AudioCircle
Audio/Video Gear and Systems => The Acoustics Circle => Topic started by: vanderstephen on 15 Apr 2012, 01:06 pm
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Hi. I am DIY'ing some acoustic treatment in my listening room. I am in the process of making absorption panels for behind the speakers using 3.5" thick rock wool (Roxul Safe and Sound). For aesthetics, I do not want something that thick on the side walls and I can't find rock wool locally that's any thinner. I can get 2" thick Auralex Wedge foam from a local guitar center (that's considered diffusion, not absorption, right?). Would that be just as effective to use at a first reflection point as rock wool? Would the egg crate and wedge foam be effective for use on the wall behind the listening position?
Thanks!
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Hello Vanderstephen,
I understand your questions and it would be nice if this would work. However, the thickness (and material properties) relates to the effectiveness of the absorber. Most simply, the thicker it is the lower in frequency it will absorb effectively.
The Auralex wedge is an absorber (not diffusor). Inch per inch, the Auralex foam is ~50% as effective as the rock wool you've found.
So the answer is that no, 2" Auralex wedge foam would not be as effective as 3.5" rock wool at those locations in terms of absorption.
Now, the other topic altogether is in your thread topic: diffusion vs absorption. That's a deeper question. Please feel free to post a diagram of your room, maybe a pic or two and details on your speakers. I could then offer a better answer on this question.
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You could peel off layers of the 3.5" Rouxl until you achieve the 2" thickness.
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Thank you for the replies so far. I will try to post a photo later this week. Hopefully we'll determine that I can get by with just a few squares of the Auralex wedges per sidewall.
I tried peeling the thicker Roxul, but it comes off in chunks- it was worth a shot.
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Can you use a knife and slice it to the desired thickness
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I would advice you to use absorption for early reflection points in the front of the room (sidewalls, ceiling and carpet on the floor). Basstrapping behind speakers and in corners. Use diffusion on rear sidewalls or backwall, but make sure you have the distance that's required.
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Use diffusion on rear sidewalls or backwall, but make sure you have the distance that's required.
What is the required distance?
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It depends on the type of diffuser (i.e. true diffusion vs diffraction or scattering), but assuming something like the ones from RPG, look here and click on page 46: http://books.google.com.au/books?id=jYBR-aL2vJMC&lpg=PP1&dq=Acoustic%20Absorbers%20and%20Diffusers&pg=PA46#v=onepage&q=%22spatial%20response%22&f=false
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Diffusion is appropriate when the listening distance is at least 3 wavelengths away from the diffusor of the diffused frequencies. So a 6 inch deep diffusor (500 hz) should be 7 feet from the listener.
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Hi
If you use Wing diffusor from SMT there is no need for any 3 wavelenght away from the diffusor. The Wing is perfectly suitible for small rooms. You can sit around 20 centimeters from it without any degradation from Wing's diffusions performance.
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If I use the Cardas method of positioning, my listening seat will be six feet away from the back wall. Using your formula, one third of 72 inches is 24 inches, and a 24 inch wave is 565 Hz. In this case, I should build or buy a diffuser effective, if possible, down to 565 Hz?
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If I use the Cardas method of positioning, my listening seat will be six feet away from the back wall. Using your formula, one third of 72 inches is 24 inches, and a 24 inch wave is 565 Hz. In this case, I should build or buy a diffuser effective, if possible, down to 565 Hz?
That's correct. But remember that 3 wavelengths is the minimum recommended distance. You might want to stick to diffusors that are effective down to about 700-600 Hz.
If you end up buying something, stay with products that show measurements. Like for instance RPG:
http://www.rpginc.com/
And you want 1D diffusors that only diffuse in the most important horizontal plane and don't waste energy in unwanted directions. You will need several for a good effect.
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That's correct. But remember that 3 wavelengths is the minimum recommended distance. You might want to stick to diffusors that are effective down to about 700-600 Hz.
If you end up buying something, stay with products that show measurements. Like for instance RPG:
http://www.rpginc.com/
And you want 1D diffusors that only diffuse in the most important horizontal plane and don't waste energy in unwanted directions. You will need several for a good effect.
1) Are there consequences for buying diffusers effective to lower frequencies? Or they are just more expensive?
2) What are the prime frequencies needing diffusion? Obviously, as great a range of frequencies as possible, but what is the frequency range that the ear will most appreciate being diffuse?
3) Why only 1D? Why is reflection towards the ceiling or floor wasting energy?
