Audio Post

[G. Lee Gordon]

I have been involved with audio recording for years. Someone suggested that I do audio in post. What does it take to do this. I currently run PRO TOOLS, but have several other interfaces (cubase, acid, etc.).

What equipment does it take to run a professional audio post house (audio sync, surround mixing, etc.)?

[Bryan Beasleigh]

You might want to post this question at dv.com as well. Jay Rose the moderator over there, may have some answers for you. Douglas, the moderator from this forum, is also well versed in post production audio.

[Douglas Spotted Eagle]

First, you'll need monitors. I'd recommend Mackie, M-Audio, KRK, Blue Sky, or the new JBL. (Avoid the JBL you see at Comp USA and computer stores)

These are powered, so you don't need amplifiers.
Then you need an audio card. I HIGHLY recommend Echo (Layla) or M-Audio Delta's. (1010) If you are using ProTools, you might have the MOTU, if you're an Apple guy, MOTU is fine. Sux for PC though.

Find accurate speaker placement.

Then you need to tune the room. Auralex (www.auralex.com) is a great place to start learning more about that. It's more than just putting speaks in the room if you are serious about doing this.

Then you need an app that manages 5.1. ProTools offers this, so does Nuendo. I prefer Vegas for surround, with their new film tool it's damn hard to beat on either platform. With Downmixing, which is critical, it's hard to screw up a 5.1 mix.

Sync is only an issue if your audio is living outside the computer. We use a Lynx for our sync work, it's awesome, but the M-Audio and Layla both have blackburst and SMPTE in/out.
Then you need to get trained in how to do all this correctly. I recommend VASST for that. http://www.vasst.com
Get good cabling, get good speaks, get trained. Then go out and start making great mixes.

[Glenn Chan]

1- From a business standpoint, you need just enough equipment to get the job done while keeping your clients happy. Um... some of them won't notice if your mix won't translate.

If you want to impress clients and get the big bucks, you might want to pay some attention to a nice looking studio. I personally wouldn't spend too much money on this stuff as it's dumb and it makes some business sense to be cheap.

2- Auralex/Room treatment: Auralex wants to sell you foam. This isn't a bad thing necessarily, but their products are not good at everything and there are cheaper alternatives.

For sound absorption, the design outlined in Jay Rose's book is just as good and cheaper. The key is using owens corning 703 fiberglass, which is just as good (in terms of sound abosorption) as acoustic tile but cheaper.

Acoustic foam also is not that good at absorbing bass energy under 125hz. That's according to F. Alton Everest's Master Handbook of Acoustics, although I don't know about the bass traps Auralex sells. If you do not have a bass problem in your room (you'll hear it as "boominess") then you do not need specialized products. Also... you do not need to worry too much about sounds <125hz if going to broadcast televison when most people are using crappy speakers and you are rolling off bass anyways (for more compression --> louder sound).

Diffusion: According to F. Alton's Everest's Master Handbook of Acoustics, diffraction grating diffusors are better than all the geometric diffusors out there.

A specific arrangement of slots will diffract sound and cause it to scatter because of some interactions with interference. That's probably not a very good explanation. You can see pictures of diffusors at http://www.rpginc.com/products/diffractal/index.htm.

Do you need it? I don't know.

I also don't know any good cheap ways of getting cheap and good diffusors.

There's also a lot of differing opinions on acoustics... which makes the whole subject very confusing.

If you're deciding where to place absorption material, you might want to look into the absorption free zone idea:
http://www.realtraps.com/rfz.htm
I wouldn't trust everything on that site, but the RFZ idea:
A- It doesn't hurt much.
B- Everyone who talks about it thinks it is a good idea.

There are some designs that are much more extreme that what realtraps.com suggests. These involve splayed walls... see http://www.acoustics101.com/room_its...0Room%20Itself (at the very bottom) for one example. Changing your existing room to the above makes very little business sense so I would forget about it. I doubt it makes you a better sound engineer.

If you want to get really serious about room acoustics then go visit some sound studios with modern designs, see which sound good, and figure out who the acoustic consultant is. You could also try reading F. Alton Everest's Master Handbook of Acoustics. I don't think spending lots of money on room acoustics makes too much business sense though.

