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Please let's start a list of speakers that work well with an OTL amp from 30 - 60 watts. Let's keep the price below 20k for argument sake.
Thank you.
Follow Ups:
Wondering how an OTL would perform on my fulton p12's
Lawrence
Fidelity_Forward
I use Magnepan 20.1 with the huge GRAAF GM200 OTL/OCL amp,
sounds fantastic , no problem with the match. The sound is incredible real.
Ups, I missed that only up to 60W was the desired power. The GRAAF GM200
can easily put 200W into 8 and still 134W into 4 Ohm load.
I've been using these with an older pair of M60's with great effect. The bass drivers are "pro audio" speakers that simply don't compress at high volume. If you like head-banger rock at realistic sound levels, these could be your speakers. Amazing lack of distortion at hearing-loss threatening levels.
They sound pretty darn good at normal listening levels too. Duke's stuff is great with Atma-Sphere's.
Most of my listening is with Planars, so perhaps I attribute extra credit to a speaker that can move so much air. But these are impressive!
"Knowing what you don't know is, in a sense, omniscience"
Aside from decent efficiency and an impedance curve that doesn't dip too low, a fairly smooth impedance curve is desirable. Assuming the speakers were voiced on solid state amps (most are), be aware that an OTL amp will be a bit louder where the impedance is high, and a bit softer where the impedance is low.This is NOT a "fault" of the OTL amp - we could point out that, relative to tube amps in general, a solid state amp is louder where the impedance curve dips, and softer where the impedance curve is high.
(If you ever read where someone tried an OTL amp and their speakers sounded worse, the culprit was a poor job of matching speakers with amp.)
Okay, on to the thing you might want to watch for: A frequency response curve that zigs where the impedance curve zags. In such a case, an OTL amp will probably result in a more natural-sounding frequency response (in addition to its other benefits).
The Silverline Audio Bolero is an example of such a speaker, note how its frequency response curve zigs (Chart 1) where its impedance curve zags (Chart 4) at the link below. Even though this speaker's impedance curve goes a bit lower than we'd like, I'd expect it to still work well with most OTL amps.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Edits: 08/23/15
And the rest of us were remiss in not mentioning (much) the Audiokinesis speakers made by Duke. (The brand name is in Ralph's list below.) Really, some of the best speakers around for our amplifiers (or any amplifier, really).
The more benign the electrical load, the easier for an OTL to drive.
the musicians are in the room with you...
(Musical Fidelity DAC, Transcendent Grounded Grid pre, Transcendent T8-LN, Reference 3A DeCapoI speakers.
$50K sound for $5K spent...
I much prefer the 'you are where they were' effect.
I have owned somewhat bigger 'time and phase coherent' 8" 2-ways since the 1980s in quiet low-diffraction enclosures.
Hard to turn away from.
No Low-pass and an odd order HP xover.
Warmest
Tim Bailey
Skeptical Measurer & Audio Scrounger
Haven't heard a pair in years, but they were always excellent.
In addition to my Odeon horns, I have a pair of Ref 3a Master Control MMC...a more upscale predecessor of the MM de Capo. Same complement though of crossoverless carbon fiber woofer and first order, single cap xover to a (now) Be tweeter. Not quite as alive as my horns but far more than any other monitor I have heard, with the exception of the small Odeon Orfeo bookshelf speaker(I had that too and it was excellent).
I also have a pair of the floorstanding Ref 3a L'Integrale. Also a very good speaker.
I sold my Pro-Ac speakers immediately prior to buying the DeCapos. They are very different sounding although both very musical. I would often listen to either pair of speakers for 8+ hours any weekend day without risk of listener fatigue.
The ProAcs however require a _lot_ of power to go low and although I also have an Hsu sub in the system, the "integration" was never quite what I hoped. So I sold the ProAcs and bought the DeCapos.
Anyway, both are great speakers and I could live happily ever after with either.
what speakers are you using now?
ken
I use Sound Lab ESLs with my Atma-sphere amplifiers, but I am only happy after major modifications to the Sound Lab crossover network that resulted in increasing the impedance by quite a bit and increasing efficiency, likewise.
What kind of Soundlab requires a crossover? I thought they were full-range like my Acoustats were.
Interestingly, I demoed my Ref 3as with a Graaf GM20 OTL...fantastic. I use SET amps at home for the moment but I might try a transcendent SE OTL. (their new ones are 4 watts stereo and 12 watts mono).
