|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
131.191.158.45
I'm considering a DIY room lens, but have just one question before I pick up the parts. Here goes: With my room dimensions, I've only got anywhere from 2 to 3 feet from the speakers to the side walls, where there's currently 1st reflection point damping. Is this space (2-3 ft) enough to allow the room lens to work?
Thanks in advance.
Follow Ups:
They tend to work a little better with more room to develop the diffusion, but that should be enough room to try them.
Realize also that placing the Room Lens in various positions MAY require that the speakers be moved to achieve the very best results. Thus, you may find that moving the speakers away from the wall a bit more might be helpful with the Lens placed between them and the wall.
Here is a repost of my original note:
Argent Room Lens Analysis/Clone Note
by Jon M. Risch, (old e-mail address deleted) 3-8-99
I thought it might be interesting to share a process of product analysis concerning the Argent Room Lens. Please note that I have not seen a pair in the flesh, have not seen any whitepapers on the product. I have visted the review at Soundstage (http://www.soundstage.com/noisy14.htm), and read the review in Stereophile. See also the Argent web page:
http://www.roomlens.com/index.html
and the StereoTimes website review:
http://stereotimes.com/acc112999.shtm
The Enjoy The Music review:
http://www.enjoythemusic.com/magazine/equipment/0503/argentroomlens.htm
Using dimensions and derived dimensions based on the photo's provided, I proceeded to analyze the acoustics of the product.
Over all dimensions: 58" long tubes/pipes, slightly less than 2" I.D. on the three pipes, probably 2.5" nominal PVC plumbing pipe with close to 1/4" walls, the HD pipes. The composite width at the tubes is approximately 8 1/2". The spacing between the tubes varies from top to bottom, with the wider spacing at the top, varying from about 1" to about 2/3".
Now what would this do to a sound wave that hit it broadside (parallel to the three tubes)?
First, ignoring the Helmholtz resonator aspect, it can only affect frequencies above a corner of about 1.6 kHz, the frequency where the wavelength equals the width. There will be some effect down to about 800 Hz, below which, it won't present any sort of significant obstacle acoustically. Any significant affect on a sound wave will occur above these frequencies, slight effects above about 800, and near total effects above about 3 kHz.
The spacing between the tubes will allow frequencies with wavelengths above the spacing distance to shine through in a straight line in the cracks between, and be almost totally blocked where the tubes are, so they act as diffractors (a form of diffusion) from a low corner of 1.6 kHz, up to about 16 kHz, where they will act as a picket fence shadow, mostly blocking the frequencies above 16 kHz. A significant amount of energy within this band will also be directly diffused off of the rounded tubes.
The recommended placement and orientation will essentially make the aforementioned frequency band for the nominal first side wall reflections and the front wall reflections (to a lesser degree) become diffused on the way toward the way reflection point, and diffracted before the remaining sound energy is reflected off the wall.
This would result in the side and front wall reflections effectively being diffused and broken-up up to a large degree, avoiding a coherent presentation of energy to the ear from the first reflection.
Unlike wall hung diffusers at the mirror points on the side walls and the front wall, these Argent Room Lens will actually re-radiate a diffuse field from their location in the room, as well as diffuse the side wall reflection like wall mounted diffusers. This re-radiated sound energy will not be readily apparent as a distinct source for two reasons: one, it has been dispersed in an almost 360 degree pattern, to bounce off of other room surfaces in most instances with an arrival time at the listener at a much later time, and second, the re-radiation will be at a minimum along the edge of the three tubes, which happens to be aimed at the listening position.
The tubes themselves will act like classic Helmholtz resonators, and if they were simply open tubes, they would resonate at approximately 117 Hz, and multiples and sub multiples of that frequency. However, they have some acoustic resistance at the bottom (a fine screen), and some stuffing somewhere inside the length of the tubes. Clever placement and density choices of this stuffing could effectively result in a bass absorption right where the typical 8 foot ceiling has it first resonance mode, effectively damping this first mode via the tubes. If all three are tuned slightly differently, not only could the first floor to ceiling mode be reduced, but several of the higher order modes as well. This 8 foot floor to ceiling mode would be fairly universal, and so would be a definite way to help reducing this floor to ceiling set of modes.
My conjecture would be that by reducing the floor to ceiling modes, and enhancing the amount of random and uncorrelated horizontal reflections, as wqell as delaying and reducing the first arrival times of the side and front wall reflections these devices would tend to enhace the apparent sound image, effectively reducing the negative effects of the room itself. I would guess that they would have less of an effect with planar or other highly directional speakers, and would be at maximum effect with a full omnidirectional sound source, and at a high amount of effect with most dynamic multi-way speaker systems.
Reducing the side wall, and to a lesser extent, the front wall first reflections without any absorption or radical room geometry is a new one on me.
For those interested in constructing there own, it should be easy to obtain the necessary materials from a hardware store. Use 2 1/2" heavy duty/high pressure PVC pipes, cut to 58 " lengths, spaced apart 1" at the top tapering to 7/8" at the bottom for the left pair of tubes, and spaced apart about 3/4" at the top tapering down to a little over 5/8" at the bottom for the right pair of tubes. Make a nice heavy non-resonant base, and a hardboard cap to hold them in place. Finish as desired.
