want to run a DIY set. how to crossover. (passive)

1541 Views 24 Replies 8 Participants Last post by Billy Mays, May 28, 2009

Billy Mays

Discussion Starter · May 21, 2009

i'd like to do something from morel or SEAS but in my mind i'm stuck on how to go about crossovers. talking passive 2way. i can use the amp to highpass at 80 but how would i seperate the tweeter off of that? or maybe there's a better way and i can allpass the amp?

1 - 20 of 25 Posts

dubbreak

· #2 · May 21, 2009

So you only have two channels of amplification and don't have the budget to go active?

I went passive with some cheap components that I was able to find some decent FR graphs for (with Seas or Morel decent specs, freq response and impedance graphs can be found pretty easily, the peerless drivers I chose it was a bit tougher). I used spl trace to trace the graphs and then used some free software (PCD - passive crossover designer) by Jeff Bagby (can be found on techtalk.parts-express.com quite frequently) and worked up the approx acoustic rolloff I was looking for (4th order LR). It's a little harder to get good summation by just designing when working with car audio because of all the variables (lots of reflections, positioning may not be completely known before hand, so you don't know acoustic offsets, acoustic offsets may be entirely ridiculous etc).

If you had measurement equipment, you could get the drivers into the vehicle, measure them then design using those measurements.. that would yield better results, but more cost in measurement equipment (which could be used towards going active).

Also, if you know the drivers or at least one and are flexible on the other you could use someone else's design and just remove the baffle step compensation from the crossover (if there is any). The are plenty of already designed 2-way speakers using seas and morel drivers.

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capnxtreme

· #3 · May 21, 2009

You probably don't wanna hear it, but the answer always comes back to the fact that the easiest solution is just to go active, if you're set on DIY drivers.

Billy Mays

Discussion Starter · #4 · May 21, 2009

dubbreak said:
So you only have two channels of amplification and don't have the budget to go active?

I went passive with some cheap components that I was able to find some decent FR graphs for (with Seas or Morel decent specs, freq response and impedance graphs can be found pretty easily, the peerless drivers I chose it was a bit tougher). I used spl trace to trace the graphs and then used some free software (PCD - passive crossover designer) by Jeff Bagby (can be found on techtalk.parts-express.com quite frequently) and worked up the approx acoustic rolloff I was looking for (4th order LR). It's a little harder to get good summation by just designing when working with car audio because of all the variables (lots of reflections, positioning may not be completely known before hand, so you don't know acoustic offsets, acoustic offsets may be entirely ridiculous etc).

If you had measurement equipment, you could get the drivers into the vehicle, measure them then design using those measurements.. that would yield better results, but more cost in measurement equipment (which could be used towards going active).

Also, if you know the drivers or at least one and are flexible on the other you could use someone else's design and just remove the baffle step compensation from the crossover (if there is any). The are plenty of already designed 2-way speakers using seas and morel drivers.

capnxtreme said:
You probably don't wanna hear it, but the answer always comes back to the fact that the easiest solution is just to go active, if you're set on DIY drivers.

i don't want to go active because A) i know very little about how to make active crossovers and how a bi-amp setup is going to work out with my gear selection and B) i'm running out of places to put stuff. i have a EG civic coupe. it's a pretty tight ride as is. my box takes the trunk, my amps are on the back seat and i'm using stock speaker locations. the plan is to put small format tweets in the A pillar and continue to use the stock door woofer location. i'm hoping that moving the tweets higher will bring my stage up as right now it feels like some people are singing at my knees or steering wheel height.

i'm sure this is going to be considered a bad idea but my idea now is to replace the components i have now in pieces, tweets first then the midbass using the cross over from the old set. i know this isn't ideal but i really can't stand how sibilant my car is now. i run my treble at -4 out of 8 just to cut back the lisps and washy sounds.

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benny

· #5 · May 21, 2009

Billy, here ya go: Passive Crossovers, Capacitor and Coil Calculator

Might work out for you, might not. But you'll learn things, and you'll realize why active isnt such a bad idea.

Billy Mays

Discussion Starter · #6 · May 21, 2009 (Edited)

benny said:
Billy, here ya go: Passive Crossovers, Capacitor and Coil Calculator

Might work out for you, might not. But you'll learn things, and you'll realize why active isnt such a bad idea.

thanks for the link, i'm using the calculator now and since it gives you the values for every specific part it makes me feel like building these is as simple as sticking the parts on the board. i've looked at other schematics and they seemed more complicated talking about input stages and opamps and a whole slew of parts. if this is as easy as a couple of caps and a coil or two soldered to a board this is within reach i think.

Billy Mays

Discussion Starter · #7 · May 21, 2009

also, if someone could help me with how to read speaker graphs as far as how to use them to determine crossover frequency that'd be awesome. even if it's a link. sorry to bug but there's so much reading to do!

dubbreak

· #8 · May 21, 2009

Billy Mays said:
thanks for the link, i'm using the calculator now and since it gives you the values for every specific part it makes me feel like building these is as simple as sticking the parts on the board. i've looked at other schematics and they seemed more complicated talking about input stages and opamps and a whole slew of parts. if this is as easy as a couple of caps and a coil or two soldered to a board this is within reach i think.

