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Wasn't there an acoustics forum? help needed Reverb & Delay Plugins
Old 26th August 2007
  #1
Gear Maniac
 

Wasn't there an acoustics forum? help needed

Hi all,

I hate reading long posts but if you can wade your way through this because I'm desperate for help

My situation is this, having converted a double uk garage with a room within a room setup three years later I still feel like I'm fighting my room. I have old aboslute 2's on my net machine in an untreated room and get perfectly acceptable mixes from that so I'm pretty sure it's not my ears.

Right stay with me, when I first constructed the studio I did the whole sitting on neoprene thing, 60kg/m2 rockwool 4inches thick in the walls, the whole 9 yards. Unfortunately I had to make a few concessions on the way which I think may have screwed it up completely. I wanted one skin of plasterboard (sheetrock?) on the inside and two on the outside and to cut a long story short it worked out the reverse of that.
Another concession was I ended up needing taller roof beams to support the span, I think it was 6x4 inch or 8 x 6 can't remember now but the upshot was I lost another couple of inches headroom.
I've ended up with a room that's 4.28m x 4.64m x2.02 (horrible dimensions I know). Despite numerous bass traps and proper foam treatment I always find myself with mixes which don't translate onto other systems at all. I have Genelec 1031's with the 15inch sub (I think it's the 7070)
I'm tearing my hair out here and short of moving don't know what else I can do!
One thing I did come up with was stripping the room and taking down the first two layers of plasterboard on the ceiling, keeping the rockwool in place and covering with cloth, now this won't do wonders for my isolation (right in the middle of lots of houses) but would the extra headroom and absorption be worth the effort?
As it is I'm sure I'm getting pretty heavy comb filtering with the ceiling being so low and I only have a foam backed carpet on the floor, so vertically I have hardly any treatment, this way I would increase that by loads and get wooden flooring (the classic setup)
Well thanks for sticking with it and let me know what you think, I REALLY need your help here!
Attached Thumbnails
Wasn't there an acoustics forum? help needed-top-corner-view.jpg   Wasn't there an acoustics forum? help needed-side-reflections.jpg   Wasn't there an acoustics forum? help needed-corner-traps-hidden.jpg   Wasn't there an acoustics forum? help needed-rear-corner-reflections.jpg  
Old 26th August 2007
  #2
Registered User
 
Rick Sutton's Avatar
 

My feeling is that the back splash off the speakers is where the comb filtering is coming from.
Here's what I would try.

1. Move the speakers out from the wall as far as you can. Every inch counts.
2. Kill the space behind and above the speakers completely and with as deep and heavy material as you can.
Old 26th August 2007
  #3
Lives for gear
 
Sui_City's Avatar
 

i think the first reflections off of the roof are also an issue, judging from the pics.

Get some absorption going over your mix position.

And i agree with Rick with regards to the deep adn heavy material. You need to trap the low-end a lot more.
Old 26th August 2007
  #4
Gear Maniac
 

Quote:
Originally Posted by Scoobz View Post
One thing I did come up with was stripping the room and taking down the first two layers of plasterboard on the ceiling, keeping the rockwool in place and covering with cloth, now this won't do wonders for my isolation (right in the middle of lots of houses) but would the extra headroom and absorption be worth the effort?
Thanks for the responses, yes I agree the ceiling is the issue. It will be alot of hassle to strip the room and take down the ceiling, so do you think the benefits will outway the time and financial expense?
Old 26th August 2007
  #5
Gear Maniac
 

Also, I've got 8 broadband corner traps and two on the floor down the length of the room, you think I still need more? That only leaves the wall/ceiling corners
Old 26th August 2007
  #6
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Scoobz View Post
Thanks for the responses, yes I agree the ceiling is the issue. It will be alot of hassle to strip the room and take down the ceiling, so do you think the benefits will outway the time and financial expense?
I really believe that the wall and ceiling are equally contributing to your problems. You don't have to strip the room and take down the ceiling.....bulid a coccoon that traps both the ceiling and back wall (side walls too, out to the listening position, if possible) and take them out of the picture from a reflection standpoint. It can be done even in a small space like yours. I would use a minimum 6" depth and angle the ceiling down to as low as possible behind the speakers to get a 12 to 18" depth at least, more if you can.
Old 26th August 2007
  #7
Gear Maniac
 

Don't know if I can picture that, a cocoon you say? Adding panels to the room to angle the ceiling down? Or build a triangular frame that sits between the ceiling and 'speaker' (front) wall and fill it with rockwool and cover with cloth?

Confused
Old 26th August 2007
  #8
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Scoobz View Post
Don't know if I can picture that, a cocoon you say? Adding panels to the room to angle the ceiling down? Or build a triangular frame that sits between the ceiling and 'speaker' (front) wall and fill it with rockwool and cover with cloth?

