Letters • February 2015

Buying replacement drivers

February 11, 2015


I have a pair of Audioplan Kontrast III SI speakers, and I know that you have had them before as well. I have had them for many years now and I never wanted for anything else. Recently, I accidentally blew one of the midrange drivers, so I'm looking for a replacement. I thought I better check with Audioplan, but their replies have been erratic. I was wondering if I can just buy the Audax drivers from other suppliers. I was told by Thomas Kuhn of Audioplan that the drivers are slightly modified to their specs, but I doubt that very much. Are you able to advise me what I should do? Wait for Audioplan or just buy them from a third-party supplier? By the way, Audioplan quoted me twice as much as the third-party vendor.

Ng Chee Kia

The Kontrast III SI is a great speaker that works particularly well in smaller rooms, and it is worth ensuring that you keep it in the best possible condition. The idea of manufacturers specifying driver modifications is widely misunderstood. The assumption tends to be that such a modification would be to the cone or some other physical parameter/part of the driver. This is occasionally so, but much more often the modification is designed specifically to affect the electrical or mechanical performance of the driver (its fundamental resonance, Q, impedance, bandwidth or sensitivity). This is done so that the drivers dovetail more accurately/easily with the system requirements established by the crossover, enclosed air volume and bass loading. In other words, the thing it impacts directly is the integration of the loudspeaker as a whole, its ability to sound like a single, seamless whole -- the very thing that makes the Kontrast III SI such a special speaker. Also consider that Audioplan buy their modified drivers in quite small numbers compared to general production, a factor which will make them considerably more expensive, helping explain the price that you have been quoted.

I would strongly recommend that you purchase the driver from Audioplan and maintain the speaker in its original form. Buying a cheap unit that looks the same might seem like a bargain, but it is a false economy as it will seriously undermine the performance of not just the speaker you fit it to but the pair matching as well.

One word of caution: Audioplan use their own, very heavy speaker cable internally. If you have any doubts about your soldering skills, have a qualified technician fit the driver, as clumsy soldering can easily overheat and damage or destroy the voice coil on your nice new (and expensive) drive unit. -Roy Gregory

From Sophia 2 to Sasha W/P?

February 5, 2015


Where do I go from the Wilson Sophia 2? I just love these speakers! Can I go to the first Sasha W/P and get that natural tonal balance, or will it get a bit tipped up? Sounds like they are certainly more dynamic, but maybe more present in the upper octaves too. My room is 17' x 21'.

Bill Barotti

The Wilson Sasha W/P will be an upgrade for you, as it's a later and greater Wilson speaker from your Sophia 2s. However, the better choice, in my opinion, would be the Sasha W/P Series 2, and here's why: It's a much more refined version of the speaker with two of the design cornerstones of Wilson Audio's latest speakers. It uses Wilson Audio's Convergent Synergy silk-dome tweeter, and there are now 20 group-delay positions for the midrange/tweeter module, instead of four with the original Sasha, improving the speaker's time-domain performance. Yes, you'll have to pay more for the newest Sasha than a used pair of the original speakers, but you'll also have these speakers much longer, because you'll be buying Wilson Audio's latest technology, and that may save you money in the long run. Your room is about perfect for them too. -Marc Mickelson

Cooler amp for CS3.7?

February 1, 2015


You have answered a couple of questions for me in the past to great effect, so I hope you don’t mind another one. This one concerns the running temperature of the my amp. My current amp is an Audio Research Reference 150 (into Thiel CS3.7s). I previously had a Reference 110, but I have found that the KT120s in the '150 run quite a bit hotter than the Reference 110 ever did. My room (5m long x 4m wide x 3m high) gets quite warm now (in a New Zealand summer, unpleasantly so). But I do love what the Referece 150 brings to the party.

I’m wondering if the Reference 75 (with half the number of output tubes) would run any cooler and therefore would solve my issues. I listen at moderate volumes to a diet of jazz and classical music. No ear-bleeding levels (domestic harmony dictates).This then raises another question -- would the Reference 75 have enough current to drive the '3.7’s? I can get air conditioning installed in the room, but I was wondering if the Reference 75 is a viable alternative with little sonic difference.

Kevin O’Connor

You pretty much answer your own question. Half the tubes will mean much less heat, as they, along with the fans that cool them, are the major sources of heat from your Reference 150. An important question, as you note, is if half the power and reduced current -- 75Wpc for the Reference 75 versus 150Wpc for the Reference 150 -- will drive your Thiel speakers to acceptable levels. There is an answer for that too: Just drop a match quad of KT150s into the Reference 75, as Carl Marchisotto of Nola has done, and you'll get 20% more power -- 90Wpc. You might also get a little extra heat, as the KT150s are larger tubes, but it will be negligible compared to the heat you're getting from your Reference 150 now. You might also gain some sonic purity, as the Reference 75 has fewer parts than the Reference 150, and the KT150s seem to add some magic to the sound of the amp. I have to say that the Reference 75 with KT150s intrigues me for this reason.

By the way, your Thiel CS3.7 speakers are likely the last of the breed. While the Thiel name continues, the pillars of Jim Thiel's design philosophy -- first-order crossovers, time and phase alignment -- are no more under the Thiel name. Enjoy your speakers. We will likely never see their equal, especially with Jim Thiel-designed drivers. -Marc Mickelson


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