Dave,

It occurred to me that the diagonal distance to that perforated plywood from the opposite floor corner is about (11^2+16^2)^.5 - which corresponds to about 60 hz. I think that section is likely encounter the fundamental or harmonics and I don't think there is enough room for lower frequencies to resonate.

(22^2+16^2+8^2)^.5 is the longest dimension in the room opposite corners ceiling to floor and the diagonal across the floor is (22^2+16^2)^.5 these might resonate ~40 - 41 hz. If these turn out to be an issue, I'm thinking I could have a 2" absorber that lays against the wall - mounted like a shutter so when it swings open it would encapsulate a prism shaped cavity in the corner(s) on one end of the room. I don't know if a partial (like half or quarter) wave can form resonances but it seems to me that that wouldn't tend to be too much of an issue. I'm not planning on doing anything yet - just thinking out loud before I get a mic & speaker in there.

I'm also aware that some of you guys have gone much deeper researching this stuff so chime in if I'm off the rails.

Been going steady, but have a couple of weeks of odds and ends like re-routing electric wires. I also have a couple of nice pieces of mahogany that I'm using to build a free standing mixing desk. In my other, sonically problematic room, I have my desk built against a wall. It is screwed into and partially supported by the wall. It is doubtful it is anywhere close to optimally placed - which is probably a big contributor to the sound issues. It has evolved to have a few cool features. It is kind of 3 sections:


[LIST=1]
[*]A central pc workstation.
[*]A not too large mixer cantilevered in space to the left.
[*]A compressor, a couple of tube preamps, and headphone amp racked to the right.
[/LIST]

The sections wrap around you slightly. I'd like to replicate and minimize it (channel-strip?) but also have to figure out how to make it really stable. I'm thinking free standing monitor stands - I'm curious if anyone has seen any issues with them - like falling over (there is some nearby foot traffic). I guess if I figure out where everything should be placed to sound best first, I could have the stands be mounted on something like flying buttresses that could double to secure the monitors and desk?

One of the real blunders I made was that I put loose cellulose insulation in the sloped regions by hand as I worked my way up (this is why I had kraft paper - to prevent dust leaking through the cracks). I thought it was a relatively small area, so what is the big deal? It turned out to be very time consuming. After working with the hemp batts (over the collar-ties) I realized how much faster it could have been. In retrospect, if installing cellulose again, I would have it professionally wet sprayed in where it is like papier-mache. Watched a video of this - talk about making a mess.

[quote="Dave Labrecque"]Hey--what's the T&G that you're using? Looks nice (pricey). I was thinking of using rough-sawn cedar or something similar to save a little money and get a little absorption/diffusion going on the surface.[/QUOTE]
It is white pine - so not too bad - with shellac. I have a thing for the older finishes. I wound up blending clear with amber. One of the cans is quite old with a bit of liner and rust falling from the sides, but I just poured it through a mesh. I think the wood was about $.40 / linear foot with about 4" coverage (it was actually less when I started the project). so not much over a dollar / sq foot. If I pay myself 4 cents an hour, it will be a cost effective project. The previous big projects was building an out building that is totally covered with solar panels and installing a geothermal system both with similar labor calculations. Now having made 160,000 kwh, I've passed the break-even point - not only that, my utility just jacked the rate enormously to $.25/kwh, and for now, I don't have to care (they're probably working on eliminating net-metering).

One thing to keep in mind is this job would have been banged out when I was 30. Now, not so much. I started on one of the side walls using nails and I noticed my accuracy had diminished (big secret). I realized it would be difficult to do all of that overhead nailing, and that the wood would have hammer marks all over, so I switched to finish screws for the remaining surfaces. Still I'd put up a few boards at a time and after all of the fitting, trimming, and screwing, have to rest a few days and invariably would get sidetracked for weeks at a time, so this has stretched into years. This is coming from someone who is not in bad condition, and also did a lot of overhead work (installing water softeners for several years jobs would frequently have hours of plumbing on the ceiling). I've always done things myself and don't particularly know how - or when to hire someone. In retrospect there is a lot of value in moving a project along. So just a few considerations to throw into the mix...

Hear is a calculator that you can have fun with:
[URL]http://www.acousticmodelling.com/mlink.php?n=4&nl=8&im=1&s11=4&k11=0.024&s12=2&d12=50&v12=10000&s13=1&d13=87&s14=2&d14=50&v14=10000&s15=1&d15=600&s21=4&k21=0.024&s22=2&d22=50&v22=10000&s23=1&d23=87&s24=2&d24=50&v24=10000&s25=1&d25=500&s31=4&k31=0.024&s32=2&d32=50&v32=10000&s33=1&d33=87&s34=2&d34=130&v34=6000&s35=1&d35=300&s41=4&k41=0.024&s42=2&d42=50&v42=10000&s43=1&d43=87&s44=2&d44=50&v44=10000&s45=1&d45=800[/URL]
I don't know how well it represents the real world, but it is something. My realization was that the volume over the collar ties could be put to use as an absorber. Attic side walls by the soffits would present the same possibility, if a deadened space is what you want to achieve..

