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Thread: Placement options – Impacts of location, orientation and treatments

  1. #31
    Super User JonFo's Avatar
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    Quote Originally Posted by Rich View Post
    They were the RPG Hemiffusers. Here is a link:

    http://www.rpginc.com/products/hemiffusor/index.htm

    I actually bought these for placement behind the rear speakers for surround field diffusion, but figured I would test them behind the front speakers just to see the different effects of diffusion vs. flat wall vs. absorption. I was expecting an improvement with diffusion and was surprised to find it as bad or worse than flat wall.

    Probably RPG's abfuser would be better for placement behind the panels, because it provides absorption and diffusion. I think the Real Traps diffusors will probably work great as well for the same reason.

    Rich, yes, 3D diffusion behind the diploes doesn't really work too well. One of the reasons is that it immediately engages floor and ceiling (especially), as it radiates diffused energy in all directions. The additional reflections off the ceiling add additional energy in the <20ms range to the main signal from the panel, thus causing even more comb filtering.

    3D diffusion works well on the wall between the rear speakers (as can be seen in the pics of my system below) Those are RPG Skylines, and they take the energy that has traveled 24’ or so from the fronts and diffuses it so the listener get a greater sense of space and not a strong rear-wall reflection (although those reflections are >20ms, and therefore not perceived as part of the ‘main’ impulse.

    Using 2D diffusers, like the Auralex you see behind those Sequels, work really well for the rear channels. But as noted in other posts above, probably not so good for fronts. I’d agree the RPG Abfusor or the RealTraps diffuser (which is a combo of diffusion grating over an absorber) should work really well.

    The benefit of 2D diffusion is it reduces the intensity of the primary solid surface reflection by re-radiating much of the energy in a horizontal arc. With none of the energy arriving at ceiling or floor, the only thing to worry about is the side-wall reflections and their relative arrival times.

    For instance, I recall recommending for Kruppy that he use an RT Difusor behind his SL3’s coupled with a MiniTrap along the side wall. I guess the questions now is: should the side wall mini trap be an HF variant or the normal one (which is reflective in the highs). That might a 'season to taste' item.
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    Last edited by JonFo; 12-22-2007 at 03:56 AM. Reason: spelling
     
    Jonathan

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    Super User Audioseduction's Avatar
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    Jonathan,

    Thanks for the data you’ve collected. It actually reflects my experience in my den with the Odyssey’s. I appreciate you taking the time applying your knowledge and tools in presenting the information so we all can gain a better understanding of sound reproduction. I must say this forum is the Best with people like your self being part of it. Peace!

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    Quote Originally Posted by DTB300 View Post
    I have bookcases sitting 4ft behind my seating position. Using GIK 244 panels (3 of them) in front of the bookcases really helped my room response and overall sound. Each room is different and each person has different tastes, so trying out absorption and diffusion behind should be done to see which is the best solution.

    I had thought I read that diffusion behind the seated position is only beneficial when seated further away from the rear boundary.
    Jon,

    I am sorry. In my hurry I missed some words in my post. What I really meant was "behind the speakers", not behind the listener. I was wondering what your charts would look like with an absorbtive wall in front since there would be little or no reflection at all from the front wall. Wouldn't that be ideal?
    Last edited by benleeys; 12-11-2007 at 09:15 AM.
    Ben
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    I am still experimenting and tweaking. Added spike cups. I use the flashlight method to get my toe in. Might try raising the rear of the Vantages a tad. I have searched for nice wall absorbtion treatments online, rather expensive. I might end up DIY'in them. I did something similiar behind my dartboard.

    Lee

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    Quote Originally Posted by David Matz View Post
    JonFo, thanks for posting this great information - the charts speak for themselves. Just out of curiosity, why did you settle on Real Traps? Are they significantly better than their competitors - ASC, echobusters, etc.? Also, how many did you order, and where are your placement priorities? Stereophile seems to think highly of their new product, Mondotraps. Are there any objective tests comparing the products from the different companies?

    Also, have you heard anything about golden acoustics? http://www.goldenacoustics.com/index.html

    They are supposed to be a "revolutionary" product that uses gypsum. One guy even made the claim to me that by using their product, the limited sweet spot of the Logans can be greatly increased, and one could have more uniform sound throughout the entire room. A high end store in Chicago just bought $40k of their "deluxe" panels, and it does sound good! (The rest of their system is also very expensive - Vivid driven by Luxman).
    ...