3- There's many different opinions on room acoustics. Here's another take on Auralex:

http://www.prorec.com/prorec/article...256C190080663A

4- If you want to make your clients hear a good room, you could make it look swanky. It's the monster cable principle... (Monster cable sounds better because you think it is. It isn't actually better.)

[Douglas Spotted Eagle]

Much of what you say is correct, Glenn, but only to a degree. I'm really surprised reading what you posted...

Jay's book, while good, doesn't go into the study and treatment of the room. This is EVER so critical with 5.1. His book doesn't even touch 5.1 setups unless there is a third edition somewhere.

Auralex costs a little more, and they sell a whale of a lot more than 'just foam' and further, your post suggests that there are cheaper alternatives which might cause someone to do something REALLY stupid and put up bedding foam or something along those lines. Eggcrate is illegal in most places, and will never, ever pass firecode anywhere.
BTW, Auralex will *usually* design your room without cost.

I've never once in my entire life seen a room that doesn't need some form of treatment ever, anywhere. Given that I've produced over 300 recordings ranging from hope-to-be pop stars to work for films like Hidalgo and Samurai, I've seen a lot of rooms.


Cheap diffusors? Cam be made with 2x4 scraps, can be made with Kleenex boxes, can be made with nearly anything that's squared off. Lots of time vs buying a 6.00 panel from Auralex or equivalent company.

Any client that is impressed by looks over sound in a 5.1 environment isn't a client you'll want. Because sure as hell, they'll get a mix home and hear it muxed to stereo or mono with a crappy decoder, and it's all your fault. And you'll end up redoing the mix. Multiple times.
We get an average of one 5.1 mix a week sent in here with the author asking "what did we do wrong?" 7 times out of 10, it's a bad setup. The remainder of the time is that they don't check downmixes or phase, have bad rooms, and boomy is only the beginning of the problem, far from the only problem.

Foam doesn't deter bass frequency movement below 200 hz. Correct. But Lenrds and TubeTraps DO add mass to a corner, and DO dampen wall movement/vibration and DO dampen harmonics. That's why they are found everywhere. It's not like people buy them because they are cute and take up a lot of room.

I'll wager 95% of the guys here have 12 x 12 or similar proximity rooms, square in shape, sheetrock walls, square corners, hard ceiling, and either carpet or rug on a hard floor. Then, they've got their desk pushed within 18" of the wall, perhaps a small area behind the desk so they can get to cables. Speakers set on desk or shelf attached to or next to desk, never having been measured for sweet spot. Nothing to damp or decouple speaks from desk or wall. And that's just the stereo setups. And it doesn't get much worse than what's described above for mixing.

The ONLY good 5.1 system I've seen that's not somewhat costly is the M-Audio LX4 system, and that's useless in a room larger than 12 x 12. Less than useless. No, folks don't need to buy the 18,000.00 Mackie system we have, nor the Hothouse 4's which we also have. But you DO need good monitors. In a room that's treated, or at least been pinged so you know where the problems are.
It's all about airflow, stopping frequencies from moving in the airflow, and being sure that while you don't overpressure the room, you also don't underpressure it. All of this is unrelated to STC, or Sound Transmission Co-efficient.

"Spending lotsa money on room acoustics doesn't make sense?"
OK, you're right. You can spend a lot of TIME, and a lot of effort, and a fair amount of money making do with workarounds, or you can get the right stuff. Whether it's Owens Corning 703 wrapped with non-treated burlap, BlackBoard, Metrofoam from Auralex, or concrete tube molding stuffed with shattered fiberglass drilled every 1.5 inches with a .5 drill bit or a TubeTrap, it doesn't make a difference if the DIY stuff is build well. A sheet of 703 Rooms need to be treated. At the cost of a buck a square for 703 and cost of about 1.40 a square for Auralex, plus the covering for the 703....it's not really any cheaper when you figure in your time. And it's ugly, IMO. Unless you find an acoustically porous fabric that looks nice. And frame it.
The better you hear it, the better engineer you'll become. Maybe not more creative, but better at listening.

