Although the following post deals more with speaker selection and placement than with building speakers, what I am proposing effectively means that I will have to build at least some of my own speakers to accomplish what I desire. Hence itâ€™s inclusion in this forum.
If Iâ€™ve done my research correctly, the following information is accurate. However, I present it as a question because it is based purely on reading-type research and deductive reasoning by a newbie, me. Here goes.
The center speaker is the most important one and should ideally be located with the drivers mounted vertically and the tweeter at ear level when seated. Of course, the center of the screen should ideally be at eye level, which basically puts the speaker right where the screen is. The only way to achieve this involves forward projection onto an acoustically transparent screen, the speaker being located directly behind the screen. Indeed, this is exactly how movie theaters â€œcenterâ€ the dialogue on their screens. So logically, those seeking sound perfection in their home theaters have only one option â€¦ an in-wall speaker behind a screen. It is a perfect solution â€¦ or is it? What other considerations apply?
All three front speakers should be fairly directional and pointed directly at the viewers. The reason for off axis fade (if thatâ€™s the right terminology) is that we do not want the sound reflecting off of the side and back walls. This would lose the directionality of the front speakers, and it would interfere with the directionality of the surround speakers. In effect, it would â€œadvertiseâ€ to your ear that you are in a room watching a movie, not in the middle of a battle field as the picture on the screen would have you believe. And when the action pans from left to right, you want the associated sound to move with it. This need for directional speakers is good because all drivers are mounted co-planar, which is exactly what a flush-mounted in-wall speaker requires. By contrast, both dipolar and bipolar speakers would need to â€œpushâ€ the screen away from the wall to allow for the multiple mounting planes (thereby wasting valuable room space).
However, it seems generally accepted that in-wall speakers seriously compromise the sound quality. Why is far from clear. I have read what I can on the subject and the only conclusion I can derive is that the area is at best poorly understood even amongst those with a passion for this sort of thing. For example, the A/V salesman I talked to said it was because the ports need lots of space behind them to function, i.e., to allow for free air movement so the drivers meet with less resistance and will therefore be louder and clearer at all frequencies. I have a hard time believing that this explains why a speaker sounds better 2â€™ from a wall than 6â€ from a wall. Besides, not all speakers are ported, and sealed speakers are also compromised when placed too close to surrounding objects.
A better explanation, I think, is that sound â€œbendsâ€ sharply and is seriously distorted when it meets the edges of the speaker box, which is why the edges on many high end speakers are seriously rounded. But even with the rounded edges, the bent sound will travel to the side of the speaker. If it meets other objects it will bounce around and soon be directed back at the listener. The waves of the reflected sound may cancel the waves of the direct sound at certain frequencies, and may heighten the sound at other frequencies. Bringing the speakers away from the walls or any other reflective surface would clearly minimize this problem. Great. That explains why it is foolish to place a floor standing speaker in a book-shelf and why book-shelf speakers should be placed flush with the edge of the shelf. It also partially explains why book-shelf speakers do not sound as good as floor standing speakers. But it does nothing to explain why an in-wall speaker suffers. In a flush-mounted system, there are no corners for the sound to bend around. Providing it is mounted on a flat wall well away from other objects, there are no other objects for the sound to bounce off of with unpredictable results.
Another theory is simply that in-wall speakers do not have optimum box volumes and may not even have optimally designed drivers in order to fit into a 2x4 wall cavity. Fair enough, but what if the speaker is mounted through the wall instead of in the wall? Perhaps the other side of the wall is in a closet, or maybe you use the protruding box as a shelf in the adjoining room. You can then build the box to sensible dimensions and shape and use good components. Is there still a problem?
Maybe. One person writes that â€œthe fundamental flaw with most in-wall speakers is that they are installed up high, we listen to them from down below. The wave interference between the woofer and tweeter that conventional crossovers permit will cause deep peaks and dips in the response- resulting in a hollow nasal sound.â€ He goes on to mention that the new â€œJoseph Audio Insider in-wall speaker has a patented Infinite Slope crossover so it sounds clear everywhereâ€. More research on these high-end speakers suggests that they sound as good as comparably priced floor standing speakers, suggesting that my post to this point must have merit. In other words, if you can identify the why and eliminate the underlying causes, there is no logical reason why an in-wall speaker can not sound just as good as a floor standing one. Note that you presumably do not need an infinite slope crossover providing the speakers are mounted at ear-level, at least if the author of those remarks is correct in what he says.
And now for my theory. I believe that most in-wall speakers are of poor quality. I also believe that floor-standing speakers do not so much have to be placed well away from walls as they have to be placed in locations that will not lead to problems with reflected sound. For practical purposes, this amounts the same thing, but if one were to recess a floor standing speaker completely into a wall with an opening exactly equal to the speakers dimensions, then that would accomplish the desired result. In fact, as a primary source of wave distortion is caused by the sound bending around the sharp corners of a speakerâ€™s box, eliminating those corners would eliminate the distortion. In theory, a properly built directional flush mounted in wall speaker should actually out-perform a floor standing model, all other things being equal.
Of course, the subject is way too complicated for me and perhaps for anyone to fully understand. A floor standing speaker has the advantage of being able to move it slightly to the left etc until it sounds best, while you simply have to live with wherever you mount your in-wall speaker. Moreover, you can demo various floor standing speakers until you find one that sound good to you in your room, but you will have to live with whatever you decide if you try my approach. Also, I am not sure how much sound comes out of the back of a sealed directional speaker, though I do not see why the sound could not be dealt with using sound-proofing materials around the box. Still, I am guessing that very few people have actually tried what I am suggesting, and, in terms of room layout, it seems ideal. The left and right speakers should, of course, be equal in distance to the viewer, but either you make the walls accordingly or you use floor standing models for those speakers, placing them on either side of the screen.
As for the surrounds, my understanding is that dipolar is the way to go. They have the advantage of being vague in their directionality (giving the allusion of being in a much larger room or even outside) and yet have sufficient directionality to be heard when it is necessary. But that is a whole other topic.
So here is the question. Iâ€™ve done my research (just ask my frustrated wife) and little is written that is exactly on topic. Does what I write jive with reality, or have I just fallen into my own line of b*** s***?