    Just curious what your thoughts are.

    Thanks,
    David
    David, thank for sharing the info on Golden, they have a very intriguing product line. I definitely dig the look of their panels (see pic), as I love fractals.
    The one thing I’d like to see is the independent testing and analysis results of their products. So far, none of that is posted.

    Also, I'm somewhat suspect of claims to be able to ‘diffuse’ low-frequency (below 100hz) as those wavelengths are huge (measured in feet) and in small rooms, are mostly pressure artifacts (which is why one needs diaphragmatic absorbers to deal with them), not waves that can be reflected. But then, my knowledge in this field is entry-level at best.

    I can definitely see how they could be effective at all other frequencies though. And by recommending fairly large surface area covering, they are bound to substantially change the higher-frequency modal reflections.
    The positive about using diffusion products over just throwing absorbers everywhere is that we can manage to preserve spatial imaging, and just as important, the right balance of energy in the room to maintain a uniform frequency response.

    However, the science of deciding where to put the diffusion is tricky, and complicated even further by the dipole nature of our speakers. Most of the research and literature on these topics uses point-source monopoles for the sound generators. And as we see in the graphs I published earlier, diploes can have very different impulse responses depending on placement and wall (the ones behind/side of the speaker) treatments.

    As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) .
    There are two additional HF MiniTraps to go on the wall behind the Monoliths.
    The LENRD traps in the rear corners will be replaced by 4x MondoTraps.

    I’ll be adding two to four more Mondo traps hanging from the ceiling at strategic high-pressure bass modes in the room. But this might get scratched for a room-long custom DIY ceiling / side wall trap Triangular profile, offset form the boundary by a few inches. But calculating how to make an effective diaphragmatic absorber oneself is daunting (yes, even for me )

    Once all the above is in place, I’ll see how that works and go from there if needed with more diffusion and or absorption.

    One of the things I do want is a half-way decent aesthetic balance as well, so side wall absorbers will be DIY with my artiste wife doing the look and feel. Oh, you guys will LOVE the special ML centric touch we’ll give those Just wait and see.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

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    Quote Originally Posted by benleeys View Post
    Jon,

    I am sorry. In my hurry I missed some words in my post. What I really meant was "behind the speakers", not behind the listener. I was wondering what your charts would look like with an absorbtive wall in front since there would be little or no reflection at all from the front wall. Wouldn't that be ideal?
    Ben,

    The comparison in the first few posts go between untreated (bare wall) and treated. The treated surface is an RPG product that is absorbent in the mid and high frequencies.

    So that's what the frequency and impulses will look like. As you can see, it's much improved over a bare wall.

    Again, the toe-in will dramatically affect how much this comes in to play as well. So these two interact.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

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    Quote Originally Posted by JonFo View Post
    The one thing I’d like to see is the independent testing and analysis results of their products. So far, none of that is posted.
    I see their site says "they are coming soon" - but how soon??? Always makes me skeptical when companies do not show their data results for acoustical treatments. Hopefully they will post their data to show the real benefits of their devices.

    Also, I'm somewhat suspect of claims to be able to ‘diffuse’ low-frequency (below 100hz) as those wavelengths are huge (measured in feet) and in small rooms, are mostly pressure artifacts (which is why one needs diaphragmatic absorbers to deal with them), not waves that can be reflected. But then, my knowledge in this field is entry-level at best.
    I would agree with you here on both points of diffusing low frequencies (always read what you stated about the large wave sizes and diffusers not being large enough to deal with them - that is diffuser sizes we are familiar with ) and being a newbie in this room acoustics stuff. But like you have experienced and other should too, treating our rooms is a great benefit.

    I can definitely see how they could be effective at all other frequencies though. And by recommending fairly large surface area covering, they are bound to substantially change the higher-frequency modal reflections. The positive about using diffusion products over just throwing absorbers everywhere is that we can manage to preserve spatial imaging, and just as important, the right balance of energy in the room to maintain a uniform frequency response.
    While I would agree that both products are the usual way to go, but don't you think that each room is different hence there is no real "best way"? Going through some trial and error with both products in ones room, and then listening and/or testing will show the best results. Yes?? No???

