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Are acoustic panels size proportional to room size? - Page 2

post #31 of 55
3/5/13 at 3:29pm
Quote:
Originally Posted by Ethan Winer View Post

The best place for a bass trap is wherever in the room bass builds up. This is usually in the corners, but the entire rear wall is also a good candidate. This short article and file download will help you find the best places for bass traps:

Pink noise aids placing bass traps

--Ethan

im curious: why do you recommend listening to identify areas of high pressure within the room (as our ears are sensitive to pressure), to subsequently place velocity-based porous LF absorbers?
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post #32 of 55
3/5/13 at 6:33pm
so then then corner where my sub is now as this location is where the sub crawl proved to be the ideal placement location?
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post #33 of 55
3/6/13 at 11:12am
Quote:
Originally Posted by mominayal View Post

so then then corner where my sub is now as this location is where the sub crawl proved to be the ideal placement location?

I'm not a big fan of the "sub crawl" for many reasons. Assessing frequency response by ear is never as good as actually measuring. Another problem is the music you play when "crawling" is in a specific key and plays only frequencies related to that key. Maybe those frequencies will align with the room's peak and null frequencies, and maybe they won't. Really, the only way to know which location is best is to measure the room using proper software:

Room Measuring Primer

You're 95 percent of the way there with all the gear you bought! Go the last 5 percent to achieve the best result possible.

--Ethan
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post #34 of 55
3/6/13 at 11:48am
Hmmm... I measure, but have tried the sub crawl. Never thought about doing it with music, however, I used pink noise and test tones. And an SPL meter for grins. I do agree it is way too easy to trick the ears when certain frequencies resonate, giving the false impression of more bass since only a few frequencies were really excited, but it was an interesting exercise. And, with a couple of heavy subs, "exercise" was ineed involved. smile.gif
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post #35 of 55
3/6/13 at 11:49am
Quote:
Originally Posted by localhost127 View Post

im curious: why do you recommend listening to identify areas of high pressure within the room (as our ears are sensitive to pressure), to subsequently place velocity-based porous LF absorbers?

Off of Ethan's site.
Quote:
FIND WHERE THE BASS LIVES

All room acoustic problems are caused by reflections from the walls, floor, and ceiling. Therefore, absorption is best placed where the reflections occur. At mid and high frequencies these locations are easy to determine. But bass tends to collect in the corners, and some frequencies may end up more in one corner than another and vice versa - depending on the loudspeaker and subwoofer locations and other factors. So the goal is to find where bass energy accumulates the most, and put your bass traps there.


You should try it.. It does indeed work. wink.gif
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post #36 of 55
3/6/13 at 11:52am
Quote:
Originally Posted by Ethan Winer View Post

I'm not a big fan of the "sub crawl" for many reasons. Assessing frequency response by ear is never as good as actually measuring. Another problem is the music you play when "crawling" is in a specific key and plays only frequencies related to that key. Maybe those frequencies will align with the room's peak and null frequencies, and maybe they won't. Really, the only way to know which location is best is to measure the room using proper software:

Room Measuring Primer

You're 95 percent of the way there with all the gear you bought! Go the last 5 percent to achieve the best result possible.

--Ethan

What about an instrumented sub crawl using sweeps and a measurement microphone to find the location with the best measured response you can find? Divide the room into a grid pattern and measure at each coordinate sort of thing. Is that what is meant in your article when you write: "So if you're using REW to help find the best location for a subwoofer"?
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post #37 of 55
3/6/13 at 12:59pm
Quote:
Originally Posted by DonH50 View Post

Hmmm... I measure, but have tried the sub crawl. Never thought about doing it with music, however, I used pink noise and test tones. And an SPL meter for grins. I do agree it is way too easy to trick the ears when certain frequencies resonate, giving the false impression of more bass since only a few frequencies were really excited, but it was an interesting exercise. And, with a couple of heavy subs, "exercise" was ineed involved. smile.gif

I've done the reverse, measurements, then sub crawl with RS spl.and specific banded test tones to dial in location, and re confirm with full sweep.

