• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

Benchmark ABH2 Replacement

What many people forget is that a speaker also changes its impedance depending on the volume/transient signal.
No, they don't. And they also understand CYA.
 
The measured values from STEREO are just as valid as all other measurements. They were all measured under different conditions and STEREO simply takes a more realistic approach.
I don't agree. I think they made an error. See my calculations earlier in the thread where their numbers didn't make sense. And if I am wrong show me how to get the Stereo numbers to agree with the Soundstage graph, which you should be able able to do as it is just a matter of converting back and forth between DF and impedance, and adding or subtracting the cable contribution. But if you say it is just a matter of different conditions lets use the Soundstage numbers which I don't think anyone is saying are wrong.

Anyway that doesn't really matter anyway. It seems the consensus with people who are really considering the physics of this, as opposed to hand waving, is that DF only needs to be a few 10s to be good enough, beyond that there is no additional advantage in driver control. Here is the paper on that cited on the Benchmark site:


Can you reference something better than you have been doing to refute the logic in that paper, and what @solderdude wrote in post #73. I thought your "resistance is distributed" response to his calculation was not much of a counter argument.

Sorry everyone if this is tiresome!

edit: really @pogo it would be appreciated if you can show how the Soundstage and Stereo numbers for the AHB2 DF are in agreement. Because if they are not, and you won't admit that the Stereo numbers seem to have a problem, then that shows you are not a reasonable person.
 
Last edited:
The gap is, we don't have a clear mapping between an acoustic signal "in the air" and the way it is then perceived.
We don't need to know how it is perceived. All we need is that the acoustic signal of the reproduced sound "in the air" (and at the ear) is as close to identical to the original sound at the performance as possible. What goes on between the two ears is one's own unique business.
 
@pogo here is something from folks who design amplifiers with very low output impedance:

from https://audiophilestyle.com/ca/bits...eaders-qa-with-lars-risbo-bruno-putzeys-r815/

@Sagittarius: Does the high damping factor of class D amplifiers negatively affect the subjective sound quality of some types of speakers as some reviews seem to suggest?

[Damping factor is defined as 8 ohms divided by output impedance, high DF means low output impedance and vice versa -ed]

Bruno: Oi, we had to battle for this high damping factor! Before anyone worked out how to put global feedback around the output filter, the damping factor of class D amplifiers was actually much lower than that of class A/B. And much good did that do… In particular, the big problem was at high frequencies, where the frequency response became enormously load dependent. Most speakers have a highish impedance in the top octave, and early class D amplifiers would thereby produce a very clear lift in the top end, which explains why they were often perceived as sounding harsh.

Lars: Have we got an indication where this idea of high DF being bad for sound might have come from?

Bruno: I’m not sure. Maybe in the past, high DF was associated with big, sluggish amps? I wonder what speaker they were using. If they’re listening with a broadband speaker with no crossover filter for instance, a high output impedance could bring some of the benefits of current drive and reduce hysteresis distortion in the iron in the speaker motor.

Lars: You’d have to really go overboard.

Bruno: An SET amp with no feedback typically has an output impedance equal to the rated load impedance so you’d be looking at nearly 6dB less hysteresis distortion in the midrange. But for any other speaker this trick is quite useless. Crossover filters are simply designed with the assumption of a voltage source. It’s a matter of standardisation. Otherwise how this particular speaker sounds when connected to that particular amp becomes rather unpredictable.

Lars: Isn’t that precisely why hi-fi shops do all that mixing and matching?

Bruno: It’s quite possible that shop owners would have less fun if all amps had sensibly low output impedance. But beyond “sensible”, damping factor is completely overrated in my view. Once output impedance is low enough to keep response changes due to load variations to within a small fraction of a dB it’s low enough. The term damping factor is seriously misleading because some folks think that an amp with a DF of 1000 is ten times better at stopping a moving cone than one with a DF of 100. It doesn’t make a jot of difference. In both cases the resistance of the voice coil, the crossover filter and even the speaker cable will dominate totally. In actual fact you wouldn’t even want to have infinite damping because the speaker designer counts on the natural resonance to define the bass response. So it’s rather a good thing that the speaker has its built-in resistance in series with the amp.

