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Revel M16 Speaker Review

edechamps

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IMO on-axis is of no practical usage as it is a singlle measuremetn taken strictly at axis. Move 5 deg in any direction and you will get another response.
Well, LW in even worse in that regard: it doesn't accurately describe any response you can actually get at any angle.

using single on-axis measurement to describe anything is utter nonsense.
Using LW measurement to describe anything is utter nonsense. See, I can make assertions too! :D

Both these statements are somewhat correct. What does make sense is using LW and On-Axis together to determine where anomalies are coming from.

This conversation did give me the idea of adding a feature to Loudspeaker Explorer where you can see all responses at all angles used for LW in a single graph. That might provide the best of both worlds: full spatial information and no averaging.
 

QMuse

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Well, LW in even worse in that regard: it doesn't accurately describe any response you can actually get at any angle.



Using LW measurement to describe anything is utter nonsense. See, I can make assertions too! :D

Both these statements are somewhat correct. What does make sense is using LW and On-Axis together to determine where anomalies are coming from.

This conversation did give me the idea of adding a feature to Loudspeaker Explorer where you can see all responses at all angles used for LW in a single graph. That might provide the best of both worlds: full spatial information and no averaging.
LOL :)

Ok, I admit both make sense, although I would like to see LW narrowed down a little.

However, as I already mentioned, looking at the on-axis vs LW it really seems to me Harman engineers optimised for linear LW, not on-axis. :D

(upper curves C52, lower M16, red is LW and blue is on-axis)

Capture.jpg
 

edechamps

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it really seems to me Harman engineers optimised for linear LW, not on-axis. :D
That might well be true, and I'm not saying that's not a reasonable design philosophy. In fact, if I were in their shoes I would likely do the same. But just because linear LW was their priority doesn't mean that individual angles within the LW are not important. These two things are not mutually exclusive. You can optimize for LW and also try to make sure individual angles within the LW don't deviate too much from the average.
 

QMuse

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That might well be true, and I'm not saying that's not a reasonable design philosophy. In fact, if I were in their shoes I would likely do the same. But just because linear LW was their priority doesn't mean that individual angles within the LW are not important. These two things are not mutually exclusive. You can optimize for LW and also try to make sure individual angles within the LW don't deviate too much from the average.
If optimising for LW you would certainly make response worse at some angles, including on-axis - you simply can't have it all looking perfect. :D
 

edechamps

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If optimising for LW you would certainly make response worse at some angles, including on-axis - you simply can't have it all looking perfect. :D
Exactly. It has to do with priorities, budget, and design philosophy - in one word: engineering. I think the core question is: is it better to make LW look better at the expense of all (or most) individual angles within the LW? When does the tradeoff make sense? I don't know the answer to this question.
 

Jon AA

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IMO on-axis is of no practical usage as it is a singlle measuremetn taken strictly at axis. Move 5 deg in any direction and you will get another response.
If you have really, really, crappy speakers (save for those exceptions I already explained).
 

QMuse

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Exactly. It has to do with priorities, budget, and design philosophy - in one word: engineering. I think the core question is: is it better to make LW look better at the expense of all (or most) individual angles within the LW? When does the tradeoff make sense? I don't know the answer to this question.
It would seem logical to me that by optimising the LW response they are trying to make speaker sound better to an average audiophile in the average room. That should be the universal target of all speaker designers, right?

The thing I see here is that by doing that they are not really following Toole's and Olive's line of thought.
 

maty

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Exactly. It has to do with priorities, budget, and design philosophy - in one word: engineering. I think the core question is: is it better to make LW look better at the expense of all (or most) individual angles within the LW? When does the tradeoff make sense? I don't know the answer to this question.
November 2016, Samsung bought Harman International (Harman Kardon, JBL, Revel, Infinity, Arcam, Crown, AKG...) -> priorities must have changed.

https://en.wikipedia.org/wiki/Harman_International#Brands

No reply to my email.
 

edechamps

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It would seem logical to me that by optimising the LW response they are trying to make speaker sound better to an average audiophile in the average room.
Again, I feel like we disagree on the use of the word "average" here.

If you were saying something along the lines of "they are trying to minimize the average deviation (or, in other words, standard error or something similar) from flat of every angle in the LW", then yes, I agree that would make a lot of sense as a design philosophy. But that's not the same thing as trying to minimize the average deviation of the LW curve itself. The latter is trivial to achieve: just EQ the LW to flat. But I would expect the former, which is much harder to achieve, to better correlate with the experience of an actual listener in a real-world scenario.
 

QMuse

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Again, I feel like we disagree on the use of the word "average" here.

If you were saying something along the lines of "they are trying to minimize the average deviation (or, in other words, standard error or something similar) from flat of every angle in the LW", then yes, I agree that would make a lot of sense as a design philosophy. But that's not the same thing as trying to minimize the average deviation of the LW curve itself. The latter is trivial to achieve: just EQ the LW to flat. But I would expect the former, which is much harder to achieve, to better correlate with the experience of an actual listener in a real-world scenario.
Oh, I'm sure they tried to make curve of every angle as flat as possible, but in the end they had to choose to aim for linear LW curve itself vs linear on-axis curve itself.
 

