Running Benchmark AHB2 in bridged mode and 4 Ohm Speaker

As usual, some of us try to help the OP and some of us go off on a tangent to defend their own stuff. Then everyone gets mad, I'm not mad though I am surprised at some of the responses. :(

I was surprised to see that the ATC 19 is actually 19 liters which is only 0.67 cu ft. I can't imagine why someone wants to connect this little guy to a 370 watt bridged amplifier. The speaker only goes down to 55 Hz. The resonance can be seen on the impedance graph.

I have no doubt that the Benchmark performs as stated. I am surprised that there is such fuss about whether distortion at the 0.0002 level doubles or not. Or whether the very high damping factor is cut in half. Or whether the imperceptable noise is doubled or not. Most likely your preamp will create more noise than this amplifier.

Its a bit like Woody Allen said...  "Boy, the food at this place is really terrible." The other one says, "Yeah, I know; and such small portions."

@ramtubes lol noted, it did cross my mind to get preamp and DAC from Benchmark but I am constrained by using Wavelet. My core concern was stability at or below 4 Ohm bridged. My questions are answered. I am in the process of getting a second amp. Thanks.

My questions are answered. I am in the process of getting a second amp. Thanks.

Total $6K.
Pity for that you could of got a pair of John Curl designed Halo JC1 monoblocks that would eat these bridged AHB2's for breakfast. 
They "unbridged" output  400W into 8 ohms, 800W into 4 ohms, 135 amps of peak current, and 25W of pure class-A power into 8 ohms. 
                                  JUST SAYING!

Cheers George 

ramtubes said:

I was surprised to see that the ATC 19 is actually 19 liters which is only 0.67 cu ft. I can’t imagine why someone wants to connect this little guy to a 370 watt bridged amplifier. The speaker only goes down to 55 Hz. The resonance can be seen on the impedance graph.

It’s a sealed cabinet design and bass rolls off slowly providing pleasing extension into the mid 40’s in room.
Obviously 380W is not required (or used by me) but 150-200W is useful with the low sensitivity SCM19’s if one wishes to explore the considerable max spl of which they are capable (108dB). ATC recommends 75-300W, though to be fair a single AHB2 drives the SCM19’s very well.
Since my equipment resides in a room corner I also wanted to exploit the placement flexibility of mono blocks which allows positioning behind the speakers and short speaker cables (which should also mitigate loss in damping factor from bridging - not that DF is an issue ;-)
In regard to your other snipe at me, go back and read the first line of my first response in this thread. My subsequent posts were then attempts to correct (apparently deliberate) misinformation. Something you apparently have no problem with.

Here is a plot of the no load and 6-Ohm load THD vs. output level for the AHB2. As stated above, the 6-Ohm bridged mono load is equivalent to 3-Ohm stereo loads on each output simultaneously. Note that the 6-Ohm and no-load curves are virtually identical. Also note that the THD is always better than -120 dB relative to full output and at lower power approaches -140 dB relative to full output. If you do the math, you can calculate the SPL produced by the distortion signal given your speaker sensitivity. In all cases, the calculation will show that the distortion will be reproduced at a level that is always below 0 dB SPL at 1 meter from the speakers. This means that the distortion signal could not be heard in isolation in a quiet room. For this reason we can say that the AHB2 produces no audible distortion at any output level below the clip point.

In contrast, the JC1 (suggested by George) produces 0.15% THD at full output which is only 56 dB lower than the output signal. This means that the distortion produced by the JC1 will be reproduced at a level that is well above 0 dB SPL. The distortion produced by the JC1 should be audible.

However, in George's defense, I should point out that he is correct in stating that 100 W is plenty of power (20 dB above 1 W) with reasonable speaker sensitivity in a small room. Add 20 dB to the speaker efficiency to calculate your peak SPL. But keep in mine that this is peak and not average. With music, your SPL meter will typically read about 12 dB lower than the peak SPL due to the "crest factor" of the music.

Bridged mono increases the maximum achievable SPL by almost 6 dB. In some situations, this extra capability may be required. Unlike virtually all other amplifiers, there is no performance penalty when selecting the bridged mono mode on the AHB2, you just get a 6 dB increase in SPL (nearly 4 X power).

Here is a link to the THD plot for the AHB2