[Arny Krueger]

"Sonnova" wrote in message

On Sat, 12 Jan 2008 07:58:04 -0800, Arny Krueger wrote
(in article ):

wrote in message


Consumer reports used to test them when they did high
priced speaker systems.

This led to a lengthy lawsuit that Bose eventually lost
on first amendment-related grounds.

The had their usual graphs. You
also have to know how CR tests speakers. They play back
noise while they are rotated 360 degrees. I don't know
if anybody else does this.

Polar response curves are fairly common where
loudspeakers are implemented as technical tools, such as
live sound. Lots of loudspeaker development labs have
turntables for rotating speakers while they are being
measured.

If you understand this, one can make certain judgments.

Polar response is very important for predicting the
performance of a loudspeaker in a given environment.

The 901's after the series II's
have no internal damping, very BAD.

Not necessarily.

Its easy to add some.

Certainly Bose is not leaving it out to save the big
bucks.

The overall response is fairly smooth, with peaking
around 300 Hz, and not much above 12 kHz.

Bose sort of broke ground by applying the theory that
one can equalize a system for flat response below the
bass resonance, if the bass drivers have enough linear
excursion. It takes a lot of power, but these days clean
power is relatively cheap.

But that wasn't necessarily true in the late sixties when
the 901 was introduced. In those days, 60 watts/channel
was considered a BIG amplifier and most people had amps
in the 25-40 watt/channel region (the Dyna MKIII and the
McIntosh 60/260 being pretty much the top of the power
output game).

One of the initial reviews was based on the use of a pair of those 300 watt
Mac monoblocks that were built for cutting lathes.

Transistor amps were just becoming widely
available then, and when Dynaco came out with their
ST-120, It was considered a breakthrough in
price/performance for such a big transistor amp*.

The ST120 is just 60 watts a channel all over again. The first generation of
amps that were really capable of driving a 901 right were the DC 300, Dyna
400, Bose 1801, etc.

*Barely! They were using the output transistors (2n3055s
IIRC) at so close to the ragged edge with respect to Vce,
that they had to hand pick the transistors that they
used. I know first hand the rather dubious "pleasures" of
trying to get one's ST-120 up and running again after
blowing a channel by circumventing Dynaco's parts
department and buying generic replacement transistors
locally. I'd get the thing put back together, clean the
heat - sink goop off of everything, turn the amp on and
listen for an hour, maybe two hours, and then Bang! Blown
again! Trials and tribulations with early SS amps blowing
their output (and often driver) transistors (the H-K
Citation 12 had a similar problem) might be the basis of
my preference for tubes :-)

I have a Dyna 120 with the origional outputs. In fact AFAIK it is all
origional - I can detect no signs of any repairs anyplace. Last time I
tested it a couple of years back, it met or beat origional specs.