Review and Measurements of Benchmark AHB2 Amp

[BDWoody]

It's much too hard to generalize on required power, etc but over the years it's been my experience that just about any speaker with a sensitivity under 90 will require at least 200wpc@8ohms to really come alive and rock. But again there are too many variables in input impedance, room size, music genre and listening habits, lots more to throw out a simplistic answer like that.
But if you like to rock&roll or play symphonic music at live concert levels, under 90db=200wpc+++. JMHO

I believe that is why people often have complaints about the LS50's, for example...

 

[anmpr1]

I believe that is why people often have complaints about the LS50's, for example...

These smallish (very smallish) speakers are great for up close listening, PC speakers for instance. In an apartment, where space is dear, etc. They have gotten much better over the years, however even a speaker such as the old BBC monitor (LS3/5A) was very good sounding. Those just couldn't play loud, and if you tried to push it over the cliff (or even get near the precipice) you risked blowing out its little woofer.

You get taken in by the coherent sound coming from the small box, but after a while the desire for something larger manifests. At least that is my experience.

 

[BDWoody]

These smallish (very smallish) speakers are great for up close listening, PC speakers for instance. In an apartment, where space is dear, etc. They have gotten much better over the years, however even a speaker such as the old BBC monitor (LS3/5A) was very good sounding. Those just couldn't play loud, and if you tried to push it over the cliff (or even get near the precipice) you risked blowing out its little woofer.

You get taken in by the coherent sound coming from the small box, but after a while the desire for something larger manifests. At least that is my experience.

Mine as well...
I love mine near field... they are wonderful for what they are for...but they have a tough load for an underpowered amp to handle...and pushing them at all doesn't go over well.
Sensitivity: 85dB/2.83V/m. Nominal impedance: 8 ohms. Minimum impedance: 3.2 ohms.
Could easily lead to disappointment...

I have 708p's now for that larger space...much better suited...

 

[kaka89]

It's not a problem on an absolute level, because in the scheme of what everyone is asking for in order to buy their high-end power, two AHB amplifiers bridged are not even in the 'expensive' category, although they are not cheap.

Two AHB2 aren't cheap even in audiophile standards.

 

[anmpr1]

Two AHB2 aren't cheap even in audiophile standards.

Yes. Not cheap. But not expensive in the high-end amplification scheme of things. For instance, a mid-range Boulder amp with similar power specs as two Benchmarks will set you back about thirty large. Five times the price. My guess is that the Boulder is not as electrically transparent as the Benchmark, although it is likely as (if not a bit more) powerful. Given what you get with a pair of AHB2, it might be (to use the hackneyed reviewer phrase) considered a bargain.

 

[oivavoi]

Yes. Not cheap. But not expensive in the high-end amplification scheme of things. For instance, a mid-range Boulder amp with similar power specs as two Benchmarks will set you back about thirty large. Five times the price. My guess is that the Boulder is not as electrically transparent as the Benchmark, although it is likely as (if not a bit more) powerful. Given what you get with a pair of AHB2, it might be (to use the hackneyed reviewer phrase) considered a bargain.

Given that all decently made amplifiers made these days in the range of $200 to $500 by all accounts are transparent to the human ear under normal use cases, I certainly don't think that the AHB2 is a bargain. Sure, one can pay more for the knowledge that one has the best amplifier ever built, and that there are close to no conditions where it will do anything audible to the signal (unless it clips on low-sensitivity speakers), and that may be worth it to some.

But a "bargain"? Nah. That's like thinking it's a bargain to buy a car which can drive in 300 km/h because it costs less than other fast cars, even though one lives in a place where the maximum speed limit of 100 km/h is strictly enforced. But at least you will know that that it won't be the car that holds you back that one day in your life when you'll be able to use it on a race track.

 

[DonH56]

"Bargain" is relative. There are many high-end amplifiers in the $10k to $150k (and probably up) range. And I am not aware of a sub-$1k amp with similar power that can touch an AHB2's specs and performance (but I certainly do not know them all). And of course to different folk "bargain" is also relative; a more expensive wrench that really does perform and last better but costs 2x the price of a cheaper wrench can be a bargain. A $100 amp may be a bargain economically for some whilst a $3k amp a bargain to others.

I personally don't buy the car analogies for most audio gear, especially amplifiers. Cars are not (at least IME) called upon to deliver 20 or 30 dB peaks in speed when motoring about town, for instance, while your audio amplifier sees that sort of range fairly often.

