REF75 with Summit-X?

[Clarifixer]

I'm looking at the lovely REF75 and also speaker shopping, with the Logan Martin Summit-X being at the top of my list at this moment.

Has anyone heard this combination or perhaps speculate on whether the ARC can handle these speakers? I heard somewhere that 100 wpc. is about the minimum for the Summit-X, but with its powered woofers, I'm wondering if 75 is "good enough" to drive it in nirvana-like fashion. Not that the REF75 could be called marginal in any area other than brute force!

I listen almost exclusively to chamber and orchestral classical music (Mahler is a favorite) usually in the 80-90 dB range and rarely much over 95 dB in full orchestra climaxes. Sometimes some blues and rock, but at about the same volume.

Listening space is part of a very open arrangement but is essentially a 16-1/2 x 17-1/2 corner area that extends another 15 feet in both directions. Ceiling is unfortunately 8'.

Another option I've thought about is grabbing a pair of REF210 monoblocks off Audiogon for around the same budget point, but that REF75 is just stuck in my mind's eye........

[cmalak]

Clarifixer...I don't think you want to drive these with a tube amp despite being 91dB sensitive and having their woofers driven by onboard 200wpc Class D amps. The speaker's impedance is capacitative, decreasing with increasing energy. So the impedance dips down to 0.8 ohm at 20KHz (so the impedance falls from 4ohm nominal rating at 1KHz and keeps on falling throughout the passband as frequency increases), which makes it a prime candidate for speaker-amp interaction. You want a low impedance, high damping factor SS amp to drive these. Here's an exerpt from Dick Olsher's review from TAS:

Given its 91dB sensitivity, you would think that driving the ’stat panel would be a piece of cake for even low-power tube amplification. I was looking forward to deploying my substantial collection of 30Wpc tube amplifiers in the pursuit of sonic bliss. Unfortunately, that notion went right out the window. The electrostatic panel’s impedance is capacitive in nature and decreases with increasing energy, reaching a minimum of 0.8 ohms at 20 kHz. That makes the Summit a prime candidate for amplifier-speaker interaction. Unless an amp’s source impedance is very low, meaning that its damping factor (DF) is high, it will invariably roll off the treble. The Berning ZH-230 struggled in this respect as did other tube amps. A typical tube amplifier with a source impedance of about 1 ohm is said to have a DF of 8 relative to an 8-ohm load. The same amp would exhibit a DF of less than one driving the electrostatic panel at 20 kHz. One tube amp in particular started rolling off the Summit at 5 kHz and was down 10 dB at 20 kHz. Make no mistake about it: This represents significant adulteration of the tonal balance. The amps that performed best in preserving the Summit’s frequency response were high-DF solid-state (rather than hollow-state) designs, with a minimum DF of 150 relative to 8 ohms. MartinLogan doesn’t recommend any particular amplifier; however, I can. My two favorite amps for the task at hand turned out to be the Electrocompaniet AW180 (DF=1000) and my Ampzilla II (DF=150), refurbished and upgraded to a FET front end by Mike Bettinger, GASAudio.net.

If you want to stick with tube amps, I would find a tube amp with low source impedance (input impedance) and high damping factor, so that you don't have a tonally skewed/altered presentation. Dick Olsher said on one of his tube amps, there was material roll-off at 5KHz and was down 10dB at 20KHz! Talk about a material tonal balance shift - that kind of roll off will sound thin, recessed, and uninvolving/exciting and just plain wrong.

I think with these babies you will want to stick with high powered and high DF SS amps. If that's not your cup of tea than you may want to consider more tube-friendly speakers with a benign load (i.e., at least above 6 ohms and fairly flat without major peaks and valleys in the impedance graph as tube amps don't like to see major shifts in load).

[MPS]

^ Well said.
However if you do prefer using tube amp, I am very happy with my VT200mkII which drives low impedance load with ease. Speakers are ML CLX.

[Myles B. Astor]

Originally Posted by Clarifixer

I'm looking at the lovely REF75 and also speaker shopping, with the Logan Martin Summit-X being at the top of my list at this moment.

Has anyone heard this combination or perhaps speculate on whether the ARC can handle these speakers? I heard somewhere that 100 wpc. is about the minimum for the Summit-X, but with its powered woofers, I'm wondering if 75 is "good enough" to drive it in nirvana-like fashion. Not that the REF75 could be called marginal in any area other than brute force!

I listen almost exclusively to chamber and orchestral classical music (Mahler is a favorite) usually in the 80-90 dB range and rarely much over 95 dB in full orchestra climaxes. Sometimes some blues and rock, but at about the same volume.

Listening space is part of a very open arrangement but is essentially a 16-1/2 x 17-1/2 corner area that extends another 15 feet in both directions. Ceiling is unfortunately 8'.

Another option I've thought about is grabbing a pair of REF210 monoblocks off Audiogon for around the same budget point, but that REF75 is just stuck in my mind's eye........

The ML really begin to sing when you give them some horsepower. 275 watts is great, a kilowatt even better, all things being equal

One thing to be aware of though. Although the Summit-X is self powered, the quality of the main amps is still very important. In short, the amp in the speaker reflects the quality of the main amp. In my experience, while the ART was good in the bass, the Cello was even better--even though the X's are self powered.

[Ritmo]

Clarifixer,

The Ref75 is a wonderful amp. If your heart is set on getting one, I would seriously recommend you listen to the NOLA KO speakers. I listened to this combination at RMAF last year and felt it was terrific.

[Clarifixer]

Funny how life throws a curveball at times. In a conversation with a dealer yesterday, he mentioned he was rotating out the demo REF150 he had been using for speaker and component auditions with about 400 hours on it. It is like new, having been unpacked and put directly into service at the store for a couple of years, with no one messing with it but him. For sale with a full three-year warranty and a very nice price.

I bit.

It may not be as pretty as the REF75 with its VU meters and all, but a very serious component with a bit more potential to drive a heavy load. I think I'll just ponder all the new possibilities for a while.....

[NOLG4EVR]

Originally Posted by Clarifixer

Funny how life throws a curveball at times. In a conversation with a dealer yesterday, he mentioned he was rotating out the demo REF150 he had been using for speaker and component auditions with about 400 hours on it. It is like new, having been unpacked and put directly into service at the store for a couple of years, with no one messing with it but him. For sale with a full three-year warranty and a very nice price.

I bit.

It may not be as pretty as the REF75 with its VU meters and all, but a very serious component with a bit more potential to drive a heavy load. I think I'll just ponder all the new possibilities for a while.....

Good purchase. I have heard the ref 75, ref 150 as well as the ref 250's. All very good amps. I think you will be very happy with the 150. BTW, what pre and speakers are you planning on running with it?

[Ritmo]

Originally Posted by Clarifixer

Funny how life throws a curveball at times. In a conversation with a dealer yesterday, he mentioned he was rotating out the demo REF150 he had been using for speaker and component auditions with about 400 hours on it. It is like new, having been unpacked and put directly into service at the store for a couple of years, with no one messing with it but him. For sale with a full three-year warranty and a very nice price.

I bit.

It may not be as pretty as the REF75 with its VU meters and all, but a very serious component with a bit more potential to drive a heavy load. I think I'll just ponder all the new possibilities for a while.....

Excellent choice - congratulations!

[cmalak]

Clarifixer...if your dealer is open to it, see if he will let you demo the Ref 150s on your Summit Xs before finally pulling the trigger. Better safe than sorry. If it's a good match, than you are home free with an excellent amp. Congrats!

[magoo]

It would also be worth a look at the Martin Logan owners club site, Arc have a good following over there. On paper specs have their place, but so does real world experience.