Hello, all.
First time poster here. Man, you guys are incredible! I've learned SO much in the past month, reading through these threads. Thank you SO much! And a special "hats off" to the tireless moderators.
But here's the problem - Did you all notice the phrase, "the past month?" You see, I'm not an acoustical engeneer. I just want to make music. But I have become a victim of a pretty serious case of analysis paralysis. But I think I'm getting close to a solution that fits my budget and my mediocre carpentry skills. So, I'd really appreciate some insight from you experts, before I decide to just wrap myself in muslin and stand in the corner!
So here's the deal:
New house. Below (hopefully) is a crude mock-up of the mix/control room and the vocal booth. The vocal booth is under the stairs, hence the sloped ceiling. The other door opens up to a decent-sized "great room" (25' X 21'), which could easily fit a band... someday... maybe... But, if I try to think about THAT as well, I think my head will explode.
I'm prepared to buy as much 4" Fibrex as needed. I can get 2' X 4", 4 lb. density for $7.20/sheet, and 2' X 4', 8 lb. density for $8.64/sheet. (I THINK that's good, right?)
There's no way I'm capable of building slats and Helmholtzes and whatnot, so I think I'm leaning toward a variation of the Studiotips SuperChunk. It is not my desire to overwhelm anyone, so I will number my questions. Feel free to answer as much or as little as you wish.
(I plan to cut 4 triangles from each 2' X 4' panel)
1. Is there any benefit to spacing out the triangles, other than cost-savings? Wouldn't this provide more surface area? Say, 4 triangles per 4' panel? Or maybe leave 4" gaps between triangles (6 triangles per 4' panel)?
2. I've learned from this forum that denser material absorbs more bass, but may reflect highs, so what if I used 8 lb. for the triangles and 4 lb. for the face?
3. Is it o.k. to glue the face directly to the triangles? I read somewhere that it should not touch the insulation behind it, but that was involving a sealed slat/slot thing.
4. Since I don't wish to glue anything directly to the walls and ceiling, I plan on attaching 1" X 2" firing strips length-wise (perpendicular to the triangles), one strip for each of the equilateral sides, thereby providing one contact point on each side, and placing the triangles 1" away from the wall and ceiling. Is this 1" helpful?
5. And lastly (for now), after all is said and done, is THISbetter than any of the above? (Using just fabric instead of slats, and using 4 lb. on the face and 8 lb. behind that, leaving a 2" or 3" air gap?)
Man, I'm exhausted! And all I did was write the QUESTIONS!!!
Thanks, all!
rich
(I may not be able to return here for 24 hours or so)
1. Is there any benefit to spacing out the triangles, other than cost-savings? Wouldn't this provide more surface area? Say, 4 triangles per 4' panel? Or maybe leave 4" gaps between triangles (6 triangles per 4' panel)?
I don't think anyone's ever done that and reported back; but for LF absorption, it would LESSEN the effect since only half the face would be absorbent to lows.
2. I've learned from this forum that denser material absorbs more bass, but may reflect highs, so what if I used 8 lb. for the triangles and 4 lb. for the face?
4 lbs is already kinda high for any but direct incidence - I'd stick with straight 4 lb if that's your two choices.
3. Is it o.k. to glue the face directly to the triangles? I read somewhere that it should not touch the insulation behind it, but that was involving a sealed slat/slot thing.
Only problem with glue would be if it's a continuous (or even majority) layer when dry; then it would form a membrane and restrict mid/high absorption.
4. Since I don't wish to glue anything directly to the walls and ceiling, I plan on attaching 1" X 2" firing strips length-wise (perpendicular to the triangles), one strip for each of the equilateral sides, thereby providing one contact point on each side, and placing the triangles 1" away from the wall and ceiling. Is this 1" helpful?
Unlikely to be noticeable - consider its magnitude compared to the rest of the absorber.
