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PostPosted: Fri Dec 15, 2017 7:40 am 
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Location: Boston
Hi All,

I’ve been reading for a long time, but this is my first post, although I have edited it as I have been able to answer some of my own questions after more extensive digging. I still have a few things that I am confused about. Hopefully you can help!

I have a basement room that I was able to build out (to a certain degree) when I moved in with my wife. It was an unfinished basement, so I was able to build in some nice features, but was limited in dimensions due to existing features and mechanicals. I also had to design around the space being mainly a living area with a studio space in one part of it. It is a very unique space in that the “control room” or studio section is sort of its own area off of the main room. I believe that most of the acoustic calculations will be based off of the “control room” area, with the exception being that the rear wall is much further away and there would be a big open side in back of the mix position.

A few notes about the room construction:

- Walls are concrete on all external walls (most of the walls of the control area). All concrete walls have 2” foam insulation, then 1” air space, then a 3.5” steel stud framed wall filled with 3” Roxul safe n’ sound mineral wool and finished with ½” sheetrock. All internal walls are wood framed with same Roxul and sheetrock. So add about 7” to all external wall measurements for the difference from the finished sheetrock (shown on layout drawing) to the concrete wall surface.

- Floor is concrete with ¼” carpet pad and carpet.

- Ceiling is Armstrong 954 tiles (backed by 3” Roxul safe n’ sound at entire “control room” area.) 93” - carpet to drop ceiling. About 112” carpet to plywood subfloor above drop ceiling (entire ceiling has standard pink insulation, R13 I think, at subfloor as well.)

- Soffit to right of room is stuffed with Roxul safe n' sound to quiet down a drain pipe and help in general.

- Existing treatment is 2 Real Traps Mega Traps in front bottom corners on floor (one in each); GIK Acoustics bass traps on front wall (6”), front corners (8”), and side walls (6” by speakers, then 4” further back), 2” clouds. There is also a 2’x4’ and a 2’x6’ custom trap in the back corner.

- All furniture must stay essentially where it is if I want to stay married, which I do.


QUESTIONS:

1) I’m planning on building out a soffit mount (flush mount) design. Would I need to do additional splayed (resonator) walls or would it be acceptable to just do the two corners, maybe using some of the existing traps on the sides of the soffits as space is very limited (maybe with 4'x8' MDF)?

2) What is the best way to even out the acoustics of the "L" shape of the room? Bass trap panels on left side, right side, both sides, or something else?


Thanks for any and all help you can offer!

Best,
Dan


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PostPosted: Wed Jan 03, 2018 8:43 am 
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Location: Santiago, Chile
Hi Dan, and Welcome! :)

Quote:
I believe that most of the acoustic calculations will be based off of the “control room” area, with the exception being that the rear wall is much further away and there would be a big open side in back of the mix position.
Actually, the real response will be both rooms individually, and both together: there will be a clear change in the decay response, where the acoustics of the overall larger room takes over from the smaller control room. In other words, you'll have two decay rates, one of which is dominant early on, and the other taking over later. They wont be even, either in frequency or in time. That's a consequence of having different spaces that are coupled acoustically.

There's also the issue of symmetry: the area where you have the mix position is very asymmetrical, so your left ear will be hearing an entirely different acoustics response from your right ear. The way to fix that is to build a wall on the left side of the mix position, to match the right side and make it symmetrical. That wall only needs to go back another few feet, to improve things to a reasonable (but not optimum) situation. The way it is right now, I can't see you getting a usable acoustic environment. You will be subconsciously "skewing" the mix, to compensate for the lack of symmetry, so your mixes will not translate well.

Quote:
So add about 7” to all external wall measurements for the difference from the finished sheetrock (shown on layout drawing) to the concrete wall surface.
With only a single layer of 1/2" drywall on there, your modal issues will likely be more associated with the concrete walls than the actual visible surface. You might even find that you have modal issues associated with BOTH leaves, to a certain extent. And perhaps also some membrane trap effect from the drywall...

I would suggest that you do a full REW test the way you have it right now, to see exactly what type of response you are getting. Here's how: viewtopic.php?f=3&t=21122

Quote:
- Floor is concrete with ¼” carpet pad and carpet.
You'll have to get rid of that if you want decent acoustics: Carpet is a pretty good way of trashing your room acoustics, since it does the exact opposite of what small rooms need. Carpet does the exact opposite of what you need in a small room. Small rooms need a lot of bass trapping (the smaller the room is, the more it needs), some controlled absorption in the mid range on a descending curve (more at low mids, less at high mids), and little to no absorption in the high end. Carpet does the exact opposite: It sucks out all of the high end wonderfully, absorbs some of the mid range randomly on an ascending curve, and does nothing at all to the low end. So not only is it useless, it actually makes things worse.

Quote:
- Ceiling is Armstrong 954 tiles
Those are not much use either! I would suggest that you take them out, and do the entire ceiling as pure absorption, then hang a cloud below it, angled and hard-backed.

Quote:
93” - carpet to drop ceiling. About 112” carpet to plywood subfloor above drop ceiling
Excellent! So you have an extra 19" of very usable space up there! I'm guessing that there are some large sized joists, and perhaps pipes, ducts and electrical work up there too, but that's not a problem, and can be dealt with. Having all that extra space up there is a major blessing! If that were my room, I would definitely pull the drop ceiling out, install whatever insulation I need up between the joists, perhaps cover any HVAC ducts that might be a problem, then make a plain cloth ceiling, and hang a large hard-backed cloud below it, at a suitable angle.
Quote:
1) I’m planning on building out a soffit mount (flush mount) design. Would I need to do additional splayed (resonator) walls or would it be acceptable to just do the two corners, maybe using some of the existing traps on the sides of the soffits as space is very limited (maybe with 4'x8' MDF)?
I highly recommend soffit mounting in general, and your Focals can certainly benefit from that, but I'm not sure if you have enough space to do that. The soffit structure needs to be massive, solid, rigid, and you need to leave enough space around the speaker for a massive, rigid enclosure box, plus air ventilation system behind it, plus a thick, heavy, massive baffle on the front... that can take up quite a bit of space. You'll have to do the layout first, to see if it is even feasible. Since it all has to be angled, and the Focals are quite wide, and the baffles need to be at least twice as wide to be effective, I'm concerned that there just isn't enough space to do it well. Try it out in SketchUp, and see if you can actually fit them in.

