Amp- stereo or run mono and buy another amp?

[Michaelb4]

I run a Benchmark AHB2 stereo mode into a pair of B&W 802d3. The amp does not clip at any listening level I would use. Is there any benefit running a pair of amps mono other than they would play louder than I would ever want to listen?

[GregWormald]

That's really hard to say, although more power (same quality) and more current delivery is nearly always better. Loud transients can take up enormous amounts of power and there can be 'strain' long before clipping is noticed. There is often a sense of 'ease' with high power amps that is hard to get any other way.

 

Your speakers and amp seem well-matched in terms of power so unfortunately the best way to tell would be to borrow another amp and give it a trial run. If you haven't noticed anything and you listen quietly then any improvement may be small.

 

Why not give B&W a call and see what they have to say? Benchmark may also have comments although wanting to sell you another amp may skew their recommendations.

[audiobomber]

I agree with virtually everything @GregWormald said above. IME, a second amp will almost certainly improve the sound. The question is whether the improvement justifies the cost, which is something only you can answer. A home trial would be definitive.

 

I suggest though that increased current drive is far more important than more watts with your speakers. If you add a second amp, you should run both amps in vertical bi-amp mode, i.e. one stereo amp per speaker; one channel for the woofers, the other channel driving the midrange and tweeter.

 

Monoblock operation will play somewhat louder than vertical bi-amp, but the damping factor is cut in half when the channels are mono-strapped, and so is impedance. That means your amps have decreased control of the drivers and the current demand doubles. That can be a big problem with demanding speakers, which yours definitely are. According to Stereophile's measurements:

 

"This speaker will play loud for very little input voltage! However, it is a relatively demanding load for an amplifier to drive. Fig.1 shows the B&W's electrical impedance (solid trace) and phase (dotted trace). The magnitude drops to 3 ohms between 100 and 130Hz, and again between 670 and 770Hz; and while the electrical phase angle is low in the lower region, it becomes increasingly inductive above 600Hz, reaching +46° at 1kHz, where the magnitude is 4 ohms. There is also a combination of 4 ohms and –64° at 69Hz, implying that this speaker does require an amplifier that is not upset by a low effective impedance." https://www.stereophile.com/content/bowers-wilkins-802-d3-diamond-loudspeaker-measurements

 

I have a friend with B&W 802 Nautilus speakers. He was driving them with a pair of Bryston 3B-ST amps. The dealer had installed the amps in monoblock mode. I was very disappointed with the sound, so I reconnected them in vertical bi-amp mode. The improvement was night and day. 

[davide256]

I find wattage mostly benefits peak transients, bass impact... which is probably less than 3% of the content you are actually listening to in music...

and  requires a lot of work before the amp to get right. Unless you are hearing a substantial improvement in these areas using headphones,

I'd worry more about whats in front of the amp for improvement.

At which point the other 97% still remains more important when considering an upgrade. Of course if you have a large room more wattage

may be a necessary evil ($$$)

[Killahertz]

It really depends on what style of music you listen to, the size of your your room and how loud you like to listen.  The Benchmark AHB2 is an excellent amplifier but at only 100 watts into 8 ohms its not really a powerhouse.   I would probably see clipping on my B&W Signature 805’s because they aren’t nearly as efficient as your 802’s.  I’m using 125 watts of tube power (bigger watts!  Just kidding) that replaced my solid state Aragon 4004 200 watt per channel amp and I’d swear they (tube monoblocks) sound more powerful.  They are definitely more dynamic and lively.  You should contact Benchmark because I see they don’t increase power when bridged into lower impedance than 6 ohms.  They may not be very happy with a 3 ohm load right in the middle of the musical spectrum.

[John Siau]

We would love to sell you a second AHB2, but the honest answer is that you do not need it if you are never lighting up the clip lights.

 

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 identical. Even when loaded with 2 ohms, the THD is virtually unchanged.

 

The red clip lights 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.

 

The reason the AHB2 stays clean is the patented feed-forward error correction system. The AHB2 is a very unique design and many of the usual rules of power amplifiers do not apply.

 

I would love to sell you a second AHB2, but you do not need it!

[GregWormald]

There you go @Michaelb4. If the man who makes money when he sells the amp says you don't need it, you probably don't.

Enjoy the music.