# how to measure the effects of diffusers



## djnagle (Dec 12, 2012)

Hi All, I am doing some experimentation with diffusers in my room. I'd like to measure the before and after effects of the diffuser vs flat wall. What is the best way of doing that with REW? Thanks, D.


----------



## Tonto (Jun 30, 2007)

Absolutely, there is a learning curve, but many people have learned to use it. And you can always ask questions here. We are glad to help. It would be nice if you could post your before and after measurements. That way we could all benefit from your experiments. What kind of diffusor are you using?


----------



## djnagle (Dec 12, 2012)

Here is the experiment. I have an Ikea 5x5 book shelf I use for my LPs. I will make the diffuser shape shown in the pic out of 1x3 pine and attached it to the back of each cubby so when I put the LPs in, the front of the records will take on the shape of the diffuser. I am using the Optimized Stepped Diffuser plan-form from Tim Perry at http://arqen.com/sound-diffusers/.

I want to measure the records flat across their front, then with the plan-form back as far as it can go so each cubby will have an inset diffuser face, then with the plan-form forward more so the deepest well will be on the same plane as the front of the book case.

That way I'll know where to permanently mount the shapes. Here is the book case now surrounded by bass traps I made and installed last week.


----------



## Blacklightning (Nov 22, 2011)

A few things.
1. why make something to place behind the LP's, just place the LP's in the shape that you need and measure.
2. From what I read most bookshelf's with book, LP's, DVD, even CD's act more like a Absorber than a diffuser.
3. it does not look like you have the room but I would place hard diffusers in front of the LP's. One for each square. Just remove it to grab another disc.
4. I love what you have done with the back of your room.


----------



## djnagle (Dec 12, 2012)

Thanks Black, these little plan-forms are so easy to make and I can just slide my LPs back in place without thinking about their position. The reason I want to measure the results is to determine if they work well enough or if I should build front diffuser panels for each cubby.


----------



## djnagle (Dec 12, 2012)

Should I measure the room with the diffuser or can I measure just the area with and without the diffuser? What should I be looking for in the plot?


----------



## emearg (Oct 7, 2013)

A very cool Idea but i don't think it make any difference, I get the idea you still want see all your LP 

I am sure some expert will tell you more but in small room less than 20x20ft diffuser are less than ideal or almost useless in some cases as the rebound times are so close to original Stick to absorption (rock wool)

Be careful not over kill the refection as this can be just as bad I think the rule of thumb is around 20-30% of all surface area (walls, floor, ceiling,doors and window as well) (corners and first point reflexion being the most import ares to treat 

Room layout can be just as import to your sound move stuff to the the best point (not always the same place with and without treatment) and symmetrical layout and construction (large windows reflects things very different to drywall) left to right make huge difference not so much front to back 

Just for testing place some sheet of rock wool over face and test (Some time you just got try stuff) 

I would post a room layout (with some sizes Ruff will do ) and your listening position marked Hopefully 33% or 66% of front wall


----------



## lesmor (Dec 30, 2009)

IMHO putting the diffuser inside the "cubby" is never going to work and you will be wasting your time and effort
Think about it logically a diffuser needs room to breath (ideally 10' of space behind the MLP) and the waves need to scatter.
With that panel design they need to scatter and wont work inside a box.
Only a proper designed QRD allows a box design.

Perhaps if they were on the front of the "cubby" like a door you might have half a chance but I imagine your LP's stick out the front of the unit making that impossible.
Sorry but realistically just forget the whole thing.


----------



## djnagle (Dec 12, 2012)

All good points Les, but experimentation is about testing a thought not forgetting it. 

I want too test the idea and that is why I am asking about how to measure the results.


----------



## lesmor (Dec 30, 2009)

djnagle said:


> All good points Les, but experimentation is about testing a thought not forgetting it.
> 
> I want too test the idea and that is why I am asking about how to measure the results.


Fair enough
Well I would have thought use a REW ETC chart to and see how that works out


----------



## djnagle (Dec 12, 2012)

I am new to REW Les. I've used it a number of times but not with any real deep understanding of the program. Will the reflections show up as the deep dips when I set it to 48 smoothing?


----------



## lesmor (Dec 30, 2009)

djnagle said:


> I am new to REW Les. I've used it a number of times but not with any real deep understanding of the program. Will the reflections show up as the deep dips when I set it to 48 smoothing?


Hi
I am reasonably new to REW as well but if you use the help option and search for impulse response you will see ETC mentioned.
I would suggest visiting AVS find the REW thread, look for a post from Austin Jerry in his sig is an excellent guide on using REW.
Near the end is a section on impulse response and ETC showing how to identify reflections.
I imagine if you use that before and then after fitting your diffusers it might help in showing the effectiveness of your experiment.
Good luck with your project and I hope it works out for you :smile:


----------



## djnagle (Dec 12, 2012)

Thanks for the tip Les, I'll check it out tonight. I had every plan of doing this today, but very heavy rain, lightning, and thunder pushed back my yard work. I have the wood, pattern template, and band saw so it shouldn't take long to make and install them. I use clamps first and if they do make a difference, I screw them. Pix coming.


----------



## Blacklightning (Nov 22, 2011)

Any update?


----------



## djnagle (Dec 12, 2012)

No update. Summer got in the way.


----------

