Treating a rental rehearsal room 20'x20'x18'?

[Randyman...]

Thanks! I was thinking that 16" OC would give a stiffer wall and might prevent other resonances from sneaking in. If you think the effectiveness of the rigid wall would not be compromised with 24" OC studs, then I would prefer to go that route by all means. Does a 4x4 at the center stud sound like a silly idea? It seems that having the 2 walls meet at a single 2x4 is a bit too little, and there won't be ample room to squeeze two 2x4's (one for each wall). I'm thinking I'll use a 4x4 at the middle, and bevel it (cut 2 angles with a circular saw) and have it marry the 2 wall sections together nice and solid. Or I could use Two 2x4's perpendicular to the wall, and bevel them accordingly (that might be easier come to think of it). I'm not all up on building construction, so I'm just doing what I can envision in my head...

I could start the wall on the other side of the columns, but I was hoping to retain as much floor space as possible, and this allows an easier place to attach the side studs IMO (otherwise, the wall will be parallel to the surface I'm trying to attach the stud to). The actual inside wall will end up starting approx 6"-7" in from the existing wall as-is (2x4 Stud + 5/8" Drywall + studs will be inset ~2" from the existing wall), and end up protruding 2' 8" into the room. I'm assuming the further in I move it will result in spreading out the modes from the 19' walls vs the new wall (and end up with a smoother distribution of modes)? Will an extra ~6" of depth really make an audible difference with my dimensions? If I move the outsides inwards as you recommend, then I will need to move the apex inwards to retain the angles, too (eating up more floor space)...

I would be willing to go "Flush" with the columns - netting another ~2"-4" if you think that would have a beneficial effect on my modes...

I'll also consider the 1/3 + 2/3 idea, but as you know the longer I make either wall results in more wasted floor space at the apex of the wall. I figured a small offset plus the differing angles on each side of the wall would help - so I didn't go too crazy.

For sake's sake - If I *WAS* so inclined to build a second wall (and again retain as much floor space as possible) - where would you see a second 1/2 in 1/2 out splayed wall going? I'm thinking the bottom wall on the pic (the one with the door and mirror) might be a candidate (caddy corner to the proposed wall). This would eliminate my other set of parallel walls, and I'd only have the floor/ceiling parallel at that point - not to mention that would cover the stinking mirror, too! That is probably a bit more than I'm looking to do, but if the results would be that much better vs a single wall, then I might consider a 2nd wall as well...

Any input on a slat wall vs false wall in my room as xSpace was getting at? Should I frame it, stuff it, and measure it - or just go ahead and put up the stinking wall?

Rock and Roll!!!

[xSpace]

I'm no expert.


Documents I have read suggest that a 24 inch layout reduces the rigidity of the wall, so that is a good thing.

Reason I wouldn't (I wouldn't...your mileage may vary) break up the newly framed wall is because you introduce another angle. But like we know, you are just trying to get rid of a pair of parallel walls.

Pink fluffy insulation, the cheap stuff, is recommended all over this board, so I used it

As to me suggesting doing other things, slats or what have you, this is a direct result of me not being able to get in that room, not being able to put my ears in it and listen. It is only and solely based on my experience with the issues of a square room and hard surfaces, nothing more nothing less. No science.

You have to listen to your room while you do whatever it is that you decide to do and understand that the improvements are not going to take your breath away.

The key word is improvement

[Randyman...]

Nice input

24" OC it is, my friend! You saved me some cash AND labor

As far as the wall angles go - you mentioned I could get by with 6 degrees. If I'm willing to go 12 degrees, would you think I'd notice any perceivable improvement over a 6 degree angle? I will indeed apply your suggestion and listen to the room and RTA it before I hang the drywall (even if I might not be able to return the drywall ) - the placement of the wall, however, can not be changed so easily I'd assume the additional depth of a 12 degree wall would allow more (and lower frequency) absorption if left open or less objectionable reflections if drywall is applied?

And back to my floor/ceiling concerns - I already put some 1/2" Birch plywood under my drum kit (most of it is covered by the cloud above). I like what it did to the presence of my kit in combination with the cloud's effect on reflections - the snare especially. I might be willing to slap down more birch plywood to cover the entire floor and do a quasi dropped-ceiling with a mix of 2" and 4" 703 (basically a bunch of tightly packed cloud frames). Do you see any concerns with that - and further - could I position the dropped ceiling to a point that would help reduce my major 49-50Hz 0-0-1 mode?

