[V8] Bose amps and speakers

[Craig Nicol]

<snip> I have trouble believing a single cone, paper speaker is going to
give any richness in sound or differentiate between treble and bass. 

With my rear's removed, I'm going on my fronts right now.  They sound okay,
but I can adjust the treble all the way up and down, the bass all the way up
and down, and not notice any real difference in sound.  The entire system
seems a bit too ... bias towards treble, to begin with.  

Maybe it's my ears! :D

 

~Scott <unsnip>

 

Scott, Here's what's different about Bose speakers that make them different
than anything else.

1)    Ultra light weight voice coil (aluminum flat wire), Makes the speaker
"motor" much lighter than anything else out there. This, in combination with
the small diameter speaker, makes it responsive at high frequencies. These
units are responsive above human hearing limits.

2)    The motor (The voice coil is a linear electric motor) has about twice
the displacement of a conventional motor.  This is what allows the small
diameter speaker to pump the air required to produce the large displacement,
low frequencies.

3)    The aluminum voice coil has 0.2 ohms impedance; regular speakers are
4-ohm.  (Less ohms = more current) Since it's aluminum, it can take the heat
(current) that would fry a regular speaker.  With this low impedance, it can
manage much higher input current (power) without an issue.  This is
important since 12-volt cars are limited in voltage to 12 or 24-volts,
depending on the amplifier configuration.

4)    The Bose amp is a switching amp, so there's almost no heat, especially
considering that each amp (depending on the specific calibration) produces
50-200 watts (each). Regular amplifiers of this power capacity are in finned
boxes about 10" square.

5)    The Bose speaker enclosure is tuned to resonate at the weak
low-frequency output areas of the speaker performance curve. (Typically
50-70Hz range).  This permits the relatively small cone to produce the bass
of a much larger speaker. (If you wanted 30hz, they would be challenged
however)

6)    The Bose amp has a 32-pole equalizer that's tuned to the interior of
the car, compensating for acoustics and materials.  Each EQ is specific to
the speaker position - usually F/R but sometimes all four positions are
different.  (32-pole is like having an equalizer with 32-slides *for each
speaker*.)

7)    FWIW, Bose (and the OE engineer that's on the project) set the sound
image to the front - so the dashboard is a virtual "sound stage".  This is
part of why the treble is relatively fixed and part of why the fader
"doesn't seem to work"

8)    FWIW-2 Part of the concept is that audio engineers did all the
homework so everyone that buys one gets the "designed experience" regardless
of skill or interest.  The concept is good except when you are a "tinkerer".

The tone controls are an issue with the head unit.  Bose requires OEMs to
have only Bass and Treble reduction - the units are tuned so that at max
bass and treble, the sound is "right". Almost all media has unnatural bass
and treble emphasis, these controls allow for some compensation. Since Bose
believes that their sound is "natural" (no accounting for taste) why would
anyone want anything else? (a little arrogant, eh?)

The fader control is usually set for "rear cut" only.  As a front seat
passenger, you don't see all that much change.

 

You could swap head units and get past some of the tone/fader issues except
that the output of the Bose-model head unit is 1-volt nominal where normal
head units are in the 12-24v range at the speaker outputs and millivolts at
the low-level outputs.  I've heard about converters, but they may add
distortion.  Also, you won't be able to use the "in-dash" display if you
switch head units.

 

BTW, in a prior life I was an OE engineer responsible for our company's Bose
labeled products. (Acura/Honda).

HTH, Craig Nicol

90 V8Q

95 S6 Avant (both Bose equipped)