4) When you say I need several for good effect, how many do you recommend and where in a room would you place them?
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1) Are there consequences for buying diffusers effective to lower frequencies? Or they are just more expensive?
2) What are the prime frequencies needing diffusion? Obviously, as great a range of frequencies as possible, but what is the frequency range that the ear will most appreciate being diffuse?
3) Why only 1D? Why is reflection towards the ceiling or floor wasting energy?
4) When you say I need several for good effect, how many do you recommend and where in a room would you place them?
I'm just going to briefly answer them.
1) If you sit too close to a diffusor you will start to hear discrete reflections. They need distance for the sound to blend correctly back to the listener. But I think you will be ok with RPG diffusors like QRD and Diffractal. You could also lengthen the distance by having a basstrap in the middle and diffusors on the side of it. Not sure if you need to though.
2) Ideally diffusion should start about above the schroeder frequency (where the modes start in the room) and diffuse up to around 5khz. Diffusion above that is debatable, but it does have the advantage of removing flutter-echo and you avoid potential high gain reflections above the diffusion range. So Diffractals are nice if you can afford them.
3) Our ears are on the side and we are more sensitive to sound arriving laterally. We also want to have a boost of energy arriving from behind as long as it's arriving after a certain time. It not only brings liveliness and is preferable, but it's also an important psycoacoustic cue related to accuracy. 1D diffusors will remain more energy since they aren't sending diffusion vertically.
4) A minimum of 5 would be great. Placement depends on room layout, distance to listening position, etc. One could either cover most of the backwall in ear height and some on rear sidewalls or redirect the energy on backwall with a splaying wall/gobo and have every diffusor on rear sidewalls. One could also make a large circle of diffusion if the room is very wide, which is seen in the picture below. RPG are the diffusors.
(http://www.audiocircle.com/image.php?id=62684)
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3) Our ears are on the side and we are more sensitive to sound arriving laterally. We also want to have a boost of energy arriving from behind as long as it's arriving after a certain time. It not only brings liveliness and is preferable, but it's also an important psycoacoustic cue related to accuracy. 1D diffusors will remain more energy since they aren't sending diffusion vertically.
So potentially 1D diffusers on the walls and 2D diffusers on the ceiling above or behind the listener?
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So potentially 1D diffusers on the walls and 2D diffusers on the ceiling above or behind the listener?
No need to use diffusors on the ceiling at all unless it's a sloping ceiling sending specular reflections back to the listener.
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So the recommendation is absorption in front of the listener and diffusion behind?
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So the recommendation is absorption in front of the listener and diffusion behind?
Yes, but very generally said. More spesific would be to say that one treats early reflections with either absorption or redirection and later arriving reflections from behind with diffusion if the distance permits it. One needs to take note that absorption should only be used at those spots that create early reflections in sweetspot. We don't want to use absorption (and especially not thin panels) unecessarily which can easily leave the room dead and dry. The goal is to create an RFZ (reflection free zone) and that can also be done by redirecting the reflections to the rear of the room where they will eventually be diffused. In most cases for instances, provided the rear of the room is properly treated, there's seldom a need to absorp high frequencied behind the speakers. Most speakers don't backfire high frequencies. Bass absorption is crucial though behind them. To find out exactly what do to, measuring and utilizing ETC is the key.
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If I use the Cardas method of positioning, my listening seat will be six feet away from the back wall. Using your formula, one third of 72 inches is 24 inches, and a 24 inch wave is 565 Hz. In this case, I should build or buy a diffuser effective, if possible, down to 565 Hz?
Cardas positioning won't help you anything, he makes great cables, that's about it.
Wing diffusor goes down to 200Hz.
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Hi Bjorn,
Is the OP setting up a mixing desk / studio or a 2 channel stereo listening room?
If the later I'd generally be suggesting diffusion on the front wall (with traps in corners) and absorption directly behind the listener. Personally, I've had good results using diffusion at the 1st side wall reflection points as well - but that may be a matter of personal taste.
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I've never tried it, I was just looking for some placement recommendations. Have you tried any of his placement or room treatment methods?
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Hi Bjorn,
Is the OP setting up a mixing desk / studio or a 2 channel stereo listening room?
If the later I'd generally be suggesting diffusion on the front wall (with traps in corners) and absorption directly behind the listener. Personally, I've had good results using diffusion at the 1st side wall reflection points as well - but that may be a matter of personal taste.
