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In Reply to: RE: Peaks and nulls posted by Jolida on July 03, 2009 at 12:23:24
Well, the treadmill would have had a number of freely moving parts which would have resonated in response to any sound in your room. I'm not surprised removing it had a beneficial effect.
Another source of resonance may be the hinged glass doors in your equipment rack and removing them may help if that's possible. The ceramic tiled floor will certainly be adding some brightness to the room but I would expect that to be broad band rather than creating a peak at a particular frequency.
I can't tell the exact proportions of your rug from the photos but I suspect that it's longer than it's broad and that you have the narrow side facing you. You could try turning the rug 90 degrees so the long side runs across the room and locating the rug with its centre halfway between you and the plane of the speakers. That may or may not help a little but it only takes seconds to try and things like that are always worth the experiment in my view.
David Aiken
And one more thing....
As the flooring of my room is entirely ceramic, will carpeting it till the 1st half make a considerable ( worthwhile) difference???
I do not want to make the whole room wall-to-wall carpeted as it gets rather annoying to maintain....
Klaus' citing of absorption coefficients really begs the question. Ceramic tiles are very reflective at high frequencies, just as glass is. Carpet will absorb high frequencies but is not very absorbent at low frequencies—too thin, often not dense enough, and in direct contact with the floor rather than spaced off it by 3 or 4", for effective bass absorption. Carpeting, or a rug covering the floor reflection points, won't change the sound of things at low to mid frequencies but it certainly can help somewhat with the brightness that the high frequency reflectivity of ceramic tiles can produce and that can be a useful thing in many rooms.
Numbers like absorption coefficients are fine, and useful in a number of ways, but they often don't tell you much about what the effect on the actual sound in the room will be. In this case you don't need to worry about the figures when it comes to your rug. The amount it will absorb won't change because the rug isn't changing in any way, but it's being placed in a slightly different position and that means that it's going to be absorbing in some locations where previously it wasn't and not absorbing in some where it previously was. The reflections from those areas where things are changing don't all reach you at the same point in time so you are actually making a small change in the characteristics of the reflected sound as it decays. It's not going to be a big change and it may not be an audible change. On the other hand, something may be audible and you may prefer the sound with the rug in the new position.
The thing to remember about all acoustic treatment is that it's all about changing something in the reflected sound reaching your ears. The direct sound, the sound travelling in a straight line from the speaker to you, is always unchanged unless you actually put something physically between you and the speaker at ear and speaker driver height. What you put in the room and where you put it is what makes the differences you hear, and placing the same thing in different locations can result in audible differences in sound. The easiest way to prove that is simply to move your corner bass traps to somewhere else in the room, leaving the corners untreated. You'll still have the same amount of treatment in the room but things will sound different. Moving the rug won't make as big a difference as moving the corner bass traps, it may not make an audible difference, but it just might make a small but useful difference.
What counts in the end is always the way things sound to you, not what the numbers say. Measurements can help us to get things sounding better but our aim isn't to get the system measuring well, our aim is to improve our enjoyment of the music we listen to. The measurements are worthless if our enjoyment doesn't improve.
Personally I'd prefer not to have a ceramic tiled floor. My music room is carpeted wall to wall but at least maintenance isn't too onerous since I live alone and tend not to get it dirty or messy. I vacuum clean it weekly while vacuuming the house and that is basically all I need to do. It would be different if I had kids or if my music room got a lot of foot traffic through it.
The open plan area where my TV system is located does have ceramic tiles, and I often find them a bit more of a pain to keep clean since that area gets a lot more foot traffic from me than the music room does. I walk through that open plan area all of the time to get from one part of the house to another. I don't walk through the music room to get anywhere, it's an "end point" in the house so it's easier to keep clean even if carpet can trap dirt better than ceramic tiles in some ways. Since I don't have carpet or a rug in the area with the TV system, I rely on the Audyssey room EQ function in the AV receiver to tame the brightness caused by the reflectivity of the tiles and the sound certainly benefits from the equalisation. While that does a quite adequate job for movie and TV soundtracks, I don't enjoy listening to music on that system as much as I do on my audio system which has no EQ functions. Overall I think balanced absorption does a better job in many ways than EQ.
