Quadratic Residue Diffusor
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- เผยแพร่เมื่อ 23 ธ.ค. 2014
- This is a short video of how I made my diffuser. It's not in great detail, but it may help you get started.
Main Website - Home page
www.mh-audio.nl/index.asp
Calculate Quadratic Residue Diffusor ( given size )
www.mh-audio.nl/Diffusor.asp - บันเทิง
that is a fine art piece. the wife will like it even when she finds out what it's for
Hi John! congrats for this craft! it looks really nice.
Would love to hear a before and after!
There might be some diffusion effect,. but this is not a quadratic diffusor which is working cause of closed chambers with different dephts,. on deeper frequencies it may not have any effect at all,. but maybe its a good idea to put something like 10 cm rockwool in the back,.. then you get an absorber with some diffusion effect on the highs,..
That's really brilliant! I may well attempt to do something similar, perhaps using strips of OC 705 covered with bedliner and painted.
well well well, it is simply amazing, thank you for sharing
nice work!!
Nice build John.thats dual purpose forsure. Sound and art.
I m kinda new to diffusers. But been doing research on them.
Lots of info on (Acoustic fields )channel. About room acoustics.
I was so curious I built(QRD well type)one out of double walled cardboard. Based on prime 7.
2 each. 1foot by 3feet.6 inches deep.and you know .it opened up the sound stage. And the speakers almost disappear.
I've had the same stereo for 30yrs.it has never sounded like it does now.
So I'm now building it properly out of wood. Going to try cedar.
I like the fact you experimented. (I'm the same way).
I learn from doing.not listening to other people.
I curious to find out the sound difference. Between this and a well type defussor.
Cool. They are great. I have a video recently with Dolby Atmos vs DTS. Check that out.
Hi. Did you make it finally your QR7 ? What are your results? Thanks
Sweet. Thanks for sharing this.
It's a nice diffuser and looks pretty, but that's not what you want on the rear wall! You want absorption, make that wall disappear so there is very little sound coming back, not scattering it around the room. But it's your money. Live room, .6 seconds of reverb, control room, .4 seconds of reverb and you cant to that with all the diffusion in the world. Also splay your interior walls, two adjacent walls splayed from center horizontally and the other two splayed vertically then the ceiling. Right angles are a no no. Try a few broad band absorbers in place of the diffusers, you will find that your room sounds much better. PSI have made an amazing active absorber that sounds like it removed a big chunk of the wall so there is no return, it's amazing and only about 15x28x24 inches or so with a mic and driver inside that reacts with the incoming audio.
the rear wall needs diddusion.
the side walls need absorbtion
megahertz eh?
That room is still ringing like crazy.
No, the sound on the video was recorded elsewhere in the house.
@@JohnCranberry23 Yeah obviously, but why?
@@gutshisalamanca1191 Back then the camera I used wasn't very good. I have a video recently with Dolby Atmos vs DTS. Check that out.
Its a sound diffuser man, it only distributes sounds horizontally or vertical. Depends on the orientation of the quadratic diffuser.
Great design,I'm gonna make some.I've got some marine ply I found in the street that I'm planning to use.
I'm in Sydney and I make Acoustic panels,let me know if you want to try some out.
Have you done anymore since this video?
No I haven't, only made this. Might make some absorber panels and base traps one day with ceiling bats and fabric, when I find some time.
Very nice work. Couple of questions: I noticed that you appear to have use somewhat of a bridge approach as opposed to well-type diffuseors I have seen elsewhere. This seems to me to be an easier and more cost-effective approach. Is it as effective as the well-type diffuseors? Is there some kine of formula one must use based on the size of the room, etc? Thanks again for the great video.
There has been debates for bridges vs wells. The bridges will trap and diminish sound waves as they enter the QD and bounce back from all angles. I have fabric behind the bridges which also helps. As far as the room size goes, the larger the room the more treatment you need. The QD works best placed directly behind your head. You can make it as large as you like. But remember sound bounces off all walls, floor and the ceiling. You can use a rug on the floor to absorb sound, thick velvet curtains on the walls, base traps in the corners. All this will improve the clarity, I chose to make the QD that size because it suits my wall and that is where I sit. Good luck.
Very nice
The math is based on channels to guide the sound rays so that they emerge with particular phase relationahips that redirect the sounds broadly...
