🚀 go-pugleaf

In article <2413@uokmax.UUCP> mcmiller@uokmax.UUCP (Michael C Miller) writes:

>   Maybe this is a stupid question but here goes.... 

Stupid? No.  Uneducated, perhaps.

>   I want to build
>   a sub-woofer for my stereo but I need some help designing the thing..
>
>    I can handle the low pass filters, (they are built and work well ), but 
>   I want to drive a single 15" speaker , not one per channel...

Good idea. Single speaker systems are easier to balance for a first-time
project.  Where are you crossing into the sub?  What's the rest of the
system look like?

>    Does anyone know of a passive summing circuit that will handle 120 watts
>   per channel ? 

Aaakk.  You're processing the OUTPUT of your amp?  Evil. Very Evil.
You really want to do the low-pass and summing stuff in the pre-amp
stage of the system.  With a few op-amps and some discretes, you can
build a really nice n-order filter (If you don't own the active-filter
cookbook, buy it now).  You also want to put in a sub-sonic filter (if
there isn't one in the proc chain before all this). This will guard
against one of the causes of "destructive excursion" (defined as
throwing your voice coil across the room at high speeds).  That really
low frequency stuff will cook you if you're not careful.  Once you've
got the low-level signal, you can either run your amp in bridged mono,
or buffer it and send it to both channels.  

I don't mean to get nosy here, but what kind of enclosure are you using
for the woofer?  Tuned or sealed?  If tuned, what frequency?  If you
don't understand these questions, that's answer enough.  Sorry if I seem
a bit pedantic here, but designing speaker systems is a LOT more than
just stuffing a driver in some box and putting power behind it.  If you
have more knowledge that I have assumed, I apologize, but it seems like
you may be in over your head here.  

I've recently been involved in some sub-woofer design for a specialty
audio house (not my work, I just stood around and said "wow" a lot),
so a lot of this stuff is still in my brain.  If you are interested 
in some advice re: enclosures and such, drop me a line with the model 
and specs for your woofer and maybe I can con them into using their
design equipment for a little while.

This got a little long winded, and it really belongs in rec.audio, but I
don't read it any more (got tired of mercury filled speaker wire and
black equipment panels).  Ciao.

                                                        - MM

>				sans
>   -- 
>   <  sans =>   mcmiller@uokmax.UUCP   or  mcmiller@uokmax.ecn.uoknor.edu  > 

-- 
passaret@brahe.steinmetz.ge.com              {whatever}!steinmetz!brahe!passaret