I think you may find that changing the rug's position as I suggested may help a bit. It may not, and a lot depends on just how much placing the rug in the other orientation affects the absorption of your floor reflection. You're probably getting some absorption of that already and the carpet's absorption characteristics aren't going to change. The only change occurring is where you're placing the carpet and that's a small change so I wouldn't expect a big change but you may get a noticeable change and you may find it preferable. As I said, it's free and quick to try.
It's worth playing around with simple changes like that in my view. They cost you nothing apart from a little time and they can make worthwhile differences, even if they aren't big differences. Still, several small differences from a number of minor changes can add up to a much more noticeable improvement overall than any single change makes and that's not to be sneezed at, especially when the changes are free.
Finally, working with your room and what you've got is always worthwhile in my view. The difference between good and very good results can easily be nothing more, or less, than simply paying attention to the little details. When all it's costing you is a little time, there's no real reason not to try experimenting with the small things and it's often surprising what you can learn in the process. What you learn is always going to be valuable, and it will help you a lot if you ever move house, swap rooms, or even simply change speakers and simply need to start fine tuning again to get the most out of the new speakers.
David Aiken
David,
I am in total agreement with what you said. I've been observing since your first reply to my post, that ur suggestions are very practical. Since i, or for that matter many people do not have much knowledge about physics or psycho-acoustics, practical suggestions sound as golden-words as opposed to theory.
My music room, is not just an Audio-Only room, & i have a small child who spends most of his time there, so i would refrain from full wall-to-wall carpeting. I would try to carpet the floor till my listening chair, coz i guess it would sound considerably better, as opposed to bare ceramic floor. I will try to orient the rug in the other way today & post a feedback. Also i will take-off the glass doors from the table & see if performance differs. I appreciate the time you have taken to resolve my issue.
Different circumstances can't help but steer us in different directions.
I don't think you "need" to carpet your room up to the listening chair but I do think there will be a "compromise" point that you're prepared to live with in order to balance use with sound and I do think that there will be a minimum carpet/rug size which will achieve that for you provided it's placed in the right position. Don't think only in terms of increasing carpet/rug area and do think also on where you place it between the speakers and the chair. Experiment a bit as I suggested. You may have enough area already to give you that compromise if it's placed slightly differently. If not, you may be able to achieve the result you want by placing something else like a felt backing beneath the rug you've got in order to increase its absorption characteristics. You may have enough area if you increase effectiveness and placing felt or a similar backing under the rug isn't going to make things any more difficult to take care of.
Another "freebie" you could try is moving the speakers a little closer together so the carpet, as it currently is located, is in front of the speakers.
Playing with what you've got is always a good starting point before you consider changing what you've got. Spend some time playing with what's in the room right now, moving things around or removing some things rather than changing or adding things. You might get some surprises, both good and bad, but I think you can end up with things sounding better without replacing or adding anything. If you do, those benefits will probably still work in your favour when you do replace or add something so they won't be wasted.
David Aiken
The absorption coefficient of carpet on concrete are
125 Hz - 0.02
250 Hz - 0.06
500 Hz - 0.14
1000 Hz - 0.37
2000 Hz - 0.60
4000 Hz - 0.65
Data from http://www.sengpielaudio.com/calculator-RT60Coeff.htm
Using more carpet will lower reverberation time, but it will have little effect on frequencies below 1000 Hz.
Klaus
I surely will try to rotate the rug & experiment this evening. The glass doors in the equipment table can also be removed. i will try to implement that as well. Now it crosses my mind that when i place my amp & cd player in the rack, it sounds inferior that when its kept on top of the table. But i dint pay attention to this, as it would defeat the purpose of making that rack as a whole. Even thought i have isolated the cd player on air suspension & the amp on rollerberings, they do sound better when kept on top of the table rather than inside.
Thanks for enlightening me. You are right, its easy to experiment though.....
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