B&W 804s + Atma-Sphere M60 MkIII.2

Michel,

I think Atma amps are outstanding, from what I read. Zero feedback, OTL, fully balanced. BUT...your MX135 is not fully balanced, I believe, despite having XLR connectors. Make sure you tell Ralph about this.

Buying a used 275 is certainly an option if you want to minimize expenses. Mine is a mk.IV and I have no desire to upgrade to newer ones - besides, I really dislike the green leds under the small tubes the new 275 has.

Subs: big deal! But you have to be willing to invest time in setting them up. 1 sub vs 2, don't know how to quantify the improvement but it's definitely a lot more than 30% in my case. I'm not running stereo subs playing both the same frequencies and same settings. Google Earl Geddes approach for setting up multiple subs. It made a huge difference for me.
I chose Rythmiks for having a reputation of very clean sound, not overly expensive, and have very many variables you can set up in the plate amp. BTW, my two 12" Rythmiks replaced a single REL Storm III. Nice sub, but didn't have the flexibility I wanted. BTW, my Rythmiks are DIY boxes, quite heavy and heavily braced. Each sub weights 100 lbs, for a 56 liter box.
Experimenting with placement of subs is crucial in Geddes approach. Each sub has pa different setting for crossover, slope, volume, phase (a critical feature), and amplifying/damping a certain frequency/bandwidth.
I use a measuremnt mic, an outboard USB card for the mic, and REW software. These are absolutely needed for setup. I wish I could post graphs here. With only the 804 playing you see the lowest frequencies missing as you would expect, plus the room interaction at the lower frequencies. Add one tunned sub and the lowest frequencies are boosted, but I still get huge peaks and valleys in response. Add the second tunned sub (tunned t work with the other sub) and the response gets smoothed significantly.

One of my subs ended up right in between my speakers, while the other one is tugged in a corner.

Sorry I get long winded. I did enjoy learning through this setup process!

Michel,

Never heard the Atma-Sphere, nor know much about it. I can say, though, my 804S driven by my McIntosh MC275 sounds great. It's rated at 75W per channel, and some claim these versions deliver closer to 90W, but clearly not a lot of power. At the time I bought this amp, I also tried these speakers with an MC252 Mc SS amp, and preferred the tubes - to me the added Watts weren't key. Larger B&W indeed need a lot of power. I think the 804S are a great match with tubes. BTW, my pre is also tubed.

Atma-Sphere might chime in here. If they don't, go ahead and post the question to them.

Re sub, I run two Rythmik subs and I'm very pleased with the setup. Setup is tricky, but I learnt a lot in the process. If you go down that road let me know and I can share more on the way I approached it.

Let us know how it goes.

Swampwalker,

Right now I'm running stereo subs, but's only because I have not come around to building the Y connectors to have them both sum-up L&R signals. This is the recommended approach per Earl Geddes, which I'm following with good results.

I really don't want to come across as a specialist, as I'm learning along the way. But if stereo subs sound this good and it's a "deficiency" per Geddes' recipe...I think it should sound even better with dual mono.

Some people on these forums believe we can perceive directionality below 80 Hz. I tend to believe in people like Floyd Toole (author of Sound Reproduction) who say otherwise and I can see they really know their stuff. So if we can't perceive directionality, Geddes approach makes full sense to me as it addresses the interaction with the room, which clearly is the biggest deal under 150 Hz.

Hope this helps!

Michel, thanks for the insight. I still would love tho hear the Tannoys, but it's sounding like it might not be my cup of tea.

Swampwalker, interesting input! Somebody posted the Grand Veenas as becoming distorted at high SPLs, attributed to their direct connection between the amp and mids driver. What he meant by "high SPL", I don't know. Do you find this to be an issue with your speakers?

Michel,

Indeed, I have always heard very good things about customer service from Atmasphere. That is great. Seems is up to you which amp to go with. BTW, I've been very well behaved in not steering you towards the MC275 as I'm quite intrigued about the differences between your Tannoys and your 804S with the 275. Should you go with the 275, please let us know and I'll be bugging you down the road.

One caveat to Frank's suggestion with the Zero: the 275 has an output transformer that apparently does a similar thing to the Zero, and has 16, 8 and 4 ohm taps. In fact, an audio buddy drives his CLS planars with his 275 with no issues whatsoever.

About REL vs Rythmik. Such a difficult question to answer well. The REL is great, but I had only one so the comparison is not fair. It also has a 10" driver vs two 12" drivers in a much larger sealed enclosure each one. For the price of one REL I got two Rythmik kits and built the enclosures pretty stiff and at the ideal size. Bass is much better with the Rythmiks, but maybe with two RELs I would have gotten the same response. Yet the RELs don't have as much setup flexibility as the Rythmiks. Rythmiks are also servo-controlled, and indeed the bass sounds very controlled.

As of now I'm partial to the Rythmiks + spending a fair amount of time setting them up.

Swampwalker,

I wasn't aware the Supremas had passive subs. There is still an argument for adding independent subs: a) the more bass sources in the room, the flatter the bass response (again, per Earl Geddes); b) the optimal bass drive placement is not necessarily the best speaker placement.

BTW, what do you drive your Supremas with? I've been toying with the idea of Grand Veenas with my MC275. Upgrading speakers is not really my next step, but when I day-dream I think about speakers. My speakers are the components that have been with me the longest.

Michel, and Franks,

I apologize as it seems my post was not clearly written. I was not insinuating Franks was steering Michel in any direction whatsoever. Didn't mean to.

The comment about steering someone and being well behaved was a way of making fun of myself, as I was being objective in answering questions, but down deep I was also interested in having comments from someone who could compare the sound differences between a Canterbury and an 804. I know they are in different leagues, but I understand their sound signature is different and I would benefit from some input. Logistics make it impossible for me to audition a Canterbury. Along the lines of the post above, testimony of my sporadic day-dreaming with speakers.

Maybe I should stick to speaking about the subs? :-)