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Post by vitastudio on Mar 2, 2017 21:43:08 GMT
I have the problem of stationary waves in my control room
- size 3.6 x 3.2 m
- walls : 2 beton and 2 red brick
The simple test I did taking a sin wave synth and searching the piano keys with resonance :
* C1=261.63Hz -- big
* C0=130.82Hz -- a little bit smaller
* around -F#1=92.5Hz -- very big
* around -F#2=46.25Hz -- huge !
- but frequency analyser shows the frequence around 64Hz. this is closer to -C1=65.41Hz
It seems that F# - C could be demi-wave frequencies, of the same wave (a quint) ?
How to define precisely the frequencies posing problems ? the location of the stationnary wave ?
Which bass traps would be most suitable for this small room ?
Thank you in advance for your help !
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Post by Hexspa on Mar 3, 2017 10:12:59 GMT
amroc.andymel.eu/ You can use this calculator. Plug in your dimensions then mouse over the piano graph to hear your room boom. You can also convert wavelengths into room dimensions using this chart www.phy.mtu.edu/~suits/notefreqs.htmlJust find which frequencies your room corresponds to. You room will also boom if it's dimensions are half, double or 1.5x any frequency. That's not even accounting for nulls which are a little more difficult to calculate. You'll probably need between 20-40 4" 2x4' rigid porus absorbers to get a respectable response in your room. Thicker fluffy corner traps will help too i.e. "super chunks". -m
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Post by vitastudio on Mar 3, 2017 18:48:45 GMT
amroc.andymel.eu/ You can use this calculator. Plug in your dimensions then mouse over the piano graph to hear your room boom. You can also convert wavelengths into room dimensions using this chart www.phy.mtu.edu/~suits/notefreqs.htmlJust find which frequencies your room corresponds to. You room will also boom if it's dimensions are half, double or 1.5x any frequency. That's not even accounting for nulls which are a little more difficult to calculate. You'll probably need between 20-40 4" 2x4' rigid porus absorbers to get a respectable response in your room. Thicker fluffy corner traps will help too i.e. "super chunks". -m could you give precise indications on how to place bass traps and thier types? if it is possible with the references on how it looks like and their materials, please?
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Post by Ethan Winer on Mar 3, 2017 21:02:09 GMT
The best places for bass traps are (in approximate order): 1) Straddling corners at an angle. 2) The rear wall behind you. 3) The front wall. 4) The ceiling. Note that rectangle rooms have 12 corners, not just four where walls meet other walls. In most rooms, including yours, it's a mistake to plan for bass traps that target specific frequencies. This recent article addresses all that you asked, and a lot more: Bass Trap Myths
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Post by vitastudio on Mar 3, 2017 22:56:46 GMT
The best places for bass traps are (in approximate order): 1) Straddling corners at an angle. 2) The rear wall behind you. 3) The front wall. 4) The ceiling. Note that rectangle rooms have 12 corners, not just four where walls meet other walls. In most rooms, including yours, it's a mistake to plan for bass traps that target specific frequencies. This recent article addresses all that you asked, and a lot more: Bass Trap Mythsthank you for this link, I'll read
I did some measurements with REW soft, perhaps, it'll give you more details and precision on my room here are some screenshots and data file for REW drive.google.com/open?id=0B9tdbuSyLyqHc2FSUEt0dk9Zb1k thanks in advance for your precise advices on how to trap the basses
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Post by vitastudio on Mar 3, 2017 23:02:31 GMT
if I understand well the theory, there are 3 fundamental stationary waves / frequencies to trap. I'll be happy of any help to solve this problem as I'm new in acoustics, any detailed pictures, explanations, links would be highly usefull!
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Post by Joe Hamilton on Mar 4, 2017 2:31:01 GMT
The best places for bass traps are (in approximate order): 1) Straddling corners at an angle. 2) The rear wall behind you. 3) The front wall. 4) The ceiling. Note that rectangle rooms have 12 corners, not just four where walls meet other walls. In most rooms, including yours, it's a mistake to plan for bass traps that target specific frequencies. This recent article addresses all that you asked, and a lot more: Bass Trap MythsI gather that you've listed these locations in order of importance/effectiveness. Personally, I cannot manage to treat all 12 corners. Can you please put a finer point on item 1 - prioritizing the 12 corners in order of effectiveness? EDIT: Nevermind. I just found the Realtraps article ( link ) discussing same.
