There is a formula that is available on-line to enter your room dimensions to calculate standing waves.

Sounds like you have the basics down. You may want to see what the formula says for different monitor placement options for your room size.

I can just picture in my head what would be going on if you placed them the long way. You really will need to get something on those walls for absorbers. The bass traps are a good start for the low end.

DH, here's a link to the Excel spreadsheet I wrote about 12 years ago - it's one of the two mentioned at homerecording.com - go to this page, download roomtune from the "other application" section.

http://www.prorec.com/prorec/downloads.nsf/category

There are some basic directions included in the self-extracting file, if you need more I can help.

With no more than 15' front-to-back, you'll need some diffusion on the rear wall or you'll have smearing from too-early returns off the rear wall. Ideally you want at least 20 milliseconds between the direct sound and any reflections, which translates to about 19 feet round trip from your head to the rear wall and back. You might want to consider rotating the mix desk so that you face the long way in the room if possible. Symmetry around the mix position is also important. Any place you can put a mirror and see either speaker from the mix position, should have absorption such as Auralex or homemade fiberglass absorbers to control early reflections. Parallel walls should be treated with absorption/diffusion panels to eliminate flutter echoes. You can tell if this is REALLY bad by standing at the mix position and sharply clapping your hands. If you hear a boing, like you are in a rain barrel, you need a LOT of help. Even if you don't hear anything, if the walls are parallel it is there. In a small room flutter echo can easily be masked by happening too soon after the hand clap to be differentiated by your ears.

I know what you mean about the confusion factor, I've been studying this stuff for about 14 years off and on, ever since I built a room thinking I knew what I was doing - I still don't know, but I know more of what I don't know so I guess that's a step in the right direction.

John Sayer, who hangs out at homerecording.com, has a lot of really useful info on this subject - here is a link to a basic bedroom redo -

http://www.locall.aunz.com/~johnsay/HR/index1.htm

and here is a link to his SAE site, where I've learned a lot

http://www.saecollege.de/reference_material/index.html

click on everything there, plan to spend several hours. John has DONE it, while my info is about 90% study.

When you're even more confused, post back and I'll try to help sort it out for you... Steve

Calculating the standing wave is great if your going to build a room from scratch but your dealing with a pre existing space. I don't think it will be of much help. It never hurts to know where you stand but what you want is to make your space usable. You didn't mention how high the ceiling was but if it's less than 9' (very typical in a basement) your going to have trouble with bass modes. Assuming the ceiling is of appropriate height , the safest way to approach this is to do a LEDE (live end, dead end) set up. Start with absorption on the front wall.
1. Run a 2 foot wide line of 2" foam along the ceiling where it meets all the walls.
2. Completely cover the front wall with foam at least 2" thick (except where your mounting the bass traps in step 3, ). Also the side walls and ceiling up to where you sit at the listening position. You may leave the bottom 2 or 3 feet of the wall untreated. (This is the dead end)
The goal here is to insure that all you are hearing at the listening position is direct sound from your monitors.
3. Get some bass traps for the front and rear of the room. You need both the corner types like Auralex Lenrds and also something like the Auralex Venus Bass traps. These work on different frequencies and you will need both, especially in a low ceiling room. You may also consider something like the ASC tube traps. (If you have the funds ASC will do a computer plot of the room and provide you with all the correct treatments.)
4. Diffuse the rear wall. This is most important. Do not try to substitute absorption in this area. It will absorb to much sound, forcing you to run your monitor system too loud, screwing up your bass and treble reference. It will also deaden the room too much and cause you use more reverb / ambience than necessary. You may also want to add some diffusion on the side walls in the back half of the room (past where you installed the foam) and on the cieling above / behind the listening position. Diffusion is good but expensive. Use as much as you can. It is almost impossible to diffuse a room too much.
5. Symmetry in the set up is critical except on the side walls. You should try to have absorption and diffusion / reflective and dead surfaces opposing each other on this portion of the room.
6. After you do all this fire up some test tones and read the room with a spl meter and see what you've got. Pay particular attention to the frequencies below 300 HZ. That's where your going to get your bass modes. These will show up as spikes and nulls in the response, reinforcing and cancelling out making it impossible to tell what is going on with the low end. If the response is too uneven you will need to add more bass trapping until you achieve a reasonable room response. That should at least get you started. If you need any more help you can send me a private message and I will try to assist you any way I can. Fats
--------------------------------------------
"Everyone thinks they're Stevie Wonder"

Whoa CF Fats...great message...thanks! One thing that was not clear was the basss traps...how can I use the LENRD and the Venus traps at the same time? One above the other? I think they are standard at 2 foot lengths. Do I go for the middle of the corner, or floor to ceiling with the bass traps?