5. And lastly (for now), after all is said and done, is THIS better than any of the above? (Using just fabric instead of slats, and using 4 lb. on the face and 8 lb. behind that, leaving a 2" or 3" air gap?)
Not that much difference - placement would be the same, you're only using straight absorption instead of some helmholtz and some absorption. The main difference would be that using slats will keep the room brighter. IF that's what you want, try wrapping your 4 lb stuff in light painters plastic dropcloths (about 1/2 mil or so) - this will absorb less highs. Not exactly the SAME result as slats, but similar... Steve
I'm new hear but completely agree Sharward on turning the room 90 degrees. How I wanted to face the long wall in my room, I did an extensive search of all studio designs on this forum, and www.johnslayers.com and only found one (I think) that faces the long wall:
http://www.johnlsayers.com/Studio/Mainpage/MP-Funky.htm
The only other was... I can't remember the thread but someone posted a design facing the long wall in a control room and John's comment (I believe 1st comment) was to turn the room 90 degrees... and it got turned.
Marc
WSDG does lots of CR's facing the long wall; difference is, these rooms are bigger than most of our entire studios (all rooms together) - in these cases, there is enough distance the short way NOT to cause early reflection problems, PLUS the reflection path to side walls becomes long enough NOT to require "mirror" treatments for THOSE early reflections (reflection path more than 20 feet longer than direct sound path)... Steve
Good catch, Keith; can you recommend a good "gator gun"? think I've shot the barrel out of my .44 mag, and the bastards still keep comin... :evil:
OK, I'm back. Sorry, life got a bit distracting. Thanks for the feedback guys.
Steve- I'm sorry. I guess I still don't get it. Apparently both the Fibrex AND I are too dense. I thought bass trapping was all about mass, mass, mass. I just thought the denser the better. Sure, I have other choices. I can go with the good old 703.
However, I just found out that the Fibrex I had looked at in the store (and mentioned in my post) was NOT the Fibrex I saw on their website. Turns out the store had the industrial board. What I wanted was the Sound Attenuation Fire Batt (SAFB). The figures on the 4" look fantastic. And the density is 2.5 lbs. That's good, right?
125Hz 0.97
250Hz 1.28
500Hz 1.25
1k 1.10
2k 1.10
4k 1.09
NRC 1.20
1. So, does this 4" SAFB sound like a good choice?
2. Are traps only necessary where the back wall meets the ceiling, and the 2 rear vertical corners? Are traps really necessary where the side walls meet the ceiling? And how about where the front wall meets the ceiling, and the 2 front vertical corners?
3. And one last alternate method: What about tightly rolling up a 2 X 4 sheet, wrapping in plastic, and hanging in the corner with straps, then covering with a face made of another 2 X 4 panel?
4. Or is filling the corners with cut triangles (no gaps) the best way to go? OR... is merely mounting a panel across the corner really good enough? Is filling in the corners just overkill?
5. And considering the dimensions of the room, do you guys REALLY think it will make a big difference if I position myself lengthwise? Really??? After all, I'm going to put 4" panels on the rear wall as well. I'll do it if you guys really feel strongly about it. But I'd really rather not.
Thanks again, guys.
1. So, does this 4" SAFB sound like a good choice?
Yup.
2. Are traps only necessary where the back wall meets the ceiling, and the 2 rear vertical corners? Are traps really necessary where the side walls meet the ceiling? And how about where the front wall meets the ceiling, and the 2 front vertical corners?
Smaller the room, the worse your modes will treat you. Yours has two nearly identical dimensions, so will need more treatment to get closer to flat response.
A start for ALL smaller rooms is doing all vertical corners, front behind speakers, first reflection points on side walls and ceiling, and heavy absorption to the rear of the mix position. Wall-ceiling corners are next if this doesn't finish the job of flat response.
3. And one last alternate method: What about tightly rolling up a 2 X 4 sheet, wrapping in plastic, and hanging in the corner with straps, then covering with a face made of another 2 X 4 panel?