Hey, I'm surprised to see you left the sides of the wells open, I mean sound goes all ways, I think it's necessary. This way the diffuser only works for sound that's aimed straight at it, I'd imagine. I'm drawing the outlines of a fractal diffuser onto a piece of plywood and the surfaces will be made from pinewood, in my language (grenen). It will be a ton of cutting, but it's alright, everything better than spending 35K haha
The idea is so that sound waves will get trapped under these walls. Without it, we simply reflect them in another direction. Either way is effective.
Hi John, great design and info, thanks for sharing.
Just a thought, how you have the two side by side, do you think that by flipping the second one so they were symetrical would it change the way it responds? or in theory would it work the same way?
Just thinking from an asthetic point of view, although they do look great side by side as you have them.
I think they would work either way because you need to remember that mathematics aside, you are creating an environment on your wall that with diffuse excess sound waves. The purist may argue semantics but you could hang a thick woollen blanket on your wall an still achieve a reduction in excess reflective sound which in turn will add clarity to your listening environment. The QD just look nice than a blanket. Having said that, I do intend to make a few absorber panels and base traps one day for the walls and upper corners of the room.
If they turn out as good as your diffusor did, they will look great.
@JohnCranberry23 I have a question. Did you consider the width of the rooftop's timber impacting the final calculation of each well's depth? Because maybe you are adding like one inch or so to whatever measurements the diffuser calculator gave you for those wells. I'm thinking about building one of these myself, I find this so inspiring. Thanks for your answer, I wish you my best regards from Chile!
Saludos. Lograste hacerlo finalmente? Que te pareció el resultado finalmente y sobre todo el efecto sonoro? Gracias desde Puerto Rico.
iff X^2 = b (mod p), then there exist a quadratic residue b. b belongs in Group of residue of modulo p.
did you do a before and after acoustic test of the room to show the difference.
I think you need absorption in your room (like corner bass traps). Diffusion is a secondary thing. I hear a ton of flutter echo in this vid and also in your star wars trailer.
+Julius Bernotas Agree, I will make some one day.
It's a combination of absorption (mid-high, and low frequency) and diffusion. There are two ways to handle flutter echo, you can have diffusors or absorption, both will work. It also depends on the room and it's dimensions.
Back then the camera I used wasn't very good. I have a video recently with Dolby Atmos vs DTS. Check that out.
Thx for sharing , That looks beautiful. However does it work like the solid ones. Thx
I also like building things so it's a great project.
Also each strip 1.5 inches is good ?
I works fine. It is only a small part of the room, but because it's directly behind my head, it eliminates reflection. strips should be around 2 inches, as long as they are staggered
@@JohnCranberry23 thanks for replying.
When the time comes I'll build one thx again.
It is still reverberating
He mentions recording audio in a different room.
diffusor is not an absorber
wanting to build this for my bedroom that is a little echoe, to put behind my bed. any new lessons learned since then to add? cheers good vid
SilkMilkJilk not really. All I can say that it’s still there hanging behind the lounge. Just plan it well before you buy the wood and dry fit the pieces before gluing it. Use quality wood glue because every now and then I dust it with a duster gently so I don’t knock it loose. Good luck.
@@JohnCranberry23 Thanks mate, much appreciated!
MEGAHERTZ Hahahaha ok
Looks cool, but it's 100% not a QRD, so it will not be predictable in its response.
You may get a good result, you may not. It's basically down to luck.
If anyone's looking at this video for reliable information, You probably don't want to follow this design.
Can you please fine that website for calculations. The link in the comment section is dead.
Doubt it works the same way as a diffuser with the wells having walls, but it would still diffuse. I see it as another option, kind of like Hoffa diffusers. I'd build this just to try it out.
One last question, if you could choose between a very heavy-hard timber and a softer type of wood, to get the best performance out of this design, what would it be?
Como talar un alerce I would go with a medium to soft density because hard wood is tough to work with and it’s heavier.
Hardwood tends to be more expensive too.
How many hours did you spend in total to make one? How much money did you spend in making one? Just curious.
+Oneness100 Actual hours..hard to say, but if I had to guess I would say maybe 20 to 30 actual hours not including drying time or planning. Planning is the most important part - if you plan well before buying anything, you will save money. The cost would be around $150 in timber for each. You don't have to spend heaps of money on the wood, just find something soft to medium hardness and nice looking. Good luck.
@JohnCranberry23 what is the length of each column before the frame?
Andrew James Each Column is around 90 cm long. It's up to you how long you make it. You can make it cover the whole wall from top to bottom if you wanted. But you only need to trap / diffuse the waves at ear level. I filled the wall above my lounge so I made it long enough to cover that part of the wall only. The width is determined by the channel sizes and prime sequence you choose.
