We should reject hard-to-drive speakers more often

Ralph, so the answer is = none. My best, MrD.

Back in the early 90s, TAS did a review of our MA-1 OTL amplifier. OTLs are not known for driving low impedances. The reviewer, Steven Stone, had a set of the old Apogee Full Range speakers, which were 1 Ohm. At the time we made an outboard autoformer called the ZMusic (similar to the ZEROs) that we installed between the amp and speaker- the ZMusic had a 1 Ohm tap. The result drove the Full Ranges quite well- despite the impedance, they otherwise were a resistive load and didn't need a lot of power. Steve commented it was the first time he had ever heard the speaker with a tube amplifier. 

in your experience ralph, when an autoformer is used to better couple tube amps with lower impedance speakers, is there a meaningful sonic penalty? seems to me that what is happening is many many more metal windings are being placed between tube amp's built in transformer (leaving aside the otl’s for a moment) -- and so my guess is that there must be more of the classic wooly, expansive, slightly echo-y transformer sound that is introduced into the music, more or less....

of course, this point and my question is moot for speakers that could never be driven by the tube amp in the first place, but have you done an experiment with a more ’normal’ higher impedance speaker... then adding the autoformer ... then trying hearing the sonic change from the additional transformer present in the chain?

just curious

@mrdecibel  there are a few tube amps that can power the apogee scintilla and full range, most of them have 1ohm taps. There is a guy that used to post on the apogee forum that is powering his apogee full range with Tube Research Labs amps, four monoblocks with 1200 watts total, and he has owned quite a few of the usual suspect solid state amps that are supposed to be used with this type of speaker. He says the tube amps do the best job.

@jon_5912 Wrote:

 High power class D amps more than make up for the difference in dynamic contrast between low and high efficiency speakers. 

In my opinion, a high powered amplifier that can drive lower impedances will never be a proxy for a speakers lack of true efficiency. 

Mike

I have been around the block with Apogee speakers back in the day, including the Scintilla ( I actually owned, for a year, the Duettas ). My question was, as stated, " adequately " drive? I am not fond of tube amps ( low / poor damping factor ), which is a shame, as I own horns. The times I used tubes for mids / highs, and ss for bass, I always was aware of the " transition " between the two. Listen, I have always said, " whatever the listener enjoys, that is fine. I like what I like, and I don’t like, what I don’t. My best, and enjoy ! MrD.