[Glenn Kuras]

Hey guys. Just found this great program for designing QRDs. I most say it is about the best I have found so far.

ENJOY!!!!!

http://www.subwoofer-builder.com/qrdude.htm

[TRADERXFAN]

Awesome. Thanks for sharing this!

-Tony

[Browntrout]

Very Cool, thanks. Quick question, if I wanted diffusion at my first reflection points could I make a diffusor that had a design frequency of say 400hz giving a well width of 120mm, then.....on the faces of the 'wells' putting a diffusor pattern that dealt with much higher frequencies say a design frequency of 3500hz giving a panel width of 119mm which would fit on to the faces of the wells of the same panel. Do you get what I'm saying? Cheers, Ben.

[bpape]

Understand and some people do that.  It does somewhat impact the upper end of the larger diffusion pattern but can be done.  In our big diffusers, we use a poly for the face of the wells instead.

Bryan

[Glenn Kuras]

Understand and some people do that.  It does somewhat impact the upper end of the larger diffusion pattern but can be done.  In our big diffusers, we use a poly for the face of the wells instead.

Bryan

Here is a picture so you can see the poly built in.

[terry j]

Very Cool, thanks. Quick question, if I wanted diffusion at my first reflection points could I make a diffusor that had a design frequency of say 400hz giving a well width of 120mm, then.....on the faces of the 'wells' putting a diffusor pattern that dealt with much higher frequencies say a design frequency of 3500hz giving a panel width of 119mm which would fit on to the faces of the wells of the same panel. Do you get what I'm saying? Cheers, Ben.

like this??





I designed it using the calc linked to, is a five prime within a seven prime (hope the smaller pic is clear enough) and that is designed to go within a thirteen prime.

These have a width of 161 mm, and the bigger picture shows when the five repeat has been put together...with hopefully a/the correct implementation of the barker code!!!

When these are inserted in the prime thirteen, whole shebang will be about 1800. Just as info, what you propose (only two diffusors in total...as opposed to my three in total) is ample to cover 400-20 000 hz (play with the calc and you will see). I only needed to go three diffusors because I had an 'exact' space to fill, and a two diffusor build was either too narrow for that space or too wide.

Anyway, as already stated, it is a very good calc, tho prob start in basic mode till you get the hang of it!

[JakeJ]

Understand and some people do that.  It does somewhat impact the upper end of the larger diffusion pattern but can be done.  In our big diffusers, we use a poly for the face of the wells instead.

Bryan

When you are referring to a "poly" is that the curved face in the well?  I see some have more or less curve and some are flat, is that combination the "poly"?

Your D1 diffuser uses all curved surfaces and varies the depth and width of the wells.   Is this due to a manufacturing advantage of working with molded plastic?  Most of the wood diffusers have equal width of the wells and the are equidistant in spacing.  Are the wooden versions made this way for ease of construction?

Thanks for the link too.

Jake

[bpape]

Hi Jake. 

On the big wooden well diffusers, some of the wells have polys, some don't.  Jason would be the one to answer the reasons why - he designed them.

On the D1's, working with molds certainly makes things easier.  The one wider area is where 2 wells of the same depth are next to each other.

The advantages of the convex curves is that they don't have an upper limit. 

Bryan

[JakeJ]

Thanks, Bryan.

Jake

[tdangelo]

Glenn/Bryan, when will these be available and how $$ 

Thanks
Tony

Understand and some people do that.  It does somewhat impact the upper end of the larger diffusion pattern but can be done.  In our big diffusers, we use a poly for the face of the wells instead.

Bryan

Here is a picture so you can see the poly built in.

[TomS]

Glenn/Bryan, when will these be available and how $$ 

Thanks
Tony

Understand and some people do that.  It does somewhat impact the upper end of the larger diffusion pattern but can be done.  In our big diffusers, we use a poly for the face of the wells instead.

Bryan

Here is a picture so you can see the poly built in.

Tony,

I saw these at last year's RMAF and they were beautifully made.  Bryan, I can't recall, maybe maple or cherry wood?  Very nice stuff indeed.

