The most effective bass trap?

Discussion in 'Studio Construction & Acoustics Forum' started by sound_forward, Nov 4, 2005.

  1. First of all, I am not a mixing expert but a composer so sorry for my poor acoustical knowledge. Also sorry for my bad english.

    I will be working on a project out of main studio where I usually mix.

    The mixing room (actually a living room) is awfull...naked walls, big window (door for balcony), wierd dimensions (3.6x7.4x2.5m) with a big opening behind in other smaller room...

    The worst thing is that I have only one option where to set my little studio - in the corner! All other places are already occupied with other stuff.

    I do not want to treat the room acoustically to much because it is only a temporary solution.

    After a lot of experiments with speaker placement I actually found a very good setup (see picture) which sounds really good with mid/high frequencies (lets say above 300 Hz) and imaging is also very good.

    The only problem that I still have to solve are bass frequencies.

    I have some cancellations in the middle of the room and also some massive bass Waves in the corners and by the walls.

    The bad part is that I have only one corner in the room where I can apply some bass treatment - the corner where I mix.

    My monitors (Genelec 1030a) do not reproduce bass below 55Hz so I suppose that frequencies below are not the problem.

    What is the best way to bass trap frequencies from 55-300 Hz in my situation?

    Also, my right speaker is by the wall which I share with neighbour. I will not listen at loud levels (mostly because of bad room acoustic) but from my experience, low frequencies form this speaker will leak thru the wall and I would also like to solve this problem with bass trap.

    I would prefer cheaper and simpler sollutions if it is possible because this situation is only temporary but if more expensive soultions offer much better results I am prepared to invest.

    Thanks!
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  2. Greetings

    You're setup is really in a bad position in the room. I'd re-arrange the stuff in the room first and then plan the acoustic treatment afterwards.

    The most effective bass trap ( given all other things equal ) is a BIG ONE!!!

    :)

    Paul
     
  3. Thanks Paul,

    I amfraid that every other position in the room is not possible. I am stuck with this corner because this is only a temporary solution for smaller projects. Bigger projects will be done in proper studio.

    Why do you think it is such a bad position?

    This is the story behind this weird position...

    Acoustic treatment of this room is not possible because it is living room and I am not the only one living here :)

    Because of this, I wanted to decrease bad room response by placing monitors very close to me, so that I can listen to much lower levels and also to get much more direct sound and less room. Generally, I will not listen very loud music in this room.

    Then, I placed the speakers in diagonal position to keep decent simmetry and to get rid of unwanted reflections. For higher frequencies (above 400 Hz) I have only one wall reflection and this is the wall opposite the right speaker. There will be a mid/high absorber placed there. A cool article about diagonal placement can be found here... http://www.decware.com/paper14.htm

    I placed monitors right by the wall to prevent bass cancellation caused by walls behind speakers. I can deal with bass frequencies gain with controls found on genelecs (bass tilt, bass rolloff).

    The only big problem left is bass reflections from walls of opposite speakers. I will probably get cancellation frequencies at around 80-120 Hz because speakers will be at the distance of 1-1.4 meter from side wall.

    This is the reason why I want to deal with bass traps. I was thinking about making panel bass traps, like Ethan Winer suggests, and placing them by the walls only in this corner, behind speakers.

    Do you think it will solve this cancellation problem at low level listening?
    Generally, this room is actually not so bad for bass frequencies probably because of this big opening.

    The question is...Is it worth investing my time and money in building those 2 bass traps for this corner to get more accurate sound at lower levels (and to prevent bass leaking thru this wall because of neighbours) or is it just not worth doing it?

    Thanks!
     
  4. Well it's not only in a non-symetrical position, the corners are a place of bass build up.

    This is the story behind this weird position...

    Yes I read it. Sadly the author assumes sound travels in a tight beam, which is NOT the case. Speakers are pretty much omnidirectional, weighted to the bass end. Even the highs spread out somewhat. The wall the other side of the window doors, is reflecting from both the left and right speaker.

    I dont think he really knows what he's talking about. He confuses refraction with diffusion, even though diffusion is not an issue on the flat walls he's discussing

    "Nothing is truer than the statement; "You can't make a bad room sound good" This is crap.

    You'll need a lot of roll off, as your speakers are near two boundaries. Almost doubling the bass increase compare to one boundary

    I thought your speakers are close to the walls. Surely the room is wider than 1.4m? can you clarify?

    btw - Bass doesn't act like a travelling wave in a room. your problems will come from standing Waves.

    You shoud certainly put as much absorption in the corner behind the speakers as you can, but don't make panel traps, as they will still reflect all the other frequencies back at you. Use broadband absorptive traps, where the absorption is not covered by any panels.

    It's difficult to say without doing it and measuring afterwards.


    As said you shoud definitely fill that crner with absorption, but it won't do anything to preent bass leaking through the wall. For soundproofing you need MASS.

    hth


    Paul
     
  5. Regarding speaker placement...my speakers are by the walls and the room width is 3.6m. Distance between the speaker and the nearest side wall is 1.4 meters. For left speaker, I will get bass reflections from the wall behind the right speaker. Also, right speaker bass will reflect from the wall behind left speaker. This is why I am afraid of bass cancellation around 100Hz.

    What kind of broadband bass trap do you recommend? I thought before that panel bass traps are the best for broadband traping because they can resonate at many frequencies??? So there is a better solution? I do not care to much about mid/high reflections from the panels because speakers will radiate most of these freqs in other directions, and on shorter wall I will put some absorbers and the other wall is pretty far away (7.4m). Bass frequencies are my main conserns.

    Thanks once again!
     
  6. The most common is basically a large volume of rockwool ( or glass wool or foam ) arranged in a wedge ( or thick panel ) across the corners.