Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

According to Benchmark the amp in bridged mono the maximum unclipped output voltage is 45.5 Vrms (64.4V peak) into a 4 Ohm load.

I would expect it to be higher. If the rails are 60 volts then the peak volts should approach 120, say 100 Volts with losses,  but the current won't support that as 25 amps are needed. BTW 18 amps is not an impressive amount of current for modern amp of that size. Should be more like 40 amps. The Mitsubishi Docking Amp of 1978 delivered 60 amps, I measured it!

Something is a little off here and the more I here the more I wouldnt want to bridge this amplifier. I have nothing against bridging in general and have made bridged amps.

The reason we bridge amplifiers is when WE DO NOT have a low impedance load. We bridge to get voltage not current. We bridge to get some juice into 8 ohms. When we have 4 ohms we dont bridge. 

Where are the italics around here? All caps is my best substitute. :)

georgehifi, my question was in the form of yes/no.

Are you speculating, or do you have actual experience with the amp in different configurations?

I repeat, If you have a technical background and understand what happens when you bridge an amp, you wouldn’t be asking this question.

Cheers George

That 18 amp number was a mistake if you read further down it was clarified to be 29 amps. I am not an expert just going by what I read on benchmarks site and various reviews. Benchmark used the amp at a 2017 show to drive a pair of 4 Ohm PCM monitors in bridged mode. Reviewers have used it to drive 8 Ohm, 6 Ohm and 4 Ohm speakers in bridged mode apparently with good results. Actually I agree with you and George I don't really see why 1 amp in stereo would'nt be enough with the OP's efficent speakers that have powered subs so this amp is just driving the mids and highs I assume. But he seems to want 2 amps to try in bridged mode and from everything I have read on this amp it can do it. 

djones51
George I don’t really see why 1 amp in stereo wouldn’t be enough with the OP’s efficient speakers

Been there, done that.

https://forum.audiogon.com/posts/1647982

and here

https://forum.audiogon.com/posts/1647933

But he seems to want 2 amps to try in bridged mode and from everything I have read on this amp it can do it.

Not really into 2ohm which is what the amps will think their driving (bridged) and then there's the disadvantages with bridging that I and many on the net outline. If there was no disadvantages then we'd all be using and selling bridged amps.

Cheers George

George I agree with you that with efficient low impedance speakers the OP may likely be better off with a single AHB2.

However it’s worth noting that unlike most power amps, the Benchmark AHB2 does not have increasing distortion into lower impedance loads. The bridged AHB2’s distortion is just as low as in stereo mode - the THX AAA circuit takes care of that - the quoted THD+N spec is the same for stereo/mono "at full rated output into any rated load". This has been corroborated by independent measurements. Note that Benchmark only provides power ratings for nominal 8 and 6 ohm loads in bridged mono.

In my case the bridged AHB2 amps do sound better than a single AHB2, but my ATC speakers are very different from the OP. The ATC’s are inefficient with high power handling (ATC recommends 75-300W) and have a nominal 8ohm rating with a minimum of 5.6ohms - pretty much the ideal application for the bridged AHB2.
Using the amps in mono mode also allows for much shorter speaker cables, which may also have contributed to my positive impressions vs a single stereo AHB2.

Having said the above, Benchmark have demoed with bridged AHB2’s on several occasions with nominal 4ohm rated speakers. So clearly they don’t see any issue. Here is a recent positive impression: 
https://parttimeaudiophile.com/2018/05/21/axpona-2018-benchmark-stays-smooth-with-martin-logan/