John Sayers' Recording Studio Design Forum Archive

Hey all,

I have a new room I'm mixing in and had to sort it in a hurry do to work demands, and now I'm sorting some issues.

The room is 20' 5"L x 10' 10.5"W. The ceiling over the mix position is a built-in cloud - 3" of 6lb mineral wool, then 1/2" drywall, then 3 1/2" fluffy before the subfloor. The drywall is 7'8" off the floor, and the back half of the room has a normal ceiling 7/4" up. The back wall is 3" of min wool floor to ceiling, with 4" min wool nested traps (24/16/8") in both corners, floor to ceiling. The front wall also has 4" min wool nested traps (36/24/fluffy) and the wall between is 4" min wool spaced 4" from the wall.

Speakers are currently at the corners of my Stirling Modular Plan A desk because when I Smaarted the room (I'm also a live engineer) that provided the best frequency response, unexpectedly. I tried them in several other locations but saw deep dips. They're sitting with acoustic centers at 50"H, which is also where my ears are, generally.

There is RFZ treatment at all the reflection points hung already (like I said, I needed to start working asap), with 2x4' 4" min wool panels spaced 1" off the wool at the first spots to the side, and then 2" panels from the Primacoustics London kit further back. A couple panels aren't up yet, and are just leaning in place.

I'm monitoring through Mackie HR824s, with the acoustic space at quarter (half and whole raised the low end in a weird way) and the crossover rolloff at 80hz. I have a KRK 10" powered sub making up the low end. It's crossed over higher than I'd think is right, but the Mackie rolloff is much higher than 80hz, and lowering it only added sub frequencies without bumping the rest of the low mids for some reason.

Main issues I'm thinking about right now are some of the dips in the low and low-mids and the low-mid response in general looks bumped between 150-250. I see some comb filtering in the highs, I'm pretty sure that's desk bounce. In the right speaker, also, the dip between 500-1k seems to be my laptop on the desk, which you can see in the pics. When I play with closing it the dip goes away, so I need to figure out a better place for it.

I'm including pics, a Sketchup diagram, and and mdat and would appreciate any and all feedback/advice on how to improve things! Thanks!

[PICS ARE MESSED UP, FOR SOME REASON ONE IS ON TWICE?]

https://www.dropbox.com/s/9c84qhx3qjvsr ... l.skp?dl=0
https://www.dropbox.com/s/x29uh1doeak39 ... .mdat?dl=0

Woo, nice decent sized space. I would have another go at Speaker and Listener Locations. Start with touching the Front Wall. Find the optimum listening location, optimise width also, recheck listing location.
Make sure the side reflections are absorbed, borrow some panels from the back if necessary. Ditto the cloud, I would add hanging panels over the mix location and speakers. Your width and height are similar so you will be in a double lowest null, and peaks. If you are hearing an echo behind you try block using some more panels on mic stands. Or polyester duvets hanging. Those Mackies are pretty decent speakers. You might be better running them full range and adding the sub.
You may have speaker controllers at hand..... Some parametric Eq might tighten the bottom need by nuking the lowest few modes.
With good cloud and side absorption, the path from tweet to ear will be free of early reflections and comb filtering. Very clear. Just like a PA I would roll off the HF.
The Bruel and Kjaer curve works really well for me. https://www.bksv.com/doc/17-197.pdf

Thanks DanDan.

There's a 3 1/2' difference between width and height, in acoustic world is that considered pretty similar? Not being snarky, just asking

Side reflections are absorbed as far as I can tell, the only reflections showing within 20db of the direct signal in the impulse response are within a millisecond. The entire ceiling from the front wall to 9.5' back is a cloud, but I could add more I guess. It's built into the ceiling, so I think in certain configurations I might be getting a reflection off the joist that's centered there (going across the room width-wise). No echo behind me, the whole back wall is 3" mineral wool and 24" nested corner bass traps.

Because of the large bass traps (36" wide and at a 25º angle) in the front corners and the front wall being 4" of mineral wool and a 4" gap, I can't but up to the front wall. If I back right up to the traps I'm about 16" from the wall and the SBIR dip is big. I had better luck pushing out into the room a bit, putting them about 3' out and 2.5 from the side wall.

For kicks, though, I put plywood against the corner traps and pushed the speaker up against them and it did make a big difference. There was still several 6db dips, fairly narrow, in the 200-700hz range, but above that was solid. I might be able to soffit-mount the speakers in the traps, I left off covering them till the room was right. There's just black landscaping plastic over them now.

Sorry I misread your dimensions. What is the Height?
Generally many of us say 4" fibre+ 4" airgap equivalent to say 6-7 inches of fibre, minimum. 3"inches will prevent flutter, and diminish the HF aspect of room decay.

Great re the side reflections but keep an eye on with speaker position and listener position changes.... 20 is a minimum, mostly I see 25-30.
I guess your very early reflections are the desk, so speaker stands, angle the work surface if you can.

Interesting that your Speakers show strong FWBIR when you place them in front of these presumably deep Corner Traps.
Given your opportunity with temporary covering I would definitely try Soft Soffit, sink them in there.
I have had good success with that.

Maybe I’m wrong and it’s not SBIR? Definitely saw a big difference when I put plywood in front of the traps with speakers against it. I included my .mdat in the OP, maybe I’m misreading, still learning the nuances of all this!

The bass traps themselves are nested, not full super chunks.

I noticed (in REW and SMAART) a difference in SBIR response when I put plywood over the bass trap with the speaker backed up to it, with it being better than just having the speaker pushed up to the trap. Can I cover part of the trap and it still be effective as a bass trap?

thedavidlim wrote:I noticed (in REW and SMAART) a difference in SBIR response when I put plywood over the bass trap with the speaker backed up to it, with it being better than just having the speaker pushed up to the trap. Can I cover part of the trap and it still be effective as a bass trap?

Yes, you could do. A lot of the low frequencies which are not reflected or absorbed by the plywood will creep round the plywood and then get into the fiber.

Paul

I’d thought about venting the bottom like John does his soffits.