Also, that is a ton of covering for the back wall and the side walls. Remember that my room is approx 35 feet wide!

If this is the *ideal* situation, what is the absolute *minimum* that I could get by with?

The other option might be to move the setup to the short wall, but that is a bit impractical at the moment the way things are set up. It would screw up the rest of the room design, I have a great space at one end that is used as a vocal booth (not fully enclosed, so it is not *really* a complete booth), and then there is a "sound proofed" closet for guitar amps. (The room is not an exact rectangle.

It is difficult to explain, and this forum is not the place to get into too many details, but just curious if there is a way to get some help with minimum coverage...the entire back wall and sides is just a huge, huge area, and would cost me an absolute fortune.

Doublehelix,
Absolute minimums:
1. 2' x 4' foam on the ceiling where the wall meets the ceiling, the whole room. Mount the foam so you have a 2' wide strip on the ceiling. When treating rooms with foam products, you should always do at least this.
2. Place 2 Lenrd style bass traps in each corner of the room. 2 to 4 Venus style Bass traps on the wall behind each of your main speakers.
3. Diffuse the rear wall behind the listening position.
4. 2 Venus bass traps on rear wall at each corner next to corner/ lenrds.
5. Hang some type of soft absorbtive matierial on the side walls to the point that you sit to listen / work. Area rugs , drapes, moving blankets, anything like that.
That's still a lot of treatments but it is what is needed. If this isn't enough to get a good result start adding stuff from the first list I gave you until you reach somthing that works.

Lenrds are a foam corner bass trap designed to fit in the corner of a room and venus bass traps are square / rectangular thick pieces of foam designed to mount on flat surfaces. Each type of trap works on different frequencies and it is important to use both types to achive desired results. You can go to auralex.com to check out these products. Auralex makes a great product but other companies manufacture these type of products as well and I am in no way specifiying or recomending these products. You can do a search on the web for acoustical sound treatments and perhaps find a less expensive source. I would still recomend the first list of things I gave you but this may be a way to at least get started with treating your room. You never said how high the ceiling is but if it's less than 9' DON'T cheap out.
Let me know how it turns out. Fats

Hey Fats...I really appreciate the time you have taken, I will get to work, and will let you know how things go...You posts have really helped, I was getting so frustrated reading all these really confusing articles...I have ended up doing *nothing*! Now at least I have a plan. Thanks again! I should have this done within a couple of weeks.

First off, sorry I was confused on the bass traps, I thought they were *both* corner treatments (Venus and LENRD).

Secondly, the ceiling is at 8 feet...so yes, it is less than 9 feet, and will require the extra work.

I do have an Auralex catalog (and obviously their web address), but have also seen other ads in magazines, and will certainly search online. Even with the minimum treatments you suggest, it will not be cheap.

DH,
From what I can figure it's about 2 to 3 grand to do a full blown LEDE set up in your room. I'm glad to hear that you cieling is at least 8 feet. I saw a basment studio the other day that had a 6'2'' cieling! I couldn't believe it! You can check Marker Tech, they have foam and products that are less expensive than the other we were disscussing. Look around, you may find someone local that can give you a deal. This is a lot of dough and don't forget that this foam doesn't last forever. In time it will degrade and crumble / rot. BUt if you want to make your studio accurate this is what is needed. Good luck and please keep me posted....Fats

Hey DH, there are other options than giving all of your money to Auralex (and others). A lot of your problem can be addressed with sound absorbers of your own building. Most of the frequencies above 125hz can be absorbed by 4" of Ownens-Corning 703 rigid fiberglass in wood frames covered in burlap. You can use the same materials to make bass traps.

The room mode calculator that knighfly sent you to can tell you where you will have mode problems. You can make absorbers that will specifically target the frequencies, in addition to the normal bass trapping that you would use for a room.

The best purchase I ever made was a book called

Master Handbook of Acoustics
http://www.amazon.c…

It details a lot of these things. It shows how all of these devices are built, so you don't need to purchase them.

