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Studio Sound Treatment

Discussion in 'Acoustics (Live Room, ISO Booths)' started by Doublehelix, Sep 4, 2002.

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    The New AT5047 Premier Studio Microphone Purity Transformed

  1. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  2. knightfly

    knightfly Active Member

    Joined:
    Jan 18, 2002
    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
     
  3. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  4. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    By the way, the best way to cut foam is with a table saw or an electric carving knife....Fats
     
  5. knightfly

    knightfly Active Member

    Joined:
    Jan 18, 2002
    Never tried it with a table saw, but I absolutely LOVE the electric knife... Steve
     
  6. Doublehelix

    Doublehelix Well-Known Member

    Joined:
    Oct 7, 2001
    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!!!
     
  7. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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.
     
  8. knightfly

    knightfly Active Member

    Joined:
    Jan 18, 2002
    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 $*^t 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
     
  9. Doublehelix

    Doublehelix Well-Known Member

    Joined:
    Oct 7, 2001
    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! :)
     
  10. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  11. knightfly

    knightfly Active Member

    Joined:
    Jan 18, 2002
    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 :=)
     
  12. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  13. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  14. Doublehelix

    Doublehelix Well-Known Member

    Joined:
    Oct 7, 2001
    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?
     
  15. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    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
     
  16. audiowkstation

    audiowkstation Active Member

    Joined:
    Jun 29, 2001
    Look at http://www.acousticsfirst.com and scope ut sound channels and bermuda traps. Great stuff
     
  17. knightfly

    knightfly Active Member

    Joined:
    Jan 18, 2002
    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
     
  18. Kurt Foster

    Kurt Foster Well-Known Member

    Joined:
    Jul 2, 2002
    Location:
    77 Sunset Lane.
    Steve,
    Hear, Hear and Harumph. Can I get a harumph? (that guy over there didn't harumph).
     
  19. Doublehelix

    Doublehelix Well-Known Member

    Joined:
    Oct 7, 2001
    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...
     
  20. Doublehelix

    Doublehelix Well-Known Member

    Joined:
    Oct 7, 2001
    Oh yeah...and Harumph!!! :)
     
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    The New AT5047 Premier Studio Microphone Purity Transformed

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