Confused
Yeah, a light weight frame, I'd use 1x2", and stuff that puppy. I've built them as helmholz resonators and just plain old insolation stuffed and in your situation I'd probably do the back wall as an insulation stuffed trap and put some helmholz action into the triangulated area in the ceiling/back wall intersection across the entire back wall.
I would construct that with the frame covered with 1/2" soundboard with gaps between the sheets, stuffed with insulation behind and the soundboard covered with 2" Sonex or similar.
Old 26th August 2007
  #9
Gear Maniac
 

I think I can picture that!

Just to clarify you're talking about the rear wall (opposite to speaker end)? There's a door in the middle of that but it definitely gives me another line of thought, damn! More options!
Old 26th August 2007
  #10
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Scoobz View Post
I think I can picture that!

Just to clarify you're talking about the rear wall (opposite to speaker end)? There's a door in the middle of that but it definitely gives me another line of thought, damn! More options!
No, I'm talking about the wall behind the speakers. I can see that I wasn't clear, by "back wall" I meant wall behind the speakers.The worst comb filtering in the upper and mid frequencies is due to the reflections nearest to the speakers, bass problems in a small room are coming from everywhere! But the rear wall can be done as well and certainly would help, probably depends on how much space you're willing to use up. I use to have a similar trap across my entire back wall (opposite my speakers) that was very effective but eventually took it out in favor of a window and door to a patio behind the control room. Took me a while to relearn my speakers but hey! life in a control room cave gets tough after a lot of years. Luckily my control room has larger dimensions and plenty of trapping so I can get away with a few acoustic changes without the problems that would occur in a smaller room.
Old 27th August 2007
  #11
Gear Guru
 
Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by Scoobz View Post
Also, I've got 8 broadband corner traps and two on the floor down the length of the room, you think I still need more? That only leaves the wall/ceiling corners
I see plywood attached to the corners. That is NOT a bass trap, nor are the foam panels I see. Eight good bass traps should make a huge improvement, but I agree with the others that first reflections off the ceiling need to be dealt with too.

--Ethan
Old 27th August 2007
  #12
Gear Maniac
 

No need to be an arse about it ethan, this has been pointed out to me recently too (somewhere else), I explained when I first looked into bass trapping (and yes read everything you've published on the matter as well as many other sources) this was THE way to do it, a sealed box of variable depth where the front panel resonates and the vibration is damped by the rockwool inside (without touching the face itself)
But I guess things have changed, so would I be better off just building a 2' x 6' frame and putting a layer of 4" rockwool in it and straddle this across the corner? What about the dead space behind?
Old 27th August 2007
  #13
Gear Maniac
 

Actually, Rod Gervais has been very helpful and reminded me of the gap between wall and treatment thing, which I would like to do on the ceiling, what's the safest way to put the treatment up there without it falling on my head! heh
Old 27th August 2007
  #14
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Ethan Winer's Avatar
 

Lightbulb

Quote:
Originally Posted by Scoobz View Post
No need to be an arse about it ethan
Nobody's trying to be an arse. I'm trying to help you, okay?

Quote:
this was THE way to do it, a sealed box of variable depth where the front panel resonates and the vibration is damped by the rockwool inside (without touching the face itself)
Yes, but that type of trap needs to be sealed air tight. Also, the variable depth approach is probably not as good as it might seem in theory. Wood panels traps are great in large rooms, and the were popular long ago in pro studios large enough to accommodate the design. But in smaller rooms fiberglass only is the way to go.

Quote:
would I be better off just building a 2' x 6' frame and putting a layer of 4" rockwool in it and straddle this across the corner? What about the dead space behind?
Yes, exactly, with the air space left open.

--Ethan
Old 27th August 2007
  #15
Gear Maniac
 

Well there was an air of superiorty in your first post I didn't take too kindly to but I do appreciate the help heh
Yes, they are air tight but can see they maybe aren't the right tool for the job in this case, I might leave them in place behind the new panels I will make.
I don't really want to throw away the foam so I will mount the tiles on an open backed frame and leave a 2" airgap from the wall, this is only on the side walls btw to stop flutter echoes. That coupled with the ceiling treatment (hey I won't be able to stand in the mix position but who cares! ) and the rockwool/fibreglass across the corners should make a BIG difference right?
Old 28th August 2007
  #16
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Rick Sutton's Avatar
 

Quote:
Originally Posted by Scoobz View Post
this is only on the side walls btw to stop flutter echoes. That coupled with the ceiling treatment (hey I won't be able to stand in the mix position but who cares! ) and the rockwool/fibreglass across the corners should make a BIG difference right?
I still say a monolithic treatment across the entire speaker wall/ceiling is the way to go. You can keep applying patches but your kinda throwing stuff up randomly.
Whatever you do.....best of luck!
Old 28th August 2007
  #17
Gear Addict
 

from someone who had a simillar sized room afew years back. main solutions were

to number one, leave the speakerswhere they are depth wise, move them out wider, and move yourself back a few feet.

