SET Amp question

I'm interested if anybody has experience using a SET amp with certain harder to drive speakers, like the Dynaudios and OHMs in my system, or others. What might one expect from such a combo sound wise? Could it work well say in a smaller bedroom system that will not be played too loudly in general.

Think of it this way:

The SET Amplifier is like a singer / vocalist without a microphone, and the Loudspeaker is like a space or venue in which the singer / vocalist is singing.

In a modest sized venue - the sound will be sweet because the performer can sing at their singing volume and everyone can enjoy. However, if the venue is too big - the performer has to try to sing louder - affecting tone and still not fulfilling the desired performance.

So, what you will have is a SET Amplifier that is not giving you 100% SET sound. It will be best if budget permits to get a compatible Loudspeaker.
Depends in part on the amp's output impedance and the speaker's input impedance.

Oversimplifiying a bit, a high output impedance (low damping factor) amp will put out increased power into an impedance peak, and decreased power into an impedance dip. In contrast, a typical solid-state amp will have the opposite characteristic.

So if the speaker was "voiced" on a solid state amp, and its impedance curve has significant peaks or dips, the resulting tonal balance will probably be quite a bit different on a typical SET amp, regardless of whether the amp has enough power to drive the speaker to satisfying levels. For example if your solid-state-voiced speaker has an impedance peak at 3 kHz, it will probably sound too bright and forward with a SET or OTL amp - and you would be mistaken to lay the blame on the amplifier, as the cause would be poor synergy.

Nothing good (unless you go to higher output tubes).

The Verity Parsifal/Encore is a modestly difficult load and it swallowed my Cary 300B monos whole. OTOH, the Cary 805s work just fine with the P/Es. Never even thought to try the 300Bs with my Ohm 100s (which seem to like more, more, more when it comes to amplifier muscle). I'd bet that the 805s would work, but I wouldn't expect improvement over the ARC VT130SE I'm now using, so I'm not about to schlep the 805s into the listening room in anticipation of degraded results.

The problem is that -FOR THE TRUE BELIEVER SET GUY- the low powered amps are the only true key to a happpy life. Flea powered designs just won't work in the type of application you describe and even 300Bs IME will struggle. You're left with the 211/845 designs which will probably provide decent results, but:

A) won't sound their best in such a pairing,
B) may not be "SET" enough to satisfy the experiment.

Just my experience.
Good Luck.

Good answers guys. Thanks!
The Cary 805 AEs are honestly hard to fault in comparison to even the best SET amps (which to me are 45s). I never did any sort of A/Bing because you wouldn't use the two on the same speakers - but the AEs are no slouches in any department.

To get a hi-power SET (anything stronger than a 300B) to sound really good takes a great deal of money in the power supply and output trannies. There are no good, cheap 211 or 845 SETs. Not really good anyway. The bargain gear does still give some SET sound but will be slow and rolled-off due to the inevitable bandwidth restrictions.
Pardon from the semi thread jack.
Is there anything that will minimize the speaker SET interaction. e.g. bigger, shorter speaker wire: adding additional stuffing inside the cabinets: changing bias voltage. Any suggestions?

it is possible to add circuitry between amp and speaker to present a more tube friendly load. merlin rc network option is such a solution. i have read where some more tech savy listeners have done similar themselves. agoner gallant diva has done something along this line to better run apogees of high power tube amps. so it is possible but not commonplace. not sure there is anything that can practically be done to make low efficiency speakers play louder off a flea powered set.
Do you think extra big powercables might tip the response for more at 100-200hz
Better power cables might deliver current more effetively to the amp if that were an issue but I would not expect a power cable change alone to deliver the desired results.
My speakers (EgglestonWorks Fontaine) are not the most efficient (Dynaudio Esotar tweeters), but I am able to drive them to satisfying levels in my medium/large room with Audio Mirror 45 watt SET monoblocks. Rated at 45 watts, but Vlad says more like 55, with peaks to 90. And I do love their glorious SET qualities.

Thanks. Yes, I have had several respond indicating that some better built higher power SETs have produced good results with some less efficient speakers even in lieu of a separate powered sub.
Is there anything that will minimize the speaker SET interaction?
In the case of speakers that are voiced to be used with high damping factor/low output impedance amps, such as typical solid state amps, I would expect that the tonal imbalance problems which were explained in Duke's excellent response could be significantly reduced by inserting a pair of Zero Autoformers between the amp and speakers.

I have no personal experience with them, though.

Best regards,
-- Al
Check out the GM70 SET monoblocks from SACThailand.
If you have questions about how an SET or other 'current source' amplifier will drive a speaker, maybe this link will help in understanding what is going on:
Thanks for the read Ralph! It would seem that the distortion spectrum or bandwidth is more important with respect to the preceived loudness then the intrinsic acoustic power? EG: to make a rig sound less forward one would strive to minimise odd distortions in the presents range ( 1500 Hz).
The Almarro 318B can drive some difficult speakers.I use one to drive Gale 401a speakers and most 100 watt SS amps struggle with these speakers.A 3.5ohm load and 88db sensitivity.
I've had great luck with a BelCanto SET40 (stereo amp using single ended 845's) driving my Dunlavy SCIV's which are 91dB and a stable 4-5ohm load. Dynamic, extended at the frequency extremes, huge soundstage, great body/harmonics/detail and provides the single ended "majic" people crave. A great option for speakers that are not friendly to the 45/2A3/50/300B amps.

Did you ever try your Cary SET amps with the OHM 100s?

If so, how did it sound? What were the good and bad?

Still toying with adding SET somewhere, possibly as a 3rd system in a different room with proper speakers for a SET.

I know that this would be the best option from a performance perspective. But I've already nailed that in my larger main system, so I am thinking that it would be interesting to just play with a SET and see how it sounds in different combos, even if far from an ideal match on paper. Go for a different "flavor" of sound perhaps would be a good way to describe it.

Would not think to use a SET with OHMs, but putting the SET into my second system where my OHM 100s currently reside might be a possibility if teh sound quality is good at just moderate volumes in taht I ddo not often turn up the volume much there. Current amps there are TAD hibachi monoblocks that are a good SS option to a higher power tube amp. The Hibachis and OHM 100s are a very good match in there currently and sound lovely and can go fairly loud when needed.

So I would not go to SET specifically for use with OHMs necessarily, but having the option to run that combo and expect decent results at moderate volume would be a bonus that might make me pull teh trigger sooner rather than later.

I have OHM, Triangle Titus (moderately efficient with a rep for synergy with tube amplification) and Dynaudio Contour 1.3 mk II monitors to dabble with currently.

The Triangles would likely cut it best with a SET, followed by OHM and the very demanding Dynaudios least I suspect.