Review and Measurements of Benchmark AHB2 Amp

[PASOKO]

Coil whine is really bad, I talked about coil squeal in the D90SE thread, but this one is 10 times worse. No matter how good the SINAD measured from the terminals and the SNR that affects it, this is a speaker amp, and what you actually hear is not much different than a $30 amp with a lot of white noise. It's really bad. I never had this problem with my PM6006.
It's not super high frequency this time, maybe 1 kHz? Very unpleasant, and I'd say the power supply circuit is incomplete. Please mention it when you take measurements.
Normally, this test should not be necessary since the AHB2 is supposed to filter out noise. However, I tried unplugging all the power from the same breaker and putting in a power distribution board with a noise filter. It didn't help, and I am convinced that the problem is with the AHB2 itself.

Do you think it is defective product ?
Or is it the same with your AHB2?
I've contacted the distributor.

*I'm not a coil whine fanatic.

 

[DonH56]

I'd contact benchmark directly. Sounds like a defective amp.

Is it coming from the amp itself ("coil whine" is usually a physical vibration) or the speakers?

 

[josh358]

Coil whine is really bad, I talked about coil squeal in the D90SE thread, but this one is 10 times worse. No matter how good the SINAD measured from the terminals and the SNR that affects it, this is a speaker amp, and what you actually hear is not much different than a $30 amp with a lot of white noise. It's really bad. I never had this problem with my PM6006.
It's not super high frequency this time, maybe 1 kHz? Very unpleasant, and I'd say the power supply circuit is incomplete. Please mention it when you take measurements.
Normally, this test should not be necessary since the AHB2 is supposed to filter out noise. However, I tried unplugging all the power from the same breaker and putting in a power distribution board with a noise filter. It didn't help, and I am convinced that the problem is with the AHB2 itself.

Do you think it is defective product ?
Or is it the same with your AHB2?
I've contacted the distributor.

*I'm not a coil whine fanatic.

What Don said, I haven't had any coil whine at all. Dead silent in every respect.

 

[RPG]

What Don said, I haven't had any coil whine at all. Dead silent in every respect.

Same here....first amp I've had where there's not even a hint of speaker hiss.

 

[cany89]

Hi All! I don't really understand amp specs vs speaker specs. Can someone tell me if this amp will sound good with a pair of JBL750i?
- If I need 2x AHB2 or not? And if needed, again can they be used with these speakers on mono mode...

I also heard with some speakers it doesn't sound that good. I probably can't try it before buying, is there any way to understand it? Or has anyone used it with similar speakers?

Thanks a lot!

(Here are the specs of JBL LSR750i)

 

[levimax]

Hi All! I don't really understand amp specs vs speaker specs. Can someone tell me if this amp will sound good with a pair of JBL750i?
- If I need 2x AHB2 or not? And if needed, again can they be used with these speakers on mono mode...

I also heard with some speakers it doesn't sound that good. I probably can't try it before buying, is there any way to understand it? Or has anyone used it with similar speakers?

Thanks a lot!

(Here are the specs of JBL LSR750i)

Why not just use the "recommended amplifier" ? It is perfect match and works seamlessly. You can use one or two of the AHB2 but you are going to have to buy and configure the separate "sound processor" which if you are not technical may be difficult. It will also make it difficult to impossible to listen before you buy.

 

[Sal1950]

Hi All! I don't really understand amp specs vs speaker specs. Can someone tell me if this amp will sound good with a pair of JBL750i?
- If I need 2x AHB2 or not? And if needed, again can they be used with these speakers on mono mode...

I also heard with some speakers it doesn't sound that good. I probably can't try it before buying, is there any way to understand it? Or has anyone used it with similar speakers?

Thanks a lot!

(Here are the specs of JBL LSR750i)

You seem to have your model numbers confused, AFAIK there in not a LSR750i, only 705/708 models exist.
The pdf tells you if you use any other amp besides the Crown you will have to include a Harman BSS Soundweb London Processor, which is a digital frequency response correction system. Driving it with the AHB2 but without the processor, the speaker wound not sound at all right. Also they recommend 300 wpc so a pair of the amps in bridged mode would be the way to go.
I'm not sure I could justify this level of expense for this speaker, you could make better choices at this dollar level. IMHO
YMMV

 

[cany89]

You seem to have your model numbers confused, AFAIK there in not a LSR750i, only 705/708 models exist.
The pdf tells you if you use any other amp besides the Crown you will have to include a Harman BSS Soundweb London Processor, which is a digital frequency response correction system. Driving it with the AHB2 but without the processor, the speaker wound not sound at all right. Also they recommend 300 wpc so a pair of the amps in bridged mode would be the way to go.
I'm not sure I could justify this level of expense for this speaker, you could make better choices at this dollar level. IMHO
YMMV

I’m using these speakers with 2x Nad C270 and don’t know if they sound off. I also have Chord SPM 400, which I also liked but it’s connected to other setup atm.