2, stick a cloud above the mix position

3 monitor at a lower volume
Old 28th August 2007
  #18
Gear Head
 

"Air of superiority"? I should hope so. Ethan's knowledge about bass traps is superior to yours.

And the point he made was important, and helpful.

Sorry, but dudes who can't tell when they're being helped confuse me. You've gotten some stellar advice from some pros on this thread.
Old 28th August 2007
  #19
Gear Maniac
 

Right thankyou to all who have responded to my dilema, it's really helped my perception of the problem.

And yes, ethan does know alot more than me and I'm grateful for his input, all I was saying was that he was unnecessarily curt and abrupt in his first post which I found rude, I stand by that.
That said I value his opinion and have seen the effort he's put into his research which has helped many people.
Right I'm done defending myself on that matter.


Rick, you've been a star, I'm now trying to formulate the best way of doing this. The helmholtz thing you mentioned, I've always shyed away from that due to my ignorance of it. So we're talking essentially pegboard 5mm thick, and that would be on the face with insulation behind that? I've obviously got it wrong because this wouldnt' help reflections would it (see helmholtz = scary )

Anyways, you'll see in the last pic that panel made of a wooden frame with rockwool inside it covered in material, I've put that across the front corners and that's made a massive difference already! So I'm making two more of those to go across the rear corners. Two to hang a couple of inches off the wall either side of the mix position, some diagonal ones to hang in the top wall/ceiling corners (down the side of the room) and this bad boy front speaker wall thing (and something to cover those bare bits behind the speakers (I read your post before you edited it lol) They were covered originally but I have foam mounted on boards so i can experiment with positioning and had moved them the day I took the picture.
I'm gonna have to find a way to illustrate what I'm thinking about this central ceiling/wall construction above the mix position, so I can make sure we're on the same page

Thanks again to all, I really appreciate it

Scoobz heh
Old 28th August 2007
  #20
Gear Maniac
 

Ok A) Does this work and B) is this what you were thinking? C) Even if it wasn't would it help lol heh

Old 28th August 2007
  #21
Registered User
 
Rick Sutton's Avatar
 

Scoobz,
I can't resize your latest picture so i really can't see what you're referring to. The form of resonator I've used isn't pegboard but what is called soundboard or Celotex here in the US. Think of it as a false wall that is filled with fiberglass and "skinned" on the outside with the Celotex (sorta like a soft plywood). Instead of "skinning" the wall so it is air tight you cut the Celotex into 1 to 1.5 foot wide strips and lay them up with 3/4" gaps between them. The Celotex is a fairly soft board but does have some ability to bounce sound back at you so it is usually covered on the outside with layers of softer materials like cotton batting/cloth or acoustic foam.
I guess my main concern in a room that is that small and has severe acoustic problems is that small patches often aren't good at solving the issues and a more "full wall" approach can help to take the "pain" away.
I am probably sensitized to the reflection issue because in one of my first control rooms (many moons ago) I built a shelf to sit my monitors on that was placed in front of the CR window. The comb filtering was intense and my recordings suffered until I finally figured out what was going on and built a full soffet across the top of the window and mounted the monitors in that. You don't have the room to build a soffet but that kind of approach with a false wall/ceiling can be useful.
I've also seen totally soft false walls used (made entirely of acoustic foam) with the speakers flush mounted, actually suspended, that sounded quite good. Lots of options, you'll get it worked out. These are just my thoughts (my opinions) and will probably be seen as overkill by many but I feel with a tiny room sometimes you gotta really kill it more so than a larger space where reflection and controlled dispersion can be used more effectively.

I've taken a closer look at the picture and it looks like you might have a variable depth acoustic cloud over your mix position. That is the idea, I'd just extend that all the way across the ceiling (not clear to the opposite end of the room but from left to right as you sit at your mix position) and then triangulate it into the wall that your speakers are against and all the way down that wall to the floor.
Old 28th August 2007
  #22
Gear Maniac
 

Thanks for taking the time to explain Helmholtz traps to me, I'm planning on moving next year so i think I'll do it properly in my next place.

