Problem Frequencies - Treating Tracking Room

phyl · Post by **phyl** » Thu Sep 01, 2005 7:17 am

Thanks to Knightfly and other for previous construction advice.

I'm ready to start planning some acoustic treatment for my tracking room. The attached drawing shows dimensions and approximate placement of doors and windows. One entry to the tracking room is not visible; it's directly underneath the HVAC ducting and connects the control room and live room. There are two doors there -one hollow core, one solid core - separated by about 6 inches. Ther are decoupled as much as possible.

Walls and ceiling will have two layers of sheetrock. The wall between the control room and tracking room is a double wall with approx. 3" of air gap between walls. I plan to use 3 pcf rockwool behind the sheetrock.

Now my question - I've plugged the room dimensions into the RoomTune and RoomModeCalculator spreadsheets, both of which I downloaded from this site. I'm a bit unsure about what to do with the results.

First off, for RoomTune, I think I understand how to interpret the results and have circled what I think are the freqs I need to worry about. Next, I plugged the room dimensions into RoomModeCalculator and got numbers for the axial standing waves. The freqs identified by RoomModeCalculator are different from the RoomTune freqs, but not by very much.

Based on what I've seen in previous posts, the idea is take the problem freqs and either build broadband absorbers or panel traps to mitigate their impact. I guess my question is, based on the results of the attached graphs -

(1) have I correctly identified the problem freqs?
(2) how many of them do I worry about?
(3) Does anyone have ideas for optimal placement of absorbers/traps in the room?
(4) I read the following thread with great interest and thought a similar approach might work for me. Comments?

LINK

Post by **sharward** » Thu Sep 01, 2005 3:55 pm

You need to resize your images -- they're about twice the allowed width.

phyl · Post by **phyl** » Thu Sep 01, 2005 10:11 pm

Sorry - They should be sized better now. All images are GIF files to keep the size down.

drfrankencopter · Post by **drfrankencopter** » Fri Sep 02, 2005 6:20 am

Your graph is hard to understand. What would make more sense, would be frequency on the X axis, and mode strength, or # of modes in a 1/3rd octave band on the Y axis.

Theres another mode calculator available (linked on this forum somewhere) that gives better results. I think it's called modecalc or something like that, its an Excel spreadsheet.

Cheers,

Kris

phyl · Post by **phyl** » Fri Sep 02, 2005 8:58 am

drfrankencopter wrote:Your graph is hard to understand. What would make more sense, would be frequency on the X axis, and mode strength, or # of modes in a 1/3rd octave band on the Y axis.

Theres another mode calculator available (linked on this forum somewhere) that gives better results. I think it's called modecalc or something like that, its an Excel spreadsheet.

Cheers,

Kris

I used spreadsheet programs from this site to create the graphs, I thought they'd be the ones most folks would be adept at interpreting.

drfrankencopter · Post by **drfrankencopter** » Fri Sep 02, 2005 9:14 am

Not sure about what other people use, but I like, and used the one called ModesV2 found on this site.

http://www.studiotips.com/tools/

Lots of details on it. Its a little challenging to get going on it at afirst, but you'll get the hang of it. Once done, post the bonello and mode distribution graphs.

See my thread here: http://www.johnlsayers.com/phpBB2/viewtopic.php?t=4152 about 1/2way through the first page I interpret my Bonello and mode graphs. May give you a good place to start.

Cheers,

Kris

phyl · Post by **phyl** » Fri Sep 02, 2005 11:19 am

Thanks Kris, I'll give that a try and post the results.

drfrankencopter · Post by **drfrankencopter** » Fri Sep 02, 2005 11:58 pm

Something to consider....since this is your tracking room, maybe you're better off not building anything just yet. Do your analyis, and see where the modes are, but get some instruments in there, and figure out where the 'sweet spots' are for modal reinforcement and the like.

