What to place in front of center speaker to limit early reflections from furniture?

[Duke]

I should point out that just because you can see it on measurements, it does not mean it will sound bad. My advice is to pull your speaker to the front of the shelf and have a listen. I doubt it will sound substantially better than where you have it at the moment. Then you can push it back to where it is and sleep in peace.

Agreed. The ears do not necessarily process sound the same way the eyes process a frequency response graph.

Comb filter effects in particular can look horrendous on paper while being innocuous to the ear.

And one potential downside of using aggressive absorption there is, the short wavelengths will be removed from that sound but the long wavelengths remain, so THAT reflection energy now has a significantly degraded spectral balance.

 

[ExPerfectionist]

You could get a different equipment stand, something not so deep so the center speaker doesn't have to be all the way back against the wall. I got some of these for bookshelves ( https://www.etsy.com/listing/448798564/iron-modernist-record-shelving-brackets ), and liked it so much I got a 2-shelf version for my audio equipment under my TV. Center speaker is on the top of the two shelves, and my TV is on a bracket arm suspended over it (looks like a wall mount). I got wood planks that I stained myself, for both the bookshelves and audio equipment shelves.

And you might consider pulling your L/R mains forward a little more. Would help with the center speaker not being so "visually distracting"

If you're absolutely against moving the center speaker forward, you could put a folded blanket there in front of it. Or some sort of audio absorption panel like what you have on the wall, so it would sit on top of the stand and the speaker would sit on top of it.

 

[Keith_W]

Comb filter effects in particular can look horrendous on paper while being innocuous to the ear.

That brings up an important point. Comb filtering is time critical.

Here is a quick recap of what comb filtering is. Comb filtering is a series of cancellations that occur when a signal is superpositioned over a time-shifted copy of itself.

Let us take two examples, a time delay of 1ms and 10ms. At some point, the delay will result in a 180° phase shift, which will produce phase cancellation. A 180° phase shift is half a cycle, therefore a full cycle is at 2ms and 20ms respectively. Because frequency = 1/T, the frequencies affected can be calculated:

• For a 1ms delay, the lowest cancellation point is 1/0.002 = 500Hz. Additional cancellation points will be at 1kHz, 2.5kHz, 3.5kHz, etc.
• For a 10ms delay, the lowest cancellation point is 1/0.02 = 50Hz. Additional cancellation points will be at 100Hz, 250Hz, 350Hz, etc.

Thus, a shorter delay will result in comb filtering occurring at high frequencies. As can be seen, a delay even shorter than 1ms may result in comb filtering at inaudible frequencies, for example, a 0.1ms delay results in cancellation at 10kHz, 25kHz, 35kHz, etc. On the other hand, delays of 20ms and above are outside the Haas fusion zone, so the delay is heard as space or ambience rather than a change in tonal quality.

A shelf in front of your speaker will produce an exceedingly short time-shifted reflection. That will push the comb filtering effects quite high.

This does not mean there aren't other audible effects from your speaker placement though. It will change the directivity for shorter wavelengths because you are essentially introducing a weird shaped baffle in front of the speaker. And maybe other things, my brain isn't functioning all that well right now. ASR members are always eager to point out my mistakes so maybe I should say something stupid and someone will jump in with the correct reply

I'll take a look at your measurements later and respond.

 

[RickS]

You could get a different equipment stand, something not so deep so the center speaker doesn't have to be all the way back against the wall. I got some of these for bookshelves ( https://www.etsy.com/listing/448798564/iron-modernist-record-shelving-brackets ), and liked it so much I got a 2-shelf version for my audio equipment under my TV. Center speaker is on the top of the two shelves, and my TV is on a bracket arm suspended over it (looks like a wall mount). I got wood planks that I stained myself, for both the bookshelves and audio equipment shelves.

And you might consider pulling your L/R mains forward a little more. Would help with the center speaker not being so "visually distracting"

If you're absolutely against moving the center speaker forward, you could put a folded blanket there in front of it. Or some sort of audio absorption panel like what you have on the wall, so it would sit on top of the stand and the speaker would sit on top of it.

