Review and Measurements of Benchmark AHB2 Amp

[Olli]

Thanks for the info. I'm strongly considering the AHB2 but the DAC3 HGC is not in the cards (I already have the RME ADI-2 DAC). Generalizing, I take the recommended solution is to just use one's DAC or pre-amp. Fair enough.

You could trade in your ADI 2 for an ADi 2 Pro FS which is a 8 CH DAC with 4 analogue outs. I use it with 2 AHBs and 2 Subs. Crossovers and REQ are done with a software called Audiolense. Generated Filters are apllied in Roon's convolution engine (or could alternatively loaded into JRiver). Very easy setup that sounds and measures great.

2 caveats: This setup works only for Digital media and you'll have digtal volume control within Roon/JRiver.

 

[Mikechw]

Hi, i just bought a ahb2 last month and thinking of getting a 2nd one to pair it up as mono blocks.

Just wonder if i can used them as dual mono blocks. Left channel to drive high frequencies and right channel to drive low. Just set the dip switch on the back to bridge. And reversing the polarity of one channel. I suppose the black terminals on the back is the ground channel.

Then i dont need to use a split cables for the input.

 

[anmpr1]

...wonder if i can used them as dual mono blocks. Left channel to drive high frequencies and right channel to drive low. Just set the dip switch on the back to bridge. And reversing the polarity of one channel. I suppose the black terminals on the back is the ground channel. Then i dont need to use a split cables for the input.

Before you do something unusual with your expensive amp, you might want to consider calling Benchmark support and discussing your plan. Why wouldn't you do that?

 

[RichB]

Hi, i just bought a ahb2 last month and thinking of getting a 2nd one to pair it up as mono blocks.

Just wonder if i can used them as dual mono blocks. Left channel to drive high frequencies and right channel to drive low. Just set the dip switch on the back to bridge. And reversing the polarity of one channel. I suppose the black terminals on the back is the ground channel.

Then i dont need to use a split cables for the input.

Here is my recommendation to bi-amping with a Single Blind Test (SBT):

• Listen to only one speaker for SBT (Harman does this in the DBT's)
• Split the signal using a XLR Y splitter cable
• Remove the straps from the speakers
• Wire on speaker section with stacking banana plugs
• Run two sets of speaker cables to a speaker
• Make an 8" (or so) patch cable to connect the upper and lower sections
• Have someone switch between connecting the second speaker cable (bi-amp) and the patch cable (single amp)
• Play a selection of music, female vocal work well for me (Celtic Women)

This methodology provides for quick switching and has a low risk of connecting the amps together.

Here are some very nice Locking stacking banana plugs:

https://www.parts-express.com/angle...s-poly-shell-and-insulated-thumbscr--091-3608

I have done this many times and find that bi-amped has better clarity at low volume. I can only assume that there is a benefit by disconnecting the passive crossovers. YMMV.

With the AHB2's all options are open if you buy two (or more)

- Rich

 

[DonH56]

Hi, i just bought a ahb2 last month and thinking of getting a 2nd one to pair it up as mono blocks.

Just wonder if i can used them as dual mono blocks. Left channel to drive high frequencies and right channel to drive low. Just set the dip switch on the back to bridge. And reversing the polarity of one channel. I suppose the black terminals on the back is the ground channel.

Then i dont need to use a split cables for the input.

I don't fully understand what you are trying to do but am pretty sure what you are describing will not work. To use both channels you should not use the bridging switch. That will turn them into monoblocks, true, but then each amp is a one-channel amp, one amp per speaker (full range). And no need to reverse one channel. No output is ground if you bridge the amplifier. Read the manual.

 

[STUDIO51]

Hi, i just bought a ahb2 last month and thinking of getting a 2nd one to pair it up as mono blocks.

Just wonder if i can used them as dual mono blocks. Left channel to drive high frequencies and right channel to drive low. Just set the dip switch on the back to bridge. And reversing the polarity of one channel. I suppose the black terminals on the back is the ground channel.

Then i dont need to use a split cables for the input.

Available. I am also using that method. see HERE

I asked @John_Siau if this method would cause problems for ahb2. He replied that there was no problem.


John said : "Crosstalk is never an issue with the AHB2. There will be no audible crosstalk from the AHB2 in any system configuration.

