Members rpjazzguitar Posted October 12, 2014 Members Share Posted October 12, 2014 I guess this post is more about getting rid of sound than making it. I've set up a 17x15 practice room. I found, on the ATS website (they make acoustic panels) a calculator that tells me I need 100 sq ft of acoustic treatment to get the reverberation under control. My wife tells me that I need less. I put in a drum set, I hit it and I thought it was too loud, even though I didn't hit it that hard. So, do these calculators work? What I did was buy thick curtains from JC Penney for a sliding glass door and a big window. Also 4 2x4 foot ATS panels that haven't arrived yet. I think it's going to be okay. If not, I'll sedate the drummer. Drums don't sound quite as loud now. But, I'm still wondering, do these calculators work? Might I really need a bass trap? I know, I'll try it and see. First quintet session is Monday. Rick PS. It's been an absolute pleasure to read Agedhorse's posts for the last few years (I'm here intermittently). The field hardly matters -- I love listening to somebody who knows what hes talking about. No disrespect to other very knowledgeable posters, but I saw that AH may not be here so much any more, if I read that right. Link to comment Share on other sites More sharing options...
Members wesg Posted October 12, 2014 Members Share Posted October 12, 2014 Andy's still around. I'm in a very similar practice space, I don't find the reverb objectionable but it's hard to get the GBF we want. I am using a feedback eliminator on each vocal mic now to get the room's resonant frequencies cut deeply without too much collateral damage. My current mission is to try dampening the sound going upstairs a bit. Currently, there is only 1/2" of fiberglass ceiling tile between the band and the floor upstairs. I'm going to throw in some Roxul Safe'n'Sound between the floor joists this weekend to see if that makes a difference at all. I'd like to change to acoustic ceiling tile, but I don't think I'm allowed to by fire code. There is a wood stove in the practice area. In an ideal world, I would re-do the ceiling in QuietRock, but that's very impractical. So, you are trying to reduce reverb rather than sound proof, what is your ceiling made of? What is your floor made of? Have you tried putting down a rug? Have you got any office dividers you can bring home? Are you going to put these panels on the walls or the ceiling? Do you know which is causing the objectionable reverb? Wes Link to comment Share on other sites More sharing options...
Members dboomer Posted October 12, 2014 Members Share Posted October 12, 2014 Hey Wes. You'll have to check code but if you want to stop the sound from traveling outside the room you need to block it with mass. Fiberglass won't help. You need to Sheetrock the ceiling with a couple of layers but you need a structure that can support it. As far as cutting down reverb inside a room you want absorption. But you have to be careful to absorb all the frequencies that are a problem ( which usually means broadband). If you use curtains they will really only soak up frequencies above about 1k. Now you'll have very unbalanced reverb which is probably worse. Remember that when you use those calculatiors that 100% absorption really means about a 20% reduction in level. Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 12, 2014 Members Share Posted October 12, 2014 Thanks for the kind compliments... You need as much absorbtion as you can possibly throw at it. Absorption, as Don points out, is not perfect. It varies with frequency as well as base materials. The rule of thumb when trying to get a difficult space under control is to throw as many "dead cats" as you can at the problem. When calculating absorption, all surfaces count, including the floor and ceiling. Look at the absorption coefficients and response curves, for mid band absorption, it takes a bit of thickness and (lossy) density. Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 12, 2014 Members Share Posted October 12, 2014 Next Saturday the band I play in is performing at a "Rocktoberfest" event in a stupidly lively room (absolutely horrible acoustics... I can't imagine any worst exists). My possible solution to soften the acoustics is that I've invited the local quilting group to go in on the event and display their quilts along "the walls". That should add some color to the bare walls and sop up some of the sound... and they can show-off their quilts to a likely target market (which they seem extremely eager to do). I've never done this sort of thing before... I'll be helping with their setting up the day before... I'm wondering if spacing the displays of quilts out a foot or so from the walls would be better, or flat up against the walls? Link to comment Share on other sites More sharing options...
Members dboomer Posted October 12, 2014 Members Share Posted October 12, 2014 It will absorb more if you space it off the wall a few inches. You get the bounce for free Link to comment Share on other sites More sharing options...
