Stereo questions

[Ameer Antar]

I'm not sure what you mean by 'control the woofer'? I'm guessing this means that
the cone movement (and thus sound) is accurate to the original signal... The thing
is, even if the speaker is rated at 1000W, a good quality low power amp will
always sound smooth and controlled. The good amps have low distortion even
near the max rating, especially those using class-A circuitry. Beyond that they will
shutdown to save themselves. But the sound level will be much lower, esp. if the
woofer is inefficient. Low quality amps will fart out the crappiest sounds near their
max rating whether it's at 20W or 500W. Point is, sound distortion has more to do
w/ amp + spkr quality than wattage. One thing about power is that there is a much
larger difference in volume or dB between 1W and 10W than between 300W and
400W. dB's are in a logorithmic scale. So if a speaker is rated at 500W, 300W for
an amp is reasonable, as long as you know where the limits are. (How loud do ya
really want?) If you wanna greet you neigbors at the end of the street w/ your
subs, then high-power, low efficiency subs will work great, but if you want to be
more merciful on your car's electrics and your ears, medium power, high
efficiency subs are the answer. Speakers w/ low Fs (resonance freq) will get those
low organ notes out, as long as there is enough cone area (separate or combined).

About head unit amps, they've actually come a long way since several years ago.
Head units had the problem of only being able to use 12V for the audio amps, and
many used cheap IC packs that had terrible quality and very low power. The
problem was the 12V power was too low. An amp can only produce an output
signal whose amplitude is less than half of the amp's voltage source (audio signal
has a + and - portion). Outboard amps bypass this problem w/ DC-DC conversion
which converts 12V to +/- 20-50V. So now the amps have plenty of source voltage
to amplify the incoming signal w/o any distortion. Finally they've done the same
for head units using miniaturized electronics to convert 12V into some higher +/-
voltage. MOSFET's are very good at doing this b/c they're highly efficient and run
at high frequencies. That's why you often hear things like MOSFET's in the newer
head units and they've been used all along in outboard amps. Although I wouldn't
recommend using a head unit to power a sub, the fact that it is possible and that it
sounds very reasonable, proves that they can be useful, if at least used to power
small drivers above the subwoofer freq. range. Of course, there are many
advantages to using outboard amps, esp. w/ subs, but head units aren't as bad as
they use to be...

-ameer


---Original Message---
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Message: 8
From: "TM" <t44tq at mindspring.com>
To: "'Audi Quattro'" <quattro at audifans.com>
Subject: RE: Stereo questions
Date: Tue, 2 Jul 2002 23:01:17 -0400

Brad-
No, I have not considered two 8"- the bass extension is not enough IMHO
to make it worthwhile.

How much power were you running to the speaker? You need a lot of power
to
control the woofer properly- I have this problem at home, feeding only a
measly 60W to my speakers when they really need 200W or more to properly
control the woofers and keep it from getting too boomy.

IMHO, 100W RMS is not enough to run dual 10s. I'm planning on feeding a
DVC sub 160W to each coil, total 320W RMS and that's still somewhat
underpowered.

If I had a monoblock amp, I'd use it, but I already have this amp, so
that's
why I'm not feeding it more. I'd go w/ something like the JL sub amp-
250Wx1
at 4 ohms, goes to 500W at 2 ohms, that would do very nicely feeding the
sub, but I have the amp I'm using already.

I've not heard of many car speakers running 8 ohm- standard load is 4
ohms.

I plan on using a small sealed enclosure for a single 10 and from what
I've
heard so far, the JL 10W3 is not a bad SQ sub. Kickers are not known for
SQ,
nor are Cerwin-Vega, two of the other suggestions I've gotten.

Taka