Anyone else here interested in, or built, or even heard Folded Well Diffusers??

I was introduced to the Folded Well Diffuser while looking around Agon, I forget who had first mentioned it, but I thought I might have a go at building some for my listening room.

RPG have submitted a patent for extended bandwidth folded well diffusers,

ReadScapes have a DIY page with many options to choose from, I went with the 40mm Prime number 7 version


I made some myself using 3/4'' plywood. The dividers I used 1/4'' maple ply which was lacquered on one side from factory. I've noticed the dividers have bowed and warped on me once installed. What's his name says you have to use cherry, I'm sure wood species will make a difference, I'm gonna use red oak next go around. 

@brunomarcs - I have made QRD17 also out of cherry wood. When I re-sawed the beams into the dividers I ran them on a joiner each time to get a perfectly flat surface to run along the guide, and still it wanted to bow a little. Certainly not what you’ve described though.

Have you considered making a comb that will have teeth that hold the divider fins in place at the correct pitch? I’ve seen a few diffusers using that method to get the centers perfectly aligned, maybe it could work for you?

I find building with wood to be so much fun, and almost therapeutic even.

How many did you make of these?
Where did you position them?
What were your listening impressions please?

@slaw - I suppose they will be collectively, reasonably heavy.
I made them 4ft long, and they are about a foot wide. Yeah, a dozen or two of them will get some mass, they weigh just under 23lbs each. The 5ft tall QRD 17 diffusers I made took two of us to lift, and I was admittedly the smaller fella doing the lifting.

I suspect in order to be reasonably rigid though, the structure needs to be made of a material that will not yield too much?? I’m still learning about diffusion, and getting better woodworking skills in the process.

@oldhvymec - it looked interesting enough to make this crazy builder have a go at them. I already have 6 built, then it occurred to me that I should ask in here if anyone one else found them beguiling enough to build, it appears there is.

@brunomarcs - I just also considered using popsicle sticks with the well width as the length cut, it would probably help to go from one side to the other and use them to prop it back into shape, for little investment?

I used Dennis Foley's plans and built them 9" deep. 2' by 4'   3 total placed bedind speakers. Dennis told me they probably wouldn't work in my small room 10' by 14'. He also said you have to take care of low frequencies first or your wasting your time. I have the 1/4" ply which is very good plywood used on the backs of cabinets, into a groove resting in the plywood boxes. The leading edge of said 1/4" ply has bowed and warped and has left a few small gaps in the front facing 2" wide strips. Idk if these have made an improvement in sq. I would have to remove them to really see. I would also need to build more to cover whole wall. Notice on Dennis builds they only go one direction on front wall. Rear walls and ceilings they do go in both ways. 

@brunomarcs - ok, so the first diffusers I built were Denis Foley’s Acoustic Fields QRD17, I have two glued up, four cut out.

However these folded well diffusers are a slightly different animal, and I have only got a 24’ by 15’ room. Because of this I went with folded well on the rear wall.

I plan on building the carbon absorbers and stacking them, slaw was bang on when he said that they’re heavy. The absorbers are even heavier than the diffusers.

The ceiling I’m not entirely sure how to tackle yet, I need some measurements and research to get a better idea of how to proceed.

Now, with your diffusers, there is a distance from the diffusers that you need to be in order for them to perform at their best, your room limits this.
Have you heard of BAD? Binary amplitude diffusers, and you can put absorption in behind them as well. I have read that .5" holes do deal with lower frequencies much more effectively.
These BAD panels are less restrictive in the listening distances in order to be effective. Do you want more information?

Yes I do want to learn of the BAD diffusers. But I'm also gonna remove a wall pour a slab and extend the room by 8'. So the dimensions will be roughly 10' by  21' minus wall stud and paneling thickness. It will be another year for this construction project to begin. 

The ceiling is 8' with a central ac above or I would remove it too. 

Why couldn't we put low freq absorption and diffusion in a wall especially if building new construction and Taylor the wall stud thickness to accommodate said building techniques? Has this been done before? So my whole wall is a huge panel!

Dennis quoted me 3,000 to 4,000 for his carbon technology, says it's the only thing guaranteed to work and I need a lot for my small room. 

@brunomarcs - I haven’t actually heard the carbon technology of Acoustic Fields at all. When Dennis spoke of how he come to discover the technology by accident, it reminded me of what was told to me when I visited the Genolan Caves.

It wasn’t too much of a leap to believe what he was saying about the micro pores in the activated charcoal is powerful for low frequency attenuation/absorption.

My plan is to get the diffusion done, take some measurements and build (from his plans and his DIY activated carbon) some ACDA-12 M type modular bass absorbers.

I can’t speak to the carbon absorbers, I haven’t heard them as I stated, but his QRD from plans work very well. I have only two assembled of the four cut out, and I have the two in my room, we love how they look and work in my room.

I spent $2000 on cherry wood and some more on glue, that’s just materials for my four QRD17 diffusers if you need some sort of idea. There is of course a big difference in cost between cherry wood and MDF.

I wonder if he has a customer near you, that might let you hear his room, to get an idea? I’m in the middle of west Texas, guns and big trucks galore, but audiophiles are not common out here. So I just went for it, so far I’m happy with the results.