Post by LC September 20, 2004 (21 of 30)
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Khorn said:
LC, I notice you are using "egg crate" type foam treatment. Both myself and a friend tried these in all different sorts of configurations but in our cases it "deadend" the sound to an unacceptable degree. How is yours set up?
I use 3' x 4' panels on the front wall behind my system and on the rear wall behind my head. The left wall has various shelves and things and the right side is open with a couch.
In a performance area where real acoustic events take place, "brightening" or "deadening" the sound by exposing or covering hard, flat surfaces of different materials is more or less a matter of taste and suitability. It affects the sound of what you hear, but it doesn't - barring the occasional strange echo effect - affect *what you hear*. This is because, somewhat trivially, sound reflections originate from the source of the sound. The reflected sound, whatever it contributes to the *character* of what you hear, is all consistent with the information your brain is getting from the sound propagating directly from the event through the air to your ears. But in stereo playback, the source is of the sound is *virtual*; it doesn't produce any actual sound waves in your room. The *real* sources of the sound are two boxes whose job is not to sound like the recorded thing sounds, but rather each to present to one half of your auditory system a sequence of "cues" from which your brain (re)constructs an illusion, the virtual source. So the reflected sound will be consistent with the real sources of sound, the speakers, but will be *inconsistent* with the virtual source, in other words, inconsistent with what your brain "believes" it's listening to. In theory, almost all reflected sound (above mid-bass frequencies, anyway) will "muddy" or "blur" the stereo image and diminish spatial realism.
However, speakers are designed to be heard in normal rooms, not in anechoic chambers. Their frequency responses are roughly matched to average listening environments. In an average indoor listening environment, most of the sound you hear is reflected sound. Try to imagine the difference between hearing someone speak from ten feet away in your living room and hearing them speak with the same force in a grassy field. The sensitivity rating of a loudspeaker is usually given as a single number, but to be accurate, you really need two: "anechoic" and "in room" responses. The "in room" response will typically be several dB above the anechoic" (6dB is a doubling of measured response). Making your listening area more like an anechoic chamber more closely approaches the theoretical ideal of stereo playback: two (equidistant) point sources and no secondary reflections. But moving closer to that ideal will almost certainly move further away from the speaker designers' anticipated playback environment, and the environment to which the speaker's frequency response is "tuned." It is quite possible that this departure would result in one or more "dips" in the upper frequencies and that this could be perceived as a "deadened" sound. It's a trade-off.
One way around this trade-off would be using a sophisticated digital equilizer from a company such as TacT. A digital preamp with hundreds of frequency bands is linked to a PC running a program that, using a microphone known to the system placed at the listening position, calibrates the frequency response for the precise details of your speakers, their placement, and the room itself. So you could design the room to reduce secondary reflections, preserving stereo imaging, while letting the digital equilizer compensate to avoid tonal inaccuracies. (I don't believe these systems are compatible with DSD yet.) I've read mixed reviews of these systems, and they don't really seem to have caught on, but in theory, it should be one hell of a tweak.
Bit of a long-winded answer about foam, I guess. Sorry 'bout that.
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Post by Khorn September 20, 2004 (22 of 30)
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LC said:
Bit of a long-winded answer about foam, I guess. Sorry 'bout that.
Don't worry , what you say is interesting as my friend and I have gone through just about everything that you mention over the last few years. I have even considered the TacT stuff. I did do some active room correction EQ using a Tascam prametric equalizer in a previous room/system situation although I found that there was perhaps too much distortion added by having the EQ in the chain. It produced a slight but noticeable "veil" in transparancy.
I find now that in my music listening room (I have seperate rooms for Audio and Video now) due to the size which is about 14' x 11 1/2' with two openings on the opposite ends of one wall, I am in effect "near field listening". This of course may seem strange with speakers the size of Klipschorns but I find that it (the room size) eliminates interactions that would be present in a larger space. As a matter of fact this present room is acoustically superior to any of my spaces in recent memory. Too many people pay little attention to or, dicount entirely room/system interaction which is of course a mistake as the room is very much a system component on par or even more so than any other.
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Post by LC September 20, 2004 (23 of 30)
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Khorn said:
I did do some active room correction EQ using a Tascam prametric equalizer in a previous room/system situation although I found that there was perhaps too much distortion added by having the EQ in the chain. It produced a slight but noticeable "veil" in transparancy.
Too many people pay little attention to or, dicount entirely room/system interaction which is of course a mistake as the room is very much a system component on par or even more so than any other.
Equilizers, of course, have been around for a long time, and people used to spend hours getting everything to measure right, only to find that it sounded like crap. Part of the problem was too few frequency bands and part of it was running an analogue signal through all that extra stuff. Digital EQ may well survive or, like active speakers, it may never make much of an impact because it just doesn't rub people the right way, despite its theoretical advantages. I know I'm drawn to simplicity of processing and signal path.
