Bass trap frame made of plywood ?

Hi everybody ! Today I began to build my first bass trap !!! :shot: :yahoo: lol (it's a projet I have for 1 year now, it was time to begin it !! ) I just bought enough to built only 2 panels, so as to validate the design. The frame is 2.5m high and 70 cm wide, made of strong fir tree slats (160mm wide, 28mm thick). It contains 150mm thick wool and will be covered with a clothe. I just finished one frame today and now I can see how (very) heavy and strong it is... and I wonder if something so heavy is really necessary ... so, what about making the frame with plywood, 15 or 20mm thick ? Is plywood good enough for that purpose ? Thanks for your advices ! I'll post some pictures of the trap I'm building as soon as possible :)

welcome - I'd like to see the pics if you can post them :)

According to some acoustics experts that design will have no effect and is a waste of material. For a bass trap to work it must be absorbative

Really? Wow! That's incredible! So you are saying that people who build panel traps, Helmholtz resonators, slot resonators, membrane traps, and suchlike are misguided, and have no idea what they are doing? Did you ever manage to explain that to F. Alton Everest? I'm sure he would have been fascinated by your theory! Just as I'm sure that the real acoustic experts on this forum (who write books on the subject, and build world class studios every day) are also fascinated by it... This truly is an outstanding revelation for the world of acoustics! After all these, years, and all those Helmholtz resonators and panel traps that have been built all over the world, it really is fascinating to learn that none of them actually work... :!: - Stuart -

Hi everybody ! here is some pictures of the first panel : the wood frame: detail of the corner: Clothe on the back of the frame: the picture with wool indise is missing ! The finished panel: Finally it is a strong and not so heavy panel, It will be a nice corner panel :). For the other panels I found better wood : $4.3 nice fir tree slat, 10 mm thick, 100mm wide and 2.4m high. It will be used for 100mm thick whool panel.

Looks very nice!

After testing my first panel I wonder that what I planned to do would make a very damped room for high frequencies (cloud panel is not showed here) : Would this this configuration be better ? : thanks your for your advice !

I think that new design will give you a bit better bass trapping.

oh, nice !! :D thanks

This weekend I was explaining to a friend my project of acoustic correction with hand made panels ... and he told me that Auralex kit where maybe as efficient, or maybe more than the panels I was doing, for the same price (around 600/ 700€) , which correspond to this : http://www.auralex.com/sound_control_pr ... oject2.asp or http://www.auralex.com/sound_control_de ... xeplus.asp What I'm wondering is, how a small LEND corner trap, which is only 2feet long (60cm) would be as efficient as a full panel of 2,5m high of 150mm of whool ?! Is it really efficient, especially if there are 8 placed in each corner wall/wall and corner wall/ceiling, combined with the the wedge panel?

I think you mean "LENRD", not "LEND". You might be interested in the data on this page, which compares the performance of LENRDS to another brand. http://www.realtraps.com/data.htm The LENRD line on the graph (purple line, bottom graph) is not very encouraging, since that is supposed to be a bass trap! There doesn't seem to much "trapping" of "bass" going on with those things: Below 200 Hz. (kind of where "bass" lives) the performance drops like a dead brick.

What I'm wondering is, how a small LEND corner trap, which is only 2feet long (60cm) would be as efficient as a full panel of 2,5m high of 150mm of whool ?!

Answer: It cannot be. Not unless they figured a way to change the laws of physics! The graph speaks for itself. Stick with what you are doing, I'd say. - Stuart - (PS. The graph for the wedge foam is not exactly exciting either... Yellow line, top graph)

Thanks SOundman !! I just read a topic in the forum talking about the same thing :) Okay, let's doing DIY panels !! :shot:

Yeah, stick with DIY yer doin' a good job already. Standard (glass or rock) wool will absorb pretty good and it's waay cheaper. PLUS you can make it very, very custom to your likes :) I'll link this threat in the sticky about absorbers (viewtopic.php?f=3&t=10304&start=0). thanx

New idea : what about that : three questions : - Does it matter if the left Wall/ceiling panel is 40% shorter than it symetrical at right ? - Does it matter if I place on the rear wall only acoustic foam and no bass trap ? Or do I need to bass trap a lot even in the rear ? - Does it matter if there is no cloud panel ? Thanks a lots for your help :)

- Does it matter if the left Wall/ceiling panel is 40% shorter than it symetrical at right ?

You should try to keep the room as symmetrical as you can at least as far back as the mix position. Behind that isn't so important.

- Does it matter if I place on the rear wall only acoustic foam and no bass trap ? Or do I need to bass trap a lot even in the rear ?

It's a small room, so you should try to get as much bass trapping as you can into it.

- Does it matter if there is no cloud panel ?