I'll check back on this personal goldmine of information in a little while

[xSpace]

"... could I position the dropped ceiling to a point that would help reduce my major 49-50Hz 0-0-1 mode?"

Directly over the mic position you are trying to correct.

Stuart mentioned already, you have so much going on in this room, reflection and absorption, that the readings are different from one place to the next. And this is why there is no simple cure-all. If you had an acoustics technician there, this person might have simply said "Rip it all down then let's read the room and make changes according to how the room responds."

When you eliminate the one set of Fundamental 29.73, 1st 59.47, 2nd 89.21 and 3rd 118.94 being produced by the walls, you at least take that reinforcement out of the picture. Problem is, they still exist due to the other parallel pair. So you still have them to deal with

The ceiling height modes are running hot and cold, depending on where in the room you are. Again, what ever you have on the walls and on the floor and over your head at that point are either supporting or creating an acoustic hole.

We might even find that the speaker and mic you are using are influencing these figures...the speaker may not be giving the same reproduction, depending on what surface it is on, if it is being damped or reinforced in some manner by the materials of the room

This sure is fun

[Randyman...]

This sure is fun

You're telling me ! I'm such a noob

So, with your last post, are you still thinking framing the wall as I posted will be worth my time and money (either way - left open or covered with drywall)?

I'm sure the stuff that was in the room has at least some influence on the RTA plots. The Mirror covered with a blanket, the plastic on the walls, the plexiglass drum gobo partially covered with blankets, the clouds at different heights from the concrete ceiling, the drums in the room resonating, etc. I use a Mackie HR824 and a DBX RTA mic (from the Driverack PA processor), and ATRA software to measure. The speaker was placed at a wall/wall/floor corner as tightly as I could wedge it in there (adjacent to the door). The other RTA plots that say "Speaker high" had the speaker approx 2' from the ceiling at a wall/wall/ceiling corner and approx 8" away from the wall (close to the PA Stack/Bass Area in my first post).

Here is what I'm envisioning: I'd like to end up with a cheap plywood floor controlled by numerous clouds (cloud height is sill unknown, a mix of 2" & 4" OC703). The new wall (if I decide to hang the drywall after I frame and stuff the cavity) will be somewhat reflective and will have some broadband absorbers to help reflections. I might also cover the mirrored wall with drywall (not change the dimensions), and also treat that with broadband panels accordingly. Then, the front wall by my drum area will retain the 2" pyramid-type foam across 90% of it (the area close to the ceiling is exposed brick/mason, but the lower 9' of the front wall is covered with the 2" pyramid foam), and then I'll probably leave the thin 1" foam on the last wall with the plastic covering, and suppliment with more absorbtion as needed (might consider ripping that down as well and exposing the mason wall behind - but again reflection city!). The corners will get a good dose of super chunks.

I realize ripping everything down and starting fresh might be advisable, but that would result in much more work up front, and more investment - and likely result in leaving the room in an unusable state for a week or 2 (we will still be rehearsing in the room during this feat! - Like pulling the tablecloth from under the dinner set!). I'll be doing one or 2 sections of this project per week until I'm "done".

Does my vision above sound like it has ANY promise in improving the mess I'm currently dealing with? I will indeed take it as it comes and "listen" at each step as long as this seems like it has any hope for success...

Since I'm pondering covering the mirrored wall with drywall (the mirror is glued to a sheet of particle board that seems to be attached to the drywall with liquid nails! I'll have to cover it as I can't seem to be able to remove it easily), making a second angled wall at 6 degrees *MIGHT* be an option, but I'd need to be judicious with eating up floor space. Would you see any benefit in that - or will simply eliminating parallel walls w/o drastically changing my dimensions be pointless at this juncture?

This is a TINY project compared to other designs I've seen around here - and it is amazing how uncertain all of this ends up when the starting point is so bad (and partially unknown), and a small budget is involved Oh well - I'm not expecting miracles, just a halfway descent sounding room to jam and record in w/o breaking the bank. Obviously not as easy as it sounds when you're starting where I am

Thanks for putting up with all of my crap!!!!

[Randyman...]

Quick update (to myslef ) - After a few different vehicle issues this week (I'm a moron!), I'm hoping to get my truck back on Friday Afternoon and head straight to Lowes or Home Depot to pick up the Studs, Drywall, and pink insulation for stuffing the wall. I'll also have to rent one of those sweet nail guns that use blanks to shoot the nails into the concrete! If I don't get my truck back on Friday, this will have to wait until next weekend as my time is very limited, and 12' drywall and 12' studs won't be cramming into a Corolla .