Over the years my "bargain" line has moved up with income and experience. Too many "cheap" buys over the years sitting in the back room gathering dust, or broken and in the trash (as if -- "no, I can fix that, when I get a little time"), and I am able to afford better stuff than the $20 wrench set now.

 

[oivavoi]

I personally don't buy the car analogies for most audio gear, especially amplifiers. Cars are not (at least IME) called upon to deliver 20 or 30 dB peaks in speed when motoring about town, for instance, while your audio amplifier sees that sort of range fairly often.

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

EDIT: I don't think it can, but I've yet to see any specs for max peak current on it. There are quite a lot of other cheaper amplifiers which we know can deliver those peaks, though

 

[DonH56]

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

How is that relevant? If your car is going 25 mph I cannot imagine suddenly needing to do 250 mph. You can always set up an example of failure. I'd rather celebrate the good now and then.

As for the answer, I really doubt it, but there are plenty of online calculators around you can use to find out. You need to know distance to speakers and estimate sound reinforcement from the room (if any), natch.

In terms of amplifiers, relative to the competition and current state of the art, I do think the AHB2 provides good value for its performance.

 

[oivavoi]

How is that relevant? If your car is going 25 mph I cannot imagine suddenly needing to do 250 mph. You can always set up an example of failure. I'd rather celebrate the good now and then.

I think it's relevant because that's what I want from my speaker system, since I'm mainly listening to classical music and 30 db peaks happen quite often. I'm currently using the discontinued Yamaha P7000s for my passive floorstanders in the living room. That amp easily delivers that and more, all while having distortion levels that are well below the levels of audibility for musical material. (AP measurements of its little brother P3500s are excellent: https://www.homecinema-fr.com/forum...mpli-yamaha-p3500s-mise-a-jour-t30056383.html )

Before it was discontinued the P7000s cost around a 1/5th of the price of the AHB2, and yet it delivers much more power. Other examples can be found as well.

But I think the main reason I'm objecting to the use of the term "bargain" is that it kind of sets the obscene prices in the hifi world as the bench mark. "So it doesn't cost 100K? Wow!" I think that's a low bar to use for what constitutes a bargain or not...

 

[Kal Rubinson]

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

EDIT: I don't think it can, but I've yet to see any specs for max peak current on it. There are quite a lot of other cheaper amplifiers which we know can deliver those peaks, though

29 A peak, per channel, both channels driven.
Other relevant data here: https://benchmarkmedia.com/products...MIqqznhtT25QIVkJOzCh19SQ7yEAAYASAAEgLYa_D_BwE

 

[oivavoi]

29 A peak, per channel, both channels driven.
Other relevant data here: https://benchmarkmedia.com/products...MIqqznhtT25QIVkJOzCh19SQ7yEAAYASAAEgLYa_D_BwE

Thanks! 29 A is pretty decent, I must say, particularly given the diminutive size of the amp.

 

[HammerSandwich]

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

That's a LOT of dynamic range. 30dB is 1000x power output, right? So, a 100W amp has that headroom when average levels are 0.1W or so. Your example needs about 400W, if we're looking at 1M SPL.

If you want ~113dB at 3M, I conclude that you need more sensitive speakers at least as badly as more amplifier. An 87dB speaker may be the median, but it needs multiple kW to produce 113dB peaks at 3M.

 

[DonH56]

I think it's relevant because that's what I want from my speaker system, since I'm mainly listening to classical music and 30 db peaks happen quite often. I'm currently using the discontinued Yamaha P7000s for my passive floorstanders in the living room. That amp easily delivers that and more, all while having distortion levels that are well below the levels of audibility for musical material. (AP measurements of its little brother P3500s are excellent: https://www.homecinema-fr.com/forum...mpli-yamaha-p3500s-mise-a-jour-t30056383.html )

Before it was discontinued the P7000s cost around a 1/5th of the price of the AHB2, and yet it delivers much more power. Other examples can be found as well.

But I think the main reason I'm objecting to the use of the term "bargain" is that it kind of sets the obscene prices in the hifi world as the bench mark. "So it doesn't cost 100K? Wow!" I think that's a low bar to use for what constitutes a bargain or not...

I was addressing the car analogy. You define what constitutes value and performance for you. If the Benchmark AHB2 does not provide the power you need then it is not a bargain at any price for you. Other amplifiers can deliver much more power but AFAIK not at the same low level of distortion. That is the problem with blanket "all or nothing" statements; there are always counter examples.