You can use diffusion on sidewalls if you prefer, but it will not be accurate. Areas like tonality, localization, clarity and intelligilibilty will suffer compared to attenuating reflections with absorption or redirection. Depends if you want your room to color or if you want to hear the recording/mix alone. Diffusion in the rear of the room is vital though. When one has done this properly, without overdampening, and have lateral diffuse energy, I would be surprised if many still want to have diffusors on sidewalls.
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You can use diffusion on sidewalls if you prefer, but it will not be accurate. Areas like tonality, localization, clarity and intelligilibilty will suffer compared to attenuating reflections with absorption or redirection. Depends if you want your room to color or if you want to hear the recording/mix alone. Diffusion in the rear of the room is vital though. When one has done this properly, without overdampening, and have lateral diffuse energy, I would be surprised if many still want to have diffusors on sidewalls.
Hi
What about listening volume ? Does the volume you listen to music effect a treatment strategy? I do lots of late nite listening. Diffusing maybe more appropriate here on sidewalls?
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Hi
What about listening volume ? Does the volume you listen to music effect a treatment strategy? I do lots of late nite listening. Diffusing maybe more appropriate here on sidewalls?
Can't see that makes any difference to what I've already said. If anything, it's probably even more important to treat to enhance clarity and intelligibility when one is listening with low levels.
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Can't see that makes any difference to what I've already said. If anything, it's probably even more important to treat to enhance clarity and intelligibility when one is listening with low levels.
Ok thanks !
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You can use diffusion on sidewalls if you prefer, but it will not be accurate. Areas like tonality, localization, clarity and intelligilibilty will suffer compared to attenuating reflections with absorption or redirection. Depends if you want your room to color or if you want to hear the recording/mix alone. Diffusion in the rear of the room is vital though. When one has done this properly, without overdampening, and have lateral diffuse energy, I would be surprised if many still want to have diffusors on sidewalls.
Do you go by the name bwo from gearslutz. :green:
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You can use diffusion on sidewalls if you prefer, but it will not be accurate. Areas like tonality, localization, clarity and intelligilibilty will suffer compared to attenuating reflections with absorption or redirection. Depends if you want your room to color or if you want to hear the recording/mix alone. Diffusion in the rear of the room is vital though. When one has done this properly, without overdampening, and have lateral diffuse energy, I would be surprised if many still want to have diffusors on sidewalls.
Respectively I have to disagree. I AB'd absorption vs. diffusion on sidewall (listening and measurements) and much preferred the later. I found that resolution, localisation and intelligibility all improved with diffusion though there was some cost on imaging.
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Respectively I have to disagree. I AB'd absorption vs. diffusion on sidewall (listening and measurements) and much preferred the later. I found that resolution, localisation and intelligibility all improved with diffusion though there was some cost on imaging.
Isn't localization the same as imaging?
Could you describe the cost on imaging?
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No. Localisation is placement of instruments in a sound-stage. Image (used here) is the referencing the central image. Click on the globe under my name. It will take you to my virtual system where I explain my observations in some detail.
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Respectively I have to disagree. I AB'd absorption vs. diffusion on sidewall (listening and measurements) and much preferred the later. I found that resolution, localisation and intelligibility all improved with diffusion though there was some cost on imaging.
Well, you are debating against years of research when it comes to accuracy. I'm not going to discuss preferences though. Many variables with the setup come into place with what's preferable.
Can you post an ETC of each speaker with both treatments? It would be interesting to see if placement, reflective material or different size has brought you to this conclusion.
I do see that you use quite thin absorption panels. This will alter the frequncy response since they bascially will absorb highs and mid highs. It will function like an EQ. And I see no diffusion in the rear of your room.
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No. Localisation is placement of instruments in a sound-stage. Image (used here) is the referencing the central image. Click on the globe under my name. It will take you to my virtual system where I explain my observations in some detail.
I just read all four pages of your thread in AudioEnz. A fascinating and very informative/helpful read. It was fascinating to study your journey and the huge improvements you gained.
Very few people document and explain their changes any where near as well as you have. I found it way more helpful than reading piles of documents on the theory of room setup.
Thank you very much.
Rod
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Respectively I have to disagree. I AB'd absorption vs. diffusion on sidewall (listening and measurements) and much preferred the later. I found that resolution, localisation and intelligibility all improved with diffusion though there was some cost on imaging.
