Adding a ZERO which is after all a transformer after the otl ? Does it not defeat the whole purpose and sonics of otl in the first place ? How much of the otl sound remains after that ?
IMO/IME there is a simple rule of thumb: the ZERO should help and not hinder. So if its doing the job all the transparency and speed that OTLs are known for will be intact- after all, the ZERO has wider bandwidth than the amp itself- usually with tube amps the transformer is the bandwidth limitation.
1) Doesn't the 85db rating suggest that the M60s would be necessary for adequate power?
2) Perhaps I'm oversimplifying, but doesn't the 8ohm impedance tell us that zeros shouldn't be necessary?
A lot depends on room size, how lively it is, how close one is to the speakers and personal listening habits. Given those numbers I would be more likely to go with the M-60s, but in a smaller room there might be no point. The impedance does suggest that the M-60s would be fine without a set of ZEROs.
Al, I disagree with the 2nd sentence to the last paragraph:
..."It is a great disfunction {sic} to music loving audiophiles for speaker manufacturers to be making 4 Ohm speakers with 3 or 2 Ohm impedance dips, and then expect amplifiers and speaker cables to be able to transfer music into a load approaching a dead short."...
Some of the popular and most accurate audiophile loudspeakers ever made have such impedance plots, and many, many amplifiers and most speaker cables work quite well with them.
All amplifiers, tube and solid state, make more distortion into lower impedances. While it is true that many solid state amps drive low impedances with power, making them do so is not the same as saying they are sounding their best. Generally speaking all amps will sound better (meaning: smoother and more detailed with greater authority) driving a higher impedance.
I have a set of Classic Audio Loudspeakers at home. They are 16 ohms, 98 db 1 watt/1 meter, go to 20Hz no worries and have no breakups in the audio passband (owing to a pure beryllium diaphragm with a Kapton surround in the midrange unit, which handles most of the range of the speaker)- they are very smooth and detailed. They had to beat out a lot of speakers in order to find their way into my home. Dunlavys are nice but these are better. Not as cheap though...
As I mentioned before, its a Bad Idea to make an amplifier work hard; tube or solid state. It might surprise some people here that OTLs can make as much current as a solid state amp, and when you think about it the reason why is obvious- they have to do the same work. But if you want to get the best out of them you present them with a reasonable load and then the magic happens. Because OTLs can be just as fast or faster than a solid state amp (the output section risetime of our amps is around 600V/microsecond) and lacking the odd ordered harmonics that plague solid state designs, they can be quite beguiling as you can simply hear details that other amps seem to miss.
The idea is just the same as if you have a fine car, motorbike or bicycle- it will handle better and be more confidence inspiring if it has good quality tires. Inappropriate tires will not allow you to realize the performance that is possible.
