Audio Monitor Placement

[PaulGriffith]

Hey everyone, I've been asking a lot of questions lately, this one is for the audio pros.

I'm setting up a new edit suite in two weeks and have some new monitors. It's a traditional post suite: desk/computer towards the back of the room facing the far wall, couch immediately in front of desk facing the far wall for the producer, then big screen on the far wall showing the output of the NLE.

It's a stereo set of JBL LSR2328P monitors, a matching 10" Sub and a monitor control interface that lets you select inputs and outputs and gives you a giant volume knob and comes with a mic that's supposed to auto calibrate to your room.

Ideally, I'd like to place these on the far wall 8' or so from my desk so both producer and editor can hear. Is that too far away for accurate sound? Pretty sure these are near-fields but not sure just how near they need to be.

Second question, I have a set of M-Audio DX-5's that I'm going to use for a smaller speaker check of the mix that I can switch between with the controller. Where should they be placed?

Thanks for your help audio-bros!

 

[Alcove Audio]

Ideally near fields should be three to four feet apart and your head the apex of an equilateral triangle between the speakers.

The M-Audios would be placed inside of the JBLs as a second reference.


If you want to place the speakers further out front that's up to you, but they will not have optimum sound where you are sitting - you're too far away - and your clients won't get the optimum sound either - too close and probably too low. This is one of those situations where it's probably better to have the clients behind you like in a traditional recording studio.

 

[PaulGriffith]

Ok cool, thanks!

 

[AudioPostExpert]

Ideally, I'd like to place these on the far wall 8' or so from my desk so both producer and editor can hear. Is that too far away for accurate sound? Pretty sure these are near-fields but not sure just how near they need to be.

All small studio monitors are specifically designed to be positioned on your desk (nearfield), not 8ft in front of your desk. As room size grows and the distance between your monitoring position and the speaker increases, the design of the speaker has to change to not only maintain sound pressure levels but also the accuracy of the stereo soundfield. To give you some idea, by the time you get to a very big room (say a cinema) usual speaker technology (cone and dome type speakers) simply can't meet the design requirements and a completely different technology has to be employed. Incidentally, this is one of the reasons you can never get an accurate idea of what a mix is going to sound like in a cinema when mixing in a small room.

The design philosophy of nearfield monitors requires that you sit no more than about 3ft or so away from them. In addition to Alcove's diagram, the nearfield speakers should ideally be positioned further from the nearest wall than to the listening position and there should be at least 2-4 times more distance between the listening position and back wall as there is between the speakers and the listening position. This is all to ensure that what you are hearing is predominantly the sound from the nearfields rather the acoustics of your room. This means that nearfields can be designed with relatively little care about how they will perform in any particular acoustic environment and therefore at a hugely lower price. That's why you can buy good nearfields for $600 a pair, while good mid or far fields are going to be about ten times (and up to about 100 times) more expensive. Knowing all this, you can now see that the speaker and monitoring positions, relative to each other and the boundaries (front and back walls) which you are suggesting are so far from optimal that it would be hard to conceive of a worse setup!! Those JBLs are good little monitors for the money but only if you use them as designed. I don't dare ask how you're going to deal with all the acoustic difficulties that using a sub-woofer entails.

To suggest a solution, if there is one, we need a bit more info, so a couple of questions:

1. What are you mixing for, IE., where are your clients products going to be distributed; Internet, TV, HDTV, DVD, BluRay, Cinema (film festivals)?
2. What are the dimensions of your room (length, width and height) and what shape is it?

G

 

[PaulGriffith]

Nice and detailed, I love it.

70% of my work in this room is going for broadcast TV, about 15% played back in big venues (stereo systems, not surround like cinema), 10% online and 5% misc (BluRay, DVD, Audio CD etc). I'll do some cinema stuff too, but only the rough edit mix will be done in the room, the rest is done by other guys on the team with some waaaay better tools and more audio post experience than I have.

Room is 9'x13', 8' ceilings. With the setup I described earlier, the desk would be about 3-4' off the back wall/shelves just a hair off center (though I'd sit more center), the back of the couch more or less bumping up against the desk and about 5-6' between couch and far wall/screen. It's a video suite first and foremost, audio isn't an afterthought but if I can't get the existing setup to work that way I can figure out a way to pipe audio to a separate set of speakers just for preview playbacks for the client.

Plus, these JBL's sound pretty good, and the screen will be pretty big. Might be fun to sneak a movie in now and again too .

 

[AudioPostExpert]

70% of my work in this room is going for broadcast TV, about 15% played back in big venues (stereo systems, not surround like cinema), 10% online and 5% misc (BluRay, DVD, Audio CD etc). I'll do some cinema stuff too, but only the rough edit mix will be done in the room, the rest is done by other guys on the team with some waaaay better tools and more audio post experience than I have.

OK, first thing to do is put a Low Pass Filter (LPF) on your main mix bus. Set it to 40Hz and at least 18dB/8ve, preferably 24db/8ve or even 36dB/8ve. Make sure that LPF is on the mix bus for everything you do except the ones going the the other post guys. Next, give the sub-woofer to a friend or sell it on eBay!

You're based in the States, so I presume your TV work is for US broadcasters. This means you're going to have to create good sounding mixes, compliant with ATSC A/85 specifications. Major broadcasters are going to have a list of other delivery requirements too, usually the standard stems; Dialogue, SFX and Music (either dipped or undipped), plus an M&E mix. You're going to need an A85 compliant loudness meter (software or hardware) and to be safe, a True Peak Limiter plugin. To be honest, I'm not sure how you're going to do all this without a dedicated DAW but I'm sure it must be possible.

