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Room treatment help

post #1 of 42
Thread Starter 
Does anyone have a good article or website about the specific placement of diffusers along with absorption panels? I've found articles that do one or the other but none that help with placing both.

I have 5 absorption panels I have built now that I am going to hang in my room, they are 2'x4' and 2" thick using roxul RHT80. I understand that I have to sit at my listening position and use a mirror along the walls and place them where I can see the speakers. I have also read to put diffusers on the first reflection point, and absorption on front and back walls. Another thing I read said don't put absportion on front walls. So where do I want to put my absorption panels, I am also interested in putting up some diffusers.

I want to build a couple diffusers as well, but am unsure of the placement. I want to build some of these http://www.pmerecords.com/Diffusor.cfm , is there any reason to build the >1200hz diffuser over the >800 hz diffusers other than the fact that it is 4" deep instead of 8" deep?

Where do I place diffusers? Behind the listening position? First reflection point? How many 1.5' x 1.5' diffusers should I build?

Here's a very rough picture I drew in 60 seconds of my room.


Also what is the best way to hang panels on walls? Something fairly cheap, I checked out home depot and stuff but all their options are like 6 bucks a panel and that seems like a lot.

Thanks
post #2 of 42
Good question smile.gif

Unfortunately, your room is really too small for proper diffusion. When utilizing diffusion, in order for the energy to fully manifest itself into a proper diffuse field, ideally the minimum seating distance needs to be three times the longest wavelength diffused.

Also, with your LP being up against a boundary, you need massive, thick absorption there, .. as thick as you can manage in my opinion/experience.

Here is an outstanding diffusion source. However I really feel in your small room, absorption would be most appropriate.
post #3 of 42
Thread Starter 
Quote:
Originally Posted by FOH View Post

Good question smile.gif

Unfortunately, your room is really too small for proper diffusion. When utilizing diffusion, in order for the energy to fully manifest itself into a proper diffuse field, ideally the minimum seating distance needs to be three times the longest wavelength diffused.

Also, with your LP being up against a boundary, you need massive, thick absorption there, .. as thick as you can manage in my opinion/experience.

Here is an outstanding diffusion source. However I really feel in your small room, absorption would be most appropriate.

You think I shouldn't use any diffusion panels? I have 5 absorption built already and am not building more, you think that adding diffusion panels is completely pointless and not worth it? I really want to build some I think they look cool and I enjoy making things so...

I guess I was unclear about the article, I was looking for one that will explain proper placement of absorption AND diffusion at the same time.

My LP is probably 1-2 feet from the back wall.

I don't understand what you mean about the room being too small, because if the minimum seating distance needs to be 3 times the longest wavelength, if the lowest frequency being diffused is 800 hz, isn't the wavelength of 800hz only 42.5 cm long? so that makes the minimum listening distance 127.5 cm or about 4 feet? Why is a listening distance of 9 feet not acceptable for that?
Edited by WagBoss - 6/17/13 at 12:41pm
post #4 of 42
Quote:
Originally Posted by WagBoss View Post

I really want to build some I think they look cool and I enjoy making things so...

That's refreshing! Few around here easily admit to an approach because it looks cool, or they merely want to ... because they enjoy making stuff...! Seriously, that's great, go for it. That's a good reason.

Much can be learned from experimentation.

Quote:
Originally Posted by WagBoss View Post

I guess I was unclear about the article, I was looking for one that will explain proper placement of absorption AND diffusion at the same time.


http://www.realtraps.com/art_basics.htm

http://gikacoustics.com/articles/

These last two are superb, and quite suited for your scenario;
http://www.ethanwiner.com/acoustics.html#top


http://www.harmanaudio.com/all_about_audio/loudspeakers_rooms.pdf


Quote:
Originally Posted by WagBoss View Post

My LP is probably 1-2 feet from the back wall.

This is important, and very easy to address; you need a full absorption treatment, maybe 12" thick, behind the LP.


Quote:
Originally Posted by WagBoss View Post

I don't understand what you mean about the room being too small, because if the minimum seating distance needs to be 3 times the longest wavelength, if the lowest frequency being diffused is 800 hz, isn't the wavelength of 800hz only 42.5 cm long? so that makes the minimum listening distance 127.5 cm or about 4 feet? Why is a listening distance of 9 feet not acceptable for that?


