[s-cars] Replacing Original Bose Head Unit

[Adam D.]

The problem with replacing anything within the signal path of a Bose system
is that Bose applies heavy equalization to compensate for gross frequency
response errors in their speakers.  Rather than actually making a decent
speaker driver, Bose chooses to cover up their crappy designs by altering
the signal.  The biggest drawback of this method is increased strain on the
amplifier.  In order to get decent output at the frequency extremes from a
full range driver they boost the bass and treble considerably, effectivey
making those sounds (which happen to be the most difficult for an aplifier
to reproduce cleanly) "louder" and demanding more power from the amps.  So
in order for this method to work the amps have to be big.  The Bose amps are
not.  This is why the sound totally changes character as you turn up the
volume.  Distortion sets in and the sound becomes brittle and glarish in the
highs, and flabby and flatulent in the lows.  No Highs?  No Lows?  Must be a
Bose.

To make matters worse Bose speakers have a wierd impedence...something like
2.7 ohms, and the line level signal from the head unit is an odd voltage as
well.  These quirks (especially the heavy equilization) will almost
invariably alter the performance of any aftermarket equipment  (usually for
the worse) you try to install.  So unless you remove all vestiges of Bose
from your car, better keep it stock and find a factory changer or the
compatible Sony (S4) or Panasonic (S6) unit.

TTFN,
Adam Dieckerhoff
Head Tech, Achtuning LLC

'93 S4 (black/ecru)
'00 A6 2.7t (black/melange)
'00 TT 180qc (silver/gray)
'86 5kcstq (its baaaack!)
fourquattros at hotmail.com
Bellevue, WA.   USA



----- Original Message -----
From: "Timothy Lynch" <tlynch at aquaengr.com>
To: <s-car-list at audifans.com>
Sent: Wednesday, June 12, 2002 9:41 AM
Subject: [s-cars] Replacing Original Bose Head Unit


> This is a multi-part message in MIME format.
> --
> [ Picked text/plain from multipart/alternative ]
> As with everyone that owns a UrS4 or UrS6 w/o the CD changer option, I
> have been running through hoops in an attempt to find a solution.  I
> have been told that if I replace the head unit that I would have to also
> re-run the speaker wires in order to bypass the speaker amps (which
> supposedly wouldn't sound as good as the factory system), or replace the
> entire system head unit, wires, and speakers (very pricey solution).
> Other options are to install an RF modulator type CD changer (my last
> choice) or to locate the original CD changer that was offered as well as
> the correct harness (nearly impossible to find and requires more
> patience than I think I have).  I was thinking (dangerous sometimes as
> we DIY's all know), what if I were to purchase an aftermarket head unit
> that has no built-in amp (i.e. Alpine 7995)?  Would there be any
> problems with doing this?  Are there any other alternatives that anyone
> has done and been happy with the results?  Thanks!
>
> Tim Lynch
> 1992 Audi S4
>
>
> --
>
>
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