Whether they are treated ugly or beautiful doesn't matter. Sound reflection control, which isn't remotely related to recording audio in a low STC environment, is critical for mixing. Period, end of story. If you can't hear it right, you can't mix it right.
It's akin to saying you don't need a good broadcast monitor to view video on. No one in their right mind would color correct nor title for broadcast or DVD delivery without a good visual monitor to preview on, right? Same goes for audio. If you can't trust what you are listening through, you can't feel good about sending it out. That doesn't mean spending tens of thousands, but it DOES mean that you need to pay serious attention.
DIY or pre-made....one costs a ton of time in labor, research, and effort, with often less than stellar results. Then there is the slightly more expensive way, following the thousands who have gone before and experienced the problems and solutions. Of which I'm one. I'm now on my 7th major post room, and we have 3 rooms in which we do audio. Only one in which we mix for broadcast. With 3 different monitoring systems ranging from the Hothouse and Mackie 626 with the 150 sub, to the ancient Craig boombox. There are also Auratones, and a standard home-quality 21" TV with stereo speaks if we need to go there too.
Our ears are far and away more sensitive than our eyes. We hear what we see. We define what we see often by what we hear. I demonstrate this every other day of the week. If you can't make it sound good, even the best Viper shot, Lucas edited video will look like crap. Because it sounds bad.

Sorry to rant, but this subject is ridiculously often filled with voodoo, myth, and DIY that is either dangerous, useless, detrimental to sound quality or sometimes all three.
Useless and detrimental is no big deal. People buy junk all the time, and build home made stuff that sometimes works, other times doesn't. Dangerous is another story.
off rant :-)

FWIW, Ty Longley was my friend.

[Glenn Chan]

"Spending lotsa money on room acoustics doesn't make sense?"
OK, you're right. You can spend a lot of TIME, and a lot of effort, and a fair amount of money making do with workarounds, or you can get the right stuff.

Sorry, that comment was referring to changing an existing room to one with splayed walls. To me it just doesn't seem to be really worth it.

A sheet of 703 Rooms need to be treated. At the cost of a buck a square for 703 and cost of about 1.40 a square for Auralex, plus the covering for the 703....it's not really any cheaper when you figure in your time. And it's ugly, IMO.

The sound trap Jay Rose proposes uses acoustic foam on top of the fibreglass. And you put all that in a wood frame, and use furring to get it off the wall if possible.

I haven't looked into the pricing difference between Auralex and 703. If the price difference is $1.40 versus $1+labour, it looks like the Auralex stuff would be a better choice.

However, there a difference between the 703+auralex/sonex/whatever panel and just auralex foam:
Bass absorption extends further down a bit.
No consulting

Cheap diffusors? Cam be made with 2x4 scraps, can be made with Kleenex boxes, can be made with nearly anything that's squared off. Lots of time vs buying a 6.00 panel from Auralex or equivalent company.

I read most of F. Alton Everest's Master Handbook of Acoustics and he talks about diffraction grating diffusors, which seems to be a lot better than traditional diffusors.

I have never seen DIY instructions for these (I personally like DIY solutions) but there are also very few vendors making these.

Whether they are treated ugly or beautiful doesn't matter. Sound reflection control, which isn't remotely related to recording audio in a low STC environment, is critical for mixing. Period, end of story. If you can't hear it right, you can't mix it right.
It's akin to saying you don't need a good broadcast monitor to view video on. No one in their right mind would color correct nor title for broadcast or DVD delivery without a good visual monitor to preview on, right?

Ok my standards are really low right now. I have started interning at a place that does just that.

Well, they're still in business. (Yes, I think it's wrong too.)

I've never once in my entire life seen a room that doesn't need some form of treatment ever, anywhere. Given that I've produced over 300 recordings ranging from hope-to-be pop stars to work for films like Hidalgo and Samurai, I've seen a lot of rooms.

I've listened to a fraction of that so I don't know what works and what doesn't. Listening to rooms definitely seems to be the most practical as there are many competing theories on what good room acoustics entails.

5.1 mixing: Some people don't do a lot of it. Certainly your room design will be different if you want to mix 5.1.

It's all about airflow, stopping frequencies from moving in the airflow, and being sure that while you don't overpressure the room, you also don't underpressure it.

I've never heard of this. As far as I know, wind currents in the path of a sound source is bad but I have never seen room pressure mentioned. Could you provide more information on this?

voodoo, myth, and DIY that is either dangerous, useless, detrimental to sound quality or sometimes all three.

