[geeks] Car audio question

[Kurt Huhn]

Figured it out: for those interested.

The problem:
My amplifier has a crossover network built in to it - somehow this was not
agreeing with the speaker level inputs.  For some reason it was amplifying
line noise of some kind, that only appeared in the lower ( <50hz) range.
Wierd.  Still not exactly sure what the issue was.  However, I did find that
it only happened when the crossover feature was enabled, and the line-in was
hooked to the amplifier.

The fix:
I had a stand-alone crossover unit hanging around that I bought by mistake.
Turns out it wasn't a mistake, I just bought it before I needed it.  At any
rate - I used the crossover to filter the speaker-level input, split off the
low-range frequencies, and convert to line-level.  Now the amp has
line-level input, isn't trying to split frequencies, and is only boosting
the signal - which is only the low level ranges.  The result - no wierd
thumping, and clean sound.  Well, almost clean - now I find the subwoofer
isn't powerful enough for the amp - figures.

Next step - an actual subwoofer instead of some crap I recovered from my
attic...

Goes to show you - use purpose built components, and let each one do the job
it was designed for.  It also shows, your whole system is only as strong as
the weakest part.

Kurt


----- Original Message -----
From: "Kurt Huhn" <kurt at k-huhn.com>
To: <geeks at sunhelp.org>
Sent: Wednesday, September 05, 2001 8:16 AM
Subject: Re: [geeks] Car audio question


> Ford Taurus - factory stereo, the amp is an American Legacy 300W.  I'll
> double check the ground today - I suspect that might be it.  It is
> *possible* that I forgot to completely ground the chassis of the stereo
> unit.
>
> Kurt
>
> ----- Original Message -----
> From: "Matthew Poertner" <mrblue at mrplaid.com>
> To: <geeks at sunhelp.org>
> Sent: Tuesday, September 04, 2001 11:52 PM
> Subject: Re: [geeks] Car audio question
>
>
> > What kind of car?  What kind of amp?
> >
> > Check and make sure you have a good ground...
> >
> > I used to play with audio equipment quite a bit in high school.  I had a
> > 1970 VW Fastback.  It had a similar problem.  Also whenever the bass
> > hit, the headlights would dim.  I guess the little generator didn't put
> > out enough juice and it was taking out quite a draw from the battery.
> >  So, I went to my computer repair class and tore apart some old
> > computers and took the capacitors (Two - about the size of a coke can).
> >  I hooked it up so the amp took the draw off the caps instead of the
> > battery.  Sounded hell of clean and the headlights didn't dim anymore.
> >
> > -Matt
> >
> > Kurt Huhn wrote:
> >
> > >Slightly more geeky today,
> > >
> > >I just installed an amplifier/subwoofer combo in my car - but can't
> utilize
> > >it to it's full potential.  The reason is, whenever I try to increase
the
> > >output the subwoofer will thump and hum.
> > >
> > >It *sounds* like it is firing _roughly_ once per three RPMs.  This sort
> > >makes sense to me - since my car is a 6 cylinder.  This is just by me
> timing
> > >the thumps from the subwoofer - not that I actually hooked up a tach to
> my
> > >tach-less car and ran it against the thumps.
> > >
> > >It sounds to me like I need a line filter for the power lead - but
> figgered
> > >I'd ask here in case anyone else has come across the same problem.
> > >
> > >Any ideas?
> > >
> > >Kurt
> > >
> > >_______________________________________________
> > >GEEKS:  http://www.sunhelp.org/mailman/listinfo/geeks
> > >
> >
> >
> > _______________________________________________
> > GEEKS:  http://www.sunhelp.org/mailman/listinfo/geeks
> >
>
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