Ok retweaked my pic, I think we might have a plan here, I've ordered the fabric and rockwool. The only thing I'm dubious about now is keeping the things on the walls/ceiling. For the cloud I figure little L shaped brackets and raw plugs will do it if I use about four down each side and 3 on the front edge as well as some on the back edge that touches the wall.
I've seen people use simple shelving brackets to hold the wall ones and the corner ones will be free standing.
If anyone has any final advice before I put this plan into action I'd love to hear it, thanks

S
Attached Thumbnails
Wasn't there an acoustics forum? help needed-img_0569-tweaks2.jpg  
Old 29th August 2007
  #23
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Rick Sutton's Avatar
 

Looking good Scoobz! As far as securing the cloud I have one in my main room and I screwed large metal hooks into the ceiling joists and put metal eyes (round loops) on the cloud and hung it that way. Not sure you have enough vertical height for that, just make sure that someting attaches to the structure and not just sheet rock. Sometimes a piece of plywood or a pair of 1x4s that span the joists is useful as a base to attach the cloud to.
Best of luck with it.
Old 2nd September 2007
  #24
Gear Maniac
 

Hi,

Right I'm getting there, parts are taking longer than I would like but the plan is concrete now.
I'm using 4 inch screws into the ceiling joists btw.

Ok so I've got this fabric 'upholstery grade' calico, it's quite a tightly woven cotton weave and I'm worried it's going to reflect high frequencies as it will be very taut across the faces of the traps. Am I completely wrong?

Also I've attached an image of one of a pair of panel traps running down the length of the room, as we've established panel traps are rubbish so I was thinking of converting it to a pair of helmholtz traps. From memory they're sealed units (they have a front and back plywood) and have 4" rockwool inside. Shall I take the face off and put this board your talking about in it's place? (obviously in the configuration you said 1' wide strips) Or would I be better off just taking the front and back off and covering with material?

I hoping to get all of this done by the end of the week and will of course post new pictures when it's all completed.
Attached Thumbnails
Wasn't there an acoustics forum? help needed-possible-helmholtzl.jpg  
Old 2nd September 2007
  #25
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Rick Sutton's Avatar
 

Hey Scoobz,
The fabric is probably fine unless it's shiny and stiff or something else weird. There are lots of ways to check like use two parallel hard surfaces (say in a bathroom...even a shower) and snap your fingers and listen to the tone of the flutter echo. Then hang some of your fabric up and listen again and you can hear how much the fabric is doing to the high end.
Panel traps are not rubbish and are very useful they just won't do the entire job in a tough space. I'd probably leave the panel traps alone but if you're "gung ho" then go ahead.
Just re-read your post and you say your panel traps have plywood on the front? That's kind of strange. If so, opening up the front a bit wouldn't be a bad idea. Just to be clear, the traps I have discussed with you are much larger (full wall and/or wall ceiling) and need some decent cubic footage inside them to work well.
Old 2nd September 2007
  #26
Gear Maniac
 

Well I was partially joking, I was just wondering whether converting it to a helmholtz resonator would make that use of space more effective. Thanks for the response tho! heh
Ah you've edited since I last read, I think I'll take the front and back off then and cover with fabric thanks again
Old 2nd September 2007
  #27
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Rick Sutton's Avatar
 

here's a picture of my main room looking toward the control room. Just to illustrate what I mean by the "entire wall" approach as opposed to just hanging baffles. Nothing wrong with hanging baffles, I use them also.
Attached Thumbnails
Wasn't there an acoustics forum? help needed-img_7-studio.jpg  
Old 2nd September 2007
  #28
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Rick Sutton's Avatar
 

This shows the ceiling a little more clearly. The redwood wall is a modification of the resonators that we were discussing earlier. Notice that the wall above the CR window slants out to produce a deeper trap for more low freq absorbtion. My attic space also acts as a giant bass trap....luckily the studio is located on an acre and I can let a little bit of low end slip out without bothering anybody.
Attached Thumbnails
Wasn't there an acoustics forum? help needed-13.jpg  
Old 4th September 2007
  #29
Gear Maniac
 

Lmao, my entire studio would fit on your rug!

I see what you mean about needing alot of volume for the traps to be effective tho. Control room pics please! heh

Tomorrow's the 'big day' last of the bits arriving still going to do this cloud by ear tho. I know the overall dimensions but the actual construction I'm just going to make up as i go along.
Old 9th September 2007
  #30
Gear Maniac
 

Right all done, pictures when I've had a chance to tidy up properly but I thought you might be interested to hear this. The only difference is the room, so I had a quick 're'eq session on this last night and I think the difference is very noticable.

What you'll hear is 12 seconds of how I had it before (bear in mind this sounded 'right in the room' when I pulled the track back up everything sounded wrong (which was a good sign in my book) so I jumped on the Eq's and tweaked levels. I know the bass still isn't right but I had bounced/frozen it pre room treatment, so I'm gonna have to go back to that but overall at 12 seconds when the new mix kicks in everything seems to open up, the low end is punchy and the top end has a lot more definition and space.

Please let me know what you think

Thanks

Scoobz heh
Attached Files

trouble difference.mp3 (751.0 KB, 226 views)

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