Same here. But if my room was wider it may be a different story. At 13' 8" wide diffusion on the side walls really makes my room feel bigger and I have no difficulty distinguishing musicians in the stage. I have plenty of bass trapping in the room as well.
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Hi Bjorn,
If the later I'd generally be suggesting diffusion on the front wall (with traps in corners) and absorption directly behind the listener. Personally, I've had good results using diffusion at the 1st side wall reflection points as well - but that may be a matter of personal taste.
In "Sound Reproduction," Toole suggests the use of wideband diffusers as a possible alternative to broadband absorption at the first sidewall reflection points, which may be optional in certain situations (wide dispersion speakers, listener preference, etc). In one chapter, he also mentions the use of diffusion OR absorption in the center of the rear wall (he goes into this a little further one pages 22-23 at http://www.wghwoodworking.com/audio/LoudspeakersandRoomsPt2.pdf)
Diffusers only direct a fraction of the original energy in any one particular direction (like directly towards the listener), and they MAY potentially preserve the spectral content of the off-axis response better than absorption, which is not uniform at all frequencies or angles of reflection (especially when covered with so-called acoustically transparent cloth, particularly at increasing angles). However, some distance from the diffuser may be required to avoid phase anomalies at the listening position.
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Yes, but very generally said. More spesific would be to say that one treats early reflections with either absorption or redirection and later arriving reflections from behind with diffusion if the distance permits it. One needs to take note that absorption should only be used at those spots that create early reflections in sweetspot. We don't want to use absorption (and especially not thin panels) unecessarily which can easily leave the room dead and dry. The goal is to create an RFZ (reflection free zone) and that can also be done by redirecting the reflections to the rear of the room where they will eventually be diffused. In most cases for instances, provided the rear of the room is properly treated, there's seldom a need to absorp high frequencied behind the speakers. Most speakers don't backfire high frequencies. Bass absorption is crucial though behind them. To find out exactly what do to, measuring and utilizing ETC is the key.
What if the wall behind the listening position is dozens of feet away and isn't a problem as far as reflected sound goes? For instance, my room is odd in that it is only 12 feet wide, but it's 45 feet long, and then "L's" into another section at the very back (behind the LP) of the room; it's a basement. Anyway, would it be best to adsorb the lateral first reflections or diffuse them in a room that narrow? I plan to to widen it at some point, but I have to leave it as is for now.
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What if the wall behind the listening position is dozens of feet away and isn't a problem as far as reflected sound goes? For instance, my room is odd in that it is only 12 feet wide, but it's 45 feet long, and then "L's" into another section at the very back (behind the LP) of the room; it's a basement. Anyway, would it be best to adsorb the lateral first reflections or diffuse them in a room that narrow? I plan to to widen it at some point, but I have to leave it as is for now.
First of all it depends on your goal. If you want an accurate listening environment as possible, one wouldn't use diffusion to treat early reflections. I'm well aware of Toole's researches, but they are not about accuracy alone and they really raise more questions then answers any. That's another discussion.
When it comes to your rear walls, it can still cause high gain reflections even with a room with your length. 45 feet isn't really that big when it comes to acoustics. But I can't quite picture how you room looks, so difficult to say anything for sure. Measurements would give the answer whether you have late arriving detrimental reflections or not. If you don't have any and they just die out, you avoid certain problems but you may end up with a pretty dead and dry sound. A reflective backwave from diffusors is beneficial and brings a feeling of envelopment and liveliness that you will lack. Something you could consider is setting up angled wall dividers that will redirect the energy to rear sidewalls where you have diffusors but will still pass the bass through.
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A lot of this discussion is very helpful. I was about to ask a number of questions, but someone else always sneaks them in first, and I get them answered without ever typing a message! 8)
This thread has given me a good idea how I want to treat my room. And this late discussion of absorption vs diffusion on first reflection points, especially in a narrow room, is very good to know. When I can represent my plan with images and details, I'll be sure to post it in the Acoustics Circle to get some advice.
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First of all it depends on your goal. If you want an accurate listening environment as possible, one wouldn't use diffusion to treat early reflections. I'm well aware of Toole's researches, but they are not about accuracy alone and they really raise more questions then answers any. That's another discussion.
When it comes to your rear walls, it can still cause high gain reflections even with a room with your length. 45 feet isn't really that big when it comes to acoustics. But I can't quite picture how you room looks, so difficult to say anything for sure. Measurements would give the answer whether you have late arriving detrimental reflections or not. If you don't have any and they just die out, you avoid certain problems but you may end up with a pretty dead and dry sound. A reflective backwave from diffusors is beneficial and brings a feeling of envelopment and liveliness that you will lack. Something you could consider is setting up angled wall dividers that will redirect the energy to rear sidewalls where you have diffusors but will still pass the bass through.