The problem is those calculators assume a constant impedance and give you a straight electrical network of the order you want. On a woofer a 2nd order electrical filter could result in a 4th order rolloff (depending on the values and the impedance curve of the driver), it could be a lot more shallow, could even be steeper and the corner frequency may not be what you calculated at all (i.e. it won't start rolling off at the frequency you selected in the calculator). A second order filter on a tweeter may only result in a 3rd order acoustic rolloff, and again the corner frequency may not be what you thought it would... End result is a set of components that won't sum anywhere close to flat (either a big hole or hump in the region where the two drivers cross).

Drivers are reactive to the filter network, and you really can't design a crossover w/o taking the particular driver into consideration. Yes you can use zobels and other tricks to try and get textbook calculated crossovers to work better, but you end up using a lot more components and still won't get anywhere close to modeling it. Also by modeling you can properly notch out breakup on the woofer (if necessary).

Personally I would use PCD or something similar to get both drivers to get a 4th order LR acoustic rolloff at my chosen crossover freq (ignoring stuff like trying to get the phase perfectly aligned). If you don't want to try it yourself you can always ask (lots of people over at techtalk find modeling drivers fun, and since the aim isn't perfection it should be pretty quick to work up).

Have you nailed down what drivers you plan on using?

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falkenbd

· #9 · May 21, 2009

http://www.diymobileaudio.com/forum/438225-post4.html

Everything you need, everyone can put spoons down now.

Reading the stuff linked in that post, will be more useful than taking tidbits from people in this thread.

Understand the whole picture.

dubbreak

· #10 · May 21, 2009

Why not to use pre-built crossovers. Generic pre-built crossovers are basically the same thing as using a crossover calculator.

Not properly designing a crossover for good drivers is a waste. Again, if you know what drivers you want to use (or at least one) then someone else may have already designed a x-over. I can help find one and remove baffle step from the filter.. but first you have to nail down at least one of the drivers and a budget.

MiniVanMan

· #11 · May 21, 2009

Billy Mays said:
also, if someone could help me with how to read speaker graphs as far as how to use them to determine crossover frequency that'd be awesome. even if it's a link. sorry to bug but there's so much reading to do!

I'm gonna be blunt. By the time you understand everything you'd need to know to implement a half way decent passive solution, you'll understand how to do active.

Due to the phase relationships in a car, and complex problems like extreme lobes, passives are incredibly difficult to optimize for auto applications. So, unless you're willing to invest in some test equipment that won't be cheap, I'd suggest learning about crossovers and just implement an active solution.

However, here's a step by step tutorial on how to design a passive crossover for a home application. Gets considerably more complicated when you try to implement in a car, and a home designed crossover may not work well in a car anyway. It is a good start though.

http://www.rjbaudio.com/Audiofiles/FRDtools.html

Billy Mays

Discussion Starter · #12 · May 21, 2009

falkenbd said:
http://www.diymobileaudio.com/forum/438225-post4.html

Everything you need, everyone can put spoons down now.

Reading the stuff linked in that post, will be more useful than taking tidbits from people in this thread.

Understand the whole picture.

thanks for the link!

dubbreak said:
Why not to use pre-built crossovers. Generic pre-built crossovers are basically the same thing as using a crossover calculator.

Not properly designing a crossover for good drivers is a waste. Again, if you know what drivers you want to use (or at least one) then someone else may have already designed a x-over. I can help find one and remove baffle step from the filter.. but first you have to nail down at least one of the drivers and a budget.

i don't have a specific single driver picked out. that's probably a good thing though. given an $800 or so budget for woofs and tweets what's a common application?

dubbreak

· #13 · May 21, 2009

Billy Mays said:
i don't have a specific single driver picked out. that's probably a good thing though. given an $800 or so budget for woofs and tweets what's a common application?

That's enough of a budget to get some good tweets, mids and some more amplification to go active.

Some decent tweets that are affordable are the seas neos. The vifa xts are a good deal too. Since you are planning on doing sails you'll need small tweets w/o much depth (generally this will mean you have to cross higher than a bigger tweeter).

SEAS Prestige 27TAFNC/G (H1397) 1" Aluminum Dome Tweeter from Madisound
SEAS Prestige 27TFFNC/G (H1396) 1" Textile Dome Tweeter from Madisound
Vifa XT25SC90-04 Ring Radiator Tweeter from Madisound

If you want to step up to some pricier ones Scanspeak makes some awesome tweeters with a small faceplate. I'm sure there are some morel options too. Personally I'd say $100/tweeter is plenty budget. Heck, you can get some pretty awesome tweeters for $100/pair (those seas examples I linked to were only $30/each).

For mids the seas p18 or l18 are good deals and <$100/each. There are morels in that price range too. The peerless hds line is nice too (and in that price range).

That would set you up with some pretty high end drivers for <$400 and would leave $400 for more amps and some form of active x-over.

Another point against passive I just remembered - cost. Inductors and decent caps aren't cheap and are inflexible. With active you can play with x-over points if you get it wrong the first time. Passive means buying more components.

