What acoustic treatments for vocal booth?

Posted: Fri Dec 06, 2002 5:54 am

I've read the posts from Doublehelix about possible acoustic treatments for his studio,and all the answers from those guys as Nightfly,Cedar Flat Fats(...).I've also read most of the links provided...
I was very interested by all these informations which should be useful for myself too!

But what's still a little bit confusing for me is how could i readapt these informations for a vocal booth treatment?
Indeed,i suspect my "vocal booth" not to be optimized for vocal and acoustic/electric guitar recordings;(for ex.,the sound is too "close",especially for acoustic guitar....)

My "vocal booth"(6,5ft lg/6,5ft wide/7,2ft height) is a square room and i've put 1'' foam tiles( on about 50% of the walls),carpet on the floor,and stretched material at the ceiling and on walls(between the foam tiles)
1)So i'm wondering if in that case bass traps would be useful,or special treatments for standing waves (as for a control room,for example).
2)Furthermore,as the sound seems to be really "dead" ,should i reduce the absorption or modify it (less foams tile?/ and are the carpet on the floor and the stretched material at the ceiling the good choice ?).

I must admit that i've got some big difficulties to achieve a good recording in that room ,and some help would be wonderful for me!

Thanks

Posted: Fri Dec 06, 2002 1:36 pm

The two same dimensions, 6.5 X 6.5 are a real problem. If you try to "liven up the room, you will experience some major standing wave and comb filtering. Reduce one of those dimensions to 5'. It is going to be difficult to add any liveness to a space that small. Perhaps you should just keep it dead and add ambiance after the fact. Do you have a larger "live " room? If so, send the vocal out to a speaker in the live room and record it back to another track using a large diaphragm mic. Blend this in with the vocal track at mix. You will be surprised at the "air" and "sparkle" it will add..... Fats

Posted: Fri Dec 06, 2002 5:06 pm

You could kill two birds with one stone if the method you use to shorten one of the dimensions to 5 feet (100% agreement here) was to build a floor to ceiling bass trap. You could place 2" Owens Corning 703 (compressed fiberglas board insulation) floor to ceiling as a fake wall, 5' from the opposite wall, and caulked for an airtight seal - cover it with open weave cloth, such as burlap or speaker grille cloth (more expensive) If you placed the new absorptive wall at an angle, so that the space behind it was 18" deep at one end and maybe 10" deep at the other, you would have both a broadband absorber AND a bass trap.

O-C 703 is notoriously hard to find at consumer oriented stores, here's a UK link (within the quotes, I copied the whole reply) from the studiotips.com site that may help. Maybe this contact knows of sources in your area.

"Hi-

All the O-C products are now available under the Knauf-Alpocor name in
the UK, the slab fiber products known as Crown Slab.
http://www.knaufalcopor.com/products/product.asp?ProdID=18

Atkins insulation can supply quite cheerfully.
http://www.atkinsinsulation.co.uk/

I spoke with the European O-C rep, and he confirmed the sale of O-C's UK
business to Knauf."

Knauf has materials that are similar to the 703 - either will work well as the "acoustic resistance" needed to build a trap.

I can easily believe you're having a hard time getting good recordings in that square room - it's a perfect recipe for high frequency flutter echoes among other things.

If you need more info on traps and how to build them, here's a link that will help. Click on everything that sounds remotely useful, the site won't let you send specific links...

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

Fats' idea on micing the larger room's ambience is a good one - if that's not an option, you'll probably need to use your best digital reverb on the vocal, and feed some of that into the headphones when the vocalist is recording takes - just don't print the reverb, you'll want to be able to make changes during mixing later.

The reverb in the cans is just for the sense of space it will give the vocalist so they don't think they're drowning in a sea of marshmallows... Steve

Posted: Fri Dec 06, 2002 5:17 pm

Steve,
Sea of Marshmallows,,, ahhh ha ha ha ha....LMAO.. some very good points and I really like the broadband absorber & bass trap idea. Just one thing though. Do you work for or own Owens Corning? ruk ruk....You really seem to like that stuff. 4" foam is almost as effective .... Fats
Very Happy

Posted: Fri Dec 06, 2002 5:38 pm

nightmusic,
I got the message, but you sent it as a "report this post" rather than a private message so I have no way of replying to you. Please resend it as a private message. To answer your question, yes square rooms are a NO NO! I have to look for it... but I have a book that outlines all of this. There are accepted ratios for rooms that audio is to be recorded and played back in. Some of these are referred to as "Sepmeyer Ratios". (not sure about the spelling) I can give you some of these as soon as I find the book. I moved into a new house about a year ago and I'm still digging looking for stuff. Man I have too much sh*t!... I'll look for that book, meanwhile send me another private message if you wish. ........ Fats

Posted: Fri Dec 06, 2002 9:06 pm

Knightfly,

You beat me to the punch with that link to the SAE site...........it's just a pity they don't see fit to actually credit John Sayers by name for all that free reference material.

