Sad Discovery

[Johnny08]

So I'm mixing a song. I mute the vocals and find out that whenever a sine lead sound plays a certain note, it attenuates greatly in volume or perhaps even cancels out. I find out that the note is a B3. I walked to the side of my speakers could hear the note fine. I wanted to turn my desk over! I'm thinking, how many mixes could I have mixed better had I know this earlier?!

 

I thought I had my speakers set up according to the phantom image rule. I adjusted them a little and could hear the note better from my chair. However, I am nervous now. Is there a poor man's way to test my room to find other problem spots?

[fader8]

Is there a poor man's way to test my room to find other problem spots?

 

Yes. But there aren't many poor man's ways of fixing it.

 

You have a room mode, aka standing wave. Step 1: Post your room dimensions.

[Johnny08]

 

Yes. But there aren't many poor man's ways of fixing it.

 

 

Crap. What are the unlimited budget ways of fixing standing waves? I get a good bass response from the krk's/room that relates well to other speakers, and the tucked in space is pretty dead to room acoustic; so I don't need bass traps and a lot of acoustic treatment. Just want to make sure I'm hearing from 20 to 20.

[biff_larken]

Nice setup, but i was under the impression that bass traps were ALWAYS a good idea....

[fader8]

Those two walls facing each other flanking your workstation is likely the culprit. Is that 8 or 9 feet across? That would give you a problem around 65 and 130Hz-ish. Is there a flat ceiling above, or does it peak?

 

You'll have to measure the response somehow to find out how deep the whole (node) in the frequency response is. That will determine if you can get away with store bought broadband bass traps or something custom for the specific problem frequencies.

 

It would likely help if you could move your rig out of that hole though.

[nikkik]

At a minimum, bass traps.

I love Ready Acoustics stuff, but there are plenty out there, and you could make your own.

 

Next, IMO, would be diffusion, and doing the "mirror trick" and using the appropriate materials to kill those immediate reflections.

[Johnny08]

Those two walls facing each other flanking your workstation is likely the culprit. Is that 8 or 9 feet across? That would give you a problem around 65 and 130Hz-ish. Is there a flat ceiling above, or does it peak?

 

You'll have to measure the response somehow to find out how deep the whole (node) in the frequency response is. That will determine if you can get away with store bought broadband bass traps or something custom for the specific problem frequencies.

 

It would likely help if you could move your rig out of that hole though.

 

There is a flat ceiling above, but the B3 note on the sine sound is around 440hz. I heard something a long time ago about using pink noise to test a room. I was hoping something like that would at least tell me what I am missing, but I have absolutely no idea how to do it.

[Johnny08]

At a minimum, bass traps.

I love Ready Acoustics stuff, but there are plenty out there, and you could make your own.

 

Next, IMO, would be diffusion, and doing the "mirror trick" and using the appropriate materials to kill those immediate reflections.

 

That sounds cool but

 

How do you build your bass trap?

 

Mirror trick?

[Johnny08]

Nice setup, but i was under the impression that bass traps were ALWAYS a good idea....

 

Thanks, but I thought that bass traps were to used only if the bass in your final mix, when play on other speakers, was exaggerated or not translating well.

[dkgross]

First thing I'd do if that was my room is get some speaker stands and spread them puppies OUT, past the edge of your desktop, and angle them in towards you more. I'd also get some sound foam stuff for that back wall, right behind the speakers.

 

and get JBL LSR's that you can tune to the room

[nikkik]

At a minimum, bass traps.

I love Ready Acoustics stuff, but there are plenty out there, and you could make your own.

 

Next, IMO, would be diffusion, and doing the "mirror trick" and using the appropriate materials to kill those immediate reflections.

 

That sounds cool but

 

How do you build your bass trap?

 

Mirror trick?

