Morale buster or treating my unusual room

wmb · Post by **wmb** » Wed Jul 14, 2004 5:07 am

I am in the process of treating my room. I have been reading this site and others. Small rooms, big rooms and rooms with many features have been discussed but I have yet to conclude on my situation.

I have a larger room to work with. It's unusually shaped and is more like two intersecting rectangles with a sloped ceiling. (I will try to attach an image.) Trying to narrow down the dimensions that might be giving me problems is challenging. I am trying to figure out if the two shapes will contribute their problems to the other areas.

For instance, there is an area near the center of my room that is common between the two spaces that is approximately 8'x12'x11' that is a volume within demensions nearly 29'x34'x11'. If I am thinking correctly then this area would have modes of a room that size? Futhermore, the other two retangular areas would have modes of their own as well? I guess these modes would/could compound in the common area?

My desk is within the center area I mentioned above (pointing mostly into an accute corner). I have a peak at 114hz that is pretty extreme. I cannot remember the exact db but it's the only one that was unchanged after I put 2'x8'x 4" 703 absorbers in the six corners around the room.

My next tactic is to put an array of 703 absorbtion on the walls that have the 29 foot demension. I also have very heavy theater curtains that cover nearly half the walls in the room. I know this does little to stop bass but I am planning to put 2'x'4x4" 703 spaced every few feet behind it. I have a few 2'x'4'x4" panels I have been testing in wall/ceiling intersections but they have been for testing how this stuff works and have made no changes that I can observe in testing.

Am I correct about the compounding mode issue? Any suggestions?

Thanks, wm

knightfly · Post by **knightfly** » Wed Jul 14, 2004 1:51 pm

Can you modify your pic and show (as closely as possible) exactly where your desk, speakers, and head are placed? Also, are you aware that corners are major buildup places for modes? Most of the time, the first things to do would be to place 4' wide by 4" thick rigid fiberglass or rockwool across all the corners in the room, put more wherever you'd see your speakers if the wall were a mirror (use one, held by a helper) and hang more of the stuff over the mix position - having the desk facing into a corner is normally a big no-no, as you'd need to absorb so much of the room to avoid early reflections that it would become unnaturally dead. Sound fired into a square corner will come back exactly parallel to the entry angle, so side reflections take quite a bit more area treated to control it.

let me know where your desk/speakers/head are in the room, including height to floor and ceiling of ears and centers of woofers... Steve

wmb · Post by **wmb** » Wed Jul 14, 2004 9:50 pm

I'll see what I can do for measurements and editing the image. Would photos help? I have a very busy 24 hours ahead of me. That request might take awhile. I will just have to do this in paint or something. I don't have any graphic tools.

I was really afraid someone would say four footers for the corners. I went with 2'x8'x4" since realtraps are that wide. Oh well. Can I just move the 2 footers out a little more to hit more lows? Would I be doing more for myself to just make another six 2'x8's or continue with my plan to put 4" 703 on the walls.

I try to be pretty scientific by changing only one thing at a time. Currently I am going to finish making the panels that are mid way to completion. I have six more to cover. I have done this assembly line style so the gratification is slow. I am losing patience. I have been in the panel making business for the last two weeks and I am so tired of it. I cannot give up yet.

Tonight I did some experiments in measuring the peaks in the 114 hz range. At the mix position it read 91 db on my Radio Shack meter another 5 feet back it was something like 86 db and the peaks continued to decline every 5 feet or so until the wall where I measured the last peak. I guess this dimension is the cause for the peak?

Thanks, wm.

knightfly · Post by **knightfly** » Thu Jul 15, 2004 2:08 am

Actually, 4 footers of 4" 703 in all corners is one of the best starts you could make - I still need to know the orientation and location (to the nearest 2-3 inches) of you, speakers, and walls - no hurry, it's just that modal problems can be specific down to inches because you may be moving just out of one node/antinode and into another, possibly from a different pair of walls, etc -

So, when you get some time if you could measure accurately, then do a crude "pencil tool" add-in to your drawing in paint, and list exact dimensions (the drawing itself just needs to be close for visualization) - No rush, I seem to have enough going to keep boredom at bay

- even after you get the time, it's likely (partly because of the complexity of your space) to take me a while to get back too... Steve

wmb · Post by **wmb** » Thu Jul 15, 2004 5:58 am

I could expand to 4' pretty easily in four of the six corners. Would the two that were 2' be that much of a problem? They are diagonally aligned in the eastsoutheasternmost and westnorthwestern corners. That might be hard to visualize but it's the best I can do.

I still have nearly a full box left and have made enough 2'x4' and 2'x2' panels that I could improvise some more 2'x8's to test it out.

I have two albums to mix and a third is knocking on the door. I want to retire from the panel business for awhile.

Thanks, wm

wmb · Post by **wmb** » Fri Jul 16, 2004 11:46 am

Here is a rought sketch. The gray lines are the 703 I have installed. The yellow lines are the curtainsa I mentioned before.

Measurements will come later tonight.

Thanks, wm

Edit: I resized the enormous image to a more conservative size.

wmb · Post by **wmb** » Sat Jul 17, 2004 6:52 am

Steve,

Last night I used my studio to rehearse a band I play with. The room was wildly different from the last time we rehearsed (without any panels in place). Despite my inability to knock down the peak at 114 hz it sounded fantastic. Every instrument sounded tight and clear like it never had before.

