CR Treatment and Tuning---The home stretch!!

What is your reasoning behind embedding the CR glass so far into the front wall? To maintain a certain resonant frequency within that cavity?

Mostly room volume. Recommended minimum volume for a critical listening room is 1400 cubic feet. Frank's room is 1380 cubic feet, which is fine but on the edge. If I would have brought the window in to line up with the soffit faces, I would have lost another 60 ft3 or so, which I did not want to do. That's over 4% of the room volume. For small rooms, interior volume generally takes priority over modal issues. Also, having the window in a different plane does help a little with both modal issues and SBIR, to a certain extent. In a small room with an unusual layout ("corner control room"), I'll take every bit of help I can get! I used a lot of "tricks" to maximize the volume and acoustics of this room. Originally Frank wanted the largest possible size for his live room, with the control room as second priority, so I designed the entire studio like that (even the bathroom has a strange trapezoidal shape to eak out a few more square feet from the LR). But I didn't want to compromise too much on the CR, so I kept it as big as possible, within the limitations. I tried not to waste even a single cubic foot! There's one more reason here too: by pushing the window deeper, Frank gets slightly better sight lines into the LR, since the window frame is a little wider, as it is not restricted by the soffit faces. In the years since I originally designed Franks room I have come up with an even better method for improving sight lines (sorry Frank! I only thought of it after I designed your place), but I'd prefer to keep that to myself for now... :)

I will have about a 2' 8" gap between my windows if I mount the CR side window almost flush with the soffit walls.

That's a pretty large gap, which tells me that you are probably wasting space there. It's great for very good isolation down to low frequencies, of course, but that only really matters if the rest of the wall has the same gap and mass.

Also, assuming your slotted poly is sealed (HH style), typing in the 3/4" x 4.5" slat dimensions with even a 10" depth,

It sticks out 9" from the stud faces, but these are inside-out walls, so there's actually 13.5" of depth.

When you say that it is effective down to 50 Hz, is that because you will lightly dampen it like you did with the rear treatment device and lower the Q of it?

Exactly. The coefficient of absorption will still be above 0.5 at 50 Hz, which is usable. Here's the predicted tuning for the two most critical elements:

It seems near impossible to find out much information online like this, so I'm sure I can speak on behalf of everyone when I say thanks for sharing your awesome amounts of knowledge!

Yep! Many designers don't like sharing too many secrets (me included!), but tuning a slot wall isn't that much of a secret. The problem isn't in the prediction equations so much as in the practical implementation. That's where the important information is lacking in many of the DIY explanations and YouTube videos.... and curiously, those videos and websites don't seem to show actual acoustic test results from the advice they give! I wonder why? 8) :lol: Unlike John's forum, where we really do want to help. - Stuart -

I'd love to see your desk idea. I'm not going with a full blown console, I'll be mixing in the DAW. I will need desk space for a controller. Ultimately, I don't see the point in coloring a signal path with a console unless its high end and I don't see the need really. I like your desk description.

It's the Sterling E series desk that I'm thinking of as the concept. Here's the actual desk inserted in your room: It's a little large (front to back) for your room, but I was thinking of taking that same concept and re-working it to fit better, in something you can build yourself (buying that thing new costs a fortune: quite a bit more than your speeding fine! :) ) Let me know if you like it, and I can add that to the "to do" list, for future stuff. I'm also going to modify the soffits a bit more, to improve the angles and dimensions for your new speakers. More on that later... (another "to do" item....) - Stuart -

Maybe the soffit would break up the wall features in a helpful way visually speaking... What's your take on how the soffits benefit us acoustically? I still need to picture what all this will look like with the cloud too..could be kinda busy

I'll do a rough mock-up when I have a chance. I'm on vacation this week and next, and also working on another urgent project that has been delayed too much.... I'd like to get you the curve ASAP, so you can at least start cutting out the spacers and buying materials.... stay tuned....

The outlets are set to be about 18" from the floor, center of each wall...can't imagine that's going to mess things up too much since that's well below the ear...but who knows?

Pity they have to go on the side walls.... Putting them on the rear would have been a piece of cake. But no problem: I'll fit them in for you. - Stuart -

Yeah, I definitely want to build my own desk. Furniture is insanely expensive!!! That desk is $4000 US at Sweetwater! I could never :ahh: ..Too many other things worth saving up for, like the gear to go in the desk :mrgreen: I new I was going to do some sort of desk rack space..Interested to see how much space I can pull off. Just wanted to see if you had some crazy option I hadn't thought of. I will be doing modular 500 series type stuff for sure..If I actually make money at this then I'll look at higher end converters like Dangerous or Burl, but the cart is way in front of the horse there. Sooo, put that on the list.. :thu:

Soundman2020 wrote:

I'm on vacation this week and next, and also working on another urgent project that has been delayed too much.... I'd like to get you the curve ASAP, so you can at least start cutting out the spacers and buying materials.... stay tuned....