Another link that knightfly already gave you is the one to John Sayer's site. He has absorber construction details too.

Eric

DH,
Eric is correct in what he says about ridged fiberglass although it can be difficult to find in the retail market. The only thing about building traps and absorbers is you need to be sure the calculations and sizes are correct so you get your target frequencies. The foam products however are a kind of sledgehammer or one size fits all solution. Pick the approach that best suits you and go for it! Fats

DH, I just ran your dimensions in my sheet and another more involved one from Studiotips.com, and you will most likely have some really low bass modes, around 20-25 hZ. You also have coincident modes at 113, 133, 188, 201,235,240,283 and 304. these freq's would be more accentuated in that room, so would be good places to tune any DIY absorbers you made.

With that many coincident modal frequencies, Auralex or other foam could get quite expensive since lower freqs require thicker (4" or more) foam for any appreciable absorption.

Fats is right about the difficulty of finding rigid fiberglass such as Owens Corning 703

I really think rotating your mix setup 90 degrees and keeping it near one end, if that's possible, would help rear diffusion needs. that would give you more delay between direct and rear reflections and should cut down on the need for as much diffusion. Also, a cheap alternative for the diffusion you DO need could be a couple of large book cases (with books) at the rear of the room, arranged symmetrically either side of the median plane (a plane equidistant between the left/right speakers, passing thru your head when at the mix position) You'll understand my comments here when you price commercial diffusors such as AbFusors, QRD's, etc - Talk about getting paid for your ideas... Also, read carefully anything you find on "Poly's" they could help your room quite a bit. Happy reading, hope your eyes are good and your chair is comfy... Steve

Here's a quick update...

1) I have rearranged the room so that I am facing the "short" end of the room (which has caused other problems, but we won't go there...). This change makes it easier to cover the back, since it is *much* smaller!

2) So far, I have covered the back wall behind the desk and monitors, and have LENRD traps in the corners...

Wow!!! What a difference!!! :D The sound just seems to jump out at me now! I never really thought the room was *that* bad, but now I am convinced that there were definite problems!!!

Thanks to all for your help...I have a few more pieces to add until complete, but I am making *huge* progress!!!

DH,
I found another source for acoustic foam, Markertek.com .....Check them out, they have everything! Cables, foam, mics, cases,everything..I calculated the cost to do my room the way I suggested you do yours,... $500!
At that price maybe you can flip the room around the other way again (that's the way I would set it up). Use the 4" blade tiles as bass traps. These are the same exact thing as the Venus Bass traps only they are cut into 16"x16" tiles. Markertek also has the corner bass traps at $20 each. Once again you will need both types of traps to cover the area between 20 Hz to 300 Hz. Finish off the wall behind the speakers and the ceilings with the 3" foam. It comes in 54"x54" sheets so this will aid in an easier set up. You will still need to get your diffusion products from Auralex but at least you can save a bundel on the foam.....Sorry I didn't get this resource to you sooner.............. Fats

Yo Fats...Thanks for the link, I will check them out. I have already been there looking at cable and connectors. I will check out their acoustic foam.

The foam that I have already put up is 2", *not* 3", so I am not sure if I will have to replace what I have (I sure as hell hope not), add more 2" to keep it consistant, or switch mid-stream to 3"?

Thanks!

DH,
Your going to need the 4" foam in the corners next to the corner traps for additional trapping in the extreme low end. In my room I will be using, in each corner of the room, 2 corner traps and 6-16"x16"x4" thick tiles (3 on each side) to comprise a whole bass trap. These traps should be pretty effective in all but the worst situations. You can use the 2" foam for the ceiling and the walls. Just peel it off the walls carefuly and reuse it. If you do this your going to get as much additional improvement in the low end as you already have in the mids. Then when you add the diffusion to the back wall and the ceiling the whole thing will gel and your going to wonder how you ever got along without it........now, what about the tee vee room?........Fats

OK Fats, I get it now, it makes perfect sense! :)

