Helmholtz Resonator 42HZ ROOM MODE

Well, afaik your SPL is already good.

I suppose your 42Hz bump is your length dimension.

Being that your speakers are right up against the wall, it's unsurprising you have a bump there.

Is that your subwoofer on the ground? You can try to move it into a null to "integrate" your bass response with your speakers; depends how low those go.

Basically I think SPL is more related to positioning than to treatment. In other words, try to move your speakers or LP a little before building anything.

A resonator is a slow-response unit, from what I understand; it won't help your initial SPL.

I'd be happy with the SPL you're getting.

This is just my current understanding.

-m

You can also see the RT60 waterfall here
ibb.co/fXfkFv

Thank's
Giving you a tip 😜
In corners I built 4 (40cmx40cmx120cm) plywood frame, like an open closet and inserted 7 pieces of mineral wool
I used variable 4 densities (60kg/m3-120kg/m3).
In addition to that, I covered those with light thin pvc behind( work also to high frequencies)

Most of my acoustics on wheels or portable so it's easy to move in the room

That's my "secret weapon"
An 35cmx35cm mineral wool
😉

All I can add is that, since it may be your rear wall, you can do 8" thick mineral wool panel gapped 4x off your rear wall to target that frequency. Actually, a 10" absorber 4x would be closer to ideal. Really, about 3' of absorption is probably the best answer but who's going to do that?

In any case, it's not unrealistic to target that frequency with absorption.

In metric we're talking a 20cm thick mineral wool with 80cm gap.

I mean, you're already using 40cm thick in your corners, right? Isn't that 16"? If that's true then this thickness should be a breeze for you. It's just whether or not that air gap is tenable in your space.

So ya. idk anything about anything except just a little about absorption. But, realistically, unless I could manage the kind of treatment I'm suggesting, at this point in my life, I would just live with the slight out-of-specness of your 42Hz ringing. Ultimately, it's your room and you can decide what's best.

If you're really interested in acoustics then it might be a fun project to try out. I'll just say, usually when I test things out on my own it only confirms the common knowledge propagated by Ethan, rock and anyone else with experience. The only thing I've found contrary is that I read he said putting super chunks flush in the corners is best. In my room, I found a little benefit to gapping them as you would any other absorber.

But ya, he never recommends anything but broadband and maybe diffusion once your ringing is set; at least for small rooms.

-m