ART 27A driving Quads

[kswanson27]

Anyone have experience with an ART27 A driving Quad ESL63s?

 

[DonH50]

I have no experience, but it seems like a relatively poor match unless you sit close and listen at fairly low levels. Be sure to use the 4-ohm tap/version of the ART27A to drive those Quads.

 

[kswanson27]

I have no experience, but it seems like a relatively poor match unless you sit close and listen at fairly low levels. Be sure to use the 4-ohm tap/version of the ART27A to drive those Quads.

Because of the Quads efficiency, impedenance curve or what?

 

[DonH50]

Because of the Quads efficiency, impedenance curve or what?

They have fairly low sensitivity and widely varying impedance. A low-power amp driving a low-sensitivity speaker means you need to sit fairly close and/or keep the volume low. They have a high impedance peak at low frequency and fall to pretty low impedance at very high frequencies, like most (if not all) ESLs, so a tube amp with high output impedance will exhibit significant variation in output over frequency. That may or may not matter; it is possible the resulting modified frequency response will be more to your liking.

I have used low-power tube amps with insensitive speakers, e.g. a 35 W/ch Eico or Dynaco with Magnepans, but sat fairly close. The Maggies also have pretty flat impedance over frequency. The times I have used a tube amp on ESLs (Acoustat, Beveridge, KLH, Quad, etc. -- but not Sound Labs, have very rarely heard them) I found the highs to be a bit harsh, which surprised me a bit because the lower impedance I expected to decrease the amp's effective output. In some cases, the amp was clipping early, but I did not measure them all and that was long, long ago.

All panels exhibit modes to some degree, though the newer Quads (ESL63 etc.) have a radiator structure that should minimize that effect. (Magnepan uses internal "buttons" to break up panel resonances, even placing them in different spots on each speaker in a pair to prevent the remaining resonances to "double up" in the pair.) A SS amp's lower output impedance, in addition to flattening the frequency response (again, for better or worse), also tends to reduce panel resonances, though I think it helps less in ESLs due to the coupling transformer. For them the SS amp's lower output impedance is the main benefit (plus it is easier and cheaper to get low-distortion high-power SS amps).

That said, some of the best sound I had from my Maggies (and some of the ESLs I was able to hear if not own) was using (larger) tube amps, primarily ARC and CJ models. Not as accurate, but lovely sound.

 

[BWilson]

k Swanson,

I have Quad 988's that have been upgraded by Electrostatic Solutions. I drive them with a 30 year old cj MV50 amp (has been recapped with Mundorf caps) that is approximately 45 watts per channel. My listening room is 20 ft x 24 ft x 18 ft ceiling. I have them four feet from the back wall, about 9 ft apart and 9 1/2 feet from the listening chair. I listen to mostly small group acoustic jazz (think Miles Davis, Coltrane, most ECM label artists, et al). I do not listen at loud levels but I think 40 - 50 watts in a tube amp is probably minimum depending on your room size and type of music. Although I have read reviews by Herb Reichert and others that sing the praises of the Pass Labs 25 watt amp XA25 I think or maybe Int25. Considering the price of the ART, I think you need a longer term loan before committing to buy it. You should get some good answers over on the Conrad-johnson owners forum, if you have not already tried it.
https://www.conradjohnsonowners.com/viewtopic.php?p=25210&hilit=quad+ESL+and+ART+27#p25210

Regards, and let me know what you decide. I want to upgrade my amp, but not sure where to go for an amp.

Alton

 

[Another Johnson]

Be sure to use the 4-ohm tap/version of the ART27A to drive those Quads.

The CJ default is the 4 ohm wiring. There is only one set of “taps.” If you want something else, you have to rewire the transformer to the taps … an inside job.

You can have it done at the factory, or you can take it apart and find the wiring diagram for other loads on the transformer.

Regarding the OPs question, CJ would advise buying the ART 108As. The 27A is for smallish rooms with efficient speakers.

Nevertheless, your ears, your system. You might like it.

Edit: FWIW, the 63s dip to 6.2, so they might sound better wired for 8 Ohms. But 4 or 8 … either will work.

 

[kswanson27]

The CJ default is the 4 ohm wiring. There is only one set of “taps.” If you want something else, you have to rewire the transformer to the taps … an inside job.

You can have it done at the factory, or you can take it apart and find the wiring diagram for other loads on the transformer.

Regarding the OPs question, CJ would advise buying the ART 108As. The 27A is for smallish rooms with efficient speakers.

Nevertheless, your ears, your system. You might like it.

I should add I'm running a pair of Entec 12-F20 subs with the Quads crossed over at 60Hz.

 

[puroagave]

IMHO, 63s need at least 100 wpc. 57s are a different story, the ART27 would be wonderful on those.

 

[DonH50]

The CJ default is the 4 ohm wiring. There is only one set of “taps.” If you want something else, you have to rewire the transformer to the taps … an inside job.

You can have it done at the factory, or you can take it apart and find the wiring diagram for other loads on the transformer.

Yah, that is why I said "tap/version"; probably should have just said "version" but figured a lot of folk might be used to "tap".

 

[DonH50]

IMHO, 63s need at least 100 wpc. 57s are a different story, the ART27 would be wonderful on those.

Hmmm... IIRC they would not take as much power as the 63's, but are even less sensitive, so I would still favor a larger amplifier. No point in going over ~100 W, though, as they would self-protect around that point (again, IIRC).

 

[Another Johnson]

I’ve got to add … if you can arrange it, get an audition of the ART27A in your own proposed system. In the US, this may be easier than in some other locations… but I can’t overstate the value in doing this, even if it costs you something to make it happen.

 

[puroagave]

Hmmm... IIRC they would not take as much power as the 63's, but are even less sensitive, so I would still favor a larger amplifier. No point in going over ~100 W, though, as they would self-protect around that point (again, IIRC).

The 57s were designed for 15 wpc, rebuilt speakers with clamping boards there is no problem going higher. The 63s, to me, sound dead with less than 100 wpc. Again, with updated zenner clamp boards you can safely run 63s harder w/o risk of arcing the panels. I'm on my 6th pair of 57s and owned 2 prs of 63 incl Crosby Mod'd 63 Pros. not my first rodeo re quads.

 

[Dogberry]

Running 2905 speakers (86dB sensitivity) with 40W Quad II/forty amps, and I have no lack of volume!