I checked out Markertek for the acoustic foam, and you are right...it is much less expensive than the Auralex stuff. Now I am sure that the Auralex products are great, but for a home basement, the less expensive product is going to be such a *huge* improvement over having nothing. So far, I have bought some 2 x 4 foot auralex foam tiles (I am so glad I bought the charcoal gray ones, since that is the only color that Markertek sells for the corner bass traps!). These were US$20 each. Markerteck is selling 16" X 16" tiles for US$3.99 each for the 2" ones and US$5.99 for the 4" ones...less than half the cost of the Aurlex tiles. Those big 54" ones look different than the smaller tiles. They look more like the "egg carten" design with foam rather than the blades. Do you think it will effect the sound to have 2 diff types? Heck, for the price of one of those 54" sheets, I would only get one 24" x 48" sheet from Auralex. The Markertek corner bass traps are US$20 each...I have no idea how much the Auralex traps are, but I am sure that they are much cheaper from Markertek. I did not see any diffusion pieces, just as you mentioned, so it does indeed look like Auralex for those...

Thanks for the heads up there Fats...you are going to be saving me some serious cash! :)

DH,
Yeah I thought that would make you smile... :D You can use both the egg carton and the blade styles, It has more to do with the deph of the foam as to what pattern is cut into it. For the deep 4" foam the blade cuts are better.........Fats

DH, a good general rule for foam placement is this: Any surface, whether floor, ceiling, or walls, that you can place a mirror on and see either of your speakers from the mix position, should have absorption. Generally, this means foam on ceiling halfway between speakers and your head, foam on side walls (mirror trick) and absorption (foam) behind the speakers on the wall. Diffusion on the wall behind you can be anything from polycylindrical absorbers to QRD's to bookshelves, etc - the farther away the better.

Speakers should be at least 3 feet from any wall if they're not soffited, or bass will be exagerated. If nearfields are above ear height, point them down to aim at the ears. Some people tilt the console forward, so its surface reflections miss your ears and go for the back wall. By the time those reflections get diffused and back who cares? The main thing you need for best imaging is for no sound to reach your ears within at least 10-12 milliseconds, preferably 20 milliseconds, after the direct sound reaches your ears. This can be figured by rounding off - 1 foot = 1 millisecond isn't exact, but close enough to get there. Using that figure, 10 feet to the rear wall from your ears = 20 milliseconds before reflections return (both ways = 20 feet)

The more walls meet at a junction, the more bass build-up, so that's why corners are best for bass traps. What you're trying to do is convert (by friction) the bass freq's to heat so you can't hear them anymore. In actuality, air VELOCITY at a boundary (wall) is ZERO, since it can't go any further - this is why products such as 703, when used for bass traps, need to be thick and spaced out from the wall, AND hermetically sealed except for the path THROUGH the absorbent. If you have no velocity, you have no friction, and convert no bass to heat. Not good. Using this stuff in corners as a triangular trap, spreads out the freq response (different depth of the trap caused by the triangle shape) which, unless you're tuning for a specific frequency, is usually better. Fats' comment about foam around the ceiling perimeter would give a degree of bass trapping, more if thicker foam, as well as general absorption for the room. I would do this AFTER the mirror trick and AFTER listening to reverb time - you're trying to save money, and you could conceivably shorten the RT60 of the room TOO much if you do the perimeter thing first.

Odds are, the main reason you like your sound so much better with the length-wise setup is that the rear reflections are coming back so much later that they don't smear the stereo image by phasing/comb filtering, until your brain no longer cares. (20 milliseconds or more)

Sounds like you got it on the run James, good luck... Steve

The advice I have gotten in this thread has been fantastic, and I really appreciate...Seriously! Steve...Fats...Eric...Senheiser...Guys, you have really helped a lot. I have been so frustrated by this topic for well over a year now, and everything I have heard and read just makes it that much more confusing...until this thread!

Sounds like you got it on the run James, good luck...

Yep Steve, I really think I do!!! Just by a bit of rearranging and hanging up US$100 of foam (so far, got guite a bit more to go...), my room sounds soooo much better! It is one of those things that I didn't realize sounded *that* crappy until I started fixing it!

I should get most of it done within the next week, and I'll post my results!!!

Cheers!

DH and Knightfly,
The reason I specified the foam around the ceiling perimiter is to eliminate the dihiedral and trihedral corners. It helps to put this up before you do the walls as it help the istall look a little cleaner. I don't think it is overkill and it is always where I have started. Plus it looks really cool..... :D Fats

Hey Fats, I agree that's a cool way to go - the only reason I mentioned the minimalist way was that James was starting to sound a little "sticker shocked" until he found the Markertek prices so I was trying to get him as far for as little as possible. I like the idea of "fat foam" at the corners, you would kinda get double duty out of putting it there, as you pointed out.

