38% off the back wall?

[Folded]

Hi there,

I've read quite about bit on this subject and here's my very tiny room. While following the equilateral triangle, and also the 38% rule, my speakers are only 2 1/2 feet apart and I am about 2 feet away from the monitors. This leaves me not much space to put a desk optimally to avoid direct reflection.

I'll have bass traps around some of the corners and also side walls and perhaps backwalls. Is it possible that I listen more towards the center or even 62% from the room?

Thanks in advance.

Folded

[Glenn Kuras]

The 38% is only a starting point. I would move back a bit and see if you get a better response. The 62% would work, but the back wall would be pretty darn close so you would get some pretty intense nulls and peaks coming from the back wall.

[Weasel9992]

Originally Posted by Glenn Kuras

The 38% is only a starting point. I would move back a bit and see if you get a better response. The 62% would work, but the back wall would be pretty darn close so you would get some pretty intense nulls and peaks coming from the back wall.

Yep...that's the downside. You have to pay a lot of attention to the back wall if you're going to put your head that close to it...thick bass trapping is going to be mandatory. Then again, it would be anyway...

Frank

[jhbrandt]

Totally.

Take a mirror and have a friend move it around on the side walls, ceiling and back wall while you sit at the mixing position. When you see a speaker in the mirror, put absorptive material there where the mirror was.

Also, you should be 38% from the wall that you are facing - the front wall. For your monitor speakers - 2 1/2 feet apart is too far if you are only 2 feet from them - your mixes will end up too monophonic. I suggest you bring them together a bit.

good luck.

[Folded]

Wow, thanks for the reply.

So is it ok or not? I think I'll be treating the backwall with 4" fiberglass anyway. I'm in the process of clearing the room now. And getting a ECM8000 mic and also fuzzmeasure.

Let's hope I can get a relatively good sound out of this room.

Folded

[jhbrandt]

What are your room dimensions? cubic meters or feet?

I would try to stay close to the front 38% of the room. But I have no idea where that is. You didn't mention any room dimensions.

Please give more info and we'll do our best to steer you right.

Cheers,
John

[jhbrandt]

Terribly sorry. I didn't see your png file before. DUH.

Dimensions don't look too bad.. it is small - what is your height?

The centers of your speakers should be 2' apart and you 2' from them.

IMO, Trap all the corners, create a rfz around your speakers & you are off to a good start.

If I had the height, I could give you a pretty accurate idea of where to position yourself.

cheers,
John

[Weasel9992]

Originally Posted by Folded

...my speakers are only 2 1/2 feet apart and I am about 2 feet away from the monitors.

I missed this little factoid in my first responses. 2-1/2' is not wide enough, and if your room is so small that you can only get 2-1/2', then that's a problem. Your whole stereo field will be smashed into the center and to compensate you'll end up getting *way* too radical in terms of panning, time-based effects and EQing to get a "big" mix. When you take it to another system it'll sound crazy. Is there any way at all you could get a 4' triangle? That's usually a pretty good place to start, then tweak from there.

Frank

[kurt]

Originally Posted by jhbrandt

I would try to stay close to the front 38% of the room.
Cheers,
John

So in your opinion 38% from the back wall is a big no, no?

[Folded]

This community here sure is helpful! I'm grateful for the responses thus far.

John, my room heigh is around 8'7. Yes, a horribly low ceiling. I was just thinking 2' was a little too narrow as well from experience. And also, if it was 2 feet apart I'd have to be using a desk, which would lead to comb filtering problems off the desk wouldn't it? Or should I not worry about it.

However, If I'm trying to get a 4' triangle, then I would be no where near 38% of the front wall.

Also, I am not able to treat two of the corners, because of the door and a bookshelf.

So, do I ignore the 38% rule and get a decent sized triangle for listening? Or do I stick to it?

Folded

[Weasel9992]

Originally Posted by Folded

This community here sure is helpful! I'm grateful for the responses thus far.

John, my room heigh is around 8'7. Yes, a horribly low ceiling. I was just thinking 2' was a little too narrow as well from experience. And also, if it was 2 feet apart I'd have to be using a desk, which would lead to comb filtering problems off the desk wouldn't it? Or should I not worry about it.

However, If I'm trying to get a 4' triangle, then I would be no where near 38% of the front wall.

Also, I am not able to treat two of the corners, because of the door and a bookshelf.