Yes! The ceiling is a first reflection point, and should have absorption on it to prevent reflections muddying the sound, creating comb filtering, etc. - Stuart -

Thanks Soundman but what do you mean by : "You should try to keep the room as symmetrical as you can at least as far back as the mix position. Behind that isn't so important." ? Does it mean that there should have wall/ceiling corner bass trap from the speaker to the mix position ?

I feel I must comment on this room layout. This room is going to sound dead and dull because all the highs have been removed - you've left practically no high end reflections in the room. Also the term Bass Trap is missleading because placed flat on a wall the absorption tapers off the lower the frequency. Take a look at this room http://johnlsayers.com/Pages/Hello_Testing.htm It's a standard bedroom yet Paul Goodwin produced award winning commercials in that room, the hallway outside was lined floor to ceiling with international awards - all the dialogue was recorded in the room - there was no booth. As you can see there is reflective windows and and a reflective front and ceiling - the rear wall and rear ceiling is the main absorption area. Its a matter of balance.

Hi John ! thank you very much for your help ! :D So, if I understand, there should have more reflective surfaces on the room... Because of the small dimensions (3.6m by 3m, 2.5m high), I've been told that there will have low frequencies problem (even more because I'm trying to mix electro music with lots of low ends), this is why I planned to put so much bass trap. I have some idea for trapping bass, and trying to keep some highs : - to place a wood plate on the front of some bass trap panels. This would reflect more highs and if the panel is drilled with adapted holes, this would also makes a Helmotz resonator and help to trap more low frequencies ? - Simply remove some panels, just let the wall/wall corner and wall/ceiling panels, those just behind the monitors, and the cloud? A last question : I thought the room had to be as sysmtrical as possible, so I planned to put in the room entrance (on the rear, as you can see on the pictures) a big wood plate with a bass trap attached to it. Does it makes sense? what should I do? thank you very much for your advice :)

well instead of covering every wall with a panel why not leave some free - like the rear sides, and double up on the rear wall and ceiling.

Use a low-pass filter on your basstraps to stop them from absorbing too much mid/high frequencies by adding a sheet of plasic of thin wood in front of the wool. You can also make it a slottel pannel, vary the spaces to make it non-tuned. John uses it a lot and they LOOK great to begin with :) They prolly "SOUND" great, too ;)

Hi everybody :)

instead of covering every wall with a panel why not leave some free - like the rear sides, and double up on the rear wall and ceiling

okay, however, I just read some topic on the forum talking about rear wall reflexion... explaining that in small room, rear wall absorption wasn't necessary because of the small delay betwenn direct and reflected sound. So, what to think about rear wall absorption ? I should explain that the sweep spot would bebetween only 1.5 / 2 meters far from the rear wall, and that between the sweep spot and the wall there is a bed ! (look at the lasts picture in the previous page :)

Use a low-pass filter on your basstraps to stop them from absorbing too much mid/high frequencies by adding a sheet of plasic of thin wood in front of the wool. You can also make it a slottel pannel, vary the spaces to make it non-tuned.

For the wood place, this is what I thought to do when I talked of drilled wood plate on the front of panels. I'm going to get a new microphone this week (Superlux ECM999) so as to make some measure of the "empty" room and see where are the peak and the null in the frequency reponse... Maybe I'll need some tuned panels. Let see it when measures will be done :) Howerver all the panel will me mobile, so I will be able to place them with different space from walls !

Phazinhead - next time you are front of your speakers put your hands up to your ears and cup them to stop the rear reflections - you should notice the difference.

Hi everybody ! I got a Superlux ECM999 test microphone this week, I have done some measure today of my room, as empty as possible (only the desk, monitors, bed and littles things). Here are the results, made with RoomEQ Wizard : The peaks at 120Hz and its harmonic at 240Hz are pretty loud when I listen to the music, which is confirmed by the graph. So, What do you think globally of the room reponse? What are the main things to do so as to correct the peaks, and also the big null around 95 Hz and 180 Hz? thank you very much for your comments !

I should also mention that the speakers were placed on the desk, which was placed very close to the front wall (there was a 5 cm space between monitors and the wall). The monitors center (between woofer and tweeter) is at 120 cm from the ground, the ceiling is at 250 cm. I'm currently building support for the monitors, this one : http://www.tnt-audio.com/clinica/stubby_e.html let me know what you think about all of that ! thanks :)

I need your help to tell me what you think of that idea for holding the cloud and the wall/ceiling panels with a wood structure like this : Does is matter if the wall/ceiling panel is not "stuck" to the ceiling (look at the red circle on the 2nd picture) ? does it lower the absorbtion capacity?

As far as I know, there shouldn't be any problem with that. In fact, it should help, I think, with a broader range of frequencies.