Do a search for "DIY Bass Traps" or just look for Ready Traps (they sell bass traps and other acoustic treatments, plus you can simply buy the premade slip covers, and stuff your own Owens-Corning fibre in there). The Ready Traps site also has tons of info. Ethan Winer also has his line, and has tons of info. Google away on those... sorry I do not have links handy,

 

Mirror Trick is having someone hold a mirror, and walk the edge. Sitting in mix position, when you see the monitor n the mirror, that is a reflection point that most likely will need treatment.

 

Throwing the monitors on stands would be an excellent idea, but I would do so, leave a couple/few feet between them and any wall, and then slide that desk backwards. Then, figure your distance from the monitors. Once you have that, simply form an equilateral triangle, and then sitting in the main mix position, angle them accordingly. One way to do this is to set everything, have someone sit in your chair, and then use a tape measure to align it all. If alone, you can use a mic stand or something to approximate you in the main mix position. If you can get close to 3' away and still have the monitors a couple/few feet from any wall, great! For that size room, it would be rough, but without measurements, would be a nice figure to shoot for. 28-36" should be cool enough, but at least 24" would be nice. Less, and you will only have a very tight field to work within. Biggest starting point is to maintain that equilateral triangle (equal sides=equal distances; from head to monitor, monitor to monitor; 5.1 would require additional considerations...).

[fader8]

There is a flat ceiling above, but the B3 note on the sine sound is around 440hz. I heard something a long time ago about using pink noise to test a room. I was hoping something like that would at least tell me what I am missing, but I have absolutely no idea how to do it.

 

B3 is 246.9Hz.

 

OK, stop guessing at solutions until you've nailed down where the problem is coming from. Your space is small so it's not going to be tough. You need two things:

1. An omnidirectional microphone.

2. A tape measure.

 

Measure the floor to ceiling dimension and the wall to wall dimension. Post back with that info and try to find an omni mic. Once you have these things in hand I'll tell you exactly what to do. This isn't hard but you can't skip this first step as everything else depends on fixing the low end first.

 

Post those dimensions!

[maninthedark30]

At a minimum, bass traps.

I love Ready Acoustics stuff, but there are plenty out there, and you could make your own.

 

Next, IMO, would be diffusion, and doing the "mirror trick" and using the appropriate materials to kill those immediate reflections.

 

That sounds cool but

 

How do you build your bass trap?

 

Mirror trick?

 

It's lengthy, but worth the read:

 

http://www.soundonsound.com/sos/feb06/articles/studiosos.htm

[fader8]

Mirror Trick is having someone hold a mirror, and walk the edge. Sitting in mix position, when you see the monitor n the mirror, that is a reflection point that most likely will need treatment.

 

This is good advice, as usual, from Nikki. But keep in mind that it's step 2. Early reflections have a greater impact on frequencies above 7-800Hz. If you have low frequency problems as your describing, those are caused by room modes which also have an impact at higher frequencies, but to a lesser degree. The point is that you have to deal with the low end first.

 

While bass traps are the solution to room modes, there are two approaches, broadband vs. narrowband. Broadband traps have to be huge to be effective, but their design isn't critical. Narrowband traps can be much smaller and highly effective, but if you don't build them correctly they can cause more problems without solving the ones you have.

 

With that said, we're still clueless as to what's happening there until you make some measurements.

[Johnny08]

First thing I'd do if that was my room is get some speaker stands and spread them puppies OUT, past the edge of your desktop, and angle them in towards you more. I'd also get some sound foam stuff for that back wall, right behind the speakers.

 

and get JBL LSR's that you can tune to the room

 

JBL LSR's are sweet but out of the question right now.

 

I actually have a set of speaker stands, but placing them on the sides of the desk puts them too close too the side walls, and gives me and my stomach little room to get behind the desk.

 

After reading all the great posts so far, I am thinking about pulling the rig out the hole, which would make room for the stands.

