Stereo questions

[TM]

Damping factor and headroom have a great deal to do w/ this, the amp
being
able to control the current demands and supply the necessary current to
the
sub when necessary.

I'm not talking about low quality crap like Pyramid, so let's just get
that
right out of the equation to begin with.

Only a handful of car amps run class A, most of them are A/B, although
there
are quite a few class D sub amps now. Class A is also out of the
equation for
all intents and purposes.

In order for the bass to be tight and well-controlled, the amp feeding
the
sub must be able to supply enough current to handle the peaks- if the
amp
lacks the headroom, it will sound bad, as you have said. Sub amps in the
250Wx1
range @4ohms, 500Wx1 @2ohms is really the typical setup these days.

I need a specific recommendation on a sub, otherwise, I'll just go get a
JL 10W3
and be done w/ it- probably have a custom box made to measure and
that'll be it.

As for head unit amps, they may be sufficient to power factory speakers,
but
if you're serious about getting halfway decent sound, even a mediocre
outboard
amp will kill the head unit in terms of SQ. My old Sony 60Wx4 kills any
of the
head units I've heard and it's a bright, crappy-sounding amp as far as
amps go
(overrated too, only benched at 53Wx4 @4 ohms). My current a/d/s 40Wx6
is a much
better sounding amp and according to raw numbers, is outperformed by the
latest
high-power Alpine head units (which put out 60Wx4, supposedly). I'll put
my system
up against the high-power Alpine all day long, no contest.

Taka



-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com] On
Behalf Of Ameer Antar
Sent: Wednesday, July 03, 2002 1:24 PM
To: quattro at audifans.com
Subject: RE: Stereo questions


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---
--__--__--

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