BIG problems at 40Hz

Hi! I have a room: 4 x 3 x 2.4m. I efficiently absorbed most freqs, but the frequencies around 40-41 Hz are very very loud. Those frequencies seem to be fundemental freqs of my room. Or why else would they be so loud? Is there a way to cure this efficiently? I only have two corners available for treatment in the back of the room. And one corner in the front (because of the door). But then it wouldn't be symmetrical any more. Or it doesn't matter for such low freqs? Thanks!

Move your measuring position to determine which dimension or dimensions are causing the issue. Then you can put up some targeted Helmholz or sealed membrane absorbers that will get down that low. Just don't try to target 40Hz as a center frequency or you can actually cause more issues than you fix.

bpape wrote:

Move your measuring position to determine which dimension or dimensions are causing the issue.

How do I do that? Do you have any links about this? The loudest note is D#, followed by E (around 40Hz). One octave up is quite normal. This is happening at my listening position.

Aloha Ermi, Have you tried calculating the room modes? (requires Excel) http://www.harman.com/wp/index.jsp?articleId=131 If I've applied your measurements correctly (L x W x H): Length: 4 m = 13.1232 ft (decimal) 13' - 1 5/10" (feet, inches and tenths-of-an-inch) Width: 3 m = 9.8424 ft (decimal) 9' - 10 1/10" (feet, inches and tenths-of-an-inch Height: 2.4 m = 7.87392 ft (decimal) 7' - 10 5/10" (feet, inches and tenths-of-an-inch) then, it would seem that you do have standing wave a @ 43Hz. 1st 2nd 3rd 4th 72Hz 144Hz 216Hz 289Hz 57Hz 115Hz 172Hz 230Hz 43Hz 86Hz 130Hz 173Hz Attached are the results of the info entered from above. In my first thread: http://johnlsayers.com/phpBB2/viewtopic ... ght=#15644 Steve (Knightfly) replied to a similar question I had with:

Distance to wall behind speakers will change response drastically - there is a wall bounce calculator on the Acoustics forum that's fun to play with (needs Excel) Moving either speakers or your head by as little as an inch or two can sometimes make drastic changes in response, due to modal peaks and dips; here's a useful calculator for figuring this. http://www.harman.com/wp/index.jsp?articleId=131 I cut and paste the length and width graphs alongside a scaled room diagram (after scaling them to the same size as the walls) and draw red lines across the room where peaks and nulls are, then green lines where there are NO peaks or nulls - anywhere there's a green intersection is a candidate for speaker or head placement, keeping in mind you need plane symmetry in a mix room (head in center side to side) and an equilateral triangle for speaker/head placement (or at least an Isoscelese triangle)

If I understand this correctly, we want to position ourselves where there is: - no peaks or nulls - front to back - a plane symmetry in mix position (head in center, side to side) - an equilateral triangle for speaker/head placement (or at least an Isoscelese triangle - no peaks or nulls - ceiling to floor If you could post: - a drawing or pic of your room - measurements of your ears at listening/mix position from the front wall - measurements of your ears at listening/mix position from floor to ceiling it would be helpful to further determine any possible courses of action. Hope this helps. Aloha 8)

Thanks kendale! Yes I already did the calculations at the SAE site. But now I found out that my room is actually sligtly bigger, it's more around 4.2m. Now it all makes more sense. :lol: Because I was running a sine wave with TrueRTA (http://www.trueaudio.com/rta_abt1.htm) and it was definitely around 40-41hz. I also tried to move the speakers 10cm further away from the rear wall, but it didn't make a noticeable difference. Maybe I should try a greater distance. I'll upload some fresh pictures ASAP, in the mean time you can see the ones that I made in an older thread. Some furniture was removed, absorbers added, but the listening position is still the same. http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4348

If you're getting an issue tied to room length, then the measurment/seating position should be moved to minimize interaction with the modes. Generally, 38% is considered the best place to minimize modal interactions for the length dimension. While this may not be the whole answer, it's a start to verify that this is actually the issue.

Ok, I'll try in the weekend when I get home. I got some fresh pictures now: Front (I'm mostly using the big speakers, the small ones don't go to 40hz): Back, right side: Back, left side:

Aloha Ermi, Nice pics, big improvement to the room (compared to old pics).

I also tried to move the speakers 10cm further away from the rear wall, but it didn't make a noticeable difference. Maybe I should try a greater distance.

Have you tried moving your position back (say about 1.5m from the front wall)? Could it be possible that you are positioned in a peak? Here's a link that might be helpful: http://www.johnlsayers.com/phpBB2/viewt ... light=null Aloha 8)

Aloha Ermi, How's it going? Any luck with the positioning of things? Thought this might be helpful. Check out Steve's (Knightfly) post: "About Traps" http://johnlsayers.com/phpBB2/viewtopic.php?t=5401 Aloha 8)

Hello! Sorry for not replying for all this time. I probably didn't get email notifications and then just forgot about this forum. :lol: Thanks again, kendale, for the links! Anyway I tried some positioning combinations (of myself and the speakers) and they DO make a noticeable difference. Basically now I just moved backwards 0.5-1m. There might still be a bit too much of 40Hz, but it's ok, also because so I can clearly hear problems that might occur in similarly-problematic enviromnments. I can still go back for another 0.5m or so and there the 40Hz almost disappear. Hope this can be useful info for someone else, too. At first I thought that bass traps were the only solution. Sure they might still be very useful, but bass traps alone couldn't make enough difference, IMHO.

Kendale, I posted a new location for the harmon calculator; it's here http://www.johnlsayers.com/phpBB2/viewtopic.php?t=5801 ermi, you're right; neither positioning nor treatments alone will usually fix a room; you need both. And for me, it's easier to first get the best positioning - this, because any changes will be more apparent if they aren't already damped/absorbed/evened out with treatments. then, once everything is in best possible position, the treatments will finish up the job... Steve

I couldn't agree more. Get the speakers and seat (and potentially subwoofer) in the best arrangement first - THEN deal with the treatments. You'll find it much easier and the differences much more apparent prior to treatment.