A Basic Guide to Crossovers

[MiniVanMan]

There have been a lot of questions of late on the differences between active and passive crossovers. I'm sure with the influx of people on this board there's some confusion over what's what when crossovers are mentioned and how they're employed.

So, while this is in no way a comprehensive tutorial on crossovers, it's a beginning. Especially for those just cutting their teeth on audio.

Feel free to add, as hopefully this will grow, and feel free to correct me for anything I've said.

Okay, as promised here goes.

CROSSOVERS!!!!

First, this whole topic can be confusing in the respect that there is so much debate on this subject. Some guys swear by 24 db Linkwitz-Riley filters, while another guy can write an entire doctoral thesis for his PhD on how the 6 db Norman Bates filter is superior. So what does it all mean, 6 db, 24 db, Linkwitz-Riley, Butterworth, L-Pad, Zobel, blah, blah, blah, blah, blah.....?????????

Let's start simple. High Pass, Low Pass and Band Pass. I just need to mention this just to be sure everybody stays on the same page, and even understands the very, very, very, very, very, basics. High Pass means only frequencies above the crossover point, or sometimes referred to as the cutoff frequency, are played. For example, a 2000 hz high pass will only play frequencies above 2000 hz. Low Pass means only frequencies below the crossover point are played. For example, a 2000 hz low pass means only frequencies below 2000 hz will be played. BandPass plays frequencies between two points by utilizing both a high pass and low pass in the same filter network. So, for example you could have a midrange driver only playing 200 hz to 4000 hz.

***** Note - Before everybody and their grandmothers jump on me, let me cover myself. Because I say that a high pass will only play frequencies above a certain point, does not mean I don't understand that the frequencies below that point are still played, just cut me some slack. I'll get to that point later.

Next are slopes! Slope is the name associated with the numbers, 6 db, 12 db, 18 db, and 24 db. These are the most common, and I'm sure you've all seen them. What they actually mean, is "X" db drop off after the cutoff frequency per octave. So, to translate, let's take a 2000 hz "High Pass" I said above that a 2000 hz "High Pass" will only play frequencies above 2000 hz. That's not entirely true, as you may have gathered by my "Note" above. Okay, first you need to understand what an "Octave" is. An Octave is half, or double of a given frequency. 1000 hz to 2000 hz is an octave, as is 5000 hz to 10000 hz. So a 6 db per octave slope, cut at 2000 hz will yield a 6 db dropoff of output at 1000 hz, and 12 dbs by 500 hz, etc. Now understand that a 3 db gain is double the output, and 3 db loss is half the output. A "Low Pass" at 2000 hz using a 6 db slope would yield a 6 db drop of output by 4000 hz. Clear as mud???? Good!

Why are these numbers important? Well let's take a tweeter for example. You'll toodle around on this site and see many people talk about "Fs" or "Resonant Frequency". As a general rule that we use around here, we like to say that when picking tweeters, use double the "Fs" of the tweeter to determine lowest crossover point for a 12 db slope. This is in direct conjunction with how much power you can expect your tweeter to handle. So for example we'll take a tweeter with an Fs of 1500 hz. This tells us that we can safely use this tweeter at 3000 hz with a 12 db per octave slope. Now anybody that's been around speakers knows that it's not the high frequencies that blow speakers. It's the low ones. Just look at subwoofers. You might be able to get that 10" sub to play 20 hz, but you might start hearing some nasty clunky sounds when you try to get that sub to play 20 hz with double is rated power. The same can be said for a tweeter. So how do we get the tweeter to play closer to its Fs? Raise the slope of the crossover. A 24 db drop, when a 3 db drop is half the output is considerable. I'm not doing the math. You do it if you actually want to figure out how many halfs of halfs that is. Anyway, because 24 dbs is a lot more than 12 db, you can drive your tweeter closer to it's Fs. Same can be said of midbass drivers. You want your 7" midbass driver to play flat to 60 hz, but it's got an Fs of 40 hz. Well, you'd probably better use a 24 db slope.

Getting muddier, and muddier, isn't it??

Now on to Linkwitz-Riley, Butterworth, etc.

You'll usually see a name associated with a crossover. It's usually Linkwitz-Riley, or Butterworth, or even Bessel, or some fairly exotic ones. So, a crossover is a crossover right? WRONG!! With the case of passive crossovers, not knowing the difference can be very detrimental if you're trying to design one. Let's talk about what happens at the crossover point. We'll use our 2000 hz example again. If you have one driver playing 2000 hz, and another driver playing 2000 hz, and both are putting out the same amount of output, that would be effectively doubling the output, correct? Double the output is a 3 db gain. So, if you have one speaker playing flat to 2000 hz, and the other is playing flat to 2000 hz, then at 2000 hz, you'll have a summing of frequencies and effectively a 3 db gain in output. Maybe not so desireable, or maybe it is. Depends on the drivers and the application of the drivers. Well, this is actually the basic design behind a 12 db Butterworth crossover. It's simple and uses one crossover point to calculate the values for the components of your network. Only hitch is the 3 db gain at the crossover point. So, how do we get rid of that 3 db gain. Well, maybe by offsetting the frequencies a bit. Let's say 1850 hz for the low pass, and 2150 for the high pass (these are arbitrary numbers). Since they're not technically overlapping at this point, then the summing of the frequencies is only happening AFTER the output has started to go down. (I use calculators to determine this stuff so please don't ask me to do any math). With the right calculations, you can determine what sums will create a flat response. This is what a Linkwitz-Riley filter does. A Bessel filter will yield a 1.2 gain, and if you want to do the math, you can probably create your own filter network and apply your name to it. Then you can write a long diatribe about how great your filter that has a .82564345 db gain is, and how it will revolutionize the audio world.

"Man, are you sure this is mud, it smells more like....

Now to put this all together.

There are some common statements on this board. "Go active, the results are better". "I'm new to car audio, and am unsure about tuning an active setup". "Passives are way too hard to get right, you're better off going active." etc, etc, etc....

So, let's take a car application. You have a choice. That shiney new Diamond Hex set looks really sweet and you can get a great deal on it, or you can do it the hard way, and get an active crossover, some new shiney Seas drivers, and another amp. Well, with all this information you now have, please tell me how Diamond Audio knows how their components will be installed in your vehicle. Did they use a 12 db butterworth filter in their crossover? Doesn't that mean there's a 3 db gain at the crossover point. If I put these in kicks, on-axis, will that give me a nasty peak at the crossover point? If I put the midbass in the doors though, maybe the fact they're off-axis will be compensated for a bit by the butterworth design....

This is why we're advocates of active processing. It doesn't matter what kind of filter it is. As long as you can change it and experiment on the fly to get what sounds best. There's no math that needs to get things all muddled up.

However, if you really want to design a passive crossover go for it. Remember home audio uses the passive with great success. Their environment, however, is MUCH more controlled than ours.

I'm done... I know I mentioned L-Pads, and Zobels, and a lot of "blahs", but for now this will have to do.

