reflections behind speakers

[skiroy]

My monitors are about 6 inches from the wall. Do I need to treat it for reflections?

[Audiop]

Yes!

Ideally the absorbtion should be good for the frequency of first destructive interference. Below that the reflection are constructive which means the direct and reflected sound will be in phase.

A speaker should be designed for a specific distance from the wall and absorbtion should be used for that specific situation.


/Peter

[danbronson]

Originally Posted by Audiop

Yes!

Ideally the absorbtion should be good for the frequency of first destructive interference. Below that the reflection are constructive which means the direct and reflected sound will be in phase.

A speaker should be designed for a specific distance from the wall and absorbtion should be used for that specific situation.


/Peter

I have a number of problems with everything you just said. For one thing, I wouldn't want constructive interference coming from my walls either, it is equally as problematic as destructive interferance. Another thing, there will not be one destructive frequency and a bunch of constructive ones, as it seems you're saying. There will be many alternating constructive and destructive frequencies as you move up the frequency spectrum. So a tuned absorber wouldn't cut it. But also, as soon as you move your head even a little, the constructive and destructive frequencies will change completely, because the distance between your head, the speakers and the wall has changed.

It's best to make sure there are no nearby reflective surfaces either by designing the room that way in the first place or by using broadband absorbers in key locations. So to answer the original poster's question, yes.

[Ethan Winer]

Originally Posted by skiroy

My monitors are about 6 inches from the wall. Do I need to treat it for reflections?

See this:

Front Wall Absorption

Also, speakers close to a wall can be a problem at low frequencies, but sometimes it's better to be very close than farther away. An overall LF boost from being very close is often better than the severe peaks and deep nulls that happen when the speakers are a few feet away from a wall.

--Ethan

[Audiop]

Originally Posted by danbronson

I have a number of problems with everything you just said. For one thing, I wouldn't want constructive interference coming from my walls either, it is equally as problematic as destructive interferance. Another thing, there will not be one destructive frequency and a bunch of constructive ones, as it seems you're saying. There will be many alternating constructive and destructive frequencies as you move up the frequency spectrum. So a tuned absorber wouldn't cut it. But also, as soon as you move your head even a little, the constructive and destructive frequencies will change completely, because the distance between your head, the speakers and the wall has changed.

It's best to make sure there are no nearby reflective surfaces either by designing the room that way in the first place or by using broadband absorbers in key locations. So to answer the original poster's question, yes.

Well if you read what I wrote instead of putting words in my mouth maybe you would have less problems.

Oh, and if you do not want constructive "interference" from any walls you may have better luck (and even less problems) if you listen outdoors.

Now, read my first post again, think a lot more than you did and write a new repsonse pretending you never wrote your first. Then maybe we can have a constructive conversation..


/Peter

[danbronson]

Originally Posted by Audiop

Well if you read what I wrote instead of putting words in my mouth maybe you would have less problems.

Oh, and if you do not want constructive "interference" from any walls you may have better luck (and even less problems) if you listen outdoors.

Now, read my first post again, think a lot more than you did and write a new repsonse pretending you never wrote your first. Then maybe we can have a constructive conversation..


/Peter

Someone piss in your cornflakes this morning? Chill.

[Audiop]

I'm sure you can find other places to discuss urine and cornflakes. I'm here for constructive discussion regarding music and audio.


/Peter

[tINY]

I'm not sure I agree with your dogma...

In practiacal terms, any frequency low enough to diffract to the rear of the speaker won't be absorbed by 6" of anything I am aware of. So, your comments could be misleading to anyone who doesn't understand the physics already.



-tINY

[danbronson]

Originally Posted by tINY

I'm not sure I agree with your dogma...

In practiacal terms, any frequency low enough to diffract to the rear of the speaker won't be absorbed by 6" of anything I am aware of. So, your comments could be misleading to anyone who doesn't understand the physics already.



-tINY

To paraphrase the article Ethan posted, typically, speakers will radiate below 500 Hz in all directions. Under 350 Hz, things get pretty omnidirectional.

A good 6" absorber with a gap behind it should be able to absorb effectively down to around 100 Hz or even lower from what I've seen. And in fact, a single 6X24X48" panel of Roxul Safe'n'Sound that I put between/behind my nearfields cured the response of a null at 100 Hz pretty effectively. I expected it to take a lot more than that but it did the job.

Just my experience anyway...

[dangoudie]

I've been looking to do something like this too.
I wasn't sure what kind of thing to go for bu subsequent to reading that RealTraps thing above I think the appropriate thing would be something like thick, dense audio-foam across the front wall at the level of the speakers?

[tINY]

Originally Posted by danbronson

To paraphrase the article Ethan posted, typically, speakers will radiate below 500 Hz in all directions. Under 350 Hz, things get pretty omnidirectional.

A good 6" absorber with a gap behind it should be able to absorb effectively down to around 100 Hz or even lower from what I've seen. And in fact, a single 6X24X48" panel of Roxul Safe'n'Sound that I put between/behind my nearfields cured the response of a null at 100 Hz pretty effectively. I expected it to take a lot more than that but it did the job.

Just my experience anyway...

I'm gonna guess that you damped out a room node...

But, it's hard to get an air gap behind 6" of material when the monitors are only 6" from the wall. It's better to get 12 pannels of 4" material and straddle corners with them, generally.



-tINY

[Dean Roddey]

I have 10" of 703 behind my speakers, and that was one of the key components to getting a really flat response in my room. As Ethan indicated above, I have done better getting closer to the back wall and using a lot of absorption to deal with the close distance to the wall, than getting further from the wall, which exacerbated my response problems far more. I also have an unopened box of 703 on the floor below the speakers (so that's 12") with 10" stacked up in two vertical rows (4x4) behind the speakers on top of that box, and then a 6" on the wall/ceiling corner above the speakers.

Those all contributed heavily to response improvements, though the most important one for me by far was the ceiling above me (where I have a 4x4 6" 'cloud' with 5 more raw panels of 703 on top of that, for 16" worth.) If you have the usual 8" ceilings, it'll probably be one of your biggest problems.

* And of course I have the usual wall corners and wall/ceiling and wall/floor corners to either side covered heavily as well.

[atiller]

Wow, 16"?!

I'm just now figuring out what I want to do with my mixing room in the new apartment. I had planned to use the usual 4'x2'x4" panels everywhere, but now you have me worried!

[Dean Roddey]

Here's a thread from the studio construction section (though I don't flatter myself that it's a 'studio' by any means.) There are some pictures there.

The end of my room tuning adventures