QMuse

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Again, I feel like we disagree on the use of the word "average" here.

If you were saying something along the lines of "they are trying to minimize the average deviation (or, in other words, standard error or something similar) from flat of every angle in the LW", then yes, I agree that would make a lot of sense as a design philosophy. But that's not the same thing as trying to minimize the average deviation of the LW curve itself. The latter is trivial to achieve: just EQ the LW to flat. But I would expect the former, which is much harder to achieve, to better correlate with the experience of an actual listener in a real-world scenario.
Let me put it this way: you have at your disposal M16 spinorama measurement that Amir made and you are about to make active version of M16 so you can put a bunch of PEQ filters in it. What would you do? Would you optimise for on-axis or LW? Or for both of them, as a compromise? :)
 

edechamps

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Let me put it this way: you have at your disposal M16 spinorama measurement that Amir made and you are about to make active version of M16 so you can put a bunch of PEQ filters in it. What would you do? Would you optimise for on-axis or LW? Or for both of them, as a compromise? :)
That's a good question. I'm not a speaker designer and I have not yet thought much about the idea of applying EQ to correct for anechoic speaker behaviour (which, until @amirm started distributing raw measurement data, was not even something a consumer could easily do), but here's my intuitive take on it.

Off the top of my head, intuitively, I would only apply a given EQ filter if it made all or most individual LW angles better and does not make some angles considerably worse. To be fair, in many cases this is mostly equivalent to just EQ'ing the LW average directly - because, let's face it, we are discussing subtle distinctions here - but not always.

This is similar to what some room EQ software does when you ask to correct for multiple listening positions: they only apply a specific filter if it makes most or all positions better and no position significantly worse. They don't just go around and take the average of all positions and EQ that. Well I would apply the same basic principle for EQ'ing a speaker - just substitute "listening position" with "listening angle".
 
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ctrl

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Would like to give another indication (I've lost track of whether anyone has mentioned this before) that the 5kHz resonance of the M16 could be an artifact of the cone-breakup of the mid-bass driver.

It was mentioned that the bump around 5kHz could also be caused by edge diffraction. Since the cabinet is only 22cm wide a possible bump would fit quite well for a normal 1'' dome tweeter - but predicted is only a 2dB increase by 4-5kHz:
1583593434598.png


However, since a wave-guide is used, it should still control the radiation at 5kHz, so that the effects of edge diffraction in this area should be minimal:
1583593448914.png


Edge diffraction also does not (usually) delay the decay of the dome tweeter.
However, when looking at the speaker's decay around 5kHz in the CSD, a delayed decay can be observed:
1583594288304.png


This could be due to the tweeter itself, but it could also be an artifact of the cone-breakup of the mid-bass driver.
 

tuga

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This could be due to the tweeter itself, but it could also be an artifact of the cone-breakup of the mid-bass driver.
It would be nice to see the individual on-axis FR and CSD plots for mid-woofer and tweeter of those speakers which provide separate terminals for bi-wiring.
 

edechamps

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Assuming one’s not deaf in one ear and listening in an anechoic chamber, why is any one angle of any special import?
At any given time, you are listening to one of these angles, you are not listening to the LW (which is not a real response). I agree that unless you stay very still it is not predictable which specific angle you'll land on, but you will always listen at one single angle at any point in time - not to an average of multiple angles. This is why consistency between multiple angles within the LW is important, and why averages can be misleading.

(Okay, actually it's two angles, because there are two speakers when listening in stereo. My point still stands, though. Come to think of it, maybe that's partly why we are more discriminating in mono listening than stereo listening!)
 

aarons915

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At any given time, you are listening to one of these angles, you are not listening to the LW (which is not a real response). I agree that unless you stay very still it is not predictable which specific angle you'll land on, but you will always listen at one single angle at any point in time - not to an average of multiple angles. This is why consistency between multiple angles within the LW is important, and why averages can be misleading.

(Okay, actually it's two angles, because there are two speakers when listening in stereo. My point still stands, though. Come to think of it, maybe that's partly why we are more discriminating in mono listening than stereo listening!)
I don't know if this is entirely true since human hearing is much more complex than simple angles directly into our ears, Dr. Toole mentions 2 ears and a brain often when talking about the auditory system. You mentioned 2 different speakers but you also have early reflections which are perceived as direct sound and you have 2 ears which are hearing direct and reflected sounds from both speakers and all early reflections simultaneously, for these reasons it makes sense to me that averages are better representations of what we hear than individual angles. That's not to say that individual angles are meaningless but in the case of a speaker like the M16, I would just aim it straight ahead with no toe-in and not worry about that spike on-axis.
 

edechamps

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You mentioned 2 different speakers but you also have early reflections which are perceived as direct sound and you have 2 ears which are hearing direct and reflected sounds from both speakers and all early reflections simultaneously
The discussion was originally about whether the Listening Window average is a representative measure of the direct sound. Wider angles related to early reflections and sound power are important of course, but are not in the scope of my argument.
 

tuga

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you also have early reflections which are perceived as direct sound
Are early reflections perceived as direct sound (in the context of stereophonic reproduction)?
 
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