Room Coupling |
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回覆 (4): Room Coupling
Whether you are using panel speaker or not, the coupling point remains pretty much the same. For proper alignment of the drivers, however, this Spendor BC III has to be pushed half an inch closer to the wall behind, measured from the top dead centre of the speaker cabinet.  
回覆 (3): Room Coupling
Room modes  
Room modes (or resonances) are a function of the room itself when different dimensions interact with each other. It happens with all enclosed space and hence every room would have room modes one way or the other. My room has been so calculated that these interactions only produce good resonances (+/- 3 db or thereabouts) which are conducive rather than destructive to music reproduction. It does not really matter what kind of speaker is used.  
This is fairly similar to the effects of good halls. No matter what orchestra is playing, you would have good sound. If the hall is wrongly designed, particularly its shape and dimensions, remedial measures, whether by way of flying saucers or damping of the most exotic kind, are not going to turn it into a good hall.  
Most audiophiles would try every means to eliminate the room influences and in extreme cases, I have seen dedicated music rooms looking more like anechoic chambers. Yet, none seems to succeed.  
I tend to work the other way round. Since all rooms would have resonances and these room influences cannot entirely be avoided, I turn to find ways by which I could make the best use of the room modes to augment the speakers. Yes, room coupling is one good way to making use of the room, or more precisely good resonances of the room, to bring life to reproduced music. Big orchestras of 150 players have yet required a good hall to express the very best of their performances. You have only two speakers in your room and they need to reproduce a full orchestra plus the ambience of the hall. If you don't ask your room to help, I don't see how you could have this Hercules task accomplished.  
Right, different rooms would sound different, but so are different halls. They all sound good provided they are good rooms and good halls.  
Simply put, I make the best use of room resonances instead of trying to get rid of them. To do this effectively, the room dimensions, or rather their proportions are vital. The height, width and length must NOT be simple multiples of each other. To further play safe, near multiples are to be avoided as well.  
Strict multiples like 2x, 3x etc. are lethal and absolutely incurable. Near multiples like 1.98, 2.95 or the like are likely to invite trouble. To play safe, I guess, 1.5 ought to be less desirable than say 1.6 and 1.6 would not be as good as 1.628469……..  
You see what I mean. The whole affair may turn very complex if you do not have a simple shoebox, in which case you would have more than 6 planes to deal with, for example, slightly L shaped, corridors, openings to other areas etc. And yet as long as the listening room is, by and large, a rectangle and the major dimensions desirable, you cannot go wrong.  
回覆 (2): Room Coupling
我同意!! :-)
回覆 (1): Room Coupling
2012 04 02 updated  
Doubts or suspicions around this room coupling thing do come up every now and then and honestly I am not surprised that 99% of audiophiles tend to dismiss it as just another untutored bullshit which is such a commonplace within the audio circle. Perhaps I should, every now and then, make myself better understood especially with members who are not familiar with our early postings.  
The method of locating the coupling point of the room was discovered, quite accidentally in fact, during one of my speaker placement exercises. The theory behind is hardly developed and since I am no engineer, it is best left for the scientists to find out the true explanation. What is important to audiophiles, however, is that it actually works. I just want to share this with fellow audiophiles with a view that this crude method can be further refined.  
Most acoustic engineers tend to indulge themselves in elaborate calculations on direct versus reflected sound along with absorption, diffusion and reverberation control, thinking that the soundstage, depth of field, ambience as well as layering all have much to do with striking the right balance among these variables. They all seem to forget one vital element — the myriad of spatial information is already embedded in a good recording and the job of home audio is to have them faithfully retrieved rather than recreated by any other means. Upon innumerable speaker placement experiments, I have been inclined to believe that this coupling phenomenon is far more complicated than sheer tonal balance adjustments and it appears to go way beyond sound wave treatments alone.  
From a slightly different perspective, it could be safely argued that there exists ONE spot within every room where the speaker sounds its very best. The method I use is expressly to locate this sweet spot fairly quickly without the strenuous efforts of trying out every inch of the room. One rather obvious effect is that the sound level coming from this spot usually goes up by 2db or more across the audible range. When the speakers are placed along the line of this spot, the room comes alive to propagate the sound very effectively, in much the same way as a good concert hall does to proliferate the sound of the orchestra to its full pianissimo to fortissimo bloom.  
Room Coupling
limage on SPEAKER PLACEMENT AND ROOM COUPLING (07-04-15).................  