Now for the educated guess part:
Roll up a wad of 3/4 to 1" thick loose/puffy polyester batting about 16" long by 12"for each tube, rolling up the 16" portion, and push it into the tubes using a long stick. From left to right tube, position the end of the wadded polyester 18" from the bottom, 23" from the bottom, and 18" from the top on the last one. A wad of fiberglass could be used as well, a piece of 6 1/2" by 4' by 12" long, or 3 1/2' by 8" by 12" long. Then place a piece of very fine mesh screen on the bottom of each tube. If you can't get a very fine mesh screen, wrap a layer of nylon stocking on each side of a regular piece of screen door metal screen, and wedge/glue it into place.
You might even make it one tube wider, just repeat the tube pair spacing (I would opt for the wider spaced pair) opposite the added tube. This would make it effective down to even lower frequencies.
This would be a minimal investment to see if they do anything for your room acoustics. I do not have the time to build them anytime soon, so if anyone else does, let us know how they work for you.
Jon Risch
***************************************
Posts on constructing a DIY Roomlens
Alternate construction:
http://www.AudioAsylum.com/audio/tweaks/messages/307.html
the base:
http://www.AudioAsylum.com/audio/tweaks/messages/8679.html
http://www.AudioAsylum.com/audio/tweaks/messages/13630.html
3D DIY Room Lens (David Aiken):
http://www.AudioAsylum.com/audio/tweaks/messages/99714.html
and
http://www.AudioAsylum.com/audio/tweaks/messages/102957.html
Original Room Lens reviews:
http://www.stereotimes.com/acc051199.shtml
http://www.soundstage.com/noisy14.htm
http://www.enjoythemusic.com/magazine/equipment/0503/argentroomlens.htm
(This one has the placement diagrams)
Hope this helps.
Jon Risch
for all the information.
I'm definitely going to give it a go this weekend. I was planning on taking the wood bases to the woodworking shop on a nearby military base, but unfortunately, they're going to be closed.
So I won't be able to make them as purdy as I was hoping. Also a bit concerned about cutting the holes by hand. A drill press would have been really nice.
Oh, well. I guess I can always bungee cord the tops together.
For the tops you can put wood block spacers in between and use an elastic strip or strong tape to pull it all into shape. You want this thing to hold that odd shape that Jon Risch mentions, where the tops are very slightly more widely spaced than the bottoms. You also want the bottoms and tops open, and the stuffing dimensions you can get from Thorsten Loesch's old post.
You do NOT want unstuffed pipes, however.
I drilled mine with a hole saw bit on a hand held electric drill and it worked fine.
Links to DIY Room Lens projects.
Parts List And Photos
Edits: 05/26/10
.
The suggested basic placement for the original Argent Room Lens used 3 units with one placed to the outside of each speaker but quite close to the speaker and a central one placed close to the wall midway between the speakers. I'd say you've got enough room for them.
You say "I've only got anywhere from 2 to 3 feet from the speakers to the side walls, where there's currently 1st reflection point damping." If by "damping" you mean absorption, that will work against the room lens. The room lens diffuses using 2 mechanisms. The first is reflection from the curved surface of the pipes which reflect sound over a wider angle than a flat surface would. The second is by diffraction of sound passing through the gaps between the pipes. Diffraction spreads the soundwaves over a wider angle as they exit the gap so they then reach a wider area of the wall behind for reflection over a wider angle also (angle of reflection = angle of incidence so widening the angle of incidence also widens the angle of reflection). Sound reflected from the wall towards the room lens is also diffused in the same way. Placing absorption on the wall behind the room lens is going to reduce the amount of sound diffracted through the gaps to the wall which gets reflected and also reduce the amount of sound reflected from the wall towards the room lens which gets diffracted on its way back into the room.
In my experience with my DIY room lens units, the original recommended placement wasn't always the most effective. When I tried them years ago in my current L-shaped room I found they didn't help particularly well in the standard locations and part of the reason for that was the fact that I had a lot of books providing absorption on one wall behind the left hand unit, an open archway into a hall behind the right hand unit, and heavy curtains behind the central unit. In other words none of the surfaces behind them were reflective. By experimenting I did find useful placements elsewhere in the room but they were obviously heavily determined by the asymmetrical shape of the room and where I had reflective surfaces. If you're going to place them in front of absorption you may not get much benefit (I suspect a lot will depend on the size of the wall area covered by the absorption and how that area relates to the way the lens diffracts sound along the wall and also how it relates to how the wall reflects sound towards the lens). In that case you're really going to have to experiment with placement elsewhere, picking areas where you do have reflective surfaces and trying them to see what effect they have. It will vary with location.
You also said you were considering "a DIY room lens" and the use of the "a" rather than a term like "three" or "some" tends to suggest a single room lens to me. If you're going to use a single lens only, then I wouldn't be placing it near the speakers but rather on the centre line between the speakers close to the wall behind the speakers or the wall behind the listening position.
