Adding back some HF energy in my mix room.

[AuntieFa]

Hi!

I’m in the middle of treating my basement control room. It is intended to be a production room, that I can mix in as well as record vocals, and small acoustic instruments occasionally.

I’m in a relatively isolated area in Connecticut where I don’t really have to worry about disturbing anyone with my work.

The space itself is about half of an 18’x20’x8’ poured concrete semi underground basement. The builder has plywood covering 2 inches of insulation on the ceiling and three walls, the fourth wall is totally underground and has no plywood, just the bare concrete.

I have framed my half of the space inside the existing pyl and concrete. Then added insulation for absorption, which I plan to cover with fabric.

The rear wall has around 1’ of low density Johns Manville r-19 and a 1’ airgap. The rest of the space varies but the front end of the control room has 6” of r-19 with a 6” gap (including the front half of the ceiling), plus large corner “traps” which add another 1’ ish of r-19.

I’ve spent the last couple days moving everything around to mitigate speaker boundary issues. I think the bass response of the room is decent enough with my Event ASP8 speakers (though I’d like to add a sub and upgrade the speakers soon).

As you can see from the attached REW.mdat (looking at the TOPT) the HF energy in the room is below 100ms, but the low end slopes up toward 350ms.


My questions:

I’m thinking of adding slats over some of the absorption to bring some HF energy back. From around 200hz upwards I’d like to add 100ms. Will that be a good balance?

Where would be a good place for the slats? so I don't introduce new problems.

Based on the REW do you think I need more bass trapping?

Have I done anything else really dumb that I’m missing?

Thank you in advance for your help!

[gullfo]

generally speaking you can add a bunch of slats on the front wall and the sides - options including consistent patterns like John Sayers uses or Newell etc. or numeric based slat patterns like MLS or even varying the slat widths using QRD and inverse spacing for the gaps. it looks like a lot of the insulation is the light stuff. you might consider adding a layer of semi-rigid over that and cover with cloth. then add slats along the front wall, and "some" on the sides to see what response you get.

the LF - i'd add some of the semi-rigid on the back wall over the soft stuff to change of the impedance of the wall. and also consider that (given the size) may need some resonator, limp membrane, or other pressure traps to reduce the LF energy.

[AuntieFa]

Excellent, thanks Glenn.

What frequencies do you think it makes sense to target with the slotted panel to make it feel.... for lack of a better word... less weird when I'm talking in here?

[DanDan]

A friend Acoustician, Jeff Hedback, added some pegboard to Soffit style traps. Quite a change.

Kiwi Hardboard.jpg

[AuntieFa]

A friend Acoustician, Jeff Hedback, added some pegboard to Soffit style traps. Quite a change.

Thanks DanDan, having a hard time reading that graph. am I doing something wrong?

[DanDan]

I'll try a Screen Shot. Blue is Soffit Style Traps. Red is with pegboard added.

Kiwi Bigger.png

[DanDan]

Some Side/Rear Speakers and a Reverb?

[AuntieFa]

Thanks DanDan,

Am I reading the chart correctly? The pegboard is decreasing the LF absorption?

[gullfo]

yes, pegboard (and there are lots of types - # of holes / sq inch, thickness, materials, etc - although ones which are true "peg board" have a fairly standard spacing because you want to hang hooks and brackets into it) will have a resonator effect even on un-sealed absorption, although it's like Jeff's example (provided by Dan) was a proper resonator.
so the % of openings versus solid surface, spacing, and material depth are all possible to know via calculation. and you could even make your own "peg board" based on desired response and drilling holes to create that. and you could use multiple panels with different responses to broaden the overall unit response.

[AuntieFa]

Interesting. Thank you. So if I want to add a bit of liveness back in, presumably I could no impact the LF and only reflect some highs back. I suppose the next concern is choosing locations for the reflectors that don't interfere with the imaging too much or create other problems.

My thinking is to stay away from 1st reflection points, but is everything else kinda fair game?

[DanDan]

LOL, that Graph is proving troublesome. The Y axis is T60. So the red line, the one WITH pegboard, is absorbing a lot more LF.

[Paulus87]

LOL, that Graph is proving troublesome. The Y axis is T60. So the red line, the one WITH pegboard, is absorbing a lot more LF.

I have been seeing this graph and the kiwi audio peg board soffits for years now and it is so tempting to try... it is such an elegant solution, fibre (although I think he used foam instead) contained within a nice solid face which works better than without the face...

Was it standard pegboard that is used in tool shops to support hooks etc?

Shame pegboard is quite expensive and difficult to source in the UK

[gullfo]

LOL, that Graph is proving troublesome. The Y axis is T60. So the red line, the one WITH pegboard, is absorbing a lot more LF.

hmmmm it looks like the left-hand vertical scale has absorption coefficient numbers.... 0 - 1 - however if those are time T60 etc, then agree in this case the trap is definitely more effective at LF - did Jeff publish the design of the device?

[DanDan]

Y Axis is T60. I wonder if it was actual pegboard, or just hardboard without the holes. https://gearspace.com/board/photo-diari ... ost8992852