NEarfield Monitor placement for 1 eared mixer

[brianjanthony]

I've lost (at least the forseeable future) much of the hearing in my left ear due to infection. So, I'm desparately trying to redo my control room so that I can mix with 2 speakers on the right.

So I got brave and rearranged the setup to have my 2 nearfields on the right. To my horror, I lost all bass frequencies and have all kinds of nuts phase cancellations going on.

The speakers are in phase. And the CR is pretty well treated with traps, foam, diffusion, etc. Never had a problem before.

All of a sudden, (remember, both speakers are pointing towards my right ear), 150 and below DISAPPEARS. I can hear the bass if I am beside the speakers (literally, I can stand right next to the darn things and hear the full bass I remember hearing before all this crap started). I can hear the bass at the back of the room. The only place I hear NO BASS at all is in my general listening area.

It got me thinking, how do I know how far I should sit from the speakers? I always read that its supposed to be an equilateral triangle. That means if I put the speakers 2 ft apart, I should be 2 ft out. (And when you put 2 KRK 7000s on one side, they kinda have to sit pretty close together, or its too hard for me to hear a cohesive image with one ear). Is it the fact that I only have one ear to work with that's making it harder for my brain? Or shouldn't that factor into this issue? How far back to you guys sit? (I have no console, so that's never been a guide for me.)

How long does it take 60Hz and 150hz to develop? Is there a "minimum" distance you should be from the speaker (for example, maybe you should always sit AT LEAST 3 ft away or something).

I've been mixing in my humble little room for 4 years now... enough to make a living at it. But all of a sudden, I feel like a flunkie from Acoustics 101 with a degree in crappy CR setup. I guess I suffer from changing too much at once. Without being able to hear like I used to, I'm haveing trouble making the judgement calls I used to. And with moving the control room around, I'm not sure having 2 or 50 ears would change the acoustic nightmare I now have. Of course, the easy answer is "CHANGE IT BACK!!!" But that really won't work for me now...

To boot, the change was so drastic that when a client stopped by, he asked if my speakers were blown.

Anyway, hopefully someone can offer some insight or point me in a good direction. I've done web searches for this stuff. Nearfield Placement is covered extensively everywhere. But I think my case is a little out of that normal line.


Sorry to ramble.

Any thoughts are appreciated...

brian

[accession]

Hi mate,

So sorry about your hearing.

Forget your left speaker for the moment, with the right speaker in place, do you still have the lack-of-bass issue?

I suspect the problem was there all along, and the left speaker was carrying the right speaker's low-frequency output without your being aware all this time.

So then, perhaps its a standing wave issue, and you're sitting in the dead spot, while in front of you and behind the bass booms. Could be?

You asked:
How long does it take 60Hz and 150hz to develop? Is there a "minimum" distance you should be from the speaker (for example, maybe you should always sit AT LEAST 3 ft away or something).

Like an ocean swell, it doesn't matter whether you're a few kms off shore, or in the middle of the Pacific Ocean, the waves will ride past. The sound develops at the speaker diaphragm. That's all good and well, however, if you're out at sea, or setting up a PA on an open, outdoor playing field.

inside, problems occur when the waves hit a surface (ie. your rear wall), then rebound back on themselves. If the frequency of the waves, that is, if the wavelength itself is precisely double your parallel wall length, it'll rebound and reinforce (double the energy) right in the middle, and be dead at each end. This will be (one of) the fundamental frequency modes of your room. As the frequency multiplies (ie. harmonics), so multiplies the number of boomy/dead spots.

Looking from one end to the other
Fundamental = Dead-Boom-Dead
1st Harmonic = Dead-Boom-Dead-Boom-Dead
2nd Harmonic = Dead-Boom-Dead-Boom-Dead-Boom-Dead-Boom-Dead
...and so on, with the distances between the dead areas and boomy areas obviously being spaced closer together the higher up you go (unless your walls are moving closer/further apart!).

So how long's a 60hz & 150Hz wave?

Bear with my metric...

344 metres-per-second (speed of sound) / 60Hz = 5.73metres wavelength
344 metres-per-second (speed of sound) / 150Hz = 2.29metres wavelength

I'm going to take a punt and say your problem is with the first harmonic and you're sitting close to the middle of the room???

That being the case, say the fundamental of the room is 40Hz, then the first harmonic lies at 80Hz which is prime bass loss if you're sitting in the dead spot!

The next multiple (2nd harmonic) will be 160Hz and you might notice slightly boomy spots scattered about the room. It's gets less noticeable as you move up the scale.

I was going to guess your room's dimensions, but that'd be futile without knowing the exact frequency that's causing grief.

Anyway, so what's the solution?

Move your listening position out of the dead spot, move your monitors to somewhere else in the room, or install bass traps to soak up the energy before it gets to rebound. Remember sound moves 360degrees, up and down, left and right, so your floor-to-cieling dimension can cause havoc too.

Hmm... wondering what in that waffle actually made sense? And it's been a while so I hope my maths and placements were spot on.

[brianjanthony]

My room is unfortunately 14ft wide x 10ft long x 7 ft high.

Looking at it, I am actually sitting in pretty much room center. I moved the monitors to the long wall, which is treated with 2" mineral fiber baffles covered by 1" auralex foam. So the monitors are on the long 14" wall. And I end up sitting about midway in the 10ft area. The wall parallel to the monitors isn't so condusive to foaming. But I do have (2) 2x4 3 inch mineral fiber baffles on that wall.

The biggest problem freq I noticed was 135 HZ. give or take a few Hz. If I stick my head at speaker, I hear it. By the time I move into my listening area, the frequency is entirely gone, and I hear it echo more from the other walls than direct sound. Am I making sense?

And if I stand up, I hear the 135Hz just fine. RRRRRRRRRRRR!!!!!

It's just maddening that this all comes up now after like 4 years. Maybe if I indeed change it back the way it was, with the monitors on the short wall, it will be better.

To move my listening area, I'd have to be like 4-6 ft away from the monitors, which may be good. That's one of my biggest questions. Otherwise, I'll be pretty much on top of them (like 2-4 ft) and I don't know how good that is.

I'm trying to go no louder than 83db when mixing now. No matter where I sit.

Thanks so much for the input!

Brian

[accession]

RE: 135Hz.

Yep, I had the *opposite* problem at my last place. 132Hz would boom. Kick drums and basslines would simply blur into one, no definition. And I disccovered that *after* I told someone their lowend was as muddy as hell. Then I put headphones on... ooops!

I'm guessing (one of) your room's fundamentals is 67.5Hz, and your head's sitting smack in the middle (either wall to wall, or floor to ceiling) and copping the 1st harmonic (135Hz) node.

See http://www.glenbrook.k12.il.us/GBSSC...es/u10l4c.html for nodes and antinodes. Where the wave appears to be standing still is where your head is, and where the wave is wave is moving the greatest is the boomy locations each side and around the room. Sort of makes sense what I mean now? I'll have to dig up the graphic that lets you type in the freq and see the animations for each of the harmonics.

Anyway, I'll have some more time for nuttin' this out over the next few days...

[pat yacono]

My good friend lost hearing in one of his ears in a surgery. He was always a great mixer, and I think he is even better than he was with two ears. He might have a lot of insight for you. His email is [email protected] . Great guy.