I'll keep you posted on my progress. My plan still sits as it was barfed out above, but I will INDEED take time to stop and smell (and listen to) the roses after each step of the project. We are having Band Rehearsal on Sunday - so I'm hoping to get the wall framed and stuffed on Saturday, and likely have band rehearsal with the wall left "open" and see what transpires in the room and on the recording. I'll probably run some more RTA plots as well (I might use my Dynaudio AIR15's this time to see if that makes any difference). I'm anticipating a small improvement in the low-end, and a deader sound since I'll be covering one of the existing plastic walls with a good dose of pink stuff - so I'm leaning towards the fact that I will likely be putting up the drywall and treating it w/broadband absorbers afterall - but my ears will be the judge. I want to clean up the modes and parallel reflections w/o killing the "air" in the room, and I forsee a ~18' x 11' wall of pink stuff taking a lot of air with it...

If you see any show-stoppers with the initial wall plan I'd be greatful for any objections before I purchase the materials and start framing that crap like only a drummer can (it should be interesting!)

[Soundman2020]

Randy, I hope this post is in time to catch you at some point between the "truck trip to Home Depot" stage and the "shooting nails into the floor" stage!

There's an interesting discussion going in in another thread ( http://www.johnlsayers.com/phpBB2/viewt ... 888#p99888 ) with comments from some highly respected big names in the acoustics industry, about what wall angles are needed for dealing with flutter echo and reflection free zones. It turns that you can probably get away with a minimum 5 degree angle for dealing with flutter. So you might be able to re-work your plan and gain back a bit of floor space, if flutter is your only issue. Having said that, flutter is NOT your only problem in this case. You have flutter in the VERTICAL plane for sure (wall-floor), so if you do angle your cloud tops then those should be at least 5 degrees, but your wall is for a different purpose (trying to change room dimensions slightly to get away from square, and also muddling the modes a bit), so I'd suggest that you leave your wall plan way it is.

Just wanted to make sure you have all the best info before you start attacking innocent 2x4's with a dangerous weapon!

- Stuart -

[Randyman...]

Cool - I'll plan on keeping my first wall the way it is - and I'm going to make it flush with the columns to get slightly more deviation from the original square dimensions (that is IF I decide to hang drywall on the stuffed frame).

I might consider doing a second wall at 5 degrees (in/out like the first wall) when I cover the mirrored wall since eating up more floor space is not much of an option for a second wall. I'll get this first wall done before I seriously consider the second wall...

Quick Q - I plan on building the awesome Gobo listed in this forum (the one that has 1/2 reflective slat wall side, and a "dead" side). That Gobo will be placed where the plexiglas drum shield is currently located and slightly break up the flutter from the 2 existing parallel walls (reference my first post's picture). Would having a substantial gobo like that between the 2 parallel walls slightly negate the benefits of angling the mirrored wall to kill flutter? It seems like the gobo would still be affecting lots of the flutter from those 2 parallel walls (at least the lower height area of the room) - and the drum sound would be mainly encountering the "slat wall" side of the gobo - so the fact that the mirrored wall was changed to 5 degrees might not be worth my time. Thoughts?

My truck should be ready by 5PM - so this might begin to take shape tonight!

[xSpace]

If you are going to build a wall anyway, why not determine based on your existing floor to ceiling height and one wall length what would be a good room ratio to establish a rectangular room that gets you right inside the good ball park rather then trying to put a band-aid on what amounts to an acoustic hemorrhage?

You just might be surprised to find that you can do this without any special training?

[Randyman...]

...rather then trying to put a band-aid on what amounts to an acoustic hemorrhage?

You know how I feel, then

I would LOVE to get a nice golden ratio room. So, if I loosely go by 3-4-5, my longest wall is 19', my shortest dimension is height at 11'5", I get a rough multiplier of 3.8 (length to height is already a descent ratio!). So the "4" wall in the 3-4-5 would be approx 15'3". Does that sound loosely correct? I know there are other "golden ratios" - but I'm not all that familiar with them. Is there another ratio that would allow me to keep more floor space? And will cloud placement have any effect on the height calculation (I'd assume not since we are speaking of the rigid boundaries of the room - correct?)