It was more a tie the theory to real world moment for me, what my bass traps were and were not doing, diminishing returns of adding more bass traps, etc.
my wife....well it's my hobby not hers. smile.gif


Sent from my 32GB iPhone4 using Tapatalk
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post #38 of 55
3/6/13 at 1:09pm
Quote:
Originally Posted by myfipie View Post

You should try it.. It does indeed work. wink.gif

im afraid it still doesn't answer my question of why one would identify areas of high pressure in order to place velocity-based porous absorbers.
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post #39 of 55
3/6/13 at 2:27pm
Quote:
Originally Posted by JD in NJ View Post

What about an instrumented sub crawl using sweeps and a measurement microphone to find the location with the best measured response you can find? Divide the room into a grid pattern and measure at each coordinate sort of thing. Is that what is meant in your article when you write: "So if you're using REW to help find the best location for a subwoofer"?

To me a "crawl" means you put the subwoofer up on your chair or couch, then crawl around on the floor to find the complementary location for the sub. If you're actually measuring the response, you can skip all that and just measure, move, measure, move until you find the place that gives the best response. Further, since you can never place a sub exactly where your ears would be, that introduces additional errors.

--Ethan
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post #40 of 55
3/6/13 at 2:29pm
Quote:
Originally Posted by myfipie View Post

You should try it.. It does indeed work. wink.gif

Indeed. It amazes me that some people refute techniques that have been proven to work thousands of times using hard data in the form of response graphs and waterfall plots. If putting bass traps in corners (and other proven locations) didn't work, nobody would do that! rolleyes.gif

--Ethan
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post #41 of 55
3/6/13 at 3:03pm
Quote:
Originally Posted by Ethan Winer View Post

Indeed. It amazes me that some people refute techniques that have been proven to work thousands of times using hard data in the form of response graphs and waterfall plots. If putting bass traps in corners (and other proven locations) didn't work, nobody would do that! rolleyes.gif

--Ethan

and just what does "putting bass traps in corners" have to do with your recommendation to play pink noise and walk around the room to find areas of high pressure in order to subsequently place velocity-based porous absorbers.

correlation != causation
Edited by localhost127 - 3/6/13 at 3:11pm
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post #42 of 55
3/7/13 at 4:47am
Thread Starter 
Orginal plan was to not get to involved and just put up a few panels like

1.directly behind front speakers LCR

2.bass traps in all four corners (I've decided 17" is the maximium for the upper corner traps stuffed w/9.5" of rockwool small but thick).

if you Guy's still think a 17" triangle is to small then I may opt for the ATOM-12 System
http://www.auralex.com/category_bass_traps/category_bass_traps.asp
I'm curious if the Atom12 can be covered w/ white cloth?

3.first reflection points on side wall.

4.rear wall diffussor.
Then in future cieling panels.

I'm concidering a Radio shack SLP meter to narrow down where bass traps are needed.
Do SPL meters have a switch for mearsuring bass then another switch for mids and highs? or do'es it just mearsure BD levels?
Here's a image of the plastic panels W18"xH36"xD2" I was planning on stuffing the rockwool inside then covering w/ cloth.

From what I understand about panels is w/ fiberglass it's required to have a air gap inbetween the fiberglass and wall however w/ rockwool the panel can be stuffed covered and attach directly to wall is this true or false?

edit:why can't I attach images here?




STB
Edited by stevethebrain - 3/10/13 at 7:17am
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post #43 of 55
3/7/13 at 1:21pm
Quote:
Originally Posted by stevethebrain View Post

1.directly behind front speakers LCR

That's probably the least useful place to put absorbers, because your speakers fire the opposite direction. The only time I'd put absorbers behind speakers is if the speakers are dipoles that radiate equally front and back.
Quote:
2.bass traps in all four corners (I've decided 17" is the maximium for the upper corner traps stuffed w/9.5" of rockwool small but thick).

Rectangle rooms have 12 corners, not just four where walls meet other walls. A bass trap only 17 inches wide is not going to do much below a few hundred Hz. I'd say 24 inches across the face is a minimum, and wider is even better.
Quote:
3.first reflection points on side wall.
4.rear wall diffussor.
Then in future cieling panels.