I improvised on your suggestion of wider panels and used some smaller panels stacked next to my 2x8 panes in a few corners to make them 4x8. They didn't test any differently. I did not remove the additional improvised 2x8's during rehearsal to test for a change.

What I am wondering is if it would make more of a difference on the lower frequencies to have 8 inches of thickness rather than 4? This would be an easier solution for my situation. From what I have gathered from reading stuff on this site it sounds like thickness is a factor for the depth of absorbtion.

Thanks, wm

knightfly · Post by **knightfly** » Sat Jul 17, 2004 10:00 pm

Right - thicker, or even same thickness but further from the wall will absorb to lower frequencies - but even 8" from wall to the FRONT surface of absorbent won't make much differences at 114 - I'm hoping to find time to do a basic spreadsheet for figuring useful absorption based on distance from wall to face of absorber, hopefully in the next day or two.

Your 114 hZ looks like it might be a function of your 20 foot dimension, BTW -

Meantime, if there's any way you can get your desk position symmetrical with the room from left to right, (NOT in the other two dimensions) it will help imaging - however, facing into a corner will take quite a bit of wall treatment and a seriously heavy trap in that corner you're facing.

I've done a crude ray tracing of a square room with diagonal desk placement in CAD, haven't yet converted to web-friendly format; but basically, you need the front corner absorbed like crazy, extending a few feet to each side of the desk, with the desk sitting closer to the corner; then, the two walls to the rear need to be almost totally absorbed. This can seriously deaden a room, so height of the absorbers (and vertical positioning) needs to be tweaked.

Gotta go to work in a couple, more when I get the chance... Steve

wmb · Post by **wmb** » Sun Jul 18, 2004 11:55 am

knightfly wrote: Your 114 hZ looks like it might be a function of your 20 foot dimension, BTW -

Not sure which 20 feet you are talking about?

knightfly wrote: Meantime, if there's any way you can get your desk position symmetrical with the room from left to right, (NOT in the other two dimensions) it will help imaging - however, facing into a corner will take quite a bit of wall treatment and a seriously heavy trap in that corner you're facing.

A couple of things... Unfortunately I cannot move the desk very far from where it is currently. A little forward or backward but that's about it. The nearby room is where all the computer stuff lives and the cabling is a bit restrictive. It's not impossible but the current position works great for tracking and I am willing to work around the functionality it provides.

Which corner do you mean by "facing"; The one the speakers point at or the one I look at while facing the speakers in the mix position? I am thinking of building a pair of 8'x8'x4" bifolding baffles. I figure that closed they would provide massive low frequency absorbtion when placed in a corner and could be set up behind me opened when I'm mixing. I don't know how much the latter would be necessary but I figure it could help the imaging.

Thanks for all the thought you have given toward my cause. My goal is to improve the space as much as I can. I do realize the limitations of my tracking/mixing setup. I'm very hands on and this setting has gotten some great performances so far.

From what I can tell the spike in the untreated room was about -3db where the mean level was -14.5 (The average includes the spike in the sample) from the wave created from the sine wave test. I don't know if that would be considered 11.5 db or what. I don't know how bad that is comparitively. I know that 11.5 db of cut or boost on an eq is pretty extreme but the Q is tight.

After hearing that rehearsal I am sure that I am doing something good. I have invested much time and money in my place but the last $700 dollars was way more dramatic than my neve's. I'm sure they will sound better now.

Thanks, wm

Post by **John Sayers** » Sun Jul 18, 2004 8:19 pm

After hearing that rehearsal I am sure that I am doing something good. I have invested much time and money in my place but the last $700 dollars was way more dramatic than my neve's. I'm sure they will sound better now

now that's a good point isn't it

Couldn't help myself, reading this great thread and looking at your floorplan, from having my own idea of where you could go.

cheers
john

wmb · Post by **wmb** » Sun Aug 08, 2004 12:48 pm

I recently lost my internet connection for a couple of weeks so it's been awhile since I posted...

John,

Your layout is looks great! I had a similar thought in the beginning but the ceiling height in the area where you have the drums currently is only 9'. The control room is where the highest ceiling exists, 12'. It does look great though. If I buy the building I will open the ceiling in that area and build my apartment on the roof.

The bass trapping saga has continued with more 703 and I can start seeing individual frequency attenuation as I move traps. I have one big peak and one big dip that still get much of my attention but everything else is getting smoother.

As I have made more traps I can experiment more and have found one area in my room that seems to have the biggest problems. It's the corner right next to the " 31' " in my illustration. The more traps I put into the corner the better my tests come out. When I get some time I will make more traps for this area and put them in the ceiling/wall intersections.

Overall I have spent about $1200 US on my traps including hardware and fabric to cover them. They are rather beautiful looking as well as being functional. They look more like artistic expressions more than big fiberglass panels. It is by far the greatest bang for the buck experience I have had since I built my room. The first $700 was more audible than the last five but I'm getting used to it. Inversely the last five have made dramatic differences in my tests on the biggest problems.

I try not to get too religious about this kind of thing but now that I've experienced the difference of having my room treated verses untreated it's clear that this SHOULD have been one of my initial investments. I will encourage others to spend the time and money on this stuff because it will have a very broad impact on everything down the line.

Cheers, wb