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Revel M22 Speaker Review

thewas_

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#61
First of all a full circle doesn't make sense but a half circle, so something similar to the CBT. But in both cases when you move from the centre of the array the level will stay constant till some angle and then drop more than it would just by using a single driver due to destructive interference which creates the beaming. Also a flattish ellipse like a CBT will keep the level more constant compared to a half circle where it will start dropping faster.
 
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QMuse

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#62
First of all a full circle doesn't make sense but a half circle, so something similar to the CBT.
Of course it does, you just need to think out of the box - imagine a big party sitting at a large table in your yard, delicious smell coming barbeque. If you put a full circle speaker (omnidirectional) at the middle of the table you will get much better sound for everyone than with, for example, JBL Charge 3 type of speaker. :D
 

QMuse

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#63
Yeh, as @thewas_ said. To get wide horizontal dispersion from a CBT, it needs to be a vertical array.

The reasons such CBTs tend to have wide vertical dispersion are:
  • they tend to use very small drivers
  • at higher frequencies, they produce the greatest sound pressure at 90° off-axis
This is the normalised horizontal response of a CBT made up of 16 x 1.5" drivers spaced approx. 3cm apart. The red trace is 90° off-axis. As you can see, as frequency increases, the 90° off-axis response rises with reference to the on-axis response:

View attachment 56151

And this is the vertical response of the same array. As you can see, the vertical array narrows the vertical beamwidth, as opposed to widening it:

View attachment 56152

This is the layout of the array FWIW:

View attachment 56154
Ah, ok - obviously I mixed it. :D
 

thewas_

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#64
Of course it does, you just need to think out of the box - imagine a big party sitting at a large table in your yard, delicious smell coming barbeque. If you put a full circle speaker (omnidirectional) at the middle of the table you will get much better sound for everyone than with, for example, JBL Charge 3 type of speaker. :D
:D A real omnidirectional loudspeaker would be a really good solution in that case, but a circular array of drivers isn't such, but just a nightmare of interference patterns. :D
 

andreasmaaan

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#65
Of course it does, you just need to think out of the box - imagine a big party sitting at a large table in your yard, delicious smell coming barbeque. If you put a full circle speaker (omnidirectional) at the middle of the table you will get much better sound for everyone than with, for example, JBL Charge 3 type of speaker. :D
Unfortunately that's not true. You'll end up with a comb filter. A semicircle is already really pushing it for a CBT. Ideally, it should be a quarter circle or even less for the CBT to function effectively.

Here's what happens when you take the same array I presented in the previous post and bend it round into a full circle (in this case normalised to an arbitrary listening position):

CBT_1 Directivity (ver, pos front) A.png


1585486630815.png
 

QMuse

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#67
Unfortunately that's not true. You'll end up with a comb filter. A semicircle is already really pushing it for a CBT. Ideally, it should be a quarter circle or even less for the CBT to function effectively.

Here's what happens when you take the same array I presented in the previous post and bend it round into a full circle (in this case normalised to an arbitrary listening position):

View attachment 56155

View attachment 56156
That is a circle in vertical plane, not horizontal. Although I'm sure horizontal would end up being a similar nightmare! :D
 

Herbert

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#71
I know this is a bit Off-Topic, but as we see many speaker classics reviewed I am very eager to see the 3A Audio Design "Midi Master" reviewed. They came up around 1989 and were produced in southern France BUT the company changed ownership and moved to Canada - Tash Goka is the owner and the name changed to Reference 3A. To my knowledge the basic design has not changed since then, two ways, a sloping surface for set back tweeters and only a capacitor as crossover. To my ears they are the best sounding speakers ever but I had 30 years to get accustomed to them and as we all know good sound does not necessarily mean fidelity...
 
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#72
Studies have shown that neither THD, nor IMD impact listener preference.
I can concur with that in general, in instances when distortion is not high - as in any competently designed and manufactured driver (not needed to be expensive). Especially THD number by itself is meaningless. Separate presentation of harmonics from 2nd to 5th are much more revealing.
In my opinion there are examples where bad loudspeaker sound is directly connected to a relatively high 3th harmonic (4th and 5th are very low in general). I have noticed that several low- to-mid-price models of the German manufacturer Canton have increased THD between 2 and 3 kHz, as shown in the measurements of German magazines Stereoplay and Audio (higher-price models were with low THD). By itself, this increase in THD may be coming from a higher 2nd harmonics, so no big deal (all those models were highly praised in the reviews). But one day, one disturbed audiophile call me to ask for measuring his brand new Canton (I forget the model). He was complaining about the distorted sound. And indeed, the measurements showed high 2 or 3 % (as I recall) distortion from the 3rd harmonic alone, between 2 and 3 kHz (measured with 2.83 V), the same as in the Stereoplay and Audio measurements.
I can't make a qualified statement backed with blind listening tests, but after many measured and listened loudspeakers I feel that any increase of 3rd harmonic above some 0.7% (measured at 90dB/1m) in the mid to high frequencies of the loudspeaker is detrimental to the sound quality.
By the way, can you please choose another colors for the graphs of 2nd and 3rd harmonics in your measurements? As now, both colors of the graphs of 2nd and 3rd harmonics are dark and similar, so it is hard to differentiate between them. I think it would be much better if you switch the colors between 3rd and 5th harmonic. In that instance green 3rd harmonics will easily stand out.
 