3x wavelength from the diffusion panel, ... just makes the approach less feasible in many situations.
post #5 of 42
Thread Starter 
12" thick absorption panel? Why so thick? Even 4" of roxul block 100% of 125 hz and above. Do you have more explanation for that? How tall/wide of a panel would I need for that? Would a diffuser work behind instead of an absorption panel? I already built my absorption panels and wasn't planning on building more
post #6 of 42
Quote:
Originally Posted by WagBoss View Post

You think I shouldn't use any diffusion panels? I have 5 absorption built already and am not building more, you think that adding diffusion panels is completely pointless and not worth it? I really want to build some I think they look cool and I enjoy making things so...

You, me and Ethan Winer might be the only ones who actually like the aesthetics of acoustic panels. I've built a few 2D skyline diffusers because I think they look cooler than QRDs. They were a pain in the ass to build though and I didn't enjoy that part. I've made royal blue colored absorption panels that match very well with my cherry wood speakers/tv stand.

Yes, build some diffusers. Ethan Winer made a video where you can hear the difference diffusers provide... even in smaller rooms such as yours.
post #7 of 42
Thread Starter 
Quote:
Originally Posted by brandon_k_w View Post

You, me and Ethan Winer might be the only ones who actually like the aesthetics of acoustic panels. I've built a few 2D skyline diffusers because I think they look cooler than QRDs. They were a pain in the ass to build though and I didn't enjoy that part. I've made royal blue colored absorption panels that match very well with my cherry wood speakers/tv stand.

Yes, build some diffusers. Ethan Winer made a video where you can hear the difference diffusers provide... even in smaller rooms such as yours.

How many and where exactly do I put them?
post #8 of 42
Quote:
Originally Posted by WagBoss View Post

How many and where exactly do I put them?

I'm still learning myself, but - as far as I understand it - the typical placement of diffusers are:
1) Back wall
2) Side walls, above head level.
3) Ceiling.
post #9 of 42
Read the articles on Ethan's site. Placement depends on what you are trying to do. Side walls and ceilings are good places to control first reflections for conventional speakers. Placing them in corners and front/back walls helps control room modes (actually most anywhere will help, some places are better than others) and perhaps reflections from the rear wall that cause problems, etc.
post #10 of 42
Thread Starter 
Quote:
Originally Posted by DonH50 View Post

Read the articles on Ethan's site. Placement depends on what you are trying to do. Side walls and ceilings are good places to control first reflections for conventional speakers. Placing them in corners and front/back walls helps control room modes (actually most anywhere will help, some places are better than others) and perhaps reflections from the rear wall that cause problems, etc.

I have read them all. I understand where to place them if I had 20 panels and corner bass traps, I just don't know what the optimal places will be with my 5 absorption panels and 2-4 diffusor panels

I didn't make "bass traps" so I can't put mine in the corners, can I? I only have like 0.39 of absorption at 125 hz according to the specs http://www.roxul.com/files/RX-NA_EN/pdf/RHT80-3-30-10.pdf

So basically I just need to know if I should use diffusors on the first reflection point or should I use absorbers, and do I need any treatment on the front wall, and what is the cheapest way to mount them?
Edited by WagBoss - 6/18/13 at 12:42pm
post #11 of 42
Quote:
Originally Posted by WagBoss View Post

12" thick absorption panel? Why so thick? Even 4" of roxul block 100% of 125 hz and above. Do you have more explanation for that? How tall/wide of a panel would I need for that? Would a diffuser work behind instead of an absorption panel? I already built my absorption panels and wasn't planning on building more

You're too close for diffusion.

The thickness is to lessen the freq response peaks and dips at the LP. I'm not sure 4" of anything is full to 125hz, but the point is attenuate as deep as possible in frequency, to retain punch and FR smoothness commensurately.

I'd go 12", yes. If I had Safe-N-Sound, or 703 I'd use it, otherwise I'd likely compress some fluffy E-Cose style glass fiber, and go that route.
The approach I'd take would depend what material I had.


