Room voodoo

[jmh]

it***8217;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.

I was thinking of using wool rugs for this. I wonder if a cloud of flying carpets could work. Also, a well chosen rug - which my wife would insist she do, could make that shelf area look pretty good.

John,
Those monitors with the back ports were an unfortunate purchase during the pandemic. My regular Alto music that had decent pricing and I could walk in, and check stuff out was being transformed into an online giant. Now they just do list pricing and the can care less about walk in customers. Prior to them, I had KRK passive monitors with a front port - but the silk cylinders that the tweeter voicecoils were on turned to dust and the replacements I had to settle on didn't work out...

Hopefully this can serve as incentive to get the neighboring room done, and I can clean this one up and get something deployed. I'm trying to digest all of these suggestions and devise a best path forward.

[cgrafx]

I was thinking of using wool rugs for this. I wonder if a cloud of flying carpets could work. Also, a well chosen rug - which my wife would insist she do, could make that shelf area look pretty good.

Wool rugs could work, anything heavy and dense. The more mass it has the better. Flying carpets could also be used for the cloud.

I think I might try building a wood frame on the back of 4x8 sheets of peg board (or cut to size), mount your rug to the front and then hang that asymmetrically offset from the ceiling (meaning looking longways down the room it should be hung closer on the side further from the center, so it creates a wedge shape behind the panel). Do the same thing on the other side of the ceiling but hang at a different angle. You could actually attache rugs to both sides of the peg board which would dampen reflections between the sound panel and the ceiling.

The only downside to the cloth materials including the cargo blankets is they are not fire rated (unless you can find some fire treated/rated wool rugs).

[jmh]

Wool rugs could work, anything heavy and dense. The more mass it has the better. Flying carpets could also be used for the cloud.

I think I might try building a wood frame on the back of 4x8 sheets of peg board (or cut to size), mount your rug to the front and then hang that asymmetrically offset from the ceiling (meaning looking longways down the room it should be hung closer on the side further from the center, so it creates a wedge shape behind the panel). Do the same thing on the other side of the ceiling but hang at a different angle. You could actually attache rugs to both sides of the peg board which would dampen reflections between the sound panel and the ceiling.

The only downside to the cloth materials including the cargo blankets is they are not fire rated (unless you can find some fire treated/rated wool rugs).

I was kind of curious about firerating after I saw a certificate for treatment on some soundproofing in the school I work at. I don't know, but suspect they may have used PASFs in the last couple of decades - I think I'd prefer a nice wool fire - and also suspect this is much more resistant to burning then many synthetics.

You probably saw the woodstove - and you do need to consider these things when that is in use.

[Dave Labrecque]

Helmholtz resonator(s)?

[John Ludlow]

One final thought regarding the goal of 'fixing the room'. For mixing, you want as flat a space as you can get in order to make good decisions. But for tracking you don't usually want a 'dead' space. It will sound dull and lifeless in the result. Rather, you want a space that 'sounds good' to be in. Of course, the sort of imperfection that you have shown us is waaaay too much of one variation. But you want it to be a little lively. So, don't go too crazy with absorbers.

[Dave Labrecque]

One final thought regarding the goal of 'fixing the room'. For mixing, you want as flat a space as you can get in order to make good decisions. But for tracking you don't usually want a 'dead' space. It will sound dull and lifeless in the result. Rather, you want a space that 'sounds good' to be in. Of course, the sort of imperfection that you have shown us is waaaay too much of one variation. But you want it to be a little lively. So, don't go too crazy with absorbers.

Maybe I'm misunderstanding you, John, but liveness of a room (reflections/reverberation) and room modes (or other resonances) are two different things. While some of the former maybe desirable, I don't think any of the latter ever is. Certainly not for a mixing space, anyway.

[jmh]

Maybe I'm misunderstanding you, John, but liveness of a room (reflections/reverberation) and room modes (or other resonances) are two different things. While some of the former maybe desirable, I don't think any of the latter ever is. Certainly not for a mixing space, anyway.