Best is a complete fill, ala Superchunks; next best would be a second thickness right behind the diagonal outer layer of absorption. Last would be a single layer of 4" - less than that and you may or may not even hear the difference.
4. Or is filling the corners with cut triangles (no gaps) the best way to go? OR... is merely mounting a panel across the corner really good enough? Is filling in the corners just overkill?
See above.
5. And considering the dimensions of the room, do you guys REALLY think it will make a big difference if I position myself lengthwise? Really??? After all, I'm going to put 4" panels on the rear wall as well. I'll do it if you guys really feel strongly about it. But I'd really rather not.
Yes, I do; for one thing, the narrow dimension is likely to put you exactly centered between walls, in an UNNECESSARY null/peak area. Rotating 90 degrees solves that problem. It also creates another one, that of the window; you will probably need a movable absorber for the window during mixdowns.
The only null/peak zone you have little choice in is the left/right one - anything else and stereo imaging goes funky. Other than that, you should NOT be in either peak or null positions for any harmonic of any room mode.
I can see why you're hesitant, for one thing the window; for another, the couch would need to be forward enough to clear the door. The good news is, this will probably put the couch in a better spot for listening than against the wall anyway - less bass perhaps, but better overall balance of sound... Steve
Thanks, Steve. You've convinced me. 90 degrees it is.
So, regarding the window, do you think it is ok to place 4" panels starting on the 3'-4" high sill, and going as high as 7'? That would allow for the top window pane to be uncovered, letting in some light.
(My speaker stands are 43", and I use Mackie HR824s. Also, I may set the speakers on a 4" piece of SAFB. Of course, I'll have to angle them downward a bit.)
And speaking of windows, have you ever heard of soundproofwindows.com? You keep your old window. These mount flush with the wall, using the window cavity as air space. Any opinions? The one window will run me just under $700.
Oh, and the new rear wall seems to have its challenges, also. I'll have to mount a 4" panel on the back side of the door, and it looks like I'll have to have the door closed whenever I'm mixing. Also, maybe I shouldn't install a window there. That would sacrifice the space for a much needed panel, right?
And I guess I'll need to use a moveable trap for the one rear corner, since it will block the entrance to the vocal booth.
Man, it's always something...
So, regarding the window, do you think it is ok to place 4" panels starting on the 3'-4" high sill, and going as high as 7'? That would allow for the top window pane to be uncovered, letting in some light.
Should work fine.
(My speaker stands are 43", and I use Mackie HR824s. Also, I may set the speakers on a 4" piece of SAFB. Of course, I'll have to angle them downward a bit.)
Keep center of woofers away from half your ceiling height;
And speaking of windows, have you ever heard of soundproofwindows.com? You keep your old window. These mount flush with the wall, using the window cavity as air space. Any opinions? The one window will run me just under $700.
Heard of 'em, checked out their site, not totally impressed with their suggestions or prices. You should be able to put another, identical window to the one that's there in the same location (maximum air gap) and get similar results for a LOT less $$$.
Oh, and the new rear wall seems to have its challenges, also. I'll have to mount a 4" panel on the back side of the door, and it looks like I'll have to have the door closed whenever I'm mixing. Also, maybe I shouldn't install a window there. That would sacrifice the space for a much needed panel, right?
Unless you want to build a PORTABLE panel, just move it into place while mixing; advantage there is if you don't put a solid back on the panel, you can "tune" the amount of low end trapping by how far way from the wall you place the panel... Steve
Thanks so much, Steve. I think I finally have a plan. Can't wait to get started.
And yet another question. I'll be hanging clouds (4" SAFB), covering the majority of the ceiling. Should I angle the cloud, or is that concept just for a reflective surface? I would think it's not necessary, since it's an absorptive surface anyway.
Thanks again.
Steve, I'm sorry, but I'll have to ask again. Should I angle the cloud? Or is that unnecessary, since it is an absorptive surface anyway?