Instead the goal should be to place the same load on both amplifier. Most of the power will be consumed by the low-frequency channel. Because of this, you want to combine one low frequency channel with one high frequency channel in each amplifier. When this is done, the system will achieve the highest possible headroom.

Use one amp for the left speaker and the other for the right speaker. This will put the same load on both amplifiers. There will be no interaction between the high-frequency channel and the low frequency channel because crosstalk is non-existent in the AHB2. The regulated power supply rails in the AHB2 help to make this possible.

I would suggest running the high frequency on channel 1 and the low frequency on channel 2. This is a safer configuration if someone accidentally flips the stereo-mono switch. If mono mode gets turned on, the high-frequency signal will go to both drivers and this will not hurt the low-frequency driver. This channel assignment will prevent accidental routing of the low frequencies to the high-frequency driver (which could be damaging).


I used this method because I use a JBL M2 which requires a 4ch amplifier because there is no built-in crossover. But even ordinary speakers with crossovers will work same.

 

[Mikechw]

Well thank you for the quick replies...

Actually I am very happy with the sound (one AHB2). My speakers are capable of 200W@86dB-SPL.
My living room is not very big and 100W is more than I need.

Just wonder if the SQ will be better if I do vertical bi-amp with 2x AHB2. I am running at mid GAIN settings on the AHB2.

Does this Y-split cable look ok ?
https://www.amazon.com/dp/B07H7QS8K...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

 

[anmpr1]

I asked @John_Siau

Use one amp for the left speaker and the other for the right speaker. This will put the same load on both amplifiers. There will be no interaction between the high-frequency channel and the low frequency channel because crosstalk is non-existent in the AHB2. The regulated power supply rails in the AHB2 help to make this possible.

So you are using an active crossover to split the frequency band. Out of curiosity, how do you find the dbx, noise wise, integrating with the low noise AHB2? Any perceived S/N degradation?

 

[STUDIO51]

Apparently pa2 is a weak point in my system. As you can see here , I'll replace it with a digital I/O dsp. I'm listening M2 at a distance of about 2m. The room is quite quiet but it is impossible to hear the noise at LP. Ears should be attached to the waveguide to hear noise.

But according to my own measurements, the distortion of pa2 is quite serious. So it must be replaced.

 

[STUDIO51]

Well thank you for the quick replies...

Actually I am very happy with the sound (one AHB2). My speakers are capable of 200W@86dB-SPL.
My living room is not very big and 100W is more than I need.

Just wonder if the SQ will be better if I do vertical bi-amp with 2x AHB2. I am running at mid GAIN settings on the AHB2.

Does this Y-split cable look ok ?
https://www.amazon.com/dp/B07H7QS8K...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

If the sound level is not low, you do not need to buy an additional amplifier.

 

[Mikechw]

Thanks, my next step may be having my room EQd.. I have downloaded REW, a Behringer ECM8000 microphone and ordered a Behringer U-PHORIA UMC202HD. It may take some time to learn how to use REW.
Roon is installed on my computer with a evaluation copy of HQPlayer.. (HQPlayer DSD upscale does sound better than Roon's upscaler)
Computer is connected to RME-ADI2 Pro FS via USB..
RME is then fed to Accuphase E-480 then to Benchmark AHB2.
I prefer the sound of AHB2 better than E-480. I am keeping my E-480 as my pre-amp because I am still using a SACD player as a source.

 

[Matias]

Thanks, my next step may be having my room EQd.. I have downloaded REW, a Behringer ECM8000 microphone and ordered a Behringer U-PHORIA UMC202HD. It may take some time to learn how to use REW.
Roon is installed on my computer with a evaluation copy of HQPlayer.. (HQPlayer DSD upscale does sound better than Roon's upscaler)
Computer is connected to RME-ADI2 Pro FS via USB..
RME is then fed to Accuphase E-480 then to Benchmark AHB2.
I prefer the sound of AHB2 better than E-480. I am keeping my E-480 as my pre-amp because I am still using a SACD player as a source.

This REW tutorial is fantastic. Not sure which EQ setting you would need to choose to export to Room, but Google surely has the answer.