Ask nicely and I'll explain those later.

[fej]

Nice post mini. I have a couple links that I have used forever that I might copy and paste over here for some instrument and tuning info.

[azngotskills]

Great write-up and thanks for taking the time to write it out :) I actually learned alot.

[fej]

Some of the stuff I use. Hope it helps.

The following post was shamelessly stolen from the forums at talkaudio.co.uk from Matt@ nearfield audio (UK stereo shop). He is also an IASCA judge.

Quote:


Understanding Frequency - What does What


A lot of you know that I am a bit of an sq fiend, I am one of the few people on here that often turns of the sub just to check it's still running...I personally like sub bass as an anchor for the low end and to add warmth to the music. To me, mid and midbass is the key.

Mid and Midbass IS critical. let's look at the frequency response of some instruments and see where all the action is. I am not going to go into the the differences of Fundemental and Harmonic frequencies, and how they interact (I can if need be), this is more of an overview of what frequencies make up what.

For those of us who listen to acoustic music, apposed to synthesised dance music, for want of a better description, I shall take some drums, bass guitar, electric guitar, and vocals.

I shall work through the frequencies rather than the instruements, as this will allow us to see where there are complimentary frequencies (different instruments produce the same sound).

50hz (usually sub bass)
this freq is where all the boom is, if you want more boom on foot drums and bass guitar, boost, to reduce, cut.

100hz( usually mid bass)
this is the hard bass sound, it gives drums that solid feel, boosting here will harden the drums/bass guitar, as well as adding warmth to guitars. A cut will reduce boom on guitar and add clarity.

200hz (either midbass/mid)
Boost to add warmth to vocals and guitar, reduce to clean up vocals

400hz (usually mid / large Horn)
Boost to bass in general, reduce to decrease cardboard sound low drums.

800hz(usually mid/horns)
Boost to add clarity and Punch to bass, this is the one that digs you in the ribs , cut to reduce tinnyness to guitars

1.5khz (mid/tweet/horns)
Boost to add clarity to bass guitar, reduce to impreve dullness of guitar

3khz (mid/tweet/horns)
Boost to increase pluck on bass guitar, attack on guitar and high drums, increases clarity of vocals.
Cut to reduce breathy sound on vocals.

5khz(mid/tweet/horns)
boost for vocal presence, low drum attack, piano attack, and guitars, reduce to distance background.

7khz(usually tweet/horn)
boost, more attack on low drums, percussion and bring life to dull vocals, also sharpen elctric guitar
Cut to reduce siblance

10khz (tweet/horn)
increase to brighten vocals/guitar and piano
cut to reduce siblance

15khz (tweet/horn)
increase to brighten vocals/guitar and piano highs


Right, looking down this list we can see that if we want a good solid bass line ( add @100hz), that's not boomy (cut @ 50hz), with good punch (add @ 800hz), with good attack ( boost at 5-7khz), most of the action is in the midbass and midrange area, with only boominess being in the sub area.

This also highlights one of the main benefits of horns( the huge range they cover).

Understanding these frequencies also allows for fine tuning things like stage height (more attack of drums gives perception of a higher stage), and adding depth, ( make background sounds more distant)

This is not really even an introduction apparantly, and I thought I was doing well when I understood this lot, but there's more, so much more.....

[fej]

Another shamelessly stolen post from killahertz at talkaudio.co.uk. This dude in the man and I will link to the forum it originates from and to anyone interested there are some incredible posts in the faq.

Quote:
A crossover consists of two or more filters designed to split the desired frequency range into parts. Each part then being assigned a dedicated drive unit (speaker). A 2-way crossover has two filters: a high pass and a low pass, and is usually used to integrate a mid-bass and a tweeter.

Each filter then has several characteristics, one of which is it's slope (or roll-off), measured in decibels per octave (dB/oct). An octave being a factor of 2 of the original frequency. Thus 1kHz has octaves at 500Hz and 2kHz.

The rate of roll-off is always a factor of 6 (for ease of circuit design and calculation). The most popular types being 6dB/oct, 12dB/oct, and 24dB/oct. Further to the numerical rate of roll-off, filters are often asigned an 'order' number. Order numbers are again a factor of 6, thus a 1st order filter equates to 6dB/oct (1*6), 2nd order 12dB/oct (2*6), and 4th order 24dB/oct (4*6).

The other important filter characteristic is the filter point (crossover point where necessary). The filter point is that chosen at the design stage and equates to the 'half-power point', or the frequency where output is -3dB (-3dB equating to a 50% reduction in power). *** This assumes the filter design uses -3dB, some designs are -6dB at the filter point ***.

For example: a 1kHz high pass filter. In it's most basic sense everything above 1kHz passes, everything below is discarded. That's not particularly accurate. The frequencies below 1kHz are not discraded, rather they are attenuated according to the rate of roll-off of the filter. Assuming 6dB/oct: The output from the filter is -3dB at 1kHz, an octave later (500Hz) the output is -9dB (ie the output is already -3dB, and the filter reduces that by a further -6dB). Another octave lower (250Hz) and the output will be -15dB. If the filter were 2nd order, 12dB/oct, the output would be -15dB within the space of an octave, ie at 500Hz. -15dB equates to over 95% reduction in power.

This should indicate the importance of high order filters, especially within high power systems, and especially with tweeters. With a 6dB/oct filter, low mid-bass frequencies will still be entering the tweeter. And even though the output is considerably reduced, if enough power is available, the percentage reduction may not be enough to stop tweeter damage.

Just for reference:

-3dB = 50% reduction, or a factor of 2
-6dB = 75% reduction, or a factor of 4
-12dB = 93.75% reduction, or a factor 16
-18dB = 98.4375% reduction, or a factor 64
-24dB = 99.609375% reduction, or a factor 256

[werewolf]

great thread!

I don't mean to confuse things, so please feel free to skip this part.

The way two drivers combine at the crossover frequency depends on the magnitude and phase at the crossver frequency, where both drivers are playing the same frequency. Strictly speaking, of course, it's the acoustic phase that matters. But let's say that the two drivers are equidistant to your ears, so we'll just focus on electrical phase for now.

If two drivers have the same amplitude, and are 0 degrees out-of-phase, the combination will be 6dB hotter in amplitude. If two drivers have the same amplitude, and are 90 degrees out-of-phase, the combination will be 3dB hotter in amplitude. If two drivers have the same amplitude, and are 180 degrees out of phase, the combination will perfectly cancel.

And now for a couple popular ones:

First order, 6dB per octave. Each driver is down 3dB at the xover frequency, and each driver experiences a 45 degree phase shift at the crossover (but in opposite directions). So the relative phase between the drivers is 90 degrees at the xover frequency. This means the drivers will have a combined response that's 3dB hotter ... and each was down 3dB at xover, meaning a combined result that's perfectly flat. This is a good thing ... but the shallow roll-off/up renders this solution almost useless (or at least not real popular anymore).

