Speaker Impedance, Tenor OTLs, and Watt Puppies

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.

Hayden,

Comments are spot on. I'm curently evaluating the Tenor 75wi with a pair of SF Amati Homage (4ohm, with a maximum of 7.8 ohms, but a value below 6 ohms in the midrange and below 4 ohms in the bass and high treble -- Stereophile measurements).

Some other things to add into the equation:

1. Voltage output and gain of your source gear if you are going to run direct, or even through a preamp. If the source doesn't have enough gain (i.e. my CJ Premier 15 phono pre) or voltage output, then you tax an amp already at it's edge driving a speaker below 8ohm.

2. Size of listening room and average level of loudness you like. Some listen in the 80-85 db range. Some in the 95 db range and up. This also impacts whether an OTL like the Tenor will "be a good match" for something like the Watt Puppies. (i.e. my listening room effectively is my entire 1300 sq ft open live/work loft, which makes things a little more difficult).

3. Do you already own the Watt Puppies? Sunk cost is an issue, and one that people will react to differently.

The way to describe the "poor match" is taking a speaker rated at 4ohm, and driving it using the 8ohm taps on a "normal", transformer based tube amp design. The 4ohm tap will provide more cohesion throughout the freq range, tighter bass and mid-bass, with more control over the drivers. Going off an 8ohm tap, you will get more "air", "sparkle", and maybe some more detail. Different people prefer different sounds. For instance, some folks with 8ohm speakers will drive them from a 4ohm tap, and some will drive it from an 8ohm tap.

Hope this helps,

Tom H

You must consider the damping factor when matching OTLs with speaker loads. I do not know what the output impedance of the Tenors is, but low output impedance is generally not the strong suit of OTLs. If you get low impedance speakers, or ones that swing low in the bass freq's particularly, then the damping factor of the amp can be seriously compromised. Generally speaking, higher impedance speakers will present a more controllable load for OTLs.