Panel absorbers

Musicmaker · Post by **Musicmaker** » Wed Jul 16, 2003 6:41 am

Hello,

I want to make a basstrap, because I can hear a very heavy bass in the rear of my mixing room, and I can actually can hear it trough my whole house.

After using a testtone from this page http://www.nt-instruments.com/flash_vie ... PageId=465 I have noticed that 40 Hz is causing the heavy bass.

So is it wise to, as written on the SAE site (http://www.saecollege.de/reference_material/index.html), to build a few panel absorbers that have the size 1 meter x 1 meter (3'x 3') and have different depths?

or

Is it possible to make one panel absorber, that absorbs the 40 Hz frequence?

I can imagine the last option would be usable, but isn't it better to absorb more then just that frequence?

Can you give me the sizes also of the panel absorber(s) I need to know?

If it's needed my room's sizes are: Lenth 4 meter and 45 cm, hight 2 meter and 63 cm and 3 meter and 3 cm broad. (2,54 cm = 1')

Thank you!

Ben

Post by **John Sayers** » Wed Jul 16, 2003 9:28 am

Ben - what treatment do you have in your room currently??

cheers
john

Musicmaker · Post by **Musicmaker** » Wed Jul 16, 2003 7:40 pm

Hello John,

I have two panels in my room with the sizes 103 cm x 120 cm and a depth of 12 cm each. They are both filled with 4 plates of rockwool.

I case it's usefull, here is a illustration of my room:

-----
The windows are on this side > | |_
|____| < Here's the door

^
This is the rear of the room

As you can see, there is a gap in the room that leads to the door.

I hope this makes it clear.

Thanks

Post by **John Sayers** » Thu Jul 17, 2003 12:24 am

Mate you need more than Two panels in your room. Have you checked out what others have in their rooms at http://johnlsayers.com/Studio/index.htm ??
cheers
john

Musicmaker · Post by **Musicmaker** » Thu Jul 17, 2003 5:51 am

I like to work to those kind of solutions, but is it possible to get rid of that heavy bass with a relatively simple solution? Like building a basstrap or something?

Post by **John Sayers** » Thu Jul 17, 2003 9:46 am

the bass wouldn't be your only problem - in fact it's probably the least of your problems. Youmust bring the reverb time of your whole room down from where it is - panels of rockwool/insulation will do this but you will need a lot more than you currently have. Once done then you are in a position to see how much bass trapping you will need.

cheers
john

Eric_Desart · Post by **Eric_Desart** » Thu Jul 17, 2003 10:40 am

Just a small comment.

Concentrating on the fact that you hear it in the whole house:
If this is typical 40 Hz there are a few options.

Is there a weak point as door, window?
Your lowest axial room mode at x-axis is 38.6 Hz.
How are the walls made? Drywall? How? This can be a mass-spring resonance making the wall a filter at 40 Hz.

Can be a combination of the above.
Absorption with wool will only help (in function of insulation) for a few dBs.

This does not mean that you probably must upgrade your room as John said.

Creating a panel trap at 40 Hz will worsen the problem. A panel trap is a mass-spring system absorbing at that frequency in the room but simultaniously creates a weak spot in the insulation at the very same frequency. This insulation leakage is much more significant than the absorption.

What seldom is told:
A panel trap can be a good and space saving low frequent absorber, but simultaniouly this absorption is at the expense of the insulation of the wall on which it is mounted (mass-spring), and on a drywall it will shift in frequency (depends on mass ratios) and creates a triple leaf system.

Conclusion:
A panel trap tuned to a specific frequency in order to increase insulation is counter productive and has the REVERSE effect as intended.

Eric

giles117 · Post by **giles117** » Thu Jul 17, 2003 12:08 pm

Welcome Back Eric, where yah been??

Bryan Giles

Musicmaker · Post by **Musicmaker** » Thu Jul 17, 2003 5:49 pm

Thank you for your help.

I am going to focus me on the reverb time of my room.