 

 

 

 

 

 

 

 

 

 

Do a search for "DIY Bass Traps" or just look for Ready Traps (they sell bass traps and other acoustic treatments, plus you can simply buy the premade slip covers, and stuff your own Owens-Corning fibre in there). The Ready Traps site also has tons of info. Ethan Winer also has his line, and has tons of info. Google away on those... sorry I do not have links handy,

 

Mirror Trick is having someone hold a mirror, and walk the edge. Sitting in mix position, when you see the monitor n the mirror, that is a reflection point that most likely will need treatment.

 

Hmm, that's cool and doable. I could get my wife to help me with that.

 

 

 

 

 

 

 

 

 

 

OK, stop guessing at solutions until you've nailed down where the problem is coming from. Your space is small so it's not going to be tough. You need two things:

1. An omnidirectional microphone.

2. A tape measure.

 

Measure the floor to ceiling dimension and the wall to wall dimension. Post back with that info and try to find an omni mic. Once you have these things in hand I'll tell you exactly what to do. This isn't hard but you can't skip this first step as everything else depends on fixing the low end first.

 

I'm just getting started and only have a few cardioid pattern mics. I am, however, going to take your advice and pull the rig out the hole. It seemed like a cool space at first; I did not think of it as being in a hole, but now that you mentioned it... Ding... I see that it is.

 

 

 

 

 

 

 

 

 

 

It's lengthy, but worth the read:

 

http://www.soundonsound.com/sos/feb06/articles/studiosos.htm

 

Thanks!

[nikkik]

"Shooting the room" is a great idea, but sometimes not necessary f an omni and spectrum analyzer are not available (own, lease, borrow). If you get the monitors up on stands (the better decoupling, the better..I LOVE my stands; removable spikes, hollow column which can be filed with shot or sand), and then get the desk situated well, you can go form there.

 

Fader- yeah, bass traps can be a crap shoot in a way. I have the Ready Trap broadband traps (6 of them in a ~12.5' x ~14' x 7'10" monitoring room). It is just a smidge enough off squared to be a doable room...luckily...

 

If you could get those dimensions posted, and then post a nice pic shot from behind the desk facing toward the back wall, that would help immensely. WIth that couch, some broadband, and then some high freq foam on the early reflection areas, and probably some "over mix pos" diffusion, prolly be doing pretty well.

 

You want live, but not with standing waves and other nasties. IMO..

[Johnny08]

8ft floor to ceiling and roughly 9 1/2ft wall to wall.

 

I have the stands now. Here are more photos, including one showing the ceiling.

[nikkik]

The first thing I would remark on is the placement. The equilateral triangle thing is important. If you spread them that wide, you *need* to set the mix position back that same distance. So, if they are 4' apart, then you would sit 4' back from each monitor, forming a 4' x 4' x 4' triangle. If you simply place them wide and aim them in, you distort the field the wider you go without compensating by setting the mix position back further. I would say either place them behind the desk, and then get the triangle going, or slide the desk back about 8-16" and THEN place them behind the desk and finalize placement by using a tape measure.

 

One method I have used is to figure the rough position, then decide on distance. Once i have that figure, I will tie a string to a mic stand, extend the stand to about my ear height, and then place it so the top of the mic stand is about where the center of my head would be while mixing. With center of room marked, I can then move the monitor position in or out based on half that string length from the center length. Then adjust either the distance from front wall of monitors, or move mix position back further or closer to get the other two legs of the triangle set. With the desk closer to the monitors, obviously this means you will be closer, and thus the two legs originating from your head will be shorter, making the distance between the two monitors will decrease. Slide the desk and your mix position back a bit, and the monitors will spread the same amount. Personally, I like to get within .5" if possible. A bit strict, especially considering that when simply listening to a mix most of us will ease back a bit, thus destroying that "perfect" triangle monitoring setup. However, I see the critical listening being during the mixing process, and once you slide back and relax and simply listen, the position becomes less critical, as most of us want to get an overall "picture" of the mix, and hope it will sound great across the greatest number of playback mediums. If sliding back a bit destroys the mix, what will a car stereo do with it?

 

Pfft on me for babbling yet again...

