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Is the Benchmark AHB2, in mono mode, really better than my Mark Levinson No. 536 monoblocks?

LTig

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AHB2: Another 40th anniversary speaker tests, this time with Dynaudio Special 40s: and my test measurement ears hard at work. LoL
I'm going to focus on previous comments made by others with regards to my perceived Left-Right improvement scenario that I earlier reported after going dual "mono" with my AHB2s.

1. In stereo mode, My Dynaudio SP40 provide good bass, but the soundstage is blasé relative to the Triangles Comète speakers.
The Dyns and the Triangles are doing different things. I love them both but for different reasons.
2. With the dual mono AHB2s powering the Dyns, there is a "huge" improvement in soundstage as compared to one AHB2 in stereo mode.
I give the edge to the Comètes for Soundstage (both in stereo and dual mono mode), but the Dyns are now very close and they provide a deeper bass response.
3. There is clearly more bass in dual mono mode. This is easily evident with Dave Brubeck's Take Five CD that I was using as reference material tonight.
4. The sound is more forward and present with more detail, as perviously reported.
This was noted with the Comètes. And those Pianos, oh my! And the brass instruments, oh my!

5. The Left-Right imaging is much better with the dyns in mono mode, and they better the Triangles in this manner as well. An easy improvement to report with the Dyns.
If the amplifiers offer no better specifications in dual mono operation from what is being reported, I have to come up with an explanation for what I am hearing!

So here goes a theory: there is so much more detail coming through, a more forward presentation and a wider soundstage, that certain sounds or instruments that remain in the background in stereo mode get projected to the front in a disproportionate manner in mono bloc operation. This impact is more easily discernible with the Dynaudio speakers.
One cannot base a theory on experimental results which were taken using known flawed methods.
 

mkt

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I started with one AHB2. The clipping light would come on for mid-bass heavy content at high volume. So for probably psychological reasons, I added a second. No more clipping light, and no difference that I could tell. (Not easy to do a quick switch, let alone a blind one with volume matching).

PS. (I'm selling them now to further try out the "active lifestyle")
 

sarumbear

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I started with one AHB2. The clipping light would come on for mid-bass heavy content at high volume. So for probably psychological reasons, I added a second. No more clipping light, and no difference that I could tell. (Not easy to do a quick switch, let alone a blind one with volume matching).
The clipping is as objective as it gets for sound quality. Why do you think it’s psychological?

AHB2 is such a transparent amplifier that it’s not possible to hear the difference between single or bridged modes. Hence, it’s expected that you can’t tell.

In short: your speakers required higher power than a single AHB2 channel can supply and you, correctly, doubled the power capacity. There was no audible difference, which was expected.
 
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mkt

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The clipping is as objective as it gets for sound quality. Why do you think it’s psychological?

AHB2 is such a transparent amplifier that it’s not possible to hear the difference between a single or bridged mode. Hence, it’s expected that you can’t tell.

In short: your speakers required higher power than a single AHB2 channel can supply and you, correctly, doubled the power capacity. There was no audible difference as expected.
Psychological in the sense that I noticed the clipping light not a sound quality problem, and I don’t listen that loud often. Psychological need for power?:)
 

sarumbear

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Psychological in the sense that I noticed the clipping light not a sound quality problem, and I don’t listen that loud often. Psychological need for power?:)
Sorry to argue but your need of power was physical, there was no human notion involved. Amplifier was clipping, hence was producing more distortion than its specified. You had an indisputable, physical need for power - from the amplifier. :)
 

mkt

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Sorry to argue but your need of power was physical, there was no human notion involved. Amplifier was clipping, hence was producing more distortion than it’s specified. You had an indisputable, physical need for power - from the amplifier. :)
Validation accepted. I think this covers my *need* for better measuring speakers too :)
 

sarumbear

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Validation accepted. I think this covers my *need* for better measuring speakers too :)
I urge you to start auditioning speakers while the ATC love is high, pushing the used prices up.
 
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The difference almost certainly has nothing to do with DF as in either case, stereo or mono, the DF on the AHB2 is more than adequate. Instead the difference is coming from essentially quadrupling the power. DF is the ratio of the impedance of the load divided by the impedance of the source. The impedance of the AHB2 is very low. When you bridge then the load sees two source is series, and therefore the impedance is doubled and the DF is cut in half. But it’s so high to begin with that this doesn’t affect the sound.
Agree.
 

pogo

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Instead the difference is coming from essentially quadrupling the power.
However, this is not an explanation if the low frequency range has changed even at low volumes.
 

RichB

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However, this is not an explanation if the low frequency range has changed even at low volumes.

I think we have been through is well trodden topic on this thread.
Many posts have been presented about the impact and math for computing damping factor.
Benchmark has a DF article and provides a spreadsheet.

Here is a post from a user on this thread that analyzed the damping factor of his/her system using the Benchmark spreadsheet:


- Rich
 
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However, this is not an explanation if the low frequency range has changed even at low volumes.
Generally speaking, the impact on Damping Factor will alter the low resonant frequency of the drive system (I've had the opportunity to measure stuff like that with a work colleague with test equipment way back when). It may impact the phase of the audio through the system as well (this I've never measured, things like group delay).
Damping Factor is all well and dandy, and the minute I hook up my speaker cables, the damping factor should take a hit (I'm using the Benchmark cables with NL2 connectors).

So here's a perspective:
1) hook up your speaker cables and measure the Damping Factor with cables attached in stereo mode.
2) Bridge the amp and repeat the measurement.
I am more than expecting that the change will be so small that the impact on the sound would be minimal; at least to my ears.