So, do I ignore the 38% rule and get a decent sized triangle for listening? Or do I stick to it?

You're in a tough room....this is where a room starts to become so small that you have to make big compromises to really make it work well. You should not move your head back to the 50% mark to make the 38% guideline work, though your room seems to be so small that no matter what you do you'll be within a short distance of either the 50% mark or the 25% mark, neither of which is good.

The only thing you can do is arrange things in such a way that you get the best response possible from the room...experimentation will be critical. For example, if a 3' monitor width gets you close to the 38% starting point, then do that and tweak from there.

As far as the desk goes, you're going to have to live with some kind of furniture man. Even the high end places have big consoles, which are comb filtering machines. Everybody has to work around it to some degree.

Frank

[Wes Lachot]

Kurt,

In most rooms, 38% from the back wall is far too close. Even in a 20 ft. deep room, 38% would be 7.6 ft. from the back wall. Since we always have to deal with a 1/4 wavelength null from the back wall, we need to do the math and see what frequency has a quarter wavelength of 7.6 ft., and see if that's an acceptable frequency for a null. So we divide the speed of sound by 4 and divide the answer by 7.6, and we get 37 Hz as the null frequency for 7.6 ft. That's a little tough to take, since 37 Hz approximately the frequency of the low D on a 5-string bass guitar (plus there's a lot of kick drum energy around that frequency). The range from 30 - 40 Hz really is something you need to hear accurately.

On the other hand, if you have the luxury of a 26 ft. deep room, say a mastering room, the situation changes, as 38% of 26 ft. is 9.88 ft. If you do the math on 9.88 ft., the 1/4 wavelength null moves down to about 28 Hz, which is low enough to be less consequential for bass accuracy. I really prefer to be 12 ft. off the back wall if possible, which moves the null point down to the threshhold of inaudibilty (23 Hz).

-Wes

[Ethan Winer]

Though as you told me the other day Wes, the 3/4 wavelength null can be a killer too!

--Ethan

[kurt]

Hi Wes. My CR is 6.5 X 4.94 with 3.10m ceiling. True, I have problems at ca: 35 & 100Hz. I´m about to build more bass traps on the back wall. At the moment there is 100mm with 100mm space 120 X 120 cm bass trap + massive corner traps. I plan to make it, back wall bass trap, 180 X 180 X 25cm.

[Wes Lachot]

Originally Posted by kurt

Hi Wes. My CR is 6.5 X 4.94 with 3.10m ceiling. True, I have problems at ca: 35 & 100Hz. I´m about to build more bass traps on the back wall. At the moment there is 100mm with 100mm space 120 X 120 cm bass trap + massive corner traps. I plan to make it, back wall bass trap, 180 X 180 X 25cm.

Kurt,

Those are pretty good ratios. You have plenty of depth to give you the flexibilty to get some distance from that back wall.

Ethan,

You are so right, and we've got that one knocked too, but it's part of our "secret sauce".

-Wes

[Jeffrey Hedback]

Though as you told me the other day Wes, the 3/4 wavelength null can be a killer too!

right! Absolute killer for clients (referring to 75% back), the second order axial mode. In the 20' length example: 56Hz null or essentially the low A on bass guitar. Case again for proper bass tapping.

Back to original post: monitor placement in your size room has to be a compromise between how you excite modes (38% back, 60 degree triangulation) and imaging. Like Frank mentioned, closer than 4' and you're not going to get stereo field. You may get best results by breaking convention. Beyond proper room treatments, the accuracy of your monitoring system is ultimately going to be greatly influenced by speakers themselves: are they ported? What is the off-axis response? Edge diffraction...etc

[farmboy]

Folded,
I can't open your control room drawing (google.png) Trying to translate with live search and can't figure it out. Can anybody help me?
Thanx,
farmboy

P.S. - this is the coolest forum I've ever monitored!!

[kurt]

http://sketchup.google.com/download/

[farmboy]

Thanks kurt. I recently downloaded sketchup and am trying to get up to par with you folks so that I can communicate with you. The file in Folded's first thread says "google.png". When I bring up that file, I enter a language that I do not understand. I tried translating and my computer will not recognize it. I apologize for being slow at this stuff, but I really want to learn. What am I doing wrong?
Thank You,
farmboy

[Lupo]

Originally Posted by farmboy

Thanks kurt. I recently downloaded sketchup and am trying to get up to par with you folks so that I can communicate with you. The file in Folded's first thread says "google.png". When I bring up that file, I enter a language that I do not understand. I tried translating and my computer will not recognize it. I apologize for being slow at this stuff, but I really want to learn. What am I doing wrong?
Thank You,
farmboy

PNG is portable network graphics - a standard image format that should open in most image viewers - including your web browser!