The 12dB Butterworth Alignment provides 12dB roll off/up for each driver, and each driver amplitude is down 3dB at the crossover frequency. Each filter "order" also provides 45 degrees of phase shift at the crossover frequency ... so the woofer will experience a negative 90 degree phase shift (second order), while the tweeter will experience a positive 90 degree phase shift (second order). This means that the drivers are naturally 180 degrees out-of-phase at the crossover frequency. This is kind of a bad thing, because it means a deep cancellation null at the crossover (again, we're assuming same distance from each driver to your ear). To solve it, many people wire the tweeter out-of-phase at the crossover. This puts the drivers back to a 0 degree phase relationship (inversion provides exactly 180 degree phase shift), which will result in a +3dB amplitude bump (since each one was down 3dB). Can be addressed by underlapping xover freqs a bit.

The 24dB Linkwitz-Riley was discovered by the challenge to find a crossver where each driver would be down 6dB at the crossover ... instead of the typical 3dB ... and each driver would experience a 180 degree phase shift (in opposite directions, of course) ... meaning a "perfect", 6dB summation at the xover. It was discovered that the cascade of 2 second-order butterworths satisfy all requirements, while also providing a relatively steep roll-off/up.

Well I guess that's enough for now ... not trying to hijack your thread :) Just wanted to point out that the combined response of drivers at xover is a function of each individual magnitude and phase ... creating a combination that's either +3dB bumped, flat, or deep null.

This xover stuff is a bit complex indeed :)

[MiniVanMan]

Hey Werewolf, POST AWAY. It's a far better explanation than I could have given.

A very common crossover that I've seen is the 12 db butterworth on the woofer, and an 18 db butterworth on the tweeter. I've always assumed it's because it allows you to swap phases on your tweeter to compensate for different mounting locations. Please correct me on that, and elaborate. This example should be enough to get me to wrap my brain around this stuff a little better than just, "it's a bit out of phase".

[02bluesuperroo]

Just for reference:

-3dB = 50% reduction, or a factor of 2
-6dB = 75% reduction, or a factor of 4
-12dB = 93.75% reduction, or a factor 16
-18dB = 98.4375% reduction, or a factor 64
-24dB = 99.609375% reduction, or a factor 256

Finally, this has been the last piece of the puzzle for me. I have been looking for this info everywhere. (Apparently, not hard enough) ;)

[thadman]

Werewolf, would you care to explain what exactly happens exactly with a 48dB crossover and the advantages/disadvantages?

It would be awesome if you could elaborate on the differences between bessel, butterworth, and linkwitz-riley too.

Thanks, Thadman :D

[werewolf]

holy cow ... yeah, big topic.

Hey this ain't my thread guys! Really don't want to hijak ... but for right now, here's a few interesting items:

Any linear filter is completely characterized by two things : it's MAGNITUDE response versus frequency, and it's PHASE response versus frequency. Together, these two functions define the COMPLETE FREQUENCY RESPONSE fo the filter. Oftentimes, we are more interested in the first derivative of the phase response, giving rise to a new function of frequency called the GROUP DELAY ... which will also, of course, be a function of frequency.

A "Butterworth" response is also known as Maximally Flat Magnitude. Mathematically, it is determined by setting as many derivatives as possible ... of the filter's MAGNITUDE function ... equal to zero at DC (for a low-pass filter). The resulting low-pass shape will have a MAGNITUDE response that is as FLAT as possible ... until it kinda starts to rolloff, of course :) Applicable to low-pass, high-pass and band-pass of course. This filter has a phase response that, while not as good as our next candidate, still isn't "bad".

A "Bessel" response is also known as Maximally FLat Group Delay. Mathematically, it is determined by setting as many derivatives as possible ... of the filter's GROUP DELAY function ... equal to zero at DC (for a low-pass filter). The resulting low-pass shape will have a GROUP DELAY response that is as FLAT as possible. Applicable to low-pass, high-pass and band-pass of course. The magnitude response will still look low-pass (or whatever you want), but will not roll-off as quickly or sharply as the Butterworth.

The transient time domain behavior of any filter ... including both of these, and any other linear system ... is completely determined by the COMPLETE frequency response (magnitude and phase, or group delay). The Bessel is generally considered to be a bit "better" ... less overshoot, less ringing for higher orders ... because it's phase is better behaved. But the Butterworth isn't bad, and given it's sharper roll-off, it's generally preferred for most crossover designs.

Excepting, of course, the Linkwitz-Riley. From a simple filter perspective, it's simply a cascade of two Butterworth responses. It won't be as flat as a true Butterworth of equal order, but it's strength is the way the two drivers combine at crossover, as discussed above.

More later ...

[werewolf]

Of course there's a whole other dimension to crossover design, besides time and frequency ... and that dimension is space. At the crossover frequency, two drivers will be playing the same frequency, but probably with different amplitudes and phases. And their acoustic centers will, most likely, not be coincident ... they will be separated in space, at least by a few inches. So the radiation pattern, mapped across 3-D space at the crossover frequency, will look quite different, depending on the chosen crossover. This pattern, called a "lobing" pattern, is not unlike the polar response pattern of a single driver actually. A single driver also has different "elements" playing the same frequency ... those elements being the array of points across the cone surface, but all playing in electrical phase :)

Anyway the lobing pattern of two drivers depends on the chosen crossover circuit. (An interesting "exception" being the MTM array. The fundamental merit of D'Appolito's design is that the geometric symmetry yields zero-lobing error ... defined as the first derivative of the lobe, wrt vertical space ... on axis, independent of the chosen crossover circuit. That's pretty damn clever :) ) But this whole other dimension is rarely applied to car audio, simply because the cabin itself introduces so many other variables ... mostly reflections ... that a priori design of crossovers, based on driver lobing, tends to be rather pointless.

Just wanted to mention this point in a great thread about crossovers :) And give some more underlying info about the challenges in excellent crossover design, and why it's hard to provide a simple answer to the question : what crossover should I use?

[Daishi]

Thanks very much for starting this thread. I've wanted to learn more about specific crossover types and this is a great way of getting all that info in one thread. One stop learning FTW!!!

[SOHCKing03]

What formulas do you use to determine the capacitor values?

Also, why do some places state that an inductor is needed and others say that a resistor is needed?

Lastly, are there any sites that could give a nice explanation of how to determine what frequency you should cross at?

Thanks

-Brad

[solacedagony]

http://www.passivecrossovers.com for the formulas for high/low/bandpass filters.
Inductors and resistors are used for different things. It would depend what that section of the crossover was being used for.
The drivers you're planning on using and the frequency you cross at will be derived from looking at FR graphs, waterfall plots and distortion graphs. I'm sort of new at this, but that's what I've figured out so far.

[03blueSI]

Anyone know of a place that will make crossover networks for speakers they do not carry if you can provide Klippel or LEAP readouts of the parameters of the drivers? I am looking at getting some custom crossovers until I can afford the amps to go full active on my 3 way front stage. Thanks

[SOHCKing03]

So would active require a different amplifier for each pair of speakers? i.e tweeters off one 2-channel amp, mids off one 2-channel amp, and sub off mono block?

