building the pro-38 audax kit

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murphythecat8

murphythecat8

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Joined 2011
#1
hi
I want to make my speaker fully passive.

I already use the pro 38 crossover for my mid (audax pr170) and highs (audax pr 120) with a perfectly flat response. Right now, my bass is active, but I want to change that.

you can find the kit details here (post number 3):
http://www.diyaudio.com/forums/multi-way/211669-good-diy-pro-driver-designs.html

The original bass driver of the pro 38 kit was this:
https://www.google.ca/search?q=audax+hd+38+s&oe=utf-8&rls=org.mozilla:fr😱fficial&client=firefox-a&gws_rd=cr&um=1&ie=UTF-8&hl=fr&tbm=isch&source=og&sa=N&tab=wi&ei=rUg2Uv3WOJLG4APChoHgAg&biw=1920&bih=950&sei=r0g2UtijGrXi4AOK64CwCg#facrc=_&imgrc=MLJtreaB8Q5LkM%3A%3BG3F_-2ItoE6n6M%3Bhttp%253A%252F%252Fwww.audax.com%252Farchives%252Fhd38s100.jpg%3Bhttp%253A%252F%252Fwww.audax.com%252Farchives.php%3B780%3B568
the driver is 101 DB/W
So i'm thinking that I could use the same crossover values of the pro 38 kit and try to find a driver with around the same efficiency as the original woofer and probably have a good result....

I think I could get pretty close with the Eminence kappa pro 15. Its also a 101 db/w
Eminence Kappa Pro-15A 15" Cast Frame Driver 290-422

What do you guys think?
 
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#2
It looks as if the crossover for the woofer is based on impedance rise compensation and a second order filter. It shouldn't be too hard to tweak this to work with a similar driver. It may even sound good as is.
 
#3
AllenB said:
It looks as if the crossover for the woofer is based on impedance rise compensation and a second order filter. It shouldn't be too hard to tweak this to work with a similar driver. It may even sound good as is.
Click to expand...
if I try and the results are not as hoped, will I have to change the coils? I want to try this, but if I have to change multiple times of coils value, this experiment might be expeansive. I could however get super cheap film caps to make sure sure it sounds good before investing... My question is, if the results are not as hoped, what will have to be twaeked? the coils or just the caps and resistors?
thanks!
 
#4
Hmmm. I guess if Re and Le are the same then the compensation can stay. The crossover appears to be somewhere in the vicinity of 500Hz so I guess the actual bass resonance wouldn't be a major factor if it's at least similar to the kit. The box (externally) should function similarly.

I'd study the frequency response of the original woofer and the prospect, looking for smoothness and making sure the efficiency figure quoted wasn't just taken at one point.

Electrolytics should be OK for the caps anyway. With a resistance of just less than an ohm, you're probably looking either at a slightly expensive air cored coil or a fairly cheap iron cored one.
 
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