Problem Frequencies - Treating Tracking Room

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

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

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

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

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.

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

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

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

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.

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

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.

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

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

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

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

Yup; sorry if I confused things. Kris is right, seems like quite a few people have a hard time with the fact that different rooms, different purposes, different acoustic needs. I'll be more succinct in future; lemme practice a bit - Yup. Nope. Probably. Maybe. Depends. Not sure. That'll work. OK, think I got it now - man, this is gonna save me a CRAPload of time... :wink: Sorry, Andre, just funnin' witcha, I get in these moods when deprived of enough sleep :shock: (man, those new Titanium Toothpicks really work - look, you can even see my eyes in that last shot)

Kris and Steve: Thanks and thanks. When I wrote my post regarding symmetry I was going to elaborate in control vs tracking and decided against it in order to avaoid confusing people who complete threads, figuring if someone wasn't clearly understanding the thread they would ask. So keeping ti succinct: Thanks; Good; Not always; IT depends; Andre

Alrighty then. I've measured the room more accurately and included a detailed drawing. Ceiling hieght is 7'8", except under HVAC ducting where it's 6'10". I've also plugged the dimesions into ModesV2 and RoomTune. See attached graphs. After reading the recommended sections of this site and reviewing several studios in construction, I think it makes sense that I proceed as follows: 1) Determine type and ideal placement of acoustic treatment 2) Test room to see if emperical results agree with attached graphs 3) Install acoustic treatment The drawing of the tracking room shows my guess at all the possible locations for slat resonators (triangles) and panel absorbers (rectangles). I understand I may not need treatment at every location. My questions at this point: 1) I perceive my main problem areas to be at ~80Hz (panel absorbers), ~113 Hz (slat resonator), ~150 Hz (slat resonator), and ~225 Hz (slat resonator). Did I miss any other areas? 2) I plan to put the drums along one of the short walls (as shown) with an acoustic cloud above them. Given this location, what's the optimal placement for the panel absorbers and slat resonators? 3) The studio is in a basement. Will the fact that two of the tracking room walls have concrete behind them affect where the acoustic treatment should go? My brain hurts.

Hopefully no one will shoot me for bumping this thread since it's been dormant for 9 days. If I'm not being patient enough, someone please let me know. I need some help with the questions in my last post before I continue with the project. I'm looking for advice on where to place the traps in my tracking room, and also need some help determining which of the freqs I identified are worth treating.

Phyl, > I'm looking for advice on where to place the traps in my tracking room < Bass traps work best in corners. If you fill all the corners - including the wall-ceiling corners - and still have bass problems, then you can consider even more traps flat on the walls. > need some help determining which of the freqs I identified are worth treating. < Best is to absorb all bass frequencies, not just those predicted by a mode calculation program. --Ethan

Thanks for replying Ethan. I'm wondering if a combination of panel traps and helmholtz resonators might work better than just a shotgun approach with panel absorbers. I'm also interested in the optimum placement for the helmholtz resonators given the location of the drums. Finally, I was hoping the resonators could be used to break up the room symmetry. The final decision will be made after recording test tones at various locations in the room.

I'm also interested in the optimum placement for the helmholtz resonators given the location of the drums

What do you define as optimum? Be clearer. What is the optimum shade of red? You get the idea. Andre

Here's my logic. The drum's energy is predominately in the lower portion of the frequency spectrum. The frequencies I've identified that may require treatment also reside in the lower portion of the spectrum. Given that i'll be micing the drums it makes sense to place the acoustic treatment such that a 'sweet spot' exists around the drums, i.e., no localized nodes, ringing, etc. It seems as though this issue has been addressed for other studio threads on this board, that's why I bring it up here. ...or I could be completely full of shite....

Phyl, > I'm wondering if a combination of panel traps and helmholtz resonators might work better than just a shotgun approach with panel absorbers. < Broadband absorption is not a "shotgun approach." All rooms have peaks and nulls at all low frequencies, not just frequencies related to the room dimensions. See THIS article I wrote for Electronic Musician magazine that explains the principles in more detail. --Ethan

phyl wrote:

Here's my logic. The drum's energy is predominately in the lower portion of the frequency spectrum. The frequencies I've identified that may require treatment also reside in the lower portion of the spectrum. Given that i'll be micing the drums it makes sense to place the acoustic treatment such that a 'sweet spot' exists around the drums, i.e., no localized nodes, ringing, etc. It seems as though this issue has been addressed for other studio threads on this board, that's why I bring it up here. ...or I could be completely full of shite....

The last line is close to the truth. There is no "optimum", "sweet spot" "perfect sound" etc for generic drums. Look at and study the studios in the "studios under conscturction" section. You want help, we will help you. You mention othere studio threads regarding drum. Use the search function. We gladly help those who willing to help themselves. IF you want spponfeeding, teh going rate is 120$/hr (US) the last I checked. :) Ethan has been doing a great job TRYING to help you. You counter help with poor communication and obstructions, and no one will help you. Andre