Reducing the floor plan from 19'x19' to 19'x15'3" would probably kill a bit too much floor space IMO (4'3" x 19' = approx 80 Square Feet of floor plan lost to the wind) - and while the owner did mention he was cool with me doing stuff, reducing the size of the room that much (w/o any splaying to conserve floor space) would probably not be cool with him. He generally charges rent by the size of the room for all of the other rooms at this facility - and I'm not sure that most potential future renters (musicians) could appreciate the dimensional change as "added value" when the room is actually a good deal smaller than a neighboring room with the same rental fees. I guess we could go back to planning on ripping the wall out and restoring the original wall when we vacate the premises...

Edit - What about a compromise of a 12 degree in/out wall, but have the apex peak out at the 15' dimension (so the apex will be 4' from the original wall opposed to 2'8" from the original wall as previously anticipated), and have it fold back at that 12-15 degree angle to save some room in the corners?

OK - Another silly idea - if I did go with a deeper false wall - could I fore go the insulation, put a cheaper door in there and utilize the wasted space for storage? I know "appropriate" soundproof doors and associated installation are pricey - and I won't be able to invest that much on a door. The leakage would probably negate some of the benefits of the dimensional change - ya think? If this is a possibility - then I can *probably* make a 15' false wall work...

I'd also quickly add that while I would LOVE to kill my major room modes, I'm thinking the overall timbre of the room in the low-mids through highs will still be VERY important. And I'd also like to keep the room as lively as possible while eliminating flutter echo. What kind of trade-offs will sacrificing more floor space with another PARALLEL wall versus my original plan of the splayed wall end up with? I know this is likely next to impossible to determine online, but if sacrificing all of that floor space just to kill a few major modes still means I have to cover the walls with tons of absorption to kill flutter, then I'll likely be sucking all of the air out of the room, no (but the low-end will be tight, correct)?

Any thoughts? I'm learning a lot here - and I'm getting dangerous

[Soundman2020]

You know, I was about to suggest the same idea as Brien!

( You know the saying, right? "Great minds think alike"!!! )

Anyway, the closest ratio I found by fiddling with the numbers for a few minutes is:
Length=14.5 ft, Width=18.25 ft, Height=11.5 ft That works out to a ratio of 1 : 1.26 : 1.58, which is one of C.P. Boner´s good rations, according to Bob Gold's calculator. It's still not a fantastic ration, but it IS in the ball-park, and is on the charts that Eric Desart prepared so carefully over at Studiotips. I reckon it should work. (It is also a bit better than the classic "golden rule" ratio, according to Eric).

Being a bit more drastic:
Length=13.83 ft, Width=17.25 ft, Height=11.5 ft. Room Ratio: 1 : 1.2 : 1.5 That is Louden's 5th best ratio, which is pretty decent already.

But both of the above involve taking fairly large slices of TWO of your walls...

FWIW

- Stuart -

[Soundman2020]

A bit of clarification:

I'd also quickly add that while I would LOVE to kill my major room modes,

You cannot kill them! They will always be there. Changing the ratio of the room just spreads them out more evenly, which is a Very Good Thing, but it does not kill them.

I'm thinking the overall timbre of the room in the low-mids through highs will still be VERY important.

That won't change much by changing the ratio. Timbre depends on other things too, like absorption, diffusion, diffraction, refraction, etc.

And I'd also like to keep the room as lively as possible while eliminating flutter echo.

"Live" relates mostly to reflective surfaces. "Flutter" to parallel surfaces. So neither angling walls nor building fake walls will change the "liveliness" very much, unless you also add treatment to the new walls. In fact, your room will probably be even LIVER with the new walls, since you will be covering up that foam, plastic and egg crate "treatment" that you have right now. That stuff is most likely doing SOME absorbing, and some diffusing, but only God knows what frequencies and magnitudes it is accomplishing! So covering that up will REMOVE absorption and diffusion from the room, making it more "live".

...but if sacrificing all of that floor space just to kill a few major modes still means I have to cover the walls with tons of absorption to kill flutter, then I'll likely be sucking all of the air out of the room, no (but the low-end will be tight, correct)?

Once again, neither angled nor moved walls will "kill" modes. It will merely move them around, even them out, and change the relationship between modes. The modes will still be there, but they will no longer be reinforcing each other, overlapping, and playing havoc with the sound. For example, you will ALWAYS have a 1,0,0 mode, and also a 0,1,0 mode, and a 1,1,0 mode. The only question is, where are they in relationship to each other? Are the reinforcing each other (which is what they are doing right now), or are they playing nicely together, in different parts of the spectrum? (which is what the would be doing if you move the wall).

