[john_bull]

In the 7B, 14B and the 28B amplifier manuals, there is a clear warning and I quote:  "The minimum recommended loudspeaker load is 4 ohms".  Most 8 ohm (Nominal) and 4 ohm (Nominal) loudspeakers dip well below 4 ohms in some frequency ranges.  Does that mean the 7B, 14B and the 28B perform poorly below 4 ohms in these frequency ranges?

Also, what is the output power of the 28B amplifier into 4 ohm and 2 ohm loads?  The 28B manual says and I quote:  Maximum power output at onset of clipping into 8 Ohm is 1486 Watts.  Nothing is said about 4 ohms and 2 ohm loads.  Is the 28B not stable at 4 and 2 ohms? 

For the 7B and the 14B amplifiers, power output is specified for 8 and 4 ohms.  How about 2 ohms?

[Anonamemouse]

In the 7B, 14B and the 28B amplifier manuals, there is a clear warning and I quote:  "The minimum recommended loudspeaker load is 4 ohms".  Most 8 ohm (Nominal) and 4 ohm (Nominal) loudspeakers dip well below 4 ohms in some frequency ranges.  Does that mean the 7B, 14B and the 28B perform poorly below 4 ohms in these frequency ranges?

The image above shows the average inpendance load of an 8 ohm ported loudspeaker. as you can see it is only 8 ohm in 5 spots, it peaks at almost 25 ohm, the lowest is about 2 ohm. The perfect 8 ohm loudspeaker does not exist. The 8 ohm number is just an average, and usually even waaaay off.
An amplifier sees the impendance as resistance, something to overcome. I have yet to see a load that a Bryston amp cannot deal with.

Also, what is the output power of the 28B amplifier into 4 ohm and 2 ohm loads?  The 28B manual says and I quote:  Maximum power output at onset of clipping into 8 Ohm is 1486 Watts.  Nothing is said about 4 ohms and 2 ohm loads.  Is the 28B not stable at 4 and 2 ohms? 

Sure it is. Unless you have a perfect sinus wave at 2 ohm, that is probably something the amp will not be too happy with. But music is never the same.

For the 7B and the 14B amplifiers, power output is specified for 8 and 4 ohms.  How about 2 ohms?

It roughly doubles. So 100 watts at 8 ohm, 200 watts at 4 ohm, 400 watts at 2 ohm.blahblahblah

[95Dyna]

Below are links to John Atkinson's measurements in reviews of the 28B and 14B.  The 14 review is of the SST but shouldn't differ much from the current 14B SST2.  Both sets of measurements show the amps "running out of grunt" (Atkinson's words) into 2 ohms.  Bear in mind that these loads are instantaneous and not continuous.  My 7BSST2's drive my speaks with ease and they dip to .8 0hms at around 28 hz.

The 2 ohm outputs were measured to be 1050 w for the 28 and 720 for the 14.  Both are far below their respective 4 ohm measurements.  4 ohm for the 28 is 1800w and for the 14 just a shade over 1kw.

BTW, be sure to read the entire review and measurement sections as both received an excellent review.


http://www.stereophile.com/solidpoweramps/108bry/index4.html

http://www.stereophile.com/solidpoweramps/725/index7.html

[95Dyna]

I forgot to include the 7B SST2 which was also reviewed in Stereophile earlier this year.  Output into 4 ohms measured 930w and into 2 ohms 690w.  John Atkinson has some very good things to say about the 7B's measured performance.  For your reading enjoyment:

http://www.stereophile.com/solidpoweramps/bryston_7b_sstsup2sup_monoblock_power_amplifier/index7.html

[vegasdave]

Cool stuff!