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Post by Hexspa on Mar 4, 2017 10:47:31 GMT
I'm not above giving away my free book on small room acoustics specifically targeted to first time treaters hexspa.com/listening-room-ebookI'm surprised Ethan says that the front wall is more important than the ceiling. I don't have evidence to the contrary but, given that it typically has more surface area than a front wall, you'd think the ceiling would be more important. Vita - by three frequencies you mean the basic axial modes in a room, right? That's true. I don't know how the "angled corner" method become so ubiquitous. Maybe since bass build up in the corners. However, it seems to make things confusing for newbies. The bottom line is that by adding absorption you're removing walls. No walls, no modes, no reflections. Therefore, the more you can get in the way of your walls, i.e. more square foot coverage with broadband absorption, the less problems you'll have. For future reference the only graphs you'll need to post are your waterfall and SPL (solo6.png type). -m
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Post by vitastudio on Mar 4, 2017 11:41:54 GMT
Thank you Michael, I'll read your book. yes I mean the basic axial modes, the other are thier ratios I guess for some reasons, it is not my room, I can not do modifications on the ceil, I can only insert movable panels in the conners and install something on the floor, also movable. I'll go to shop now could you advice me materials to fabric bass traps for firstly 4 main conners please ? what density glasswool should be? how to compute the right size of conners ? would the conners be more effective than tube traps ? in the conners ? I have also the possibility to install something between the monitors in the middle on the table and under the table. would tubes be a good stuff for this ? and I can also add a glasswool on the table with displays, that is the exact middle of the room, where the second three waves are presented. would be it the efficent solution ? I have also some space for front traps, but there is a window on the front wall. I guess that rectangle helmholtz bass trapes could be good decision for front and low side walls...is not it?
and more technical questions :
besides materials and its density to choose, namely - glasswool ? if yes its optimal density, is density influence considerably ?
how to compute the right dimensions of helmholtz bass traps? tube bass traps ?
from the Ethan paper I understood that there is no necessity for tuned bass traps, but for my case the broadband bass trap have to absorb the 40Hz stationnary wave (1 axis mode).
thank you so mush for your feedback and advices !
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Post by rock on Mar 4, 2017 14:12:48 GMT
Hi vitastudio, I've been following this thread and, with all due respect, it is my impression that you really have not done your homework. For instance, did you google Helmholtz resonant absorber calculations? I don't have the link handy but I know it's "out there". Many, if not all of the questions you ask have been asked and answered before in other threads and can be found either in the archives here, in Ethan's previous forum (I'll look for the link for you), or on Ethan's website and book. Here's that link: forums.musicplayer.com/ubbthreads.php/forums/24/1/Ethan_Winer_The_Audio_ExpertCheers, Rock
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Post by Hexspa on Mar 5, 2017 9:09:39 GMT
Thank you Michael, I'll read your book. yes I mean the basic axial modes, the other are thier ratios I guess for some reasons, it is not my room, I can not do modifications on the ceil, I can only insert movable panels in the conners and install something on the floor, also movable. I'll go to shop now could you advice me materials to fabric bass traps for firstly 4 main conners please ? what density glasswool should be? how to compute the right size of conners ? would the conners be more effective than tube traps ? in the conners ? I have also the possibility to install something between the monitors in the middle on the table and under the table. would tubes be a good stuff for this ? and I can also add a glasswool on the table with displays, that is the exact middle of the room, where the second three waves are presented. would be it the efficent solution ? I have also some space for front traps, but there is a window on the front wall. I guess that rectangle helmholtz bass trapes could be good decision for front and low side walls...is not it? and more technical questions : besides materials and its density to choose, namely - glasswool ? if yes its optimal density, is density influence considerably ? how to compute the right dimensions of helmholtz bass traps? tube bass traps ? from the Ethan paper I understood that there is no necessity for tuned bass traps, but for my case the broadband bass trap have to absorb the 40Hz stationnary wave (1 axis mode). thank you so mush for your feedback and advices ! Great questions, Vita. Sounds like you have an inquisitive mind and an aptitude for categorization - just what an autodidact needs Rock is right - often several seemingly unrelated questions can be resolved by finding and acting on an established course of action. In other words, if you read Ethan's articles and implement the advice you'll be far better off than getting a la carte answers in a forum format. Basically read the material, reread it, google it and read at least three related articles. Then, if you're still confused, make a post with that single point and endeavor to understand it fully before moving on. -m
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Post by Ethan Winer on Mar 6, 2017 16:26:36 GMT
Just one point toward Hex's comment about the ceiling: Yes, the ceiling is usually larger than the front wall, and it's important too! But it's easier to treat the front wall than the ceiling. In truth, all six surfaces are good places for bass traps. Just as all 12 corners are good. Which surface, or corner, will help a given single frequency most depends on where the speakers and listener are. Room acoustics has no concept of up, down, left, or right. Think of a room as a 3D object floating around in space.
