Axiom Home Page Forums General Discussion Home Theater Bass Traps

While trying to keep myself busy so as to not go crazy waiting for my speakers to arrive, I thought I would look into a topic that has intrigued me, but never really understood.

As I'm reading through a number of websites, I kind of get the feeling that there's a lot of really bad advice out there. Acoustics is a VERY room specific topic, so I'm not sure where to start. Being the astute newbie that I am, I've turned to the Axiom message boards.

I've run a mode calculator on my room and there are some frequencies quite close together (between ~200Hz and 500Hz), so I'm making an assumption that doing something about this would be a good thing. I've seen some people show graphs of their room's actual frequency response. How is this done? I'm not too keen on buying equipment for it, but spending a day with my Radio Shack SPL meter, a pencil, and a notebook is not out of the question.

Here's what ModeCalc came up with for me:


From what I've read on other websites about some of the DIY bass trap designs is that they typically work in the 250-500Hz range. Perfect!

Now, before I go off and spend a bunch of time and money playing with fiberglass insulation, I'd like to hear what you guys have done. I know I've seen a picture of someones spectacular looking room with some very nice floor to ceiling corner traps. This is what I have envisioned for my room, but I'm not sure that particular design would be appropriate. I'm not terribly concerned with the making of the traps (I'm pretty handy), rather I'm concerned with the proper design with an eye out for WAF. Throwing up a bunch of 4" thick panels on the walls is going to drive my WAF waaaay down. Having some really nice looking corner traps that have the added benefit of hiding some of the cabling in the room would actually boost WAF.

Hmmm... I wonder if I could use movie posters with some nice framework to disguise first-order absorption panels. Not specifically on topic, but it just popped into my head.

First comment is that your room dimensions seem pretty good, ie the modes aren't anywhere near as "bunched up" as they are in some rooms.

Bass traps seem to be most effective in the corners so that's another benefit of the corner traps. A couple of the members here have made some very nice corner traps -- the pictures you saw were probably posted by Sirquack.

You can get software that will do automated response measurements by generating tones and measuring the mic input, but I think most of us just use a test CD, an RS SPL meter and a spreadsheet.

Do you recommend any particular test CD? I have the Avia DVD, but the test tone sweeps were much too fast for me to read the meter, record the level, record the frequency, rinse, repeat.

Ah ha! I found the post where Sirquack (with some Excel help from yourself) built a Superchunk Bass Trap. Haven't read it all yet though.

The most popular one is probably the free download from RealTraps. It only goes up to 300 Hz but most of the exciting room response issues happen below 300 Hz anyways.

I purchased a nice test CD from Rives... one of my friends borrowed it... so I'm using the download from RealTraps ;(

I have a few pictures on my website during the construction and building of my bass traps and first reflection wall panels. I used Owens Corning 703 2ft x 4ft material which is a popular product used by many.

Yes, I think if you placed a reflective material on the front face of the panel, it would reflect the higher frequencies, the once you want to absorb.

I used 2" Owens Corning 703 material within the wooden frames I built. There is actually a space between the wall and the material that forms a void. Many people, like Real Traps, recommends that you space them off the wall, the more the better results. That is why I included my spacing within the framing.

This page on my website has some pictures of building the wall panels.

http://porterplex.googlepages.com/constructionpics

although don't build a cross member like Randy did, it is not as effective as a full open back of the trap, sorry randy

Bleh, the wife nixed the bass trap idea. We have an agreement on this project where I get to spec out the technology and she is in charge of the interior decorating. Both of us have veto power over the other. To avoid an impasse, we both must pick our battles carefully.

The good news is that after I pulled down RoomEQWizard, I realized that it'll take me a couple years of studying to get it set up to measure my room (much less make any sense out of the graphs), so I won't really know how good or bad my acoustics are for quite some time.