I attached a (crappy) picture. The DVD rack has since been moved, but other than that the layout is the same. Obviously I am limited in what I can do, but the speakers fire down the long dimension and are about 7.5 feet apart (flanked by dual subs) and just over 2 feet from the side walls; they are 4 feet from the wall behind them. The listening position is 10.5 feet from the speakers. As you can see I have a first reflection absorption panel at the lateral walls, and a pair of bass traps in the corners. The room isn't dedicated and extends well beyond the couch (passed where I was standing when I took the picture), which then becomes the children's play area (lots of toy boxes, toys and various kiddy stuff everywhere). The room then L's around and open to another 12x15 section (complete opposite end of the TV and speaker system). Obviously it's not an ideal setup, and my plan is to expand the right wall another 5 feet (the laundry room is way too big), and perhaps use wall dividers like you mentioned behind the listening position.
(http://i401.photobucket.com/albums/pp94/iviustang50h/IMG_20120505_015618.jpg?t=1337704071)
Anyway, do you have an suggestions? And yes, I want an accurate listening environment (as much as I can get with this crappy room). My apologies to the OP - don't mean to hijack the thread. I didn't want to start another one, though, since I am pondering adding diffusion myself. Thanks for letting me post in your thread.
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(http://i401.photobucket.com/albums/pp94/iviustang50h/IMG_20120505_015618.jpg?t=1337704071)
What's that by the ceiling above the TV?
Did you make the traps or buy them?
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I attached a (crappy) picture. The DVD rack has since been moved, but other than that the layout is the same. Obviously I am limited in what I can do, but the speakers fire down the long dimension and are about 7.5 feet apart (flanked by dual subs) and just over 2 feet from the side walls; they are 4 feet from the wall behind them. The listening position is 10.5 feet from the speakers. As you can see I have a first reflection absorption panel at the lateral walls, and a pair of bass traps in the corners. The room isn't dedicated and extends well beyond the couch (passed where I was standing when I took the picture), which then becomes the children's play area (lots of toy boxes, toys and various kiddy stuff everywhere). The room then L's around and open to another 12x15 section (complete opposite end of the TV and speaker system). Obviously it's not an ideal setup, and my plan is to expand the right wall another 5 feet (the laundry room is way too big), and perhaps use wall dividers like you mentioned behind the listening position.
Anyway, do you have an suggestions? And yes, I want an accurate listening environment (as much as I can get with this crappy room). My apologies to the OP - don't mean to hijack the thread. I didn't want to start another one, though, since I am pondering adding diffusion myself. Thanks for letting me post in your thread.
Looks like a cosy place to enjoy music and movies.
L-shaped room can be tricky. Very often the bass response is different with the speakers. Many struggle with a lack of bass too, but that can vary with placement and what type of wall that divides the room.
Something I would consider in a room that's somewhat narrow is getting speaker with controlled dispersion. For example a good waveguide speaker. These will give less reflections from sidewalls and you don't need to dampen them as much and one can therefore avoid the headphone feeling which easily comes with much absorption on sidewalls. Here's some examples of that type of speaker:
http://gedlee.com/Loudspeakers.htm
http://www.jblpro.com/products/recording&broadcast/lsr6300/JBL.LSR6332.pdf
If this is the setup you will work on, you should dampen part of the ceiling between you and the speakers, dampen the opposite mirror image to each speaker on sidewalls, and use more and bigger basstrapping behind the speakers and in the corner. Unless your speakers are backfiring much of mids and highs, the traps on the frontwall should be made reflective. This can be done by using some layers of plastic between the porous material and acoustic fabric.
The panels on ceiling and sidewalls should not be smaller then a minimum of 4" thickness. Adding an airgap behind would be good. In a narrow room however, you may not want them too thick to remain some spaciousness. Something you can try out. 4" isn't too much of compromise and using panels with that thickness or thicker makes one avoid changing the spectral content. One can build these oneself easily, but if one rather wants to buy I would recommend buying from Acousticmac since they don't use a reflectice membrane on their panels/basstraps. Yes, what they call basstraps are what we should use for early reflections. Basstraps made of porous material really need to be bigger to have a decent effect.