How this impacts the sonic signature and is perceptively heard is beyond me. The extra power and impact to the system has changed, I note the changes through my filter and report them.
As I stated, there seems to be more bass, but it is very subtle; it could even be that the bass frequency is the same but the woofer is just receiving more energy.
If bass was the only reason to 'bridge', I'd save my $$ and keep the amplifier in stereo mode and call it day.
Alternatively, the results I note going to "bridged mode" or 'mono mode' surprised the heck out of me: I was expecting more power, more slam, more volume in a high level kinda way; I noted more air, more presence and more fluidity and a wider soundstage (depending on material used). It's a more sophisticated sound all around.

Makes me wonder how a small rated amp like Schitt Aegir would respond in 'Bridged mode'; which has many fans on other forums as well. In Canada, quantity x2 Schitt Aegir is starting to get up there in price due to exchange rates and makes me wonder: should I take a punt and try it for my second system?
 

PGAMiami

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Generally speaking, the impact on Damping Factor will alter the low resonant frequency of the drive system (I've had the opportunity to measure stuff like that with a work colleague with test equipment way back when). It may impact the phase of the audio through the system as well (this I've never measured, things like group delay).
Damping Factor is all well and dandy, and the minute I hook up my speaker cables, the damping factor should take a hit (I'm using the Benchmark cables with NL2 connectors).

So here's a perspective:
1) hook up your speaker cables and measure the Damping Factor with cables attached in stereo mode.
2) Bridge the amp and repeat the measurement.
I am more than expecting that the change will be so small that the impact on the sound would be minimal; at least to my ears.

How this impacts the sonic signature and is perceptively heard is beyond me. The extra power and impact to the system has changed, I note the changes through my filter and report them.
As I stated, there seems to be more bass, but it is very subtle; it could even be that the bass frequency is the same but the woofer is just receiving more energy.
If bass was the only reason to 'bridge', I'd save my $$ and keep the amplifier in stereo mode and call it day.
Alternatively, the results I note going to "bridged mode" or 'mono mode' surprised the heck out of me: I was expecting more power, more slam, more volume in a high level kinda way; I noted more air, more presence and more fluidity and a wider soundstage (depending on material used). It's a more sophisticated sound all around.

Makes me wonder how a small rated amp like Schitt Aegir would respond in 'Bridged mode'; which has many fans on other forums as well. In Canada, quantity x2 Schitt Aegir is starting to get up there in price due to exchange rates and makes me wonder: should I take a punt and try it for my second system?
Science would predict that with an amplifier as superb as the AHB2 as long as it’s operating within its power limits (clipping indicators not blinking), perhaps our dogs can hear the difference, but us humans should not hear any difference in DF, distortion, FR, channel separation … of a single amp vs two bridged.

One test we could try is to run two amps, using only one channel of each and see how that sounds. I don’t believe these are dual mono amps, and the two channels share one power supply. So this is not a 100% perfect test, but it would be interesting to see if this is about power.

My guess is this is placebo, that said, I’m really enjoying having 4 in bridged mono.
 

pogo

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should I take a punt and try it for my second system?
If you still want to experiment, you can also try a T+A A200. Here you can possibly experience a deja vu when activating the DF LO switch ;)
 

Darkscience

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For what it is worth to anyone discussing this topic, I recall a conversation I had with Benchmark support, (I forget the guys name who helped me, he is the only one I have ever talked too when calling them), were I was told that running 2-AHB2 bridged will not improve my sound unless the amp is clipping and more power is needed. Again, the way I understood it, if I am not clipping, adding another AHB2 will do nothing to help my sound.

My personal belief is that any perceived difference will be in your mind, like someone else pointed out. I also believe it will not hurt anything and even if it is only placebo, it is still cool to have 2 of them and if what you ultimately hear is what your brain says your hearing, then no harm is done in having two and enjoying the placebo effect. Ultimately if 2-AHB2 bridged sound better to you, there is no need to convince anyone else of it if you are enjoying yourself.

I myself struggle with the issue of boredom and want to buy another AHB2 to bridge them, fully knowing that it should not sound different, but my guess is my brain will make me think it sounds better, so be it.
 

Geert

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If you still want to experiment, you can also try a T+A A200. Here you can possibly experience a deja vu when activating the DF LO switch ;)
Also this story has already been refuted. How is it possible that you keep on repeating this nonsense like nothing happened?
 

fpitas

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pogo

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This is exactly what is done.
And here is a technical explanation (in german): Link

And once again to remind:
After the stereo team has confirmed that the DF was measured properly at a 4ohms load and not bridged for the AHB2 ((63Hz/1kHz/14kHz): 48/45/19), I still wonder how the reduced control of the chassis and especially in bridge mode should not have an effect?
Where would the values be with 3ohms, ...?
 
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For what it is worth to anyone discussing this topic, I recall a conversation I had with Benchmark support, (I forget the guys name who helped me, he is the only one I have ever talked too when calling them), were I was told that running 2-AHB2 bridged will not improve my sound unless the amp is clipping and more power is needed. Again, the way I understood it, if I am not clipping, adding another AHB2 will do nothing to help my sound.

My personal belief is that any perceived difference will be in your mind, like someone else pointed out. I also believe it will not hurt anything and even if it is only placebo, it is still cool to have 2 of them and if what you ultimately hear is what your brain says your hearing, then no harm is done in having two and enjoying the placebo effect. Ultimately if 2-AHB2 bridged sound better to you, there is no need to convince anyone else of it if you are enjoying yourself.

I myself struggle with the issue of boredom and want to buy another AHB2 to bridge them, fully knowing that it should not sound different, but my guess is my brain will make me think it sounds better, so be it.
Going to test 1 (one) of them in stereo and see what happens!
 
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