John Sayers' Recording Studio Design Forum Archive

Should slat resonators be designed for the target frequencies such as the room modes, or evenly across the 100 to 600 hz range?

For example: I calculated the room mode frequencies of a 12x10x8 foot room to be:

12') 47, 94, 141, 188, 235, 282, 329, 376, 423, 470, 517, 564, 611
10') 57, 114, 171, 228, 285, 342, 399, 456, 513, 570, 627
8') 71, 142, 213, 284, 355, 426, 497, 568, 639

Should I design the resonators for problem frequencies like 141, 171, 213, 235, 285 etc. Or should I just make many that are evenly spaced from each other such as 100, 140, 180, 220, etc. What ends up being most effective and balanced? I was going to go for the evenly spaced aproach.

You've calculated just the axial modes for the 12x10x8 room - when you do all 3 types of modes and look at distribution, the room doesn't look so bad. You didn't mention the room's purpose; tracking, mixing, both? Or mastering, just good listening...

Generally, broadband corner absorption should be the first thing you do in a room; this will go a long way toward evening out the response. For a mix room that size, you want it fairly dead, with bare floors and at least the area over the desk absorbed at the ceiling - beyond that, first reflection points (do a search on mirror trick) should be treated, the rear trapped with as deep trapping as you can spare room for, and (if speakers will NOT be flush-mounted) thick absorbent behind each speaker.

Speaker and head location will also be critical, in all THREE dimensions; with 8 foot ceilings, it's too easy to end up with either or both at exactly half the ceiling height, which will put both your head AND the speakers in a first harmonic NULL for the room height.

For more on that part, do a search on harmon - you should find a couple of threads where I explained how to use a spreadsheet/graph and the paint program to map out where things should/should NOT go in your room -

Post back if you have problems with any of this... Steve

Tracking will be the primary purpose. Later I plan on modifying it with bass trapping in the back of the room for mixing.

I'm going to investigate the nulls before deciding on a recording spot. At the moment I was thinking of setting up in the corner with the mics facing into the room.

If you are the sound source would you use the same concept as the speaker location and just substitute yourself for the location of the speakers? In other words, if you have determined a good speaker location for a listening room would it follow that this would also be a good place to use as a tracking spot; or do the mics and reflections from the nearby wall create more complications that render this approach useless?

Would you want to stay away from center or is the center a good location? If the mics are facing close to one wall, (because you are the source with your back to wall) they would only pick up early reflections from this one wall and longer reflections from other walls. So by damping this close wall as you would the area behind speakers you are achieving the same effect. You are basically substituting the mics for where the listener would be and the source(you) for where the speakers would be in a listening room setup. Am I right in thinking this or are there more complications I'm not considering?

In the center the reflections would be about even from all directions, right? In theory which should sound better?

Thanks for the suggestions, I'm going to do that search you recommended.

Dead center in all three dimensions is probably the worst place to put anything; your head, a mic, an instrument, etc - this is where all modes either peak or null, so not a good spot for even response.

You're right, it makes little (if any) difference what's in a spot, it's either good or bad - so that harmon reference should also help you pick locations for instruments, ears, mics, whatever.

I've been playing with ETF a bit for the first time tonight, and found that even moving your body around can make quite a serious difference in response of a speaker/mic/room combination; stands to reason that an instrument/mic/room would have the same tendency. Moving anything in the room will change SOMETHING, it seems...

"At the moment I was thinking of setting up in the corner with the mics facing into the room. " - I'd be careful on that one; any sound (above roughly 200 hZ or so) fired into a 90 degree corner, will come back out exactly parallel to itself; this can catch the (fairly strong) node at the REAR of a directional mic, and possibly cause phase cancellations; worse, if you're micing in stereo using a spaced pair, each mic could get the reflections from the opposite side, and really mess up the track(s) -

Bottom line is your ears though - put 'em where you think the mic should go, (plug the other one), and if it doesn't sound good in your ear it ain't gonna sound good on a neumann either... Steve

I searched for 'harmon' but didn't pull up much. I'm not sure what you mean by harmon. Is that short for something? Could you explain further please?

Perhaps this is what Knightfly refered to: http://www.harman.com/wp/index.jsp?articleId=131

Thanks clueless, I think that's it.

That's a link to the spreadsheet I used; I just did the search on this site for harmon, guess the one I was looking for got lost. I'll find it as time permits and post it in the stickies so it doesn't get lost again... Steve

-- there is an entire section on finding good/bad spots for speakers, heads, etc, that uses this sheet for the graphic map of a rectangular room; that's what I was looking for.

That sounds like a useful program. I tried the modecalc but I think you have to use the measurements it gives you for the nulls to make your own drawing right? So these are two different programs we're talking about?

Thanks Steve.

Yeah, the only advantage to modecalc is that it doesn't require you to have Excel on your computer to run; the harmon sheet give you a really cool graphic display of where the peaks(antinodes) and nulls (nodes) caused by axial modes will be located in a (rectangular) room - using this, you can figure out where NOT to put you or your speakers, or mics and instruments for that matter.

Finally found the thread I was talking about -

http://www.johnlsayers.com/phpBB2/viewtopic.php?p=18059

Let me know if you have other questions this doesn't cover... Steve