Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

Thank you Al, but I lost all hope - it is almost 6 months now and no improvement.  All audio tests show -95dB.  My doctor says it was most likely a virus from the shingles variety.  After 15 sessions in hiperbaric chamber and two direct injections of steroids thru the eardrum my eyes suddenly improved and  I'm typing this without glasses (+2 before).  Doctors have no clue why.

That’s so scary Kijanki, I too hope it comes back.

Love all your knowledge that you all have been speaking to. When building my system I considered more Benchmark amps and read a lot of discussion similar to your thread so I bought two and thought I could always get four if needed. I had completed the system in a tiny place in Cali and moved to a huge space now and got the system set up the way it should be. When showing off to friends and the occasional maintenance guy I would get my Maggie’s to clip and could hear it happening if I pushed them. So here I am thinking I may need more power. I would also get my Pass X-250 (going to my main subs) to bury the bias needle in large transients and movies especially. I have been so crazy with work I couldn’t get everything set up right. After my system was hit my lightening and bought a P15 to protect it the Pass would pull too much power and shut down the P15. I started plugging the amp into the wall directly at each listening session as everything was before the lightening and pulling it out afterwards. . .

So about out three weeks ago I was able to sit down and do room correction with REW and MSO adding in my SVS subs. Which by the way made the house and windows shake when I turned them on so bad that I literally jumped off the couch because they scared my soul, the water on my table had the ripples, and my wife jumped out of the shower upstairs yelling that lightening/thunder just shook the house and I needed to shut down the system and unplug it because lightening was in the area. Anyway I started with 4 and ended up getting to 12 biquad filters going in my Mini DSP and with some playing around got things to sound amazing. I noticed now with the room correction how much more accurate the music was and how little the subs had to work to make the transients that sent everything clipping before, now playing at -15 for movies and -20 for music.

Now I don’t come close to clipping playing louder than I would ever listen but do in demo mode on any amps + have everything running off of my P15. The power needle barely moves. . . With all the speakers running full range (obviously MSO attenuated the subs naturally). Who would have guessed it. FYI you barely hear the system upstairs now with all the subs working together even though everything is more impactful.

So what I’m saying is if your having clipping issues look at your room nodes, buy four quality subs, play with some room correction and placement of the subs and the power argument will become a moot point. I’m happy to answer any questions if people want to try this path.

Kijanki FWIW you are one of the no nonsense technical  guys on this site whose insights I value most.   Keep it up!

Thank you hifidream, mapman

There are many good comments in this thread but there is also much erroneous information. In most cases, this erroneous information is based on the assumption that the AHB2 behaves like most power amplifiers. The statements made would be true of most power amplifiers, but do not apply to the AHB2.

The AHB2 does not act like a traditional power amplifier because it has a very unique design. It has tightly regulated power supply rails, a patented feed-forward error correction system, and an offline protection system that is not in the signal path.

Unlike virtually all other power amplifiers, the THD produced by the AHB2 does not increase under load. The 8-ohm and 4-ohm THD vs. Power curves are absolutely identical. Even when loaded with 2 ohms, the THD is virtually unchanged. To the best of my knowledge, no other power amplifier can do this, or even come close to doing this. And, no amplifier delivers lower THD or lower noise at any price. The AHB2 holds the record for lowest THD and lowest noise. It is also important to understand that this performance is not just achieved at one particular load impedance, test frequency, or operating level. It is achieved into any rated load at any power up to full output power, and any test frequency between 20 Hz and 20 kHz.

The red clip lights on the AHB2 are driven by a circuit that measures the THD. If it exceeds 1% the lights will turn on. The AHB2 delivers an astonishing 0.00011% THD, 1 kHz at full rated power into any rated load.  The transition from 0.00011% to 1% is abrupt, but it occurs above the rated output power. This means that the AHB2 stays clean, even when you drive it almost to the rails. Ordinary amplifiers cannot do this. With most amplifiers, THD gradually increases with output level and with increasing current load. With the AHB2, THD is not a function of output current.

The impedance load ratings for the AHB2 are based upon long-term thermal limits (prolonged operation into the specified load impedance). This is not a limitation on the allowable minimum impedance of the loudspeaker. It is a rating for the nominal impedance of the loudspeaker. If the impedance drops to 1 or 2 ohms at certain frequencies or is presented with a difficult phase angle, this is not a problem for the AHB2. Feed-forward correction is stable into any load. Feedback is not stable into any load. The AHB2 uses a large amount of feed-forward correction and a minimal amount of feedback. This allows stability into virtually any load. Match your speakers to the AHB2 on the basis of nominal impedance not minimum impedance. The impedance minimums are not a concern.