Hopefully you don't have the whole room carpented. Carpet is ok on the floor between the speakers and listening position, but I wouldn't use it other places since it basically just sucks up the highs and too much of that can leave the sound muddy.
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That's a window near the ceiling and a little curtain covering it. :) The bass traps were purchased; my wife surprised me again for my birthday. She's a smart lady and obviously listens when I talk audio with her, though I wish she bought them from Gik (they are from ATS).
Well, the speakers aren't going anywhere, but they have very good off-axis/polar response. The bass response is good, and I have attached an in-room averaging across the three couch locations.
The L in the room is on the opposite end and doesn't' seem to pose a problem regarding bass. I think adding the second sub helped a lot with that (it's hard to see, but that is what the lamp is sitting on. They are DIY 15" sealed TC Sounds TC2000's). I already have a 4" thick first reflection panel at each lateral reflection (used the mirror trick). The speakers do not backfire, but I can certainly add bass traps behind them. Thanks for the info guys; you kind of confirmed what I was thinking, but I wasn't sure if I should add diffusion or not, hence my question.
(http://i401.photobucket.com/albums/pp94/iviustang50h/bass.jpg)
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So what does the response graph look like above 100Hz? Below that, I wouldn't touch a thing - +-3dB is essentially perfect. Although, given what I do see above 100, it would appear that you are running the subs a little hot. Assuming the graph shows all speakers being driven of course.
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So what does the response graph look like above 100Hz? Below that, I wouldn't touch a thing - +-3dB is essentially perfect. Although, given what I do see above 100, it would appear that you are running the subs a little hot. Assuming the graph shows all speakers being driven of course.
Yes, I am running a little hot; I just like it better that way. :)
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That might be tough to get rid of. 540Hz has a wavelength of 2 feet. Typically you'd move the listening chair or shift the speakers, but that may screw up your <100Hz performance. Have you tried a blanket over the tv?
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ETC of each speaker and waterfall for each speaker below 500 Hz is much more useful looking at.
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That might be tough to get rid of. 540Hz has a wavelength of 2 feet. Typically you'd move the listening chair or shift the speakers, but that may screw up your <100Hz performance. Have you tried a blanket over the tv?
I have not - will try that now, then take more measurements. How do you do ETC with REW?
Edit: adding the blanket didn't change anything measurements wise, but I will perform listening tests later.
I have added the impulse and waterfall plots; there's some obvious ringing in the nether regions. :) I also added a current L & R in-room averaged response.
Will update later with the proper plots.
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How do you do ETC with REW?
Under Impulse, choose Envelope (ETC) at the right bottom and remove all the others. Zoom in on the first 50-70ms. What comes after that is of no interest, since the reflections will been attenuated a great deal.
Your waterfall shows that you have some troublesome resonances and a bit of a long decay.You might want to change the settings to 500 ms for both window and time.
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Under Impulse, choose Envelope (ETC) at the right bottom and remove all the others. Zoom in on the first 50-70ms. What comes after that is of no interest, since the reflections will been attenuated a great deal.
Your waterfall shows that you have some troublesome resonances and a bit of a long decay.You might want to change the settings to 500 ms for both window and time.
I'll post those this evening. Thanks.
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Here's the ETC measurements; any help is most appreciated. Other than widening the room and adding a false wall behind the LP, should I treat anything else (diffusion, more bass traps, absorption)?
(http://i401.photobucket.com/albums/pp94/iviustang50h/left.jpg?t=1337897842)
(http://i401.photobucket.com/albums/pp94/iviustang50h/right.jpg?t=1337897867)
That might be tough to get rid of. 540Hz has a wavelength of 2 feet. Typically you'd move the listening chair or shift the speakers, but that may screw up your <100Hz performance. Have you tried a blanket over the tv?
That peak at 540 Hz and 3.5KHz definitely shrinks if I move the mic to the left or right seat, as opposed to the center seat. It's prominent in both the L and R speaker measurements, though, so it must be room interaction, eh?
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I just read all four pages of your thread in AudioEnz. A fascinating and very informative/helpful read. It was fascinating to study your journey and the huge improvements you gained.
Very few people document and explain their changes any where near as well as you have. I found it way more helpful than reading piles of documents on the theory of room setup.
Thank you very much.
Rod
Thanks for the kind words Rod. Journey is indeed the right word and that journey continues. The improvements have indeed been huge, far bigger in fact than any equipment upgrade has ever delivered. Somewhat foolishly the room was the last thing I worked on and it should have been the first.