Will second the smaller equipment shelf as the room is not as deep as it seemed and would help there too.

 

[gorman]

Will second the smaller equipment shelf as the room is not as deep as it seemed and would help there too.

It could not be much shallower (less deep). AVR is quite deep, HTPC too...

 

[RickS]

It could not be much shallower (less deep). AVR is quite deep, HTPC too...

Ok, clearly though am not the only one who though it seemed much deeper than usual though. My wife likes to say your monkey. your circus. 

 

[Ultrasonic]

What is your centre speaker sitting on top of? My main thought would be to rest the back actually on the surface you're worrying about and then angle the front up towards the listening position, or even slightly above given its a coaxial design. This will reduce the amplitude of he reflected signal due to the speakers directivity. It will also increase the angle of the shallowist reflection of the surface, which may in turn mean it bounces over the top of the listening position. Actually placing anything there to provide meaningful absorption over a worthwhile frequency range just isn't feasible.

 

[gorman]

Ok, clearly though am not the only one who though it seemed much deeper than usual though. My wife likes to say your monkey. your circus.

I measured, HTPC case is 42cm deep. Shelf is 60cm deep. So it could be 18cm smaller (7 inches) in that dimension.
I could completely change the furniture piece, adopting a different approach. But, at that point, I wonder if it would be worth it (and I suspect not).

My main thought would be to rest the back actually on the surface you're worrying about and then angle the front up towards the listening position, or even slightly above given its a coaxial design.

The center speaker's tweeter is pointed straight at MLP (between my ears, basically). I could try pointing it a little bit higher, maybe, as you suggest. I *think* the stand on which it is placed is already at maximum angle, 6.5°, but I could check...

... checked before posting. Yeah, it's already at maximum angle (for this stand). I could think about raising the front part of the stand to increase the angle. But there's very little angle available before the front of the speaker occludes the bottom part of the TV from view.

 

[Clmrt]

I have the same situation - furniture is deeper than the speaker. My wife insists all speakers are to live pushed as far back as possible. Only when listening / watching are they to be brought out to where I feel they perform best.

Luckily, I don't measure. Ignorance is bliss, and since everything sounds fantastic, I don't care to see the sins.

So if you just can't live with the speaker being on plane with the mains, baffle flush or just over the edge of the shelf when in use, then go custom. Spend a grand or two on bespoke AV furniture or get a jigsaw and relieve the portion in question. Might even look cool.

 

[Ultrasonic]

The center speaker's tweeter is pointed straight at MLP (between my ears, basically). I could try pointing it a little bit higher, maybe, as you suggest. I *think* the stand on which it is placed is already at maximum angle, 6.5°, but I could check...

Looks like you could get a much greater angle if you didn't use the stand?

 

[gorman]

Looks like you could get a much greater angle if you didn't use the stand?

Theoretically yes, of course. But it's a nice stand and it avoids transmitting vibration to the furniture which is hollow by design and it would likely resonate (hope that's the right word) a lot. I doubt that would be good for sound.

 

[Looneybomber]

A first suggestion was to place the speaker at the front of the shelf. But that, to be honest, would be aesthetically unacceptable for me. It would distract me enormously, making me concentrate all the time on the speaker itself, instead of music and/or video content (I know myself, it happened in a past setup).

As such, I'm asking if there are good suggestions on what kind of material I could use to reduce early refrections, in place of the two black clothes you see in the picture (that are obviously uneffective).

I would imagine the black cloth would be much better used covering the speaker while it’s placed at the end of the furniture. Really, the entire table should be covered in a black towel when watching a movie if you’re easily distracted by reflections from the TV. That would be a win win - better audio and everything is covered/hidden.

 

[gorman]

I would imagine the black cloth would be much better used covering the speaker while it’s placed at the end of the furniture.

The speaker has matte finish. Tried placing the black cloth on top of it... did not make a significant difference in reflections. It has to do with the angle my eyes sit at. Reflections are fine like this.

I kept searching online for options, this is my most recent find:

https://www.amazon.it/dp/B08MC4VWKC/

Would a couple of these in front of the center speaker help with reflections from it? Or is there too much "flat surface" on them?