• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required as is 20 years of participation in forums (not all true). Come here to have fun, be ready to be teased and not take online life too seriously. We now measure and review equipment for free! Click here for details.

Review and Measurements of Benchmark AHB2 Amp

Coach_Kaarlo

Active Member
Joined
Apr 27, 2020
Messages
114
Likes
79
Location
Sydney
Hi,

My name is Bernard and I am from Sydney, Australia. I have read all 99 pages on the Benchmark AHB2 discussion and yet I could not find any discussions of the Magnepan 20.7 being driven by the Benchmark.
Does the Benchmark have sufficient power to drive the Magnepans?

Thanking you in anticipation.

Regards
Bernard
Hi Bernard,

Where are you in Sydney. I can offer you a test drive of my amps if you aren’t too far away. You are welcome to try one, or two in mono (my preferred setup). See what you think before dropping the big dollars.

Let me know.
 

bern2a

New Member
Joined
Oct 4, 2020
Messages
3
Likes
1
My sincere thanks to all who responded to my post.

to Coach_Kaarlo,

I am in the northern suburbs and my mobile is 0413xxxx87. Thank you for your offer.

Best Regards
Bernard
 
Last edited:

RichB

Addicted to Fun and Learning
Forum Donor
Joined
May 24, 2019
Messages
989
Likes
995
Location
Massachusetts
My sincere thanks to all who responded to my post.

to Coach_Kaarlo,

I am in the northern suburbs and my mobile is 04xxxxx. Thank you for your offer.

Best Regards
Bernard
I recommend PM'ing and remove your phone number.

- Rich
 

Coach_Kaarlo

Active Member
Joined
Apr 27, 2020
Messages
114
Likes
79
Location
Sydney
My sincere thanks to all who responded to my post.

to Coach_Kaarlo,

I am in the northern suburbs and my mobile is xxx. Thank you for your offer.

Best Regards
Bernard
Number saved - will contact you later today.

I recommend PM'ing and remove your phone number.

- Rich
Good tip.
 
Last edited:

Neel

Member
Forum Donor
Joined
Oct 1, 2020
Messages
14
Likes
9
Hi everyone – I am a new member and need some advice.

For my stereo system, I use the following in my audio chain:
Auralic Aries as Roon End Point -> Minidsp SHD studio for Dirac -> Benchmark DAC3 as DAC and Preamp-> Benchmark AHB2 -> 10 ft benchmark NL2 cable -> Revel Salon 2

Recently I got a second amplifier (AHB2). Using the amplifiers in mono mode, I have felt (no measurements or any data whatsoever) the lower frequencies are not as tight as it used to be in a stereo configuration (one AHB2). I am planning to try out vertical passive bi-amping and see if there is any difference in sound (hopefully improvement).

Has anyone tried passive vertical bi-amping the Revel Salon 2s with Benchmark AHB2s and did you notice any difference? Am I supposed to get any difference from a measurement standpoint?
 

Inner Space

Senior Member
Joined
May 18, 2020
Messages
363
Likes
624
Recently I got a second amplifier (AHB2). Using the amplifiers in mono mode, I have felt (no measurements or any data whatsoever) the lower frequencies are not as tight as it used to be in a stereo configuration (one AHB2).
Hello and welcome. Used in mono, there's a halving of the amp's so-called "damping factor", which might, through interaction with the speaker's impedance characteristics, produce the effect you're hearing. Benchmark will say the numbers are such that neither usage should be a problem, but yes, there's a theoretical and measurable justification for your impressions.
 

Neel

Member
Forum Donor
Joined
Oct 1, 2020
Messages
14
Likes
9
Hello and welcome. Used in mono, there's a halving of the amp's so-called "damping factor", which might, through interaction with the speaker's impedance characteristics, produce the effect you're hearing. Benchmark will say the numbers are such that neither usage should be a problem, but yes, there's a theoretical and measurable justification for your impressions.
Thanks for the welcome and for concurring with my listening impressions.

I do like the additional power that AHB2s provide in mono mode and intend to continue using it in mono mode. However, I am looking for all ways and means to improve the lower frequencies, if I can.

Two that I have found till now:
1. Keep the speaker cable short or move the amplifiers closer to the speakers (not my preferred option - so will try it last if nothing else works)
2. Use vertical passive bi-amping - will appreciate if someone can share their experiences

3. Any advice on other techniques?
 

Inner Space

Senior Member
Joined
May 18, 2020
Messages
363
Likes
624
1. Keep the speaker cable short or move the amplifiers closer to the speakers (not my preferred option - so will try it last if nothing else works)
2. Use vertical passive bi-amping - will appreciate if someone can share their experiences
3. Any advice on other techniques?
1. Assuming your speaker cables are adequate and currently normal domestic lengths, then shortening them is very, very unlikely to make an actual audible difference.

