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Post by cyclecamper on Dec 5, 2016 19:31:52 GMT
Thank you for setting me straight on the diffusors. Of course horizontal makes more sense, unlike absorption I want to hear the diffused sound, as long as I'm far enough back! DOH!
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Post by cyclecamper on Dec 5, 2016 19:38:57 GMT
It's not clear to me what you mean by hanging diffusers. Do you mean hanging out in the air? You ask good questions about sound arrival direction. I know that sound coming from the sides still gets scattered, but I'm not sure about sound from above and below. Of course, sound in most rooms doesn't emanate from the floor or ceiling! Google may have something to offer. If you find a believable explanation please post it here. Yes, just an absorption panel hung from the ceiling by cables attached to just one edge of the frame. Not like a horizontal cloud. More like a "solid" curtain hanging from the ceiling, parallel to the problematic parallel sides walls. Instead of on the wall or inches from it, I have the space to hang thick panels hanging down in the middle of the room (1/2 way from the right-side wall), and 1/4 way from the right-side wall, and 1/8 of the way. I just am curious whether there are known relative sizes that might be good, like should the one in the middle be larger....
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Post by Hexspa on Dec 5, 2016 20:59:40 GMT
The bottom line is that a panel anywhere will work - to a degree.
Placement is very important and you won't know how important each location is until you treat it - I don't think they're all equal.
The reason people place panels against walls is to take advantage of the reflection the surface bounces back so you, in effect, get to use your absorber twice.
If you hang it in mid air you won't get that.
Larger is always better.
If you're going to hang panels all over you should measure first then try to position the absorption as close to 1/4 wavelength of your worst frequency - again, location.
And back to larger, you should just make a big pink fluffy bale or soffit and put it 1/4 wavelength.
And definitely do measurements so we can see your results.
Thanks,
-m
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Post by akaspeedy on Dec 10, 2016 0:53:53 GMT
Good points...just did my room measurements and they are way off...
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Post by akaspeedy on Dec 10, 2016 0:54:18 GMT
Left and right speaker response
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Post by Hexspa on Dec 10, 2016 2:14:33 GMT
Left and right speaker response Surely wrong thred
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Post by akaspeedy on Dec 10, 2016 2:38:42 GMT
Aye...it most surely is!! D'oh!!
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Post by cyclecamper on Dec 19, 2016 21:08:56 GMT
Still interesting...
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Post by cyclecamper on Dec 19, 2016 21:26:56 GMT
HEXSPA: I'm trying to confirm a shorthand rule-of-thumb, just simplifying the larger equation for identical results. Instead of measuring the room and converting that into frequencies of modes and then converting that back into distances for locations 1/4 wavelength etc. etc. we should be able to look at one dimension of a room and know the locations where the velocity antonodes nearest one wall would be for each mode, as a simple fraction of the distance between parallel walls:
(A) midway, which also addresses every second higher mode (B) 1/4 (C) 1/6, but already addressed by (A) (D) 1/8 (E) 1/10, but already addressed by (A)
So I might be able to place 3 hanging absorbers (A) (B) (D) and take care of the worst problems bass modes between those parallel walls. I'm hoping this kind of thinking minimizes cost.
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Post by cyclecamper on Dec 19, 2016 21:36:07 GMT
I have insufficient real experience with diffusors. By that, I mean that I don't have enough experience listening to them. I'm having trouble visualizing what it would look like in one of those high-school wave tanks using water, and how that relates to what it sounds like at a distance.
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Post by Hexspa on Dec 19, 2016 22:17:36 GMT
HEXSPA: I'm trying to confirm a shorthand rule-of-thumb, just simplifying the larger equation for identical results. Instead of measuring the room and converting that into frequencies of modes and then converting that back into distances for locations 1/4 wavelength etc. etc. we should be able to look at one dimension of a room and know the locations where the velocity antonodes nearest one wall would be for each mode, as a simple fraction of the distance between parallel walls: (A) midway, which also addresses every second higher mode (B) 1/4 (C) 1/6, but already addressed by (A) (D) 1/8 (E) 1/10, but already addressed by (A) So I might be able to place 3 hanging absorbers (A) (B) (D) and take care of the worst problems bass modes between those parallel walls. I'm hoping this kind of thinking minimizes cost. I think what you're asking is whether you can predicts a room's modes by its dimensions and the answer is yes. amroc.andymel.eu/?l=20&w=20&h=20&ft=true&r60=0.6 for instance Diffusors are just going to break up the sound as opposed to a flat wave reflection. Maybe you could think of it like hitting an incoming water balloon with a huge cricket bat and it explodes as opposed to throwing it into one of those practice pitching nets where it'll just bounce back wholesale; the farther you are, the more likely you'll get hit by drops instead of the main body of water. -m
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Post by cyclecamper on Dec 20, 2016 23:25:46 GMT