Lars: Having a super low output impedance does have one real benefit: it makes bi-wiring work. The whole point of bi-wiring is to isolate the tweeter and woofer portions electrically. If you have a common impedance in series with the speaker, distorted currents produced by the woofer will turn into a distorted output voltage which in turn is seen by the tweeter section. So if you want bi-wiring to work its magic you really do need an extremely low output impedance, which is the same as super high DF of course.

Bruno: Good point, a hundred might not be enough then. I think people resort to bi-amping when their amps don’t have low enough output impedance for bi-wiring to do the trick. So for a serious audiophile having really high DF is a real advantage, if only financially.
 
here is something from folks who design amplifiers with very low output impedance
Look hear at para. 2.3.2: Link
Purifi was also involved in the T+A A200 and M200 with switchable DF. The AHB2 corresponds more to the DF LO position.
 
What many people forget is that a speaker also changes its impedance depending on the volume/transient signal. Denon, for example, has understood this: Link
The output impedance of an amplifier can also change depending on the amplifier design with the volume.
The measured values from STEREO are just as valid as all other measurements. They were all measured under different conditions and STEREO simply takes a more realistic approach.
It look like you misunderstood what they meant.

A 4 ohm (average or at 1kHz) speaker may well drop below 3ohm at specific frequency (bands) and even lower than that even. In such case you don't want the amp to have the current limiter to kick in or have a too high (< 20) DF.
Another aspect which can affect the load an amp sees is current-phase being too different from the voltage-phase which can lead to an amp not being able to provide the needed current (when the phase is off).
All very measurable, both for amps and for speakers and is what the Denon story is about.

Another aspect of non-linearity of back EMF (if that's what you mean) can be from the magnetic field from the magnet (in the airgap) produces less back EMF when you have a short throw voicecoil getting outside its linear field. In this case there also is an higher odd harmonic distortion anyway.
As the source impedance is determined by the ohmic resistance the resistance will only be higher but the current can be either positive or negative at certain frequencies.
But the ohmic resistance does not change, only the apparent impedance can change due to current phase.
This is not what the Denon article was about though.
 
Look hear at para. 2.3.2: Link
Purifi was also involved in the T+A A200 and M200 with switchable DF. The AHB2 corresponds more to the DF LO position.
Are you switching to discussion of bi-wiring now? Really I got the impression that tongues were in cheeks when they talked about DF as beneficial in bi-wiring in audiophilestyle Q&A.
 
We don't need to know how it is perceived. All we need is that the acoustic signal of the reproduced sound "in the air" (and at the ear) is as close to identical to the original sound at the performance as possible. What goes on between the two ears is one's own unique business.
I kinda like my rose coloured glasses. The exact sound staging I get from sitting in front of my speakers and having a vocalist sized exactly right compared to the instruments, as well as getting the exact position of those instruments, probably sounds nothing like the original sound at the performance. Similarly I also enjoy a little more harmonic richness than the original performance likely has. If I had a hearing disability in the higher frequencies, where they started to irritate me when played as per the performance I would also seek a system that tamed those.

I believe the ideal for listening to musing should be your personal perceived enjoyment of it, not exact reproduction of the sound at the event. In fact I suspect much of the mastering that goes on makes your music sound nothing like it actually happened at the event anyway.

So I think there's nothing wrong in seeking a music system that sounds good to you, if that's preferable to what the actual event sounds like by your estimation. So I'd argue you exactly want to choose a system for how it is perceived by you, and not how closely it replays the original event... which is a fiction given everything is mastered.
 
We don't need to know how it is perceived. All we need is that the acoustic signal of the reproduced sound "in the air" (and at the ear) is as close to identical to the original sound at the performance as possible. What goes on between the two ears is one's own unique business.
It amazes me how simple this is and difficult it is for some to grasp, even with measurements.
 