Also, should a subwoofer ever be in the same crossover network with mids and tweeters? Should I run a 3-way with tweeters on highpass, mids on bandpass, and sub on lowpass?

That link you gave me was helpful, but it was more about passive crossovers rather than active. Is there a certain formula you use to determine active values? This site helped, but it was only for two-way... http://www.carstereo.com/help/Articles.cfm?id=12

Thanks, and sorry for all the questions.

-Brad

[demon2091tb]

Anyone know of a place that will make crossover networks for speakers they do not carry if you can provide Klippel or LEAP readouts of the parameters of the drivers? I am looking at getting some custom crossovers until I can afford the amps to go full active on my 3 way front stage. Thanks

As far as i know madisound designs them based off leap, decent quality.

[MiniVanMan]

So would active require a different amplifier for each pair of speakers? i.e tweeters off one 2-channel amp, mids off one 2-channel amp, and sub off mono block?

Also, should a subwoofer ever be in the same crossover network with mids and tweeters? Should I run a 3-way with tweeters on highpass, mids on bandpass, and sub on lowpass?

That link you gave me was helpful, but it was more about passive crossovers rather than active. Is there a certain formula you use to determine active values? This site helped, but it was only for two-way... http://www.carstereo.com/help/Articles.cfm?id=12

Thanks, and sorry for all the questions.

-Brad

Yes, going active requires seperate amps for each speaker.

There's no problem with using a subwoofer within a 3-way network.

[MiniVanMan]

I'm importing information from another thread. It's the thread that prompted me to start this one. Hopefully it will answer some questions regarding crossover points.

I'm going to use a couple of examples, and some response graphs to help you understand this.

I'll start with the Peerless Exclusive 7". Scroll to the bottom of the PDF where the response chart is.

http://www.madisound.com/pdf/peerless/830883.pdf

You'll notice the "blue", "red" and "green" response graphs. Labeled at the bottom you'll see "On Axis", "30 Degrees", "60 Degrees" respectively.

Looking at the graph you can see that the upper end response of the driver lowers dramatically the further off axis you play them at. Now if your driver side door sits 60 degrees off-axis of your listening position (which most doors fall in that area) then you can get a good idea of what the upper end response will be. In this case the graph shows about 1750 hz before it starts to collapse, and is probably useable up to about 2200 hz.

Your passenger side driver will yield a considerably higher response due to it be much closer to on-axis than the driver side, so you might start to hear some bias from the passenger side should you try to run the set up to 3500 hz.

Now let's look at the Vifa MG 4" midrange

http://www.madisound.com/pdf/vifa/mg10md09-04e.pdf

Here you'll notice that on-axis response is great. Near 15k flat, with extension up to 20k. Npdang tested this driver and mentioned that it can almost be used without a tweeter. By the response graph we can see that.

However, now let's say we're building some kick pods, and due to some reason, we can't get them completely on-axis, but rather 30 degrees off-axis is the best we can do. You'll see that the 30 degree off-axis response graph basically tells us we can use these midranges up to about 5k before any real degradation of response. Pretty nice.

Now, for low end response. For tweeters, the general rule of thumb is twice the Fs (Resonant Frequency) at 12 db. A higher slope (i.e. 18 or 24 db) can get you closer to the Fs, but we'll use 12 db for now.

Let's first look at the most common tweeter on this board... The LPG

http://www.madisound.com/pdf/lpg.pdf

The Fs of this tweeter is 1850 hz. Doubled that is 3700 hz. Now, try coupling that with a 7" driver mounted in a door 60 degrees off-axis, and you have quite a gap between 2000-3700 hz. Almost a full octave. Now to be fair, let's look at the upper end extension. The on-axis, 30 and 60 deg graphs look almost flat up to 20k. Very nice. These can be mounted in some sail panels firing horizontally across your front stage and you can get great results from them.

Next is the Seas Neo tweeter.

http://www.madisound.com/pdf/seas/h1396.pdf

Here is a tweeter with a much lower Fs. 1170 hz, using our rule, can be crossed at 2340 hz. The specs say 2500, so we're pretty close. With a 24 db slope you could get 2200 hz out of them. These would be much better to mate with a set of Exclusives mounted 60 degrees off-axis. However, their top end is nowhere near that of the LPGs. You can definitely see that these would lack the top end "sparkle" that so many people refer to when talking about the LPG's. These will be much more neutral and laid back on the top end. Not a bad thing, as a lot of music doesn't go any higher than 15k. You will also notice a huge difference between on and off-axis. A major consideration when considering how to mount them.

These are just some suggestions on how to "guess" at appropriate crossover points. The graphs give you a good idea of how to tell how a driver will perform in a given installation. These graphs in no way indicate how a driver will sound, nor how they will perform at the upper and lower limits of their capabilities.

A little more complex, but very good information.

If you want to determine the ideal LPF for a given midrange driver, observing the manufacturers (or npdangs, zaphaudios, etc) frequency response will give you loads of help. The driver must maintain a flat response 2 octaves above the crossover frequency.

For example, the Seas Excel W18E. It has a nasty breakup at 4800hz, the 2nd harmonic of this breakup is at 2400hz and the 3rd harmonic is at 1600hz. You will DEFINITELY want to avoid the 3rd harmonic of this breakup, and cross below that point (1600hz)

As a generalization (there are exceptions to this rule)

Metal cones are usually the best transducers (most pistonic, some people prefer more distortion ex. tubes) up until around 1-1.5khz (I wouldnt recommend taking a metal driver past 2khz), where they excite harmonics of nasty breakups

Paper cones breakup more easily, but the magnitude of the breakup is often quite minimal compared to metal cones and is easily tolerated. They can often be crossed much higher.

Also, you can get an idea of how a driver will perform off-axis with a little math by determining the diameter of the diaphragm.

For example, the Seas Excel W18E. It has a surface area of 126cm^2, A=Pi(r)^2. The diaphragm is ~4.99" across. The speed of sound is 13,397in/s, so divide the speed of sound by the diameter of the diaphragm and you get 2685hz. Above this point, the wavelengths the speaker will be producing will be shorter than the diaphragm and as a result, the driver will begin to beam. You will not want to use this driver off-axis, above this point

[SOHCKing03]

Thank you!

That was the kind of information I was looking for. I do not have any parts to even work with right now so I was more looking to get a plan ahead of time and tweak when I get everything in the summer.

Thanks again,

-Brad

[MiniVanMan]

Okay, now that you’ve had some time to absorb all the previous information, I’m going to step it up a little bit.

Let’s first look at the challenges we face in building any kind of speaker system.

First is level matching. It’s very difficult to find a tweeter and a woofer that have the exact same sensitivities, and will operate at the same volume given the same power.