Sure.
Quote:
Do SPL meters have a switch for mearsuring bass then another switch for mids and highs? or do'es it just mearsure BD levels?

It doesn't really work that way. The best way to measure a room is with software meant for that:

Room Measuring Primer

But you don't really need to measure at all unless you want to.

I think that plastic may be too thick to put in front of a bass trap.

--Ethan
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post #44 of 55
3/7/13 at 6:20pm
An air gap will help any (velocity-based) absorber. Ethan's website has an article talking about that, too.
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post #45 of 55
3/7/13 at 11:11pm
Quote:
Originally Posted by Ethan Winer View Post

That's probably the least useful place to put absorbers, because your speakers fire the opposite direction. The only time I'd put absorbers behind speakers is if the speakers are dipoles that radiate equally front and back.

Though let's not forget about SBIR - considering most people have their mains ~2 feet from the front wall, SBIR related nulls are very common!
Moe on SBIR for those interested: http://gikacoustics.com/speaker-boundary-interference-response-sbir/
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post #46 of 55
3/8/13 at 11:28am
Quote:
Originally Posted by GIK Acoustics View Post

Though let's not forget about SBIR

Of course, good point. I usually diss front wall absorption because most people use rigid fiberglass only 1 inch thick.

--Ethan
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post #47 of 55
3/8/13 at 12:25pm
The other common exception, which happens to be mine, is dipoles. My front wall is filled with absorbers (4" thick, about 2" - 4" off the wall) and as a result the image from my Maggies is rock-solid. Spaciousness comes from the recording, if there, and is not artificially added by the room. It is a trade as many do not like a "dead" room, but it works for me. It is also a rather small room with some doubled modes so I was also trying to increase LF absorbtion, always a painful thing.
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post #48 of 55
3/9/13 at 10:37am
Quote:
Originally Posted by Ethan Winer View Post

Of course, good point. I usually diss front wall absorption because most people use rigid fiberglass only 1 inch thick.

--Ethan

Yeah, I agree.
Quote:
Originally Posted by DonH50 View Post

The other common exception, which happens to be mine, is dipoles. My front wall is filled with absorbers (4" thick, about 2" - 4" off the wall) and as a result the image from my Maggies is rock-solid. Spaciousness comes from the recording, if there, and is not artificially added by the room. It is a trade as many do not like a "dead" room, but it works for me. It is also a rather small room with some doubled modes so I was also trying to increase LF absorbtion, always a painful thing.

Yes, definitely. I believe we all also agree if you're going to absorb the front wall - this is the way to do it. At least 4" thick, air gap if possible.
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post #49 of 55
3/10/13 at 7:16am
Thread Starter 
Quote:
Originally Posted by Ethan Winer View Post

That's probably the least useful place to put absorbers, because your speakers fire the opposite direction. The only time I'd put absorbers behind speakers is if the speakers are dipoles that radiate equally front and back.
Rectangle rooms have 12 corners, not just four where walls meet other walls. A bass trap only 17 inches wide is not going to do much below a few hundred Hz. I'd say 24 inches across the face is a minimum, and wider is even better.
Sure. What do you mean sure yes this is a good starting point or sure it mite work?
It doesn't really work that way. The best way to measure a room is with software meant for that:

Room Measuring Primer

But you don't really need to measure at all unless you want to.

I think that plastic may be too thick to put in front of a bass trap. Plan to have the plastic be the back of trap

--Ethan

Quote:
Originally Posted by Ethan Winer View Post

Of course, good point. I usually diss front wall absorption because most people use rigid fiberglass only 1 inch thick.

--Ethan
what is the definition of diss.?how do you separate a reponse "quote" message?

Quote:
Originally Posted by GIK Acoustics View Post

Though let's not forget about SBIR - considering most people have their mains ~2 feet from the front wall, SBIR related nulls are very common!
Moe on SBIR for those interested: http://gikacoustics.com/speaker-boundary-interference-response-sbir/
I have my mains ~2 feet from the front wall
so will it be worth the effort to have front wall panels directly behind mains?