Are we set back quite a bit on time? I know you have other stuff going on in March. Not freaking out...just a bit of a surprise....If possible, I'd like to get a general time frame for getting to the point physical room treatment completion. Walls, soffits, cloud...Everything up to digital. Naturally I want to get done as soon as possible after 3.5 years, but I also want to be reasonable and realistic. I'm ready to work day and night on my end, so it really just depends on what your able to do...

Furniture is insanely expensive!!! That desk is $4000 US at Sweetwater! I could never

Yup... I did mention it was a bit more than a speeding fine! (Unless you are doing 500 MPH in a school zone, maybe.... ) I just remembered that I did a "reduced size" version of that concept for a customer in New York a couple of years back, so I inserted that in your model as well, to give you an idea of what I have in mind. Here's a direct comparison of the full-size original desk, as per the manufacturers specs, and my reduced size version: The full size version has 24 rack spaces (12 per side), mine has 14 (7 per side), but it would be possible to put more in the legs, if necessary. However, 14 RU is probably more than you'd need, unless you really want to go overboard with gear... - Stuart -

I don't mean to include the desk in my previous question for a time frame of course! I see that as a 2 week project all by itself on my end.

I don't mean to include the desk in my previous question for a time frame of course! I see that as a 2 week project all by itself on my end.

Right! At least! But the desk size/position does have an influence on the modifications to the soffits... :) - Stuart -

Of course, but the soffits will have to be finished before a desk goes in... :) You can use the dimensions of your modded desk for the soffit. I would only do small tweaks if anything. I definitely want to as close to window as is allowable for the sake of space..

use the dimensions of your modded desk for the soffit. 

:thu: - Stuart -

Final (hopefully) entire real wall. Ceiling soffits added above 8' slotted polys, hump reduced to 7 1/4" inches, my small mastering desk, electric outlets on rear wall (my recommended location next to couch, and also the location you mentioned, in the middle of the wall aprox.): Details of soffit box and spacers: Spacer shape, high res, with dimensions: (Click on each of the above three for the full high-res image) It's far easier to do the slat spacing in millimeters, as it works out to whole numbers. In Imperial, you'd have to be figuring things in 1/64 and 1/128 to make it work! I'm sure you have a metric tape measure? SLATS: All slats are 4 1/2" wide, 3/4" thick, and routed to put a 1/2" round edge on both sides. SPACERS: Make seven spacers for each side, and set them 16" OC, starting with the first one flat on the floor. The soffit sits directly on top of the top spacer, and runs 15" up to the ceiling. The spacers must be sealed to the rear of the stud bays! Not shown in the above diagram. These are tuned devices, so they do need to be sealed. Probably the easiest is to add extra framing members at the right locations, between the studs, so you get a flat front surface, (pull the insulation first...), and caulk it all up nice and tight, to the studs and the sheathing. (Then put the insulation back into the bays....) INSULATION: You will need 1" of medium density fiberglass insulation directly behind the slats, just like you did with the "monster" devices in the rear corner. Held in place with chicken wire, beads of glue, or whatever you feel like. It needs to be more dense this time: OC-703 would be good, or even OC-705 if you can get it. But 1" thickness is what we need here. No thicker than that. Pink fluffy is too light. SOFFIT: Wood dimensions not critical, but I did make them the same size as the slats on the rear wall (updated!!!! please note!), to match visually. No need to seal the soffit: it's just pure porous absorption bass trapping. Fill the soffit completely with insulation: whatever you have on hand. Not critical what you put in there: it can be a mix of any scrap insulation pieces you happen to have, or pink fluffy, or mineral wool, or fiberglass... anything is fine. But do put 1 mil plastic across the front before you put the fabric on. REW TESTS: Do regular REW tests as you are putting up the slats, if you can. There's 15 slats on each side, so maybe do them in groups of 3 then a REW test, so we have lots of data to see how things are going. Or groups of 5 if you get bored doing so many tests.... That should keep you busy for a few hours! :) - Stuart -

Yeah shouldn't take more than a few hours to get this done, I'll have a test back to you this evening... :lol: Or more realistically sometime next week... well played..