Here's some guidelines when considering thickness available for the treatment area;

For 4" thick, the dense stuff (OC703 or equiv) is the best.
For 4"-12" use 4" of 703 like and the rest air gap, or use Rockwool Safe-N-Sound up to 12"
For 12" and up, fluffy fiberglass approach works great.

Also, comparing equal amounts of volume doesn't work. Like 12, 4" traps vs. 6, 8" traps,... thicker isn't necessarily better. Oftentimes, covering more surface area and spreading the material around performed significantly better.

These suggestions aren't hard and fast rules. 8" of 703 still works great, perhaps it's just not the best use of the material. The air gap is the performance multiplier,... mind the gap cool.gif
post #12 of 42
Thread Starter 
I have never seen a panel that is a foot thick... do you have any links to something that says you need it that thick? From what I've read on Ethan's site and of pictures I've looked at, it seems like 4" is the thickest anyone's ever used.

It would weigh at least 80 lbs too...
post #13 of 42
Absorbers @ first reflection points on side wall and ceiling. Use the mirror technique or calculate these points. Most likely you'll use all 5 of your panels in these areas. But if your dresser and door and other stuff is in the way, then toss 2 absorbers on the front wall.

FOH makes a good case to avoid diffusion in this space. If you insist on putting them somewhere, then I'd suggest the back wall.

You should try to hang your panels so that there is a space behind them. In post #5 on the thread below there is a good detail of one method:
http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames#post_19947658
Edited by CubicleCrusher - 6/18/13 at 1:33pm
post #14 of 42
Quote:
Originally Posted by WagBoss View Post

I have never seen a panel that is a foot thick... do you have any links to something that says you need it that thick? From what I've read on Ethan's site and of pictures I've looked at, it seems like 4" is the thickest anyone's ever used.

It would weigh at least 80 lbs too...

Corner, super-chunk, style panels are thick like that.

P.S. - For example, the GIK Tri-Trap corner panel:
http://gikacoustics.com/product/gik-acoustics-tri-trap/

Standard Size: 23” x 16.5″ x 16.5″ and stand 47”
weight: 15 pounds

p.s.s - my recommendations come not from technical experience nor practical application, but from my own "how-to" and "where-to" conversations with GIK consultants, HT Installers and on-line resources. So take my advice with a grain of salt; I'm basically just regurgitating what I "think" they might say. But since you are such an experimenter, I figured I'd add in my two cents. I would also suggest that you invest in REW to take before-and-after measurements of each addition so you can quantify the changes with graphs-and-numbers. If you have a laptop with HDMI out, then $100 could set you up with a USB mic and you could experiment-and-measure-and-build to your hearts content.
Edited by CubicleCrusher - 6/18/13 at 1:39pm
post #15 of 42
Thread Starter 
Quote:
Originally Posted by CubicleCrusher View Post

Absorbers @ first reflection points on side wall and ceiling. Use the mirror technique or calculate these points. Most likely you'll use all 5 of your panels in these areas. But if your dresser and door and other stuff is in the way, then toss 2 absorbers on the front wall.

FOH makes a good case to avoid diffusion in this space. If you insist on putting them somewhere, then I'd suggest the back wall.

You should try to hang your panels so that there is a space behind them. In post #5 on the thread below there is a good detail of one method:
http://www.avsforum.com/t/1312693/diy-construction-methods-of-hang-able-acoustic-panels-not-fixed-frames#post_19947658

Ethan has a video that shows how diffusers help in even small rooms. Can I just attach the panels to wood blocks attached to the wall to keep it out about 1.5 inches?
post #16 of 42
Thread Starter 
Quote:
Originally Posted by CubicleCrusher View Post

Corner, super-chunk, style panels are thick like that.

