My room's got issues!

[CurtZHP]

I can't believe I've never noticed this before. It seems lately that my mixes from home are sounding bass heavy when I listen to them at work (radio station). I was chalking this up to the rooms at work (some not much larger than a good sized closet!). I even listened to them on a pair of NS-10's we have here. I mean - if it sounds good on them, it should sound good anywhere, right?

It's not necessarily every mix either. Just some of them sound muddy outside my room. So I set to poking around a bit. First a little basic info about my room. It's 15' long with a 7' ceiling. The width of the room varies because the right wall is at a slight angle, so it's 12' across the back and 11' across the front. The door is halfway along the left wall. Each corner of the room is straddled with a 2'x4'x4" acoustic panel consisting of a thin wood frame filled with mineral wool and coated with cambric. Two similar panels are attached to the ceiling in the middle of the room about one foot apart. Two more are straddling the angle between the front wall and the ceiling. The front 1/3 of the room is also treated with foam panels attached right to the drywall. The middle five feet of the back wall have shelves attached for models, books, etc. Sort of a "poor man's diffuser."

The monitors are Event 20/20's on individual stands, powered by a Crown D-75.

There's a picture of it on my website: www.zerrohouseproductions.com.


Anyway.....
Running 100Hz tone (what the console had handy) through the speakers, it seemed like the left channel was louder than the right. Running the tone through each speaker individually confirmed this. Not sure why I thought of this, but I got my voltmeter out and while the tone was running, I checked the AC voltage at each speaker. The right side was actually lower, so I bumped the output level on that side to match.

The right side was still sounding lower at 100Hz. I checked it at 440Hz and it was still lower but not as much. 1KHz seemed fine as did 10KHz.

I dragged out the old sound level meter and placed it in the mix position. I measured as much as a 6-8dB difference between left and right at 100Hz!

At this point, I started moving things around. I dragged my 2-track machine (just to the right of the mix position) to the back of the room. I moved the desk, the equipment rack, etc. The best I could do was get the loudness gap smaller - about 3-4dB. But I couldn't eliminate it.

There's definitely a wicked null on the right side of my room around 100Hz. I guess the next step is to take some serious measurements and see if I can clean up this mess without making a bigger mess.

Any thoughts?

[darryl]

Is it possible that the bass difference is coming from the speakers themselves? Have you tried swapping the speakers and seeing if the increased volume switches sides too?

[Snarl 12/8]

http://messageboard.tapeop.com/viewtopic.php?t=77096


http://messageboard.tapeop.com/viewtopic.php?t=77077

[CurtZHP]

Darryl, yes I swapped speakers. I even turned my back to them to make sure it wasn't because I was going deaf in one ear. Still a null on that side.

Snarl, sounds like you had the same exact problem. I downloaded REW and I'll be working on the room starting tonight.

Stay tuned!

[Snarl 12/8]

Snarl, sounds like you had the same exact problem. I downloaded REW and I'll be working on the room starting tonight.

Try to make it through the middle 40 minutes of that Hodas thing. You have to read between the lines (I think all of those guys have ADHD really bad - they never quite make a clear point) but I think he sortof outlines a strategy for figuring out your room.

[CurtZHP]

That's definitely on the agenda for tonight.

[CurtZHP]

Well, so far things are disastrous. The reason for the null at 100Hz turned out to be the simple fact that the width of my room -- 11ft. -- just happens to be the wavelength of a 100Hz tone. I also found a bit of a dip at 160Hz -- which happens to correspond to 7ft, which is -- you guessed it -- the height of my room. Looks like I can also look for trouble at 76Hz as well (the length of the room).

I also need to shorten my speaker stands by about four inches, and drag the desk about 12-14 inches more away from the front wall.

I fooled around with it a bit tonight. The puzzling thing is that no matter what I do at what frequency, it always seems to be the right speaker that's softer. I've switched speakers, so I know it's not a tired driver, and I've verified that the amp is sending equal signal to both.




It's stuff like this that makes me wish I'd stuck around my dad's upholstery shop.

[Snarl 12/8]

I honestly believe no room is perfect and no room is unworkable. It might be more work than you want it to be, but that's a different story. Get it as best you can via speaker placement and then start investing in the Owens Corning 703. Every single fucking thing is life is a compromise of some sort.

[CurtZHP]

On a somewhat encouraging note, when I run pink noise through the speakers and check the meter, I read the same on both channels, for what that's worth.

And the mixes that sounded normal still sound normal.

I'm not looking for perfect, but I need to be able to trust my room.

Tomorrow, I'll dive into REW and see where that gets me.

[JWL]

Is your room symmetrical? Can you post a diagram of how it is set up?

[CurtZHP]

JWL, that's part of the problem. The room is not completely symmetrical. The room is 14'9" long. The back of the room is 11'6" wide, and front of the room is 10' 11" wide. While the left wall is square with the front and back, the right wall is angled slightly, explaining the width discrepancy. The ceiling is 7'3" high.

To further complicate matters, there are soffits along the top of both the front and back walls, housing HVAC ductwork. These soffits are 1' high and about 17" deep. They run the width of the studio.


Today, I shortened my speaker stands. This solved two issues: 1) it eliminated having the woofers located exactly center between floor and ceiling, and 2) it put the tweeters at my ear level.

I spent part of the day moving speakers around, as well as my corner absorber panels, and even tried moving a couple other panels in the first reflection zone.

No matter what I did, at between 100 and 250Hz, the left speaker is always louder than the right speaker, by as much as 5-6dB. The only thing that made any difference was putting the right speaker on the desk right in front of me! (Obviously NOT a workable solution.)

The next step is to remove the equipment rack, located to the left of the left speaker. I've moved it about 18" away from the where it was, but now I think I'll take it out of the room just to see what happens. At this point, the whole studio is basically upended anyway, so.....

[CurtZHP]

Last night, I had a little success for once! I finally found a spot where the right speaker sounds good at low frequency. Turns out it was only about an inch(!) from where I just about gave up looking. Got everything centered up and did some tests with tones from 40Hz up to about 400Hz. There were variations to be sure, but both speakers were never more than a few dB apart. So, it looks like I'm getting somewhere.

The bass in the room still feels a bit lacking. Maybe I'm just expecting too much for the level I monitor at. Or maybe I still have work to do.

More tests!

[Gregg Juke]

No question that trying to get it right is good Curt. But maybe, your room is your room, and at some point you'll have to adapt?

Have you thought about a few more sets of speakers to reference on? A good reference CD to check mixes with? A nice set of headphones (to compare, not as exclusive "mixers," before somebody hollers at me)?

A square room is a square room, and parallel walls are parrallel walls... I'd hate to see you lose your mind, like that guy who tried to play Rachmaninoff's 3rd...

GJ

[CurtZHP]

Well, fortunately, I don't have a square room. (I know that's a losing battle to begin with.) I am starting to formulate a theory or two that may lead to some improvements with a minimum of bloodshed.

I realized that the right wall is not insulated, while the front and left walls are packed with insulation. The rear wall is solid concrete backed by Planet Earth, so that's not going to resonate. But the right wall is just studs and drywall with an air gap in front of more solid concrete. Could it be resonating, and that's where part of the trouble lies? Fortunately, I do have access to the space behind the drywall, so if need be, I could stuff it with insulation.

I've also discovered that I never properly addressed first reflection points for either speaker.

I've also gotten my hands on a few things to aid in testing the room properly.

I also borrowed a different set of speakers, just to see if that accomplishes anything.

[radkins]

You should try building a trap on the wall in question. It worked in my recording studio