In the Spirit of Giving:

Doc Bernard

Doc Bernard

Indie Arms Member
I am going to share a trick to sound treating a control/edit room for audio. This is not about isolation, but controlling bounce and nodes.

So, you have an edit room, but man does the audio bounce around and give you a false RT60 time

First.....where are your monitors? The audio kind, not video. They should be no closer than 3' to you, and a minimum 3 ft' spread to where your primary listening position is. You want to try to keep an isosceles triangle going.

So on to the treatment, There are many theories: Dead, Live, Live end/Dead end. But for a general rule, you shouldnt have to plaster the walls completely with treatment to get a good result. You just need to hit the reflection points around your room (1st order reflections).

So: My "Mirror" trick.
Materials needed: Your eyes, painter's tape, a decent size mirror, and a buddy who owes you favor.
Step 1: If your monitors are against a wall........you need pull them out away from the wall. (walls are bad, em'kay?) A foot is good. That's their new home.

Step 2: Treat the area on the wall directly behind the monitors. I use BX8's, so for me 2'x2' is good. That cuts any off-phase reflections coming from the porting.

Step 3: Get out your buddy from his box. Hand him the tape and the mirror. Sit in your listening position.

Step 4: Starting on one wall, have your buddy slide the mirror on the wall. You keep looking at the reflection in the mirror. Any time you see a monitor in the mirror, have your helper mark it with tape.

Step 5: Continue around the room, repeating step 4.

Step 6: (The Hard Part) Do the ceiling the same way.

Step 7: Now you know where treatment should go to cut those nasty primary reflections. Treat with treatment of choice, usually a 2x2 to 4x4 area is all that is needed on each "spot". And hardwood floors.......not a good thing. Put a good throw rug down.

This is in no way a solve everything solution. But it will greatly improve the sound in your standard bedroom (I mean editing bay, :grin:).

This does nothing for sound isolation/transmission. And only helps a little in "tuning" the room. But it will knock down any primary reflections you hear.

Next lesson: Trap that bass.
 
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Couple additional notes...

1" foam does very little other than the highest frequencies , 2" foam is the minimum for real absorption of mid and highs evenly. 3" to 4" is better.
If you space acoustical foam (or any other acoustical absorption product) off the wall equal to its height, that helps ~80% as much as having that thickness in foam.
i.e. if you space 2" foam, 2" off the wall without a hard surface backing on it, it'll act very similar to 4" foam.
Space 3" foam, 3" off the wall, it'll act similar to 6" foam.
Be careful not to have a rigid board directly behind the foam however, as that removes this effect.

Another note, in addition to the "primary reflections" Doc points out, there's also an effect called "flutter echo" to be aware of.
Basically, this is 2 large flat, parallel walls opposite each other. Sound bounces back and forth between them and causes sound to "ring".
Easiest solution is to make try for a checkboard foam pattern on each wall, such that directly opposite any section of hard wall, there's foam and sound can't "ring" back and forth.
Handle primary reflections first though.

Third note,
Foam below 2-3' doesn't help much. Legs, chairs, furniture, ect... diffuses lower sound. Much more likely the sound near the ceiling will need more help.

And last note,
Auralex does a free "room analysis" if you want their help/suggestions. Basically you send them your budget and a drawing of your room setup with dimensions, and they give recommendations for what products to use and everything should go, as well as explanations behind why certain panels go where. Don't even have to buy from them, just some free, room specific advice if you're looking for it.
http://www.auralex.com/praf/default.asp
 
Ugh! Parallel walls. Gohanto, you ever do standing wave testing? It's amazing what it shows in a room. Nodes and antinodes.

Another thing to avoid, if you are building a room..........multiples. a room 10' x 20'.....not good. Tough to flatten.

I wrote an excel program that all you had to do was plug in your dimensions and building materials and it would give you a good representation of what frequencies you would need to target to flatten out the room. May have to go find it now. Same with my "Golden Ears Acoustic Testing CD".

It had all 31 frequencies (three different lengths), pink and white noise, pulses, calibrated levels. That was a God-send when I did acoustical testing for spare bucks.


Good points, BTW. Of course you ruined my lesson plan. LOL! Maybe we should co-teach this. I bet a lot of people are scratching their heads about now. They thought ol' Doc was just a knuckle draggin' gun guy.
 
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Doc, yeah I do a lot of sound testing, I actually work as an acoustical consultant so I see a lot of bad rooms haha. My personal favorite was a 20x20x10 ft. concrete room that wanted to be a music studio for under $1,000. (Saw that when I worked for Auralex a little while back)

The calculator you're referring to sounds like a "room mode" calculator and there are actually a bunch online now. Here's one...
http://www.bobgolds.com/Mode/RoomModes.htm

Although it doesn't do frequency testing.
I use FuzzMeasure for that and it's my personal God send.

So about messing up your lesson plans :P if you want to write up some acoustics articles though, I'm down.
 
You eat that many eggs? If you do, sound treatment is not an option......airlocks are indicated.

In honor of Leslie Neilsen. A fart joke.

On a serious note, no. Unless your problem is in the very high frequencies. Then egg cartons would work. Sound is a strange entity. The density and the thickness of the material have an inverse action on frequency. The denser the material, the farther down the frequency plot it affects.

Egg cartons are pretty thin and mid to lower frequencies do not even see them.
 
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I could use a little input too. My Room is probably really messed up. It's 13x9 at least, with one end expanding out another couple of feet. I have to put my desk in a corner due to size restraints. But I have some auralex, and some 3" pyramid panels, a bookshelf, throw rug and furniture that breaks up the waves. I also use JBL LSR4328 monitors that self calibrate to minimize bass nodes. I seem to get decent mixes that transfer OK, but I just don't know if my room is ruining my perception. I do have the monitors at an equilateral triangle with my head. Maybe you guys can offer some educated input?

You can see my desk placement here: http://www.humboldtmusic.com/webpage/index.cfm?id=162

You can also see the room throughout this video for the first minute, and from the 5 minute mark to the end as I spin around playing the bass:

And here's recent song I tracked and mixed in this room. Does it seem to be a balanced mix? My buddy Xeff played acoustic and sang lead and one harmony - I played/sang the rest.
http://www.reverbnation.com/play_now/song_8888496

Does that mix sound woofy or thin on your systems?
 
To add to this topic. If your room is in your house and your bot overflowing with space. Covering the back wall, or actually any wall with bookshelves (with books on them) can be a great surface breakeruper and you get to store all those books on audio you have been collecting.

Egg cartons don't absorb hardly anything. They can be useful for breaking up a flat surface. But mostly they are useful for giving you that 1960's garage studio look.

To deaden a room for say Foley or as a Vocal room we had very good results with packing blankets against the wall and egg crate foam on top. Unless you want an extremely dead space you are going to want some surfaces uncovered. In our very small Foley room the ceiling was bot parallel with the floor so we left that uncovered and one wall was a double paned glass sliding door and there was a control room window on one wall. The floor usually had surfaces on it so it was uneven but hard. Getting close to the treated walls could get you VERY dead and moving closer to the glass livened things up. We also had a curtain we could drop over the glass wall to add more deadness if needed. Or we could open the sliding door (it opened into an edit room so still isolated from the control room) and get a bigger livelier space.

Worked amazingly well and was very affordable.
 
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