Few of us, except perhaps the rare species of odd fossils of the pre-historic era, would have questioned the paramount importance of speaker placement nowadays. What is more debatable is where and how the speaker positions are to be determined. I have been a faithful follower of the room-coupling school and I believe that should be the best way out.  
Room coupling, I am quite positive by now, really goes beyond the deliberations over direct verses reflected sound sources, because the focal point remains relatively constant irrespective of what damping treatments we have on the wall surfaces in any given room. This focal point does not seem to move until the dimension of the room is drastically changed.  
To achieve effective room coupling, one has to locate the focal spot of the room first. There is a simple yet effective method to find this spot but I shall come back to that a while later. Every room has its own peaks and valleys acoustically. The peaks are resonances and the valleys are just the opposite, the suck-outs as a result of phase cancellation. I used to believe the coupling point is the spot where multiple resonances gravitate since it clocks the highest sound level throughout the audio band. If we look at it the other way round, however, the focal point of the room should more correctly be taken as the spot where phase cancellation is the lowest.  
When the speakers are placed along this focal spot, phase cancellation would be at its minimal obtainable within the room and the system will then be able to resolve, with the best of fidelity and the least of distortion, the myriads of spatial information contained in the recording. The width and depth, the ambience, the layering and instrument placements etc. will all spring to life. Proper sound staging, no doubt, has much to do with this phase coherency across the audible frequency range. We all know what would happen if one speaker is inverted in phase—there will be no imaging, no soundstage, and even no sense of direction. This is the result of serious phase cancellation. Even if the speakers are properly in phase, however, there would still be a fair amount of cancellation depending on where the speakers are placed.  
Ideally speaking, the room should be symmetrical in overall shape and the speakers symmetrically placed along the lengths of the rectangle. If one speaker is close to the side wall while the other is in the middle of the room, a rather common sight given the popular L-shape layout of sitting rooms in HK, there exist more chances for cancellation taking place at various frequencies, rendering the imaging blurred, stage collapsed and ambience lost.  
Once the speakers are coupled to the room, the two merge into one. The room becomes an effective extension of the speakers which in turn would cease to exist visually. Tuning for solid imaging then becomes much easier. Human ears locate the sound source by detecting the time difference of direct sound arriving at the ears. To achieve three dimensional imaging, all we have to do is to cut down secondary reflections from overwhelming the direct sound. While on this subject, I like to point out that I have tried the live-end-dead-end approach and it did not work to my satisfaction. I believe speakers are designed with the average western style living room in mind where upholstery, curtain, carpet and furniture all contribute to an acoustic environment which is neither too dead nor too live, but moderate throughout. This is something worth considering when we set about fabricating our listening area. It is not uncommon to find that the more elaborately contrived the HiFi room is, the less satisfactory it often turns out.  
Some fellow audiophiles suspect that because of the rather up-front placement of my speakers and because they are dipoles which radiate both ways, the large volume of space behind the speakers is encouraging tremendous amount of diffused reflections to create an artificial depth of field. Not so. Multi-mike mixed down recordings are rendered as they are, with absolutely no depth and instruments do stick with the speakers whereas a good concert hall recording has the ability to project the soundstage well beyond the boundaries of my small room while the speakers, despite their imposing size, simply disappear without a trace. Artificial depth just cannot differentiate as such.  
All in all, phase coherence does appear to be the key and with this key we stand every good chance to unleash a completely new dimension of audio realism.  
Here comes the core—the action part of the whole thing, a method that has proven to work wonders for me over the last 30 odd years.  
Have the speakers placed along the lengths of the room, about ¼ to 1/3 from the back wall, and ¼ the breadth roughly. Then play some vocal music, the hilarious type, the more instruments the better.  
Now walk slowly to and fro along the mid-line between the speakers, from one end of the room to the other and then back, may be several times to get the mind set (if the speakers are standing low, you may well have to crawl). Somewhere along the aisle, you would hear the sound getting louder and at the same time it rises above your head, filling the ceiling as if you’ve entered a Gothic church. Bingo, that is it, the focal point.  
Mark this focal point and drag your speakers over the lateral line crossing the spot. You’ve just coupled your speakers to your room. What is left, may be the crucial part yet, is to find the perfect stereo seat. As the name suggests, you’ll have to look for the widest stereo soundstage again along the aisle, between the speakers. If one side of the room does not give you the best definition and soundstage, try the other side. I was the one having my seat moved over to the wrong side of the room to get the best out of my system.  
Final note, if you are unable to find the focal spot despite trekking up and down diligently the whole afternoon, your room dimension is probably too bad to be a listening room. Try another room if you have one. If not you’ll have to move house.