Fidelity Research FR-64 vs. FR-54

I am a bit embarrassed and apologetic to the others as regards this exchange of insults in which I have participated. Fleib, your tone is no surprise to me; cut back on the coffee. Your level of certainty based on no data is also not a surprise. Raul, let’s just get one thing straight, if nothing else: you have never heard my Sound Lab speakers or any Sound Lab speakers that have been dramatically altered as have mine. My speakers have essentially no crossover, whereas the OEM Sound Lab speakers have an RC network to produce a high pass filter. The filter causes a major impedance dip at midrange frequencies. Furthermore, the resistor in the RC network robs amplifier power (Fleib). This robs the speaker of dynamics (Fleib), even when driven by a solid state behemoth, and really kills it with tube amplification. Please grant me this one thing, as I am willing to grant you that I have not heard your specially prepared and set up ADC speakers. If you want more info on the Sound Lab mod, we wrote about it on the Sound Lab Owners Group website. Dr. West modified his production speakers after thinking about what we had done, and why we did it, although he did not take our ideas as far as we did. ("We" is a guy in Australia and me, and then several other SL owners.) I found Dr. West to be a very fine gentleman. By the way, I would never use a transformer-coupled tube amplifier to drive ESLs. I use OTL tube amplifiers only, and my amplifiers are also one of a kind. I think when Raul dismisses tube amplification, he is really thinking about the imperfections of audio output transformers. My whole system upstream from the ESL has two capacitors in the signal path, one is 0.1uF and the other is 0.22uF (excluding the RIAA network of course). Both caps are teflon film and foil (VCap CuTf). Anyone who lives in my area is more than welcome to stop by for a listen, except Fleib.

Neither of us probably has any idea what the other is listening to. But, of course, I have two separate audio systems. The other one is based on a Beveridge 2SW with transmission line woofer below 80 Hz. The Beveridge is a direct-drive type of ESL in which the back wave is completely attenuated and the output from the front of the panel is refracted by a wave guide. NO audio step up transformer, no crossover above 80 Hz. (At 80 Hz, I use an active crossover with premium parts.) The Beveridge is quite dynamic (Fleib). Not the technicolor dynamics of a typical horn speaker, but definitely fast. The input and drive sections of the Beveridge direct-drive amplifier are solid state. Tubes are required in the output stage to achieve the +/-1600V needed to direct-drive the panels. (The FR64S is in this system.)

I promise that this is my last retaliatory post on this thread, and I do apologize to others for the sturm und drang. Now I think I will relax and enjoy the music.

Great post Lew. You may likely already know this, but Roger Modjeski, the designer of the direct-coupled amp used in the Beveridge, is now making his own direct-coupled ESL at Music Reference, with a sub for the bottom two octaves. I'm dying to hear it!

bdp, Inside the chassis of each of my Beveridge amplifiers is the inscription, done in magic marker: "RM 1979".  Knowing that Modjeski collaborated with Harold Beveridge back then, I have always assumed that he is "RM".  With the help of an EE who owns a pair of Model 2 speakers, I/we have made quite a few improvements to the circuit, but there is only so much you can do, because the input stage is amazingly complex to begin with and for good reasons.  He usually sends me long and detailed email instructions, and I print them out to have them at hand before doing anything new or trouble-shooting.  I zapped my finger-tip once with 1600V; you don't forget that experience.  When the speaker is fully assembled, the panels sit directly on top of the amplifier providing a direct connection between the two. The amplifier section effectively is the base of the speaker, for each channel. No loose speaker wires allowed.  I bought a copy of the schematic from RM, a few years ago when I first acquired the Bevs.

There's at least one company (in Europe) that markets a ESL direct-drive amplifier which they claim can drive the Sound Labs, which is no mean feat, since the SLs require at least 5kV on each stator (and no one outside of the SL factory really knows exactly what the voltage needs to be).  Ralph Karsten says he can make one, too. I am tempted. Maybe in my idle retirement years I will try it.

Dear @thekong :  """  Makes no sense to me that you ask for some tests in my audio system when I have to prove you or any one else nothing at all.  """

I told you ( and every one. ) those because what I'm doing in this thread was and is only to share my first hand experiences, not to convince any one of something.

I repeat, only sharing my experiences as always did and do.

Regards and enjoy the music,
R.

Dear @lewm : """  you have never heard my Sound Lab speakers or any Sound Lab speakers that have been dramatically altered as have mine... """

Sorry but that is not the main subject through my posts here but only a part of. I think you are missing the whole and main subject.

Anyway, you already know ( because I posted over the forum more than 3-4 times. ) that the only ESL speakers I could live with could be the Soundlabs. As you know a close friend of mine owns the top of the line here in México city an he received as 3 months ago  his originals speakers that he send it for an up-date and he made it some tweacks on it but I'm not sure exactly what he did it and is not this the main subject.
I explain all those for you be aware that I know very well Soundlabs as my friends's modified ones. No, not exactly the same you own but it's not so important as you think.

There are several critical issues that I touched in my posts in this thread and the more important relationed with your main system are:

- first that the analog and/or digital signal pass through several tubes when one tube destroy the audio signal integrity in higher way than a bipolar transitor several ones/tubes is something catastrofic for say the least.

- that main system have not an adequated system bass management and with out it any single system is totally incomplete. Home audio MUSIC belongs two both frequency extremes and very special on that accurate " bass management ".

OTL designs can't help becaus etubes are there. All your ESL modifications can't honor MUSIC till those tubes disappears from the audio signal and till you have that accurate/adequate system bass management.

There are other issues but is useless to continue speaking about till things changes in those both critical subjects that are indisputable/incontrovertible.

Regards and enjoy the music,
R.