From: gt0869a@prism.gatech.EDU (WATERS,CLYDE GORDON)
Newsgroups: rec.audio.car
Subject: Re: Call for Papers/Posts
Date: 19 Nov 92 02:08:17 GMT
Organization: Georgia Institute of Technology

In article <BxrEMD.7o@cantua.canterbury.ac.nz> deanaj@elec.canterbury.ac.nz (A. J. Dean) writes:
>Kirk Lindstrom (kirk@hpcc01.corp.hp.com) wrote:
>: Good idea.  I'd like to see more articles about how to get home audiophyle
>: quality, or at least midfi quality, sound in a car.  Im am NOT talking about
>
>And if possible, something on damping/fixing bodywork and structural
>resonances if that is a problem to anyone but me. Driving along in a

The main thing about getting good audiophile type sound in a car :




                     SPEAKER PLACEMENT AND CHOICE!!!!!

This has the most effect, in my installation experience. My ideas on
how this should be done are as follows (admittedly, these are impractical
in some cars, unfortunately).
1) Get the mid and tweeter up as high in the door as possible, preferably
aimed at about 45 degrees back toward the driver or so. If it is possible,
get them as far away from the passengers forward near the front of the
car, too. This makes MAJOR difference in the stereo imaging- I did this
and can get "all the way from outside the doors, across the dash, 
out the sides" type of imaging on a lot of pieces of music, even with
no center channel (the center channel might make it worse, in my case!-
phase distortion, false localization of L and R only material, etc)

2) Get as many good quality, either 5.25" or 6.5" midbass drivers in the
door as possible. This really makes a difference in the dynamic capability
of a system. Usually a minimum of 2 per front channel is required, for
whatever acoustic reasons. Losses in the midbass region, coulpled with 
distortion in overworked midbass drivers results in the majority if
audal problems with car stereos, IMHO. I have 2 6.5" drivers, one
Sony (L-16) and one Gold Sound (620-4) in each door; at the 
volume I listen (moderate to somewhat loud) they are adequate but
I think they could even use more power handling or power (something
"clips" a little even with 120w/ch on them and another pair of Sony's
in the rear, just between 100-350 Hz). However, this makes REAL difference
in the sound of drums, etc- I can startle a lot of people with the drum
licks in James Nweton Howard's pieces, Fresh AIre III, etc! They do 
come through with the proper snap and punch! 

3)Use as many active crossovers as possible, with seperate amps. My 
own system is tri-amped; however, I would like to have it quad-amped
but I cannot find any more of the amps I have on highs and have no 
more money to buy anymore either :-) This really helps in reducing
distortion on hard bass hits, snare drum licks, etc. The clipping
that might occur in the low frequency amps is not transmitted to the
high fequency speakers. Also, keep the power at the various frequency
ranges as balanced as possible. I have corrected a lot of systems
where a guy used 1000w on bass but a Punch 45 on highs, etc. Usually, 
if I can convince them to get at least 1/2 the power on bass on the
highs (depends on the speaker effiency, but that seems to be about
minimum) I can usually get good balanced sound. This type of power
balance usually gets rid of persistant blown tweeter problems, too.

4) Get a sub that goes as low as possible with as little inherent
distortion as possible. This usually implies getting woofers with
long cone throw or good-quality large woofers or a number of smaller
woofers in the CORRECT ENCLOSURES. I have also used custom eq to 
help bring up the extreme bottom end, especially in ported enclosures,
where the port tuning combined with the eq tuning can really be used
to good effect to smooth and extend system response, usually while
retaining very good power handling. My own sub goes down to 16 Hz or 
so (measured); this is about adequate...

5) Use analyzers to set the system but in the end, USE YOUR EARS! 
The ear can detect problems that the RTA cannot, like speakers in
incorrect phase, distortion, etc. Get the curve as close to flat
as possible, but stay away from radically tilted curves. Usually
a maximum of 6 dB drop, uniformly distributed, from 20 to 20k 
will result in pleasing balance without sacrificing accuracy and
resolution. This, of course, varies to taste. 

6) Get as much damping material in the door as possible, and brace
up anything that can vibrate anywhere in the car! I have lots 
of foam and damping mats in my doors; however they still vibrate
audibly sometimes so I am going to add more damping whenever I
get a chance. Putting thin foam between plastic/cardboard/fiberglass
panels and metal (like door panel-door, etc) can really quieten
things down. Dynamat is also a good idea- however, a friend of mine
found something called Q-pads- like Dynamat but MUCH cheaper (like
3 12x12" sheets for $7, so so) from Downey auto parts stores around
Atlanta. I would thing that the stuff could be found elsewhere with
a little research. 
 
There are a lot of other factors, of course, but these are a few that 
I think are kinda universally applicable. Other things to remember
would be to get speakers with flat response curves, regardless of 
brand (I have 6 different brands to accomplish this in my car!).
Also, the speakers have to match up correctly. The bass must meet
the midbass in frequency response, the midbass must meet the midrange, etc.
Crossover points and slopes and driver matching really make the 
differnce between a so-so system and one that makes you go WOW...

I guess that ends today's lecture :-).

Regards,
Gordon.

 
-- 
WATERS,CLYDE GORDON-Class of '93-Georgia Institute of Technology Atlanta Ga. 
"Out of the mountain of despair, we can hew the stone of hope"- MLK Jr. 
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