A tracking room should not necessarily be designed with ruler flat frequency response, and 'perfect' modal response. In fact, given the rectangular floor plan I'll bet that your biggest problems with the tracking room will be early reflections. Consider building diffuser panels first, or maybe slat absorbers (which will have some diffusion and decent absorbtion).

What's your room height? If its under 10-11 feet, consider going completely absorbtive on the ceiling, it really tightens up the room by getting rid of that 5-10 ms slap echo from the ceiling.

Cheers,

Kris

phyl · Post by **phyl** » Sat Sep 03, 2005 12:01 am

When you say 'go completely absorbtive on the ceiling', do you mean simply putting up as much Rockwool or 703 as I can afford?

I had planned to put a bunch of 3pcf Rockwool on the ceiling, especially over the drums.

AVare · Post by **AVare** » Sat Sep 03, 2005 12:42 am

phyl wrote:When you say 'go completely absorbtive on the ceiling', do you mean simply putting up as much Rockwool or 703 as I can afford?

I had planned to put a bunch of 3pcf Rockwool on the ceiling, especially over the drums.

That is an excellent way of doing it.

For the side walls look at the various studios in the "..Under Comstruction" off the main page of teh site.

Yes you have identified the problem frequencies adequately.

Good luck, and as you go on in the designt he more specific the questions the better they can be answered. Good studio building is 90% design and 10% construction.

Andre

phyl · Post by **phyl** » Sat Sep 03, 2005 1:56 am

AVare wrote:
phyl wrote:When you say 'go completely absorbtive on the ceiling', do you mean simply putting up as much Rockwool or 703 as I can afford?

I had planned to put a bunch of 3pcf Rockwool on the ceiling, especially over the drums.
That is an excellent way of doing it.

For the side walls look at the various studios in the "..Under Comstruction" off the main page of teh site.

Yes you have identified the problem frequencies adequately.

Good luck, and as you go on in the designt he more specific the questions the better they can be answered. Good studio building is 90% design and 10% construction.

Andre

Thanks Andre.

I'm crawling through a bunch of 'under construction' threads at the moment. One thing I've noticed is that it's not necessary to apply the wall treatments symetrically, that is, if I put some sort of absorber or trap on one wall, I thought I had to do the same thing on the opposite wall.

I'll be working on a more accurate drawing of my room this weekend.

AVare · Post by **AVare** » Sat Sep 03, 2005 3:54 am

Good stuff and more good stuff posting your thought processes. Have a look at Joe Egan's studio for non-symmtery and variable acouastics in the space.

Andre

knightfly · Post by **knightfly** » Thu Sep 08, 2005 7:08 am

One thing I've noticed is that it's not necessary to apply the wall treatments symetrically, that is, if I put some sort of absorber or trap on one wall, I thought I had to do the same thing on the opposite wall.

Ideally you should do symmetry, in a control room. Not so in other rooms, for those you need to work in the room and learn its "G-spots" so to speak. No different than experimenting to find best mic position; this is, in fact, part of why there ARE "best mic positions" - it's all about locations/interactions/wavelengths, etc.

Advantage of NONsymmetry includes being able to pick your "sound" by placement of instruments/mics.

For best CR's tho, plane symmetry is the holy grail - if you can't get there full-time, sometimes portable absorbers can help during mixdowns... Steve

AVare · Post by **AVare** » Thu Sep 08, 2005 7:39 am

Steve:

Your last post has me somewhat confused. Not that that is hard to do...

The thread is about Phyl's tracking room, yet your post keeps refering to control rooms?

Confused again, or still;
Andre

drfrankencopter · Post by **drfrankencopter** » Thu Sep 08, 2005 9:25 am

Hi Avare,

I'm pretty sure Steve was just clarifying that in a control room symetry is a good thing, but isn't necessary (or even desired) for a tracking room...probabaly he was clarifying that jsut in case someone was applying the information from this thread to their control room design instead of just to a tracking room..

Cheers,

Kris