Tom

[bpape]

They're available as a custom order thing.  We try to do them in batches as they're a LOT of work.

Maple is the stock wood and just a blonde finish.  We can do them in other woods also but price varies depending on what you want.  We're going to be doing about a dozen of them for a recording studio outside Dallas pretty soon if that job comes through.

Bryan

[tdangelo]

how much for the stock wood/finish?

[Big Red Machine]

Looks like a fun woodworking project for the winter.  Bryan, is there a rule of thumb for the design you should target based on the room dimensions and modal frequencies?  I'd like to replace or face off the absorber behind me with one of these anywhere from 4 to 6 feet wide and up to 8-10 inches deep and put some 4 - 8 foot wide units on each sidewall.

[Glenn Kuras]

how much for the stock wood/finish?

Around $1300.

BTW if that job comes through I can let you guys know and we can put you in with the batch.  aa
Or if you guys want to team up (we need around 8 to make them) we can do it that way.


who's in??

[bpape]

Looks like a fun woodworking project for the winter.  Bryan, is there a rule of thumb for the design you should target based on the room dimensions and modal frequencies?  I'd like to replace or face off the absorber behind me with one of these anywhere from 4 to 6 feet wide and up to 8-10 inches deep and put some 4 - 8 foot wide units on each sidewall.

Hi Pete

Doing a diffuser in front of the absorber will defeat the purpose of the absorber.  It's been a while since I've been in your room.  Not sure there is enough distance to really make diffusion an option behind you.

You don't really usually use diffusion for modal issues.  The bottom really effective frequency of diffusion for that 6" deep well diffuser is around 500Hz, well above your modal issues until you're up into the higher harmonics.

Bryan

[srlaudio]

Hey there.... we have some solutions, too, here is our offering in this area.  What do you think of this?

http://www.srlaudio.com/srl_new_product_announcemen.pdf

[JakeJ]

Howdy All,

I played around with the Mode Calc (available on RealTraps website) and then did the same with the QRD Calc (thanks Glenn!).  After punching a variety of numbers, including my actual room dimensions, I can see there are theoretically a bunch of modes between 32 and 500 Hz on all three axes.  Then I spent a few minutes punching a variety of numbers into QRDude and noticed a pattern emerging.

Basically dependant on depth of the individual wells and the prime division used, these factors determine what frequency "window" the QRD diffuser is good for.  So if we have a diffuser with a depth of 7 inches and a prime of 11 it covers the window of 394 Hz to 2,866 Hz.  If we have a depth 2 inches and a prime of 37 the window changes to 1,654Hz to 11,466 Hz.  Changing the prime shifts the window up or down in small steps and changing the depth gives much larger steps.  If we leave the prime at 37 and change the depth to 1 inch the window is now 3,307 Hz to 21,500 Hz.  This offer great flexibility of fixing the sonic anomalies that can occur in our listening rooms.

It would appear that before one arbitrarily buys and puts a QRD diffuser in a room one should take careful measurements to assess the range that need fixing.  Also don't forget hanging diffuser on the walls will not address modes in the vertical plane.  That's where a skyline type of diffuser will work nicely.

Does all that sound reasonable, Glenn and Bryan?

It appears my plan to make DIY diffusers out of commercial paper roll tubes will not work quite as well as one fabricated to the specific need of a particular room because the width of the wells need to change as we design it for that application.  The paper tubes are all 3.5 inches O.D. and none of the calculations I got were even close to that large.

A whole lot of good info and it saved me a bunch of work that would have been a waste of time and materials.  Every single day I learn something new here.

Thanks again to the acoustics gurus for this great information. 

JakeJ

[richidoo]

Thanks for the link Glenn, that is awesome!

[Rob Babcock]

Hey there.... we have some solutions, too, here is our offering in this area.  What do you think of this?

http://www.srlaudio.com/srl_new_product_announcemen.pdf

If you're going to jump in with your product, please give us a little info on how they work instead of just advertising them. 

As per the posting guidelines, discussing a product you make is fine- I'd rather not have open advertising of them in this Circle.  I think you guys are okay here, just heading this off at the pass before it turns into a showroom.