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Post by Ethan Winer on Mar 6, 2017 16:34:06 GMT
For Vita: Yes, 40 Hz can be targeted with tuned traps, but I honestly don't know much about Helmholtz absorbers. I used to build tuned wood panel traps, and you need to cover a lot of surface with those, just as with porous traps. Looking at your waterfall.png file it seems there's no output at all between the huge peak at 45 Hz and the huge peak at 92 Hz. So I suspect something is wrong with your measurements. Really, for a room this size, just treat it with as much broadband bass trapping as you can.
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Post by vitastudio on Mar 6, 2017 17:07:21 GMT
For Vita: Yes, 40 Hz can be targeted with tuned traps, but I honestly don't know much about Helmholtz absorbers. I used to build tuned wood panel traps, and you need to cover a lot of surface with those, just as with porous traps. Looking at your waterfall.png file it seems there's no output at all between the huge peak at 45 Hz and the huge peak at 92 Hz. So I suspect something is wrong with your measurements. Really, for a room this size, just treat it with as much broadband bass trapping as you can. sorry that I did not read all books and all forums and all details many times ... just because I have not so much time as wished... for this reason I try to ask the concrete questions that optimize the time of reading. as I'm not specialist of acoustic but musician ) from the Ethan's answer I understand that usual broadband bass traps are suffisant for my room as for measurement I used a usual condenser mic, not tape one. and I did it at lower volume I guess with your professional permission, could I ask you my stupid questions without reading forums, please ? - advantages/disadvantages rockwool vs glasswool ? - what is the optimal density of rockwool/glasswool ( kg/m3 ) are optimal for 40-100 Hz traps ? - what is the optimal width for the size of 1.20 x 6.0 m ? - advantages/disadvantages rectangle vs tube form ? thank you!
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Post by Hexspa on Mar 7, 2017 14:50:26 GMT
For Vita: Yes, 40 Hz can be targeted with tuned traps, but I honestly don't know much about Helmholtz absorbers. I used to build tuned wood panel traps, and you need to cover a lot of surface with those, just as with porous traps. Looking at your waterfall.png file it seems there's no output at all between the huge peak at 45 Hz and the huge peak at 92 Hz. So I suspect something is wrong with your measurements. Really, for a room this size, just treat it with as much broadband bass trapping as you can. sorry that I did not read all books and all forums and all details many times ... just because I have not so much time as wished... for this reason I try to ask the concrete questions that optimize the time of reading. as I'm not specialist of acoustic but musician ) from the Ethan's answer I understand that usual broadband bass traps are suffisant for my room as for measurement I used a usual condenser mic, not tape one. and I did it at lower volume I guess with your professional permission, could I ask you my stupid questions without reading forums, please ? - advantages/disadvantages rockwool vs glasswool ? - what is the optimal density of rockwool/glasswool ( kg/m3 ) are optimal for 40-100 Hz traps ? - what is the optimal width for the size of 1.20 x 6.0 m ? - advantages/disadvantages rectangle vs tube form ? thank you! Vita, to be fair, no one asked you to go to those lengths. Neither am I an acoustics specialist; others and I volunteer our time to help and learn. Regardless, a "usual" condenser is not the correct instrument for the job. I will give my best answers as far as I can: rockwool/glasswool - standard fiberglass performs better than generic mineral wool but the differences can be overcome with additional density, thickness and/or coverage. I use 8lb mineral wool. If you use OC70X you can use 3-5lb. If your absorbers are greater than 8" thick you can use less dense "fluffy" fiberglass for better cost/performance ratio. What do you mean by 1.2x6m? That's like 4x19' You initially said your room was 11.81'x10.49'. I already looked it up and there is no ideal ratio for your room. The best you can do is create as much volume as possible without using any common factor as a dimension like 5', 10' or even 6'. That leaves 7' or 4' and their multiples assuming we're using the first dimensions you gave in OP. I don't know anything about rectangle or tube pressure absorbers. -m
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