Members Dogoth Posted October 12, 2014 Members Share Posted October 12, 2014 In a room that small I doubt you'd need bass traps (Maybe mid traps :-). The BBC did a lot of studies back in the 50s & 60s about mid sized room acoustics (mostly for studio work but the principals still apply). Here's a link to one of them http://downloads.bbc.co.uk/rd/pubs/archive/pdffiles/monographs/bbc_monograph_64.pdf Bass frequencies need long distances to become "lobey" (is that a word? :-), so most of your issues will be from lo-mids on up (unless you have resonant walls which WILL either help or hamper even bass reproduction). Although it's usually impractical, non parallel walls & ceilings are often of great benefit to the sound (and a horrible waste of space :-). There's a book called "The Audiocyclopedia" that has a great chapter about mid sized room acoustics (citing those BBC studies a lot). If your local library has a copy it might be worth a read. It's some pretty dry stuff with a lot of math but also some generalizations that make sense. Hope this helps Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 12, 2014 Members Share Posted October 12, 2014 It will absorb more if you space it off the wall a few inches. You get the bounce for free Thanks Don... that's what I was thinking. Can you suggest some critical or ideal distance? I'm thinking of offering my stands and trussing for the "quilt hanging apparatus"... there's legs involved with the lighting stands that will off-set the truss a few feet from the walls... we're fixin to hang about 100ft. horizontal and 16ft. high of quilt display in the venue. The quilters have quilt display frames that can be situated smack up against the walls or any distance out from the walls... but assembling the frames and hanging the quilts by that medium seems to be "involved"... compared to just going with the towers and trussing. Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 13, 2014 Members Share Posted October 13, 2014 Towers and truss should work fine. Is it triangle, box or flat truss? Link to comment Share on other sites More sharing options...
Members dboomer Posted October 13, 2014 Members Share Posted October 13, 2014 If you knew the absorption coefficients per frequency of the quilts you could calculate wavelengths and actually tune them. But that ain't gonna happen is it? Best ballpark guess would be between 4 inches and 1 foot. Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 13, 2014 Members Share Posted October 13, 2014 Is it triangle' date=' box or flat truss?[/quote'] What I have on-hand is 4ea. 10ft. sections of box truss (12" as I recall), 4ea. 10ft. sections of triangle truss (12" as I recall), and 6 crank-up towers. I have another 4ea. 10ft. sections of the box truss that's "out on loan" to an area lighting outfit, that I can utilize if need-be. My biggest unknown/question with the idea is how to hang the quilts from the truss, but the quilt folks have assured me they "have the appropriate stuff"... no problem, they have that aspect fully under control. But I'm going in a day early to set-up with the quilters to "make sure". Also I believe the quilt club has a bunch of little LED display booth lights on arms they're fixin to attach to the truss to light-up the quilts... it should look pretty nice. If this works out (and isn't a knock-down drag-out), we'll likely make a regular habit of it to varying degrees when doing local indoor shows in lively rooms as it seems to be a nice marriage of the quilters and our brand of entertainment, the types of events we preform at, the crowds we generally play for, etc... We'll see... Link to comment Share on other sites More sharing options...
Members rpjazzguitar Posted October 14, 2014 Author Members Share Posted October 14, 2014 Had the first band rehearsal today. But first, last night I picked up, for free, off CL, 4 foam cubes 17" on a side. Described by the donor as "acoustic foam". Who knows? My thought was to cut them on the diagonal and stack them in the corner behind the drums. I didn't have time for that, so I just stacked them on a table on one side of the room. There is a commercial carpet, sliding glass door, big window and the rest is sheetrock, some teak bookcases and a good sized futon. I got the thickest curtains JC Penney sells for the door and window -- and extra panels so they're nice and folded. And we played. The drummer, who tends to be loud, didn't bother me. The bassist, playing a 5 string through my 30w Ibanez practice amp (I bought it for $10 at a garage sale, which, sadly, may be the fourth best moment of my life) was either playing too loud, or the room was too live in that frequency range. Late in the day, well after the rehearsal, my 4 2x4 foot ATS panels arrived. So, now I've maybe got a bass problem, I've got the 4 cubes and the 4 panels and I need to place them. The only strategy that I might be able to follow is simply adding acoustic insulation until the silence becomes eerie. Since I don't have all that much available wall space, I don't have a lot of decisions to make about the panels. But, does anybody have an idea about how to use the foam cubes? Does cutting them on the diagonal and stacking them in the corners make any sense? More facetiously, what about one right in front of the bass speaker? How about a remote volume control on the bass amp which I control surreptitiously? More seriously, what about getting the bass amp off the floor, or maybe onto one of the foam cubes? Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 14, 2014 CMS Author Share Posted October 14, 2014 I'd just say, "Hey, can you turn down a bit?" If he then can't hear himself, simply reposition the amp so it's aimed at his head. As a bassist (not a good one) I find that small rooms can be challenging to hear my amp, and this may be what's happening. Link to comment Share on other sites More sharing options...
