Thoughts on the Krell S-550i?

[SteveK]

I had owned S300i for my office system. It drove bookshelf speakers well and I loved that Krell sound. However, when I hooked it up to Strads, it overheated and shut off in about 15-20 minutes. It was at moderate volume. My dealer let me try a different unit and same problem repeatedely happened. I understand it is probably not designed to be used for bigger speakers, but it is supposed to double up to 300 WPC at 4 ohms. I guess specs do not tell the whole story. I am wondering if S550i would have better luck with heat tolerance.

[Shaffer]

Originally Posted by SteveK

I had owned S300i for my office system. It drove bookshelf speakers well and I loved that Krell sound. However, when I hooked it up to Strads, it overheated and shut off in about 15-20 minutes. It was at moderate volume. My dealer let me try a different unit and same problem repeatedely happened. I understand it is probably not designed to be used for bigger speakers, but it is supposed to double up to 300 WPC at 4 ohms. I guess specs do not tell the whole story. I am wondering if S550i would have better luck with heat tolerance.

The issue may have more to do with a reactive load, rather than the size of the speaker. My S300i drives a pair of Dunlavy SCIV at full tilt without a sign of strain.



[not my pic]

[SteveK]

That's good to know. I do not fully understand the concept of "reactive load" but I am assuming my speaker is "harder to drive" at least for S300i. Can that mean S550i may have the same issue with my Strads?

I have used Krell 2250e and currently trying 302e. They are wonderful amplifiers and makes my Strads sing. I am eventually going with different pre/amp, but I also do like Krell sound. I wanted to get a S550i as a cheaper "alternate" that I can switch to should I crave for that tight controlled Krell sound. But I don't want it shutting off after 20 minutes. Thank you in advance.

[Shaffer]

Hi, Steve. I have not heard the S550i. Its test results show it to be an extremely powerful amplifier - much more so than the S300i - that's capable of throwing a lot of juice into lower/more reactive loads. Intuitively speaking, it sounds like it's something for you to seriously consider. Good luck.

[Elberoth]

Originally Posted by SteveK

I had owned S300i for my office system. It drove bookshelf speakers well and I loved that Krell sound. However, when I hooked it up to Strads, it overheated and shut off in about 15-20 minutes. It was at moderate volume. My dealer let me try a different unit and same problem repeatedely happened. I understand it is probably not designed to be used for bigger speakers, but it is supposed to double up to 300 WPC at 4 ohms. I guess specs do not tell the whole story. I am wondering if S550i would have better luck with heat tolerance.

That is surprising and only shows how difficoult to drive the Strads really are (I've heard that already from multiple sources).

When I tried the S300i in my system, it drove my Sashas, which are also a difficoult load (1.8 Ohm minimum + some tough phase angles), without a problem.

And as Shaffer have said - the new S550i looks to be far more powerful.

[SteveK]

I guess that means high efficiency doesn't mean easy to drive. For some reason, I thought Strads would be easier to drive with 92db rating. As I posted on the 302e thread, 302e also gets very hot after half an hour or so of listening. I also have Mcintosh 601's on Strads and they get lukewarm at most even after prolonged listening. Hard to predict...

[Elberoth]

Originally Posted by SteveK

As I posted on the 302e thread, 302e also gets very hot after half an hour or so of listening. I also have Mcintosh 601's on Strads and they get lukewarm at most even after prolonged listening. Hard to predict...

That depends on the biasing of the amp. Amps biased heavily into Class A dissapate more heat. That is entirely normal.

[Shaffer]

Originally Posted by SteveK

I guess that means high efficiency doesn't mean easy to drive. For some reason, I thought Strads would be easier to drive with 92db rating. As I posted on the 302e thread, 302e also gets very hot after half an hour or so of listening. I also have Mcintosh 601's on Strads and they get lukewarm at most even after prolonged listening. Hard to predict...

Actually, high-efficiency/sensitivity does mean easy to drive, for the most part. The Strads specify 92dB, but what does that actually mean? As an example, 92dB at 8 Ohms is 89dB at 4 Ohms and so on. Too, in order to achieve that target, a 8 Ohm load needs 1w of power, but a 4 Ohm load needs 2 watts. You get the idea. Then there's the phase angle to consider, as well as the overall design of the speaker, including the way it behaves as its port unloads. It's complicated. Specs are in place to sell products. In a greater scheme of things they're meaningless.

This being said, the solution is right there in front of you; buy a bigger, more powerful Krell.

[bigblue]

As the curious hifi enthusiast I am I just had to try the S-550i out when my dealer had a demo sample in the shop. They are pretty rare so this was an opportunity not to be missed. My primary interest was to get a grip on how it performed - not to get rid of my integrated Audio Research DSI200.



The physical footprint of the two machines are almost identical but the Krell is almost twice as heavy.

It's hard to be completely objective when doing such a comparison. I have already heard several Krell-based set ups and thereby formed an opinion of their capabilities and "signature". One of these preconceptions is that the bass tends to be something special. I therefore initiated the listening session with Kari Bremnes song Søvnjengersken containing a solo with big drums that gets lots of whipping. It's not long before my premonitions come true. The Krell got the speakers to stand at attention. With the Krell the drums membrane are set in motion and stopped by with an outstanding accuracy. It feels like my Sonus Faber stands on tiptoe through the whole song. In addition to the bass is rock solid, I also get the impression that the base is some what attenuated to give a little extra UMF.



A classic album for me when evaluating gear is Joe Sample and Randy Craford's album No Regrets. The disc contains many fine acoustic arrangements where you hear a richness in the instruments. Whatever I play everything remains effortless (no wonder with those power resources). The depth of the presentation is in line of what my ARC performs - ie in line with the speakers. The S-550i plays with a freshness that shines through in everything I give it. The machine extends far both in the deepest as well as the highest notes, without being edgy. Compared with Audio Research it gave a more neutral (less rich) presentation. DSI200 is also a solid state machine but you can hear that it comes from a manufacturer that has its roots in the tube world, which gives the DSI200 a combination of properties I have come to love.



S-550i is cool machine that is absolutely full of energy, and in addition, it can play with finesse. I played them for a few days side by side. First with short A / B shifts to evaluate the differences. And then further gigs to "forget" the details and instead focus on the big picture and feel what that was most enjoyable. And there the Audio Research won for me. I felt an intimacy, a personality in the experience that I can not defend myself from. As always it's all about compromises and sure, the ARC is not as transparent and neutral as Krell, but I simply became more engaged in the music through the Audio Research.
This is, however, two great machines so in the end it's all about taste.

[partrician]

The KRELL S-300i and the S-550i for the money definitely big time winners.