Quote:
2) What is the best way to even out the acoustics of the "L" shape of the room? Bass trap panels on left side, right side, both sides, or something else?
Simple answer: you can't! At least, not with treatment alone. More complete answer: You can, if you build a wall on the left side of the mix position that mirrors the wall on the right. Symmetry is critical, and key, to good mix translation. If you build the wall, and treat suitably, then you can fix that problem.

Bass traps alone won't do anything to fix the symmetry issue: Bass traps are basically just very large globs of acoustic absorption, with not much mass, no rigidity, not sealed, soft, and not reflective. What you need to fix that room is a hard, rigid, massive, reflective surface on the left to match the one on the right. THEN you can add bass traps.

In addition to all of the above, you need to fix the layout an geometry of your mix position. Right now, it is way off. First of all, get your speaker off the desk and onto stands behind the desk, up tight against the front wall. The stands must be massive (very heavy), and set correct so that the height of the acoustic axis of your speakers ends up at 48 inches above the floor. The positions of the speakers relative to the side walls also needs to be fixed, as does the toe-in angle. Right now you have your speakers in the corners, which is about the worst possible place. Then need to be moved out of the corners (closer together) and the angle needs to be adjusted such that they are both aimed at the same spot, about 16" behind your head. Yes, that will be a somewhat lower angle than you have at present, but there's not a lot of choice here! The room is very narrow, so you are stuck with "what can be", not "what it would be nice to have if the room where bigger".

If you don't build the soffits in the end, then you will need a whole bunch more bass trapping in those corners. I'd suggest Superchunk style traps, made with OC-703, floor to ceiling, and as large as you can possibly make them.

It's a very challenging situation you have! It can be improved, yes, but it's not going to be a world-class mixing space, with top-notch acoustics. That doesn't mean it will be bad! It can be good: Just that it won't be exceptional.


- Stuart -

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PostPosted: Fri Jan 05, 2018 4:21 am 
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Joined: Thu Dec 14, 2017 5:45 am
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Location: Boston
Hi Stuart,

Thank you for the detailed reply!

I have been starting to realize that the situation with this room is much worse than I thought it would be. You have pretty much confirmed that. Especially because the carpet, ceiling tiles, and walls are going to have to stay as they are, as this is not a dedicated mix space. It is actually more of a living room with my stuff in the corner. My wife would kill me if I started making those types of alterations. The good news is that some time in the next few years we will are planning on buying a new house and she WANTS me to build a dedicated mix room there. Definitely my best option will be a careful, thought out, properly designed, planned, and built new room. Which I look forward to getting started on a little bit down the road.

As for this room, I have become accepting of the idea that it will never sound great, and I likely won't do much mixing for a while. Reworking a mix 5 times to get it OK sounding is not something I enjoy. However, if there are things I can do to get it to sound OK and maybe only have to tweak mixes a little once or twice, that would be nice, and I guess it is my current goal.

I am willing to go with soffit mounts or super chunk, but as you said, the space is very limited. To further complicate things, there is a water shutoff and other plumbing above some of the corner ceiling tiles which means I can't completely cover that up unless I redo the plumbing. Not out of the question, but not something I want to do unless the benefit would be great enough. Maybe if I went with soffits, they could stop a foot or so under the ceiling tiles to maintain access? Not sure if that is bad or acceptable.

One quick note - the speakers are actually on stands behind the desk, and on IsoAcoustics isolation platforms (which made quite a noticeable improvement in clarity), and not on the desk.


So I guess I have a few followup questions:

1) With these monitors, what would be the ideal distance from the side walls?

2) I assume the ideal toe-in angle would be based on mix position (16" behind that). It would seem that I am stuck working in front of the 25% position. I obviously don't want to be at the 25% spot, and the 33% spot pushes all my stuff into the main part of the room, which won't work for my wife. I also notice what seems to be the acoustics of the 2 rectangles combining around that area, which is bad. So how best to position myself given all that? Should I be as close to the front as possible while having the monitors either soffited or on stands? I couldn't find much info on the best places to be in front of the 25%.

3) I think you are correct about these monitors not having enough room to be soffited here, as least in horizontal position. Would it be better to switch them to the vertical orientation? They would then probably fit, but would have to be towords the corners. This would also allow me to choose which speaker the upper-mids and which speaker the low-mids come out of (if there is a benefit to making one higher or lower in this room, although maybe it would just mess things up more given the small size of the room.)

4) I'm not averse to trading these monitors in for the smaller Solo B6 model. Obviously this would help with soffit mounting. Do you think this would help in general given the small size of the room (soffited or not)?

5) I was also looking into the use of tube traps. Do you have any experience with these, and do you think it would be a worthwhile avenue to pursue given everything else? They are very expensive, so I probably wouldn't be able to have too many unless I were to DIY.

6) What about sound treatment a few feet behind mix position? Would any sort of gobos, traps, etc., be at all useful here? Anything that was somewhat moveable and reasonably attractive would be something I could work with.


Thanks again for your help and any future advise you may have. Also, I have started to learn SketchUp. It is amazing! Very much looking froward to using it for the design of my next room.

Best,
Dan


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