I think we've just made a "convert" - I can tell James has seen (heard) the light (sound) - it's always amazing when you first hear what you've been missing and realize that not all the acoustics hype is hype... Steve

Knightfly,
Just wait until he gets the diffusion and the bass traps finished! The traps I suggested will run about $75 for each corner from Markertek ( :D CHEEP! :D ) and they should be effective in the ranges of 50 Hz to 350 Hz.! I was going in the same direction as you as far as trying to minimise the "sticker shock" factor and that's one reason I specified the foam on the ceiling around the parameter of the room. It should help to control upper bass freqs in the room and it may reduce the amount of foam that will be needed to cover the side walls. The side walls should only be treated to the mix position and in many cases it is only necessary to stagger the foam. That is if one wall has foam on it on a given section it is not required to use foam on the opposing section of wall. Especially if you have the luxury of having 15 feet width! IMO it's more important to consider standing wave rather than flutters and early reflections in this situation. I have to stress that diffusion is the element that is going to need to be addressed next. After the treatments are complete, just wait until you hear what a mic sounds like in this room....keep the kleenex handy!.....Fats

By the way, the best way to cut foam is with a table saw or an electric carving knife....Fats

Never tried it with a table saw, but I absolutely LOVE the electric knife... Steve

OK...I am putting together my shopping list for Markertek for this weekend, and a I have few more questions/comments: (just when I *thought* I understood things!!!)

I did some more measurements of my room, and here is a more accurate picture of what is there:

It is in reality a very long "L" shaped room, with a very small "L" part (I hope that makes sense). When I look at the room blueprint, it shows the dimensions as 30' x 15', but that is not quite true for a couple of reasons. First, there is a staircase at one end that shortens the length dimension from 30' to 27'. Also, only the *wide* part of the "L" is 15', the narrow part (where the mixing desk is) is really only 11' wide (bummer). I also checked the ceiling, and it is 7'7" (in decimal feet that is 7.58').

The "L" part of the room is 4' wide x 10' long, and I am just pretending that it does not exist for purposes of calculations...

So I guess I have the following numbers to plug into RoomTune:

27 x 11 x 7.58

After plugging in these numbers, what does the program tell me? Are all of those red bars the standing waves? Can you help me to interpret the data?

Do I need diffusion on the ceiling as well as the back wall? For the celing, how much foam and how much diffusion? I am still a bit confused here I guess.

Fats: As far as the 4" foam next to the corner bass traps...you add 16" of 4" foam along *both* sides of the traps? And what is the deal with the ceiling wall junction and the 4" foam, I guess I missed that.

Steve: Unfortunately, I do not have the space to put the monitors 3' from the walls...they are about 18" now, and that is pushing it.

For the back wall (behind the monitors), do I need to put foam from floor to ceiling, or just from the top of my desk to the ceiling?

Whew! Almost got it licked! Thanks!!!

DH,
You asked a lot of questions so here goes;
" Are all of those red bars the standing waves?"
I'm guessing that they are the room modes.
"Can you help me to interpret the data?"
Not without seeing it.
"Do I need diffusion on the ceiling as well as the back wall?"
It would help, once again you can never have too much diffusion. Anywhere. I have seen rooms that employ no absorption, only design and diffusion. That's the real hip room set up nowadays.
"For the ceiling, how much foam and how much diffusion? I am still a bit confused here I guess."
Just as with the side walls, you may cover the ceiling with foam to the point where you sit. (your listening position) Typically this is about 1/3rd to 1/2 of the room.
"Fats: As far as the 4" foam next to the corner bass traps...you add 16" of 4" foam along *both* sides of the traps?"
Yes.
"And what is the deal with the ceiling wall junction and the 4" foam, I guess I missed that."
I would use 2" foam on the ceilings and the walls. Save the 4" stuff for the corner bass traps.

"Steve: Unfortunately, I do not have the space to put the monitors 3' from the walls...they are about 18" now, and that is pushing it. For the back wall (behind the monitors), do I need to put foam from floor to ceiling, or just from the top of my desk to the ceiling?"
I'll leave this for Steve, who you addressed it to but if there is no answer or if you would like my slant on it I'll return to answer.

