Is a Bryston 3B SST2 enough for Magnepan 3.7i or 20.7?

Thank you Al,
Ok then the idea of bridging just went out the door...🤗
But To make sure I got this right:
So what you are saying is that the amp should also close to triple it’s power into the 2 ohm load (in the bridged mode) or about 3000w, in order to sustain the same increase of 6 dbw?

@Lucidear, no, I wasn’t saying that. When I said ...

So unless the amp is known to perform at or close to its best when driving 2 ohms in stereo mode I would not count on it providing good results when driving Maggies in bridged mode.

... I was referring to the amp being known to **sound** close to its best when driving 2 ohms in stereo mode, since in bridged mode it would "see" a 4 ohm load as 2 ohms. Implicit in that statement, of course, is that the amp should be able to function in a reasonable manner when driving a 2 ohm load in stereo, without overheating, fuses blowing, or self-protective shutdowns being triggered. The 2 ohm power capabilities you listed for the specific amps suggest that they would meet the latter requirement, but say little or nothing as to how they would sound in doing so.

And regarding how the amp would sound in bridged mode when driving 4 ohm speakers, the fact that Simaudio does not appear to provide a power capability specification for bridged mode for anything other than 8 ohms is not encouraging. (Also, btw, text on page 11 of the manual indicates a capability of providing 800 watts into 8 ohms in bridged mode, which conflicts with the specs page of that same manual and the specs shown at the website, which indicate 1200 watts).

Now understanding that these amps could sound different from one another, my question is:
Do these larger transformers, more capacitance etc. etc. have a noticeable affect on these Maggies even though the indicated output wattage of all three are very close to each other ?

While I certainly appreciate your attempts to determine these matters analytically, and if everything else is equal those factors are of course **potentially** beneficial, as a practical matter there are so many design-dependent variables and unknowns involved that listening, and/or finding credible reports of relevant listening experiences, is probably the only way to tell.

Best regards,
-- Al

P.S:  "355@4/500@8" in your post should of course be "355@8/500@4."

@lucidear, the main concern regarding the possibility of bridging that amp with Maggies is that a bridged amp "sees" the speaker impedance divided by two.  So it would see the 4 ohm impedance of a Maggie as 2 ohms, and most amps will not sound good driving such a low impedance.

So unless the amp is known to perform at or close to its best when driving 2 ohms in stereo mode I would not count on it providing good results when driving Maggies in bridged mode.

Unrelated to that, a minor point that may be worth mentioning is that the sensitivity numbers you cited appear to reflect the input voltage required to drive the amp to an output of 1 watt (into 8 ohms).  As opposed to the more usual way sensitivity specs are defined, which is the input voltage required to drive an amp to its maximum power capability.  On that basis, its sensitivity calculates to about 1.4 volts for stereo mode, which is a fairly typical number.

Regards,
-- Al 

While I couldn’t find measurements of the sensitivity of the three speakers that have been mentioned in the OP, I note that their sensitivity and impedance specs are identical. And I would assume that the sensitivity specs (86 db/2.83 volts/500 Hz) are based on a distance of 1 meter.

I would therefore expect that at reasonable listening distances (as opposed to 1 meter) the larger speakers would require **less** power to produce the same volume as the .7, not more. Large panel speakers tend to "throw" the sound forward to a greater degree than smaller panel speakers, since the height and width (especially the height) of the larger speaker will "subtend" a larger angle relative to a given listening position.

It is possible, of course, that like many speaker sensitivity specs the 86 db figure is somewhat optimistic (and I note that Stereophile’s measurement of the sensitivity of the 3.6/R was 83.5 db/2.83 volts, while that speaker also had an 86 db/2.83 volt spec). But as long as any inaccuracy in the specs is consistent among the three models what I said above would apply.

Also, I see that the 3BSST2 is specified as being able to supply 250 watts into 4 ohms. Keep in mind that even if you were to go to an amp rated at 500 watts into 4 ohms that would only be a difference of 3 db in maximum volume capability.

Good luck as you proceed. Regards,
-- Al