In regard to parallel walls and standing waves.........once walls are approx 12deg off parallel, standing waves become less of an issue. This also applies if your ceiling is parallel to the floor.

Most references to vocal booths that I have come across advocate making the booth DEAD and adding verb, delay, etc., later.......something that has already been advised here.

Cool

Posted: Fri Dec 06, 2002 9:38 pm

Just to add some info, making a vx booth dead is not a guarantee that you will not get comb filtering. Proper dimension is the only way. Square rooms or rooms with two dimensions that are equal are a real problem. Steer away from this. Ideal vx booth dimensions, 5' X 6'X 9'. fits the before mentioned sepmeyer ratios. I am still not sure about that spelling. ........... Fats

Posted: Fri Dec 06, 2002 11:42 pm

Fats,

Is it those dimensions themselves or the ratio between them that is preferable?

Cool

Posted: Sat Dec 07, 2002 12:51 am

Sepmeyer was one of two acousticians, don't remember the other, who each suggested different sets of "ideal" room ratios, assuming parallel walls. Three of Sepmeyers' favorites were 1.00:1.14:1.39, 1.00:1.28:1.54, and 1.00:1.6:2.33 -

I wrote a simple spreadsheet several years ago that calculates axial modes of a rectangular room and graphs the response, out to 8th/9th harmonics or 400 hZ, whichever happens first - I found that Sepmeyers' "ideal" ratios could be improved upon slightly, but I doubt that one ear in 100 or more could tell which was which.

According to Everest, there is little point in calculating the tangential and oblique modes of a room, since the minute you put furniture or people in the room it all changes. I'm not sure that's completely true, but at the time I liked it because it made the job of programming a spreadsheet much easier for someone who doesn't live for spreadsheets... You can download my spreadsheet for both excel and lotus, at

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

The name of the file is roomtune - it's a self-extracting file with both the lotus and excel versions, plus a doc file with some application notes.

If you want to play around with room dimensions, this is an easy way to do it. You can, for example, leave the cursor over any one dimension and play "what if" very quickly.

As is mentioned in the docs (I think) the goal for a good sounding room is not to have any two modes of a room closer than 4-5 hZ, nor farther apart than about 20 hZ, up to around 300 hZ where it becomes kind of a moot point. This is not as easy as it sounds, especially in a smaller room - Usually, when you gain better spacing from a dimension change you lose it somewhere else.

To see what one of the Sepmeyer rooms looks like, simply (in the example of 1.00:1.6:2.33) set the height dim to 10, width to 16, and length to 23.3 feet. Presto - Sepmeyer "C", graphically.

The BBC has found, in their experiments with vocal booths, that which dimension is which is not critical. If you have a room that has a footprint of 10 x 16, the ceiling could be 23.3 feet and it would have similar sound. Sooo, for vocal booths it's normal to have a higher ceiling that either wall dimension.

Fats, it's not that I'm in love with 703 - it's just cheaper (when you can find it) and denser than even 4" foam, and easier to make semi-rigid panels from when building corner traps or splayed side absorbers. I still think at least some foam, in the right colors and patterns, makes a recording space look pretty cool and high tech and when I get that far with the next space there will be a little bit of everything including rockwool filled poly absorbers, slat resonators, etc... Whatever is called for to solve a particular problem.

This month's EQ has a short article on treating a room that covers some more portable ways of wall treatment - looked like some possibilities there... kinda liked the white plastic lath panels for foam mounting, and the fact that they let you stand the foam off the wall for better low absorption.

BTW, 5x6x9 will give you two dimensions supporting the same frequency at 188 (2nd harmonic of length and 3rd harmonic of height) and again at 376 hZ (not as important) Better with a 5x6 to use 8' ceiling - still some modes a little farther apart than ideal, but a small room will NEVER give ideal modal spacing, all you can do is compromise.

As I understand it, John Sayer SOLD the rights to the SAE site and I think they said he is no longer involved with it. Still, you'd think a word or two wouldn't hurt...