Second is impedance variations. As you move through a speakers frequency response the impedance varies. As you get towards the upper end of response the impedance starts to rise considerably. This is demonstrated in the following graph. This a factor of inductance of the voice coil.

http://img.photobucket.com/albums/v641/glevii/zwozobel.gif

As you can see, the impedance is rising the higher you go. This causes a drop in output. A Zobel will level that out, giving you a flatter response.

http://img.photobucket.com/albums/v641/glevii/zobelcomp.gif

Third is spikes and dips that cause your response to be something other than flat.

Let’s start in order here. Level matching is done using an L-Pad. Generally, the tweeter is much more sensitive than the woofer. So the tweeter needs to be attenuated. The L-Pad circuit can be introduced into your passive crossover. It can be done 2 ways. First is fixed. If you know the amount of attenuation, you can get the appropriate resistors and build the network right into the crossover. The problem with this is if you don’t get it right, you need to completely redo it. The second way is to use a variable L-Pad. Parts Express has these and in a car audio application using passive crossovers they are a MUST in my opinion.

http://www.partsexpress.com/webpage.cfm?webpage_id=3&CATID=48&ObjectGroup_ID=196

The drawback is you need to build around the L-Pad and mount it somewhere that is accessible. However, it does allow you to adjust your tweeter to compensate for different mounting locations. These are what upstage kits, like CDT use.

Next is the Zobel network. The Zobel network compensates for the rise in impedance due to voice coil inductance. Pretty much enough said.

Third, and this is where crossovers start to get REALLY tricky, and even I’m a little fuzzy in this area. Depending on your baffle, mounting locations, varying distances of voice coils, your response will be something other than flat. If your baffle is too narrow, (as in a tower speaker) your mid drivers can experience a spike in response of around 6db starting at around 100 hz and flattening off at around 1k hz. This is called baffle step. You use baffle step compensation to, well, “compensate” for it. I’m not going to go into it a whole lot, and baffle step is just one example of how a speaker reacts to it’s environment. I will say that there is a compensation circuit that will cover just about every peak, and dip.

What does this all mean? It means that you can drive yourself CRAZY trying to build the perfect crossover for any application. There’s a point of diminishing returns when a crossover just becomes too over-engineered. It’s safe to say that a decently built crossover will contain 3 parts, the actual crossover network, the L-Pad, and the Zobel. The other networks don’t really come into play until you NEED them. Baffle step can be fairly accurately predicted, but other “notch” type filters are usually used to compensate for something unpredicted and unwanted. It’s possible to “notch” out a peak caused by a Butterworth type crossover at the crossover point, but it’s just better, if it’s a problem to pick a different alignment.

LEAP is great, as are a lot of other programs out there. LEAP allows you to build your crossover ‘to the enclosure’ for the best possible results. LEAP can only be effective when the surrounding variables of a driver are controlled. For example, the difference between a well built speaker enclosure, and a door frame. LEAP can predict and design a crossover to compensate for the way the speaker will react within a given enclosure by simply inputting the dimensions. LEAP is going to “leap” out of your computer and kick the snot out of you if you try to enter door frame parameters.

So, if you are looking to go the passive crossover route, you can pretty easily design a crossover as long as you know which speakers you’re going to be using. You add your three essential items and voila you have a working crossover. However, based on the above information that’s all you’ll get. You won’t get any kind of compensation for the way the speakers will react in the car. And believe me, they will react BADLY.

So, what do we do to compensate for these unknown and highly erratic, unpredictable peaks and dips in our frequency response? We EQ them out. An equalizer will do everything that a notch filter will do, and is effectively an “Active Notch Filter”. We couple the EQ with an Active Crossover, and you get a system that is highly adjustable and can correct for the many, less than desirable, effects your car will have on your system. Add Time Alignment and you can achieve results comparable to a cheap home audio setup (given that you spend $1000.00 on high quality speakers).

By going active, we’re essentially, trying to take the “car” out of the “car audio”. Active processing is also used in home audio and is highly desired by many audiophiles out there. However, in my opinion, the difference between a well built tower with a passive crossover and an active setup in home audio is not nearly as dramatic as an active to passive setup in car audio.

[thadman]

Unless you are restricted to an extremely stringent budget, active is much more desirable.

The DCX2496 only costs $300 (I picked mine up on ebay bnib for $215 shipped w/ warranty). It has 6 outputs (3L, 3R) and gives you access to 48dB filters and all the processing that a sane person would ever need. Passive filters become increasingly complex, difficult to design/build, and exponentially expensive once higher order types are needed. You also cannot experiment with passive crossovers without having to ditch your previous parts...and you will have to redesign/buy new components if you ever decide to go with a new system. Passive crossovers also waste the your amplifiers power as heat, putting excess strain/load on your electronics.

[demon2091tb]

Going to be buying a 2496 soon here, either before christmas or soon after. Will be the start of my new home setup.

[SOHCKing03]

I searched the 2496 and it looks like a really nice product, especially for under $250...

But if I am understanding all this crossover stuff right, then to go active the 2496 would require a seperate amp for each pair of speakers?

I am considering using the DCX2496 but I am getting a PG 400.1 for my sub and PG 100.4 for my HDS tweeters and Peerless Exclusives mids. Would that work or would I need a seperate amp for each?

-Brad

[solacedagony]

I searched the 2496 and it looks like a really nice product, especially for under $250...

But if I am understanding all this crossover stuff right, then to go active the 2496 would require a seperate amp for each pair of speakers?

I am considering using the DCX2496 but I am getting a PG 400.1 for my sub and PG 100.4 for my HDS tweeters and Peerless Exclusives mids. Would that work or would I need a seperate amp for each?

-Brad

You need a channel of amplification for each driver (or two channels for each way). If you have 4 drivers, you need 4 channels of amplification.

[SOHCKing03]

Alright, so I would need to have the speaker wires going from the crossover to the amp and then from the amp to the speakers?

Also, are there any models that are not as expensive as the PPI one always mentioned and the DCX2496? I want one that will be sufficient for a beginners set-up. I do not need a very expensive one because I am not looking to control very expensive speakers.

-Brad

[solacedagony]

Alright, so I would need to have the speaker wires going from the crossover to the amp and then from the amp to the speakers?
Active crossovers work BEFORE the amps, while the passives work AFTER the amps. You're all signal (RCAs) before the amps and the speaker wire goes straight to the driver.

Also, are there any models that are not as expensive as the PPI one always mentioned and the DCX2496? I want one that will be sufficient for a beginners set-up. I do not need a very expensive one because I am not looking to control very expensive speakers.
That's sort of unrelated. As you pay more, you generally get more flexibility and options out of your unit, not higher quality sound. It shouldn't make any change in your sound if you apply the same exact settings on one unit as opposed to that other. Of course, that's in an ideal world. :)

[MiniVanMan]

What the PPI, 2496, Alpine H701, and others offer you is much more than just a crossover. You get features like time alignment and EQ, etc. You can pick up a basic 3 way active crossover like the Coustic XM-6, on ebay for under $50.00. It'll be just fine to start with. Then as you get more experience, you can move to other features, and your setup can grow.

