Barrel diffusers

[dillweed]

not much talk about these so....

I've got a medium sized tracking room. about 26' x 23' with 9 foot ceilings and no parallel walls.
The ceilings are well diffused, the wall to ceiling corners are sofited, and the corners are bass trapped. Hard wood floors.

would some barrel diffusers on the walls be the way to go to make the room sound "bigger"?

I would think 1/8" plywood wrapped around a shallow "u" shaped piece of could be made fairly easy. Maybe stuff the thing with fiberglass and pull out from the wall an inch or two for more bass trapping.
anyone make these, or have any info?

a google search of "barrel diffuser" comes up with quite a few plastic varieties.

[terry j]

try poly diffusor in the search.

studiotips has a lot on polys...they are quite down on qrds!

[Glenn Kuras]

Originally Posted by terry j

try poly diffusor in the search.

studiotips has a lot on polys...they are quite down on qrds!

Not sure if those guys are down on QRD's (well I hope they are not) but +1 on the poly's.

[spm_gl]

Interesting... If you build a real barrel, i.e. out of wooden slats, you could combine the diffusor with a slat resonator, by leaving a bit of space between the slats. Interesting...
Would look a bit weird though.
Polys are rather simple to build. Here's a pic of ours (made of plexiglass, also works as a membrane resonator) in the background:

[norton]

I built "barrel diffusers" into a room design to great effect.

The room is triangular, for lack of a better term... and we really wanted to stay away from any nasty flutter echo's etc.. So we built in a curved diffusing wall treatment from the floor to 8' up the wall.

I don't think it would be fair to say that it made the room sound "bigger"... but it did get rid of all of the nasty ringing... and the space really does sound good. We also stuffed the cavities with insulation for extra trapping. Works great.

I've put these to use in other room designs too. Where you need to spread sound around AND get a little extra bass trapping the poly-cylinder shape can be ticket.

Good luck!

[Weasel9992]

Polys don't tend to get much love, but they really are great. I've got them on the "live" side of my gobos.

Frank

[terry j]

Originally Posted by Glenn Kuras

Not sure if those guys are down on QRD's (well I hope they are not) but +1 on the poly's.

Well, I don't think my assessment was too far off the mark...to be fair to them it seems mainly due to complexity vs simplicity, cost that sort of thing. But there is quite a bit of derision over RPG and their ability with PR to 'oversell' the benefits of qrds vs polys.

That was the main reason I came over here with my 2 ch thread. I was not 'determined' to use qrds or prds, but I simply could not get data at all really to rule them in or out.

You may have noticed discussion of qrds was , umm, quite accepted here!!??

At the end of the day they feel qrd's co not really offer much over polys...I know this is in no way definitive but my small initial attempts using the ripple tank to see the difference, well honestly polys do not come even close to the diffusion abilities of qrds.

So I personally am sticking with qrds.

[Glenn Kuras]

Originally Posted by terry j

Well, I don't think my assessment was too far off the mark...to be fair to them it seems mainly due to complexity vs simplicity, cost that sort of thing. But there is quite a bit of derision over RPG and their ability with PR to 'oversell' the benefits of qrds vs polys.

That was the main reason I came over here with my 2 ch thread. I was not 'determined' to use qrds or prds, but I simply could not get data at all really to rule them in or out.

You may have noticed discussion of qrds was , umm, quite accepted here!!??

At the end of the day they feel qrd's co not really offer much over polys...I know this is in no way definitive but my small initial attempts using the ripple tank to see the difference, well honestly polys do not come even close to the diffusion abilities of qrds.

So I personally am sticking with qrds.

I think it really depends on what you are going for in the room. We did sell poly's (will have them back some day) and liked them A LOT. But the QRD (our d1 is based off the 7 root QRD) seems to work a bit better when the listener is less then 6 feet (6" QRDs) away from the unit.

[terry j]

Originally Posted by Glenn Kuras

I think it really depends on what you are going for in the room. We did sell poly's (will have them back some day) and liked them A LOT. But the QRD (our d1 is based off the 7 root QRD) seems to work a bit better when the listener is less then 6 feet (6" QRDs) away from the unit.

glenn, kinda off topic a bit but I see that you are keeping an eye on this thread

can I ask a favour?

would jason be able to clarify his comments on the barker code implementation please?

maybe not in this thread, but perhaps in my 2 ch thread (or not, as long as we get the answer)

it may be only me that has misunderstood his comments, (and if so then I have already made one wrongly!!) but it would be good to clear it up.