I am presently experimenting with different options for rear wall treatments; listening and measuring results with different treatments including absorption, polyfusors, 1D & 2D diffusers.
Some audiophiles justify their choice of treatments by reading piles of theory and following others. While I understand this I also think that experimenting in your own room, with your own measurements and own ears is the way forward if the goal is maximum enjoyment of the music rather than +/- 3dB 20Hz-20KHz.
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Here's the ETC measurements; any help is most appreciated. Other than widening the room and adding a false wall behind the LP, should I treat anything else (diffusion, more bass traps, absorption)?
You need to let the window only show the first 50-70 ms. You zoomed in, but you also moved the window to the right. We need see more details to say anything. Let 0 start at the far left.
Pictures of the rear of the room would also be nice.
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That peak at 540 Hz and 3.5KHz definitely shrinks if I move the mic to the left or right seat, as opposed to the center seat. It's prominent in both the L and R speaker measurements, though, so it must be room interaction, eh?
More than likely it is a room interaction, you've got a summing going on at that spot. What happens if you move the mic front or back?
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More than likely it is a room interaction, you've got a summing going on at that spot. What happens if you move the mic front or back?
That's what I figured. If I move the mic forward it's still present, though the width of the peak changes a little. I haven't tried moving the mic back, as there's no way I'll be moving the couch further away. Although, maybe I could convince the wife we need a 60-65" plasma then instead. :D
You need to let the window only show the first 50-70 ms. You zoomed in, but you also moved the window to the right. We need see more details to say anything. Let 0 start at the far left.
Pictures of the rear of the room would also be nice.
Jeez...I cannot get it together this week; sorry about using the wrong graph limits. I will re-post them tonight, as the .mdat file is at home on my laptop. I could also just post the entire file if that would be easier.
I appreciate the help fellas!
Something you could consider is setting up angled wall dividers that will redirect the energy to rear sidewalls where you have diffusors but will still pass the bass through.
I forgot to ask about this: do you have any recommendations from a manufacturer that already offers something such as this? I mean, I can research wall dividers all day long, but does one specific brand or model stick out among the others for this type of use?
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Something I would consider in a room that's somewhat narrow is getting speaker with controlled dispersion. For example a good waveguide speaker. These will give less reflections from sidewalls and you don't need to dampen them as much and one can therefore avoid the headphone feeling which easily comes with much absorption on sidewalls. Here's some examples of that type of speaker:
http://gedlee.com/Loudspeakers.htm
http://www.jblpro.com/products/recording&broadcast/lsr6300/JBL.LSR6332.pdf
The JBL LSR6332 are actually wide dispersion but great linear on- and off-axis response. A better example of controlled dispersion would be the JBL Project Array series, which have a higher directivity index for most of the frequency spectrum.
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The JBL LSR6332 are actually wide dispersion but great linear on- and off-axis response. A better example of controlled dispersion would be the JBL Project Array series, which have a higher directivity index for most of the frequency spectrum.
They are a fantastic speaker (objectively, as I've never heard them). I believe they are Harman's best measuring speaker, period. The fact that they use those instead of the Revel Salon2's is telling IMO. Or maybe it's because they play the nicest in a variety of rooms due to their superior polar and sound power response. My speakers have a very good polar response, but not that good; I don't think many speakers measure that well, actually.
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They are a fantastic speaker (objectively, as I've never heard them). I believe they are Harman's best measuring speaker, period. The fact that they use those instead of the Revel Salon2's is telling IMO. Or maybe it's because they play the nicest in a variety of rooms due to their superior polar and sound power response. My speakers have a very good polar response, but not that good; I don't think many speakers measure that well, actually.
I had wondered about whether part of the reason for the JBL Pro speakers was easy duplication of the reference rooms in various countries, sort of the way some studio monitors seem to be chosen for easy availability anywhere?
I never directly compared the LSR6332 graphs with the Salon2 and Array 1400 graphs on page 399 of Toole's book (they're not named but pretty clear). Not at home, so don't have book handy, but the accompanying text was part of why I was happy to get the 1400s...
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Post 47 has been updated with ETC measurements within the specified window.
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Post 47 has been updated with ETC measurements within the specified window.
