John Sayers' Recording Studio Design Forum Archive

Hi, I'm new here and I have searched through many posts before asking this question. I'm hoping someone can give me some advice to cure what ills my home studio area.[img]

The largest problem appears to be standing waves. The layout I posted is the best I could do, with what I had, to even out the extreme low end <60HZ. Moving the bookcases to the corners and moving the sub to its current location is what improved that. Before, the very low end was uneven throughout the room. The bookcases are 5' tall. The drawing is proportional. Now my problems are from 90-120HZ. In the current location, those frequencies are severely reduced. I tried moving the whole studio around so I would face the short wall where the bookcases are. That is what everyone recommends, yet when I do that, I have severe phase cancelations in the vertical plane. If I stand, 90-120HZ are present and fairly even. When I sit, they are gone. Sounds like I need bass traps, right?. But where should I locate them and what type should I build or buy? Should I start with one in each corner? What about the phase cancellation in the vertical plane? What causes that? Is it also solved with bass traps? And lastly, does anyone want to loan me some cash? I don't think my wife is too keen on supporting my studio habits. I'm one of those fools who bought some nice recording gear, yet failed to realize how important the room was for getting an acurate mix.

I would appreciate any help.

Thanks,
Tom[/img]

Hmm. The JPG didn't seem to go through.

Tom - you've got to take the reverbtime of the whole room down as evenly as you can afford to do.

If you can't afford to build a proper room - and you've got a good sized room that could make a proper room - go out and get some 703 rigid fibreglass and start taming the room. This will effect only the highs and mids, the lows require bass trapping etc.

Alternatively you could lash out and get some of Ethan's units - you'd need a few of them in your room.

Have you looked at what others have done here??

http://johnlsayers.com/Studio/index.htm

cheers
John

Thanks for the reply John. I will take a look at the pictures to see what others have done. I have bee trying to think of ways to treat the front corners. If I had the extra cash, I would just buy something pre-made, but money is a bit tight now. I was actually thinking of a modified panel trap made for the corner. Tell me if this is a stupid idea. What if I made a frame across the corner that was 2' wide and filled it loosely with fluffy insulation. Then I would cover thae frame with 1/4" luan. I would make the whole thing it air tight. The luan panel would vibrate from the low frequencies and the fluffy insulation would dampen the movement. I was thinking that might work for the front corners. It would also be extremely inexpensive. But I don't want to take the time to experiment with this if it's already been tried and found to be worthless. Do you have any thoughts on this?

Here's a shot accross the bow. First center your mix position, and put the monitors on stands (equalateral triangle). As for the acoustics --You could do this all DIY. Mainly: 2x4's/Burlap/703/plywood/wood for slats. Takes some time, will still cost money, but you could save mucho dinero.

Jeff coopers book , building a studio has useful pics for building bass traps. You could also build a variable depth bass trap on the back wall instead of a 6" trap.

Also you might try a book case in front of the rear wall trap, and chair in front of book case, if the 703 makes the room too dead -- bookcase providing a little home made diffusion -- seems like your depth would be long enough.

I don't think my wife is too keen on supporting my studio habits.

Can't help you there.

Best,

Dave

Hi Dave,
That's not fair; your drawing looks better than mine! I like your thoughts though. I have a couple questions. What type of bass traps do you recommend in the corners? Is just putting 4" thick sheets of 703 from floor to ceiling going to be the right approach, or should I make some type of panel cabinet? You have a cloud on the ceiling and 703 on the front and back walls. Won't that make the room real dead? It has a wonderful sound right now for recording acoustic guitar and violin, I would hate to make it totally dead.

Are there detail on making the slats? I have seen the drawings, but I am still a bit uncertain on many things about them. I have the ability to make them, I just need a bit more detail. I am still trying to find a good source for 703 in my area. There seems to be some discussion as to whether 703 or 705 is better for bass traps. I have no clue myself, since I have not tried either yet.

Keep blasting away! I can use all the help I can get. I would like to get this stuff solved soon. I am a very impatient person and all I really want to do is have a room I can mix in. I'm not hoping to become an acoustics expert, but I see that I will need to gleen some more knowledge before I will get good results.

Thanks,
Tom McKeown

Hey Tom,

What I have learned from John and others is that this stuff is not so much an exact science, as an approach to what you want to be doing in your room. But much can be improved.

In general bass tends to collect in corners -- so that's a good place to soak it up with panel traps, or at the very least some 703. I am guessing you don't want to build soffits, so generally speaking an absorptive wall behind the monitors will lessen phase cancellations between wall and speaker. Also keeping the monitors as far from the walls as practicable will help. This all had to do with the mind sorting out direct signal from early reflections.

You could also put a slatted wall over the 703 in between the speakers, to liven up the room, if needed. I also suggested a bookshelf behind your mix position for DIY diffusor. You will still want a panel trap back there IMO to absorb the real lows. Your sense of livelyness comes from the highs.

Break up the standing waves. You have to treat the entire spectrum as much as possible. Bass panel traps get the real lows. 703 spaced off the gets the lows' too/low mids and highs (actually Owens corning specs show that 6" of 703 absorbs pretty uniform down to 60hz -- you can get the sabins spec manual from them -- something I gleaned from the late Malcolm Chisholm). Burlap over 703 compliments nicely getting the very high freqs. John's slots work on the low-mids while reflecting the highs-- for a sense of livelyness.

