Bill - you are quite correct that the stereo reproduction cannot provide believable spaciousness because it comes from only two directions. That's why I want my room to be very live, and to yield good imaging through high directivity that avoids the sidewall reflections. No sidewall sound to be reflected and there is no need for sidewall absorbers or diffusers.
But if there are no early reflections - through speaker directivity - then you don't have to make that trade-off.
That's the nice thing about having a DSP based system. No, I can't change the directivity on the fly. I don't see any reason to do that. I have 3 different "modes" that I use for my system. The Music mode has a slightly elevated bass and some hf down shelving. The Movie mode has a more elevated bass with the same hf shelving. Then there's a Background mode that I used for.........well background listening. The right speaker is in a spot that sort of aims at the rest of the house. For the Background mode I run that speaker in mono with some of the hf down shelving taken out. Works really well.
It depends on the delay of the first reflection. If its far enough out it won't affect timbre but if it's closer in time, it does. I know Voecks would agree with that based on his past writings. It also has to be delayed enough but not too much to be perceived as spacousness. From "The detection of Reflections in Typical Rooms", Olive, presented at the 85th AES convention, preprint # 2719 (F-1): Lateral reflections from 10 to 40 ms lead to image spreading and spaciousness. Notice you don't get something for nothing, the image spreads.
Kantor also indicated keeping that side wall reflection reduces clarity "The key factor in editing is clarity, not audiophile accuracy. You need to hear splice points, noise floors, fades, etc. From a speaker design standpoint, this means a strong emphasis on clean axial response, with few early reflections"
Oddly enough, Moulton completely disagrees (talk about circle of confussion!). From Moulton: "WHEN we employ a loudspeaker that has both point sources and constant lateral output as a function of frequency, working in a room with hard sidewalls for broadband specular reflections, it turns out that the resulting playback phantom images and reverberance GAIN in detail, not LOSE" But Newell and Holland disagree finding “spaceousness and the resolution of fine details are largely mutually exclusive"
Then there is Toole's finding that keeping a strong sidewall (not reduced through overly tight dispersion) reduces error due to crosstalk (Pan's center image thread). See my post with Toole's quotes at http://www.diyaudio.com/forums/multi-way/277519-fixing-stereo-phantom-center-19.html#post4518639. So, there's an argument that too much DI and toe in increases this error. BTW, recording environment can't correct this, it has no knowledge of the distance to my side wall for example.
Next, regarding my point that the playback can and should be tuned by individual listeners to account for their differing perception of realism, from Toole:
"Ando et.al. (2000) found that musicians judge reflections to be about seven times greater than ordinary listeners, meaning that they derive a satisfying amount of spaceousness from reflections at a much lower sound level than ordinary folk"
Again from Toole:
"This is a caution to all of us who work in the field of audio and acoustics. Our preferences may reflect accumulated biases and therefore may not be the same as those of our customers."
So your premise that there is ONLY one way to achieve realism (spaciousness and accuracy) and that it's not listener dependent is without scientific precedent, in fact the science (with with fairly substantial independently repeated support behind it now) sufficiently refutes that position.
I can dig up much much more, but enough for now.
What I'll be trying in a new design will be a WWMTMWW using dipole mids and one W top and bottom cardoid leaving the intermediate W as bass reflex. I'm building a new set of test cabs for woofers now with removable sides to try different vent sizes and patterns.
Has anyone seen Amphions choice of a triangle shaped side vent? I 'assume' they did some extensive research to arrive at that shape.
Has anyone seen Amphions choice of a triangle shaped side vent? I 'assume' they did some extensive research to arrive at that shape.
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