[fader8]

8ft floor to ceiling and roughly 9 1/2ft wall to wall.

 

Good.

 

The 96" dimension means you'll have your first axial mode at 71Hz, second at 142Hz, third at 213Hz, etc, with diminishing effect as you go higher in frequency, so these 3 are the ones that really matter because it's the really low end that's hardest to absorb.

 

At 114" the first axial is 59.5Hz, then 119Hz, then 178Hz, 238 . . .

 

Depending on where your ears happen to be within that space, you'll either get a big hole or a big bump in the frequency response at those frequencies. This is the anti-node and node of the standing wave, respectively.

 

So now, from your listening position, fire up the test oscillator and dial in those numbers. sweep aound them too and note the effect you hear on the loudness of the tones. Once you get an omni mic plugged into your interface you'll be able to look at what's happening in Logic's multimeter or other analyzer plug-in. Then you'll have some real +/-dB numbers to work from and it'll be a LOT easier to determine what kind of bass traps you'll need.

 

Note that loudspeaker placement has almost nothing to do with this problem, with the exception that if you put them closer to the wall the problems will get worse.

 

What worries me are those big angled walls. If you're finding problems at frequencies not listed above, it means you have some oblique modes occurring which are very difficult to calculate and predict. All of this might just point to getting that rig out of that hole!

 

If the bumps and valleys in the response are big enough, it could mean that the only way to solve it it any meaningful way is to put traps in that would nearly fill that little space, LOL. "Hey, we solved the problem but there's no place to put the gear now!"

 

From a high frequency standpoint, your ceiling is problematic. Even though the flat, level portion is small, any reflections are naturally amplified by that "horn" which is aimed dead smack at your listening position. Great. You would definitely need some thick absorption there.

 

So, good luck with it, but in all honesty be prepared for that little space to be a hopeless cause.

[Johnny08]

Thanks guys! This is great information and some pretty technical stuff; thanks for breaking it down for me. Okay, now it's time to apply all this. I will report back asap with an update.

 

Thanks again.

[fader8]

Thanks guys! This is great information and some pretty technical stuff; thanks for breaking it down for me.

 

Your welcome. No problem really. Just a reminder, Nikki is not, nor shall she ever be as far as we know, a "guy".

[nikkik]

LOL Fader! Yeah, even if I try the drag king thing, my boobs get in the way..lol!!!

 

One thing I forgot to add in there was that if you do not have an omni, a really cheap, non-tech way of checking your room if you have god ears... simply use a tone generator and sweep it. There will be bumps and valleys you cannot hear, but an obvious one should "pop" for ya. Also, a decibel meter can help. I would say it is a must to calibrate a monitoring system, and one from Radio Shack that would do the job would run about $20, so it is a good investment IMO. Or, find a live sound company in the area, and ask to borrow theirs or rent it. Or, lease from a shop. Live guys should always have one... at least they used to..

 

With that ceiling...lol... it is an interesting one, to be sure. On one hand, it might deflect and such in a good way; or, it might be reflective in a bad way, PLUS add nice spot that is as bad as or worse than a corner. Just glancing at that room, I would guess 8 broadband traps; front corners, angled front corners, both rear corners, direct rear ceiling/wall corner, and a hanging one directly above the mix. Sub a hanging diffuser with some absorption capabilities for that last bass trap possibly, but without an acoustician, it is a hit of miss thing I think.

 

Just curious- how is the view out fo that window in front of the mix position? If it is a nice view, enjoy it, at least every now and then. I wish I could find this pic of a control room for a project studio this guy has; it has tons of floor to ceiling windows, overlooking woods and a pond. Absolutely beautiful, and supposedly an excellent sounding room despite seeming to be a reflection nightmare.

 

BTW- Here is a great forum for studio design and set-up and stuff. John Sayers is pretty well known in the project studio realm. Measure out your room, make a nice graph paper drawing and scan it in, and then add your pics, and you would probably get even more advice there. Guys over there that live for this stuff.