Tube amps and speaker ohms

Bartokfan I think you are confusing impedance with sensitivity. Nevertheless, both are factors that influence how well (or not well) your amp will do.

Rule of thumb is to have a speaker with simple cross over design (or better, no cross over), benign impedance curve, high(ish) impedance and high(is) sensitivity.

I will probably get flack from a couple of SET guys for saying this, but I do not believe any single tube is better per se than another at orchestra (or opera, jazz, rock or anything else.). However, not all amps are equal, and some will perform way over what their rated output would suggest they can.

Don’t get bamboozled into buying a huge tube amp to drive tube unfriendly speakers. Get the right speakers and every tube amp will work well (or work as well as it can).

If somebody tells me his speakers worked fine with his 100 wpc plus tube amp but not with his 50wpc tube amp, I run away. That is the speaker I will never want own, even if I get paid to take them. Proper tube friendly speakers will work well with 2 to 3 wpc tube amps.

As far as orchestra/opera goes, I have had good results with all my tube amps on my speakers. These amps were 300B SET (x 2), 6C33 SET, 6550/KT88 SEP, EL34 PP (x 3), 6550 PP, EL84 PP. I’m probably missing one or two, but the point is they all worked great for orchestra because I mated them with the right speakers.

Once you have tube friendly speakers, you can try any tube type and amp configuration and always end with a smile on your face.

Regards
Paul

A 4 ohm speaker rated at 92db? Quite unusual. Lower impedance speakers are almost always much less efficient. Just a thought...

On the topic of loudspeaker impedance and crossover complexity, "simpler" doesn't necessarily translate into "easier to drive". It is quite possible that elements in the circuit that add to the visual complexity are smoothing the impedance curve, reducing the phase angle, and making the speaker a much easier load to drive. Since we don't get to see the crossover and even if we did we probably couldn't reliably predict the impedance curve just by eyeballing it (at least I sure couldn't), the best bet is to look at the impedance curve itself. That is what the amplifier sees, and whether a tube-friendly impedance curve is arrived at by a complex crossover or by an extremely simple one doesn't matter to the amp.

Duke
dealer/manufacturer

05-22-07: Audiokinesis
On the topic of loudspeaker impedance and crossover complexity, "simpler" doesn't necessarily translate into "easier to drive". It is quite possible that elements in the circuit that add to the visual complexity are smoothing the impedance curve, reducing the phase angle, and making the speaker a much easier load to drive.

How fortunate are we to have the participation of designers/builders like Duke who dispel misconceptions and provide facts that enable us to cut through the clutter?

It's the primary reason I keep coming back to Audiogon threads.

Thanks, Duke.

Paul
I googled impedance. Its a load issue, 4 ohm speakers create a heavier impedance/resistance level vs a speaker at 8 ohms. Now I'm not sure why some Seas Excel designs are 8 ohms: Thor and several Tyler designs all with lower db levels at 87, and other Tyler designs with Seas Excel are at 4 ohms but have a higher sensitivity, 92. Both use the same copper magnet/motor. Truly a beast to drive correctly and will suck the life out of any tube amp that ain't got the Trans and/or tubes to push the current up and out the voice coils and make the speaker sing. i kind of envision the Seas Excel drivers as a panel/electrostat but in the shape of a conventional cone.
So impedance is the resisitance of the speaker to amp. Sensitivity is how well/or poor the speaker responds to 1 pure electrical watt.
Elevick, that is odd, the Lin Sig Sys is 4 ohm BUT 92 db. Tyler somehow figured out the crossover to function at a higher rate of sensitivity.
What happens in this case is that the vol needs to be turned slightly up to achieve same results on a 8 ohm speaker. IOW my MTM Thors at 10 o clock sound at the same db as the Lin Sig Sys at with the vol at 12 o clock. WITH THE DYNAMICS BEING EXACTLY THE SAME. Jadis has done something with the process in making the trans that allows the amp to drive as their web site says "any kind of speaker"...of course I wouldn't wish to push my luck on a expensive tube amp with 4 ohm speakers. This is why I say tubes "prefer 8 ohms", its a realiability issue. Never want to over work the horse, as they say.
My next speaker will be the Tyler 3 way called the Lin Sys 2, the speaker that Sally Renyolds reviewed in Absolute Sound last Oct. She had nothing but good things to say on its performance. The dual W18's in the Thor's worked fine for past 4 yrs, now I'm ready to move up the next level and get in on some the 25-35 hz's I've been missing.