I can name lots of higher-powered discontinued amplifiers that cost much less than the AHB2. What would you compare it to today? For that matter, my Emotiva XPA-2 has much higher power for about 1/2 the cost but in terms of performance is no match for the AHB2 except in raw power. It is good enough for me, or at least enough that I am spending money elsewhere in my system, but when I was looking at other amplifiers the AHB2 was much less expensive than many of them. A number of pro amps have much more power but not the SNR or low distortion levels. Etc.

I do listen to a lot of classical music but at this point it's just a pissing contest. That's the thing, you are taking me to task on a definition that is IMO relative and personal, and you are "setting the bar" for all others. In any event I have no real argument with you and agree prices have generally gotten crazy.

 

[RichB]

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

EDIT: I don't think it can, but I've yet to see any specs for max peak current on it. There are quite a lot of other cheaper amplifiers which we know can deliver those peaks, though

Forgive me for being redundant but here are the measured levels for stereo tones played at my listening position where -31 was measured at 2.83 volts. Since the Salon2's are basically 4 Ohms speakers, this is in the tables as 2 watts.

Based on this, there is more than 20 dB available single amped driving the Salon2's.
I should note that the LA4 is in the chain to drive the AHB2's at the lowest gain.

I have never seen the clip lights illuminate playing movies considerably past comfortable levels.
For example, Aquaman 4K played at -18 did not clip and the Salon2 woofers show considerable movement during the Kraken scene.

For music, I played Lorde Royals full range into the Salon2's and at -10 there is a clip indicator.

In theory, I could use a kilowatt but in reality, I have all the power I require.

- Rich

 

[anmpr1]

But a "bargain"? Nah.

I get what you are saying, but consider this. Usually a bargain is a good deal on whatever you are looking for. Let's say that you are looking for the most electrically transparent amplifier made, in the entire world (whether you can hear that level of transparency, or not, is beside the point--it is what you want and what you are going to buy). So you start comparing all known amplifiers, both small and large. And let's say that you find it--the most electrically transparent amp. And from your searching you discover that, price-wise, it is 10 times more expensive than some less electrically transparent amps, but 10 times less expensive than other less transparent amplifiers. In that case, knowing what you want, you might well reasonably conclude that you got a bargain for the price, given the entire scheme of all things amplified.

 

[wynpalmer]

Can the AHB2 deliver 30 db peaks on a typical 87 db sensitivity speaker, with a baseline listening around 80-85 db?

EDIT: I don't think it can, but I've yet to see any specs for max peak current on it. There are quite a lot of other cheaper amplifiers which we know can deliver those peaks, though

From the owners manual specs, 29A in mono mode, both channels driven.
The rated output SINAD is 118dB.
I have to ask- why bother with trying to achieve SINADs of 108dB+ from a DAC or ADC/DAC path if you don't have an amp that doesn't appreciably degrade the overall SINAD of the system to drive the output into.
By the way, it isn't the lowest distortion, highest SINAD power amp on the planet. Any of the top of the line Halcro amps are alone on that pinnacle, but if you think the AHB2 isn't cheap (I do think it's cheap, by the way) then you would have a serious problem with the Halcro amps that are one to two orders of magnitude more expensive for essentially only "slightly/inconsequentially" better harmonic and intermod distortion specs/measurements at frequencies c. 5kHz and above.
For what it's worth, I've listened to a pair of gain matched AHB2s vs. Halcro DM68s and I could not tell the difference, but I (and others) could distinguish the AHB2s versus gain matched Rogue M180s or a Hypex Ncore400. Yes, they were single blind AB tests, and not double blind ABX, so take it for what it's worth.

 

[oivavoi]

I have to ask- why bother with trying to achieve SINADs of 108dB+ from a DAC or ADC/DAC path if you don't have an amp that doesn't appreciably degrade the overall SINAD of the system to drive the output into.

Personally I don't bother with that, TBH. My priorities gear-wise is to have gear which allows me to use:
a) crossover/integration of multiple subwoofers (and possibly external active crossover for main speakers)
b) room correction in the bass
c) easy access to basic eq and tone controls, for adjusting recordings to taste (some have too much bass and some have too little)
d) multichannel upmixing (that's a newer development for me personally, but I increasingly find it to be indispensable)

These things make a perceivable big difference for me, whereas SINAD numbers beyond a certain threshold don't. So I'm fine with a SINAD of 80 db, for example, as long as my gear does these other things which matters a whole lot to me when it comes sound reproduction and creating musical illusions in my brain. I'll take a higher SINAD if I can get it, of course, but I don't stress with it beyond a certain level. Priority for me is gear which does the other stuff well.