Awesome! What did you use to mount it to the wall?
Just some HD frame mounting hooks. Go to a hardware store and buy something that easily supports the weight. You don't want them falling on your head as you watch a movie. LOL
What kind of wood did you use? Did you cut them all or they came ready to install?
I used Meranti, but you can use what ever you have in your area. I did cut the wood in accordance to the quadratic equation specs.
Im thinking about building something like this but the pieces of wood in the front (diffusors) would be pvc/tube pieces instead. Cut either in half or 1/3 with the concave part facing the back. My theory is that what ever hits the front will be diffused and whatever gets between and hits the back will be trapped by the concave part of the pvc/tube. Any input on how efficient that would be?
It would work but would it look nice? The concave and convex theory is great. You could use pvc edging strips and cut them to size. The concave would face back like you said and trap the waves and the convex would disperse them. Good luck
@@JohnCranberry23 thanks for your reply. Of course there would be some sort of treatment for aesthetical purposes. Perhaps some paint. I even thought about using carboard tubes instead and cover the exposed (convex) part with some sort of wallpaper or fabric. I just wasnt sure on the science part 😅.
@@LosantoBeats if it’s going to hang in your wall, make sure it’s pretty to look at. 🙏
Not exactly. Trapping sound needs mass, not a shape, primarily. Whatever is unable to escape through the concave face, it would actually reflect back in a deflected direction, and bounce off the back surface, with a random possibility of either losing all the kinetic energy in between reflections, or finding some escapable mass of matter coming back into your room.
More importantly, the frequencies that have that chances of getting "trapped in your pvc pipes" are only the very higher ones. Low frequencies won't even consider those pipes to be a barrier, they'd simply transmit through! (Low frequencies+ higher wavelenghts, hence they need space).
Diffusors and deflectors are meant for velocity - phase/amplitude grating, and what your theory is relevant for (to a very basic extent) is pressure trapping (not velocity), where your pvc MIGHT act as a membrane. Whereas diffusors and deflectors are meant for velocity - phase/amplitude grating. But, sound pressure generally builds up in the lower frequencies only, and once again, it needs a lot of volume to trap low frequencies. Plus, for membrane based traps, your trap neds to be airtight, pressure just escapes wherever it finds room.
Hi John, are the height measurments of the columns from the top front surface to the ply wood back? many thanks M
The back. So to simplify. The individual pieces are cut to the exact heights of the formula. The covers (strips) sit on top.
@@JohnCranberry23 but if You do in that way, the total height of the strips will be the height on the formula PLUS the "thickness" of the strips.. am I wrong? thanks! :)
@@massimilianofontana No because the ratio will be true under the strips and above the strips because the thickness is constant. Remember it's a ratio, not a specific length. If you doubled the lengths the ratio would still be true.
@@JohnCranberry23 THANKS! :)
How do u know what u need/want to defuse?
Do you have any insight into how this design might sound differently from the more standard design where each well has a wall separating it? I am curious if the open design has implications on how the sound is reflected versus how the the sound is reflected with the walled design. Were you able to have a comparison at all between yours and a standard design?
Interesting question. Maybe someone has the right answers by now? 🤔
@@LowEndStrings Yeah, same curiosity here
Sorry but this is not a QRD- the slots need to be enclosed for it to work as intended. Furthermore, even the thickness of the "walls" is to be precisely as per calculations, as is the width and depth for each slot. That's just physics. Not an opinion.
I understand your point and have to disagree for the simple reason that an empty flat surface will do nothing to diffuse the excess sound waves passing by my head, however my QD will and does actually diffuse, trap and break up sound. waves. Difficult to prove unless I have sound testing equipment to show the difference. However, I sit there and watch movies on my BenQ projector, Yamaha 7 x 150w Receiver and Klipsch speakers with the QD mounted behind me and it does sound fricken awesome. Don't believe me? Come over one Saturday night.
There is nothing to disagree about. That is NOT a QRD diffuser. ALL QRD diffusers are based on prime numbers and a center frequency. Based on *that* [chosen] frequency there is a *minimum* distance from listening position to diffuser. For example, let's say one wanted to make a QRD based on the number 7 and a design freq of 675hz, the MINIMUM distance between diffuser and listener would be around 5 feet. I am not making this stuff up, it's science and therefor it's NOT an opinion. You made an art piece, akin to a hanging picture but, it's not a QRD. You can't disagree with science :)
Gio, you're right. Got to have each well/trough enclosed.
