What is your take on high efficient speakers vs. low efficient speakers?

Hi @sns ,

You mentioned a very important question.
Most low power DSET (45, 2a3, 300b,...) made today and before designed for very easy load and very hight sensitivity speakers file full range Lowther, Fostex, Voxativ,...
But in therm of pik volume these amplifiers can work for midsize room and ~95dB sensitivity speakers like big JBLs and Tannoys. But in the real live they don’t work properly even with more sensitive Klipsch and vintage Altec speakers.
The main design issue is weak power supply and weak driver tubes. The only SET amplifier I know (probably there are another) that don’t have these issues is Coincident Frankenstein.

I have been using a good DIY 300B DSET (6sn7 input, 6f6 driver) since 2006 with Altec 604E. This combination played nice but it had pronounced genre preferences. It was good for small jazz and classical groups, great for vocals but disaster for any kind of electronic music, rock, fusion jazz.
When I increased capacitors value and quality (oil capacitors) in the power supply and divided the right and left channels PS by resistors. It dramatically improved bass, dynamics and separation on bass heavy complicated, congested music. My solution is not optimal as my stereo amplifier uses one power transformer, rectifier and choke. Monoblock solution should be significantly better.
But the bottom line - the main issue in DSET in combination with big woofer 15" speakers is not lack of power but lack of ability to produce enough current. And the reason for this is not enough powerful power supplies. To drive 15" speakers some audiophiles go in the direction of big 845, 211 DSETs, but I’m not sure that this solution is the only one. 2a3 or 300B with a good big power supply can be another very good and more affordable one.

Regards,

Alex.

Lower efficiency speakers gives designers much more opportunity to “voice” things. At least that’s my uneducated opinion. 

The main design issue is weak power supply and weak driver tubes. The only SET amplifier I know (probably there are another) that don’t have these issues is Coincident Frankenstein

Agree completely!

All low power SET amplifiers are not created equally. Some will succeed admirably where others will fail, and for the very reason you eloquently state. Robust high quality power supplies and appropriately chosen driver tubes are critical steps that have to be taken.

As far as I’m concerned, the contribution of a component’s power supply can not be overstated. In the best sounding/performing components this is where the money and attention is wisely committed. The Coincident Frankenstein is a good example but there are certainly others as well.

Charles

@phusis , horns are a very alluring proposition. They are efficient and there is no question they can play louder than any other type of system with low levels of distortion. You can also control the radiation pattern to limit room interaction, another big plus. Unfortunately they fall short for a number of reasons. There is no such thing as a full range horn. You are forced into having a crossover somewhere in the midrange or upper bass. Many horn systems run a dynamic woofer well into the midrange, so much for low distortion. It would be a complicated mess trying to make a line source horn system.

Line Source systems are the only way to get into the first 10 rows. ESLs can cover 100 to 18 kHz no problem, no crossover. They maintain the lowest distortion levels throughout that range. Crossing to a sub at 100 Hz is much less of a problem especially if done with steep digital filters. The only disadvantage ESLs have relative to horns is that they are much less efficient. The fact that they won't play as loud is not a problem because they will do 105 dB and anything louder than 100 dB is certainly damaging your hearing. 

I am a huge proponent of actively driving loudspeakers. This does not mean that all the wizardry has to be within the loudspeaker. You can actively drive any loudspeaker with outboard components. I have been doing it for 20 or so years. There is no other way to get the absolute most out of any system and this is not IMHO. I have seen, heard and measured enough to know this is a fact. If there are any downsides to this they are far outweighed by the benefits. Trying to maintain a totally analog system is like owning a vintage Corvette. If you are a track junkie you will go a lot faster in a C8. I'm not into owning antiques. I like driving fast.

SET amplifiers are about as silly as cable elevators.