What you're looking for is a crossover that has the following features.

High Pass - variable up to about 4000+ hz
Band Pass - variable of about 50 hz high pass - 5000 hz lowpass
Low Pass - can be anything above 80 hz

These are very flexible numbers. If you find a unit you think might work, post it here, and we'll let you know.

[SOHCKing03]

That's sort of unrelated. As you pay more, you generally get more flexibility and options out of your unit, not higher quality sound. It shouldn't make any change in your sound if you apply the same exact settings on one unit as opposed to that other. Of course, that's in an ideal world. :)

I must not have worded things correctly. I understood that you'll get about the same sound quality, but I didn't know if all those features were even necessary for a beginning set-up.

I got my PE catalog a couple days ago and I had found a 2-way stereo/3-way mono crossover with subwoofer out. It has 24dB slope LR filters, balanced inputs and outputs, and seperately adjustable subwoofer output. It is only $90. Would this be sufficient?

They also have a 3-way stereo/4-way mono. Would it be better to have the 3-way mono or 3-way stereo? The price is only $130 too so it isn't that expensive. I do believe however that this one has time alignment unlike the other.

Any input on these would be great.

Oh yeah they are Super-X Pro CX2310 and Super-X Pro CX3400. Model #'s are #248-664 and #248-668

Thanks

-Brad

[solacedagony]

For only 40$ extra, I would get the 3-way stereo one. If you decide you want to go 3-way front stage you have that option. More specifically, I would want it for the time alignment. Does that unit also allow for level matching?

Mini: Sorry if this thread is getting off of its main purpose. I'll stop replying if you want to cut down on junk in the thread.

[SOHCKing03]

" The CX3400 is an active frequency crossover enabling 2 or 3-way stereo or even 4-way mono operation. Each band features two 24-dB Linkwitz-Riley filters, as well as individual IGC limiters, while the integrated delay enables flexible time alignment. Polarity switches for each output allow quick and easy runtime compensation for various driver and horn types."

So I am guessing that it doesn't do level matching unless that's what the "runtime compensation" is.

I too am sorry for jacking this thread, I can delete these posts and take them to PM's if you want the junk out.

-Brad

[MiniVanMan]

As long as it stays within the realm of crossovers, then it'll be okay. However, I did start a new thread concerning the DCX2496 in the general forum. There are definitely some things people need to know about the pro-audio units before they purchase them. For one, you need to supply them with 110v AC, which means you need a power inverter. I'm pretty sure it'll get hashed out in the new thread.

http://www.diymobileaudio.com/forum/showthread.php?t=7378

[SOHCKing03]

So between DCX2496 and the CX3400, would you go with the CX3400?

-Less money
-Runs off DC (I haven't seen otherwise)
-No known issues (heating, noise, etc)
-Can perform the tasks I need

I am leaning more towards the 3400 so I'll probably get that and if I need to upgrade then I will move to the 2496 or even the PPI 730 if I've got the money for it.

-Brad

[solacedagony]

I personally think the DCX is worth the extra money for having all the EQ and bells and whistles on top of the crossover. Less to worry about. Although, like MiniVan said, you have to use a power converter on it or get the unit modded for 12v. I remember seeing somewhere that some company would do it for you (don't remember who or at what cost, however).

[MiniVanMan]

So between DCX2496 and the CX3400, would you go with the CX3400?

-Less money
-Runs off DC (I haven't seen otherwise)
-No known issues (heating, noise, etc)
-Can perform the tasks I need

I am leaning more towards the 3400 so I'll probably get that and if I need to upgrade then I will move to the 2496 or even the PPI 730 if I've got the money for it.

-Brad

All those pro-audio units run off of 115 VAC.

[-=Jeff=-]

Thanks for the Thread MiniVanMan!!!

this helps.. now I just need to decide what to do.. LOL

[shinjohn]

So between DCX2496 and the CX3400, would you go with the CX3400?

-Less money
-Runs off DC (I haven't seen otherwise)
-No known issues (heating, noise, etc)
-Can perform the tasks I need

I am leaning more towards the 3400 so I'll probably get that and if I need to upgrade then I will move to the 2496 or even the PPI 730 if I've got the money for it.

-Brad
Since I have a 3400, (which I am about to upgrade to a 2496) a couple of notes:
1) It runs of AC, as mentioned
2) Set crossover slope (24dB/oct) whereas the the 2496 is configurable
3) HP and LP are not independentally controllable. One knob sets the crossover frequency, and therefore you cannot controll the amount of overlap or underlap.

Just FYI.

[nablis]

Ok so some crossover types boost the db at the crossover frequency. Anyone know what type of crossovers are used in the 8053? or does it only apply to analog or digital?

[MiniVanMan]

Ok so some crossover types boost the db at the crossover frequency. Anyone know what type of crossovers are used in the 8053? or does it only apply to analog or digital?

Actually, it doesn't really matter, as each slope is individually adjustable. It would only matter if you set the crossover point as one selection for say the high pass of the tweeter and the low pass of the mid. I don't really know how to explain that better, so I hope it clears it up.

This also another huge advantage of active over passive. You generally don't need to worry about whether it is Butterworth, LR, etc. Because, with active you're selecting your own underlap or overlap depending on what sounds good. You're essetially creating your own crossover variant.

[thechris]

Ok so some crossover types boost the db at the crossover frequency. Anyone know what type of crossovers are used in the 8053? or does it only apply to analog or digital?

the adjustable-Q "peaking" type filters are typically found in subsonic filters and some class D amps, advertised as a bass-boost+filter in one deal.

because digital filters often are designed around analog filters, the effect is not limited to just analog designs.

it is assumed that unless specifically stated, the filter will not have peaking.

[saMxp]

Actually, it doesn't really matter, as each slope is individually adjustable. It would only matter if you set the crossover point as one selection for say the high pass of the tweeter and the low pass of the mid. I don't really know how to explain that better, so I hope it clears it up.

This also another huge advantage of active over passive. You generally don't need to worry about whether it is Butterworth, LR, etc. Because, with active you're selecting your own underlap or overlap depending on what sounds good. You're essetially creating your own crossover variant.

Is there a phase shift with active digital crossovers? There is a note in the Pioneer P880PRS manual that talks about compensating with phase for 12dB slopes. I thought this phase shift was only present with analog components?

[werewolf]

Is there a phase shift with active digital crossovers? There is a note in the Pioneer P880PRS manual that talks about compensating with phase for 12dB slopes. I thought this phase shift was only present with analog components?

common misconception :(

YES. Digital crossovers also induce a phase shift, quite similar to their analog counterparts ... 45 degrees at the xover frequency (per-order), asymptotically approaching 90 degrees at frequency extremes (per-order). Anyone who tells you different, is either ignorant ... or selling something ;)

The only exception to this rule in digital xovers is a class of digital filters called FIR (for Finite Impulse Response), which have the ability to realize perfectly linear phase. But these filters are quite rare ... in both home and car audio processors.

[saMxp]

Thanks for clearing that up!