Further comments for DIY construction: units with more than the original 3 pipes are more effective because of their greater width which increases the amount of diffusion provided. If you're going to use more pipes, then I think there's a fair amount of room for experimentation with pipe geometries other than placement in a straight line. I originally made 4 of the standard 3 pipe units but later dismantled them and used the pipes for 2 units, an 8 pipe unit with pipes based on a pattern determined by quadratic residues, and a 4 pipe unit based on a primitive root sequence. I felt the 8 pipe unit was more effective than 3 of the standard 3 pipe units placed side by side in the same location. Those are the only non-straight line geometries I used and I make no claim that they are the most effective in normal use. I was playing with odd placements in my asymmetrical room when I decided to try them but I do think a symmetrical unit like the 8 pipe unit would be far more effective than a single 3 pipe unit if you're only using one unit placed on the room's central line. It certainly was in that location on the wall behind my speakers but I also found that while it produced a stronger effect I did not like that effect. I ended up with it placed on the wall behind me where I thought it's effects were quite positive but that wall was in the toe of the L-shape and I don't know that it would have the same effect in the centre of the rear wall of a normal rectangular room.
I eventually stopped using them and now rely solely on absorption in my room.
So basically I think they work, I think bigger units work better and there's a lot of room for playing with different pipe geometries to make them even more effective, and I find them extremely placement sensitive. They definitely work more effectively in front of an untreated wall.
David Aiken
David:
You wrote: " The suggested basic placement for the original Argent Room Lens used 3 units with one placed to the outside of each speaker but quite close to the speaker and a central one placed close to the wall midway between the speakers."
The central one placed "close to the wall" midway between the speakers. Is that front or rear wall? And the ones outside of the L and R speaker, should they be next to it or slightly (or more) in front or rear of each speaker? Thanks in advance.
ET
I thought it was time to change my signature line
Found this online - Thanks! ET
I thought it was time to change my signature line
Yes, that's it. The original web site is long gone now but they had that picture there, plus a couple of others showing how to place some additional units.
David Aiken
they supposed to be 'in-line' to the sound propagation to the first reflection on the side wall?
I don't know if that was ever clearly explained in the instructions but I placed them along the first reflection path. Try playing with their angling a little as well.
David Aiken
Hi David,
Thanks for all the information. I am planning on building a trio of room lenses.
I never realized that you're not supposed to use these, along with acoustic treatment. I guess it's going to require some experimentation on my part.
From reading some of your earlier posts, it seemed as though you were pleasantly surprised by the sound improvement of the lenses. What made you change your mind to removing them altogether?
Mamoru
"I never realized that you're not supposed to use these, along with acoustic treatment."
I don't think it's that, exactly. You certainly can use them along with other acoustic treatments but the question becomes one of placement. They use reflections on wall surfaces to help achieve diffusion so placing absorption where they need the room surface for reflection works against them.
I suspect a major reason why they tend to be used without other acoustic treatments is that they don't look like the average acoustic treatment product and I suspect more than a few people who couldn't, or didn't want to, use normal acoustic treatment products went for the room lens because it took up less floor space than other treatment products and didn't look as bad in a living room. They're also light and easy to move so they could be moved into place for a listening session and removed afterwards quickly and easily.
I seem to remember that their advertising made a big deal of the fact that they absorbed bass frequencies by their action as a Helmholtz resonater, and also worked as a diffuser, so they tended to be pushed as a single treatment strategy that did everything. I think the bass absorption was not particularly great and they certainly were incapable of replacing a good set of bass traps. For their size, however, I think they did a reasonable job of diffusion. They have no absorption whatsoever at higher frequencies however.
Why did I remove them? I first built them when I was in my previous home with an awkward room, couldn't use any other sort of treatment because it was a very small living room. They helped a lot there but the room was basically rectangular, was reasonably reflective, and less problematic than the L-shaped room I acquired when I moved house. It wasn't easy to find effective placements for them in the new room and one of the major problems with the new room was that the shape of it strengthened the reflections from one side, pulling the centre image to that side quite noticeably. In the end I found it easier to get better results using absorption and the best placement for the room lens units ended up being where I needed to put a sofa so in the end absorption and furniture won out over the lenses in the new room.
David Aiken
I have some experience with DIY room lens clones. I use only 2 triplets and they work very well indeed. Mine are NOT in the standard setup, which didn't work as well in my room. Mine are actually behind my speakers inboard at the first reflection point from that wall.
As David says, you have to experiment in your room and move them all about to various reflection vectors.
Also as David says, there are many different possible configs of these devices, and his posts list several good ones. But I found the basic triplets work very well using the exact dimensions and fill as described by Risch and Loesch in their posts. These are cheap and easy to make. Mine cost me about $25 for two several years ago, and I doubt they're much more expensive to make up today! So you can experiment a lot for very little money indeed.
You can work with one, BTW, but as David said, it's not the best setup. Argent originally recommended at least 3 and many more as potentials.
Have fun!
When I finally got around to looking at how these things are made, I couldn't believe how really easy it seems. I figure I should be able to put these three together in a few hours.
And as for the price, you're right. It shouldn't cost me much more than about 50-60 bucks for the trio of them.
Looking forward to hearing how these will work (or not) in my room.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: