Building membrane resonators?? DIY or should I buy them?

Dear Mr. Sayers. I live in Germany I am a composer just starting my business to go the commercial route in composing. I was mixing long time my own music but I moved to anther place and the room-acoustics in the new place went crazy. The dimensions of the room are very poor: 1:1,2:1,9 We have done measurements with a professional of my new small Home-Studio-Room, 22 square meters. We found out what our ears heard we have two huge resonances 50 HZ and 100 HZ. To our surprise above 100 HZ everything is fine. I want to get rid of those resonances but I cant afford commercial membrane resonators and broadband corner absorbers would meassure about 2400 mm in the corner the long side? The advise was to build two resonators for each frequency and place them in the room. I understand the principle of those membrane resonators but another advise by the professional was only to go the DIY route if I have detailed building plans. I know it is your best secret and many testing and trying went into detailed plans. But this is serious decision for me because I am not Hans Zimmer. :mrgreen: Thanks for doing this forum.... Hendrix PS: If you want I can PM you waterfall plots!!

welcome! please update your profile with your location. can you post the actual room dimensions, perhaps some photos and a pic of the waterfall plot?

gullfo wrote:

welcome! please update your profile with your location. can you post the actual room dimensions, perhaps some photos and a pic of the waterfall plot?

I do not want to make him feel I am sneaking behind his back. So it is better not to post the waterfall but I can PM you this one!! This is the room dimensions. There is one Brradbandabsorber for mid lows and high-f behind the monitors already build. On the left two windows ceiling and floor is wood construction. Ethan Winer at GS mentioned to build corner chunks long side 90 centimeters, whole corner filled with mineral wool. But I have my doubts that those would work at the resonances.

looking at the mode calculations, it could be due to height or depth (based the room ratio of 1:1.16:1.88) ax 1st ax 2nd h 53.82 107.63 d 46.42 92.84 what do you have overhead? based on the waterfall and spectrum plots, there is something around 315 or so (which in the mode calculator is 322) so i'm inclined to think its a floor-ceiling mode.

gullfo wrote:

looking at the mode calculations, it could be due to height or depth (based the room ratio of 1:1.16:1.88) ax 1st ax 2nd h 53.82 107.63 d 46.42 92.84 what do you have overhead? based on the waterfall and spectrum plots, there is something around 315 or so (which in the mode calculator is 322) so i'm inclined to think its a floor-ceiling mode.

Interesting. Yet above my head there is nothing I was thinking about to build a cloud. What would you suggest to build?

maybe something like this? download/file.php?id=37117&mode=view

gullfo wrote:

maybe something like this? download/file.php?id=37117&mode=view

This would be a complete redesign I just search for first aid and when the royalties go up I can do a redesign. My guesswork from what I hear is when I am playing sine tones. Building these four resonators two for each resonance. Building a 3 square meter cloud. Building on the sides where are the windows and the doors are movable absorbers at the first reflection points. Are there any resonator designs on this forum?

i only meant that in terms of the clouds, not the rest of the design :)

I understand. Would this design work for the resonators. The formula I have is just in metric kg and centimeters. but the layout 4" to 2" ...would this be OK?

that's a panel absorber design and should work. you want to identify the locations where the pressure on those frequencies is greatest and place them there. play the tones and by sweeping the room with a mic (use a mic stand without the base) near the ceiling and using an RTA, you should be able to find it pretty quickly.

gullfo wrote:

that's a panel absorber design and should work. you want to identify the locations where the pressure on those frequencies is greatest and place them there. play the tones and by sweeping the room with a mic (use a mic stand without the base) near the ceiling and using an RTA, you should be able to find it pretty quickly.

It is that drastic at 50 hz and 100 hz that you can hear it when you go near the back wall or the corners in the back. But I will do the mic thing as well. Most common mistakes when building those panel absorber? Is there a formula how I can get information about the Q factor?

i'm not sure there is a way to calculate the Q but the closer the insulation is (including lightly touching it) the more damping is applied with a corresponding loss of peak efficiency in exchange for wider bandwidth. consider thinner panels over thicker ones and if it turns out to be depth related, consider polycylinders as a option for trapping as well as diffusion.

gullfo wrote:

i'm not sure there is a way to calculate the Q but the closer the insulation is (including lightly touching it) the more damping is applied with a corresponding loss of peak efficiency in exchange for wider bandwidth. consider thinner panels over thicker ones and if it turns out to be depth related, consider polycylinders as a option for trapping as well as diffusion.

Thank you so much for this basic information. So taking out the insulation results in a sharp Q. What would you consider from seeing the measurements? More broad or a sharp Q? What are polycylinders never hared about that concept?

polycylinders - "poly" diffusers. most times thin plywood with damping bent by pressing between two strips of wood - vertical or horizontal. i would go with a wider Q since exactly targeting a problem frequency can be tough. also, having the panel sit on spongy rubber or padding can allow for some adjustments to be made by tightening or loosening the screws holding it on.