Help with 40 hz problem in small room

Hello Everybody . I am recording engineer form Caracas Venezuela and i just build a production and mixing room but i am having a very hard time getting it to sound right, my biggest problem is a resonance i have around 41 hz that is driving me mad , if i play a 41hz tone and mute it suddenly, i can hear a 1 sec tail in that frequency and it resonates around all the room being worst at the front and back areas of the room.. The room is 13’7” L 10’8” w 7’5” (4,20 3,30 2,30 meters) I have carpeted floor all around , I also made broadband wood acoustic panels with fiberglass inside and covered in burlap. I used mdf panels in corners covered with 3 inch acoustic foam (please see the pictures to see the configuration. I know the ratios and parallels walls of the room are anything but ideal but is what i have for now, please let me know any advice that you would have to improve the acoustics and get rid of the 40 hz problem... thanks in advance everybody, This forum is great

read stickies, read the forum, place basstraps. wow, that was short! hi and welcome to the JLS forum!

What kind...where??? thanks

Hi Fulltato Stickies are at the top of the list of the forums topics. Concerning your 41hz problem, That frequency is very low, to have a sensible reduction at that frequency you"ll either need to be able to built something that is at least 1/4 of the wavelenght of 41hz in thickness (6.75ft) filled with wool or bulit a tuned panel bass trap or membrane resonator, call it what you want, wich would aslo be huge. All of wich are not aplicable in you situation imho. Six inches deep Broadband traps are definitely not enough to control reflexion at those frequency. More and bigger trapping and in ALL corners (3 inches is far from enough 24 inches would be a minimum), trapping all your ceiling would also help. The smaller the room the more problematic they become especially at low freq. You problem may also reside outside your room , that frequency maybe a reflexion from other boundaries outside you room. In any case, this a simple problem with a complicated solution that woul need a lot more info and lots of money for an acoustic solution. keep looking, good luck.

Can i use Rockwool to make basstraps and solve this problem???

Yes you can use rockwool, Solve your 41hz problem completely, i doubt it, minimize it a little ...probably. Begin with bigger corner traps "superchunk" style, and cover the whole rear wall with the thickness of RW you are ready to loose in floor space. But may i ask if it is absolutely necessary for you to have this 41hz controlled, or does it became a problem when you actualy saw it upon room analysis ? i mean, 41hz is lower than the lowest bass drum i know. I understand you want the best possible acoustic but if you know it's there you can just work around it, no small room is perfect.

Can i use Rockwool to make basstraps and solve this problem???

Yup! It can't do any harm, and will very likely help a bit, even though it won't cure your problem. And as Ethan would say: "You can't have too much bass trapping in a small room". Here's some links about building bass traps that might help: viewtopic.php?t=7278 http://www.cloneensemble.com/basstraps.htm

Ooops! Double post. Sorry!

I wonder if a Helmholtz resonator would work for you? I'm not sure how big it would have to be to kill your 41Hz problem, or even if it's feasible, but I do know that you can tune them fairly accurately to hit specific problem frequencies. Maybe one of the experts can comment on whether that would work or not? My guess is that, for such a low frequency it would have to be pretty big to have a noticeable effect on your room.

hi! i have similar problem at 56 hz, and all we can do is to put as much tick, rigid rookwool in all corners as we can afford. i would start with four where you put that foam, (btw. that foam doesn't have much effect on low freq.) you should probably make something similar to mine, as deep as possible. viewtopic.php?f=3&t=11285 If that doesn't help you still have many corners in your room... 8 more to be specific... hope it helps.

hi! i have similar problem at 56 hz, and all we can do is to put as much tick, rigid rookwool in all corners as we can afford. i would start with four where you put that foam, (btw. that foam doesn't have much effect on low freq.) you should probably make something similar to mine, as deep as possible. viewtopic.php?f=3&t=11285 If that doesn't help you still have many corners in your room... 8 more to be specific... hope it helps.

hi! i have similar problem at 56 hz, and all we can do is to put as much tick, rigid rookwool in all corners as we can afford. i would start with four where you put that foam, (btw. that foam doesn't have much effect on low freq.) you should probably make something similar to mine, as deep as possible. viewtopic.php?f=3&t=11285 If that doesn't help you still have many corners in your room... 8 more to be specific... hope it helps.

I wonder if a Helmholtz resonator would work for you?

Altough they work at low frequency,they usually are more suited for broadband low-mid control. That being said building a slat resonator tuned at 41hz would look like this : slats 1 inch thick by 8 inches wide spaced 1/8 inches appart with a 3 feet deep cavity behind the slats. there are myriad of variation but they all take lots of space. If you are willing to loose 3 feet of floor space that could be a solution.

First of all thanks for your help guys ....I am concerned with this very lows because there is a very annoying resonance in that area that is driving me nuts... if i could take care of that I would not care to have a peak in that frequency and compensate for it with eq or something ,,,I think i am going to do rock wool superchunk in the corners and rockwool panels in the backwall

The traps links are appreciated. Superchunk seems like a popular solution. Thanks guys. W

WayneD wrote:

The traps links are appreciated. Superchunk seems like a popular solution. Thanks guys. W

You might want to try make some of this wooden box and place at room corner, dont need insulation inside ( to maintain sharp Q) if your 41Hz problem is serious, its basically a 42hz Helmholtz Resonator , I have make about 8 sets tune to 70hz spread at all room corner for my friend , and it really cure his serious 70hz problem better than those broadband bass trap... do let me know the outcome if you try it....or anyone here have other bass frequency problem, and want to built some but need the dimension, can email me . :D