Subwoofer opinions needed!

[chr]

I'm planning a subwoofer using the driver below (have been laying around for a couple of years). The subwoofer is primarily intended for home cinema use, but must be descent for audio as well. Have this 15"-driver, probably intended for car use. A 65 L closed box would give a f3 of 61 Hz, which is way too high. A ported Butterworth B4 would result in a f3 of 38 Hz and 85 L. May be adequate for cinema, but may be too boomy for audio use, don't know .... I do not want a too bulky box, maximum 125 L net or so. Would like to hear your opinions what to do. Have been thinking of a electronic assisted system, servo or 12db/octave bass-boost for a closed system. Opinions?

Driver data:
Rdc = 3.5000 Ohm
Qms = 6.5501
Fo = 43 Hz
Qes = 0.569
Qts = 0.524
Vas = 67.9753 Litr
BL = 16.998 TM
Cms= 78.882 uM/N
Mms = 174.0771 Gram
SPLo = 94.6330 dB
Mmd = 161.5753 Gram

best regards /Christer

[planet10]

Originally posted by chr
Qts = 0.524

The Qts is too high for a reflex. Might do OK in am ML-TQWT but that would be BIG.

What i do in situations like this is an aperiodic design. Put it in as big a box as you can live with and them add a damped vent.

I am doing exactly that with a pair of Philips 12s i;ve had laying around... we will see.

dave

[chr]

Thanks for your reply.

Must admit I never heard about the ML-TQWT, is it a TL-design, or ... Could you, please, point some directions where to find information on the subject. (Should I read "phone booth" for BIG, or ?)
The aperiodic design; are there any design equations for it, or have I to rely on trial and error?

Again, thanks

/Christer, Stockholm.

[planet10]

Originally posted by chr
Must admit I never heard about the ML-TQWT, is it a TL-design, or ... Could you, please, point some directions where to find information on the subject. (Should I read "phone booth" for BIG, or ?)

The original ML-TQWT article is at my site.

Martin King has since set up his own site which is a bit more up-to-date.

And one need's to also visit Bob Brine's site.

The aperiodic design; are there any design equations for it, or have I to rely on trial and error?

Aperiodic is much less quantified. I expect with a little calibration of the resistive port material one could model them with Martin's software.

Ted Jordan did the seminal paper (4.7 MB) when he worked at Goodman's but not much has been published since then.Fortuneatly the design is fairly tolerant and quite ameanable to trial & error. This pic is a cut-away of a good, but relatively unsuccessful, commercial design.

dave

[chr]

Again, thanks a lot !

BR / Christer