As I get started, I'd love to give back to this forum since I've taken so much. So, I would like to post photos as I progress. I think I'm coming at this at an angle that may ring true with folks who are musicians more than they are acoustics experts.
Funny, I spoke with an engineer here in Nashville, and he mentioned a handful of very prominent studios here, and said they all sounded "bad." He said, "Just play a few of your favorite CDs, and adapt." He also advised that I stop obsessing, put some insulation up, and start making music.
Wise words, indeed.
Yes they are wise words; and no, you don't need to angle your cloud. Just make it thick (2" is absolute minimum, 4" if you can) and space it away from the ceiing by a few inches. Center it between a line from speaker to speaker and your head. Play some CD's and listen 8)
Well, for the past few months, I've done nothing but sit and stare and think and scribble and sit and stare and think some more. I had absolutely no idea where to begin. I knew absolutely nothing about room acoustics.
I'm so glad I stumbled onto this forum. (I must have googled something or other...) Steve, thanks to you and this forum, today's the day that I take "that thar screw gun" and start makin' a mess!
Cover me boys, I'm goin' in. Yee...Ha!!!
OK, so no screw gun yet. But I'm glad I thought about things a bit more. Saves me from ripping stuff out later.
Steve, in your first reply to me, you mentioned about wrapping plastic around the traps. But back then, we were talking about the 4lb density stuff. Does this still apply to the 2.5lb stuff also?
And if so, do I need to completely WRAP the traps with the plastic, or can I just stretch plastic over the face of it? That won't have any adverse affects like a drum head, will it?
Also, now I'm thinking about framing the traps with, say, 1' X 3" pine, with the 3" sides facing the room. The 3" won't cause any reflection problems, will it?
(This frame is what I was thinking of stapling the plastic to, by the way)
Thanks.
hmm, I'm kinda in the same boat (doors in bad places). What about running your traps horizontaly along the floor/wall and ceiling wall corners?
Just a thought.
Thanks, lomky. I do plan on putting a trap on the ceiling/wall corner, and I think I have a pretty good idea on how to make moveable traps and panels. If they work out, I'll share them here.
Hey, Steve...
My question still stands. Is it OK to just face the traps with plastic?
And framing the traps with 3" pine won't cause a significant reflection problem, will it?
Also, I will be putting a cloud over almost the entire ceiling. Is it really necessary at all to put traps in the wall/ceiling corners on the sides?
(I had to special order the Fibrex, so I have two more weeks to "plan" (obsess).
Got your PM -
My question still stands. Is it OK to just face the traps with plastic?
You can; or you can put the fibrex into garbage bags (not the expensive, thick ones) - idea is to contain the fibers AND brighten the room a bit by reducing high frequency absorption. If you stay THIN, like 1/2 mil or so (painter's plastic drop cloths, for example) you won't affect lows or mids while doing this. Bottom line - complete wrap with ONE layer of thin plastic won't hurt anything, and will better contain any loose fibers. Acoustically, once you've covered the front (and sides) with thin plastic, doing the back won't make any difference (acoustically, that is)
And framing the traps with 3" pine won't cause a significant reflection problem, will it?
Actually, YES. If you frame them so they look "Nice", you're covering up their edges - this replaces absorption with reflections/diffractions. If you do that (the frames) I'd recommend larger surface areas (maybe a foot more in either direction) to compensate for the loss of edge absorption, AND to move any reflections further away from the mix position - this should do two things - one, it will help direct any reflections elsewhere, and two, any acoustic disturbance caused by the frame will have a longer path back to the mix position so will DIFFUSE a bit more.
Also, I will be putting a cloud over almost the entire ceiling. Is it really necessary at all to put traps in the wall/ceiling corners on the sides?
Where your door is, and that SILL running along the one wall, I would think it'd be hard to do all four VERTICAL corners; so you probably WILL need to do at least the left and right sides' wall/ceiling corners.