Actually, many Acoustats have a crossover used in exactly the same way as is the one used in the full-range Sound Lab speakers: Inside the "backplate" you will find two audio step-up transformers, one for the bass and one for the treble. There is a first-order crossover network that divides the incoming frequencies to feed the two transformers. Sound Lab actually copied this approach from Acoustat. In the SL speakers, the low pass filter is an inductor, in series with the input and the primary of the bass transformer. The hi-pass filter is an RC network, with C in series and R in parallel with the primaries of the treble transformer. On the secondary side, the two transformers are tied together and do drive the panel as if it were a one-way speaker. Very small value capacitors are used in series to isolate the secondaries of the treble transformer from those of the bass transformer.
That is true for the older 1+1 and 2+2 etc. The spectras did something different and had a High voltage crossover that was using resistors and the native panel capacitance as near as I could tell. Two transformers but of equal size...not like the 1+1s I had. In all I had three pairs of Acoustats (1+1, Spectra 2200 and Spectra 4400)...all at the same time! The 2200s were the best sounding overall...very transparent but full sound. The 1+1 were a bit leaner but slightly more opaque sounding and the 4400s were for some reason I could never figure out slightly dark and a bit muffled sounding...made amazing subwoofers though, which is ultimately how I used them.
By this do you mean that the filtering was done after the secondaries of the step-up? Yes, I see how that could be done with the proper very high voltage rated resistors, in theory.
And I use Stax F83's with Futterman OTL3's. These speakers are incredibly inefficient, but they have a very high impedance in the midrange (160 ohms). Strangely for ELS's, the impedance drops to about 4 ohms at low frequencies as well as high, and the amps struggled with bass. Adding a pair of subwoofers helped enormously, and I now get plenty of dynamics as well as greatness sweetness in midrange and treble.
The speakers are pretty much unavailable now, unfortunately.
F83s are great! I had F81s and wish I had kept them...so transparent. We drove them best with a big Push/pull EL34 based amp but I can imagine an OTL being just jaw dropping with them.
Have you seen the company in Holland that makes a Electrostatic direct drive amp that will also work with STAX speakers?
http://twinstaticaudio.com/elektronica/twin-otl/
monoblocks with 4600V swing.
Thanks very much. I am indeed very happy with the sound of my OTL-STAX combo.
I have a letter from Harvey Rosenberg himself saying it was an ideal combination; for a while he was thinking of marketing a special amplifier to go with these speakers. I think Roger Modjeski is also offering a direct drive option for this and several other ESL;s. I'm happy as is, however.
I'm using a set of B&W 800D's with the Spelz autoformers driven with a rebuilt NYAL OTL4.
Not missing a note...
Wow. Isn't the OTL4 the triode version built for the Japanese market? And doesn't the impedance of the B&W's go down pretty low---3 ohms or so. It is very surprising that such a combination would work. By the way, before I got my Stax ESL's, I had some B&W DM2's.
I'm using a pr of Acoustic Zen Crescendos with Auto Transformers and Atmasphere Novocrons with good success. Yes I could use more power but for 95% of the music it's just wonderful!
Spendor BC-1
Dynaco A25
KLH 9
DeVore Fidelity O 93/96
Happy Listening
devore 8's work very nicely, only 90db efficient but plays at 7 ohms and over all the way.
Tom Collins
Most of the larger Tannoys
Audiokinesis
Classic Audio Loudspeakers
most horns
Quad ESL 57 and ESL 63
Most single-driver loudspeakers like Lowther or PHY; will in many cases require a speaker protection fuse as these speakers don't handle much power
Rogers LS35A (35 watt limit)
High Emotion Audio (Pyra Bella 6 and Bella Twin)
Merlin (we have more M-60 customers using Merlin than any other speaker)
Magnaplanar 1.7s and the like work quite well with M-60s if you have a set of ZEROs
Tonian Labs
Surreal Audio
There are a bunch of others I'm not remembering off the top of my head...
To Ralph's list, I might add the Martin-Logan CLS I (the original version). M-L screwed it up totally in version II and later. But the first version is fantastic with either Futtermans or Atma-spheres.
And dare I mention once again, modified Sound Labs or the very latest Sound Labs that use the latest toroidal treble transformer.
Vintage Jantzen (sp?) ESLs work fine, too. (They are basically the same as a KLH9.)
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