2. Bi-amping will restore the damping factor in the bass to what it was during stereo use, so if (and it's a big if) damping factor was the cause of your dissatisfaction, then that's obviously the solution. However, you'll be wasting most of the extra power you've bought, because most demand is in the bass, where you'll be back to one channel + one channel, like you had before. The other two channels will be basically idling, in the face of HF demand, which is modest.

3. Moving your speakers by trial and error - back and forth, in and out, even a few inches here and there - will produce definite audible changes, way more than anything else, and you might find a position that works better. This is your obvious first move.
 

waynel

Addicted to Fun and Learning
Forum Donor
Joined
Nov 14, 2019
Messages
686
Likes
759
Thanks for the welcome and for concurring with my listening impressions.

I do like the additional power that AHB2s provide in mono mode and intend to continue using it in mono mode. However, I am looking for all ways and means to improve the lower frequencies, if I can.

Two that I have found till now:
1. Keep the speaker cable short or move the amplifiers closer to the speakers (not my preferred option - so will try it last if nothing else works)
2. Use vertical passive bi-amping - will appreciate if someone can share their experiences

3. Any advice on other techniques?
3). Add a pair of subwoofers and use the SHD studio as crossover and volume control. You will need another dac for the subs but a you can use a less expensive one.
 

Inner Space

Senior Member
Joined
May 18, 2020
Messages
363
Likes
624
3. Moving your speakers by trial and error - back and forth, in and out, even a few inches here and there - will produce definite audible changes, way more than anything else, and you might find a position that works better. This is your obvious first move.
Quoting myself here, because a thought struck me: did you move the speakers at all, when you installed the second amp? If you did, the obvious explanation for the differences you're hearing is that you didn't put them back in exactly the same place.
 

mafelba

Active Member
Joined
Sep 27, 2020
Messages
125
Likes
41
There is no disagreement. I am confident that there is a logical, scientific and real-world reason for what I have heard and reported. However, so far, I do not know what it is. This is one reason why I participate in forums such as this and appreciate posts such as the one above from josh358.
Fantastic
 

Sir Sanders Zingmore

Senior Member
Forum Donor
Joined
May 20, 2018
Messages
498
Likes
748
Location
Melbourne, Australia
Hello and welcome. Used in mono, there's a halving of the amp's so-called "damping factor", which might, through interaction with the speaker's impedance characteristics, produce the effect you're hearing. Benchmark will say the numbers are such that neither usage should be a problem, but yes, there's a theoretical and measurable justification for your impressions.
According to Stereophile the Revels have impedance which "….. impedance (fig.1) drops to between 3 and 5 ohms between 17Hz and 600Hz".

So another way of saying this (I think) is that the Revels will effectively present a load that will be half that (between 1.5 and 2.5 ohms).

Benchmark state that the amp is "stable into all loads" but they don't provide a power rating below 6 ohms for bridged mono operation
 

mafelba

Active Member
Joined
Sep 27, 2020
Messages
125
Likes
41
I tend to lean the other way... give me sources, preamps, and amps that allow the least possible colouring and work with loudspeakers and spaces to achieve the necessary effect.
I've been reading a lot of posts here at ASR and quite often this debate comes up: coloration vs transparency. I am still not persuaded either way and I will tell why. Regarding transparency: transparency would be king IF the source was a decent VERSION of sound as our ears hear it. But, unfortunately, 99.9% of recorded audio does not sound anything like what we would hear in a live setting. And when I use the word "live", I don't mean live music, I mean the way an acoustic guitar sounds to us when it is being strummed 3 feet away from us, or what a human voice sounds like to our ears when someone is in the same room. Something is WRONG with recording music. It's WAY OFF and I don't think any honest person could conclude otherwise. Why should we care so much about transparency when the underlying recordings sound nothing like what we hear live? Recorded music does not sound realistic and that is just the sad fact that all of us who are interested in great sound have to deal with. Of course there are a few recordings which do come close, through painstaking effort, but even those recordings fall incredibly short in reproducing the PRESENCE that we hear naturally with our ears when instruments are played near us. For whatever reason, and someday they will figure it out I'm sure, music reproduced and played is FLAT and sandwiched and missing a very important something that we have not yet defined or understood. The difference in sound perceived vs sound recorded of 4 people playing bass, drums, guitar and singing in your bedroom vs coming out of your speakers is STAGGERING and almost reside in totally different worlds. Yet, we just move on, accept it, and strive for faithful reproduction - what else could we do? Nothing.

