Speaker Impedance, Tenor OTLs, and Watt Puppies

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.

Mikelavigne, you state: "..this case is that for the closest to the musical event an OTL is the best amplifier... "
I would totally agree with you, was it not for the Kron Double Kronzilla SET amps. I have heard from very two reliable people, that the Double Kronzilla Monoblocks ($35000,00) are even better than the Tenor. And if you read here how the tubes are made (it takes about 120 man hours for one tube and Bohemian artisan glass blowers make the glass shell) I tend to believe these audiophiles. Read here if you like, it is in English
http://www.blackforestaudio.de/KR_Verstarker/Presse_uber_KR/presse_uber_kr.html
I was almost 100% set on Tenor amps, but since I heard of the Double Kronzilla and an audiophile using two pairs to drive his ML Prodigy, I am going to audition this set up first, before I will decide which amps to buy. He and another auduiophile who knows both amps as well, the Tenor and the Kronzilla told me that the Kronzilla will beat the Tenor by quite a margin, when it comes to reproducing music life like.
Had you ever had a chance to audition Kronzilla amps, or have you heard from people about these amps? As you know I always value your opinion.

Tekunda, i refuse, on general principle, to buy anything called "Double Kronzilla".....the name is just too "out there". i couldn't brag all over the web on my great "Double Kronzillas".....the name "Tenor" sounds much more classy and dignified.

i, of course, am joking....eventually i will hear a better amp than the Tenor 75Wp....could be the Double Kronzilla....heck, some people prefer the Lamm ML2. my opinion is that ON THE PROPER SPEAKER, the best OTL can't be bettered.....and at this moment, the best OTL to my ears is the Tenor.

maybe out there is someone who has heard the Double Kronzilla (could they have come up with a sillier name?) and the Tenor on speakers correct for the Tenor, and they could share with us their opinion.

one last point, the Prodigy is an electrostat that is not OTL friendly. it would be the last speaker to compare OTL speakers on. the Prodigy is 4 ohm and drops to one ohm. any conclusions reached on the Prodigy regarding the Tenor are not meaningful to me. also, even though the Prodigy is an excellent speaker (i know you own them), the dis-similar driver designs limit the potential coherence of this hybrid design, and render meaningless the Tenor's top to bottom excellence. with the Prodigy you need horsepower, and lots of it. don't get me wrong, i like the performance of the Prodigy, it has earned it's awards. but find an OTL-friendly speaker to compare the Tenor and the Double Kronzilla.

Mikelavigne, I agree, the name Kronzilla is silly at the first look, but what else can you name your products if your last name is Dr. Kron and you design the biggest, baddest audio tubes in the world? I have not yet seen a Kronzilla tube in real life, but I was told it is monstrously tall. So Gonzilla-Kronzilla, its not toooo far fetched.
I know that the Prodigy is not a good match for the Tenor at all and the guy in Germany has auditioned the Tenors on different speakers (if I am not mistaken on a new desgin called the Ascendo, www.ascendo.de)
But you are right, there will always be something better eventually. I was only intrigued by the idea of Bohemian artisan glass blowers and 120 man hours to build one tube.
So for me, it is more a piece of art and once Dr. Kron, who is not a young man anymore, will die, his designs might die with him.
My brother, whom I help to build a system, might indeed buy the Ascendo speakers with a apir of DoubleKronzilla
(he opted for Tenor and Piega at first, but he now could get an good deal on the Kronzilla and since the Ascendo are very OTL and SET friendly speakers, 8 Ohm, between 6 and 10 Ohm impedance swings and 91dB sensitivity, it would be a good match to test the Tenors.
The problem is only what to do with the pair of amps, which looses the audition. It is kind of tough to sell these kind of amps on the used market.
Anyway, I just bought two Wolcott amps for my Prodigy. That made a huge improvement. Especially the soundstage and transperency has greatly improved now.
So now I have time to look into analogue stuff, since my system is now at a point, where I would benefit from a nice turntable.