Room voodoo

[jmh]

It still has parallel walls, just the 2 outer thirds of the ceiling are sloped (with the central third level like the floor). I think the room was originally constructed as an open garage - then whoever finished it, built it out so the paired 2x12 beams that support the eaves, and the posts that support it, are about a foot inside the room. Apparently, he wanted it bigger than the natural layout, and the eaves projected enough to accommodate that. I also put in a funny shelf that spans the room in the 20' between the 2x12s on one end of the room kind of diagonal top about ~8' up and 3' deep on one end and 7' on the other.

[John Ludlow]

Well... I can't imagine it from your description. But I'm sure that you will be able to at least improve it, and I'm interested in the results of your tests.

[cgrafx]

It still has parallel walls, just the 2 outer thirds of the ceiling are sloped (with the central third level like the floor). I think the room was originally constructed as an open garage - then whoever finished it, built it out so the paired 2x12 beams that support the eaves, and the posts that support it, are about a foot inside the room. Apparently, he wanted it bigger than the natural layout, and the eaves projected enough to accommodate that. I also put in a funny shelf that spans the room in the 20' between the 2x12s on one end of the room kind of diagonal top about ~8' up and 3' deep on one end and 7' on the other.

Could you post a picture of the room?

looking at the sweep you posted there is clearly a big resonant boost, but how best to fix that will depend a lot on the design of the room.

[jmh]

Could you post a picture of the room?

This will be in the subdirectory RoomPhotos_1

https://drive.proton.me/urls/FFHF8N2NS8#kxQA8AsTNN3F


If I knew I was showing the place I would have cleaned - which I have to do as the futon couch doubles as a spare bed and I have someone coming next weekend. The next room has a construction project so it is that much worse. We can just refer to all the crap as the current acoustic treatment. Enough excuses...

The 2 Room photos are fisheyed on the phone which makes it look bigger than it is. The length (along roof ridge) is 24' 4-1/2". The width is 21' 11". Height to flat top is 11' 10".

What I was referring to as paired beams are actually tripled (although the 'original' blue ones, behind the drummer, are doubled).

On the 'TowardWest photo, the shelf is about 3' deep on the left and 7 on the right. A mix of empty gear boxes, water conditioning equipment, and camping gear. The room sound improved dramatically when that was put in, so despite my current issue - it could be worse. It would be easy to transform the shelf into a bass-trap of sorts. I have to figure out if it is in a worthwhile location. I'm probably going to get a couple of movable traps to start - maybe I should hang them up under the shelf between the beams before they find a home to see if that location has a positive impact.

The TowardEast is kind of fuzzy. The microphone in the foreground of the wooden file cabinet is the ribbon (in a plastic bag) approximately where the response waveform was captured with the edge toward the hard-panned left speaker that the sin-sweep was played on.

The last photo is the desk which started in a tiny room in another house. It is obvious to me that it is not in the perfect location - but a free-stander is another construction project.

BTW the last several sessions with a drummer have been coming out pretty nice (although on one we forgot to take off the plastic bags on the room mics. They were still okay - but a little less clarity then should have been).

[MMP]

There are a number of things about your room I would address if I was recording there.

First off and most important for the bass resonances, I would triangulate the four corners of the room with 4 inch thick panels of Owenings Corning 703 top to bottom, with the space behind them as deep as you can bear.

The ledges formed by the columns on both sides of the room I would try to fill completely with some kind of absorption, maybe rock wool.

I think the skylights are problematic audio resonators, but probably higher in pitch than your main issue.

The shelf and bookcase on the wall opposite the mix position seem like they would act as diffusers, so I would not be too concerned about them.

I would try moving your monitors further from the wall behind them, and if possible closer to the center of the wall.

The asymmetry of the ceiling is probably more an issue for mixing than tracking, but creating an absorbent suspended cloud of panels above the mix position would help.

The paralllel walls are probably more an issue for higher frequencies, but anything you could do to soften at least one side would help the room sound.

[John Ludlow]

I second the suggestion to center the monitors and move them away from the wall by several feet (particularly since those Gauss 7s are back ported). You'll hate routinely looking at the wasted space, you'll have to arrange some other method of propping them up (stands that do not acoustically couple with the wall or floor?) and you'll (very reasonably...) perpetually live in fear that someone will tip one over (->studio rules<-for visitors (I know whereof I speak...)). But it will improve your situation sonically. You might be surprised how much better they sound. I'm not sure what the difference between a wall behind the right monitor, and a glass window, will be. It's probably not a good difference though - which is probably why you did it the way you did. You might have to sacrifice the window by covering it with absorbent, which would mean you'd probably have to soften the wall on the other side to balance. You'll hate the loss of natural light, but it will help you make good mixing decisions. It's possible that that glass difference could be accounted for by software - like the one I previously mentioned - for your mixing position. You could try that.

But fix the bass first.

[cgrafx]

I don't think I'd be overly concerned about the skylights, there are bigger issues at play.

The symmetrically pitched roof is definitely an area of concern, and as others have suggested doing sound clouds in the center will help to address that issue.

The upper storage area with the camping gear should be treated.

Get some heavy sound blankets (https://www.uscargocontrol.com/produ...ound-blanket_2), and hang them from the ceiling at the leading edge of the storage space (or even a little in front) so they cover the entire face of the storage space. If you hang two offset by a few inches it will increase the effectiveness of the bass trap.

[John Ludlow]

Philip - If that is effective for absorbing really low notes, at ~$35 - that's an incredible deal. I have no experience with them. But I would have presumed that a 100 Hz wave would go right through that, bounce off the wall on the other side, and come through it again. Have you run tests on them? Because if you know this works for low bass, I'll have to get some myself!

[cgrafx]

Philip - If that is effective for absorbing really low notes, at ~$35 - that's an incredible deal. I have no experience with them. But I would have presumed that a 100 Hz wave would go right through that, bounce off the wall on the other side, and come through it again. Have you run tests on them? Because if you know this works for low bass, I'll have to get some myself!

it’s not sound proofing, but the buffered cavity significantly reduces the standing wave. a single blanket with the open space behind creates the initial baffle, adding a second offset blanket, creates a second baffle between the layers.

I did this in one of our video studios using carpet pad offset hung from the wall,so there is a gap between the pad and the wall.

in your case all the camping gear should add to the deadening effect.

[John Ludlow]

Right, right... the air gap. I had forgotten about that.

I remember the description of a DIY bass trap that took advantage of air gaps. It had 4" of out-facing 703, then an air gap, then an elastic membrane of some sort that hermetically separated the 703 side from the wall side. Then another air gap - and then the wall.

So, whatever signal made it through 4" of 703 had to excite air in the first gap, then the signal in that air had to vibrate the membrane, which had to move the air on the other side of the membrane to get to the wall. Then, that pressure wave had to go through all of that in reverse in order to get back into the room. The air gaps were the most important parts because neither the 703 nor the membrane mechanically couple with the air in the gaps very well - and the signal has to change environments repeatedly with energy (gain...) being mechanically used up as heat in the transitions.

It probably would have been even better if, instead of gluing the 2" 703 sheets together, he put dowels, or something supportive, between the layers of fiberglass to create another air gap.