"Ron" wrote in message
...
On 28/07/2010 17:50, Arfa Daily wrote:



Didn't Phillips do something like this back in the 70's? Motion
feedback
or some such daft name?

I think they called it 'David', it was a motion feedback woofer in a
powered-speaker
form factor. This kind of system can control the low frequency
behavior
of the cone very accurately. Mossbauer apparatus uses the same
hardware for motion control with .01% distortion, but that's a
linear-motion
measurement, no idea what the air movement effectiveness is.


OK, both. Don't remember the Philips system, but then the company that I
was working for back then, didn't do much with Philips. Still, that
sounds like the sort of system. Those specs for the Mossbauer are
impressive. I guess that's the sort of thing that it's going to be,
given the claimed value of these things. I've just been listening to a
CD through them. They sound nice, and very smooth with a very flat and
stiff sounding bass. Quite easy on the old lug-holes, but I'm not sure
that I would rate them as 16 grand more easy than my home-built EMI 13 x
8 cabs from the 70's ... :-)


Arfa

Ahh 13 x 8's did they have the whizzer cone in the centre?

--

Some of the 13 x 8s did have, and I seem to recall that some also had a
bracket fixed across the centre, which held a pair of black Mylar-coned
tweeters. The 13 x 8s that I used were the 'straight' bass version. I built
3 ways with them, using the matching EMI 8 x 5s for the mids, and they did
indeed (still do) have a whizzer cone in the middle. The mids are separately
baffled by their own sub-enclosure behind them, and inside the volume of the
bass cabs. The tweeters are Eagle aluminium domes. Very bright sound. I
picked them because I loved the clarity that they added to the top end of
the sorts of music that I was listening to back then - mainly heavy and
progressive rock. The crossovers are also Eagle. They used to make some good
products. I guess they don't exist any more. :-(

Arfa