[VegasMike702]

This is an awesome thread . Very helpful

[///MJay]

There is a ton of great info in this thread. What if anything happens when you cascade crossovers? Example, you use the crossover in the head unit, then the crossover in the amp in the same capacity as the one in the head unit. If you are using hpf on the deck and hpf on the amp. Does this change the slope or the crossover point? I am mostly just curious I don't plan on using this set up.

Jason

[bobditts]

excellent thread mini! I was wondering if some might want to contribute as to good sites to purchase passive crossover components. After designing the proper crossover, you need to get the parts from somewhere right? haha. where does everyone get theirs? I know www.partsexpress.com (http://www.partsexpress.com) has some parts. any others?

[seagrasser]

I usually look through the sale sections of

http://www.madisound.com/index.html

http://www.solen.ca/

http://www.meniscusaudio.com/Specials/

http://www.speakercity.com/Merchant2/merchant.mvc?

http://www.zalytron.com/

Hope that helps

Jason

[abel]

i got a question can some one help me ,
i have a set of component i follow back the original passive crossover to build another one using a better component , currently my original Coil for tweeter is running 0.2mh but i cant get the same value and i bought a 0.22mh Goertz Copper coil

my tweeter is running on 3rd order 4.0uf cap > 0.2mh coil > 10uf cap even my cap cant find exact value i only can get 3.9uf Mundorf cap if like this will have big different plus my coil is 0.22mh pls help

[MiniVanMan]

You'll have some flexibility in the parallel coil in a high pass circuit, so I don't see why .22 mh would be a problem.

Also, the difference between a 4.0, and 3.9 uF capacitor will be very little if anything at all. Those Mundorf Supreme caps have a tolerance of 2% so that's anywhere between 3.92 and 4.08. Excellent tolerances, but shows that that small of a difference won't make that much of an audible difference. Especially in a car.

[abel]

You'll have some flexibility in the parallel coil in a high pass circuit, so I don't see why .22 mh would be a problem.

Also, the difference between a 4.0, and 3.9 uF capacitor will be very little if anything at all. Those Mundorf Supreme caps have a tolerance of 2% so that's anywhere between 3.92 and 4.08. Excellent tolerances, but shows that that small of a difference won't make that much of an audible difference. Especially in a car.

thanks man now i waiting my things arrived just order from madisound really thanks

[MiniVanMan]

Bump for this one as well. It's fallen to the wayside, and is hardly being read anymore.

[borgs]

Minivan,
Do you think is necessary to build a zobel network for the mids?

[MiniVanMan]

Minivan,
Do you think is necessary to build a zobel network for the mids?

I don't generally do Zobels in my networks. Zobels allow you to increase the top end acoustic response of a driver. However, in the case of a 7" mid, using it above 2khz, starts to degrade the off-axis response of the mid, and therefore the overall polar response will suffer for the system as a whole.

So, I like to use the natural roll off of a driver to achieve my acoustical response at a point where I'll get the best polar response, and off-axis response possible.

[cacin]

There is a ton of great info in this thread. What if anything happens when you cascade crossovers? Example, you use the crossover in the head unit, then the crossover in the amp in the same capacity as the one in the head unit. If you are using hpf on the deck and hpf on the amp. Does this change the slope or the crossover point? I am mostly just curious I don't plan on using this set up.

Jason

Based on what I read from the Car Stereo Cookbook, you'll have change in slope. The slope will be steep than the one set in the HU and amp. I don't remember how to calculate it.
I'm not sure about the crossover point though.

[exonn]

hi, very helpful thread....
but now i have some quastions (am realy sorry for my english).
i have morel mt 23 tweeters and want ot build and x-over for them. So, Fs is 950 Hz, it meens it can be saftly crossed at 1900 hz with 2nd order hi pass. Am i right? So, i have formulas to calculate the values for cap and inductord, but cant finde anywer data sheet for my tweeters with impendance at cross frequency. morel provides manual only with "sensitivity Mag" in 0, 30 and 45 dgree. Do anyone knows whats is impendance value for mt 23 at 1900 hz? or maybe anyone knows where to finde info or a link with info how to mesure impendance?

[MiniVanMan]

hi, very helpful thread....
but now i have some quastions (am realy sorry for my english).
i have morel mt 23 tweeters and want ot build and x-over for them. So, Fs is 950 Hz, it meens it can be saftly crossed at 1900 hz with 2nd order hi pass. Am i right? So, i have formulas to calculate the values for cap and inductord, but cant finde anywer data sheet for my tweeters with impendance at cross frequency. morel provides manual only with "sensitivity Mag" in 0, 30 and 45 dgree. Do anyone knows whats is impendance value for mt 23 at 1900 hz? or maybe anyone knows where to finde info or a link with info how to mesure impendance?

The only way to know what your impedance measurement for a driver is, is to measure it yourself. The manufacturer can give a good idea, but it's always better to do it your self.

As for crossing at double the Fs, that's a loose rule. Even if the driver can handle that low of a crossover point, doesn't mean you should. Other factors like distortion and power handling come into play as well.

The Morel MT23 will probably be fine in the 2k range, but there are tweeters, and I think Morel has them as well, that have an Fs of around 500. I'd be VERY cautious about crossing any tweeter over at 1khz. In fact, I probably wouldn't even do it.

[exonn]

on other forums, i get sugestions to go 1st order and cross my tweets on 5600 hz. And all i need is just one cap of 4.7uf (for one tweeter). Do you think this is good idea?

This is gona be 2 way system. mid bass is from focal 165 access system.

[lyttleviet]

very informative guys...

[MiniVanMan]

on other forums, i get sugestions to go 1st order and cross my tweets on 5600 hz. And all i need is just one cap of 4.7uf (for one tweeter). Do you think this is good idea?

This is gona be 2 way system. mid bass is from focal 165 access system.

There aren't many tweeters I would suggest using a 6 db network on unless you're crossing over VERY high. And then, for a 2-way, you're going to have serious problems.

5.6khz is too low. That can be dangerous for a tweeter is you push it hard.

Because Dynaudio does it, doesn't mean that everybody can do it. The Dynaudio tweeter is a very good tweeter.

[exonn]

MiniVanMan,
Thanks for your ansvers...

[hngu7721]

excellent and informative write-up. will save for reference!

[txbonds]

Thanks for posting this thread. Tagging for easy reference.

[Jhemi80]

Bump for an awesome thread!

[stoeszilla]

There aren't many tweeters I would suggest using a 6 db network on unless you're crossing over VERY high. And then, for a 2-way, you're going to have serious problems.

5.6khz is too low. That can be dangerous for a tweeter is you push it hard.

Because Dynaudio does it, doesn't mean that everybody can do it. The Dynaudio tweeter is a very good tweeter.

What's your opinion of the TBI Sound tweeter that comes with a "6.8 UF FILM CAPACITOR (3.5KHZ @4 ohms - 6db/oct)" (from the website: http://www.tbisound.com/dsp_products_auto_tweet1.asp)?