I'd do the stuff you KNOW you're gonna do first; then listen and TEST - you'll know then if you have enough absorption. My guess is NOT, but every space is just enough different to make me a liar... Steve
Thanks again, Steve.
Wow. Just when I thought I've read everything, this morning I noticed something that I must have skimmed over earlier. While revisiting the SAE Institute website, I read that pegboard can be used for the face of a panel absorber. I'm wondering if we could discuss this a bit, as this opens up a whole new world of possibilities.
I understand that this involves a sealed cavity, right? Originally, I was not interested in anything sealed, as this would involve more trauma to the walls and ceiling than I was willing to inflict. (I'm always thinking about how easy it would be to dismantle/repair everything if I were to move) But now, I realize that I could make quite a few of my absorbers portable (and sealed), and leave my walls untouched!
First, let me ask about the vertical corner traps. So, I could theoretically use plywood for the 2 equal sides, and pegboard for the face. This would obviously solve the problem of absorbing too many high frequencies that we addressed earlier (wrapping in plastic). Now, is it possible, and more importantly, is it beneficial, to combine the theory behind a panel absorber and the theory behind the Superchunk? Or is it the airspace that makes a panel absorber work?
If this is a good idea, then here's the plan:
Plywood for the 2 equal sides.
Pegboard for the face.
Fill entire trap with Fibrex, ala Superchunks.
Attach cloth to the inside of the pegboard.
One sheet of plywood cut in half lengthwise would be enough for one 8' tall corner trap. Or I'd probably make two 4' high traps and stack them. They would be easier to move.
Now, how about this? Since pegboard isn't very thick, and bends easily, why not curve the face and get some diffusion action going while I'm at it?
So, if (IF) this turns out to be a good idea, I'd have a follow-up question:
Which is better: Plywood or MDF, and why?
Or, if this turns out to be a <i>bad</i> idea, then will someone please stop me before I waste any more time thinking about it?
Curving the pegboard makes it a polycylindrical absorber - NOT having insulation up against the curve makes it very narrow band (not good) - and the standard available types of pegboard are kind of limited as to frequency - one example calculation puts 1/8" pegboard, 1/8" holes on 1" centers, spaced off the wall by 16", at a frequency of around 135 hZ. Here's the formula -
http://www.johnlsayers.com/phpBB2/download.php?id=6680
Note that this is for panels with SUBDIVIDED air space - this means that in order for this formula to be accurate, each hole must have a divider around it. Not fun to build. I've yet to see a formula for NON-divided air spaces, I'm inclined to think (lacking evidence to the contrary) that the reason the corner slat absorbers work without figuring this in is that they are a VARIABLE air gap behind. Keep in mind that I'm NOT even close to being an acoustician and have not built and tested bunches of these with different parameters and actually MEASURED the results - all I know is that John's been using them for years with good success...
Bottom line here - for your small room, I would NOT get into tuned traps, with the possible exception of a couple panel traps tuned to 60 hZ and below, which are the only areas your room dimensions may show problems at. But the first thing to do is ALWAYS broadband absorption, and usually that's ALL you need unless the room has unusually bad dimensions... Steve
Thanks for the speedy reply, Steve.
Well, only a couple hours and a couple cups of coffee spent going down that dead-end street. OK, back to plan "A". Just thought I may have stumbled onto something. Wood = Tuned. No Wood = Broadband. Got it.
I'd LIKE to ask just exactly how I would tune a trap to 60 hz, (and where they would go) but I'm afraid you'll throw some other "e = mc hammer" formula at me. And those things just make my head hurt.
Where they'd go depends on which room mode is causing the problem; panel traps work on sound PRESSURE, not velocity; so they need to be at pressure peaks - one basic axial mode calculator that gives a good visual is the one at harman's site, linked in this forum about 4th from the top of the page - it shows a quasi-sine wave of sound pressure for each of 4 harmonics of each dimension of your room, so you can tell where the axial modes peak and where they're nulled in pressure.