James, the red bars are a chart of the frequencies of each axial mode of the room, as entered into the L, W, AND H cells. The left scale is frequency, and the bottom legend notes which mode each bar represents. For example, L5 would be the 5th harmonic of the Length mode, and W3 would be the 3rd harmonic of the Width mode. The ideal, at least for a room with parallel walls, is that no two modes are closer than 5-6 hZ, and that there are no gaps in response greater than 20-25 hZ. The only way to change these figures is to move a wall or raise a ceiling, so if your room is already built then Roomtune can only alert you to the likely frequencies that will cause problems with getting an even response in that room, so that you can plan absorption, bass traps, resonators, etc. accordingly.

I plugged your dimensions in and, while they're not ideal, they don't suck too much. You might have some noticeable peaks at 100 and 150 hZ, but the bass traps and 4" foam should take care of that. I then plugged your room into a more esoteric sheet I found (fortunately) just before I was going to expand on mine, and the modal distribution looks OK in that sheet also. Some low bass problems, but no room smaller than about 4000 Cu.Ft. isn't that way.

On the monitors, you should shoot for 3 feet and take what you get. If they have rear firing ports, the bass boost will be more exagerated. About all you can do if moving away from the wall isn't an option, is use any roll-off switch they might have, or in the absence of that option I would use Fats' technique and apply 4" foam about 2 feet wide across the bottom of the rear wall, across the top of the rear wall, up the corners next to bass traps, so there is 4" foam framing the rear wall about 2' wide as well as vertical 2' wide 4" foam on the two side walls abutting the rear wall. On the rest of the rear wall, 2" or 3" should be enough, since bass buildup is worse at walls/floor/ceiling. You can compensate somewhat for bass levels without resorting to electronic EQ in the monitor path, by mixing at a little lower or higher than the optimum 85 dB - even though that level puts things in a relatively neutral part of the Fletcher-Munson curves, you can lower it to 80 to lessen the perceived bass or raise it to 90 to increase it. I wouldn't recommend raising it though, 85 is about it for OSHA safe levels for 8 hours without hearing protection.

Oh, and don't put your speakers exactly halfway between the floor and the ceiling - dead center between ANY two parallel surfaces is one of the two worst places you can put a mic or speaker or sound source - the other is right against a wall. If you have to raise them to get them away from the half-way height, make sure you set them on a tilt so that they point directly at your ears, not over your head. Nearfields are touchy about keeping the baffle, and therefore the woof and tweet, time-aligned to your ear. Don't set them on their sides either, especially if you have a fairly tight triangle - your head is more likely to move side to side during a mix than up and down, and if the monitors are on their side you will experience HF phasing shifts due to unequal distance from woof and tweet relative to your ear.

Fats, feel free to chime in here, especially if you've experienced otherwise - a large part of my acoustics info is based on about 14 years of part-time study while being able to put very little of it into practice other than sporadically. I hope to drastically change that ratio in the next year or two, but there's a reason why one of my favorite sayings is the one that goes "Life is the shit that happens to you while you're busy making plans..."

James, hope this helped some. IF Fats has opposing ideas based on practical experience, I would go with that. Books help, but nobody ever learned to ride a bike by reading a book... Steve

OK...I am crusing on over to Markertek right now, and will be ordering most of the pieces I need (minus the diffusion, obviously). I am going on a trip Mon - Thu, so the stuff will hopefully be here when I get back, and I can start my sawing! I don't have an electric carving knife, so I'll probably take the primitive approach and use my stone axe!!! :) Hehe...

Once again, I was down in the studio last night working on a mix until about 1:00 am, and just by adding that 2" foam to the back wall behind the desk (from the desk to the ceiling), it sounds 1000% better, so I am excited by the prospect of how it is going to sound by the end of the week!