I think what John is saying is your effort to control your room's response is likely to extend beyond the frequencies you are targeting.

Any space is going to impart a unique character on sound, and I guess mine isn't (yet) ideal for mixing. I think room modes are a consequence of having a room - from my reading, bass traps are a way to tame some of them.

________________________________

I did some *experimentation: stepping through frequencies at low volume yielded less responsive resonances (the peak response was proportionally not that much higher) than when rerunning it at a higher volume. Could the relative level of chaotic noise floor noise attenuate the resonant response?

I wandered around like a bullfighter with a heavy wool blanket with 102hz playing. Certain locations did seem to impact it - although it may have been the wool's proximity to my ear muffling the immediate space.

* This is preliminary and I wasn't testing for this per-say, so I wouldn't base any statements on this.

[Cary B. Cornett]

... I would have thought you'd have an advantage in non-parallel walls.

Non-parallel walls can have acoustical advantages, such as avoiding flutter echoes. However, the do NOT eliminate room modes (resonances), although they do make the mode frequencies more difficult to calculate or predict.

[Cary B. Cornett]

Helmholtz resonator(s)?

Those turn out to be very ticklish to apply correctly, and are definitely NOT recommended as DIY projects.

[Cary B. Cornett]

I'm going to make a few general comments here.

A friend of mine is a professional studio designer, and I found myself helping moderate one of the Facebook groups he runs. I have learned a few things from him and from some forum discussions.

The first caution is, DIY studio construction and design are great ways to waste a lot of money while not quite getting the results you are after. If you have the budget, the best starting point is to find and contract a professional designer (no, I am not one of those, just a guy who has learned a few things, some of them the hard way). The thing is to find someone trustworthy. There is a LOT of really bad information out there, put out by people who are NOT qualified professionals.

The hardest thing to control in a room is bass response. First, it is affected by the size and dimensional ratios of a room, and getting those right makes the rest of the process of getting control of the bass easier. There are some good calculators available out there (often set up as spreadsheets) that can help with choosing room dimensions, or at least finding out how much trouble you are in with the room you have. The purpose of these is to help you put the room boundaries where the room modes (resonances) are distributed in a favorable way.

Once the room is constructed, or after you are stuck with a room and have to make the best of it, you start adding acoustical treatments. Again, the low frequencies are the hardest to treat, not least because, for a given sound pressure level, there is a LOT more energy in the low frequencies. The main way to "tame" resonances is to absorb energy. Make the room lossy enough, and the resonances will not be as strong. Bass traps, properly made and placed, and the most common (good) answer for this. You need a lot of these, and not just in corners. If you need to make your own, limp bag absorbers are the easiest, and don't have to be specially calculated. These have to go directly against the hard boundaries (walls), because they work on pressure, not velocity. The pressure zone is right at the hard surface.

For mid and high frequencies, you buy or build broadband absorbers. These work on velocity instead of pressure. The deeper (thicker) these are, the better, up to about ten inches or so. Try to go for at least 6 inches. Fiberglass or rockwool, either of these at Low Density, is best for this application, covered first with a thin layer (quarter inch) of poly quilt batting (both to contain fibers and as part of the absorption), then covered by burlap or similar strong acoustically transparent fabric. Both wall absorbers and ceiling clouds work well made this way. Making absorbers too thin is a great way to make a room sound "tubby". This is all about wavelength, and you want your absorber to be at least a quarter wave thick for the lowest frequency of maximum absorption.

It is best not to put broadband absorbers in front of bass traps, because the former will then make the latter less effective.

Hanging a rug, moving blanket or whatever is not going to do much for low frequency problems. You may hear people touting Mass Loaded Vinyl. This is much oversold, and much of the advice on how to use it is wrong. It has limited use, and is best applied by professionals, which is why I myself won't mess with MLV.

For people who want to do some preliminary study at a trustworthy source, I often recommend going to the resource page at jhbrandt.net