Generally, if you have a mode that's caused by the length of a room, there are two approaches - since the two short walls will be at high pressure for ALL modes, you could place the traps on those walls (although modes for width may interfere, this gets trickier) - or you could place them along the LONG wall, at different percentages of the wall's length depending on which harmonic you're trying to treat.
If you download the calculator and open it (requires Excel on your computer) you'll see that First harmonics ONLY peak at the ends; so traps for this should be in a corner, preferably on the short wall for long wall mode and vice versa. The second harmonic (black graph) could be placed the same, OR it could be placed at the center of the LONG wall (assuming it's the LONG wall's mode you're treating, and at the second harmonic frequency) - this is because the graph shows another PEAK at the center of the dimension.
Third harmonics (shown in red) are seen in the graph to peak at 1/3 and 2/3 of each dimension, so a frequency that coincides with a third harmonic would need its panel trap (tuned to that frequency) placed on that wall's 1/3 and/or 2/3 points (IOW, where the wave will peak in pressure)
Fourth harmonics (yellow) peak at every 1/4 of the dimension they're caused by, so could be placed at any 1/4 or 1/2 of their corresponding wall dimension.
More, including the "MC Hammer" formula, here
http://www.johnlsayers.com/phpBB2/viewtopic.php?p=41713
Hope I didn't just make things MORE confusing... Steve
Steve
Quite honestly, I've always scrolled right past those graphs when I saw them in someone's post. It just looked WAY too over my head. But, I just now downloaded the xls file and typed in my numbers. Then I re-read your post, while looking at the graph, and I can now say I understand what that stuff means... sort of. Wow. Thanks.
But what it's telling me is this: Something is peaking somewhere all the time. IOW, why would I tune a trap to the 2nd harmonic and place it at the half-way point on the wall where it peaks, when the 4th harmonic also peaks there? Sounds like a job for a broadband absorber. Or, why would I tune a trap for the 3rd harmonic, if the 4th harmonic peaks right next to it? Broadband again.
So, how about I go with broadband (4" fibrex), completely covering all walls, and superchunks in the 4 vertical corners and front and rear wall/ceiling corners.. I'll hang a cloud for the majority of the ceiling. I'll wrap all corner traps with plastic. No plastic for the clouds (I have that wood floor).
RE: the side walls, how about this for keeping the room from being too dead? EXCEPT for the first reflection points near the mix position (which will NOT be wrapped): How about, on one side wall, I wrap every OTHER panel in plastic, and on the other side wall, do the same, except wrap the OTHER every other panel? You know? That way, for each pair of panels that are directly opposite each other, one will be wrapped and one will not.
Even if I drop the cloud down 10", I'll still have a comfortable 9' ceiling. So, that makes for 9' high walls, of course. So, I could line vertical 2 X 4 panels side by side, centering them vertically on the wall, or I could use pairs of vertical panels, one above the other, thereby covering 8' of vertical wall space. Is it helpful to go almost all the way to the floor? I don't mind. I have enough fibrex. I just want to know if it's TOO much.
All good ideas; for one thing, even looking at the other two types of modes your room isn't too bad; just a couple of lower frequency things that MAY cause some lack of SPL at 60 hZ and below.
For ANY room, the first thing to do is broadband absorption - in a large percentage of cases, this will be all that's necessary to smooth out the room response.
When that's NOT the case, this is when tuned traps may be necessary. Where you locate them is decided by which harmonic is causing the problem; and if you tune a panel trap to 4th harmonic and place it where second and fourth harmonics peak, it's tuned to the 4th so won't affect the second harmonic AS MUCH as it does the frequency it's tuned to.
The thing you FIRST need to do, before you can FIX something, is to MEASURE it; without that, you have no idea if anything's even BROKEN. For that, there's help too; check this out
http://homepage.ntlworld.com/john.mulcahy/roomeq/
HTH... Steve