Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

@kijanki 

Heres a Rowland that specs 60 into 8ohms,  120 into 4 ohms just the way you like it. The actual measured powers are "  Fig.7 indicates the THD vs power for 8, 4, and 2 ohms at 1kHz, one channel driven (bottom, middle, and top curves respectively; line voltage of 113V). The maximum output power at 1% THD was 84W (19.2dBW) into 8 ohms, 140W (18.5dBW) into 4 ohms"
Read more at https://www.stereophile.com/content/jeff-rowland-design-group-model-1-power-amplifier-measurements#D...

The spec is twice the power into 4/8 ohms is just as you like 120/60 watts. The measured is 140/84 watts, not double. Note as I predicted the 8 ohm power is understated as it must be. But 120/60 watts are just minimum specs, not what the amp CAN do. Good manufacturers always underspec to make sure they make spec. 

Here is a Krell speced very close to 2/1 power into 4/8.  However the actual ratio is 910/625 watts. hardly 2/1. 


 Although the Krell's specified maximum power into these loads is very high, at a respective 575W (27.6dBW) and 900W (26.5dBW), the amplifier exceeded those powers, clipping at 625W into 8 ohms (28dBW) and 910W into 4 ohms
Read more at https://www.stereophile.com/content/krell-solo-575-monoblock-power-amplifier-measurements#17OE2KQdwm...

Cant you see that the doubling down is just a spec and to make that spec they have to go way over on the 8 ohm to get the 4 ohm to work out. The Krell barely makes spec with only 10 watts to spare on 4 ohms but exceeds 8 ohm power by 50 watts. 

I have a friend that loves to see amps double down but none actually do. Its nice when they get close but its just impossible to be exact or just close. 

Where does this religion of doubling down get its followers?

I will clarify; the bridged AHB2 drives the Kingsound King III ESL much better than a stereo unit alone, or two stereo units in passive biamp mode. 

As the discussion of the thread centers around bridged operation, I don't believe I have stated the capacity of a stereo unit on this forum to drive the Kingsound King III.

When I refer to "level unlimited" I mean that the amp is at maximum output of the preamplifier turned full on and the speakers not hitting past perhaps 87-88 dB. I would call an amp "level unlimited" where in my use I would not turn the level up more, but the amp could certainly provide a higher listening level. It may not be a technically correct description, but it serves to indicate the situation. I do not attempt to listen to systems at "live", i.e. above 90 dB levels, and I do not recommend others to do so. 

I have said several times previously that there is NO sonic degradation in bridged mode, nor distortion associated with running the amp full out. The amp is FAR superior sounding in bridged mode regardless of the speakers used, efficient or less efficient. 

 The AHB2 was never even close to clipping. Relevant to that, summarizing the discussion from the Owner's Manual, "... the AHB2 has an Over-Temperature Fault circuit that monitors the heat sinks constantly. If either one reaches the max allowable temperature the channels are muted to protect the amp and speakers. All high-power systems are shut down to facilitate cooling... One or both heat sinks will be very hot.. power reset after cooling." (Again, summary) 

The amps were actually running cool with the Kingsound King ESL, I could keep my hand on them. The amp also has a "Clip" light indicator, which never, ever came on. The King III is nominal 6 Ohm and 83 dB sensitivity. 




 

@kijanki  Yes, drop across resistance will double, but reserves in power supply combined with the feedback will make up for that.

I dont see why it is a virtue especially if it is just a spec and not what is really going on. Has Stereophile tested any of these amps. Please provide a link.

I never said it is a virtue - just the opposite.

I, prehaps misinterpreted this statement as something you agreed with.. 

 

Exact doubling of the power is treated on this forum as a virtue.

 Under RMS testing (which I have responded to in your other thread) there is no power suppy reserve, its flat out. 

Please tell me how feedback is going to find power where there is no more. Feedback does not create power. Rather than keep telling me it does tell me HOW it does.

@douglas_schroeder    When I refer to "level unlimited" I mean that the amp is at maximum output of the preamplifier turned full on and the speakers not hitting past perhaps 87-88 dB. I would call an amp "level unlimited" where in my use I would not turn the level up more, but the amp could certainly provide a higher listening level. It may not be a technically correct description, but it serves to indicate the situation. I do not attempt to listen to systems at "live", i.e. above 90 dB levels, and I do not recommend others to do so

It appears you may be confusing gain with power as many do.

I mean that the amp is at maximum output of the preamplifier turned full on and the speakers not hitting past perhaps 87-88 dB.

This is the statement I do not understand. The amp is doing what?

The top setting on a preamp does not conform to any percentage of the power amplifier's potential output. Some systems max out on power at 9 on the clock. some at 12 some not even at full up, which is a good situation where the 9 on the clock is very bad, though I hear some like it as they think there headroom above that setting, where there is not. 

90 db is a nice listening level, however do you sometimes find a CD might not get to 90 at full preamp level? And of course some will be too loud.

ramtubes
It appears you may be confusing gain with power as many do.

He is, by me too.

douglas_schroeder

The amp is FAR superior sounding in bridged mode regardless of the speakers used, efficient or less efficient.

I ask again, then why sell it in stereo mode if it’s so hobbled in stereo mode???
You should then be suggesting that no one buy it for stereo mode listening there are far better offerings.

douglas_schroeder
I have said several times previously that there is NO sonic degradation in bridged mode, nor distortion associated with running the amp full out.

This is a furphy, I didn’t ask that half a page back, I asked a simple question of amp sound quality driving the Kingsound III it was ignored. I present it again.

"How did one stereo amp sound to a level it was totally comfortable at.
Then the bridged ones at the same level?"
"To gauge which sounded better."
"NOT WHICH COULD GO LOUDER!"

I think it all needs "paralleled interconnects attached to each channel", that should fix the problem/s.


Cheers George