Advice on REW graph - Page 4 - Home Theater Forum and Systems - HomeTheaterShack.com

Old 03-04-10, 09:14 AM Thread Starter
Shackster
Spy

Join Date: Feb 2010
Posts: 30

I am using 8 Auralex LENRD bass traps + 2 acoustic solutions bass traps ( from a UK based company).

I have read online that there is a formula you can use to get the correct length between the wall and the speakers. It's the height of the room times 0.618. Have you ever heard of this formula? I found that my speakers are placed approximately the correct distance. Around 30 cm shorter actually than what it needs to be.
nasp is offline

Old 03-04-10, 04:27 PM
Senior Shackster
Dan

Join Date: Oct 2009
Location: Mountain View, CA
Posts: 502

I'm going to say something that is contrary to popular practice: placing foam in corners isn't going to do a lot for bass problems. In corners there is a lot of pressure and not much particle velocity. IOW, nothing much to absorb there. Absorbers are better placed 1/4 wavelength of the offending frequency from the boundary in theory, but this tends to place them in the middle of the room. Mechanical dissipation is a far better solution for boundary placement. Read text and view simulations:
http://www.isvr.soton.ac.uk/SPCG/Tut...ding-rooms.htm
Bass is a tricky phenomenon.

Dan
DanTheMan is offline
Old 03-04-10, 04:44 PM
Senior Shackster
Dan

Join Date: Oct 2009
Location: Mountain View, CA
Posts: 502

Quote:
nasp wrote: View Post
I have read online that there is a formula you can use to get the correct length between the wall and the speakers. It's the height of the room times 0.618. Have you ever heard of this formula? I found that my speakers are placed approximately the correct distance. Around 30 cm shorter actually than what it needs to be.
Yea, the old "Golden Ratio." I wish that worked and it does have some reasoning behind it in a theoretical room at a theoretical listening position, with a theoretically perfect speaker, etc..., but other than that it is just experiment until you're happy armed with actual facts. Acoustics is just far to complicated for that amount of reductionism. I'm sure you can find people online who'd say that formula changed their life blah, blah, blah and there's chance that it did. Grant it, there's an exceedingly small chance it made much genuine improvement, but it just doesn't mean there's any real reason for it. IOW, an ordinary room may not and probably doesn't measure any better overall. Too much luck, chance, and wishful thinking involved for me.

Of course there is plenty that can be done with the application of real knowledge.

Dan
DanTheMan is offline
Old 03-04-10, 05:30 PM
Elite Shackster

Greg

Join Date: Nov 2007
Location: NY
Posts: 2,601

The idea is to take the likely problem areas due to one dimension and not reinforce them with additional problems in the same area due to another dimension. In that respect, the theory is sound. Sorry for the pun. In practice, sometimes it works and sometimes it doesn't. Why? Because there's a lot more going on. Your walls aren't perfectly square. They're not even perfectly straight. They're not even perfectly flat. Etc.

That being said, there are a handful of times that measurements have shown me something, I decided on a whim to apply one rule or another, and found that something fixed. Not every time, but enough to not discount trying.

Acoustics is one area where no matter how much you simulate, something will be different in the real world. So experiment and see what works. But make sure some of the "golden rules" are part of your experiments so you can see for yourself.

And I've seen enough experiments to see that corner traps work. But as with all acoustic things, they work at certain frequencies and not at others. And with certain materials, and not with others.

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline
Old 03-05-10, 02:37 AM Thread Starter
Shackster
Spy

Join Date: Feb 2010
Posts: 30

I'll try and move the speakers a bit closer to the corners and run REW and post the results.

The WHOLE wall behind the speakers is also a wardrobe (about 2 feet width) so the bass traps are placed in the corner outside the wardrobe and not inside it. I'll try and put the bass traps inside the wardrobe and take some more measurements and post the results as well. I just thought that by placing the bass traps outside the wardrobe, the back of the speakers will be facing exactly towards the bass traps and there will be better absorption.
nasp is offline
Old 03-05-10, 09:03 AM
Elite Shackster

Greg

Join Date: Nov 2007
Location: NY
Posts: 2,601

Corners are seldom good places for getting smooth response from speakers... how close to the corners are you talking about moving them?

-Greg

Don't worry... nothing new here, I've already made that mistake. Trust me.
glaufman is offline
Old 03-05-10, 09:03 PM
Senior Shackster
Dan

Join Date: Oct 2009
Location: Mountain View, CA
Posts: 502

Oh, one more question: How does it sound now?
and a couple more: what exactly are you trying to do with the foam bass absorbers? The bass shown doesn't seem like it's overwhelming. Are you just looking for a nice "dead end"?

Why not see what happens if you pull them into an area where you have a lot of particle movement?
here's a wavelength calculator: http://mehlau.net/audio/calculator/ just divide that value by 4 and place the bass absorber that far from the corner or wall and see what happens. Keep the patterns in mind from the other site I linked. If I'm crazy, you'll know it then. One other thing is that most foams are pretty broad band absorbers.

Dan
DanTheMan is offline
Old 02-23-13, 09:06 PM
New Member

Join Date: Feb 2013
Posts: 2

Hello Spy,

I have a baby bottle too and i would like to do some measurements. Can i have the cal file? Thank you in advance
pstrav is offline

 Bookmarks

 Tags advice , graph , rew

Message:
Options

## Register Now

Random Question
Random Question #2

User Name:
 PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS! ATTENTION! YOU MUST ACTIVATE YOUR ACCOUNT!Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software. AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED! See our banned email list here: Banned Email List We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration. Email Address:
OR

## Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.