Masonite Panels...

[DrWho]

ok, so artto has curved masonite panels and the dope from hope has a diagram on how to build them...now what the heck to do they do? im hoping that understanding how they work will help me to integrate them into my room (if in fact the room needs that kind of treatment). i started piecing a few of them together and realized my panels are a lot smaller than i remembered them being so I was hoping to maybe combine them together to get a bigger panel (i'm assuming that a bigger panel would be more capapble of handling the lower frequencies.)

from my basic understanding, i think the panel is supposed to be a diffuser (causing the direct sound to spread out as it reflects off the curved surface). but i remember artto mentioning that the diagonal length had something to do with the lowest frequency it affected...is this still diffusion? i thought perhaps there were some absorbtive properties as well.

As far as application, i was thinking of putting a few of these devices in the horizontal corners (at least in the back) or just on the back wall in hopes of reducing rear reflections (the room i'm playing with is rather small and has hardwood floors). the rear vertical corners both have doors on them (which renders them useless for corner trapping) and the front corners will have the speakers crammed in them. if i can bring the speakers out a bit, then i will definetly put some in the corners right behind the speakers.

i don't think they'd work well to use on first reflection points, but i wanted to hear y'alls opinions on that (by 'first reflection points', im referring to the spot on the wall where you'd see your speaker in a mirror).

i think pics might make this easier to describe...i'll have to wait till my bro gets back from europe and then i'll steal his camera.

and lastly, how would one go about mounting these to a wall? (i think it's plaster). would drywall mount screw dohickeys do the trick? (provided i use enough).

as far as my room, im not sure about the dimensions, i'll have to get a measuring tape. But based on some guessing and entering stuff into some mode calculators, im gonna have about 30 modes below 150Hz with about an average spacing of 3Hz. yucko.

[DrWho]

one more question...

the only way i've seen these panels implemented is by placing them on flat portions of the wall. How would putting the curved panel across a corner of two planes (creating a much larger space behind it) affect the performance? How bout a corner of 3 planes?

i understand that a lot of experimentation is going to be needed, but im hoping to gain a proper understanding of what it's supposed to do so that I don't have to be random in my experimenting

[mikebse2a3]

Hi DrWho

I hope this picture comes out OK I'm new at this.

This is from a room I use to have and the tall brown panel is a polycylindrical diffusor I had built. I used two oak strips on each side which I had cut a deep grove in for the masonite panel to slide into. Then I ran screws from the back side to lock them together. I also placed eye bolts in the oak strips and used small chains with s hooks on them to adjust the depth of the bow of the poly.

I'm sure artto can give you alot better advice since he has alot of experience using these.

I've made polys out of clear lexan (which can be bent)when I wanted them to not be as obvious like infront of windows or maybe on the ceilings.

I would encourage you to get F. Alton Everest (Master Handbook of Acoustics) and read up on acoustics.In his book he says polys of chord length(Widths)of 2 to 6 feet and depths of 6 to 18 inches meet most needs. You want a mixture of poly sizes and orientations for best results also. There is alot you can do with the polys and what I,ve written just scratches the surface!

Also notice the white panel leaned against the poly its one of those ceiling tile panels I was playing with at one time I definitly wouldn't recommend them they cause more problems than they cure IMO.

mikeb

[mikebse2a3]

DrWho here is a picture of how some polys where used in what was the Klipsch Museum in Hope,Ark. This was taken in the late 1980s

There in between the windows.

mikeb

[mikebse2a3]

A few more pictures of polys in the Klipsch Museum.

mikeb

[artto]

You've asked a lot of questions. First things first.

Polycylindrical Cylinder Mounting

There are a number of ways to mount Masonite polycylindrical surfaces to wall surfaces.

The easiest way, provided were talking about conventional gypsum drywall or plaster wall construction, is simply to secure it directly to the wall with drywall screws or multipurpose screws. You usually dont need those plastic screw anchors inserted into the wall first. Be careful on older homes with plaster lath as electric wiring was often simply embedded in the walls without any conduit for protection. You may need someone to help you hold the panel, especially while flexing and bending it while securing it to the wall.

The above process can be made somewhat easier by making a frame out of 1x2 lumber as shown in the Dope From Hope newsletters (available in PDF format as The Paper at www.soundwise.org). The Masonite can simply be bent to be seated between the two side frame members, and the frame secured to the wall as mentioned above.

