My homemade bass traps

I've finally decided it was time I sorted out my studio, acoustically that is, and in true FBB fashion the object was to get the results I wanted as cheap as possible.
 
First thing I did was check the room actually needed treatment, just in case it was acoustically perfect, of course it wasn't - Thanks to bitflipper and his excellent thread about DIY poorman 's room treatment (http://forum.cakewalk.com/tm.aspx?&m=1495170&mpage=1) - obviously a man after my own heart.
 
Unsurprisingly there was all sorts of peaks and troughs especially in the bass end which my ears had already told me by listening to various sine waves and stepped sine waves. My speaker position isn't perfect but it's as practical as it's going to get for now so I'm working under limitations rather than ideal conditions.
 
My brief to myself was simple, due to a variety of reasons any bass traps had to be relatively light, stackable, easily moveable, capable of being hung if needed, not too ugly and not too big either. After much web searching I decided to buy acoustic tiles for the higher mid and high frequencies, and make my own bass traps. None of the homemade plans I found really suited my needs so I decided after collating lots of information to design my own.
 
Result - 8 bass traps for about £50 - bargain. To cut a very long story short I made wedge shaped boxes 60 cm tall and 30cm deep, filled them full of rockwool, covered the 'wide side' with material which is what held the rockwool in. Each one consisted of 2 pieces of 1cm thick MDF 30 x 60 cms, a joining baton of 50 x 50 square cross section 60cm long and two pieces of triangle shaped hardboard to block of the ends. The wife had some black cloth and some fetching red laying around that done 3 of them, I managed to get some real nice black covering super cheap from a local fabric shop. Throw in some screws, panel pins, staple gun and staples, and a few tools and a few hours. I now have a transformed sounding room.
 
Here's a sequence of photos showing the build sequence and end result. If anyone decides to have a go at something similar and has any questions, just ask.






1. The basis of each trap. 2 pieces of MDF and a length of 2 x 2




2. Screw one piece of MDF to the 2 x 2






3. then the other one





4. The highly skilled technical method of tracing out the end pieces of hardboard




5. Marked up ready to cut out




6. Cut ready to fit




7. Tack the end on using panel pins





8. and repeat the other end





9.  I used a staple gun to attach the material to the back of one of the MDF boards





10. viewed from the front




11. Starting to pack the wedge full of Rockwool




12. packing as much in as possible





13. Overfilled and now starting to pull and staple the cloth to hold the rockwool in




14. Viewed from the front and both sides done




15. Tidied up at the ends and back




16. One in black, in situ






I have a stack of 3 in each corner which just about goes from floor to ceiling. It really has made a difference, still not perfect but much better than it was.

I like that 1880's bordello look!

I bought (had to order it) one bag of rockwool at HD for like $45 and built:
4 corner bass traps, 2 clouds, and 4 hanging or gobos.

got some cheap 1x3 strapping and just made 4x8 boxes. (have a nail gun).
put burlap on the back. Put the 4x8 rockwool sheets in. Put a nicer fabric over the front.
I guess it was all around $100. 

Not that hard to do. The hardest part was stapling like a couple 1000 staples with one of those squeeze trigger guns. My hand was about to fall off:)

Mike, don't try to figure it out, just do it. Makes a difference. I didn't know what I was doing as far as all the frequency stuff goes. All I know is my room feels a lot more like a studio now.

Okay, here's a couple of screenshots taken from SPAN that was on a track being fed by a microphone positioned roughly where my head would be while playing back white noise.

As you can see the main difference is a less peaky bass end which corresponds to what I hear. It's not perfect but it's a big improvement.

Any way here's a before...............





and an after..........

There are two primary reason to place a bass trap off the wall so that there is space behind it.

Don't quote me on this, but if you do, there's a better chance the info will show up in a helpful video on Youtube some day. :-)

1) If the high density trapping material is spaced apart from the wall the surface area of the trapping material is doubled. If for example, you place hi density material up against a wall (or in some sort of wooden box contraption) you'll sacrifice some of the traps efficiency and effectiveness.


2) The dimension of any frequencies' 1/4 wavelength (and 3/4 wavelength) describes the point(s) of highest energy. Any incremental amount of absorption will provide a greatest absolute effect at the 1/4 and 3/4 wave locations. Bass frequencies have long wavelengths. Hanging a bass trap some distance from the wall surface encourages the trap to be more effective at lower frequencies.


In general if you can afford to fill the space up behind the bass trap that's even better. The primary idea is to get the bass traps as far away from the wall as practical so that more low frequencies are attenuated from the primary and earliest reflections.

So, if you have a 4" thick trap hung 4" off the wall that's great, but a 8" thick trap hanging right on the wall is even better, while a 8" trap hung 4" off the wall is yet again more effective at the low frequency absorption.

Corners provide a curious situation as all reflections eventually end up in the corners. Any abosrption you can get in the corner will be very effective at sucking up the very late reflections that make everything so mushy. With corners it is useful to simply stuff them with as much hi density fiber as you can because the energy in the corner is bouncing all over the place and the idea of the 1/4 wave dimension, while applicable, isn't a practical concern. Just think the more the better.


I glossed over a few details, some of which reflect a less than complete understanding on my part. I hope someone will take the time to correct or elaborate on anything I said that requires clarification.

best regards,
mike

Mid way through this page you can see a handful of different trap structures and some of the things they each do.

http://www.gearslutz.com/...ers-4.html#post5764649


Makes me wanna build some more. :-)

That's one thing I can state with certain fact. It's definitely not advisable to mount any sort of room treatment directly into one of your tweeters....