Don't know if that makes things clearer or murkier!

- Stuart -

[Randyman...]

Makes sense - I do kind of understand that the even distribution of modes is the key - I incorrectly used "killing modes" in place of "re-distributing overlapping modes".

So, as far as being "in between" any of those ratios - I'm assuming that 19' x ~15' (false wall) x 11'5" would still distribute my modes much more evenly than they are now? If I'm doing a ~15' false wall, that will be all of the floor space I'm willing to sacrifice (no second wall).

And what about the fact that I'm back to having 3 pairs of parallel surfaces with this suggestion? Would it not be better to average out the false wall's dimension at a 5-6 degree angle to scatter the flutter from one set of walls? Doesn't angling the walls reduce flutter - resulting in less absorption needed to kill the parallel flutter (likely resulting in a livelier room w/o excessive flutter)? I must be confused on the concept of angling walls to re-direct flutter (no longer flutter at this point) and lessening the need for absorption to eradicate the reflection all together. Otherwords - Re-directing the parallel reflection but not absorbing it (splayed wall) vs simply absorbing the reflection (parallel wall).


What about the prospect of leaving the wall un-stuffed and installing a cheaper door for storage? TBH - that is about the only way I see that proposition working...

I'm thinking that creating a storage area in the false wall will end up costing too much with a good door tossed in. My rough estimate for the initial wall was ~$300 painted and done. I could see adding $100 for a door, but that's about my limit ATM (stupid car/truck problems ). Thoughts?

I also have other "wall attachment" issues to consider as there are apparently some windows covered with plywood behind the foam on the front wall (don't have dimensions or placement as I had no intention of going that far into the room - and they are covered with foam), and the opposing wall has the mirror which is glued to particle board glued to drywall. PS - I found out the right and bottom walls in my diagrams were drywall - the top and left walls in my diagrams are the brick/mason outer structure of the building). So, sticking with attaching the wall to the columns seems to be extremely easy by comparison...


And again - since I know most of this stuff will not be "Wowing" me or knocking my socks off with regard to the sound of the room before/after - I have to keep the relative acoustic improvements in mind to keep the cost and wasted floor space reasonable for the scope of this project (I'm not big time ).



If I wanted to loosely estimate the effect of my proposed splayed wall on the modes - how could I do that? Would I average out the splayed dimensions and plug them into a box-type room mode calculator? I'd guess I'll be at 19' x 17'2" (averaged dimension) x 11'5". Regardless - I will take down ALL of the plastic crap and expose the walls - then I'll treat accordingly to kill flutter yet retain air...

[AVare]

Regarding room ratios, use one that meets the EBU/ITU/Walker equations. Or one that matches one of Cox's ratios for rooms.

There are no perfect ratios, or even "golden" acoustically. Just better and worse and terrible. Terrible being with two or three identical dimensions.

Andre

[Randyman...]

I know it is hard to hypothesize on this kind of stuff, but seeing the room is currently 19'x19'x11'5" (horrible), how drastic would the differences be from building my 1/2 and 1/2 splayed wall (starting at approx 10" in the corners are reaching an apex of approx 3' into the room) versus eating up all of that extra floor space for a straight-across ~15' false wall?

The way I'm rationalizing this is: The difference from my current state of "Terrible" to "Better" (with my splayed wall proposition) is a pretty big jump. Is going from "Terrible" to "Even Better" (with a ~15' false wall) going to be drastically different from "Horrible" to "Better" (with a splayed wall)? Will this one change be worth loosing the floorspace in a rental rehearsal room? I'm really trying to keep this in perspective for the scope of this rental rehearsal room project (floor space is a good thing)... I also have the wall-attachment concerns I mentioned above (the vertical columns are VERY appealing as attachment points!!!!!)

And if I go with a ~15' false wall, will using the dead space in the false wall for storage be a horrible idea? The inside corners and maybe up higher in the wall would still have some insulation - but most of the cavity would be used for storage - and a cheap pre-hung door would be required for access (likely the one show stopper right there, huh?).

I'd like to get the materials purchased today - and I likely will. The differences in materials will only be adding a door and loosing some of the insulation in either scenario. I'll plan on buying the insulation and make sure I can return it to purchase a pre-hung door if that ends up being a valid option...

I should be picking up my truck shortly - I'll stop back home and check in here before I stop by Home Depot or Lowes...

Thanks!