Remember your ceiling is often the closest wall -- what's it made of? Keep looking for the slot details - they are on here, and you will get the idea eventually. There will be some compromise between a lively performance space and decent monitoring conditions -- as with everything in life:)

703 & 705 debate is kinda moot. But I vote for the 703:)

I am a very impatient person and all I really want to do is have a room I can mix in.

Patience is a virtue in this game.



Best,

Dave

Hey Dave,
Thanks for writing back. I have this idea for a corner bass trap design that i want to run by you. I have read others who had a similar idea, but no one that I have read has disproved or aproved the theory. I was thinking of making a panel trap on the front corners of the room. The traps would be triangular in shape and run from floor to ceiling. The dimentions would be 2' x 8'. The front of the panel would be 1/4 luan. I would then put 1"-2" of 703 on the inside of the trap, spaced from the front panel by 1/2". On the front of the trap, I would space a 2" piece of 703 off the front. This way, no 703 actually touches the trap, so it can move. I figure the trap itself will get the real low stuff and the 703 on the front will get everything else. Does this sound like a good design? I know it's pretty hard to prove a theory until it's tested, but I just want to get some extra thoughts on it. I don't know if this would be better than simply puting 4" of 703 across the front corners. The majority of my room problems are under 200hz, (at least those are the ones I notice the most).

What do you think?
Tom

Well maybe some more folks will chime in here, but I think that a triangular corner panel trap could work nicely. Btw, I put 2 in the rear corners of my CR, plus a 2x4 frame in front of them for hangers and another layer of 4" 703 covered with burlap. You can see part of the details here:

http://www.johnlsayers.com/Studio/Pages/Bluefield1.htm

Jeff Cooper argues that a multi-dimensional panel trap is quite useful for smaller home studios as they cover a wider range of low freqs. He has a chart (which I used) showing how to target your rooms modes and the panel construction details. "The thinner the membrane used on the front of the panel, the more effiecient and finely tuned the result will be." The only thing is that thinner means more airspace is required for the panel trap.

Your roughly 10' & 20" dimensions produce standing waves roughly at:
1st 2nd 3rd harmonics
10' 57 113 170
20' 28 57 85

1/8" plywood would require a 25 " 3/4" air gap for the 10' dimension
107 1/4" ...for the..............20'


you can see a thin membrane requires allot of air space. Luan is pretty thin and not too dense:)


a 1/2" plywood face would require 6 1/2" and 26 3/4" airgap for the 10' and 20' dimension respectively.


In other words a corner triangle panel trap 6 1/2" off the wall to 26 3/4" might give you some nice results, using 1/2" plywood., an airtight enclosure and 703 space off the interior of the panel to dampen even more.


The formula is d = 28,900
_______over

fo(squared)M


d = depth of required airspace, inches (distance between back of panel and rigid wall)

fo = fundemental absorbing frequency of basstrap, Hz

M = surface density of panel, lb/ft(squared).

3/4" plywood would require even less airspace in the panel.


It's all in Jeff Coopers book. I found mine at ederlyinstruments.com

Best,

Dave

Dave,
Are you saying that the trap would be smaller at one end and wider at the other? I think I need to get the book to see some pictures. I only have two corners to put traps in. There's a door in the back right corner and no corner at all on the back left. ( it goes into the next room) So, I'm left with two traps in the front corners. From my tests, that's the main place the bass builds up.

I appreciate the time you have taken to do some math and help me come up with solutions. BTW, you have a cute daughter. Does she visit the studio often? My daughter likes to read books in the "big" chair while I am working. I remember when she was that young. Seems like a lifetime ago. She's 9 now, going on 30. Very intelligent, but of course I would say that.

Here's a pic of something you might try. Maybe 2 corner panel traps, one flat one in the middle, and a 2x4 frame in front to hold 4" of 703, covered in fabric/burlap.

I think a flat panel trap could work on the back wall as I first drew.

My daughter thanx you for the compliment , she has a sister as well now

Best,

Dave

Interesting idea Dave. What's your reasoning for it? How does it work?

BTW, if your getting sick of writing back, just tell me to go away.

Hey Tom,

No problem here. Basically the idea is that you can build a panel trap as a triangle or any shape for that matter. As for the math, I can't take credit -- that was out of Jeff Coppers book.

What I am thinking here is that you have a very absorptive front wall (uniform in the feqs) that will help eliminate reflections from the rear of your speaker back to the listening posiotion (especially if they are rear ported - like my M1's). Then the slotted splayed boxes help to create a RFZ while keeping the mix position live, and with 20' CR length, probably a bass trap on the rear wall, maybe slots, maybe 703 -- perhaps John can chime in here. You might also consider an upside down "V" panel trap on the rear wall. I know this sounds like allot of options, but something will emerge from the realm of possibilities.

I built something similiar to the picture before I ripped it out and put in soffits. You can see the original treatment that was there before on the link I provided. I didn't do the panel traps however.

My room is 15' deep and I eventually opted for soffits and an absorptive rear wall, including panels (3) , hangers and 4" 703/burlap. Ceiling was 703/ R19 -- covered in burlap. I like the sound, but it's not a space for guitar/violin ambience. If you need detail pics I think I have some showing my panel back wall build out.

This shows the basics of the flat panel design courtesy of the kind work of Ethan Winer:

http://www.ethanwiner.com/basstrap.html

Best,

Dave

Hey Dave,
I found some 3" 703 only a few minutes from my house. I ordered 12 pieces of it. I can start experimenting this weekend.
Thanks for the help.