Speaker Impedance, Tenor OTLs, and Watt Puppies


Generally, is it better to match Tenor OTLs, or any low wattage tube amp, with 8 ohm speakers, rather than say, 4 ohm speakers? I do not clearly understand the impedance factor concept, but have been told that 8 ohm speakers are easier to drive, and also that speaker ohm stability is important. Are Watt Puppies a poor match for the Tenors? I know they will sound good, but are the Watt Puppies performance being maximized?
haydn_josef
Let me give you my two cents form what I learned about Tenor OTLs, or OTLs in general, when it comes to speakers.
OTL amps like an easy load, so an 8 Ohm speaker is easier to drive than a 4 Ohm, but what is more important is the impedance behaviour.
They like a rather linear impedance curve, so if a speaker has huge impedance spikes, say up to 30 Ohm or more and dipping down to 2 Ohm, like my Martin Logan Prodigy┬┤do, they are not a good match and hard to drive for OTLs
I am also looking into these amps and next to the Piega P10, whci a friend drives with Tenor, I am interested in a German made speaker which has an Air Motion Transformer for the treble (I saw it for the first time at the High end show in Frankfurt/Germany)and it is an 8 Ohm speaker, whose impedance varies between 6 Ohm and 10 Ohm, with a 93 dB sensitivity. So this speaker would be a very easy load for any OTL amp like the Tenor.
I would also look into the von Schweikert DB 100 speakers if I were you. I have discussed this speaker with Mr. von Schweikert and according to him, it would be a wonderful match for any OTL.
Hayden, one thing you need to remember is that the Tenors only output 55 watts into 4 ohms, but 75 watts into 8 ohms. then if that is reduced to 3 ohms you are probably looking at less than 50 watts. so the output power of the amp is affected by the impedence.

then the stability of the amp is affected by the change in impedence since there is no output transformer to regulate and stabilize output.

think of impedence as the size of a garden hose. high impedence is a very thin hose....it doesn't take much water to fill and pressurize the hose and it is easy to keep up the pressure. now consider a very large garden hose which is like low impedence....to keep up the pressure it takes lots of water and power to drive the water. without trying to explain the whole impedence picture; an OTL amp is like a water pump designed to work ideally in a medium size hose but that struggles with the bigger hose. also, this pump has a hard time changing speed of flow if the hose changes size.

as you already know, the Watt/Puppy 6's sound great on the Tenors....they just have limited dynamics and can get hard on the peaks or go into soft clipping if pushed. so a marginal match still works with the Tenors....but why have a marginal match when speakers exist that are a very good match with the Tenors?
Thank you Mike. You used a good analogy to clearly explain three concepts: the difference between high and low impedance; impedance stability and output; and amplifier matching with the correct impedance. The problem is should you match your speakers to your amplifier or the other way around
you will read a good review about tenor and watt/puppy
macth at soundstage(june)
adsal, i did read that review.

Hayden, the choice of which comes first, the chicken (speakers) or the egg (amps) is classic. my 2 cents in this case is that for the closest to the musical event an OTL is the best amplifier and no matter what speakers are used only an OTL offers the level of musical satisfaction that i want, especially the Tenors.

in my experience 3 or 4 different speaker systems that are quite a bit different all sounded their best on the Tenors.