Anyone interested in getting just ONE good book on basic acoustics for further study, I'd strongly recommend Everest's Master Handbood of Acoustics. He has several others out, but this one covers nearly all but some specific "budget" plans. The book runs about $20 from Amazon (no, Fats, I don't own Amazon either - damn!!! :=)

I think I forgot what the original question was, so if I missed it somebody remind me - otherwise, "Glad ya got ta stop by and see me..." (hehehehe) Later... Steve

Posted: Sat Dec 07, 2002 12:16 pm

Steve,
Some great info, thanks for the back up on the Sepmeyer thing... I think the book you spoke of by Everest is the same one I mentioned. It can be found at Borders and Barnes and Nobel. Just kidding about the Owens Corning thing.... I saw that same article in EQ this month and I too like the plastic lattice application. The only reason I am always pushing the foam thing is it is easier to deal with than the 703 and it can be reused in different places if it is removed with care. Some of us just don't have the carpentry skills that others do and foam is just so much simpler to deal with. An electric knife and a little glue, zip, zop, zap…your there! In this case the rooms demensions needs to be adjusted so your idea may be the better. I think that panels made with 703 and fabric actually have a superior aesthetic appeal.
If you have the time could you run the room modes on a 5'X6'X7'6" booth for me...Thanks ............................. Fats
_____________________________________________
It's my opinion, I'll play with it if I want to …… Very Happy

Posted: Sat Dec 07, 2002 9:01 pm

nx ny nz f
0 0 1 75.3
1 0 0 94.2
0 1 0 113.0
0 0 2 150.7
2 0 0 188.3
0 2 0 226.0
0 0 3 226.0
3 0 0 282.5
0 0 4 301.3
0 3 0 339.0
4 0 0 376.7
0 0 5 376.7
0 4 0 452.0

x=6', y=5', z=7'6" -

These are just axial modes - I ran a Bonello plot also, still looks good with all three sets of modes. Unfortunately, the bbs code doesn't allow pasting or I'd put up the graph. There are a couple of wider than 20 hZ gaps, but apparently the tangential and oblique modes fill those in, since the Bonello distribution shows no specific problems - Overall, looks like a winner.

I know what you mean about tools and/or skills, I get used to being able to build nearly anything I need that nobody sells for reasonable, that I tend to forget not everyone has that option - My shop has both arc and gas welding gear, drill press, lathe, small mill, several stationary and portable power tools for both wood and metal, built-in air, pressure washer (3200 PSI)both air and airless paint spray capability, numerous air tools, etc -

One of my favorite types of construction for studio furniture is square steel tubing with oak ply for surfaces, the square tube painted satin black and the oak done with satin Varathane which keeps things light and modern looking. Simple but classy, and you can put anything anywhere once you figure out where you want it. I've also used common pipe fittings to make articulated pods for different tabletop gear, so you can position it where you need it. Painted the same satin black with oak ply floating shelves and you can put a BRC or a tabletop processor wherever it's needed and just push it out of the way when it's not.

When I finally get the chance to do a real standalone facility, I intend to utilize several different tools to get whatever acoustics I need, especially in the tracking room and drum booth - For example,I like Everest's hinged panel approach for reverb tuning - open = short RT60, closed = more diffused and longer tails - options rule! The control room will end up with a shorter RT60 and deader than the other rooms (except vocal booths), so that I'm not letting the Control room reverb affect ambience decisions.

The neat thing about being able to do a separate building is that I can have 24 foot ceilings if they're necessary - try THAT with a rental or a remodel job... Steve

Posted: Sat Dec 07, 2002 9:19 pm

Steve,
Thanks for running those dimensions. In reference to your comments about steel furniture, Most of the stuff in my studio area is steel. Speaker stands, chairs tables, bookcase, torch lamp, all pretty much painted balack . The room looks pretty hi tech. 2 steel futon style chairs at the rear of the room that serve as bass traps.... along with the ottomans for them. I gotta get a digital camera so I post some pics. Coolest home studio in th' hood...(the only one actually) ...... Fats

Posted: Sat Dec 07, 2002 10:08 pm

This link has a varied collection of things made by those of us who frequent HR.com.........www.longsoughtfor.org/postn/html/modules.php?set_albumName=DIY-
Audio&op=modload&name=gallery&file=index&include=view_album.php

Hope it works........you will find my contribution under my HR nik. Cryptic clue......"Antipodean Stone".

Cool

Posted: Sat Dec 07, 2002 10:21 pm

I gotta do a moderator thingy here...EVERYONE,... when you are posting links please be sure to hit the enter bar at the end of a line. If you fail to do this, the line will run on and readers have to use the left to right scroll bar to read the entire page, not just your post. This also screws up the entire active topics page. Thanks, Moderator Fats

Posted: Sun Dec 08, 2002 4:59 am

Fats,

Just an assumption here, as everything looks fine to me, but are you saying that the long link I put in my last post just ran on as one loonnnggggg line?

If so, that could explain why I have encountered this phenomena (i.e: UWP=unexplained wide pages), in the past but didn't understand how it happened.

Cool

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