P.S. - For example, the GIK Tri-Trap corner panel:
http://gikacoustics.com/product/gik-acoustics-tri-trap/

Standard Size: 23” x 16.5″ x 16.5″ and stand 47”
weight: 15 pounds

p.s.s - my recommendations come not from technical experience nor practical application, but from my own "how-to" and "where-to" conversations with GIK consultants, HT Installers and on-line resources. So take my advice with a grain of salt; I'm basically just regurgitating what I "think" they might say. But since you are such an experimenter, I figured I'd add in my two cents. I would also suggest that you invest in REW to take before-and-after measurements of each addition so you can quantify the changes with graphs-and-numbers. If you have a laptop with HDMI out, then $100 could set you up with a USB mic and you could experiment-and-measure-and-build to your hearts content.

yes, but 12" deep in a corner is really only a few inches out the wall. a 12" giant block sitting in the middle of a wall is weird...

Yes I have REW and all that stuff, my computer is at my desk, which is why I have a desk there.
post #17 of 42
Sounds like you are ready to go!

So yeah, just put some mounting blocks/spacers on the wall with molly screws or something, then get something equivalent to those z-clips from ATS acoustics ($12 for 12 hanging points) and you should be in pretty good shape.
post #18 of 42
Thread Starter 
I'm in canada so i probably can't get them for less than 100 dollars shipping lol
post #19 of 42
Quote:
Originally Posted by WagBoss View Post

I'm in canada so i probably can't get them for less than 100 dollars shipping lol

One word: Roxul
post #20 of 42
Quote:
Originally Posted by WagBoss View Post

yes, but 12" deep in a corner is really only a few inches out the wall. a 12" giant block sitting in the middle of a wall is weird...

I don't think they're weird, but I understand if one hasn't seen such things, ... one would.

One component to sound, is size. To adequately attenuate bass frequencies with velocity based absorption (fiberglass etc), you need space.
Either very thick yet fluffy insulation, or the more dense stuff, like 703 rigid, limited to 4" or so, however spaced off boundary with an equal air gap or more.


Also, it's helpful to understand that for bass traps, understand that the LF waves will typically diffract around your absorber. This reduces the pressure difference, that exists between the back and front, thus it's less effective overall. The gap does help if the absorbers are significantly big or the gap is closed off at the sides.

I agree, there's space considerations, and aesthetic considerations.
post #21 of 42
Thread Starter 
Quote:
Originally Posted by arnyk View Post

One word: Roxul

roxul has clips to hang panels? I already have my panels built out of roxul..
post #22 of 42
My guess if you are looking for a quick and dirty starting point: I would start with one panel over the dresser and another opposite on the other wall, two on the wall directly behind the listening position, and one from the ceiling roughly in the middle of the room. I would use spacers (foam, wood, whatever) for the wall panels and hang the ceiling panel from a couple of plant hangers with chains. See what it sounds like.
post #23 of 42
Thread Starter 
Quote:
Originally Posted by DonH50 View Post

My guess if you are looking for a quick and dirty starting point: I would start with one panel over the dresser and another opposite on the other wall, two on the wall directly behind the listening position, and one from the ceiling roughly in the middle of the room. I would use spacers (foam, wood, whatever) for the wall panels and hang the ceiling panel from a couple of plant hangers with chains. See what it sounds like.

Nothing in the corner? What about diffusers directly behind me and absorption panels in the rear corners?
Edited by WagBoss - 6/19/13 at 6:06am
post #24 of 42
I have about 100 of those ATS french cleats. If you want me to send some you way if you cover shipping I would be happy to.
post #25 of 42
Quote:
Originally Posted by WagBoss View Post

Quote:
Originally Posted by DonH50 View Post

My guess if you are looking for a quick and dirty starting point: I would start with one panel over the dresser and another opposite on the other wall, two on the wall directly behind the listening position, and one from the ceiling roughly in the middle of the room. I would use spacers (foam, wood, whatever) for the wall panels and hang the ceiling panel from a couple of plant hangers with chains. See what it sounds like.

Nothing in the corner? What about diffusers directly behind me and absorption panels in the rear corners?

Hmmm... You asked for opinions, I gave mine. Try it out (your plan) and see what you like, there's nothing lost in trying. Not even time, as it is a learning experience, and what I say over the 'net is just a guess, may be totally unrelated to what you find and like.

Now, to answer you, you said you had five absorbers. In the corners might help a little with the bass, but the speakers are not bipolar* and your absorbers are too thin to absorb signifcantly in the bass, so I chose to attack the first reflection points (side walls and ceiling) and the reflection from the wall right behind the listening position as the places most likely to corrupt the sound.

