Do speakers with good off-axis response require less acoustic treatment at first reflection point?

[Snoochers]

I have KEF R7s and will be putting them in a theatre. I'm familiarizing myself with acoustic treatments and early reflections etc. I've run across a few people who suggest that speakers with good off-axis response benefit from having minimal early reflection absorption to maximize sound stage.

Is there any merit to this argument? Any thoughts on this would be great!

 

[MZKM]

I can’t find it right now, but Matthew Poes & Gene did a video on their Audioholics channel that touched on this. Matthew stated that since acoustic panels (the canvas type) aren’t true full-range, you thus would be altering the tonailty, and that when it hits at extreme angles, the fabric of the panels actually mess the sound up a bit. So, his point was mainly that if the speaker has a good off-axis, you do not need side-wall absorption in a good room.

 

[AnalogSteph]

The crux of the matter is, absoption may actually be welcome to get the reverb times in check. So a step forward in RTxx comes with a step back in tonality. You would thus want absorption that is as constant over frequency as possible, which is easier said than done. This is barely ever specified for panels - and how would you even measure it anyway? I mean, sticking a speaker in a chamber lined with the stuff should paint a clear enough picture but hardly makes for standard testing conditions, does it?

 

[audio2design]

No easy answer. Depends on the time delay from the direct and reflected and relative energy which requires a more accurate definition of good off axis response.


A wider dispersion often is best used with a good wide bandwidth panel. Sometimes a bit of diffusion to reduce the first reflection energy works well.


Keep in mind personal preference also comes into play.

 

[Snoochers]

I can’t find it right now, but Matthew Poes & Gene did a video on their Audioholics channel that touched on this. Matthew stated that since acoustic panels (the canvas type) aren’t true full-range, you thus would be altering the tonailty, and that when it hits at extreme angles, the fabric of the panels actually mess the sound up a bit. So, his point was mainly that if the speaker has a good off-axis, you do not need side-wall absorption in a good room.

thanks! I guess reverb is the big issue. Maybe this can be controlled primarily by panels in front and back?

 

[Snoochers]

The crux of the matter is, absoption may actually be welcome to get the reverb times in check. So a step forward in RTxx comes with a step back in tonality. You would thus want absorption that is as constant over frequency as possible, which is easier said than done. This is barely ever specified for panels - and how would you even measure it anyway? I mean, sticking a speaker in a chamber lined with the stuff should paint a clear enough picture but hardly makes for standard testing conditions, does it?

Good points thanks. How much treatment does a carpeted room with chairs usually need for reverb anyway ?

 

[Snoochers]

No easy answer. Depends on the time delay from the direct and reflected and relative energy which requires a more accurate definition of good off axis response.


A wider dispersion often is best used with a good wide bandwidth panel. Sometimes a bit of diffusion to reduce the first reflection energy works well.


Keep in mind personal preference also comes into play.

Thanks. Lots to think about

 

[Snoochers]

I can’t find it right now, but Matthew Poes & Gene did a video on their Audioholics channel that touched on this. Matthew stated that since acoustic panels (the canvas type) aren’t true full-range, you thus would be altering the tonailty, and that when it hits at extreme angles, the fabric of the panels actually mess the sound up a bit. So, his point was mainly that if the speaker has a good off-axis, you do not need side-wall absorption in a good room.

let me know if you find that vid!

 

[Emlin]

No easy answer. Depends on the time delay from the direct and reflected and relative energy which requires a more accurate definition of good off axis response.


A wider dispersion often is best used with a good wide bandwidth panel. Sometimes a bit of diffusion to reduce the first reflection energy works well.


Keep in mind personal preference also comes into play.

In what way does diffusion reduce energy?

 

[audio2design]

Reduced energy in the first reflection that reaches the listener, not total energy.

 

[Emlin]

Reduced energy in the first reflection that reaches the listener, not total energy.

So it reduces first reflections, not the energy of them. Because first reflections have to reach the listener, otherwise they wouldn't be first reflections.

 

[theyellowspecial]

Well, technically total energy isn't lost because audio energy is absorbed and dispersed as heat energy with absorption panels, but maybe a2d meant something different. Total audio energy is definitely lost, however.