    However, the science of deciding where to put the diffusion is tricky, and complicated even further by the dipole nature of our speakers. Most of the research and literature on these topics uses point-source monopoles for the sound generators. And as we see in the graphs I published earlier, diploes can have very different impulse responses depending on placement and wall (the ones behind/side of the speaker) treatments.
    Agree. When talking with people in the know and you spurt out the word Electrostatics, they usually come back and state their experience is very limited with them and their products. Have you considered sharing your charts and graphs with people like Ethan to help him sell his products to other ML people - then sign the contract for your percentage of the profits!!! Seriously...I do think they would be very happy for the information on planar speakers and the results of acoustical treatments with them.

    As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) . There are two additional HF MiniTraps to go on the wall behind the Monoliths. The LENRD traps in the rear corners will be replaced by 4x MondoTraps.
    I suspect you will hear a great improvement in your room when switching over from the stated products to the Real Traps products. The change from the LENRD's to the Mondo's will really help out the low end. I used the GIK to replace some LENRD's and the change was really nice.

    Please make sure to get back with all of us on the changes you hear. Again I suspect that it will be very positive.

    One of the things I do want is a half-way decent aesthetic balance as well, so side wall absorbers will be DIY with my artiste wife doing the look and feel. Oh, you guys will LOVE the special ML centric touch we’ll give those Just wait and see.
    The products from Real Traps and GIK really look nice and do not give our rooms that recording studio look. Considering most of our rooms double as living spaces, this is a real plus.
    .............

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    Quote Originally Posted by JonFo View Post
    As for what I’ve ordered: I’m going for three RealTraps diffusers (which are absorptive as well), two will replace the Auralex diffusers behind the Sequels. The other goes behind the Center (which also has Auralex diffuser+ and HF absorber blanket over it) .
    There are two additional HF MiniTraps to go on the wall behind the Monoliths.
    Jonathan, please do a test for me when you get your products in and start placing them. Please do a comparison between placing just the two HF mini traps behind your monoliths and then place the real traps diffusers in front of the HF mini traps (still behind the monoliths). I am have a theory that this would provide some ambiance by diffusing some of the higher frequencies of the rear wave, while providing even greater absorption of the mid and lower bass frequencies. Or just a comparison between the HF mini trap vs. the diffuser alone behind the monoliths would be great. For these tests, I am primarily interested in two-channel sound and imaging. Depending on your results, I may decide to purchase a couple of those diffusers as well. Thanks so much.
    Rich

    This comment is intended solely for educational purposes and should not be construed as conveying any express or implied warranty of fitness for any other purpose. Said comment constitutes merely the humble opinion of its maker and does not reflect the views of the MLOC or of ML, Ltd. YMMV. Trust your own ears.

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    Jonathan,
    Can you please post the manufacturer and name of the diffusers you used for your measurements in the first couple of posts. The white one looks like an Auralex MetroFusor. The darker/black one I can seem to place, looks like an Auralex product.

    Right now I'm looking for a combo diffuser/absorber but I don't see anything that is more my (insert deep voice) "budgetary style".....specially if this is something that is experimental/trial and error and may not be permanent.
    Been Thinkin bout nothing and doin nothin but thinkin...

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    Quote Originally Posted by JonFo View Post
    Ben,

    The comparison in the first few posts go between untreated (bare wall) and treated. The treated surface is an RPG product that is absorbent in the mid and high frequencies.

    So that's what the frequency and impulses will look like. As you can see, it's much improved over a bare wall.

    Again, the toe-in will dramatically affect how much this comes in to play as well. So these two interact.
    Jon,

    I thought you would say that. Unfortunately, my experience with heavy curtains covering the wall behind my Summits was a sonic disaster. Vocals sounded very much like the singer had a bad cold. Push the curtains aside and the cold disappeared. I wish I have the facility to take measurements like you do to find out the reason why. Obviously heavy curtains was the wrong idea for an absorbent.
    Last edited by benleeys; 12-12-2007 at 08:29 AM.
    Ben
    System # 165 : Summit/Descent i/Stage/Passage

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    Jon,

    I would also like to add my sincere thanks for your thread. It will directly affect my panel choices for when I split off my 2-ch, which I hope will be sometime next year. While there is probably no substitute for serious experimentation, as done by Rich for example, your recommendations will be my command!