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Billy Mays

Discussion Starter · #14 · May 21, 2009

dubbreak said:
That's enough of a budget to get some good tweets, mids and some more amplification to go active.

Some decent tweets that are affordable are the seas neos. The vifa xts are a good deal too. Since you are planning on doing sails you'll need small tweets w/o much depth (generally this will mean you have to cross higher than a bigger tweeter).

SEAS Prestige 27TAFNC/G (H1397) 1" Aluminum Dome Tweeter from Madisound
SEAS Prestige 27TFFNC/G (H1396) 1" Textile Dome Tweeter from Madisound
Vifa XT25SC90-04 Ring Radiator Tweeter from Madisound

If you want to step up to some pricier ones Scanspeak makes some awesome tweeters with a small faceplate. I'm sure there are some morel options too. Personally I'd say $100/tweeter is plenty budget. Heck, you can get some pretty awesome tweeters for $100/pair (those seas examples I linked to were only $30/each).

For mids the seas p18 or l18 are good deals and <$100/each. There are morels in that price range too. The peerless hds line is nice too (and in that price range).

That would set you up with some pretty high end drivers for <$400 and would leave $400 for more amps and some form of active x-over.

Another point against passive I just remembered - cost. Inductors and decent caps aren't cheap and are inflexible. With active you can play with x-over points if you get it wrong the first time. Passive means buying more components.

awesome info. i gave a genorous budget because i've seen woofers from scanspeak and morel for $300+ per.

if i could get setup for under $400 that'd be awesome. especially since i could upgrade a la carte after that.

what's the amplification concern with actives? you keep saying i need more power to run active.

dubbreak

· #15 · May 21, 2009

Billy Mays said:
what's the amplification concern with actives? you keep saying i need more power to run active.

More channels. You need one channel per driver. So an amp channel (or bridged pair of channels) per mid and a channel per tweeter.

Not sure what head you're running, so don't know if you can go active straight off the deck, or will need a crossover. Another option is zapco amps with onboard processing. Just hookup your computer via usb and you can use the amp's onboard dsp to do the crossovers and time alignment etc. If you already have amp channels you can always get a simple 3-way active x-over on the cheap (won't have time alignment though).

What do you have currently for gear?

Billy Mays

Discussion Starter · #16 · May 21, 2009

dubbreak said:
What do you have currently for gear?

Kenwood Excelon KDC-X591 CD receiver with MP3/WMA/AAC playback at Crutchfield.com

2 of these

Rockford Fosgate Punch P500-2 2-channel car amplifier 125 watts RMS x 2 at Crutchfield.com

5 1/4 pioneer components

2 of these

JL Audio 12W6v2-D4 W6v2 Series 12" subwoofer with dual 4-ohm voice coils at Crutchfield.com

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Billy Mays

Discussion Starter · #17 · May 21, 2009 (Edited)

if i went with the zapco REF amps i could keep my HU correct? if so that might be the most economical way. i'd just have to make sure all my drivers were 4 ohm so i'd have enough power. i was just reading another thread where a guy was having trouble getting good mid bass out of 75w to his drivers.

Billy Mays

Discussion Starter · #18 · May 21, 2009

what about these morel's with those alum SEAS you listed?

http://www.morelhifi.com/products/pdf/mw265.pdf

these morel's seem to fall off after 5k. those tweets list 2.5k as their bottom. so you could cross at like 3k?

Billy Mays

Discussion Starter · #19 · May 23, 2009

MiniVanMan said:
I'm gonna be blunt. By the time you understand everything you'd need to know to implement a half way decent passive solution, you'll understand how to do active.

Due to the phase relationships in a car, and complex problems like extreme lobes, passives are incredibly difficult to optimize for auto applications. So, unless you're willing to invest in some test equipment that won't be cheap, I'd suggest learning about crossovers and just implement an active solution.

However, here's a step by step tutorial on how to design a passive crossover for a home application. Gets considerably more complicated when you try to implement in a car, and a home designed crossover may not work well in a car anyway. It is a good start though.

http://www.rjbaudio.com/Audiofiles/FRDtools.html

thanks for the link but it seems that going passive is a complicated way to get a not as good answer to the problem.

so lets talk about how to do this. i basically need some kind of signal processing or i need to make stuff. given my situation i'd say it's easier for me to get a HU or something rather than building something. as it stands i have alot on my table as far as fabrication projects/ideas so i don't think tackling active crossovers is on the agenda. so does that mean i have to scrap this idea and go with a set from like rainbow or can i get a sufficient software solution with a HU like an 880prs? i'd like to still do this SEAS/morel/etc idea since i'd like to swap my HU anyway so if that's a good answer that'd be great.

MiniVanMan

· #20 · May 23, 2009

An 880PRS or Alpine 9887 are good options with the processing you'd need. I haven't seen or used the $160.00 Clarion that was talked about for a while, but that would be worth looking into as well.

I really like my 9887. Great head unit that will do everything you'd need it to.

As for mids, I'm a much bigger Seas fan than a Morel fan. Much more for your money than the Morel. Especially in that price range.

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