For what it's worth, I've listened to a pair of gain matched AHB2s vs. Halcro DM68s and I could not tell the difference, but I (and others) could distinguish the AHB2s versus gain matched Rogue M180s or a Hypex Ncore400. Yes, they were single blind AB tests, and not double blind ABX, so take it for what it's worth.

This is very interesting! Cool. Would you care to share more details about the setup, what the perceived differences were, etc? I don't find it strange that you could distinguish the AHB2 from the M180 tubes, nor that you couldn't distinguish the AHB2 and the Halcro beast (both super-magnicient AB amps). But it's intriguing that you could distinguish the AHB2 and the Ncore... I would like to know more, if you care to share. (my one concession to gut-based audiophoolery is that my gut is still somewhat skeptical to class d amps. Well-performing ab amps still feels like the safer choice - possibly with the exception of purifi).

 

[HammerSandwich]

Plot the best performer at a given price in blue & the worst in red (linear scales), and I'd say that the amp market looks a lot like this:

(Drawn before @wynpalmer noted that Halcro is still around & kicking butt.)

"What is a bargain?" is left as an exercise for the reader.

 

[wynpalmer]

Personally I don't bother with that, TBH. My priorities gear-wise is to have gear which allows me to use:
a) crossover/integration of multiple subwoofers (and possibly external active crossover for main speakers)
b) room correction in the bass
c) easy access to basic eq and tone controls, for adjusting recordings to taste (some have too much bass and some have too little)
d) multichannel upmixing (that's a newer development for me personally, but I increasingly find it to be indispensable)

These things make a perceivable big difference for me, whereas SINAD numbers beyond a certain threshold don't. So I'm fine with a SINAD of 80 db, for example, as long as my gear does these other things which matters a whole lot to me when it comes sound reproduction and creating musical illusions in my brain. I'll take a higher SINAD if I can get it, of course, but I don't stress with it beyond a certain level. Priority for me is gear which does the other stuff well.



This is very interesting! Cool. Would you care to share more details about the setup, what the perceived differences were, etc? I don't find it strange that you could distinguish the AHB2 from the M180 tubes, nor that you couldn't distinguish the AHB2 and the Halcro beast (both super-magnicient AB amps). But it's intriguing that you could distinguish the AHB2 and the Ncore... I would like to know more, if you care to share. (my one concession to gut-based audiophoolery is that my gut is still somewhat skeptical to class d amps. Well-performing ab amps still feels like the safer choice - possibly with the exception of purifi).

I'll try.
System: RME ADI-2 PRO FS, my own MC/line preamp design, VPI classic SE TT with Mijajima Madake cartridge, VPI 3D arm. Modified ML Montis, with the bass path separated from the path to the panels. Raspberry Pi/Volumio, HSU ULS15 Mk ii. 4' long double 12 AWG cable from amps to speakers.
The Rogues have non-stock small signal tubes- selected to make the amps sound right to me, with the input of my spouse, who has a music degree and was trained in voice. An Otari MX50 with various 15IPS tapes was also used.
All of the power amps are mine, except for the Halcro units. The Halcro comparison took place at the home of a friend in Atlanta- he has a DM10/DM68 combo and a pair of stacked quad electrostatics. I brought the RME box and the AHB2s with me. He had an analog only (LP, Tape) system.
The Rogues sounded surprisingly close to the AHB2s- the differences were mainly at the very high end where they were a bit less "bright" and when the music became loud and complex they seemed somewhat congested and the image tended to flatten. The dynamics were also a bit more constrained, they have less of the "make you jump out of your seat in surprise" quality. The noise floor was obviously higher when digital sources were used, but it was not noticeable for tape or LP. The stock tubes sounded less like the AHB2.
The Ncore amps sounded, well, dull, in comparison- softer, less dynamic. It's hard to describe, but it was, apparently, obvious.
I had a friend who unbidden made exactly that observation when I was switching between the amps casually without any prior discussion on the matter. Perhaps the issue is some matching issue with the electrostatics. I tried measuring the frequency response, but I could not find anything unexpected- small signal -3db point at, if I remember correctly, about 50kHz. I can't measure large signal behavior.
I tried both analog and hires digital for sources. The conclusions were the same.
All Amps were initially tested with square waves to ensure stability into the speakers. No oscillation or unexpectedly long settling times were noted.