You guys have been great (and patient)...thanks! :)

Knightfly,
Wow, I'm impressed! :tu: All that is great info. I agree with everything you brought to the table. I was going to say the same thing about using 4" foam around the parameter of the front wall. Lets all get on the same page here so there isn't any confusion. When I say "front wall " I mean the wall you face while you're at the listening position. I call the wall that is behind you at the listening position the "rear wall". OK that said, it looks like you on the way my friend. Now it's time to get the foam up and then shoot the room with pink noise. Get a RTA plot of it. This will show where you need to do some improvements.......Good Luck, Fats
P.S. don't forget the diffusion

James, Fats - We ARE on the same page, glad you clarified the "which wall is which" thing Fats. When I said rear wall, I was talking about the wall behind the mix desk, which if you refer to the walls by where they are in relation to the mix person would be backward. I intended that whole treatment to go on the wall that would be in FRONT of the mix person when they are where they are SUPPOSED to be, facing the speakers.

Also, James, when/if you decide to RTA your room post back here - I saw an article on studiotips.com with some info and a screen shot or two...

Fats, thanks for the vote of confidence - apparently I'm not only studying the right stuff but making some sensible assumptions from what I read; maybe by the time I get to build my own space (looking at a total of 36 x 48 with up to 16' available for ceiling height) I won't screw it up too bad. I was so dumb about this in 1983 I actually thought egg separators on 1/2" carpet pad = soundPROOF. Oh well, at least that room's never had any 10kHz feedback... Steve :=)

In 1983 I actually thought egg separators on 1/2" carpet pad = soundPROOF.

Well, it's not soundproof but it does make for some trapping and diffusion...Acoustic foam is not a soundproofing material either. For soundproofing we need to get into a whole different approach. This room treatment is to control unwanted reflections and room modes. There should be some attenuation of the sound level but not soundproofing. If the foam were indeed performing a soundproofing function I would think that the absorption would cause an operator to run the monitors at excessive levels, creating problems with the response of the room as you pointed out in your references to "Fletcher- Munson" curves.....Fats

By the way DH,
Electric carving knives are very inexpensive. I usually purchase a fresh new one every time I do a foam install. Last time it cost $15. That is less than the cost of 1 piece of foam which I'm sure you will make up in less waste. They may be found at any store that sells toasters, can openers and coffee pots. Out here it's Longs Drugs or Rite Aide....it will save you heartburn and money in the long run. Besides Thanksgiving and Christmas are just around the corner. I can see it now, "What's this gray stuff on the turkey?"...... :D

Haha!!! I love the bit about the electric knife! I will consider that seriously, the holidays are coming...and sooner than we will ready for!

I placed my order today with Markertek, and they say "UPS Ground" which could mean 3-5 business days, depending on when they actually process the order. I also saw a Guitar Center ad today that had the Auralex LENRD traps for $23...I paid $20 at Markertek...I wonder if I should have bought the Auralex ones...oh well...I did not buy any corner traps for the "back wall" yet (behind me when I am in the mixing position), so I guess I can cross that bridge later, since I have to go to Auralex to get the diffusers anyway.

I already have an RTA on my old Behringer digital EQ (I know...I know) that we used to use in our live rig...so when I get all the foam up, I will see if I can figure out what it can tell me! I'll probably need some help here as well. Since this thing is also a digital EQ, I used to use it to set up the room with a "flat response", then I would tweak to taste. How am I to use it in this situation?

DH,
Great! The Auralex foam corner traps are not any better than the other ones available. The only advantage I see in the Auralex products is a choice of colors and cuts. Now, the Behringer EQ / RTA. Does it have a calibrated mic that came with it? If not it will most likely not work for this application. As far as using the eq to flatten the room response, there are 2 schools of thought on this and it has been a thorny issue for years. Some say use eq and some say don't. I go with the don't camp. It induces phase differences and often you create as many or more problems than you fix. I am generally pretty "old school" (couldn't tell could you?) when it comes to audio.....Fats

Look at http://www.acousticsfirst.com and scope ut sound channels and bermuda traps. Great stuff

Fats, I didn't even mention that we were NOT talking about sound PROOFing for James, I'm so used to knowing what I had no clue about years ago that I may have messed up by not stating what was NOT obvious to ME back then - sorry James if you thought otherwise... Just for the record, sound PROOF keeps sound from getting in or out, while sound TREATMENT or CONDITIONING makes what stays in the room sound right.

I agree on NOT using EQ to flatten room response. First, you don't want it completely flat or it will sound too lite on bass and too bright, and second, that's what the various types of materials with different absorption characteristics are for.

I don't think there's an analog and probably few if any digital EQ's out there that don't induce phase anomalies in a signal if you boost more than 1 or 2 dB - any unevenness in freq response of a room will change the minute you move ANYTHING in the room, so the only practical way to handle these problems is to absorb those freqs more than the non-problem ones. That way there is little or nothing to correct for.