Pretty sure the confusing points have been outlined in the last page or so of that thread, if not then I can ask the question precisely after a good sleep.

thanks for that.

[Glenn Kuras]

Originally Posted by terry j

glenn, kinda off topic a bit but I see that you are keeping an eye on this thread

can I ask a favour?

would jason be able to clarify his comments on the barker code implementation please?

maybe not in this thread, but perhaps in my 2 ch thread (or not, as long as we get the answer)

it may be only me that has misunderstood his comments, (and if so then I have already made one wrongly!!) but it would be good to clear it up.

Pretty sure the confusing points have been outlined in the last page or so of that thread, if not then I can ask the question precisely after a good sleep.

thanks for that.

Can you direct me to the question you would like for him to answer? The thread has gotten kind of long so I left it as it was WAY to much to keep on my radar.

[terry j]

Originally Posted by Glenn Kuras

Can you direct me to the question you would like for him to answer? The thread has gotten kind of long so I left it as it was WAY to much to keep on my radar.

Boy!! Aren't you diplomatic haha. Did you not want to say 'that thread got so fricking boring....'??

Anyway, good call to ask me to link the question...most of it was not in my thread at all! Had forgotten that it had transferred to another.

So here it is, hopefully jason can see where the confusion lies, and that will help him answer

http://www.gearslutz.com/board/4612843-post162.html

thanks to the both of you.

oops, that came up as a single post. Still, if the answer can be put in that thread rather than this one, think that would be better.

[Glenn Kuras]

Boy!! Aren't you diplomatic haha. Did you not want to say 'that thread got so fricking boring....'??

YES! Kidding!


I will email Jason to see if he can get to it.

[mattyRPG]

If polys worked as well as QRD and other types of diffusor, everyone would use them..I think the sheer quantity of acousticians who specify RPG products gives an indication of how they perform. For 'diy' projects then yes, Polys have a place for budget and simplicity, but if you have the choice and can make an informed decision then why not...

[Weasel9992]

Originally Posted by mattyRPG

If polys worked as well as QRD and other types of diffusor, everyone would use them..

You'll have to qualify that a bit. They do different jobs, really. One isn't "better" than the other any more than a screw driver is "better" than a socket wrench. It all depends on what kind of problem you're trying to solve.

Frank

[mattyRPG]

hi Frank

if I may

http://www.rpginc.com/news/library/tyndall_paper.pdf

part of the paper explains the difference far better than I can.

[Weasel9992]

Originally Posted by mattyRPG

hi Frank

if I may

http://www.rpginc.com/news/library/tyndall_paper.pdf

part of the paper explains the difference far better than I can.

Thanks for the paper...very cool. I'm aware of the physics and resultant performance differences, and the point the author makes is a good one as far as it goes: I wouldn't use a poly cylindrical diffuser at a first reflection point either. Then again, I'm not a fan of diffusion at the first reflection point to begin with.

Again though, I don't see anything (other than the reference to the small-scale study by Lee) that indicates that one form of diffusion is *better* than the other, just that it's different. The context of Lee's study seems to have been performance halls, which is indeed the spacial reference throughout the paper with a few exceptions.

Frank

[mattyRPG]

Sorry I havent replied sooner, I really dont know how you guys all find the time to browse these boards all day AND do a days work, maybe I need a secretary..

I suppose it comes down to personal preference if pure measured performance is set aside. Polys do have advantages, from a speed point of view its a whole lot easier and quicker to manufacture and install the polys, though in the handful of installations ive seen that they have been used, there has always been something with the install, either rattles, resonance or poor finish (that said though, ive also seen some very poor QRD copies built in studios by so-called specialists too) Inconsistancy seems to be another issue, especially for onsite manufactured parts..

polys do give a good account when used for live rooms, sometimes a studio design will blow the budget on the control room so cut back in the live room with polys being used instead of more expensive devices, and also in ceiling reflecters the poly has found a good home, we have a couple of projects coming through at the moment with a lot of those parts in the ceiling design - and there is the difference i think. For use in auditoria the polys are good, directing sound back as well as offering some diffusion, while on walls the QRD type device gives that bit more scattering?

for raw feel I really prefer step-installed DFR units over QRD, not many smaller studios have gone for that in the uk but the places that have really make it work well - Students who have studied at LIPA should be familiar with that set up in the main Sir George Martin studio

There are some good papers in the AES library on polys from way back in the day, some of those are worth the fee.