Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

Does running this amp in bridge mode mean each channel will see half the impedance i.e 2 Ohm each when connected to a 4 Ohm speaker.  If so will this cause a problem when the speaker dips to 3 or 2 ohms?. 

Anyone running Benchmark AHB2 in bridged mode with low impedance speakers?. 

Test results unbridged and bridged.

"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."


@twoleftears I did read the article by 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:


< 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


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

OK, so Benchmark amp is not totally immune to the effects of bridging, but I still see them sending out pairs to reviewers so they can use them in bridged mode. So they must have a fairly strong level of confidence in their performance.
Is the raise of Noise floor from -112 dB to -109.2 dB really bad?, Seems like this is quite better than many implementations by wide margin at least 6 to 9 dB below, or did I get this wrong?.