How critical is the curve accuracy? I have enough information for the high point but there is no contour dimension info. Might be easiest to get me the .skp..Not sure how I'm going to lay out that curve yet. Hmmm..... I might be able to get a print shop to print it onto something I can then trace to boards. Also, be aware that the 1" duct liner will be out of the equation with this new scheme as I will be chucking the existing wall panels housing it. Too bad I can't use it over the 703...shame to throw it away :( . Occupational hazard in this case. perhaps I'll throw it into the soffit.

I realized that the dimensioned view probably wasn't too clear, so I did another one: I also decided to divide the device into three sections, in the middle of the 6th and 12th slat (which should line up next to your studs), and I think it might be easier to just make the spacers deeper, to go all the way to the back of the insulation bays, like this (except for the top and bottom spacers, and also note that the top spacer is doubled): Slot the spacers to fit around the studs. Then the 1" thick insulation would fit in the front of the bays, up against the rear faces of the slats: Hope that clarifies things! - Stuart -

(That looks like the same screenshot)Unfortunately, I have no bearing on the curve itself..Its free hand for me at this point. I have no way to lay that out with any accuracy cause I'm not a CNC :) and even a CNC would need a data file to draw it. OK, I'll slot the studs. Did I make you mad??? ouch! :shock: I do see that some of the slats won't have very adequate backing if the ribs aren't deeper. Also, I need to know where those dividers go. I need dimensions. My studs do not line up with the model. (Actually I can just look at the model on that one and reference the studs) And, does the insulation need to be up against the slats? Not sure how I'm going to do that.....and have it stay in shape. Not too concerned about this yet cause there is other stuff to deal with.

Check your e-mail: I sent you some SKP files, with all you need, and some instructions.... You can get all the dimensions from the SKP. - Stuart -

Thanks man!! :yahoo:

Looks like I just need to convert the curve to a pdf file then the print shop can print it out for me....We'll see how I do.. Congratulations! It looks like I'm out of your hair for awhile!! :shot: :mrgreen:

Looks like I'm going to have to install the floor first as a result of the curve. I wouldn't be able to do the snap together tongue and groove otherwise....Just letting you know. That should ad a day.

In the interest of saving on material, I just wanted to check that I couldn't use the 1" duct liner instead of 703. Hate to waste it ...Can you think of anywhere else to use it if not?

I just wanted to check that I couldn't use the 1" duct liner instead of 703. Hate to waste it ...Can you think of anywhere else to use it if not?

Afraid not. Not for this case. Higher density would be better, in this specific case, which is why I suggested OC705, if you can get it. But 703 is also OK. We can use the duct liner in the soffits, though. Both the "soffits" above the slotted polys, but more importantly the speaker soffits. You are going to need quite a bit of insulation to fill those. We could even do an experiment, and see how it works for the hangers under the speakers: it's worth a try. Make one set of hangers normally, and one set with duct liner, then swap them out to see if there's a substantial difference. For the "soffits" above the polys, I would cut the duct liner to the same shape as the floor of the soffit, and stack it up in layers. But first, what type of duct liner is it? Brand / code.... I'd like to see if it is suitable... - Stuart -

Its the Johns Manville Linacoustic RC 1" R value 4.2. How's about inside the soffit walls? Layered to depth of course... You'll be happy to know that the insulation removal punishment is underway and possibly having the desired effect... :P

Johns Manville Linacoustic RC 1"

:thu: That's fine, but not so good in the lows (to be expected: it's only 1" thick). So I'd recommend the following "fill" for the soffits above the poly's: Starting from the front, and going back towards the wall: Fabric finish --- cheap black light blocking fabric --- 3 mil plastic --- 2" OC703 standing up vertically, on edge --- horizontal layers of duct liner stacked up --- insulation in rear stud bays --- sheathing. That should give you decent performance in the lows, and keep the highs nice.

You'll be happy to know that the insulation removal punishment is underway and possibly having the desired effect..

I figured you were about due for another "workout" like that! :) Glad you appreciate the effort... The good news is that there's not much more insulation to do now... the bits above the doors, the soffits, and the cloud. - Stuart -

Fun with floors...

Fun with floors...

Looks pretty nice, actually! :thu: Hint: Once the floor is done, get an old piece of carpet, flip it over (fluffy side down, rough side up), and cover your complete floor with that. That's to protect it from dropped tools, dropped materials, you falling off the ladder ... :) Of course, you'll need to take that out for each REW test... And speaking of REW tests, that flooring will probably change things slightly. No big deal, of course, but it will be interesting to see what it does. - Stuart -