Members Ambugaton Posted October 14, 2014 Members Share Posted October 14, 2014 Here is what I would do... focus on the problem from its source... which is probably the cheap practice amp. I am guessing that it is producing a large amount of teeth clenching mids. When practiceing... pay attention to what parts and/or notes are creating those trouble frequencies. When you get an idea of where the problem is you can alter the amps eq settings, buy an external eq, or use a better quality amp. If you throw a bunch of bass traps in the corners or sound panels up without knowing the how, when, whys then you might be potentially creating another problem without fixing the current one. Soon you will find yourself lacking low end or having everything sound too thin and flat. Remember that alterations to the room will affect everything, and not just the bass. Other options: If you narrow down the problem and it is specific to mid - slightly high frequencies... I would recommend getting some Roxul 60 Rockboard (3" thickness) and hanging a couple of those around. For lower frequencies I would go with the Roxul 80. The material is cheap and if you put a simple 2x4 frame around it and cover it with some black breathable cloth it looks pretty neat. Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 14, 2014 Members Share Posted October 14, 2014 First thing to do is take a small amount of the cube material, go outside and see if it burns. Acoustic control material is almost always self extinguishing as building/fire codes require this. If it burns, you now know what NOT to do with it. Link to comment Share on other sites More sharing options...
Members rpjazzguitar Posted October 14, 2014 Author Members Share Posted October 14, 2014 If the bass amp isn't good enough, I could replace it with a powered speaker and put the piano through it too (it's an old Wurlitzer 200A? I imagine I'd get at least as much bass as I'm getting through the practice amp. Is that right? And, it would be better than the amplification I used for piano yesterday (a Roland JC55). And, if I need to amplify vocals at some point, I could do that too. BTW, as amateurish as this set-up might seem, the musicians involved were all long time pros, and nobody complained -- possibly because that would have meant that next time they'd have to hump their own gear in. Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 15, 2014 CMS Author Share Posted October 15, 2014 The bass amp is good enough, and the predicted mids are fine as you can hear them and discern notes more easily than the muddy lows. Comparing the amp against a powered speaker is difficult as I don't know what powered speaker, but it might have a bit more articulation. Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 19, 2014 Members Share Posted October 19, 2014 I'm happy to report back that the quilt display acoustic treatment worked great at yesterday's event. The room dimensions are approx. 50ft. x 50ft. with a 15 - 16ft. high ceiling... bare drywall walls and ceiling, concrete floor. We noticed a marked improvement in the room acoustics with just the first couple of quilts hung. The total quilt display we put up I'll estimate treated 2/3 of the wall surface and resulted in a "night and day" difference in the room acoustics. Also the visual of the quilt display went over really well with the crowd. I'll see if some pictures or video surface in the future of last evening's event... as a comparison as I've found a couple of youtube videos of bands playing the same room (untreated) with basically the same sound rig at the same annual event over the past couple years: Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 20, 2014 CMS Author Share Posted October 20, 2014 What a cool and unexpected collaboration, Mark. I'm glad it went well! Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 20, 2014 Members Share Posted October 20, 2014 Nice! Link to comment Share on other sites More sharing options...
Members RoadRanger Posted October 23, 2014 Members Share Posted October 23, 2014 Kind of interesting that the quilts are legal (because they were on sale?) whereas if you owned a bunch and hung them specifically for acoustical purposes you'd have the fire marshal all over you . Also kind of funny, one rehearsal space I play at has the walls entirely covered with real egg cartons (the molded paper pulp kind) - Woo ! Link to comment Share on other sites More sharing options...
CMS Author Craig Vecchione Posted October 23, 2014 CMS Author Share Posted October 23, 2014 Kind of interesting that the quilts are legal (because they were on sale?) whereas if you owned a bunch and hung them specifically for acoustical purposes you'd have the fire marshal all over you . Also kind of funny, one rehearsal space I play at has the walls entirely covered with real egg cartons (the molded paper pulp kind) - Woo ! Probably never visited by the fire marshall since the place opened. What's frightening is that it'll go on like that forever....nobody will say anything even if they know it's a potential problem. Then Mrs. O'Leary's cow tips the lamp... Link to comment Share on other sites More sharing options...
Members trevcda Posted October 25, 2014 Members Share Posted October 25, 2014 Probably dating myself but this is what I think of when I see egg crates on the wall: Link to comment Share on other sites More sharing options...
Members Audiopile Posted October 25, 2014 Members Share Posted October 25, 2014 Kind of interesting that the quilts are legal (because they were on sale?) whereas if you owned a bunch and hung them specifically for acoustical purposes you'd have the fire marshal all over you . That was taken into consideration... I believe due diligence was done. The quilts displayed were cotton and/or wool construction... to my understanding "fire retardant 100% cotton fabric and fire retardant 100% wool or cotton batting"... which, as I understand, is considerably more fire resistant than polyester or silk. Also, the venue was "no smoking" and "no fireworks" or anything of the sort... and approx. 200" of open egress for the 2500sq. ft. venue and a max of probably 50 occupants actually inside the venue at any one time. Link to comment Share on other sites More sharing options...
Members agedhorse Posted October 25, 2014 Members Share Posted October 25, 2014 Correct, different assembly types have different codes regarding flamability. Also, the AHJ has considerable flexibility in smaller gathering areas, as they do in larger sprinklered fire resistant construction types such as a convention center. It's not a black and white decision, there are many possible mitigating factors that CAN come into play. Link to comment Share on other sites More sharing options...
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