The above frame method is also useful to put a permanent bend in the Masonite. After securing the Masonite in the frame, paint it with a stain blocking shellac based primer such as Bullseye BIZ and then several coats of your desired paint/color. After the Masonite has resided in this frame for some time it will hold most of the bend. How long this actually takes, I dont know. Its something I discovered accidentally when I was disassembling some panels that had been up for years.

Another method is to take a 1x3 or 2x6 lumber or something similar that fits your needs and carefully cut angled slots with a radial saw of a width to snuggly fit the Masonite Panel edges. The 1x3 is secured to the wall and the Masonite panels are flexed to slip fit into the slots. (see Master Handbook of Acoustics, F Alton Everest)

Curved bulkheads can also be placed behind the panels and the panels secured to them. This method can be used in conjunction with the above slot method. The bulkheads should be randomly spaced to distribute any rsonances. (see Master Handbook of Acoustics, F Alton Everest)

You can also make a T support from a 1x4 and a 1x3 similar sized material. The top of the T is secured to the wall. The leg of the T projects from the wall and is the support for the curved panel. In this way, the curved panel can be suspended, away from the wall, supported down its centerline, sort of like a shield (see my posts in the architectural topic area, arttos klipschorn room). This method allows more sound to get behind the panel, from all sides, providing more trapping.

The polysurfaces can be closed, sealed or open. They may have acoustical damping material such a fiberglass or rigid insulation, open cell acoustic foam, etc, stuffed or placed behind them (see my posts in the architectural topic area, arttos klipschorn room).

These poly surfaces can lend themselves to very dramatic lighting effects through the use of both indirect and direct spot lights and backlighting. The can be made from plywood or a wood fiber product such as Masonite. For indirect or direct splash lighting, Masonite looks much better because of its smoother surfaces. Make sure you use a stain-halt type of primer first. These products have glues and resins in them which will eventually bleed through normal paint primers causing streaking. The Masonite should be of the tempered type which will be less likely to break when bending. It is often beneficial to alternate the orientation of the curved panels although in my room they are all curved vertically for architectural effect, and because the 45 degree toe-in of the Klipschorns already provides enough angular incidence of reflection off of the many varying curved surfaces on the front and side walls.

Master Handbook of Acoustics provides NRC rating guidelines for various sized panels of various chords (which changes the depth of the curve), open or closed, with or without damping material.

EDIT:

One other method I forgot to mention is on vertical panels you can simply wedge them between the floor and ceiling, or the ceiling and a 'catwalk' ledge as some homes may have (like mine). Depending on you situation, these panels may eventually sag due to temperature/humidty changes. I had to secure mine to the ceiling so they wouldn't fall down. I did this by making wood "L" 'clips' slightly shorter than the width of the panel for visual concealment. To more easily position the L clip, and have it positioned after the panel is taken back down I used double-sided tape to hold it place on the ceiling. I then drilled holes large enough to accept butterfly anchor screws and secured them to the ceiling (make sure you find and mark where the ceiling joists are so you don't run into them. Likewise, if the panels are perpendicular to the ceiling joists you can simply screw the L clips to the joists.) (see my posts in the architectural topic area, arttos klipschorn room)

[artto]

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On 7/25/2004 3:49:20 PM DrWho wrote:

from my basic understanding, i think the panel is supposed to be a diffuser (causing the direct sound to spread out as it reflects off the curved surface). but i remember artto mentioning that the diagonal length had something to do with the lowest frequency it affected...is this still diffusion? i thought perhaps there were some absorbtive properties as well.

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The curved panels act primarily as a diffuser at middle and treble frequencies. At lower frequencies they act primarily as absorption. If large enough, and bowed enough, they can also act as diffusers to some degree at lower frequencies, to help break up standing waves. How much low frequency absorption they perform is also related to their size and thickness of the material, as well as how much they are bowed and how they are constructed, open sides and back having the least amount of low frequency absorption, and filled ones having the most. (see Master Handbook of Acoustics, Appendix, F. Alton Everest)

Also consider that, because of the forces of gravity, vertical cylinders will sag, creating a true polycylindrical surface which has a continously variable radius. This greatly aids in its broadband diffusive properties. Also consider that these panels may be twisted or angled to further increase its diffusive qualities.