People do not understand enough about room interaction. The room is quite possibly the single most important component. You know how many people get gear home from the dealer and discover that it doesn't sound as good as it did in the showroom. When I talked to a TacT dealer a few years ago, he was laughing at some of the really expensive speakers and mocking Wilson's policy of sending a certified technician out to your home when you buy their big speakers to help you place them right. "The fact is," he said, "that you can measure any speakers in most rooms and the idiosyncrasies of their placement within that space will yield frequency responses so different that you needn't even bother getting two speakers from the same manufacturer" (since response profiles between speakers typically differ less than they do between speaker locations).
Of course, it's easy to see why there isn't much enthusiasm for this stuff. It's complicated. With very few exceptions, there's nothing you can buy to fix it. And even the best digital gear like the TacT may well have other sonic drawbacks.
Maybe I'll just pick myself up a new "quantum resonance electron aligner," or upgrade the volume knob on my amp. . .
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Post by Dan Popp September 20, 2004 (24 of 30)
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Two comments on what I've read so far:
1) Speakers are not tuned to rooms, as there is no way for the designers to know anything about the playback environment. In the case of a ported speaker, the speaker is tuned to the resonant frequency of the enclosure (the speaker box) so that you get an extra "oomph" from the port at that frequency, the lowest one the box will produce. I'm speaking in generalities, of course: some manufacturers may intentionally tune lower to avoid certain distortions, or partially flatten the peaky response of that design.
2) Equalization is a frequency-based solution. Room modes are a time-based problem. The standing waves in your listening room occur because of the physics of sound energizing the air in a real space over time. Equalization cannot solve that problem. At best it can mask it, while introducing other problems of its own.
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Post by LC September 21, 2004 (25 of 30)
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Dan Popp said:
Two comments on what I've read so far:
1) Speakers are not tuned to rooms, as there is no way for the designers to know anything about the playback environment. In the case of a ported speaker, the speaker is tuned to the resonant frequency of the enclosure (the speaker box) so that you get an extra "oomph" from the port at that frequency, the lowest one the box will produce. I'm speaking in generalities, of course: some manufacturers may intentionally tune lower to avoid certain distortions, or partially flatten the peaky response of that design.
2) Equalization is a frequency-based solution. Room modes are a time-based problem. The standing waves in your listening room occur because of the physics of sound energizing the air in a real space over time. Equalization cannot solve that problem. At best it can mask it, while introducing other problems of its own.
Thanks for this, Dan.
1) "Tuned" was not the right word, because it does mean something quite specific in the case of cabinet, port, and transmission line designs, and this is not what I meant. But surely designers know at least something about the average playback environment. Are you saying that speaker designers don't count on the fact that speakers will not be used in anechoic chambers when deciding if their frequency response is acceptable, because, for example, an accentuated upper range would be compounded in an average room with surfaces of drywall, wood, etc.? I may be quite misinformed here.
2) I agree that equalization can at best mask the problem of standing waves. But standing waves wouldn't have much to do with either problem I was discussing, would they? Room modes can result in "lumpy" sound, with bass frequencies "boomy" or "sucked out" at certain places in the room, but they only occur with long wavelengths corresponding to frequencies below those whose subtle timing cues the ear/brain uses to construct a virtual sound source, and whose tendency to bounce around a listening space would make it sound brighter or deader. So I'm less clear about this point.
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Post by mdt September 21, 2004 (26 of 30)
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LC said:
Thanks for this, Dan.
1) "Tuned" was not the right word, because it does mean something quite specific in the case of cabinet, port, and transmission line designs, and this is not what I meant. But surely designers know at least something about the average playback environment. Are you saying that speaker designers don't count on the fact that speakers will not be used in anechoic chambers when deciding if their frequency response is acceptable, because, for example, an accentuated upper range would be compounded in an average room with surfaces of drywall, wood, etc.? I may be quite misinformed here.
2) I agree that equalization can at best mask the problem of standing waves. But standing waves wouldn't have much to do with either problem I was discussing, would they? Room modes can result in "lumpy" sound, with bass frequencies "boomy" or "sucked out" at certain places in the room, but they only occur with long wavelengths corresponding to frequencies below those whose subtle timing cues the ear/brain uses to construct a virtual sound source, and whose tendency to bounce around a listening space would make it sound brighter or deader. So I'm less clear about this point.
It's right that the room has the bigest influence on the sound. When moving in to my new apartement i had the living room acoustically treated, by installing a bass trap especially calculated to the rooms dimensions and by dampening the first reflections from ceiling,floor and walls. Also a special Ccomputer program was used to determine the optimum speaker positions.What this did for the systems performance in all aspects is unbelievable.
I am convinced that such measures should be taken first and equalizing should be regarded as a last touch fine tuning.In my case the measuring of the response in the new room showed that no equalizing was necessary. Besides that the acoustical measures taken didnt only provide a good frequency response but also an adequate decay time, arrival time of the first reflections after the direct signal and level ratio of the reflections to the direct signal. All these parameters are essential to the quality of the reproduction alltough not frequency response issues.They can not be solved by equalizing.
