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Rudy81

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  1. I have not explored how to 'tune' the membrane at all and although I'm sure it would be possible to figure that out, I'm not looking at that right now. The curved surface is also flexible to some extent when you put pressure on it since it is bendable plywood and it is very pliable. The recess is 3/4" which is the 18mm plywood frame. I cam up with this since the back of the frame rests against the wall surface. I figured the MLV needs room to 'breathe' as the LF pressure strikes the MLV surface. The LF will transfer across the curved surface, so that is how it gains access to the MLV membrane. Units are mounted with french cleats flush with the wall. In actuality, I didn't need to create the MLV mounting frame since the french cleat by itself creates a 3/4" space behind the frame. So now, the MLV membrane is about 1.5" from the wall surface.
  2. Generally speaking, most rooms have the biggest problems with bass and it is the hardest to tame. I am talking about bass below 300hz or so. My goal with this build was twofold. First to tame some of the bass room modes and second, to improve the room 'sound' by not just absorbing the HF frequencies. I'm still in the early stages of listening to the new room, but it seems very promising.
  3. I don't believe the skyline diffusers will do anything for bass frequencies. AFAIK, they are strictly HF diffusers.
  4. If you are talking about the 'skyline' type diffuser I think that is way more complicated to build, particularly on a large scale. As I understand it, the poly vs. the quadratic diffuser are very different in operation. The poly uses the curved surface to diffuse the sound and keeps the sound timing, phase and amplitude more 'coherent' than does a quadratic diffuser. Since the quadratic diffuser has varying well depth, it changes the timing of the reflected sound. There is quite a bit of discussion on this topic on the net. As you can imagine, there are many opinions on the subject. Both ideas have their detractors and supporters. Based on how long this project has taken, it is well worth doing some intensive research before you commit to one type or the other. This project has taken way longer than I anticipated, but seems to be well worth the time and materials....at least for me. Looking at my plots, the poly's definitely do tame some, but not all, LF resonances. In my case, some is better than none. I still have not had time to really listen to music in the room. As soon as I have some time to dedicate to critical listening, I will report back. For sure, it sounds 'different' than my original setup with just absorbers at the reflection points.
  5. Well, if I end up using poly diffusion on the back wall, you can have the quadratic diffuser I currently have there. 😁
  6. Here are the initial results of the project once hung on the walls at the reflection points. I did run sweeps for the three main speakers as well as the subs. Have not had time to study the results, nor had time to listen to anything. More to come.
  7. All 12 polys are now complete. As soon as I have time, I will begin the process of hanging them at the first reflection points on the side walls. Plan is to first take full frequency sweeps of each main speaker with the room in its present state. Then, remove all the side reflection point absorbers. Another set of readings. then hang the polys and finish with a set of readings with the polys hung floor to ceiling at the reflection points.
  8. Showtime power-up is easy. I use a programmable remote to sequence what I wish to watch or listen to. Once the Integra fires up, it uses the two timed triggers to start the two Furman PS-8R sequencers. They, in turn, send power to the needed equipment in slow increments so as not to have everything power up at once. Works pretty slick actually.
  9. More progress today. Finished adding the MLV to all 12 polys. Also added cleats to the top section of each poly. I did not glue the cleats in case I ever want to change the hanging method or wish to use the polys in some other configuration. Next will be adding the material and adding the hanging cleat to the walls. Getting close now.
  10. Cost is certainly a big consideration for all of us. I personally stay away from fiberglass or mineral wool and prefer cotton products. I think it would be worth your time to find the Master handbook and look at the suggested examples of good corner traps. You may not have to use hard fiberglass or mineral panels due to the way the corner pieces are constructed. Once I finish the side polys, assuming they actually do work, I will be building some more for the back of my room for diffusion and more bass absorption. Once that is complete, I will be addressing stand alone bass traps for the front of the room behind my screen, followed by attention to the room corners.
  11. Are you talking about the super chunk corner trap? Floor to ceiling insulation stacked one sheet on top of another? Get a hold of The Master Handbook of Acoustics and it has some suggestions on corner traps. In general, there is a piece of thin plywood or luan that is attached to the side walls running floor to ceiling. Insulation is added behind the panel, but not totally filled. Just a sheet running vertically floor to ceiling with an air gap. You should be able to find a copy of the book from many ebook providers if you don't want the hard copy. It is well worth the effort to really research this before you start your project. This is my second effort at all this. The first time I really didn't do my homework and am having to replace some itesm.
  12. I use QSC as well for my HF section. I know many look down on Behringer, but I use several Behringer EP4000's for all my effects speakers as well as my subs and LF sections. Plenty of power, reliable and inexpensive. All I did was to change the original fans with quiet fans and have never had any issues. I used to have a K2, but didn't need another whole house heater in just one room.
  13. Again, I am no expert. But, I have found that my corner traps were pretty much useless for low frequencies. The physics of LF sound dictates that those super chunk traps are actually....useless, which is what I HAD in the corners. Actually, this type of diffuer/absorber in corners has better ability to trap bass than the super chunk idea. Eventually I will use a similar design for the corners. In corners, the LF velocity becomes pressure as it reaches the walls. You need to 'absorb' the pressure by using a flexible surface that will dissipate the pressure. That, is the basic idea. The thickness of absorption material in a super chunk required to dissipate LF is so thick, it is impractical in any common listening room. That leaves things like membranes or helmholtz resonators for true LF absorption. My plan is to keep taking before and after measurements to see what actually works. Plenty of available data on this subject.
  14. Finally had a chance to get back to this project. Today I finished trimming the excess bendable plywood edges, sanding all the polys, and filling each with Ultratouch denim insulation. Next will be cutting the MLV and stapling to the back, adding french cleats to the back and finally covering with fabric. I used thicker 8" insulation in the largest two sizes. The 3.5" thick insulation went into the smallest of the polys. I lined them up for size comparison as shown in the pic.
  15. I used 1/4" bendable plywood for the front. You can use many other products for the front, but my research indicates that wood has the preferred qualities for HF diffusion and is somewhat flexible for use in LF absorption. It is also a product that is easy to cut, glue and adhere. A 4x8 sheet of barrel bendable ply cost me about $20 per sheet. You can also get the 'column' bend plywood which bends along the 4' edge to make an 8' column. I measured the circumference of the polys and cut the bendable ply a little larger, then use a hand router with a flush trim bit to size perfectly. Used glue and brads for the larger polys to attach the poly front. The smaller sizes needed staples to keep the bendable plywood attached while the glue dried (smaller radius polys were at the limit of the natural bend of the plywood and needed to be held in place while glue dried). This is where the time needed to bevel the outer edges of the frame paid off. Here is a picture of a semi-finished poly. This is the basic structure prior to adding interior insulation, attaching the LMV, adding french cleat and finally adding the colored material to finish the poly. I have finished all the basic structures but need to add the insulation, add the cleat and finish the exterior. Plan is to take room readings with nothing at the reflection points, with just HF absorbers, and finally with the 12 polys in place.
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