Now back to your room setup. Move your desk so that the front of it is about 4ft from the front wall (where your TV monitor is). Put your JBLs either on your desk or on stands immediately in front of your desk. Take the shelves off the back wall and cover it with sound absorption panels. Put the sofa against the back wall beneath the panels. Then buy a comfy chair with wheels for your producer to sit near/next to you. The sofa will effectively be decoration/additional absorption. Lastly, you will need to calibrate your JBLs, probably at about 76dBSPL but it might be lower, you'll need to check with the ATSC A85 sample test recordings.

I've got to finish off some work now. If you want an explanation of why this is the only setup which will work for you just ask. I'll try and answer later this eve or tomorrow.

G

 

[PaulGriffith]

Thanks again for the detailed post, I appreciate you putting your time into it.

I get what your saying about being in the middle of the room and slapback from the wall. Regardless of where the producer sits I couldn't put the desk that close to the far wall/screen. I need to be far enough back to not see individual pixels, which with that screen is a good 7-8'. With some treatment on the rear wall is going for a 1:1 speaker-ear-wall distance ratio instead of 1:2 like you said earlier going to jack me up that much?

There's a bit of music multitracking in like (like 3 minutes out of every 140 edited minutes), but the bulk of it is either graphical with stock mixed music (I just have to set a level, no EQ or anything) or doing some sweetening on a single person talking through a handheld, a little EQ and occasional noise removal.

Again, thanks for your time. I'm not trying to argue with you or weasel my way out of great audio at all, just trying to weigh options and come up with the best solutions with minimal compromise in every area; video, client preference, personal preference and of course, audio.

 

[AudioPostExpert]

As you seem to appreciate them, here's another detailed answer:

It's impossible to make a room which is acoustically perfect and it's incredibly expensive to make a room which is even very good. Adding picture to the equation just complicates the problem further and requires even more compromises. This means that you generally have to prioritise the compromises biased towards either picture or sound, depending on the work you specialise in. That's one of the reasons why in TV and Film post production you have separate video editing suites and sound editing/mix rooms.

The problem you've always got is that the speakers have to point towards the monitoring position and therefore also at the wall behind you. The signal from the speakers reflects off the back wall, comes back into the room and interacts with the signal coming out of the speakers. Depending on where you're sitting, these reflections are either going to summing with the signals from the speakers or cancelling with them. This means that there are going to be a bunch of frequencies which will appear to sound either much louder than they should or much quieter. In a small room the problem is worse because the amplitude (level) of the reflections is going to be higher relative to the signal from the speakers and therefore the interaction greater, both in terms of the amount of summing and cancelling at individual frequencies and in terms of the number of frequencies affected.

When we process audio we do so on the basis of what sounds best, which means if we are doing our job well, we're going to be (subconsciously) applying EQ, choosing effects and relative levels which counteract or minimise the undesirable summing and cancelling caused by the room's acoustics. The result might sound good in your room but would sound completely different in any other room (except one with perfectly identical acoustic properties). In your case, the EQ'ing (sweetening) you do may have the opposite effect when your mix is played in another room, your levels could be anywhere from slightly wrong to severely wrong and there maybe artefacts from your noise reduction which you can't hear or conversely, artefacts which you feel are unacceptable which would be unnoticeable elsewhere.

Now, if you put your nearfields on your desk and your desk is near the back wall, your speakers are going to be say around 6' from the back wall causing two problems: 1. Your sound is going to be originating from a different place to your picture (on the front wall) which will disassociate the sound from the picture and sound weird and 2. It's going to increase even further the amount of reflection from the back wall and therefore the amount of summing/cancellation and the number of frequencies affected.

Using broadband absorption on the rear wall would appear to solve our problem by eliminating the reflections in the first place but the simple fact is that even the most expensive/sophisticated absorption is only partially effective and then only partially effective in certain frequency bands. You will hear a dramatic improvement with a lot of high quality acoustic absorption on the wall behind you but so severe are the problems to start with, there's almost no chance this improvement will be enough to make the room usable to produce professional quality results.

Going back to your original suggestion of the nearfields on the wall next to the video monitor. The speakers are now much further away from the rear wall, which would reduce the problems from the wall behind you, providing you are sitting closer to the speakers than the rear wall, which you have indicated will not be the case. So in this case, the improvement from having the speakers further away from the rear wall will be negligible. Plus, this setup will severely increase the effect of a number of other problems as there will now be a lot more reflective surfaces between you and the speakers (side walls, ceiling and floor) as well as a boundary effect caused by the speakers being just a few inches from the front wall. And, due to the design of nearfields, not only are you going to have severe frequency inaccuracies, you're also likely to have quite severe inaccuracies in the stereo sound-field and even potentially have to overdrive your speakers to produce the sound pressure levels required by the calibration (probably 79dBSPL as you would be sitting further away).

I'm not saying that absolutely, definitely your room will be unusable but with your combination of speakers, room size and required monitoring position, in my opinion you are going to need to get a professional acoustician in, to stand even a slim chance of achieving accurate enough sound reproduction to allow you to consistently produce broadcast quality mixes.

G

 

[PaulGriffith]

Great, thanks!