In Reply to: RE: Immersive posted by cawson@onetel.com on October 26, 2016 at 03:49:52:
Cawson: This is an interesting theory, but questions must be asked as the theory is put forward by the manufacturer of a loudspeaker brand that attempts to comply with this theory!Duke: True!
C: Firstly, is the theory itself valid? In a concert hall the reverberation is far far more than 10 milliseconds. However a small room in club or a pub may have reverberation time of this order.
D: The basic theory of minimizing early reflections while preserving later ones is valid, and is usually approached from the angle of room acoustic treatment instead of speaker design.
While we can't replicate the concert hall's reverberation time, we can still make worthwhile improvements by a) minimizing early reflections while still b) preserving substantial relatively late onset reverberant energy... that is, "late onset" within the context of our small room sizes.
The "10 millisecond" target comes reading Earl Geddes and years of playing with full-range dipoles (SoundLabs).
C: Next, why should reverberation created by a group of live musicians exist in a room, but reverberation generated by conventional speakers not exist in one's listening [room]?
D: Reverberation definitely still exists in the home listening room, what we want to do is make it work WITH the first-arrival sound instead of AGAINST it. So we don't want it to start out too early, and we want it to be spectrally correct.
C: Perhaps one could argue that the instruments in a band emit their sound in all directions. Well, imagine listening to a band (with trumpets, saxes, a singer, etc) with all the musicians facing away from you. Wouldn't the sound be most unsatisfactory? Live music is largely (but not wholly) directional - as are conventional speakers.
D: We get our primary imaging cues from the first .68 milliseconds of the first-arrival sound, which works out to about 9 inches (corresponding to the distance around the head from one ear to the other). Then the "precedence effect" kicks in, and we largely (but not completely) ignore directional cues from repetitions of that original sound, i.e. reflections. But we still pick up timbre and loudness cues from those reflections, so they do matter. We also get our sense of the acoustic space from the reflections.
So I don't think that what I'm advocating is analogous to having the musicians face away from you... more on that in my next paragraph.
C: Conventional speakers are designed to send all their sound towards the listener, but most are still best placed away from back walls.
D: Conventional speakers generally have a wide but non-uniform radiation pattern that gets wider or narrower as we go up and down the spectrum due to the radiation patterns of the drivers. So let's say a conventional speaker has a roughly 180 degree radiation pattern. What I do with my pair of directional arrays (front and rear) is, chop that 180 degree pattern into two smaller 90 degree patterns, aim one at the listener, and then aim the other in a direction that gives us a lot more benefit than if it had gone into early reflections.
C: If one wants longer reverberation such as experienced in bigger live venues or concert halls, one should perhaps be looking to delay (by an electronic circuit) a secondary sound signal - and perhaps have it come from rear and/or side speakers. There's no sign of this in the thesis above.
D: Ken Kantor did exactly that years ago in the Acoustic Research "Magic" speaker. I believe a worthwhile improvement over conventional speakers can be made with a passive system done well.
C: Then one has to ask why so few speakers offer the seemingly simple solution of back facing non-bass drivers. One or two other makers have backwards-firing drivers that seems similar in concept. With one the volume level was fully adjustable, but comments from owners seem to suggest that the sound was less "muddled" with little or no back-firing.
D: Dipoles set up with sufficient distance behind them (5 feet or more ideally, 3 feet minimum imo) are a widespread example of a Two Stream paradigm setup.
There is such a thing as too much reverberant energy (cough cough Bose cough), and if the front-firing drivers already have a wide radiation pattern, adding rear-firing drivers may be too much. That's one of the reasons why I shoot for somewhat tighter pattern control with my arrays.
C: Doesn't the effect depend very much on the distance to the wall behind the speakers and the material covering the wall? Presumably to get this effect, one needs about 5 ft behind the speaker (sound travels 10 ft in 10 ms) and it has to be reasonably reflective of sound. This can be achieved in most homes, but certainly not in all - including mine unfortunately.
D: The up-firing (from the floor) configuration that James Romeyn came up with, which he calls "Late Ceiling Splash", allows placement of the speakers much closer than 5 feet to the wall.
C: So the theory is one that has not been taken up by any of the big boys in the loudspeaker industry. One has to ask why not. Even top-of-the-range multi kilo-buck models almost never include this feature of back firing drivers. Are they all wrong?
D: Again, a dipole speaker set up well is a Two Streams Paradigm system. Maggie, Quad, Martin Logan, SoundLab, etc.
If the big conventional speaker boys have decided against it, that's fine with me! The market seems to be more interested in uber-tech driver diaphragms than in psychoacoustically beneficial room interaction anyway. In order to do it right, imo they'd have to get much more aggressive with their radiation pattern control, and that means big cones and/or horn-like devices, both of which put off most audiophiles. I'm small enough that I don't need much market share.
C: Is this "immersive" sound" feature only appreciated by a handful of listeners with the rest of us considering it "muddled sound"?
D: There are tradeoffs virtually every step of the way in speaker design (and anyone who tells you differently is in marketing). I don't want too much reverberant energy, hence the narrower-than-normal patterns that I use. Remember that it is the early reflections that degrade clarity the most, which is one reason why a good horn system can have such good clarity. But horn systems tend to sound a bit dry, so another way of looking at my approach is, I'm retaining the freedom from early reflections of a good horn system but doubling up on the beneficial later reflections.
C: I don't know the answers but I'd love to try a pair of these speakers in my very definitely difficult listening room. No UK distributor unfortunately!
D: Tell me more about your room, if you don't mind.
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
Edits: 10/26/16 10/26/16
This post is made possible by the generous support of people like you and our sponsors:
Follow Ups
- Excellent points - I'll try to address them... - Duke 09:59:36 10/26/16 (2)
- RE: Excellent points - I'll try to address them... - cawson@onetel.com 14:59:41 10/26/16 (1)
- RE: Excellent points - I'll try to address them... - Duke 16:51:31 10/26/16 (0)