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Great video interview with Bob Carver


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There are some interesting discussions - Carver is actually pretty good at communicating without resorting to techspeak--and that isn't always easy.

Some points on the discussion:

1) The Folger-can 350 W/ch amplifier that got him into business in '71 or '72 - now that was interesting. Even more interesting was that it was Mcintosh that gave him his boost. Very high power amplifiers were the rage in the early 70s because of the cost of high-power tube amps and their tendency to heat the room, and the acoustic suspension speakers that were the rage back then.

Note: I bought my Carver M1.5t and C1 pramp in 1984 to drive a pair of Magnepan MG-IIIa's. The design of that amplifier was interesting...and a bit scary when it required service 6 months later due to "component drift" issues. I liked it though for the novelty of using the power company's transformer to supplement its own power supply. [:o]

2) The Stereophile amplifier blind-blind "transfer function-matching" contest, i.e., matching the the Mark Levinson SS amp and the CJ tube amp: I really liked that discussion. I still smile when I hear that story--which has been told many times. I guess that I've never been a true audiophile. To me, it's not about pedigree but the sound that emerges--that counts. [:D]

3) The long-displacement subwoofer: although I don't think Carver talked about distortion products associated with a high-displacement woofer. But it was a common need that led up his "invisible subwoofer" - WAF. [^o)]

4) Sonic Holography: interesting, but it flies in the face of comments made by Floyd Toole concerning buyers' preference for speakers that have nearly constant coverage over a wide arc. Sonic holography requires that everyone must sit on the centerline between the speakers to hear the effect properly. Dipole speakers (like his Amazing Loudspeakers) have a significant weakness in this area. I think that the discussion about widening the apparent source width leads me to think about issues related to "sound effects" vs. more accurate/faithful sound reproduction.

5) The 6-feet-wide headphone story: that was funny and interesting. I don't think that he tried to market that idea...

6) Ribbon speakers, a.k.a., the Amazing Loudspeaker: an interesting discussion related to the follow-on small surround ribbon tweeter. However, he never really mentioned how well it worked or what the trade-offs really were. I think that he "out-Bose'ed" Bose on that product.

7) Class D amplifiers: he said a lot without actually saying something distasteful: the promise of Class D amps has been predicted for more than 30 years. Bose's failure with their first product was the credit he gave for Phase Linear Corp. surviving and thriving. Interesting.

8) The difference between tube amps and SS: Carver did say one thing that rang true. He said the basic difference between SS and tubes is the output impedance--high for tubes--which in turn react to speaker diaphragms being driven by acoustic room reflections , which in turn creates a back-EMF which reverberates, whereas SS amps, with their low output impedance, don't do that. That was pretty definitive. (Maybe a reverb unit would effectively do the same thing...and be user-adjustable...)

Chris [8-|]

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  • 3 months later...

I was always hoping that Bob would come up with a 2A3 SET amp with 500 watts per channel.

I think that he would have done it with a SS amp architecture such that you couldn't tell the difference... [6]


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I watched the whole thing and was most interested in the very last part about the difference between SS and tubes (output impedance).

He said that tubes amps "hear the room" because their higher output impedance allows the room's influence on the speaker to back EMF into the amp, where that gets sent back to the speaker...

The implication of this is curious...

If you assume that the main frequencies under this effect are those with the most power (the bass/mid bass) and that they act primarily through the woofer (because it shows the most surface to the room), and if the effect is based on the shape and size of the room; what do you have?

It sounds to me like what you have is an amp that changes its production of bass in real time based on the way the room itself responds to bass. The question then, would be; does it put a bassy boomy room under control, improve a bass poor room, or does it make thigs worse? It would be nice to discover that by hearing the room the amp "corrects" the room...

I assumed this would be mostly the woofer above, but now I;m wondering if big horns offer their front surface in a way that magnifies the room sound back to the driver (the same way the old ear horn worked for people with hearing loss)... the opening of the La Scala mid horn looks like it offers about 100sq" of surface to the room... more than an 11" speaker.

If the principle works for the high frequencies, does that mean a large room (that already sounds big) gets less added spaciousness, but a small room gets more added spaciousness?

Does this also suggest that the effects of speaker placement in the room are more crtitcal with tube amps?

I really liked the interview, that Bob Carver is a smart guy... funny how much he looks and sounds like G. Gordon Liddy.


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I too thought the part about tube amps "hearing the room" was very interesting. I guess maybe this explains the "Magic" I hear about from all the tubes & horns guys, huh? I don't own tubes but this really turns up the heat!

Prepare yourself: the answer may not be so much like "magic" but rather more like "a very subtle reverb unit"... [:o]

Chris [;)]

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