[mobius.media]

pngs attached to this forum won't always load in browser when you click them. here's an embed.

[kurt]

Now I see. It opens here (on Mac), in Safari, Firefox, QuickTime, Photoshop, Preview & the most other apps. Try to download again?

[farmboy]

Thank you folks for your help. I am able to view it! Now I can see what Folded is talking about!
farmboy

[Wes Lachot]

Originally Posted by Jeffrey Hedback

right! Absolute killer for clients (referring to 75% back), the second order axial mode. In the 20' length example: 56Hz null or essentially the low A on bass guitar. Case again for proper bass tapping.

Back to original post: monitor placement in your size room has to be a compromise between how you excite modes (38% back, 60 degree triangulation) and imaging. Like Frank mentioned, closer than 4' and you're not going to get stereo field. You may get best results by breaking convention. Beyond proper room treatments, the accuracy of your monitoring system is ultimately going to be greatly influenced by speakers themselves: are they ported? What is the off-axis response? Edge diffraction...etc

Jeff,

Actually, what Ethan and I were referring to was not the 2nd order axial mode, whose null is, as you correctly state, located 75% from each boundary. We were referring to the 3/4 wavelength null caused by the distance from the listener to the back wall, which is not a modal null, but a boundary interference null. The most commonly referenced ones are at 1/4 wavelength, but they exist (although a bit toned down by distance) at 3/4 wavelength as well, a fact that becomes obvious as you get far enough from the boundary that the 1/4 wavelength null drops into the sub-audible range. But I'm sure you already know this stuff. Just wanted to clear up the confusion - I should have stated it more clearly to begin with.

-Wes

[Jeffrey Hedback]

Ahhh, thanks Wes. I re-read the thread and see what you and Ethan we're bringing forth and yes do agree how probematic this 1/4 wavelength null is.

If you bring this back to the OP with room depth of 11.5' the collective input has certainly helped (and helped Kurt as well).

I think the thing to add is a comment on speakers...today's active monitors rely a great deal on rear porting to extend LF response. But I strongly suggest a sealed enclosure that does not attempt to go down to 40Hz. The 11'-6" x 9'-7" x 8'-6" room "is what it is". After optimizing treatments and placing your ears in best possible location...the variable of speaker type is huge in this space.

So if Folded is tracking drums he will have tough time monitoring kick drum, mic placement, etc...but it is possible to mix (better term might be balance) in a room that doesn't support the lowest octave as our brains have ability to "track the fundamental". Not ideal, but it's far better to have a speaker with a tight and quick LF response than one with abundance of LF falsely exciting the room.

I guess I'm going this direction because the tendancy in such a room might be to undervalue the monitor selection...I suggest it's all the more important. There can be a big difference in this size room between "sounds good" and accurate.

[Folded]

Thanks for all the reply. I'm in the process of trying out different positions. I've just set up as I initially intended (about 38% off the back wall), but I'm getting this deviation between left and right speakers and it's slightly annoying. Also I don't think the response is all that flat neither. (See graph)

I have about 8 bass traps surrounding the speakers (the front wall and sides). Is trial and error the best way to go about positioning myself in the best place?

Folded

(Also attached a picture of the current setup.)

[PaulP]

Originally Posted by Folded

I have about 8 bass traps surrounding the speakers (the front wall and sides).

Have you put the aborbers on the back wall like you said you were about to
do ? The back wall must be pretty close. If you haven't take the three in
the center up front and put them behind you and see what happens.

Paul P

[Folded]

I do have bass traps across the backwall. The only problem is I haven't mounted my bass trap and they are freestanding on the floor.

I have, tried shooting the speakers down the slightly shorter wall and measured the frequency response and it doesn't seem at all different, but it is a bit better this way because I now have access to the windows.

The big problem is I still get this huge 10db difference <100Hz between left and right speakers and the stereo image seems to be heavily tilted towards the right and needless to say it is nowhere near GOOD atm.

More traps? Diffusion? changing the room is not currently an option....