That's the most important point! If you know the "why", then you can make more intelligent decisions about your build, rather than just following a recipe blindly.I now know not only the 'how' but also the 'why' behind determining the widths of baffles,
Exactly! That's why you see the entire front end of many studios as one solid surface, wall-to-wall. So in fact, the left soffit is also part of the right soffit, to a certain extent. I have my reasons for sometimes breaking that continuity a bit with the center section, recessing it a bit (as you can see in Steve's room for example), but it's still a solid surface... sort of!surely the middle section between the two 'actual baffles' would also be considered part of the baffle?
(not all my secrets!).If you build it as one complete, unbroken surface, then you can also include the opposite soffit, and the opposite wing...So, really half of the middle section, the part around the speaker itself plus the wing would all make up one 'infinite' baffle per speaker?
Yup!In that case, the baffle could end up being very wide indeed, thus lowering that baffle step considerably.
As soon as it stops being a baffle!I must ask then, at what point does a baffle stop being a baffle and simply a side wall?
Sounds cryptic, but it's that simple. As soon as there is a major discontinuity in it, such as a large change in angle, or a break, or an absorption panel, or a diffuser, or a slot wall, or anything else where the surface is no longer contiguous solid, massive, and rigid. Of course, the further you get away from the speaker, the lower the effect is, since air attenuates sound anyway, plus we are talking about wavefronts that are expanding hemispherically (into half space) with the accompanying decrease in amplitude with distance, plus the grazing angle (from one point of view, the wave-front is going out at 90°, directly across the surface of the baffle), plus the impedance issue, plus a whole bunch of other things... So there really isn't much point in trying to make a 20-foot wide baffle, even if you could.As long as there is no large change n angle or other discontinuity between the baffle and the wall, yes. If there's a sudden change in direction (eg, a 90° corner, or even a 45° angle), then that's a different story. Take a close look at the room above: there's only a small change in angle between the soffit baffle itself, and the sliding glass doors... it's only 9° different, so not really an issue. But I would not consider the rear wall part of the baffle, since there's a 96° angle back there. No large changes in continuity.What I mean is, if there's nothing to say a baffle must be continuously flat forever then surely a side wall should be considered part of the baffle?
But there's another issue here to complicate your calculations: Sound is 3D, not 2D, and the baffle step response also happens in the vertical direction, not just horizontal! And it's the SHORTEST dimension that sets the actual response. So even if you could make your baffle 20 feet wide, you can't make it 20 feet tall! However tall it is, that's what sets the stage here. And while you might be able to angle your side walls in slight increments to increase the apparent width of the baffle, it's hard to do that with the floor!
Your speakers are maybe 4 feet above the floor, and perhaps 5 or 6 feet below the ceiling, if you are lucky, and the floor and ceiling are usually at very large angles to the baffle: typically 90°. So you definitely have baffle-step issue in the vertical direction, even though you might have "eliminated" it in the horizontal direction.In other words, there's not really much benefit to making your baffle a whole lot wider than your floor-to-ceiling height. There's certainly no harm in doing that, and it can have otter positive benefits, but it's not going to gain you a lot, from the point of view of baffle step response. Still very good for edge diffraction, SBIR, and other phase related issues, but not a huge effect on baffle step.... and once again, baffle step can be corrected easily, electronically.
Yup... compromises, compromises, juggle, juggle....but then I suppose that may cause unwanted reflections depending on the angle of those side walls.
Right. Because it is that immediate hard, flat surface that can cause some types of "lobing". Once again, it's not a huge issue, but still worth dealing with. And once again, sound is 3D, not 2D, so off-centering the vertical direction is important too.- Regarding offsetting the speaker in the baffle by at least 5/8 or 2/5 or 20% I am assuming this applies only to the 'actual' baffle around the speaker itself?
That is usually dictated by the room geometry: where the mix position is, the angles, distances, etc. Whichever way works out better for the speaker/listening position geometry is what you want.is there a preferred wider and narrower side or is it not important? For example, should the speaker be offset closer to the soffit wing, or closer to the middle section?
Yup!but is there a more important reason for doing so that I am not aware of?
See above: room geometry. You'll usually find that if you move them outwards, they'll be too far apart to aim at the mix position, without having to put a very large angle on the soffit, which also has it's consequences. And that "20%" rule is not written in stone either! If you have to move the speaker a bit right or left to make things fit, that's fine.... compromises, compromises, juggle, juggle....
That's part of the final room tuning process. It's great that you have them on separate amps, as that gives you more flexibility in tuning, but it also multiplies the complications.... Not trying to scare you, but tuning three-way crossovers and three amps on each side, is very complicated! Not for the feint of heart... It's hard enough to do it with just a pair of active speakers and a sub...- Lastly, I think it's important to mention that my monitors are actually tri-amped. I have an active crossover unit and 3 power amps, 1 separate amp channel per driver. So that will help to balance the power once I figure out how to set it properly.
- Stuart -
