Helmholzt question

I am following an article in pro tools expert.

I have a fair bit of broad band up already and 2 super chunks in corners but I still have those problem areas.

I kind of gave up dealing with room acoustics, sold my expensive monitors and almost always use headphones. for tracking I built large gobos and mostly close mike.

But I have a large broadband up in my back wall that could be easily expanded to be one a HH. I am curious is i did it how much more flat the lower end would be one if at all?

So reading through your list of problem freq ranges, I'd focus on the first two: 70-100hz and 110-120hz. Those frequencies are critical. 400hz, imho isn't. Imho, there's just not much critical information at 400 hz. And everything from 1k up is better treated with broadband absorption.

Can you build more superchunks in any other corners? Or make soffit traps for the wall-ceiling corners? That would be where I'd start. Then, I'd maybe think of a tuned membrane trap like GIK's www.gikacoustics.com/product/gik-acoustics-scopus-tuned-bass-trap-t70/

Tuned traps like that are pretty expensive.

So 4” rockwool isn’t going to do much at 120hz and below. It took bass traps 12” deep to make a dent in the low end of my room. But when you make traps that deep you’ll need to face them frk, wood slats, it something to reflect the mud range and highs back in the room.

Thx. I have 2 corner bass traps, super chunk behind my monitors.

I could put 3rd in one back corner but not the other as there is a door there that needs to open.

Yes, that is why I want to build out the back 4 inch absorber out to a 12 inch tuned HH. It would be easy to build out the box/ frame and to seal it and install wooden slats for the desired freq.

I have an interactive calculator tool which I have used to establish frame depth and slot width and slat width and depth.

Thx for the detail, have done pretty well all of that ,except soffit mounted absorbers

The room does not have good dimensions, which is the fundamental problem.

I’ll review all this and consider my options:) I have a compressor to build first!

I would use tuned treatments (like Helmholtz Resonators) as a last resort for bad narrow band issues - as others have noted, they are notoriously difficult to tune and place.

Unfortunately, low frequency issues in small and medium sized rooms are best dealt with architecturally - move walls and/or ceiling or move the sources and pick-ups around the space to avoid the issues as best you can - which is mostly not an option. When you are dealing with a space that can't be altered dimensionally (or if you don't want to sacrifice already limited space) your best bet is to treat the corners because that will have the most impact on the room modes that dominate the low end response of the room. Tri-corners (where two walls and the floor or ceiling meet) will have the most effect on the strongest (axial) modes and treating bi-corners (wall meeting wall, ceiling or floor) will affect the next strongest (tangential) modes.

You already have two room corners (including the front 4 tri-corners, if your treatments are floor to ceiling) treated - I'd treat as much of the remaining room corners as possible. If you cannot do the entire corner with the door, there may still be some value in doing the tri-corner above it (especially if an axial mode is contributing to your issues). You can also consider treating the corners where the walls and ceiling meet to knock down tangential modes a bit. In my rooms, I treated the corners first and then added absorption and diffusion on the walls to treat higher frequency reflections - broadband absorption in the corners already knocks the highs down, so I have more diffusion than absorption on my walls. I also have some treatments that are faced with wood slats (as another poster mentioned) to avoid knocking the highs out too much.

If you want to be smart about which corners will give you the best return on effort (and your room is roughly a parallelogram floor plan with a parallel floor and ceiling), calculating the expected modes and kind of eyeballing them against measurements can help to identify which dimensions are associated with troublesome modal issues. But this can be hit and miss - the simple mode calculation uses an extremely simplified model that ignores a bunch of real world effects, so the actual modes are often only vaguely close to the predictions. And if your room is not roughly rectangular you need a much more complex set of calculations before you can even make predictions.

My $0.02 (Canadian)
John

I’m about to contradict everything I have said for years, but after fixing a home theater that was truly screwed up with absolutely no budget, I have to say try a little DSP EQ. It really can be a simple lowend fix.

You may already know this, but when building deep bass traps (12” or more) the medium/light density insulation actually works better than the high density rigid insulation used for broadband panels. The high density stuff resists airflow too much once you get to a certain depth. Roxul Safe n Sound works great for these applications and is sometimes carried at local hardware stores. I was able to get mine from Lowes.

Thx, my bad, yes, the m 3 exterior walls are likely concrete block, 2x4 framing inside for insulation.

Since we are talking remedies, anybody in the Chi town area might want to check out this gs add:

www.gearslutz.com/board/gearslutz-secondhand-gear-classifieds/1292780-gik-acoustics-bass-traps-amp-244-panels.html

I see..
I believe (sight unseen of course.. so maybe not, but I believe so):
1. Remove the drywall ceiling, insulate open joist area then fabric and slat cover that.
2. Corner trap every corner.
3. Use panel diffusion on walls and some mid / high mid (foam - (ugh - I hate foam. Maybe hanging tapestries) absorption where opposite wall has some sort of diffusion panel in the exact opposite spot / wall (if walls are parallel).

Upside.. Room will probably sound great like this. I LOVE a totally dead / trapped ceiling.
It basically kills all standing wave problems. As long as the ceiling above the insulation is not concrete.
You won't lose any room height with ceiling treatment.

Downside.. you won't want a lot (any) carpet on the floor or it will sound dead (muffled) as hell with a trapped ceiling. This can be hard on the feet. You can also leave some of the ceiling not trapped and have carpet under those certain spots. Maybe at a piano spot or singing spot. You would still need a lil' absorption over these spots though for upper mid slap echoes.