Looking very cool. I really identify with this project. My attic studio project is similarly shaped but overall smaller (12/12 roof slopes on either side with collar ties at about nine feet). I'm figuring on a lot of guesswork and maybe a little novice-level experimentation in placing the bass trapping. I found a bunch of Rockwoool two-inch panels (that are heavier than what's typically used for this kind of thing) on Facebook Marketplace for a really good price. So that's my start.

Hey--what's the T&G that you're using? Looks nice (pricey). I was thinking of using rough-sawn cedar or something similar to save a little money and get a little absorption/diffusion going on the surface.

A little more detail. This is a profile template of the absorbers:

[url=https://drive.proton.me/urls/0JMYBP02BR#SFLQIZTCrwpH]absober_position.jpg[/URL] (currently can't post it inline)

...and a sketch:

[url=https://drive.proton.me/urls/Y3D39N61PC#RH1ar3YA2dd4]roof_diagram.jpg[/URL]

I would claim I'm trying to be scientific, but I haven't found numbers for absorbent properties for the hempwool materials to use in calculations. What I can tell you is both the wool and batts are rather absorbent. This could give you an idea:

[URL]https://www.hempitecture.com/plantpanelx/[/URL]

As the air cavity behind the panels increases, the impact tends to extend deeper into the low frequencies. Anyway, in light of the fact that a whole lot of guesswork contributed to the calculating, the panels are as much positioned to visually hide the kraft-paper in the gap as anything else. In any case, the shape of my roof is rather irregular as far as online calculators are concerned, so accurate absorbent numbers probably would not get me any closer.

If I had been thinking in these terms at the onset of this project, I may have had incorporated some other materials in the corners. There are some useful materials like metal sheets with micro-perforations that have interesting sonic properties.

I'm not really sure how to hang the boards. I'm currently leaning toward to gift-wrapping the hempwool in light-weight canvas and possibly put 2 rows of 5 buttons (on ~16" centers) each used to anchor an insulation wire that would stab through the hempboards, be trimmed to the appropriate length, then bent to a hook to hang from the edge ceiling boards.

[quote="Dave Labrecque"]Very cool. I have a similar build-out I'm hoping to get to soon. Will value your input. More when I'm near a keyboard.[/QUOTE]

Here is the ceiling. There will be 4 - 2" x 23" x 96" hempwool boards (think typical absorbers - but not made of fiberglass) suspended beneath the slots with the craft-paper and what is hidden above.

[ATTACH]3023[/ATTACH]

Behind my back is a room-wide closet with sliding mirror doors on a track. I'm thinking I can mount more hemp-wool board as the doors if needed. I'd have to make frames the boards are not quite rigid - but I have plenty - and lots of options.

Oh yeah, my wife wants me to take that outlet out and hang a chandler. That equals a nice piece of gear - but if I can get away with deploying monitors and a mixing station in the middle of the room, it will be an excellent tradeoff. I have the outletbox pretty secure so I can hang a chevy small-block with the light shooting out of the cylinders if I want to. She'll never agree to that - so there is - as they say, no accounting for taste...

Very cool. I have a similar build-out I'm hoping to get to soon. Will value your input. More when I'm near a keyboard.

I'm happy to hear that you're making progress again. Once you get it together, are you planning to do tests to check how different what you're listening to is from what is headed to disk in the mix?

It's been a bit quiet here - and here. So I figured a nice off-topic was in order...

I have been hard at work on construction in room that had gotten stalled behind a hundred other projects. This room has a bit of a cathedral ceiling with 6 on 12 slopes on the sides and a central flat section with collar ties about 11-1/2 feet high. A while back, I mentioned having trouble with pronounced resonant nodes in another room (which are partially under control because I have 2" thick hempwool boards scattered around that are intended for this room). Over the collar ties I have thick hempwool bats and plywood that was perforated with a cnc machine. Anyway there are some sonic experiments built in that I hope will work. Parts of the room were already done in tongue & groove, pine before I started to work this kind of thing in. But according to my calculations, much of the possible trouble areas may be addressed as the ceiling should absorb 20 to a few hundred hz pretty effectively. Of course there are other angles for nodes to develop but one of the things about doing a long job is that you get a chance to think possible issues and solutions (like get professional help).

This room first got torn apart because I was doing the roof with steel - but that ridge had a lot of sag (probably from whenever the conversion to cathedral style was done). I followed my engineer friend's suggestion to jack up an LVL under the original ridge.
at that time, I had done a lot of house projects, and reached burnout. Now 5 years later, a mixing room is finally within reach.

Anyway now that there is some momentum, I should be able to get a rig running in a couple of weeks. It already has a comfortable sound to it - and if nothing else, it is shaping up to look pretty cool - although it may be a tad on the weird side. Call it character.