[artto]

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On 7/25/2004 3:49:20 PM DrWho wrote:

As far as application, i was thinking of putting a few of these devices in the horizontal corners (at least in the back) or just on the back wall in hopes of reducing rear reflections (the room i'm playing with is rather small and has hardwood floors). the rear vertical corners both have doors on them (which renders them useless for corner trapping) and the front corners will have the speakers crammed in them. if i can bring the speakers out a bit, then i will definetly put some in the corners right behind the speakers.

----------------

The curved panels act primarily as a diffuser at middle and treble frequencies. At lower frequencies they act primarily as absorption. If large enough, and bowed enough, they can also act as diffusers to some degree at lower frequencies, to help break up standing waves. How much low frequency absorption they perform is also related to their size and thickness of the material, as well as how much they are bowed and how they are constructed, open sides and back having the least amount of low frequency absorption, and filled ones having the most. (see Master Handbook of Acoustics, Appendix, F. Alton Everest)

I would avoid using these in the back of the room, especially directly behind or nearby any seating/listening positions, off to the sides on the rear wall may be ok. Most likely youre going to be closer to the back wall than you are to the speakers and you will still be getting near-term sound reflections off of these surfaces which will dilute detail, definition, and any spatial aspects the recording may have. The rear wall in most instances should be more absorptive to reduce near term reflections from behind you. http://www.harman.com/wp/pdf/Loudspeakers&RoomsPt1.pdf

[artto]

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On 7/25/2004 3:49:20 PM DrWho wrote:

i don't think they'd work well to use on first reflection points, but i wanted to hear y'alls opinions on that (by 'first reflection points', im referring to the spot on the wall where you'd see your speaker in a mirror).

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They can work very well on first reflection points however they need to be bowed enough. Usually the limiting factor is ceiling height and room size due to the bowed in effect of the cylindrical surfaces. Don't foget, the polycylinders do not have to be perpendicular to the wall. Twisting or angling them can provide even better diffusive qualities.

[artto]

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On 7/25/2004 3:49:20 PM DrWho wrote:

as far as my room, im not sure about the dimensions, i'll have to get a measuring tape. But based on some guessing and entering stuff into some mode calculators, im gonna have about 30 modes below 150Hz with about an average spacing of 3Hz. yucko.

----------------

This is why when building or choosing a good room for music reproduction you need to pay attention to the room size and proportions/complexity first. Most rooms in domestic environments are simple rectangular shapes. Those that are not often are part of an 'open floor plan' which has its own problems in regards to noise which becomes more difficult to isolate. This decreases the space's "signal to noise ratio" which can motivate you to play the system much louder than it needs to, ruining the more delicate effect of spatial detail and sense of space at lower sound levels.

[DrWho]

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This is why when building or choosing a good room for music reproduction you need to pay attention to the room size and proportions/complexity first. Most rooms in domestic environments are simple rectangular shapes....

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At the age of 20 though, it's almost impossible to obtain the means necesarry for choosing an environment ideal for audio. The room being discussed here is my bedroom in my house in Grand Rapids that I'm paying only $180 month to live in. Since there's other roommates, this is really the only room that I can do whatever with (and not worry about them destroying stuff).

That said, I still want to take any advantage of any opportunity that is presented to me and since my dad is giving me a ton of sheets of masonite, I figured that I would hopefully learn something in trying to treat this pathetic room (yes, it really does sound quite awful...and that's noticeable listening to a pair of crap speakers). Not only that, but it's rather unenjoyable listening to a poo system.

Anyways, I just wanted to say that to put this project in perspective. I already know it's going to sound bad.

One other thing, my listening position is actually going to be closer to the front wall than the rear wall...quite a bit closer. i believe my room dimensions are 12x14x9 (front wall being 12ft). My listening position will be like 4 feet back. Granted, I'll be experimenting a lot with where I listen and all that. I've got some room prediction software that tries to calculate shifts in frequency response due to speaker and listener location. Seems I need to move back 6ft to get the least amount of change.

Well thanks for all the info, there was plenty more than I wanted, lol. I also think that I'm just going to buy that book since everyone and their brother's dog is mentioning it