Keep in mind I'm new to all this, just thinking out loud while I learn to visualize what's going on. Yes, I love that amroc calculator / simulator. But it leaves you with frequencies, not giving you distances from a surface where the velocity antinodes are maximum for each mode (of that pair of parallel surfaces). And if you visualize the standing waves, the velocity maximums always work out to be the same fractions of the distance between parallel surfaces, of course. So there's some practicality to learning to visualizing where to expect those "maximum" locations to be, which is where absorption should be most effective. On the wall is about the least effective place; right at the wall is the location where the sound has no velocity and no absorption can occur. Of course, my rule of thumb is only about locations, and does not address the absorber thickness required in order to be effective; that is frequency related but once again more useful to think of in units of distance instead of frequency. I assume that with practice Ethan instantly visualizes the wavelength of a frequency. To a listener, carpenter or architect getting his feet wet that is probably not the case. So why do we place bass absorption against the walls and in the corners, when the most effective location is in the middle of the room or at least well into the space? For one thing, only a very tall room can be very useful with thick absorption in the very center of its space. For another, that central thick absorber might affect every second mode, but not address the others. It seems to me that a typical fully-stuffed triangular-section corner absorber isn't very good use of expensive absorbent stuffing when it comes to bass modes; it's an unbalanced treble absorber enlarged to handle mids. For my money (on materials) I'm much more inclined to place an open-back absorber across the corner or creating a hollow space; I would expect the extra stuffing required to fully fill the corner behind the panel to address more complete absorption of higher frequencies and have little effect on the bass. So have I got this all backwards? Here's from Acoustic Frontiers www.acousticfrontiers.com/201129the-secrets-of-bass-trap-placement-html/"The most effective place to add bass traps is in the corners of the room since all room modes have a pressure high or node in the corner." Wait a minute, isn't the pressure high a pressure antinode? Who cares about the pressure antinode at the wall when the absorber works on velocity, not pressure. Now, in their defense, they go on to talk about velocity bass traps that use membranes and void spaces... But I think this is typical of where people get the wrong impression and start to think that the best place for a bass absorber is jammed tight into the corner against 3 walls, where it might be effective for higher frequencies but not for bass. In my first house I glued expensive large blocks of Auralex into the corners and got little benefit from them, partly due to the material and partly due to the location; would more of them a few feet from the corner have worked better? Sometimes I think the only reason Tube Traps work is because they're out in space, near the corner not tight in the corner against the walls. I see Sonex hanging absorptive melamine cylinders in free space for treating commercial spaces, and it seems to make some sense to me. Maybe we should be hanging big absorptive balls in free space instead of flat panels on the walls. I guess I need to start modeling perforated-panel absorbers and velocity-based membranes. I often hear an opinion that the total quantity of absorptive material in a room is important for bass, but against the wall it has little benefit and a sofa with cloth upholstery in the sweet spot and two overstuffed chairs behind might do more good than many enormous corner traps that cost hundreds of dollars. My mother was a painter and I have many very large paintings on canvas stretchers, and I am very curious about how I might add damping and absorption behind, to create broadband limp mass membrane diaphragm absorbers of some kind.
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Post by Hexspa on Dec 21, 2016 7:41:03 GMT
cyclecamper, my friend. I am drinking. Allow me to respectfully say the following:
Get with the program. Do the basics. Analyze and modify later.
Yes, you'll get maximal absorption at 1/4 wavelength; but you'll get some at other fractions.
I've never seen absorbers hanging mid-room but you could be the first.
However, if you want a room that sounds great today, just do the basics first and, like I said -
modify, analyze and interpret later.
Anyone who's done the groundwork has a standard-meeting and useable room without all this endless jibber jabber speculation; just look at high-end control rooms, for example - or anechoic chambers for that matter!
-m
PS - If you're looking to make a thesis on theoretical home acoustics then I'm not your guy. I'm the guy that says, "Do ABC and get XYZ." I know what I do works. It comes from Ethan and I'm making records. That is all.
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Post by Hexspa on Dec 21, 2016 7:52:20 GMT
Look. Here's my rant: There's an inverse relationship between how many are words in someone's post and how much they understand, I've noted. You ramble; Ethan says five or six words and changes our whole game. I'm not against rambling, per se, but there's a very sound reason why I'm so cut-and-dry: I spend six solid months trying to grasp this carp and I don't want anyone else wasting that much time to get a decent room. It's like plugins for DAWs - you can do a fine job with what comes stock or you could debate endlessly about impulse responses vs algorithmic programs, which DAW to use and how that all compares with analog until the sun burns out - or you could just make a record using whatever gain, EQ, compression, saturation and time-based FX you have at hand. So it's my compassion for your apparent attraction to the insane rabbit hole that I staunchly advise toward simplicity. It's not cuz I'm 1337. Get 4" absorbers, gap 'em near a wall, measure, post and move on; that' it! I cherish this forum. I'm not trying to get b&d by being a rooster. I simply want people to succeed at home acoustics and waste less time. Ish, I wrote a song about it: youtu.be/ZTHL4wNY6lM-m
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Post by Ethan Winer on Dec 22, 2016 18:27:14 GMT
1) We don't put bass traps in the middle of a room because that's impractical. But porous "velocity" bass traps don't have to be a full quarter-wavelength away from a boundary to be highly effective either.
2) The guy at Acoustic Frontiers is not very knowledgeable, so don't rely on what you read or see in his videos.
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