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Discussion Starter #21
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.



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.



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.
 

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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.
 

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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
 

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SOHCKing03 said:
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.
 

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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
 

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SOHCKing03 said:
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.

SOHCKing03 said:
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. :)
 

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Discussion Starter #28
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.
 

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solacedagony said:
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
 

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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.
 

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" 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
 

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Discussion Starter #32
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
 

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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
 

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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).
 

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Discussion Starter #35
SOHCKing03 said:
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.
 

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SOHCKing03 said:
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.
 

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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?
 

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Discussion Starter #39
nablis said:
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.
 

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nablis said:
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.
 
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