Bass traps? (to solve a suck out)


I have a terrible suck out at 61Hz. What should I do to address, I cannot move my subwoofer or room.
gchuva
if you have a wide null centered at 61 Hz, your best bet is to try and cross a sub over a bit higher than 61 Hz and boost that null. just be careful not to create other issues with the added low freq energy released into the room. if you use a RTA while you are tweaking the sub settings to properly mate the sub to your main speakers, you can see the results with each turn of the knob. in the end, you will find this to be a very tedious process that can drive you insane.
This shows a before and after where a suckout at 75 Hz is completely removed Minitraps

The entire demonstration is on the Minitraps Demonstration video

Since this room is probably particularly bad -I don't think you can typically expect a dramatic 15 db improvement but you get the idea.

Broadband bass absorption will normally improve suckouts but each room will behave differently. There are some articles on how to determine placement on Realtraps site too.

Note that minitraps are not the most you can apply for bass absorption as they are 3 1/4 inches thick. The minitraps are very practical and useful for both corners and walls - a great all round product. However, specifically for a corner, the Tri-traps I use are actually thicker as they fit all the way into a corner.
Onhwy61

If you're treating reflections properly, you're treating both nulls and peaks.

For treating 61 Hz, I would consider 1/4 to 1/2" membranes, 3 to 4' wide and 6 to 8' tall. That would be with a practical 4 to 6" depth and 703/705 dampening. I haven't done the math yet but that's based on my work with 4' by 2' membrane panels which were efficient around 100 Hz. Not likely to buy anything that size off the shelf because it's just too big to ship. I wouldn't even consider "soft" traps for this frequency.

I wonder if there's a market for membrane trap kits? Just the unassembled frames (Ikea style). The rest can be obtained from building stores.
My guess is that one panel will make no or just barely perceptible audible difference in the bass unless it is in the corner and you are physically less than three feet from it.

I think that two panels and you will just begin to hear improvements (barely).

I would say that four panels and you have a modest improvement in most rooms (worthwhile but not a total cure). I would think you need to be up around 8 panels to make a serious impact.

If you go membrane or resonators such as tubes rather than broadband absorbers then provided you know what you are doing then you can get the same benefit (at a specific frequency) for 1/4 the treatment. So two membrane panels tuned to your specific problem might be as effective as 8 broadband minitraps.

The disadvantage of "tuned resonators" is that they don't help as much outside their "tuned" range. So in my mind broadband bass trapping is the way to go if you can find an aesthetic solution that is acceptable.

This is all "rule of thumb" YMMV but in the case of acoustics size actually does matter.