Is there audible proof that low frequencies are exaggerated in corners?

[Seeker of Rock]

Yes. I just heard it like I've never heard before tonight in a simple drum test through the monitors. I have an electronic drum kit, so I'm setting levels and EQ for each component through the pres (all older Joemeek...they do wonders for the DM Pro kit, thus I use them on all six output channels for drums/drum groups) and hearing the final input through the monitors. So I almost have it down when I decide to walk behind the kit as I'm fine tuning the snare. I notice a "boom", very prominent and everytime I hit. So I take the low down on the input pre (not setting EQ at the board at this point, just tweaking gingerly if something begins to sound too digitally boomy or screechy) and nothing. As I'm back against the wall with the back corner 3 feet away I'm heary this low frequency "boom" on every snare hit. Walk in front of the kit and reach around to hit the snare, it's gone. And this sound was not faint, it was very noticeable. I've seen graphs supporting absorption in corners, but man what an earful I got tonight firsthand!

Coincidentally, that is that last area I have yet to treat, just waiting on some wheat seconds to become available at realtraps to match those in the front corners.
Edit: Come to think of it, I may explore a different realtraps solution, something a little more substantial. I was looking at the Mondotraps about a month ago. Hmmmmmm.
Another edit is I forgot to mention the setup...the back wall has an angled square (diamond type shape) of 4" pyramid foam that covers about 50% of the total back wall sq ft. Also, I have shallow pitched ceilings. Don't know how much any of this had a part in it, but the "boom" seemed to travel along the back wall from side to side, extending out (in the center between the two back corners) about 4 or 5 feet before it completely disappeared audibly.

 

[Innovations]

Low frequencies are not 'exaggerated' in corners per se.

The volume of air in a room has certain resonances, much like the air in the body of an accoustic guitar.

The lowest resonances wound occur in the longest column of air. What is the longest dimension in a room? It is between one corner and the diagonally opposite corner.

 

[Dani Pace]

Bass traps were the best thing I added to my studio (practice room.) Mostly I use my room to record my band's practice sessions, live, all at once. Everything was comming out somewhat boomy sounding, volume didn't seem to matter, it was still boomy. After adding bass traps to the room the boominess all but dissapeared. I can't give you any specs on the difference (I don't have any) but I can say it made a major difference in what I was hearing, both for practice and for recording. You said you are using electronic drums, we use acoustic drums. The cymbals sounded harsh and sometimes clipped, I added a cloud over the drums and this worked wonders in combination with the traps.

 

[Seeker of Rock]

Yeah, those back two corners are the only places I haven't treated yet and man is that low "boom" audible. I know people have their graphometers and gidgets that technically tell you what's happening, but to hear it so crystal clear in the "boom zone" was something I wasn't expecting.

 

[pandamonk]

Walk into an untreated corner, while music is playing, and you will always(in my experience)hear it get bassy.

 

[Seeker of Rock]

Yeah, but this was like a low frequency shadow on the snare hits, and I was controlling randomly when the snare hits occured. A very revelationary moment, hearing this. I may listen again from back there and, since I know it exists, see if I can pinpoint where in the vertical plane the lows are congregating. I guess, short of a meter, this is the best way to figure out how much vertical trap I'm going to need in those back corners. Oh yeah, I've got some leftover Foam-by-mail...maybe I'll pin some of the 4" pyramid stuff in the corner and see if it does anything, then I've got a few pieces of leftover Auralex I could pin in there afterwards. Even though they are catching mids and highs, there should be a little bit of absorbtion in the lower mids that would be audible.

 

[pezking]

It's important when treating rooms to understand why things like this happen, and to understand how the various acoustic treatments will affect it.

There are two vital components to a given wave: its velocity, and its pressure.

The human hearing responds to the pressure components of the wave. Where is the pressure of a wave at its maximum (and thus when will we hear it loudest?)? The answer is when the velocity is minimum, i.e. at an antinode. When (in practice) is the velocity at a minimum? When it changes direction. And of course that is when it is reflected off a wall.

Porous absorbers respond to the velocity component of the wave. So the absolute edge of the room, or corner of a room is a really bad place to put it. Instead the absorber should be placed a 1/4 wavelength (of the frequency you wish to absorb the most) away from the boundary.

Hope that helps somewhat.

 

[bpape]

To a point that's true - if you want to treat a minimal set of frequencies. However, if you want a more broadband approach, you use thicker material and a little spacing so it doesn't filter so badly.

It's not only the placement in relation to the boundary but also how much of the wavelength you can get inside the absorbtion at one time.

Bryan