Bass trap question...

[J:son]

Hi!

I'm building a bass trap - the type with MDF-hangers dressed in Dacron.
My question is: On which wall should I place the trap?

Is it better to use an outside wall or a wall next to the rest of the building? In other words, does the trap kill bass frequencies or does it contain them?

Does anyone has any experience from this, or will John have to bare with us once again?


Thanx in advance...

J:son

 

[Brian Grey]

So I take it you really don't understand where or how a bass trap is used. Am I right in assuming that? What a bass trap will do is make the inside of your room sound better by lessening room modes. What that means is... You use bass traps mainly in 90 degree corners. When sound is bouncing around your room it's either going to like the shape of your room, or dislike it. Your goal is to make the sound dislike the shape of your room, because when it likes your room it's going to find out exactly what frequencies will bounce around the easiest and then those frequencies will be louder than the rest. That's called a mode. The hardest of all the frequencies to stop from bouncing around and pissing you off like this is the lower frequencies because they're much longer than high frequencies. And the place the low frequencies are going to love the most and create modes is in the corners. So, what does this mean? It means that when you put your bass trap in the corner it's going to do it's best to make the low frequencies hate that corner, and hopefully in the end you won't have a room mode that supports that frequency.
What does this do for you? Say you're listening to the bass player from your control room. Say you're trying to mix his bass into the rest of the music. You're listening, and adjusting his volume, and it sounds great. Then you take it to your car, start listening, and the first thing you say is "Where's the bass?!" The reason you don't hear the bass is because when you were listening in your control room it had a room mode that made those bass frequencies seem louder than they really were. So when you using your ears and adjusting the volume of the bass you were turning it down, and more than you should have. If you had bass traps, and other foam to help, you would have been able to mix it properly.
The same goes for the room that you're micing the bass. If you're running direct ignore this... If the room that the bass amp is in has no bass traps, the room is going to color the sound. And when you mic the amp, you're going to be micing more than just the sound coming out of the speaker, you're going to be picking up those spikes in the volume created by the room.
Just remember, you're more or less trying to take the room out of the equation.

Later,
-Brian

 

[John Sayers]

J:son - as Brian said put it in a corner but on your rear wall, behind you cos it also absorbs the highs as well and it will kill sounds coming back to you from behind.

cheers
John

 

[Brian Grey]

J:son - as Brian said put it in a corner but on your rear wall, behind you cos it also absorbs the highs as well and it will kill sounds coming back to you from behind.

cheers
John

Yeah, and that too.

 

[kEVINk]

Are the hangers exposed? Some of the schemes on John's site showed them contained within a wall cavity (as in the section through the control room), while another showed them under the monitors with a port at the floor leading to the cavity. Is one preferable over another? does the cavity holding bass traps need to be air-tight, or is this counterproductive?

What can I say, I'm a newbie



k

 

[Brian Grey]

I think you're missing the theory KevinK. You have to understand the theory, and then you can apply it to whatever you want to do.

Bass traps you put in corners are totaly different than ones you put under monitors.

Bass traps in corners keep the reflections coming back at you from the walls behind you. You can either build them into the wall, or do like a lot of people do, just have them free standing. Something you just set in the corner to absorb bass can be moved around, and you can taylor the sound to your liking. Ones that are built into the wall are gonig to be like that for the rest of the time you have your studio.

Bass traps you put under your monitors, or under a subwoofer, and to cut down on early reflections off the floor or your console. With a subwoofer on the floor, the first place the bass is going to reflect is the floor, and unless you've got the correct absorbing material under the subwoofer it's going to sound twice as loud as it really is.

Did you get that at all?

Later,
-Brian

 

[kEVINk]

I think I am using the wrong terminology and it is causing some confusion. The base traps I am refering to (probably incorrectly) are the hanging panels shown in the section thru the control room ceiling and under fully recessed monitors (in the cavity). My confusion was that some schemes showed these in sealed cavities, some with a port. A question further down by c7aus adresses this.


https://homerecording.com/bbs/showthread.php?threadid=22697

The base traps you are refering to would be applied to the surface, inside the room, as I understand it.

It seems I'm using the same word for two different things. If someone could clear that up, I would appreciate it. I apologize for the apparent consternation.

k

 

[Brian Grey]

Gotcha.
John, what do you think? Seems he's getting some ideas from you...

 

[J:son]

Thanx for your informative answer, Brian.

Maybe I'm being a bit unclear with what I'm asking. Most of the things you explained I already know - what I'm trying to figure out is if the bass frequencies will stay in the trap for som time before being killed(damped out), or if they will die as soon as they enter the bass trap?

The reason I'm wondering is that my studio is located next to my living room where, hopefully, the rest of the family like to lead their life as usual(without earplugs, that is).

If the bass frequencies is not killed at once, there is a slight risk that they will travel into the wall behind the bass trap, pass the air cavity and then through the next wall into my living room. Now we don't want that, do we?

I'm talking about my recording room here. Therefor I have no "front" or "back" in the room. In other words I can place the bass trap in which corner I want.

So, is it better to have it on the wall closest to the living room or on the other side of the room(which is on two outer walls)?

kevinK:s question is also a good one. I noticed the same thing when I was surfing around John's (excellent) site.


?-) J:son

 

[Brian Grey]

Yeah I get what you mean now.
What you need is lots of layers of particle wood, or drywall, or MDF, and that insulation John is always talking about inside the wall. To do yourself the best favor, put lots of layers on the existing wall that you say touches the living room wall. Then, put up lots of insulation on the layers you just put up, and then build anothe wall in front of that. Making sure to seal the perimeter of both walls. Giving yourself that dead air space will help a ton, and with the insulation in there it will get a little help.
I guess it's that or 5 feet of foam.

 

[J:son]

Now we're on the same track!

So, where do I put my bass trap?
Close to the living room or as far away as possible?
(Or maybe it doesn't matter?)

Thanx!
J:son

 

[Brian Grey]

Now we're on the same track!

So, where do I put my bass trap?
Close to the living room or as far away as possible?
(Or maybe it doesn't matter?)

Thanx!
J:son

Well, the way I described it, I don't think you'd need the same kind of bass trap John has drawn at his site. The picture that I looked at had more of a false ceiling, and it looked like the back wall also wasn't anything special, so therefore bass trapping was put behind it and that in turn helped the room itself. But the way I described it, I don't think you'd need the "bass trapping," I think just having the dead air space, and I'm talking 6 inches, would be enough. And of course insulation inside of that space to make sure any sound that does get in the middle of the walls doesn't bounce around and vibrate the walls. And the shear thickness of the insulation and it's characteristics will block about 9db of sound.

Later,
-Brian