John,
I've noticed in several posts that you have adivsed against using membrane absorber bass traps on the rear walls because they are reflective at mid/high frequencies. You have suggested using the hanging acoustic absorbers, but for my room I have two concerns about using these.
1) I'm not sure I can afford to give up that much space on the rear wall.
2) I'm concerned about the room becoming to "dead" if I don't have some reflective/diffusive surface on the rear wall.
I could place some "703 board" in front of the membrane panel which would take care of the mid/high frequency reflections, but then the room might sound too dead since I'm already planning to place mid/high absorbtion at all the first reflection paths from the speakers and around the front of the room.
How much diffusive surface do you advise is best, and where do you advise to place it? The dimensions of my room are designed to be 20'3" long, 14'4" wide and 8'7" high.
Thank you for your advice, and a great forum!
Scott
Rear Wall Bass Traps / Placement of Diffusive Surfaces
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John Sayers
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sound like you are building a LEDE room where the front of the room is dead and the rear is reflective. Not a very successful design that died in the late 80s.
"Dead" is a much abused term. Short reverb time would be a better phrase because people tend to use the term Dead to describe a room lined with carpet where the highs are absorbed but the low end is live. A room like this sounds muddy and woofy.
The aim is to bring the reverb time down evenly. It's easy to wipe out highs, hard to absorb lows.
cheers
john
"Dead" is a much abused term. Short reverb time would be a better phrase because people tend to use the term Dead to describe a room lined with carpet where the highs are absorbed but the low end is live. A room like this sounds muddy and woofy.
The aim is to bring the reverb time down evenly. It's easy to wipe out highs, hard to absorb lows.
cheers
john
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Guest
John,
Thanks for your reply.
I am not intentionally following a LEDE design, but I'm trying to follow the principle of not having any reflected sounds arrive at the listener within 20ms from the direct sound arrival. My understanding is there are only 2 ways to do this - place absorbers (or diffusive elements) in all the first reflection paths, or angle the walls & ceiling so there are no first reflection paths. Is this correct?
Regarding the goal of bringing the reverb time down evenly across the frequency spectrum, that is why I was trying not to put high frequency absorption in too many locations. I was trying to have approximately an equal amount off room surface treated for low frequencies (bass traps/membrane absobers) and mid/high frequencies (703 board panels), and I thought I needed a good amount of diffusion to keep the reverb time long enough without having "ringing" or other reflective problems.
Am I approaching this all wrong, or with an outdated methodology?
Please Help!
Thank you,
Scott
Thanks for your reply.
I am not intentionally following a LEDE design, but I'm trying to follow the principle of not having any reflected sounds arrive at the listener within 20ms from the direct sound arrival. My understanding is there are only 2 ways to do this - place absorbers (or diffusive elements) in all the first reflection paths, or angle the walls & ceiling so there are no first reflection paths. Is this correct?
Regarding the goal of bringing the reverb time down evenly across the frequency spectrum, that is why I was trying not to put high frequency absorption in too many locations. I was trying to have approximately an equal amount off room surface treated for low frequencies (bass traps/membrane absobers) and mid/high frequencies (703 board panels), and I thought I needed a good amount of diffusion to keep the reverb time long enough without having "ringing" or other reflective problems.
Am I approaching this all wrong, or with an outdated methodology?
Please Help!
Thank you,
Scott
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John Sayers
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- Joined: Mon Jan 27, 2003 12:46 pm
- Location: Australia
- Contact:
Take a look at photos of major control rooms that have diffusers. Based on what you said about having an even balance of low - mid - high - diffusion look at the % of the total wall space these diffusers cover. They are only on the rear wall, AND only where the room is big enough to warant it. Diffusion is the new catchcry - everyone says they have to have diffusion yet it doesn't appear to have affected the current designers.and I thought I needed a good amount of diffusion to keep the reverb time long enough without having "ringing" or other reflective problems.
Ringing and other reflective problems have nothing to do with reverb time. Ringing - flutter echos - bass nodes are all caused by bad acoustics not reverb time. In a control room you really want the room to be neutral, i.e. with practically no reverb time. Then what you hear will be what you get. Balance with in that, add reverb/effects with in that and then it will relate to each other room. My living room has a high timber ceiling, my floors are timber, my walls are timber and glass also. It has great reverb time and every CD I play in it has this reverb on it. I get used to it and it becomes the sound of my room. But if I open the two walls of glass doors to the outside the whole room changes dramatically. It all tightens up, the low end is tight, the sound is totally different. So which is right?? the control room is right because it has neither character and is neutral.
cheers
john