http://www.johnlsayers.com/phpBB2/viewt ... &start=105
The design uses deep construction timber with the slats protruding away from the wall, ie. not on their side.
John mentions that he uses wood that is varying depths 150mm to 200mm and varying gaps between (5mm to 10mm), but they are all the same width, standard construction timber (probably 45mm).
I understand how these would be good low frequency absorbers. These can be tuned really low, even down to 30Hz with the 200mm slats and a big air cap in a corner.
But, John says they work from frequencies from 30Hz to 100Hz. This sounds great and perfect for my rear corners.
Let's calculate the open area range:
10mm/45mm width = 0.22 or 22% open area,
5mm/45mm width = 0.11 or 11% open area,
So the open area ranges from 11% to 22%.
When speaking to Stuart, he mentions that a helmholtz acts less as targeted individually tuned peaks as you increase the open area above 5%, but more like a single device that is tuned to a general frequency in the range with a lower Q. Anything over 20% isn't tuned at all.
How can John say that this design is tuned from 30Hz to 100Hz when it has an open area of at least 11%.
I think John must know that it works because he says in the post he uses them in his designs now, even replacing hangers with them.
He says he now uses them in rear corners (my intended usage.)Anton - hangers take up a lot of space - they typically are either in the ceiling above a false ceiling or in a rear wall behind a cloth wall.
I'm now using a new design - take a look at the rear wall in this corner control room:
Obviously John has confidence in the design.In this control room it solved the typical bass buildup problem at the couch.
http://www.johnlsayers.com/Pages/Rose_Lane.html
I'm now using them in the rear corners with hangers above.
Help me understand how these things work well, how they can be tuned and yet have a larger open area?
My first thoughts are that because the depth is significant (at least 150mm), this affects the open area rules of thumb.
The standard slat helmholtz uses slats on their widths, ie. The widest face is facing into the room. This gives a depth of usually around 20mm. This means the "slug" of air bouncing in the gap is only 20mm deep.
I wonder whether a 150mm to 200mm deep slug of air would mean that you can get away with a larger open area without lowering the Q too much.
What are your thoughts?
Dan