There were two times in my life where I could not believe the sound that was coming out of speakers. The first time was 15 years ago when I played a children's video game on my computer for my 4 year old out of $15 computer speakers. My jaw dropped and I thought to myself - whoever produced this music for this silly video game must be a genius and knows something that nobody else knows. I became hopeful that finally we were on the cusp of some advent in audio. At the time, I had VTL amps and preamp and Meadowlark Kestrel Hot Rods and I knew, at least to some extent, what sound quality components could produce, so I wasn't exactly a novice. The second time I heard music emanate from speakers and my jaw dropped was just a couple of months ago, through my mid-level system, again with a video game as I loaded Animal Crossing on the nintendo switch and the intro played (via analog out on my TV!). Again, I could not believe the sound. Now, I am not suggesting that either of these events approaches the presence that we hear naturally and which is missing from 99.9% of recordings; the point is that these 2 events showed me just how bad and far from this natural presence your average audio recording is. So again, why are we so concerned about transparently recreating this incredibly bad, almost pathetic, representation of sound?

So, to color or not to color, that is question. I guess where I come down on it is that whatever approach makes the music sound more real to me is what I want. I don't care if its transparent or colored and I'm not experienced to know whether or not coloration brings us any closer to the realistic sound that I've been referring to - but I think we should be open to the possibility. Our music sources are NOT realistic representations of what we hear and feel and anything that can help these poor representations sounds more realistic, I would support and want to purchase.
 

RichB

Addicted to Fun and Learning
Forum Donor
Joined
May 24, 2019
Messages
989
Likes
995
Location
Massachusetts
Thanks for the welcome and for concurring with my listening impressions.

I do like the additional power that AHB2s provide in mono mode and intend to continue using it in mono mode. However, I am looking for all ways and means to improve the lower frequencies, if I can.

Two that I have found till now:
1. Keep the speaker cable short or move the amplifiers closer to the speakers (not my preferred option - so will try it last if nothing else works)
2. Use vertical passive bi-amping - will appreciate if someone can share their experiences

3. Any advice on other techniques?
I vertical bi-amp my Salon2s with AHB2s and I have a friend who also bi-amps. Another friend bridges the AHB2s to drive the Salon2s because he wants additional output.

The AHB2s have accurate clipping indicators per channel so it is clear when you are clipping. I was surprised that when listening to music and watching movies very loud that my amps were not clipping. I have measured two Salon2s in my room at 2 watts (2.83 volts) into 4 Ohms at 86 dB. 128 watts produces 104 dB which is more than enough for me.

Bi-amping does not waste significant power if you don't use it. Many think that the purpose is to gain power and it does not. From my tests, I get about 1 dB of headroom by bi-amping.

I have performed multiple single-blind tests using using a Single Salon2 (as does Harman) using the following procedure:

- Remove the straps from the Salon2s
- Make a short (about 10") banana plugs patch cord to single amp
- Split the source from your processor using a Y cable (I did not use built-in bi-amping in the AVP to avoid possible side-effect).
- Run both bi-amp output channels to a single Salon2
- Play familiar tracks at -30 that is the mid 80 dB range that is approximately 3 watts on my system
- Working behind the speaker (out of sight), switch between the patch (single amped) and the other channel (bi-amped).
- Take care to not short the unused amp (I had a rug under my speaker that I used for this purpose)
- Play short passages of songs, preferable with J River, Roon, or other streamer to allow quick replay and comparison.

3 of us had no trouble identifying single versus bi-amped.
There is no level matching issue in such a test.
I can only speculate that the reason but it may be that the separation of the crossovers reduces distortion.
Kevin Voecks (of Harman) was attributed on AVR saying the bi-amping may improve clarity.

Of all the tweaks that folks try in their system, this is very inexpensive experiment.
Try it with one speaker, and you need only a XLR splitter cable and a small patch cable.
If you find a benefit in SBTs or not, you will have your answer.

- Rich
 

RichB

Addicted to Fun and Learning
Forum Donor
Joined
May 24, 2019
Messages
989
Likes
995
Location
Massachusetts
So, to color or not to color, that is question. I guess where I come down on it is that whatever approach makes the music sound more real to me is what I want. I don't care if its transparent or colored and I'm not experienced to know whether or not coloration brings us any closer to the realistic sound that I've been referring to - but I think we should be open to the possibility. Our music sources are NOT realistic representations of what we hear and feel and anything that can help these poor representations sounds more realistic, I would support and want to purchase.
Start with transparent components and then, season to taste. Don't buy components that are "salty" because you once it is added it cannot be removed.
DSPs are the seasoning you are looking for.