It may not technically qualify as a QRD diffuser, but that doesn't mean it's not an extremely effective diffuser! It's more closely related to a stepped diffuser, which is not only a very popular and effective design, but which has been shown in certain tests to outperform QRD diffusers. There is a thread on gearslutz in which Tim Perry of Argen (open-source DIY diffuser design company) references a paper he wrote in which the stepped diffuser comes out on top. Honestly, I think John's design here could potentially have advantages over a normal stepped diffuser due to the "bridges" trapping sound underneath.
John, you should send your video/design to Tim @ Argen and see what he thinks. Very cool! I may build a huge one for my studio if it checks out.....in fact I may send him a link to this video to find out for myself.
Either way, great job and thanks for taking the time to document and post this! Aloha!
Gio is correct that this is not technically a QRD diffuser. However, it is still a diffuser. That "art piece" statement was inaccurate and out of line.
your border around that snt the same depth as the overall dimensions. is that optimum ? i seen acoustic fields guy doin a border on his diffusers ?
kingdizzyworld The border is simply for looks and extra strength. It is the front pieces (quadratic sequence) that do the diffusing and scatter the sound waves. The borders would also assist in trapping the waves. I watched Super 8 last night, hadn't seen it since the cinema release ages ago and when the train crash scene came up it shook the room. I still need to make absorbers for the room, but I have no complaints with the diffuser I built as it does a great job in diffusing the excess sound waves that hit the wall behind me.
yeah i see ! i like the science of the diffusers ! : ) border optional then !
actually no. without the slots being enclosed it doesn't work as per calculations. It's important that each slot be enclosed.
You are aware that you need to figure out what Prime sequence you need which is dependent on distance between the listener and the diffusor.. Sure, the higher Prime will yield a wider frequency range that it will handle, but it also requires a longer distance between it and the listener. Obviously once it's built, where you position with in the room is also important and that's more dependent on room usage, etc.
Interesting, do you have something to link with related measurements?
@@gabrielemarchetti7793 There's a video that was on Acoustic Fields where he shows the calculation.. Give me some time and I'll check their videos (over 500) to see if I can find it. :-). I'll post a link to it.
@@gabrielemarchetti7793 Here's a list of videos covering Diffusers to watch.
th-cam.com/video/fB3EsOqYZ6A/w-d-xo.html
th-cam.com/video/8OYYnGk30Qg/w-d-xo.html
th-cam.com/video/pTOfXlxGtZk/w-d-xo.html
th-cam.com/video/A4fRoLMxZ1o/w-d-xo.html
He use a QRD17 but used 17mm ( about 6" ... X4 = 24" x 2 = 48" away from the wall ) as his deepest base point. The sofa is back to the wall though. But, this is a different type of diffuser. If he is happy with the results it's fine.
It's only 17mm deep? ARGH!!! it should be more like 16inches deep for Prime 17.
Is there another calculator? This one doesn't work. The link.
Not that I know of. I haven't needed to look since I built it. Just Google, there should be something out there I'm sure.
It´s the same website, but with a changed link, so just remove the end and navigate further. There is a ton of acoustic information here including calculators for different builds:
www.mh-audio.nl/
This is a direct link to QRD:
www.mh-audio.nl/Acoustics/Diffusor.asp
Hm, this is no diffuser. It does not work, since sound waves will totally shun the open wells. You will have to close them in order to obtain an effect at all.
That's really neat wall art, but it's not a Quadratic Residue Diffuser. Without walls separating the individual wells it's only wall art.
This is actually called a volume diffuser.
A couple months... bruh
just rename it to diffuser fail
You know it's easy to criticize from afar. Come sit in my lounge room and I'll play a DTS HD movie and you will quickly experience the clarity because it chews up excess sound waves that would normally bounce off that wall and back in your ear drums. Go make your own any way you like.
@@JohnCranberry23 I like you, sound mind. No progress without people who think out of the box...
This is a joke, yes?
No, it actually works very well my sceptical friend.
Well if you think it won't work. You'll have a nice piece of art work .
So it does more than control frequency.
Its also nice to look 👀at.
They do work. I believe every theater /school music rooms/recording studios. Have some sort of diffusion.
@@jimmyFX Diffusors work. This is not a diffusor, just something vaguely prtty
Ok. Hes got a piece of art (not diffusor)that changed the sound of his room.👌👍
@@jimmyFX He's got a piece of art. Leave it there
Or just write some songs.
says the guy looking at a video on how to make their room sound better. fuck off
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