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    Quote Originally Posted by benleeys View Post
    I thought you would say that. Unfortunately, my experience with heavy curtains covering the wall behind my Summits was a sonic disaster. Vocals sounded very much like the singer had a bad cold. Push the curtains aside and the cold disappeared. I wish I have the facility to take measurements like you do to find out the reason why. Obviously heavy curtains was the wrong idea for an absorbent.
    Since I am one of the people who use absorption on their front wall, I can concur with your findings. Too much absorption can really kill the sound to the point of sounding muffled - or the singer having a bad cold as in your analogy.

    What I had to do with my space is try different amounts of mid/high absorption along with the corner-ceiling bass trapping (I do not have a very wide front wall). After much trial and error, I found a very happy medium with some absorption, some open bare wall spaces, and the bass traps. But again, in my room, for my setup, and my tastes, this absorption pattern worked the best.
    .............

  13. #43
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    Quote Originally Posted by benleeys View Post
    Unfortunately, my experience with heavy curtains covering the wall behind my Summits was a sonic disaster. Vocals sounded very much like the singer had a bad cold. Push the curtains aside and the cold disappeared. I wish I have the facility to take measurements like you do to find out the reason why. Obviously heavy curtains was the wrong idea for an absorbent.
    My guess is the problem with using heavy curtains was an uneven absorption across the frequency range. In other words, they probably completely absorbed some of the higher frequencies and didn't absorb any of the mid to lower frequencies. Reflection in the midbass can really muddy the soundstage. This is why you want a product that will absorb at an even rate throughout the frequency range (which is what the Real Traps High Frequency Mini Traps do) or you might want a prudent combination of diffusion and absorption behind the panels.

    As Dan says, this is all room, system, and individual taste dependant, so the more experimentation you can do the better. If you can spring for a couple of panels from Real Traps or GIK or something similar, I highly recommend it. Even if you don't like them behind the speakers, I am certain there will be somewhere in the room you can place them where they will improve your sound.
    Rich

    This comment is intended solely for educational purposes and should not be construed as conveying any express or implied warranty of fitness for any other purpose. Said comment constitutes merely the humble opinion of its maker and does not reflect the views of the MLOC or of ML, Ltd. YMMV. Trust your own ears.

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    Quote Originally Posted by DTB300 View Post
    ...
    While I would agree that both products are the usual way to go, but don't you think that each room is different hence there is no real "best way"? Going through some trial and error with both products in ones room, and then listening and/or testing will show the best results. Yes?? No???
    Hi Dan, absolutely agree, there is no one formula that can applied to any room. There are guidelines that are pretty widely applicable, but ultimately, initial calculations, backed up by post-installation measurements and listening are the way to go.
    What I’m hoping to get form my measurements is some of the generalized guidelines for our type of speakers in the types of rooms we typically put them in.

    Now, some of us are lucky and have dedicated spaces, so we can go crazy with the treatments and what not, but even then, there is no real clear guideline for what helps and where should it go.

    Quote Originally Posted by DTB300 View Post
    ...
    Agree. When talking with people in the know and you spurt out the word Electrostatics, they usually come back and state their experience is very limited with them and their products. Have you considered sharing your charts and graphs with people like Ethan to help him sell his products to other ML people - then sign the contract for your percentage of the profits!!! Seriously...I do think they would be very happy for the information on planar speakers and the results of acoustical treatments with them.
    What? Actually make money on my hobby? the horror

    But good idea to engage them in positioning their products for the dipole market place (there are maggies as well).
    Jonathan

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    Quote Originally Posted by Rich View Post
    Jonathan, please do a test for me when you get your products in and start placing them. Please do a comparison between placing just the two HF mini traps behind your monoliths and then place the real traps diffusers in front of the HF mini traps (still behind the monoliths). I am have a theory that this would provide some ambiance by diffusing some of the higher frequencies of the rear wave, while providing even greater absorption of the mid and lower bass frequencies. Or just a comparison between the HF mini trap vs. the diffuser alone behind the monoliths would be great. For these tests, I am primarily interested in two-channel sound and imaging. Depending on your results, I may decide to purchase a couple of those diffusers as well. Thanks so much.
    Hi Rich, sure thing, that's a good series of tests to try.

    The doubling up of the traps and diffusers should increase bass and mid-bass absorption, as the diffuser also includes absorption elements as well.
    Jonathan

    System #45 (Monolith IIIx, Sequell IIb, SL3XC)

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