I can apply EQ on dac or pc, do I still need DSP unit? Or specific Crown amp? What’s wrong with using these without dsp? - are they not somehow calibrated out of the box for basic use?

 

[cany89]

You seem to have your model numbers confused, AFAIK there in not a LSR750i, only 705/708 models exist.

Sorry it’s 705i

 

[cany89]

Why not just use the "recommended amplifier" ? It is perfect match and works seamlessly. You can use one or two of the AHB2 but you are going to have to buy and configure the separate "sound processor" which if you are not technical may be difficult. It will also make it difficult to impossible to listen before you buy.

I know the brand but never heard any amps - let alone pro versions - in person. I was just using these speakers with usual hifi amps. I’ll check the amps listed in pdf but I don’t know, shouldn’t there be a difference between these studio amps and amps I use like Nad, Chord, Denon, etc.?

 

[cany89]

@Sal1950 I found the dsp settings required for 705i, if I apply these, can I use it with any amp?

 

[levimax]

I know the brand but never heard any amps - let alone pro versions - in person. I was just using these speakers with usual hifi amps. I’ll check the amps listed in pdf but I don’t know, shouldn’t there be a difference between these studio amps and amps I use like Nad, Chord, Denon, etc.?

Pro amps tend to be cheaper and more reliable and in this case the recommended amps have the features and power required to work with the speakers as designed and tested by JBL. The disadvantages of pro-amps is that they may have fans and their SINAD may be a little lower than some "Hi-Fi" amps but it is doubtful anyone could hear any difference. The most reliable and probably cheapest way to go is with the recommended amps.... if you like to tinker and tweak then mixing and matching would be more fun.

 

[cany89]

The disadvantages of pro-amps is that they may have fans

You are absolutely right, it has a fan. And in the pdf, they recommend 2x amps. They are about $2000 so it's $4000. Now that I have the required metrics for DSP, I think I can use any amp anyway...

 

[Rottmannash]

Too bad. There is an audible difference which is easy to hear and for which I cannot account logically. I have confirmed it, so far, with three different loudspeaker systems. To deny it would be dishonest on my part. Drop in some time, I will demonstrate it to you.

(Frankly, I was not going to bring it up here for obvious reasons but, when josh358 raised the issue, I felt it necessary to concur.)

Do you prefer listening to the AHB2 or the A21?

 

[Kal Rubinson]

Do you prefer listening to the AHB2 or the A21?

The Benchmark but not to a degree where I'd make that the issue. When I reviewed the A21, I already owned the Benchmarks and had no reason to change. Had that comparison occurred before I purchased the Benchmarks, I still would have chosen them over the Parasound because of their advantage in size and weight.

 

[pma]

Oh common Kal. Please record them side by side and upload it to youtube so we can compare. I promise I will keep my eyes closed to avoid placebo effect.

You must be joking. Nothing can be said from youtube compressed sound at this level. And I hope you were not suggesting to use a microphone. Even if you used a good ADC, it would be probably pointless test.

 

[pma]

The Benchmark but not to a degree where I'd make that the issue. When I reviewed the A21, I already owned the Benchmarks and had no reason to change. Had that comparison occurred before I purchased the Benchmarks, I still would have chosen them over the Parasound because of their advantage in size and weight.

My guess: Parasound would have a bit less "defined" (less accurate) sound however maybe a bit "smoother" and "fuller" than the Benchmark.
?

 

[Kal Rubinson]

My guess: Parasound would have a bit less "defined" (less accurate) sound however maybe a bit "smoother" and "fuller" than the Benchmark.
?

Yes but not consequentially.

 

[pjug]

You must be joking. Nothing can be said from youtube compressed sound at this level. And I hope you were not suggesting to use a microphone. Even if you used a good ADC, it would be probably pointless test.

I'm not sure it would be pointless to try recording amp output voltage through a divider into a good ADC, and compare. I started a thread where I tried this myself but in that case it does look like it may be pointless with the cheapo ADC I'm using.

 

[Rottmannash]

The Benchmark but not to a degree where I'd make that the issue. When I reviewed the A21, I already owned the Benchmarks and had no reason to change. Had that comparison occurred before I purchased the Benchmarks, I still would have chosen them over the Parasound because of their advantage in size and weight.

Thanks for the reply. Am considering the AHB2 and have heard good things about the A21 and wondered which amp you preferred and why.