If you consider 5.6 khz too low, then 3.5 khz seems extremely dangerous, no? Would that not allow alot of "low" (i.e., tweeter-destroying frequencies) in? Or is this a robust tweeter as well...seems sketchy...

But it would be a nice and simple tweeter to add to a driver with natural roll-off (mach5 mli-6 or the seas model???). Is there something I'm missing?

Thanks again for a very informative thread...but it leaves me with more questions. Such as lobing (something Zaph talks about when selecting drivers and optimum crossover points) and how driver spacing plays a part in all of this...

chris

[MiniVanMan]

I have gone into lobing and combing in many other threads to some detail. You'll have to search around. I didn't compile them, and I have no intention of doing another thread like this one. Sorry.

I didn't say you couldn't run a tweeter with a 6db at a lowish crossover point, I just said, it's not a very good idea.

The 6 db crossover is excellent for producing the best power response at the crossover point of any other filter order. However, with that comes the fact that your driver had better be able to handle that power.

I haven't had the luxury of playing with the TBI tweeter, but I'm pretty sure, they don't want you running 100 watts to that tweeter with only a 6 db filter at 3.5khz. Also, a 6.8 uF capacitor yields a crossover point 5850 hz "electrical", NOT 3.5khz. Acoustically, I don't know. However, I don't know where they came up with 3.5 khz. Even "acoustically" that would be quite a stretch. Most likely, they're compensating for the rising response of the tweeter from Fs, and saying that the 6.8 uF cap "flattens" out the response from 3.5 - 6khz. Still acoustically, the slope would be much higher below 3.5 khz.

They played with some some numbers, which is fine. In the end though, they know better than to give people actual tweeter with inline caps for a 3.5khz, 6 db slope. That's just asking for trouble.

[handy]

I don't generally do Zobels in my networks. Zobels allow you to increase the top end acoustic response of a driver. However, in the case of a 7" mid, using it above 2khz, starts to degrade the off-axis response of the mid, and therefore the overall polar response will suffer for the system as a whole.

So, I like to use the natural roll off of a driver to achieve my acoustical response at a point where I'll get the best polar response, and off-axis response possible.

i had my experiment on zobel network. i agree that zobel is lowering the impedance of speaker.

http://i227.photobucket.com/albums/dd222/handyarianto/imp-1.jpg

and this one with zobel

http://i227.photobucket.com/albums/dd222/handyarianto/6868-1.jpg

the green and black is just different value of C.

and this is the response of use zobel (black) and no use (green)
http://i227.photobucket.com/albums/dd222/handyarianto/splzobel.jpg

use of zobel beside lowering the impedance to Re its also decrease the top end acoustic response of a driver.

[Andy Wehmeyer]

Careful, the Zobel doesn't change the impedance of the speaker, it changes the impedance of the amplifier. If the Zobel is calculated precisely, the response of the speaker shuldn't change, but the impedance the amplifier "sees" will change. The Zobel makes it easier to calculate the required crossover components and that's its main purpose. Simply designing the filter to use the rising impedanace as one part of the passive network will result in a simpler circuit that costs less.

The important response is the measured acoustic response from the combination of drivers connected to the crossover and not the electrical network itself.

[MiniVanMan]

Careful, the Zobel doesn't change the impedance of the speaker, it changes the impedance of the amplifier. If the Zobel is calculated precisely, the response of the speaker shuldn't change, but the impedance the amplifier "sees" will change. The Zobel makes it easier to calculate the required crossover components and that's its main purpose. Simply designing the filter to use the rising impedanace as one part of the passive network will result in a simpler circuit that costs less.

The important response is the measured acoustic response from the combination of drivers connected to the crossover and not the electrical network itself.

Exactly!

If you are resistant to doing complicated calculations yourself, and decide to use a modeling program for your filters, then the Zobel is almost an antiquated network.

When I say "modeling program", I'm not talking about a simple crossover designer where you input a frequency and an impedance then it shoots out some values for capacitors and inductors. I'm talking your Speaker Workshops, SoundEasy, LEAP, etc.

All those programs use the impedance curve, coupled with driver response, to predict the response shape after applying various capacitor and inductor values into your circuit. At that point, it becomes pointless to add a Zobel, as the program will be taking into account the variations in impedance anyway.

Another benefit to going without a Zobel is that it's an easier load on the amplifier. The higher impedance of your mid (in a 2-way generally), will increase the impedance of the system overall at the crossover point, making your amplifier sweat a little less.

However, if you really want extended response from a driver, adding a Zobel is a way to do it. I haven't played with an extended range driver and a Zobel yet, but I would venture to guess that that type of driver could benefit. I could also be totally mistaken.

[handy]

Careful, the Zobel doesn't change the impedance of the speaker, it changes the impedance of the amplifier. If the Zobel is calculated precisely, the response of the speaker shuldn't change, but the impedance the amplifier "sees" will change. The Zobel makes it easier to calculate the required crossover components and that's its main purpose. Simply designing the filter to use the rising impedanace as one part of the passive network will result in a simpler circuit that costs less.

The important response is the measured acoustic response from the combination of drivers connected to the crossover and not the electrical network itself.

Exactly!

If you are resistant to doing complicated calculations yourself, and decide to use a modeling program for your filters, then the Zobel is almost an antiquated network.

When I say "modeling program", I'm not talking about a simple crossover designer where you input a frequency and an impedance then it shoots out some values for capacitors and inductors. I'm talking your Speaker Workshops, SoundEasy, LEAP, etc.

All those programs use the impedance curve, coupled with driver response, to predict the response shape after applying various capacitor and inductor values into your circuit. At that point, it becomes pointless to add a Zobel, as the program will be taking into account the variations in impedance anyway.

Another benefit to going without a Zobel is that it's an easier load on the amplifier. The higher impedance of your mid (in a 2-way generally), will increase the impedance of the system overall at the crossover point, making your amplifier sweat a little less.

However, if you really want extended response from a driver, adding a Zobel is a way to do it. I haven't played with an extended range driver and a Zobel yet, but I would venture to guess that that type of driver could benefit. I could also be totally mistaken.

thanks Andi and mini

but if don't have any simulation software maybe zobel can give an instant solution, just count the le and re and u are done.

the same driver and the target response 12 db at 2700 hz
http://i227.photobucket.com/albums/dd222/handyarianto/spltarget.jpg

just 12db butterworth passive xo without zobel

http://i227.photobucket.com/albums/dd222/handyarianto/spltargetxo.jpg

with zobel

http://i227.photobucket.com/albums/dd222/handyarianto/spltargetxopas.jpg

zobel, with and without passive xo the higher frequency is always decrease. so i don't think zobel can extend the response.

[stoeszilla]

Thanks Mini (and others), I'll have to go over the other thread you posted for crossovers (as well as search for lobing, etc.). I just want to say that these threads help to really dispel some of the myths of crossovers and have helped me to understand that simple passive crossovers are anything but "simple"! Thanks again,
Chris