In my case i see the use of EQ only after having taken these measures to completely smoothen out the response and above all to get perfect matching of the responses of the two speakers.
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Post by Dan Popp September 21, 2004 (27 of 30)
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LC said:
Thanks for this, Dan.
1) "Tuned" was not the right word, because it does mean something quite specific in the case of cabinet, port, and transmission line designs, and this is not what I meant. But surely designers know at least something about the average playback environment. Are you saying that speaker designers don't count on the fact that speakers will not be used in anechoic chambers when deciding if their frequency response is acceptable, because, for example, an accentuated upper range would be compounded in an average room with surfaces of drywall, wood, etc.? I may be quite misinformed here.
2) I agree that equalization can at best mask the problem of standing waves. But standing waves wouldn't have much to do with either problem I was discussing, would they? Room modes can result in "lumpy" sound, with bass frequencies "boomy" or "sucked out" at certain places in the room, but they only occur with long wavelengths corresponding to frequencies below those whose subtle timing cues the ear/brain uses to construct a virtual sound source, and whose tendency to bounce around a listening space would make it sound brighter or deader. So I'm less clear about this point.
LC,
I'm not a speaker designer, but let me throw some ideas at you about designing speakers for a room:
We can assume that each room has three sets of parallel surfaces. The distance between these parallel surfaces dictates which frequencies will be reflected at exact multiples of themselves, creating a room mode, or standing wave. (You may be using these terms more precisely than I am). So any change in any dimension will cause the speaker/room interaction to change; i.e., it will sound different.
But think about this as well: What if everyone had the exact same room dimensions for listening, but some had wall-to-wall carpet and some had hardwood floors? The hardwood floor people have a much more reverberant room overall, and also more upper-mids and highs, than the carpet people with the same speaker and the same room dimensions.
What if some people have a single layer of drywall fastened to a stud; and other people have plaster walls? The harder plaster walls are going to reflect bass into the room. The drywall is going to act as a "diaphragmatic absorber;" that is, slightly flex and absorb some bass energy.
What about doors? How many are there? Where are they? How big are they? Are they open or closed? These will have a great effect on not only the bass contained in the room (or escaping the room, as the case may be), but on the overall sum of reflective surfaces.
We could go on and talk about furniture and other things, but I think you will agree that designing a speaker for an "average" listening room is not realistic.
The reason that anechoic chambers are used is that we want to understand the sound of the -speaker-. As you or someone wrote above, our hearing mechanism can compensate to a large degree for anomalies in the -room- . Designers do need to have an understanding of various playback environments, yes, absolutely. But if they design the speaker for one environment, they will be totally hosed in any other room configuration.
I may have misunderstood your point about equalization. I will re-read. In any event, EQ should be a last resort for a very hostile listening environment.
P.S, OK, I think I get it now. You were talking more about "comb filtering" or interference effects from the highs and mids especially... ? I have to stick to my story and say that, while EQ could possibly compensate for some problems at the listening position, and it may be considered a very worthwhile improvement by the listener, I think he could have gotten better results with acoustical treatment, better placement of furnishings and/or speaker, etc. Thanks for the exchange.!
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I hope this post does not violate the posting rules since I am only endorsing products that I own and use.
Check out room lenses by Argent: http://www.roomlens.com/index.html. They also carry "Dark Matter" isolation devices now.
[added text: I see by their web site that Argent is not making these lenses temporarily. Here is another source in the US: http://www.superiorsightandsound.com/default.htm. Although I have no financial connection to superior sight and sound, the owners have been very close friends since college days.]
Hearing is believing. We use one unit to create a virtual wall in a large open archway to match the real wall on the other side of the room. Another unit is used to change the bounce and echo timing of speakers placed too close to a wall (has the effect of lengthening the room) and another unit is placed behind a couch to create another virtual wall. I was very, very skeptical when I first saw these but was able to test them in my home.
Our living room (used for 2 channel stereo listening) is long and narrow with lots of glass on one side, an open archway on the other and a large, open dining area behind the couch. The set of 3 room lenses correct for these deficiencies spectacularly. The home theatre used for multichannel music and SS movies has an open archway on the left wall.
We use Transparant interconnects and I am looking into getting a power conditioner by Richard Gray Power Company or PurePower. But I'd rather spend the $2,000 US towards a HDTV. I bought a $200 Monster conditioner/surge protector for my office TV-VCR-Tivo and noticed a huge improvement in the video signal. I was surprised at the bang-for-the-buck results.
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Post by Ernio November 13, 2004 (29 of 30)
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For a cheap tweek, I've been using just rubber hockey pucks. Very effective especially under cd players. Also good on amps and preamps.
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Post by veltri November 26, 2004 (30 of 30)
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If only one tweak were to be done with a max $400 US budget, which of the following would generally show the most evident improvement?
Power Bar
Interconnect cables
Speaker cables (MCH)
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