Hi All,
I just picked up an old Kenwood M1 power amplifier (105 watts a
channel) and I noticed there is a second set of speaker connections for
each channel labeled "sensor". The information I have is this amplifier
has a special feature called "Sigma Drive" that "extends the negative
feedback loop to the speakers". Just what does that mean to me and how
do I connect it up, and more importantly does it work? I have it hooked
up via the normal speaker connections now and it works fine, but I am
always looking for ways to improve things. :)  Since I'm not aware of
any other amplifier design that uses this feature, it may not have
caught on or may not have been noticable enough to the masses. Does
anybody have any comments?
dschmoll@nyx.net (David Schmoll)
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FIDO MESSAGE AREA==> TOPIC: 183 AUDIO         Ref: DBF23080 Date: 07/11/96
From: MICHAEL SUHM                                          Time: 02:51am
\/To: DAVID SCHMOLL                                       (Read 4 times)
Subj: R: Kenwood Sigma Drive

DS>Hi All,
DS>I just picked up an old Kenwood M1 power amplifier (105 watts a
DS>channel) and I noticed there is a second set of speaker connections for
DS>each channel labeled "sensor". The information I have is this amplifier
DS>has a special feature called "Sigma Drive" that "extends the negative
DS>feedback loop to the speakers". Just what does that mean to me and how
DS>do I connect it up, and more importantly does it work? I have it hooked
DS>up via the normal speaker connections now and it works fine, but I am
DS>always looking for ways to improve things. :)  Since I'm not aware of
DS>any other amplifier design that uses this feature, it may not have
DS>caught on or may not have been noticable enough to the masses. Does
DS>anybody have any comments?
-
Hello David,
  A couple of years ago,  a lot of audio people were taking a closer
look at a spec. known as "Damping Factor".
Simply explained, the damping factor of an amplifier relates to how
well the amp can resist current that is fed back to it from the
loudspeaker as the woofer moves in and out.
-
When an amplifier sends music (AC electrical current) to the speaker,
the drivers start to move, especially the woofer.  Since the woofer
has a coil of wire with a magnet surrounding it, when it moves to
reproduce sound, it also generates electrical current.  Which it
then sends back through the speaker wires to the amplifier.
The amplifier has to accept this electrical current without letting
it effect the current that it's sending out to the speakers.
I know, confusing.
In any case, all amplifiers perform this function to different
degrees of success, which is known as the Damping Factor spec.
-
The sensor wire input that is on your amp is designed for a specially
made loudspeaker with a particular sensor output wire.  This design
was made to improve the Damping Factor, and in fact, did help
tighten up the bass response to some degree.  I'm sure that Kenwood
has/had one or two models of loudspeakers to be utilized with your
amplifier.
Yamaha also experimented with this design, but I don't know if they
still use it.
-
The concept is a good one, which does work.  Unfortunately, a person
had to own a pair of the factory speakers to utilize the function, and
most people that could appreciate the difference weren't buying
"factory" loudspeakers.
Using your Kenwood M1 amp as you are is just fine, and unless you can
find some Kenwood speakers designed with the sensor output wire, you
will not be able to utilize that function.
It is still a good amplifier.
-
Mike
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FIDO MESSAGE AREA==> TOPIC: 183 AUDIO         Ref: DBD00006 Date: 07/05/96
From: TOM MOORE                                             Time: 01:47pm
\/To: ROB APPLEYARD                                       (Read 3 times)
Subj: CAR AUDIO

On 6 Jun 96 10:11pm, ROB APPLEYARD said the following:
 RA> This letter is specifically to our lovely moderator, Bonnie.
 RA>         I can't believe that you would generalize all car audio
 RA> enthusiastes as bass hounds.  I am insulted.  It was a deqrading comment
 RA> and considering that it came from someone in your position, totally
 RA> inappropriate.  Do you really know of the challenges involved with
 RA> building a competition quality vehicle?  Apparently not, or you wouldn't
 RA> be so quick to chastize.
I have not really READ this echo in a long while.  Look through the
messages you see here and you'll find plenty of talk from the "bass
hounds".  In fact, I'd say a majority of the mail in here is from, to and
about that subject and a LOT of it is full of bad information (port size
doesn't matter) and bad spelling.  It is easy to see how the current crop
of car audio fans get lumped into a generalized catagory of cement heads.
I myself am aware of what might be involved in the creation of a
"competition" mobile audio rig.  It's just that it falls into a slot I
file away as useless.  Once something is loud, does it need to be louder? 
Once it sounds good, does it need to sound better?  I answer "no" and
"yes" to those two questions.  Loud for the sake of loud does nothing at
all for me.  Great sound, however, rocks my boat every time.  Competition
car audio, for the most part, is ONLY concerned with loud.  Max db at any
cost.  Not much of a goal as no human could actually sit in one of these
mobile earthquakes and say they 'enjoy' the audio (unless they are nuts,
deaf or both).  I have heard a couple of these 'competition' rides that
did sound pretty good, but that was when they were turned down and I could
sit in the car and listen.
I don't think Bonnie needs anyone to come to her defense - I've seen some
of her excellent retorts, but you should know that not everyone agrees
with YOUR viewpoint that competition audio is a thing of beauty.  It
requires a fat wallet, skill and devotion, but not necessarily a good ear.
Bonnie gets paid good bux for her good ear (as do I - sometimes).  Do you
see why there is a rift?
Just my opinion.
Thanks.  Tom Moore
... I hate to advocate drugs or alcohol but they've always worked for me!
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