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Room Acoustics Forum by Rives Audio Welcome! Need support, you got it. Or share you ideas and experiences. |
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Room Acoustics Forum by Rives Audio Welcome! Need support, you got it. Or share you ideas and experiences. |
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In Reply to: Thanks, bartc! This makes perfect sense. posted by Dan_ed on May 30, 2005 at 09:16:19:
First, a couple of minor quibbles with Bart's post.The first reflection points will always be on the wall that's closest to either the speaker OR the listener. Wherever the smallest of those distances is, that's the wall where the earliest reflection point will be located.
Room lenses do need a wall. They diffuse by 2 mehanisms - spreading reflections from the curved surfaces of the pipes, and by diffraction of sound waves passing through the gaps between the pipes. The sound passing through the gaps is spread wider than it would be if the pipes weren't there. Sound travelling through the pipe gaps to the wall is then reflected by the wall over a much wider angle. In addition, sound reflected from the wall back into the room passes through the gap and is spread over a wider angle as well. If you don't have a wall you lose the reflections that add to the diffraction effect and are left only with the reflections from the pipes which will lose much of your diffusive efficiency.
L shaped room - Hmmm. Sounds like mine :-)
Start by trying the standard Argent recommendations - outboard of each speaker and one in the centre and behind the plane of the speakers. This may well not be the best placements in an asymmetric room but you haven't provided any info on how the room is oriented in relation to speakers and listening position. The reason I say the standard recommendations may not be best is that they are going to spread some early reflections and that can become messy in an asymmetric room. I think absorbing the earliest reflections works better in my room and I then use the room lens units to break up the reflections from the problem end of the room.
In my room the vertical stem of the L is the listening area and I sit facing the left side of that stem so the speakers are on the long wall. The toe of the L is behind me so the base of the horizontal foot of the L is my left wall. The top of that foot and the bend is just behind my right shoulder. I use 2 room lens units, one in each corner of the toe of the L so they are both behind me. They aren't standard 3 pipe units, or even your 4 pipe unit. One is an 8 pipe unit with pipes placed at staggered depths like the wells in a quadratic residue diffusor. That's in the corner almost directly behind me. The other is a 4 pipe unit with staggered depths based on a primitive root formula that's in the corner adjacent to the left wall. I use absorption at the sides between me and the speakers and also on the wall behind the speakers.
I think placement in an asymmetric room like an L-shaped room is definitely a trial and error approach but you can get quite good results. You can also improve the effectiveness of room lens clones using 4 or more pipes by placing the pipes in configurations that aren't straight lines. I've only tried 2 variations on that - the ones I'm currently using - but I suspect that many other useful designs could be found by simply basing pipe placement on mathematical formulae like the quadratic residue and primitive root formulae used for the design of more conventional diffusors.
David Aiken
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Follow Ups
- Re: Thanks, bartc! This makes perfect sense. - David Aiken 14:20:36 05/30/05 (2)
- Thanks for "piping" up, David! - Dan_ed 15:50:48 05/30/05 (1)
- Re: Thanks for "piping" up, David! - David Aiken 23:18:25 05/30/05 (0)
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