#1905940 - 03/08/08 07:04 PM
Plexi instead of MDF or Plywood in wall-mount Bass Traps
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tunehead
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Registered: 03/08/08
Posts: 3
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Hi,
I was wondering if anyone has tried using thick plexiglass as the front 'membrane' in Ethan's wall-mount bass trap design?
I thought a painted or clear, or possibly opaque plexi might look cool and still have enough mass to work as the membrane. I saw a few posts where Ethan went back & forth on using MDF becuase plywood has multiple resonance frequencies due to the construction (desirable), whereas MDF would tend to resonate at a more uniform frequency (undesirable). I wonder about plexiglass for the same reason - it seems like it would tend to resonate at a more uniform frequency. Farther down in the posts, someone mentioned getting good results with MDF, and Ethan decided that it wouldn't make as much difference as originally anticipated.
So, anyone care to comment on whether this design would be feasible?
Another thought - what would happen when drilling holes (either evenly or randomly spaced) in the front 'membrane' of this design, similar to old-school 'soundboard' that had all the holes in it. Good idea or not?
One more - what about using a 'membrane' in conjunction with a corner-mount bass trap of Ethan's design? I would still mount the 4" 705 FRK, foil side out, on rails, but would also mount a piece of plywood, MDF or plexiglass in front of the FRK a small distance, similar to Ethan's wall-mount design. The FRK would then be spaced at varying distances to the back of the trap, and would still have a membrane at the front.
Has anyone tried this 'combination' type design? Would the foil-side sound better in this design facing 'in' (to the corner), or 'out' (facing toward the back of the membrane)?
What about covering the membrane with sound-transparent fabric, similar to burlap or the commercially available fireproof acoustic fabrics? Would this help or hurt? It may help the aesthetics...
Thanks for any and all posts. This forum rocks!
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#1906141 - 03/09/08 10:39 AM
Re: Plexi instead of MDF or Plywood in wall-mount Bass Traps
[Re: tunehead]
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gullfo
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Registered: 03/30/04
Posts: 75
Loc: Old Tappan, NJ, USA
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what's the density of the plexiglass? it could work if the plexiglass is dense enough, or expect that it would only affect higher frequencies... you could mount a panel across the corner but to calculate its exact effect is unknown... you could cover the panels with cloth but expect it to alter the free resonance of the panel somewhat - again what is unknown but most likely a mild widening of frequencies with a slight loss of efficiency - then again, panel traps are pressure types so placement is everything...
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#1913673 - 03/21/08 10:26 AM
Re: Plexi instead of MDF or Plywood in wall-mount Bass Traps
[Re: gullfo]
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tunehead
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Registered: 03/08/08
Posts: 3
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Hi Glenn,
Thanks for the info. I had a feeling it would be directly related to the mass. I would ideally want a thickness of plexi that had the same mass as the plywood in Ethan's original designs.
Do you have any comments on any of my other questions, such as using a front wood or plexi panel in the corner-mount designs, similar to how it's used as a 'membrane' in Ethan's wall-mount designs? Foil side of FRK in or out on this design?
Also, what about drilling holes in the plexi (assuming the mass after drilling would be the same as an equivalent sheet of plywood), similar to old-school 'soundboard'. Do you think this would yield better or worse results?
As far as covering these with fabric goes, as long as the fabric is acoustically transparent, it seems like I could cover the traps but leave a small gap between the fabric covers and the FRK or panel/membrane surface, so as not to impede the free-resonance of the panel or FRK foil/membrane. Does that logic hold?
Thanks, you guys are the best.
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#1913920 - 03/21/08 05:16 PM
Re: Plexi instead of MDF or Plywood in wall-mount Bass Traps
[Re: tunehead]
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gullfo
Senior Member
Registered: 03/30/04
Posts: 75
Loc: Old Tappan, NJ, USA
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the holes create a Helmholtz effect and depending on the percentage of openings vs face, plus depth, plus cavity plus insulation in the cavity, cloth behind the face, will all determine the center frequency and Q. across a corner cannot be accurately predicted but you could use the average depth to make an assumption.
as far as density, the plexi will need to be very deep compared to MDF or plywood.
don't use FRK for this purpose but if you had no choice, then put the face away from the panel.
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