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#73
M22 verse M16 is good example to see the effect in objective number for that wave guide, lookup how smoothness in directivity index curve improve for M16 over M22 and the smoother lobe in horizontal polar map tells the same story, in lower spins i EQed them flat on axis in audio band because think having one steady flat curve relative the other curves makes the eye bit happier to stare out tendencies, technically it should be good to know that directivity index curve is a divide calculated as the difference between listening window and power response.

View attachment 56105
When did waveguides start coming into wide use and who started using them first?

As an aside, I have somewhat lusted for the Amphion MobileOne12 portable monitoring kit with the One12 speakers with their cool waveguides to have a good system when I travel for extended times - well when I USED to travel...

https://amphion.fi/create/products-pro-audio/mobileone12/
 

andreasmaaan

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#74
When did waveguides start coming into wide use and who started using them first?
Horns were in use before dome tweeters, but the focus in home audio began to shift from acoustic loading to directivity control (and accordingly the name began to shift from "horn" to "waveguide") in (IIRC) the mid-2000s.

Revel began incorporating waveguides in their speakers with their second generation of products, released (again, IIRC) around the late-2000s.
 
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#75
Horns were in use before dome tweeters, but the focus in home audio began to shift from acoustic loading to directivity control (and accordingly the name began to shift from "horn" to "waveguide") in (IIRC) the mid-2000s.

Revel began incorporating waveguides in their speakers with their second generation of products, released (again, IIRC) around the late-2000s.
That makes sense as I was pretty much an exclusive Martin-Logan guy starting in 1993 or so and paid little attention to dynamic speakers until I needed to find speakers for smaller rooms. My understanding, however, is that a “horn” is essentially an acoustic amplifier of the sound produced by an otherwise limited output transducer and a “wave guide,” while horn-like in appearance, is intended to influence directivity and the integration of the tweeter output with that of the midrange or “midwoofer.” In any case, they sure look Ike they work (and the results are not the same as that of “horns”)!!
 

andreasmaaan

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#76
That makes sense as I was pretty much an exclusive Martin-Logan guy starting in 1993 or so and paid little attention to dynamic speakers until I needed to find speakers for smaller rooms. My understanding, however, is that a “horn” is essentially an acoustic amplifier of the sound produced by an otherwise limited output transducer and a “wave guide,” while horn-like in appearance, is intended to influence directivity and the integration of the tweeter output with that of the midrange or “midwoofer.” In any case, they sure look Ike they work (and the results are not the same as that of “horns”)!!
Yeh, you've hit the nail on the head in terms of the difference between a horn and a waveguide. The reason I mentioned horns in my previous post at all was just that all horns are waveguides (they affect directivity) and all waveguides are horns (they provide acoustic loading). So the difference is really one of emphasis.
 
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#77
Yeh, you've hit the nail on the head in terms of the difference between a horn and a waveguide. The reason I mentioned horns in my previous post at all was just that all horns are waveguides (they affect directivity) and all waveguides are horns (they provide acoustic loading). So the difference is really one of emphasis.
Same basic tool used to very different effect! I must admit, until I found this great forum - thanks @amirm - and started looking at these great speaker measurements, I was suspicious of “wave guides” due to my experience with Klipsch horn-loaded speakers (I spent a LOT of time with friends whose family were fanatics - they had Heresys, La Scalas and Klipschorns). Most also looked more like a marketing gimmick than an effective device. I think some measurements have shown some to be just that, as less technically capable manufacturers just “ape” the products of the technology leaders. Properly designed, they appear to be a really elegant solution to a long vexing problem.
SOME advances truly are real and not snake oil! I assume the advances are largely due to the modern availability of modeling software and cheap computing power.
 
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#78
Same basic tool used to very different effect! I must admit, until I found this great forum - thanks @amirm - and started looking at these great speaker measurements, I was suspicious of “wave guides” due to my experience with Klipsch horn-loaded speakers (I spent a LOT of time with friends whose family were fanatics - they had Heresys, La Scalas and Klipschorns). Most also looked more like a marketing gimmick than an effective device. I think some measurements have shown some to be just that, as less technically capable manufacturers just “ape” the products of the technology leaders. Properly designed, they appear to be a really elegant solution to a long vexing problem.
SOME advances truly are real and not snake oil! I assume the advances are largely due to the modern availability of modeling software and cheap computing power.
I also have come the same conclusions.
 
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#80
The subjective listening tests seem to suffer from undamped / strong side reflections and possibly cancellation in the bass and low mids from the front wall, this in combination with no backwall / open to a large space can easily give a bright sound it seems to me (hence the subjective preference for waveguided speakers which have a dark off-axis) that is not representative of an average listening room, let alone a quality dedicated audio room. Do you by any chance have an unsmoothed not eq-ed measurement at listening position?

With that said, I'm still at loss why this Revel speaker would get a recomendation and no negative annotations while the very similar (and perhaps slightly better overall) Zaph Audio ZA5.2 gets a bad review / annotations / recomendation.
 
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