By all accounts, a pair of 7b-st's is a better option than a pair of bridged 4b-st's (if, for no other reason, the fact that the 7's are single purpose monoblocks and the 4's are designed as stereo amps that can pull double-duty as monoblocks means that there is redundant or unnecessary circuitry in the 4's). Personall, however, I got a 4b-st because it fit into my budget at the time and I knew I could bridge it and get another one later on if and when it made sense to do so. Hence, it seems like the old incremental / convenience v. (maybe unnecessary) purity of design question. I can't say whether the 7's really do sound any better than a pair of 4's, but the convenience of being able to purchase and upgrade incrementally won out for me. That said, I have found the single 4b-st to be more than adequate for my use and am no longer even considering getting another one. I do like Bryston, though, so I would say that it hardly seems like you can go wrong either way...
Mezmo, what speakers are you running? And just to clarify, I wouldn't actually be bridging the 4B-ST's but rather running one channel for the LF post on the Nautilus and the other channel for the HF post on the Nautilus. I would then do the same thing with the other amp/speaker. I'm just trying to determine if it's better to run 250 watts to each LF and HF post or to just run 500watts and run jumpers or bi-wiring.
Although if I did go the 4B-ST route, I may buy a single one at first. That's a good idea.
I have been considering the same thing. I recently purchased the N802s and have a 250W amp which drives them pretty well, but after some discussions with my dealer I think it would be better to go with the 500W power rather than biamping dual 250W. I think the bass would benefit more from something more than 250W. Besides that, I am using the XLR connections, and my preamp doesn't have dual XLR outputs, so I'd have to get a custom Y adapter made which is also a concern - I'm not sure if that would degrade the quality of my cable connection or not - and it does change the input/output impedance between the preamp and power amp.
As Mezmo mentioned, its better to go with the 7BST or 14BST since they are designed for that power. I think in general bridging an amp raises its distortion numbers a bit so the monoblock design would be better. If you have the money, then I think your choice should be getting either the 7BST or 14BST. I think I would lean more toward the separate 7BST monoblocks, but there probably isn't much or any difference between the two 7's or one 14 - six of one or half dozen of the other...
Mezmo's second response seems on the mark. My Bryston 4b more than adequately drives my Infinity Beta Woofer columns at very high volumes and without any hint of breakup (I use a 3B for the mid/high panels). Can't imaging needing more power. So, unless you have clear evidence that your Nautilus is unusually power/current hungry, I'd go the way suggested by others and BEGIN with a single 4B to see is you need more. In my (and P. Actzel's) view, bryston is hands-down the best electronic value currently available...not even a runner up waiting nearby. Build, circuitry, and sound quality every bit as good as Krell, Levinson, or you name it but at a price that's sane.
Mcoker, I have owned my B & W N802's for about a year. I have had various amps in my home as demo units. I am currently running Krell FPB 200c to them. That amp does a respectable job, but is not enough in the long run. I considered the Bryston 4b ST's and a pair of 7b ST's. I emailed Bryston and they told me that the 7b ST's betters the 4b ST's in more ways that just power. They present a better sound stage and are definitely better than running two 4b ST's bridged mono. They concurred that you give up sound quality when you bridge the 4b ST's even though you get more power. Having tried several amps with the 802's I believe the more power the better. My goal is to eventually biamp the 802's using the Krell FPB 200c for the highs and a FPB 300c for the lows.
Bwyoung is on the right track: I owned a pair of 4B-ST's and loved them ... until I heard my system with the 7B-ST's. The trade-up was a no-brainer for me since I enjoy a well defined bottom end and my speakers are tough to drive. Overall, the sound stage and "live" experience was better with the 7B's so I would forgo the bi-amping in favor of the better amps. Hope that helps.
This seems to be a popular question, as I'm addressing the same issue and considering the same alternatives.
My conclusion is the 7B-ST, rather than the paired 4B-ST. B&W told me straight that my original choice: B&K 250wpc monoblocks, would be a respectable solution at modest listening levels. The B&K monoblocks are built to handle peak dynamic loads. However, that the next step would be to provide robust power to the LF: The speaker's impedance profile changes driver by driver, HF --> LF. My solution is then, the 7B-ST with an internal bi-wire: probably XLO.
Bwyoung, thanks for the info on what Bryston said. But I do have a question. If the overall consensus, including yours, is to go with one larger amp, such as the two 7B-ST's/single 14B-ST, compared to running dual 4B-ST's and using each channel for a LF and HF post, then why is it that you would buy an FPB300c for the LF and retain your FPB200c for the HF?? Doing a quick search for Krell shows that a single FPB600c is MUCH less than a 200c plus a 300c. Why wouldn't you just sell the 200c and buy a 600c?? Thanks.
For Mcoker: I'm using the N802s for mains, the HTM1 for Center and ASW-4000 for the sub.
The N802s were a better choice for me: budgetary, wife-factor and asthetically, than the N801s. The N803s compromised too much on the bass and the mid-range housed within the cabinet confines the sound, In my opinion.
Also, the N802s were my choice among the AA-10Ts and the Revel Studios: both required more amplification (more money) than the N802s: although I did like the Studio sound...
The B&K monoblocks will be relegated to Center Fronts and Rear, with the 7B-STs doing the monoblock duties on the 4 mains. Alternatively, if I go with a DVD-A approach, in lieu of a DVD-V, I'll go N802 all around. The DVD-A will assume 6, or more, full-range speakers; while the DVD-V somewhat assumes surround-type speakers.
Let me know if I can provide anymore feedback.