It amazes me how simple this is and difficult it is for some to grasp, even with measurements.
I find it difficult to grasp. I'd buy a system for how I perceived the music from it... regardless of someone telling me how correct it was. If I have to choose between someone arguing it's exactly correct but I don't enjoy it vs. it is euphonic but I do enjoy it.... I'll pick the one I enjoy every time. I don't listen with a computer, I listen with my soul. I think this site forgets this sometimes.
 
I find it difficult to grasp. I'd buy a system for how I perceived the music from it... regardless of someone telling me how correct it was. If I have to choose between someone arguing it's exactly correct but I don't enjoy it vs. it is euphonic but I do enjoy it.... I'll pick the one I enjoy every time. I don't listen with a computer, I listen with my soul. I think this site forgets this sometimes.
Then do not ask here and do it as you like it. You may not expect our advice on a system with euphonic distortion that you would like. I know nothing like euphonic distortion, if there was audible distortion, it always made the sound worse.
 
I find it difficult to grasp. I'd buy a system for how I perceived the music from it... regardless of someone telling me how correct it was. If I have to choose between someone arguing it's exactly correct but I don't enjoy it vs. it is euphonic but I do enjoy it.... I'll pick the one I enjoy every time. I don't listen with a computer, I listen with my soul. I think this site forgets this sometimes.
Accuracy is something not everyone needs. Audiophiles are dying breed
 
Then do not ask here and do it as you like it. You may not expect our advice on a system with euphonic distortion that you would like. I know nothing like euphonic distortion, if there was audible distortion, it always made the sound worse.
I didn't ask you anything. I simply said I will always pay for the system that sounds better to me... not the one that measures most accurately. I don't listen by looking at sign waves on an oscilloscope, I listen with a glass of wine in my hand. I'm pointing out that maybe the ultimate objective of listening to music should be assembling a system you enjoy listening to the most. Abhorrent I know.

Measuring frequencies and obsessing over Signal to Noise has its place in perhaps evaluating what are likely to be good sounding candidates, but everyone hears differently and the accurate reproduction of exactly what is on the recording might not actually be the most enojoyable listening experience to folks. The science should be a guide, but it is a mistake to take a metric and make it the objective. A metric should be a guide to achieving the objective. The objective is to have the most enjoyable experience of the music... to my mind.
 
Last edited:
I don't listen by looking at sign waves on an oscilloscope
But you do read posts at ASR, so simple, start there and go listen. Best of both worlds.
 
But you do read posts at ASR, so simple, start there and go listen. Best of both worlds.
exactly my point. Don't tell people that how they perceive the sound is unimportant and that the objective of music is having the most accurate reproduction at the ear. I reject that completely, the objective to my mind is exactly measured in how you perceive the sound. Measuring is a good way to understand what is likely to end up with something you'll perceive favourably. It's the metric, not the objective.

Also I argue that what you hear from a recording is unlikely to be accurately how you would experience it at the event. Its a fiction in itself, and a preferable one often.
 
Seems like components that are not accurate should sell for less $ than ones that are accurate. It's always makes me scratch my head when I try to understand why people pay extra for poorly designed components.

Anyway, there are different ways of arriving at the 'sound' one prefers. You can play around with trying out various colored components, or you can assemble a system that is a neutral/ transparent as possible, and then dial in the preferred 'sound' with DSP. The latter approach allows one to tailor on the fly.
 
Seems like components that are not accurate should sell for less $ than ones that are accurate. It's always makes me scratch my head when I try to understand why people pay extra for poorly designed components.

Anyway, there are different ways of arriving at the 'sound' one prefers. You can play around with trying out various colored components, or you can assemble a system that is a neutral/ transparent as possible, and then dial in the preferred 'sound' with DSP. The latter approach allows one to tailor on the fly.
you ever heard a DSP that could really indistinguishably mimic a SET tube amp?
 
Why would you want to mimic the sound of a broken amp ( although I am sure it is perfectly possible)?
Keith
 
you ever heard a DSP that could really indistinguishably mimic a SET tube amp?
Which specific one? The way they bend the sound is not mysterious.
 
Back
Top Bottom