Home speakers are designed with average, reflective rooms in mind, so over-absorption isn't recommended in most cases. Speakers should be selected based on dispersion energy matched to the room and listener preference.

 

[Emlin]

Well, technically total energy isn't lost because audio energy is absorbed and dispersed as heat energy with absorption panels, but maybe a2d meant something different. Total audio energy is definitely lost, however.

Home speakers are designed with average, reflective rooms in mind, so over-absorption isn't recommended in most cases. Speakers should be selected based on dispersion energy matched to the room and listener preference.

You are talking absorption. We were talking diffusers. And I'm aware of the laws of thermodynamics.

The rest of your post is opinion dressed up as fact. But "over-absorption" is clearly not recommended. The clue is in the "over" bit.

 

[theyellowspecial]

Whoops, didn't realize you were talking about diffusion.

 

[Haint]

Good points thanks. How much treatment does a carpeted room with chairs usually need for reverb anyway ?

A room with nothing but chairs, a screen, and speakers is going to be an echo chamber, even with carpet. Bare walls will slapback everything that hits them. Treatments on the rear wall/corners and side walls will have a massive impact on the sound of a largely empty room, but there is some level of preference to it. In my experience the heavier you treat a room, the more it starts sounding like room sized headphones. Some people may prefer this while others may call it dry.

 

[Josq]

I can’t find it right now, but Matthew Poes & Gene did a video on their Audioholics channel that touched on this. Matthew stated that since acoustic panels (the canvas type) aren’t true full-range, you thus would be altering the tonailty, and that when it hits at extreme angles, the fabric of the panels actually mess the sound up a bit. So, his point was mainly that if the speaker has a good off-axis, you do not need side-wall absorption in a good room.

I guess the reality is more nuanced, because untreated walls also will alter the tonality in some way?

 

[Ilkless]

I guess the reality is more nuanced, because untreated walls also will alter the tonality in some way?

Yes, but seems less so than shallow absorption, which essentially acts as a low-pass filter on the reflection's sound signature.

 

[Josq]

Yes, but seems less so than shallow absorption, which essentially acts as a low-pass filter on the reflection's sound signature.

But suppose you have a first reflection in 5 ms. That's within the wavelength of anything below 200 Hz. So does it matter that shallow absorption acts as a low-pass filter? Solving part of the problem is better than no problem solving at all?

 

[Ilkless]

But suppose you have a first reflection in 5 ms. That's within the wavelength of anything below 200 Hz. So does it matter that shallow absorption acts as a low-pass filter? Solving part of the problem is better than no problem solving at all?

The point is that the spectra of directed and reflected sound becomes even more divergent. To quote Floyd Toole in this article:

If the spectra of the direct and reflected sounds are significantly different, the reflections are likely to be more noticeable, from subtle timbral effects up to a premature breakdown of the precedence effect, at which point listeners may be aware of two simultaneous sound images, one located at the loudspeaker and one located at the point of reflection. This is obviously not good. Over the years this is likely a factor in listeners rating loudspeakers with uniform directivity more highly than those with uneven directivity. Wide dispersion seems to be good, but especially if it is uniform with frequency and the spectra of the reflections is not substantially altered. Hundreds of loudspeakers auditioned by hundreds of listeners in double-blind evaluations have demonstrated this; it is monotonously predictable.

 

[tuga]

I have KEF R7s and will be putting them in a theatre. I'm familiarizing myself with acoustic treatments and early reflections etc. I've run across a few people who suggest that speakers with good off-axis response benefit from having minimal early reflection absorption to maximize sound stage.

Is there any merit to this argument? Any thoughts on this would be great!

The artefacts produced by early reflections are a matter of taste: some people like them, other do not.
You'll have to suck it and see.

As a general rule, narrow directivity speakers such as dipoles and (full-range) horns will interact less with room boundaries above Schroeder and omnis will interact the most.

Either way you should be looking at speakers with an even off-axis response, just in case you happen to like side-wall reflections, as this will produce the most balanced response at the listening spot (see previous post).