Benchmark AHB2 - To 'mono' or not to 'mono'


I own a single Benchmark AHB2 amp and have been considering another in order to run both in bridged mono mode, which will provide significantly more power to my speakers and presumably, greater dynamics. I've read in other threads where other owners (and perhaps others with opinions) had implied both positive and negative impressions concerning this approach. Assuming I'm not considering purchasing other amps at this time, does anyone have experience with both approaches and will you please share your impressions?
wwoodrum
My first question was going to be whether you really need the extra power for your situation. It seems you may not.

JA at Stereophile measured the Pulsar’s sensitivity at 83.5dB(B)/2.83V/m, which is quite low, so certainly some situations/program may benefit from more power than the 100W/ch of a single AHB2.
https://www.stereophile.com/content/joseph-audio-pulsar-loudspeaker-measurements

There would be absolutely no issues running the AHB2 bridged with your Pulsars - their impedance is mostly above 8ohms and only drops as low as 6.5ohms.
The distortion specs of the AHB2 in bridged mode will be just as vanishingly low as in stereo mode (see Audio Precision measurements conducted by JA and elsewhere).

Regardless of the measurements, I can say that in my case (ATC SCM-19 - low sensitivity 8ohm rated speakers like yours) I got an audible improvement from bridged AHB2’s.
The sound was essentially the same (no surprises) but more ease and better sound staging with the bridged amps. I also took the opportunity afforded by mono blocks to change to short speaker cable runs (and longer XLR interconnects). This probably contributed to the improved sound I noted. Certainly, being able to run very short speaker cables is an advantage of monoblocks.

Bottom line.
If you don’t want/need the extra power or the cabling flexibility afforded by mono blocks, just stick with the stereo AHB2 - but rest assured if you decide to go to bridged mono AHB2’s you won’t encounter a sonic penalty with your speakers.
For the damping of the membrane movement - speaker's own impedance is in the series with the amp's output. Most of this impedance is resistive.

A speaker relies both on mechanical damping and electrical damping, its Qms and Qes parameters; Raidho for example expressly recommended high damping factor amplifiers for their speakers as their woofers had high Qms and relied on the electrical damping of the amplifier. There are threads on trying to find a suitable amplifier for them as their bass would sound loose and bloated with low and normal damping factor amplifiers. Just compare a Pass and an Audionet amp and you will see how their bass is very different; the Audionet's bass is much more damped and dry with better transient response, but it can sound dynamically constricted with low Q overdamped speakers

Since the OP's Pulsar Seas woofers have more mechanical damping they may not need too much electrical damping from the amplifier; bridging the amp may offer a more dynamic bass if the stereo amp/speaker pair is overdamped.   


Electrical damping occurs because moving coil generates voltage that produces current in direction that causes motion of the membrane in opposite direction hence stopping the membrane.  This current is equal back EMF (voltage on the speaker) divided by impedance in the circuit that consists of amplifiers output impedance, cable impedance, and the driver itself.  At the end it comes to 6.1ohm vs 6.05ohm difference (about 1%).  Also for the same reason the highest effective damping that can be achieved is equal about 1.5 (nominal speaker's impedance divided by resistive part of this impedance).  It might explain why some tube amps, that have very low DF (as low as 1.5), still sound great.

There might be other reasons why some amplifiers sound worse when bridged. It might be unregulated (in most cases) power supply voltage that is sagging when twice the current is demanded.  AHB2 power supply is line and load regulated and should not sag.   From all the reviews, I've read, AHB2 sounded even better in bridged mode.
You lost me.  What do you mean by bridged.  Why would you ever want mono.  Wouldn’t you lose stero?  Wouldn’t this be like listening to an AM radio.  I still don’t understand why people would ever buy a $20,000 turn table because don’t you looses lot of detail compared to digital by way of CD player.  The first thing I noticed when hearing vinyl is the crisp highs disappeared such as cymbals.  The tightness of sound disappears and sounds muddy.  I have read articles about this and many think listening to music played on vinyl sounds inferior to digital.  Vinyl sounds warmer but the detail disappears.  I like to hear the detail.  Kind of compares to listening to compressed music as compared to listening to 16 and 24 bit.