Good. 0 represents the direct sound. Of course, it doesn't arrive at 0 ms but that's how REW shows it. What comes after 0 are reflections of surfaces in the room. What we want is an ISD-gap. An ISD-gap is a gap in time where the reflections are attenuated enough so we can hear the recorded signal undisturbed. For this to happen the reflections need to be down -20 dB at minimum. -30 dB would be better, but can be difficult to attain with many speakers in small rooms. After the ISD-gap there should be a strong termination where the energy is arriving from diffusors. The length of the ISD-gap is determined by the space of the room, but ideally we want it to be a bit longer then the time the sound travels in a recording room. 20-25 ms is something you could aim for in your room.
So what you need to do is to find those spots that create specular reflections and treat them and measure again. Always start with the earliest arriving ones. You can either use an mirror or the string method. Then you place an absorbent at that spot, measure and see if it attunuates. You continue with this till you have all reflections up to a certain time below -20/-30 dB.
Here's an example of what you want. Tha first picture is before treatment. The second shows and ISD-gap, or a RFZ as they call it here, and it follows with diffuse energy.
(http://www.audiocircle.com/image.php?id=63010)
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Are the absorbers at the first reflection point? They appear to be forward of where I would expect them to be. They are also high and not in line with your ears and the speaker cones. The left side is going to hit the couch which is fine. Lay that left one horizontally along the top of the couch and lower that right one down 2 feet and see what you get.
Based on that ETC plot you have zero delay and lots of mush gong on at once.
I attached a (crappy) picture. The DVD rack has since been moved, but other than that the layout is the same. Obviously I am limited in what I can do, but the speakers fire down the long dimension and are about 7.5 feet apart (flanked by dual subs) and just over 2 feet from the side walls; they are 4 feet from the wall behind them. The listening position is 10.5 feet from the speakers. As you can see I have a first reflection absorption panel at the lateral walls, and a pair of bass traps in the corners. The room isn't dedicated and extends well beyond the couch (passed where I was standing when I took the picture), which then becomes the children's play area (lots of toy boxes, toys and various kiddy stuff everywhere). The room then L's around and open to another 12x15 section (complete opposite end of the TV and speaker system). Obviously it's not an ideal setup, and my plan is to expand the right wall another 5 feet (the laundry room is way too big), and perhaps use wall dividers like you mentioned behind the listening position.
(http://i401.photobucket.com/albums/pp94/iviustang50h/IMG_20120505_015618.jpg?t=1337704071)
Anyway, do you have an suggestions? And yes, I want an accurate listening environment (as much as I can get with this crappy room). My apologies to the OP - don't mean to hijack the thread. I didn't want to start another one, though, since I am pondering adding diffusion myself. Thanks for letting me post in your thread.
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The couch will quite certaintly reflect some. A thick woolen blanket can be placed upon it and then look at what the measurement shows afterwards. The most troublesome area right now, however, would be the untreated ceiling.
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double post
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Are the absorbers at the first reflection point? They appear to be forward of where I would expect them to be. They are also high and not in line with your ears and the speaker cones. The left side is going to hit the couch which is fine. Lay that left one horizontally along the top of the couch and lower that right one down 2 feet and see what you get.
Based on that ETC plot you have zero delay and lots of mush gong on at once.
What do you mean by "mush?"
The first reflection panels are in the correct spot, yes, which is a little forward of the half way point. The are up high because of the love seat, and I wanted to mirror image them. Should I turn them both on their side and run them the long way at tweeter height?
Edit: saw the post explaining ETC - cool, thanks.
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I just read all four pages of your thread in AudioEnz. A fascinating and very informative/helpful read. It was fascinating to study your journey and the huge improvements you gained.
Very few people document and explain their changes any where near as well as you have. I found it way more helpful than reading piles of documents on the theory of room setup.
Thank you very much.
Rod
Hi Rod,
Further updates have now been posted. Been "playing" comparing absorption and diffusion on the rear wall with interesting results.
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Hi Rod,
Further updates have now been posted. Been "playing" comparing absorption and diffusion on the rear wall with interesting results.
Hi Kiwi,
Thanks for the updates. Just read your recent postings at audioenz. Glad to hear that you are still making improvements.
I'm quite impressed with your whole approach. You are not at all hung up on others theories, but are willing to experiment to find what truly works best for YOU. Commendable!
And you are continuing to document your changes in a very clear and concise manner that can be understood by most people.
Thanks again for sharing all your efforts and successes!
Cheers,
Rod
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Not to put anyone down, but one might want to take what is written in that thread about LEDE with a grain of salt. I just skimmed through some of it and there's a lot of misunderstanding.