- Rich
 

mafelba

Active Member
Joined
Sep 27, 2020
Messages
125
Likes
41
Start with transparent components and then, season to taste. Don't buy components that are "salty" because you once it is added it cannot be removed.
DSPs are the seasoning you are looking for.

- Rich
Thanks. Don't know anything about DSP's but will certainly take a look.
 

RayDunzl

Major Contributor
Central Scrutinizer
Joined
Mar 9, 2016
Messages
10,851
Likes
10,361
Location
Riverview FL
I can only speculate that the reason but it may be that the separation of the crossovers reduces distortion.
Ir occurred to me recently, which I don't remember seeing mentioned before (I get to be wrong) that removing the strap changes the impedance of the speaker as presented to the amplifier.

My speakers are specified as 4 ohm, and measures that with an ohmmeter (they go all over the place with AC, but lets ignore that for a moment).

With the strap removed, the woofer and the tweeter independently measure 8 ohms.

That shouldn't be a surprise, but it isn't something I remember seeing in bi-amping discussions.
 
Last edited:

bigguyca

Active Member
Joined
Jul 6, 2019
Messages
258
Likes
354
Ir occurred to me recently, which I don't remeber seeing mentioned before (I get to be wrong) that removing the strap changes the impedance of the speaker as presented to the amplifier.

My speakers are specified as 4 ohm, and measures that with an ohmmeter (they go all over the place with AC, but lets ignore that for a moment).

With the strap removed, the woofer and the tweeter independently measure 8 ohms.

That shouldn't be a surprise, but it isn't something I remember seeing in bi-amping discussions.
You are likely measuring DC resistance. The crossovers have inductors and capacitors in the signal path and the AC impedance, which is the quantity of interest will be different than the DC resistance.

As an example: A very simple crossover to a tweeter is just a capacitor in series with the high frequency driver. The resistance of the crossover to DC will be infinite due to the (ideal) capacitor, but the AC impedance will decline with increasing frequency as the impedance of the capacitor drops and the impedance measured approaches the impedance of the high frequency driver.

The AC impedance of loudspeakers typically varies greatly with frequency do to complex interactions between the crossover components and the drivers.
 

bigguyca

Active Member
Joined
Jul 6, 2019
Messages
258
Likes
354
Misc. Thoughts: Bi-amping, Salon2's and Audio Quality

Audio Quality

The measurements of loudspeakers in ASR have confirmed what has been known for a long time. Loudspeakers are the weak link in most systems. Some loudspeaker companies IMNVHO appear to make no speakers that are really good. It seems likely that many people listen to speakers that are average and average isn't really very good. This unfortunate opinion applies at least as much to companies that make expensive and very expensive speakers. Many "Bad" recordings can be rescued with excellent speakers. In other words, it wasn't the recording, it was the speakers.

Salon2's are mentioned a lot here, and you'll notice that many people ultimately purchase a pair and are set for speakers. The design of the Salon2's is excellent in many ways.

Bi-amping

Salon2's seem particularly good choices for bi-amping since it appears bi-amping divides the three bass drivers at about 150 Hz from the other "three-way" of the four-way Salon2. This means that both halves of the driving amplifier are driving significant loads. Other speakers where the crossover is at 500 Hz or even 1,000 Hz put a heavier load on the bass amplifier.

The bass drivers of the Salon2 are likely to generate most of the distortion. Even with fourth order crossovers some of this distortion will still find its way to the next driver. Bi-amping prevents this transfer. The low bass crossover frequency helps here as well. A high crossover would have this distortion affecting overall performance of a single driver to a much higher frequency.

As with any bi-amping, the effective impedance overall seen by each amplifier should be higher than is seen for the entire speaker. The voltage into each half of the crossover stays the same, but the current supplied to each half drops. (grossly, V/I = impedance). This means that the effective impedance seen by each power amplifier in a bi-amp setup increases. This effect is especially beneficial for the Salon2 since the impedance is low at many points.

This increased impedance effect is helpful when an AVR is used for bi-amping since any steps to increase the impedance seen by these far less than perfect amplifiers is helpful. The higher impedance load also increases the voltage gain of the output stage of a power amplifier. This should decrease crossover distortion, especially for AVR power amplifiers that have only one pair of output transistors. Bi-amping also spreads the heat generated by internal power amplifiers in an AVR to more of the heat sink so the AVR should run cooler. These sorts of effects are most important for lesser amplifiers.
 
Top Bottom