Quote:
Originally Posted by GIK Acoustics View Post

Yeah, I agree.
Yes, definitely. I believe we all also agree if you're going to absorb the front wall - this is the way to do it. At least 4" thick, air gap if possible.
I was planning on using 3 1/4" rockwool laying on the 1 1/2" ridges (note the inside of plastic panel. this will provide a air gap).

STB
Edited by stevethebrain - 3/10/13 at 7:25am
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post #50 of 55
3/10/13 at 11:39am
Quote:
Originally Posted by stevethebrain View Post

what is the definition of diss.?

Dismiss, or (the ghetto definition) disrespect.
Quote:
how do you separate a reponse "quote" message?

Not sure what you're asking.

--Ethan
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post #51 of 55
3/11/13 at 5:23am
Thread Starter 
[.
Not sure what you're asking.

--Ethan[/quote]in post #43 you separated each of my comments and responded to each individualley. how is this done?
STB
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post #52 of 55
3/11/13 at 7:10am
Quote:
Originally Posted by stevethebrain View Post

I have my mains ~2 feet from the front wall
so will it be worth the effort to have front wall panels directly behind mains?
I was planning on using 3 1/4" rockwool laying on the 1 1/2" ridges (note the inside of plastic panel. this will provide a air gap).

STB

STB,

SBIR is somewhat mysterious, as in: it is really strong in some rooms, and not so much in other rooms. So it's really hard to suggest it without knowing the room. The easiest way to test would simply be while you're building some panels, put two behind the mains and give a listen. If you hear a big difference, keep them there. If not, then find a more effective place for them.
Quote:
Originally Posted by stevethebrain View Post

in post #43 you separated each of my comments and responded to each individualley. how is this done?
STB

Edit: Ethan has posted a better explanation as I forget which forums have code tags!
Edited by GIK Acoustics - 3/11/13 at 5:05pm
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post #53 of 55
3/11/13 at 3:30pm
Quote:
Originally Posted by stevethebrain View Post

in post #43 you separated each of my comments and responded to each individualley. how is this done?

I'll use the Code tags which lets you show anything including special formatting commands. Here's the first part of this same post by me that you're reading right now:
Code:
[quote name="stevethebrain" url="/t/1458191/are-acoustic-panels-size-
proportional-to-room-size/30#post_23066266"]in post #43 you separated
each of my comments and responded to each individualley. how is this
done?[/quote]

I'll use the Code tags which lets you show anything  including special
formatting commands. Here's the first part of this same post by me that
you're reading right now:

[quote]Here's something else you asked.[/quote]

Here's my reply.

As you can see, you can quote with the full prefix to provide a link back to the original post, or use only the words quote and /quote inside the brackets to skip that and show just the text. The forum software provides the full prefix with link. I generally use the full version the first time, then the shorter version for remaining quotes and replies.

--Ethan
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post #54 of 55
4/2/13 at 5:57am
Thread Starter 
Quote:
Originally Posted by Ethan Winer View Post

I'll use the Code tags which lets you show anything including special formatting commands. Here's the first part of this same post by me that you're reading right now:
Code:
I'll use the Code tags which lets you show anything  including special[code]
OK
formatting commands. Here's the first part of this same post by me that
Code:
OK
you're reading right now:
Code:
OK
Here's my reply.[/code]

As you can see, you can quote with the full prefix to provide a link back to the original post, or use only the words quote and /quote inside the brackets to skip that and show just the text. The forum software provides the full prefix with link. I generally use the full version the first time, then the shorter version for remaining quotes and replies.

--Ethan
Code:
this is what I tryed.
1.reply to quote

2.curser to end of sentence I'd like to respond to

3.click code function then type my message.

I think my mistake was to write outside the code brackets?


One more ? can these ORQ diffussers be used at the first reflection points of the main speakers?

Thanks STB
Edited by stevethebrain - 4/2/13 at 6:07am
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post #55 of 55
4/2/13 at 11:03am
I used code tags only to show you how to use the quote tags.

I am not a fan of diffusion at reflection points. To my ears absorption is much better:

Early Reflections

--Ethan
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