Ok I agree with you here. Certainly, I don't think anyone here should trust what I'm saying. If you look at various sites with information on acoustics, you will see a lot of different philosophies. For bass absorption, the following 3 sites all have their pet favorites:

realtraps.com membrane bass absorber (there's a sheet of plywood placed out from the wall that vibrates sympathetically/resonates with bass frequencies and absorbs them)

auralex.com foam in corners.

F Alton Everest / Master Handbook of Acoustics
Helmholtz resonators.

Of the three, all but auralex have measurements of the things they talk about, except there's a lot of 'mushiness' in the data. The data does not agree with theoretical models.

[Douglas Spotted Eagle]

Glenn, I'm glad you took my post in the manner I intended it, because it was fairly intense.

Everest's book is very, very good, but I don't know I'd put all my stock in it. Real-world experience has taught me that his writing, like that of Jeff Cooper (incredibly awesome budget studio design)
isn't always founded in reality.

Diffraction grating diffusors have many advantages and a few disadvantages over traditional panels, no doubt. It's like a fish trap in how they work. You can also build these DIY, but they are ugly unless you have access to fine woodworking tools. They aren't cheap if you buy them built...but probably cheaper than your labor and research is worth.

http://www.ethanwiner.com/acoustics.html has probably the most objective write I've seen on DIY stuff, and he's got his science down in reality rather than theory.

For higher frequencies, which are problematic for dialog etc, foam is just wonderful. Inexpensive, easy to manage, installs easily. And a good brand won't break down. I had Sonex stuff; it died in 3 years. I've got some Auralex and some of it's nearly 10 years old. Still running sweet. No stinky, no crumbley.

I have a Hemholz-type resonator in the rear corners of my studio, front walls are splayed. Tracking rooms have Lenrds from Auralex. There's not too much bass energy in that room, mostly vocal and flutes, so they are great for killing those reflections. I don't think the Lenrds do quite as well as Auralex or TubeTraps claim, but they DO work. Not possible to totally measure them due to where and how they work.
Diffusion and absorption kill a room's ring, absorption kills reverberants. Foam can do both, down to about 200 hz, at which point it becomes more or less useless, and 703 or resonators need to be installed. Most pro and semi-professional mixes for vid won't contain a LOT of information down in this range, unless its from a music library or sound effect libe, and will have been compressed already. This will still boom/bloom, but not to the point of requiring gross treatment.
I mostly advocate video editors to do 3 things:
1. Get an absorption/diffusion panel behind the speaker monitor
2. Get an absorption panel behind the mix position that covers an area as large as the distance between speakers.
3. Decouple speaks from desk or shelf with decoupling pads/mounts.

Have the room pinged/RTM'd so you KNOW where the problems lie. Doing these small and very inexpensive things will generate FAR better audio than the engineer/editor is currently experiencing.

As far as pressure/flow goes...
If you have audio monitors that can't reach efficiency until they hit XXdB, and you have a room of XXX cubic feet that will begin gross reflection prior to the speaker hitting it's XXX efficiency point, you've got a mess. (called a blivet, 10lbs of crap in a 5 lbs bag)
So you have 2 choices. Either treat the room very well, or get smaller speakers that are efficient at a lower level. Don't buy 12" speaks for a 12' room, and then add a sub to that.
Diffusion can only defract the audio moving at XX velocity, absorption can only suck up so much of it, so don't overburden the room with monster volume that some monitors need to be at peak efficiency. One of our guys recently did this, and his mixes are very thin as he tries to compensate for his error.

[Glenn Chan]

1. Get an absorption/diffusion panel behind the speaker monitor
2. Get an absorption panel behind the mix position that covers an area as large as the distance between speakers.
3. Decouple speaks from desk or shelf with decoupling pads/mounts.

What the absorption on the sides and ceiling to create a reflection free zone?
(According to the information at realtraps.com)

2- What about diffusion? Do you think putting bookshelves with books in them would help?

Have the room pinged/RTM'd so you KNOW where the problems lie.

Sorry, what do you mean by ping/RTM?

[Ruchika Tekkeveetil]

hi - i am having problems with audio - this may have occured while capturing - the file is an avi file. i was told that i needed a real time renderer like Canopus is the ADVC-100Bi-Directional Media Converter any good - my collegues are using DV storm 2 ultra. do you know which canopus product to use ? is there any other way for me to avoid audio problems withotu capturing again ? thanks