My experience with diffusors is that you need to be a little further away for them to work (sound) well, especially the smaller ones, and you did not say you had them, so I stuck with absorbers behind to help suppress the reflections from the wall behind. I also tend to side with those saying diffusion does not work as well in small rooms, because (a) the path length is small in small rooms and other items tend to break up the sound anyway, and (b) there is rarely room to put large diffusers in small rooms without sucking out too much volume and making the room even smaller. the other reason is time and cost; I have not done DIY diffusers in ages and simply don't have time now, and diffusors generally cost much more than absorbers (much harder to make).

A lot of this comes down to preference and experimenting until it sounds right to you. I measure my system but depend upon the DSP/EQ to compensate the hefty amount of absorption in my room. Ask on a forum like this and you'll probably get as many answers as people, then have to sift out the better responses. Have you asked Ethan directly? You can also send a room diagram to various other companies and they'll provide suggestions.

All IMO - Don

* I assume; if they are dipoles, then a panel behind each would be a good idea.
post #26 of 42
Thread Starter 
Quote:
Originally Posted by DonH50 View Post

Hmmm... You asked for opinions, I gave mine. Try it out (your plan) and see what you like, there's nothing lost in trying. Not even time, as it is a learning experience, and what I say over the 'net is just a guess, may be totally unrelated to what you find and like.

Now, to answer you, you said you had five absorbers. In the corners might help a little with the bass, but the speakers are not bipolar* and your absorbers are too thin to absorb signifcantly in the bass, so I chose to attack the first reflection points (side walls and ceiling) and the reflection from the wall right behind the listening position as the places most likely to corrupt the sound.

My experience with diffusors is that you need to be a little further away for them to work (sound) well, especially the smaller ones, and you did not say you had them, so I stuck with absorbers behind to help suppress the reflections from the wall behind. I also tend to side with those saying diffusion does not work as well in small rooms, because (a) the path length is small in small rooms and other items tend to break up the sound anyway, and (b) there is rarely room to put large diffusers in small rooms without sucking out too much volume and making the room even smaller. the other reason is time and cost; I have not done DIY diffusers in ages and simply don't have time now, and diffusors generally cost much more than absorbers (much harder to make).

A lot of this comes down to preference and experimenting until it sounds right to you. I measure my system but depend upon the DSP/EQ to compensate the hefty amount of absorption in my room. Ask on a forum like this and you'll probably get as many answers as people, then have to sift out the better responses. Have you asked Ethan directly? You can also send a room diagram to various other companies and they'll provide suggestions.

All IMO - Don

* I assume; if they are dipoles, then a panel behind each would be a good idea.

Thank you for the explanation. Makes sense. I am considering doing what you said and also building a couple specific corner bass traps.
post #27 of 42
Thread Starter 
Quote:
Originally Posted by beastaudio View Post

I have about 100 of those ATS french cleats. If you want me to send some you way if you cover shipping I would be happy to.

is the french cleat the "professional installation kit" http://www.atsacoustics.com/item--acoustic-panel-installation-hardware--IK12.html
post #28 of 42
The cheapest/easiest corner trap is to cut sheets of OC-70x or Roxul into triangles and stack them. You can tack cloth to the front to make them look better.
post #29 of 42
Thread Starter 
Quote:
Originally Posted by DonH50 View Post

The cheapest/easiest corner trap is to cut sheets of OC-70x or Roxul into triangles and stack them. You can tack cloth to the front to make them look better.

yep gonna make these possibly http://nagasakisound.com/how-to-build-corner-bass-trap/

will cost me about $160 for 4 traps, which will cover floor to ceiling of two corners, not too bad. And it's nice they can just sit on the floor and on one another
post #30 of 42
Quote:
Originally Posted by WagBoss View Post

Quote:
Originally Posted by arnyk View Post

One word: Roxul

roxul has clips to hang panels? I already have my panels built out of roxul..

I can't believe that someone is going to charge you > $100 for mounting clips.

I was talking about absorptive materials, and if you are already using Roxul from a local source then you are pretty much doing what you can. Then I remain mystified about the > $100 shipping charges.
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