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Anyone want to offer a little crossover assistance?

167.192.191.109
Posted on February 11, 2016 at 10:07:13
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 I'd like to build Klipsch Cornwall B2 crossovers for a DIY 3-way project I'm working on (15" woofer, large midrange horn, T-35 HF horn). The drivers I'm using work well at the frequencies of the Cornwall drivers, and I have also purchased a pair of the (very nice) Bob Crites autoformers for attenuating the horns.

My issue is that (per Bob Crites) the Cornwalls utilized a 4 ohm woofer, a 16 ohm mid horn driver, and an 8 ohm HF driver, which is therefore what the B2 crossover was designed for. My drivers are all 8 ohm. Would anyone be willing to recalculate the values of the components so they would work with 8 ohm drivers? Note that per a previous poster the autoformers introduce 40mh at max, and most likely less.

 

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RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 08:17:25
Rpower
Audiophile

Posts: 280
Location: Northeast Georgia
Joined: October 27, 2000
 Look here: http://www.apicsllc.com/apics/Misc/filter2.html

 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 10:52:41
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks Rpower. I appreciate your input.

When I use that calculator to try to reproduce the stock values I can't get anywhere close to them. The published xover points are at 600Hz and 6,000Hz. If I fiddle with the crossover types and adjust the crossover points a bit I can sometimes get either the inductor or cap value close, but not both.

For example, if I try to reproduce the second order woofer portion using an L-R type crossover, by bumping the crossover point down to 500Hz I can get a similar value for the inductor (2.5mh), but the cap value is double (about 40uf, Klipsch used 20). Other crossover types (Butterworth or Bessel) produce results even further off from the Klipsch design.

In other words, the tool may be able to tell me values I can use to scratch build a 3-way second order crossover, but it does not seem to be able to help me build a version of the Klipsch B2 adjusted for the different impedances.

I do have a question you might help with though: The Klipsch design "piggybacks" the tweeter crossover on top of the midrange crossover circuit. The tweeter cap is in series with the midrange cap. Do I calculate the value of the series capacitors for the purpose of the tweeter crossover? Or is there some reason I would not do it that way?

Thanks!

 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 10:57:17
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001
 Spice would be the best way to approach this. If you provide the details on the inductor of the original I'll build it for you and then you can just download the program and learn as you play.

dave

 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 11:32:03
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks for your kind offer Dave! I'll measure the resistance of the stock parts tonight and let you know.
Gary

 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 11:34:56
geezerrocket
 Try ALK Enigineering.

AL Klappenburger's crossover(s) are in my opinion, way better than the Crites crossovers which are basically stock Klipsch crossovers with improved parts.

If you want to go all the way, look at the extreme slope paper.

Good luck.





 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 16:09:31
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003

Hi Dave.
The above image is the Klipsch autotransformer spec sheet. Also linked below is the instruction sheet for the Bob Crites autoformer with 1 DB steps.

The inductance of the Klipsch autotransformer is as follows:
Pins 0-5 37.01mH
pins 0-4 17.23mH (?)
pins 0-3 9.31mH
pins 0-2 4.75mH
pins 0-1 2.44mh

Please let me know if there is anything else I can provide.
Thanks again for your help!
Gary

 

RE: Anyone want to offer a little crossover assistance?, posted on February 12, 2016 at 18:59:47
dave slagle
Manufacturer

Posts: 5430
Location: NYC
Joined: April 27, 2001



OK... here is a start. I simmed the original crossover as close as I could then changed the values of the drivers in a "parallel" version and adjusted to get things close. I would take this as a starting point and then work from there.

I am unclear as to where there is a "secondary dip" in the original squawker but suspect it is simply a result of the interaction rather than an intention of the design.

The LTspice file is linked below if you want to play.

dave

 

RE: Anyone want to offer a little crossover assistance?, posted on February 14, 2016 at 10:47:46
BofService
Audiophile

Posts: 741
Location: Atlanta
Joined: February 28, 2003
 Thanks so much Dave!

I've downloaded the file, but having a busy weekend so have not installed Spice or tried anything yet. Next few days I expect.

I appreciate your help.

Gary

 

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