Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

@djones51 I am preparing to ask this question. Right now I am trying the speaker manufacturer / dealer to get me answer to the question "what the lowest impedance the speakers can dip to". 

Every speaker manufacturer should publish impedance vs frequency graph or just state the lowest impedance. Only very few do that, I don't get why.

I did get one response from John @ Benchmark regarding what the tested output @ 4 Ohm in bridged mode is. 

@twoleftears I am glad you mentioned this, I did also hear about this but no concrete info anywhere regarding this. I will try to find out. Thanks for point this out.

geek101
Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

I would never bridge an amp all you gain is watts, distortion goes up, damping factor is reduced, stability into low impedance’s is reduced, and current ability is reduced. "Basically" you turn a good amp into a high wattage P.A. amp.

If your speaker terminals allow it, and you have two "identical stereo amps" like 2 x AHB2’s, you should vertically bi-amp each stereo amp to each speaker.
http://www.av2day.com/wp-content/uploads/2014/05/biamp2.jpg

The reason these guys preferred vertical bi-amping over horizontal bi-amping, is that the powersupply in each amp can be totally accessed by just one bass driver channel when needed for the biggest dynamics.
http://av2day.com/2014/05/bi-amping-vertical-vs-horizontal/

Cheers George

Test results unbridged and bridged.

https://www.stereophile.com/content/benchmark-media-systems-ahb2-power-amplifier-measurements

"But the power output doesn’t stop there. With the flick of a switch you can transform the AHB2 into a monoblock amplifier. Unlike so many other amps with a bridged mono option, the AHB2 does not limit you to just 8 Ohm nominal speakers. In bridged mono, the AHB2 is rated for 6 Ohms, but there’s a bit of an asterisk to that.

In bridged mono, the AHB2 will deliver 380 Watts into 8 Ohms, and 480 Watts into 6 Ohms. Technically speaking, you can even drive speakers whose variable impedance dips into 3 Ohm range. However, if you try to exceed 486 watts into 3 Ohms bridged mono, you will trip the 18 Amp over-current protection and the amplifier will shut down."

from https://www.pooraudiophile.com/2015/07/benchmark-ahb2-power-amplifier-review-the-first-commercial-power-amp-with-thx-aaa-technology.html

all amps very different, call Benchmark

@twoleftears I did read the article by pooraudiophile.com and did reach out to Benchmark a while ago and asked about possible tested numbers till 4 Ohm when bridged. Here is the response I have recieved:

OUTPUT VOLTAGE INTO VARIOUS LOAD IMPEDANCES

< 0.0003 % THD+N at the following output voltages and load impedances, 20 Hz to 20 kHz

· 29.03 dBV, 31.25 dBu, 28.28 Vrms into 8 Ohms, both channels driven

· 28.92 dBV, 31.14 dBu, 27.93 Vrms into 6 Ohms, both channels driven

· 28.81 dBV, 31.03 dBu, 27.57 Vrms into 4 Ohms, both channels driven

· 28.57 dBV, 30.79 dBu, 26.83 Vrms into 3 Ohms, both channels driven

· 27.14 dBV, 29.36 dBu, 22.76 Vrms into 2 Ohms, both channels driven

· 35.05 dBV, 37.27 dBu, 56.57 Vrms into 16 Ohms, bridged mono

· 34.83 dBV, 37.05 dBu, 55.14 Vrms into 8 Ohms, bridged mono

· 34.59 dBV, 36.81 dBu, 53.67 Vrms into 6 Ohms, bridged mono

· 33.16 dBV, 35.38 dBu, 45.52 Vrms into 4 Ohms, bridged mono

Use dBV to calculate the peak SPL from your speaker/amplifier combination. Use the following formula: Amplifier output voltage in dBV + speaker sensitivity at 2.83V - 9 dB. Example: (29.03 dBV at 8 Ohms) + (90 dB SPL @ 2.83V 1m) - 9 dB = 110 dB SPL at 1 meter

AHB2 OUTPUT VOLTAGE AND OUTPUT POWER

Mode, Impedance, Noise Voltage,   Maximum Output Voltage, Watts

                             dB relative to 2.83 Vrms, dB relative to 2.83 Vrms

Stereo 8-Ohms -112 dB 20 dB 100

Stereo 4-Ohms -112 dB 19.8 dB 190

Mono 8-Ohms -109.2 dB 25.8 dB 380

Mono 4-Ohms -109.2 dB 24.1 dB 518