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vifa32144
02-23-2004, 06:21 AM
Does anyone have the spec's for the 1970 - 1980's Audax 8'' bextrene cone woofer? Mainly the fs., qts., and vas for cabinet building. The model number is HD20B25H4??? It has the ''four'' layer voice coil and 30 oz. magnet.

Mr. Widget
02-25-2004, 11:08 AM
I have three or four of the Audax full line catalogs from that era. If no one posts an answer to this I'll try to look that up this evening.

Widget

vifa32144
02-25-2004, 11:14 AM
I appreciate your reply, please note the 8'' woofer has the 4 layer v.c.and heavy magnet.

GordonW
02-25-2004, 08:06 PM
HOLY $#!! I actually FINALLY FOUND the #!@&^$% thing!! :rockon2: :rockon2: :rockon2:

From the A&S Speakers catalog, 1989:

Audax (Polydax) HD20B25H4C12 8" Betrene cone driver:

Impedence: 8 ohms
Size: 8"
Fs: 25 Hz
Qts: .24
Vas: 95 liters
Voice coil: 25mm diameter
Magnet: 26 oz.
Power: 40 watts
Price (1989): $38.00

I KNEW I kept these old catalogs for SOME reason! Who's da man?? :cool: :cool: :cool:

Regards,
Gordon.

Mr. Widget
02-26-2004, 10:11 AM
Well Gordon beat me to the punch!

The only thing I can add is that this driver was included in my 1979-80 Audax catalog, but only the 2 layer VC version carried over to the 1982 catalog. For some reason the 4 layer version was discontinued.

Widget

vifa32144
02-26-2004, 04:37 PM
Thank you for the help, hopefully the two layer v.c. spec's are close enough to properly load the f3.

Mr. Widget
02-26-2004, 05:37 PM
Gordon's specs are for the 4 layer version. I was only pointing out that it was discontinued for the next catalog.

vifa32144
02-26-2004, 07:53 PM
The ported box size is smaller than I thought it would be. In the 1980's there was a popular kit in a box twice the calculated size.

Mr. Widget
02-26-2004, 07:55 PM
Are your frames stamped steel or cast magnesium?

vifa32144
02-26-2004, 08:19 PM
They are the stamped steel models. I also used a thin layer of special substance to seal the dust cap, that seamed to reduce distortion throughout.

GordonW
02-26-2004, 09:10 PM
My guess is that the bigger specified box, included a correction in Qts for the insertion of a relatively-high-DCR series inductor in the crossover, which would raise the Q somewhat. This would result in a larger optimal box, tuned lower than the "textbook" solution.

Or, OTOH, they may have been using the woofer in an EBS alignment (where the woofer starts rolling off a little higher in frequency than a standard ported box, but "carries" at a slightly reduced level, lower than normal as well). This, IMHO is a good way to design- it allows pretty easy room integration of the woofer/box, without boominess problems.

If it was recommended for the larger box, I'd be inclined to use that. Less harm in the box being too big, than too small, IMHO. If you need to make it smaller for a specific applicition, then be careful NOT to use high-DCR inductors in the crossover...

Regards,
Gordon.