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SET and planar magnetic speakers

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Could a SET successfully power a planer magnetic transducer not mounted in a box? I am curious about the Bohlender Graebener RD 28.1 or RD 40 sold by Parts Express, whose service and kits I esteem. They are not that sensitive, but they offer a nearly resistive impedence only. They crossover at 150 Hz second order and this could be done easily with two capacitors and a resistor in the input to the driver in the amplifier rather than in the loudspeaker. (The speaker needs a notch filter that ameliorates a peak at 5000 Hz and this would have to be in the speaker itself because the inductor would have to be so large if it were in the amplifier itself that only something like a secondary of a neon sign transformer would do the trick.)
I find the idea attractive because it circumvents cabinets and their problems and the below 150 Hz frequencies can be done by subwoofers and solid state amplifiers. I only use a 45 with a parallel feed output transformer so such speakers might not be sensitive enough even though there are no inductive problems in a planar magnetic transducer.
Has anybody tried this? How did it work? Your opinions will me most appreciated.

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Re: SET and planar magnetic speakers - morricab 07:17:58 02/09/07 (0)
Yes I drove a pair of Apogee Caliper Signatures (with a flat 3-4 ohm impedance) with a pair of Cary CAD572se monoblocks (20 watts). It sounded great overall and played quite loud without obvious problems.
Re: SET and planar magnetic speakers - maki 17:24:21 02/08/07 (4)
Yes, ribbons can sound fantastic driven by SET amps. I often
demo our full range planar ribbon speakers with medium power
tube amps. I was curious if a SET would power our new 4 panel
speaker so I borrowed a pair of deHavilland GM70 SET amps.
WOW! Granted, the GM70s are stout SETs, but we have power
to spare. Our larger speakers have a reasonably flat impedance
curve at about 5.5 to 6 ohms so they are easy on amps. Ribbons
with low dips would certainly be more of a challenge to any amp.
Planar-ribbon speakers and SETs are truly fabulous. Next we
will try a smaller SET, say 20 watts.
- Re: SET and planar magnetic speakers - Barney Vincelette 15:42:13 02/09/07 (0)
  I do not have the most discerning ear, but I compared a 300B to a 2A3 on the same kit speaker that uses two 6" mid ranges and a Raven ribbon and the 2A3 sounded better. The 45 sounded better still. Has anyone heard any more powerful tubes that rival the 45 SET?
  An 833A is an amusing possibility if it would not shatter even the strongest planar magnetic ribbon and it would probably have to be driven by a 211 and that by possibly a 45. But all those stages of amplification would be such a compromise.
  Perhaps the active crossover at 3000Hz to a Raven tweeter is the best way to use the 45. But other ideas that circumvent most of the crossover and cabinet problens are theoretically fascinating if they could do better. It is always advantages combined with disadvantages.
  I very much appreciate reading opinions people have taken the time to share. Thank you.
- Re: SET and planar magnetic speakers - morricab 07:19:58 02/09/07 (2)
  Just out of curiousity, which planar speakers are those? I had good success with a 20 watt SET on my Apogees. Now I am driving a big Acoustat (I mean BIG) with a 30 watt SET from KR audio (the VA350i).
  - Re: SET and planar magnetic speakers - maki 22:19:48 02/10/07 (1)
    The speaker I am referring to is our newest full range planar-ribbon speaker by Analysis Audio called Orion. It's comprised of 4 panels each being 7 feet tall and 28 inches wide. 2 panels are each comprised of a full length ribbon tweeter and a planar bass driver and the other 2 panels have only one large bass driver each. I would include a picture, but I am not sure how to do so here.
    - Re: SET and planar magnetic speakers - morricab 04:34:55 02/12/07 (0)
      Try it with a KR amp if you get the chance and then watch out! You will be shocked with the bass and control from a "little" tube amp.
Why not a hi-eff ribbon? - Kloss 06:03:18 02/08/07 (0)
Founteks neo pro 5i is 102db 1 watt 7 ohms can be used to 1200hz.Mundorf also offers a few hi-eff AMT. Hi-Vi has a few hi-eff ribbons but of these only rt8 2 can handle midrange.
Re: SET and planar magnetic speakers - Spectre1 19:56:47 02/07/07 (0)
I run an Art Audio Jota BXLS High Current version (24watts) amp to drive a pair of ML Summits. Sounds beautiful. THe amp is currently using Emission Labs 520 tubes but I've also used KR Audio 300BKLS in this setup.
I had the opportunity to try a Cary 300SEI amp (16watts) on these speakers and to my surprise they sounded sweet and played at moderate levels. I didn't play it loud though.
I just recieved a Sophia Electric Baby 10 watt amp and will see if the Summits 92db sensitivity will work with this amp.
Keep in mind that this ML model (and the Vantage model) have internal amps to drive the woofers making them literally biamped electrostats. This and the newer panel design helps a great deal to allow them to work with low powered sets.
Otherwise traditional biamping for the woofers is probably the only way that a SET amp will work with an Electrostat. The combo is great if the gear has a good boost of current behind it and doesn't have to drive the woofers.
Re: SET and planar magnetic speakers - cjfrbw 17:47:04 02/07/07 (2)
I have some Apogee Centaur Minors ribbon hybrids (86DB sensitive) crossed over at 80 HZ with a 300b at 8 watts and it gets very loud without breaking up.
A 4 watt 6v6 SET makes nice sound, but breaks up at moderate volume levels.
You could try a 300b or a high power 845 or 805, I doubt that you will get satisfaction from a 2A3 or a 45. 8 watts might be listenable, but 20 watts and above highly desirable.
I run active crossovers with my Apogee Ribbons, the ribbon from 350 to 3500 HZ will operate with a 8 watt 300b with an active crossover, but not optimally. The ribbon by itself is probably 89db efficient. I use a 50 watt Wavac SET, and it seems to do well with that.
I think you are looking at a 845 at least.
Ribbons and SETs do work, however, and sound just great, as long as you respect the limitations.
- Re: SET and planar magnetic speakers - Barney Vincelette 15:31:00 02/08/07 (1)
  Thank you for your advice and experience. I doubt that I would want to give up the pulchritudenous sound of the 45 so I use a Raven tweeter and a pair of 6" dynamic speakers in a cabinet with bi amplification and cross over filters between the 6SN7 mu follower with choke drivers and the 45 grids.
  The idea seems interesting and if I understand correctly, a planar magnetic ribbon can be mounted in a piece of wood in dipole fashion and the width of the wood varies to prevent diffraction an a frequency determined by the distance between the ribbon and the edge of the wood. I recall Dahlquist made a tomb stone shaped speaker that used no box and the thing looked like something out of a science fiction movie. The crossover parts were exposed and in the open and were beautiful to see. But with progress the sound of speakers improved. But that style never returned.
  - Re: SET and planar magnetic speakers - cjfrbw 15:39:01 02/08/07 (0)
    I do use a Korneff 45 with active crossover 18db/octave above 3500. It does seem to convey a lot of the upper midrange/upper benefit of the 45 sound, using Aurum Cantus ribbon tweeters.

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