 

[Roasty]

This REW tutorial is fantastic. Not sure which EQ setting you would need to choose to export to Room, but Google surely has the answer.

I use a different method to use REW which I found on the roon community site.

https://community.roonlabs.com/t/a-guide-how-to-do-room-correction-and-use-it-in-roon/23800

Has anyone tried both? And is there any obvious advantage/disadvantage to either?

After rew using the method on Roon, bass sure has tightened up a lot and is punchier and more textured. All of the boominess has gone away. I did it with my lounge setup and, goodness me, realized I had been listening to music "wrong" all this time..

 

[EVOLVIST]

Well thank you for the quick replies...

Actually I am very happy with the sound (one AHB2). My speakers are capable of 200W@86dB-SPL.
My living room is not very big and 100W is more than I need.

Just wonder if the SQ will be better if I do vertical bi-amp with 2x AHB2. I am running at mid GAIN settings on the AHB2.

Does this Y-split cable look ok ?
https://www.amazon.com/dp/B07H7QS8K...jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==

What make and model speakers do you have? I had a ABH2 trying to drive my Egglestonworks Andra IIs and I felt the amp lacked the balls to really grab hold and drive them.

I'm not dogging the amp. I was told well after the fact that I should have has two, running as monoblocks, to really give my speakers enough umph.

 

[Mikechw]

What make and model speakers do you have? I had a ABH2 trying to drive my Egglestonworks Andra IIs and I felt the amp lacked the balls to really grab hold and drive them.

I'm not dogging the amp. I was told well after the fact that I should have has two, running as monoblocks, to really give my speakers enough umph.

I have a pair of Pioneer S-2EX Monitors.
https://hometheaterhifi.com/reviews/speaker/bookshelf/pioneer-s-ex2-speakers/

Sensitivity is 86.5 dB
The tweeter spec can drive up to 100khz.
I have tried other class D and class A/B amps.
Class D seems always sound a little better. (more control)
But finally I have settled and paired it with AHB2. (may be other A/B's damping factor is a little low)

 

[Sal1950]

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

 

[restorer-john]

Sal, you're pretty much on the money with 200W/ch. It covers pretty much all speakers and allows for a decent reserve should you need it.

With my various vintage power amplifiers, I settle on the 200W/ch ones. I have a pair of big Sony TAN77es which can be put into bridged mono if I really feel like it. I've done it a few times, but it's unnecessary. That give 580W/ch@8 and nearly 1KW@4R per channel. Silly stuff.

 

[EVOLVIST]

Yeah, the 200W rule of thumb has always been my um...yeah, rule of thumb. I think you'd need to run AHB2 in bridged mono to get some real grunt out of them.

 

[wynpalmer]

What make and model speakers do you have? I had a ABH2 trying to drive my Egglestonworks Andra IIs and I felt the amp lacked the balls to really grab hold and drive them.

I'm not dogging the amp. I was told well after the fact that I should have has two, running as monoblocks, to really give my speakers enough umph.

I have a pair of AHB2s driving a pair of ML electrostats, which incidentally is the same set up as Benchmark uses in their show appearances.
Theoretically, a single AHB2 has almost enough drive for the speakers which are rated at 200W (500W max) into 4 ohms (the amp is rated at 190W/ch into 4 ohms). However, the reality is that the clip indicators would flash periodically with a single stereo unit when large amounts of bass is required- even though the speakers actually take care of that part of the spectrum themselves- and somehow there was a sense of strain in loud passages which no longer exists in the dual mono case. The speakers are rated, I believe at 91dB/2.83v/1m, but seem to measure at about 90.
Additionally, looking at the load waveform into the electrostatics on an oscilloscope, there were times when the output current limiting kicked in for the stereo unit, causing the edge of the signal to ramp rather than to smoothly transition both to and from peaks, presumably due to the capacitive load. That ramping no longer occurs in the dual mono pair installation, presumably due to the not quite doubling of the maximum transient current.
It's easy to argue that none of this should matter, but an admittedly non ABX purely subjective observation by myself and others is that we think it does...

 

[anmpr1]

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.

I think that's about right. The only exception might be smallish shoe box sized 'mini monitor' speakers, which ought not really be considered 'full range', and are hardly ever capable enough to 'come alive and rock', in the SPL department.

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.