It's a lot like the old statement, "The best way to get rid of noise is don't generate it in the first place..." - If you get your room sounding right ACOUSTICALLY without electronic help, everything you do there will be better sounding, therefore require less tweaking, therefore be even BETTER sounding as a part of the final product.

I have some "live to 2-track" CD's of a group called Flim and the BB's, kind of a slightly Avante Garde jazz group - the liner notes claim on at least one of the CD's that they were recorded to dat real-time and then straight to CD. These things sound great!!! Real dynamics, real acoustics for the most part, real music, real players... you have to listen to these babies at about 90 dB or you completely miss some of the softer passages, and that's not good to do since it's all great. Now there's an impressive way to make a CD, even it it never will get any prime time exposure. Their engineer really must believe in "do no harm" - just one example of the bennys of getting things right in the first place.

'nuff rant, later... Steve

Steve,
Hear, Hear and Harumph. Can I get a harumph? (that guy over there didn't harumph).

I would never *ever* use EQ for recording/mixing/mastering! When I go back and read my post on the Behringer EQ, I can see the confusion. The Behinger unit is from my old "live" rig for playing out in clubs and such, I have never used it for recording. In fact, I am going to have to dig it out of my huge pile of equipment and dust if off! It hasn't seen light for probably 3 years! For "live" perfomances we would RTA the room (since they are all so different, and most of them suck), have the unit automatically set the EQ to "flat" for the room, then we would adjust the rest to taste. The "flat" setting was used only as a starting point. Again, this was only for "live" performances of my band!

If I adjust the EQ in my studio, I am not hearing what is truly on tape! It makes no sense to have spent a small forutne on "flat" monitors if I am just going to screw with the EQ anyway! Hell, I spent more on my monitors than I did on our big PA High/Mids!!!

Sorry for the confusion there...I absolutely agree 1000% that you should never EQ the room when recording/mixing. I have read posts of those who do however...they usually get flammed pretty badly!!!

Also, I am not trying to soundproof the room. I understand the difference, and have seen sets of pictures of studios under construction...floating walls, rubber insulation, dealing with air conditioning, etc. I will save *that* project for when I win the lottery, and build a dedicated stand-alone studio in some exotic location! Hehe...who hasn't dreamed of doing that same thing??? Come on!!! Be honest!!! :)

My goal is to get my room sounding the best I can make it, considering it is a pre-constructed room. I know it will never be perfect with the parallel walls and the funky dimensions, so I am just trying to get it to sound decent without breaking the bank too far! Your help has been great so far, and I am making such great progress! I am really jazzed, considering that I have been fighting this fight for a long time trying to decide how to proceed, and instead, getting nowhere! My first big shipment from Markertek is due sometime this week, and I am "chomping at the bit" to get started.

Back to the RTA situation:

I would love to do a before/after snapshot of the room! That would be pretty cool to see the difference that the acoustic treatment makes. With the Behringer unit, I fire it up, (and YES, it does have a reference mic), let the pink noise grind for about 20 seconds or so, and it will genreate the EQ profile automatically for me at that position. I am assuming that I will take reads at my listening position. The system will then boost/attenuate at different frequencies in an attempt to get a "flat" frequency response, is that correct? So how do I interpret those readings?

I guess I could take a quick picture of the spectrum with my digital camera and post them somewhere if you guys wouldn't mind taking a quick look at them and telling me what you think...

Oh yeah...and Harumph!!! :)

DH,
The comments re' soundproofing were in reply to Knightfly's comments. As far as th RTA, if it has a calibrated mic that was supplied with the unit (hee hee, he said "unit") then it will be of some use to you in checking out your room..........Cheerio and Harumph!, Fats

DH,
I had just woke up when I replied to your last post and I hadn't had my coffee yet. I
re- read your post and here's my 2 cents. Shoot the room with pink noise and then let the RTA do its thing. You will see where the peaks are (where the RTA applied cut and where the dips are, where the RTA's boosting). I would venture a guess and say if you can get the room response within + or - 6 to 8 dB your in the ball park. If not, you need to experiment with moving the speakers and other elements in the room or adding and subtracting treatments until you get where you want to be.....Fats :tu: