This is the nathan, but the vertical lobe should be of a similar character.
http://www.princeton.edu/3D3A/Directivity/Nathan_Directivity/7. NathanContVer.jpg
http://www.princeton.edu/3D3A/Directivity/Nathan_Directivity/7. NathanContVer.jpg
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Thus far, we only know it for the Nathan, from actual measurements by Markus and those recently published in the Princeton directivity study, which substantiate Markus's findings with respect to aiming of the forward axis. Hopefully, Earl addressed this apparent issue in his redesign of Nathan.
The debate between Wayne Parham and Earl with respect to axisymmetric vs. asymmetric waveguides is thoroughly documented in these diyAudio pages. The larger C/C distance mandated by axisymmetrics may be compensated for with a lower crossover frequency than a similar-width asymmetric requires, but Wayne describes how the shorter vertical height of an asymmetric may be used to advantage in augmenting the vertical pattern control to minimize anomalous floor and ceiling reflections, obviating the necessity for room treatments in these areas.
Earl has conceded that an elliptical OS waveguide might well comprise an improvement over his current round ones, for other reasons, and, as of last year, was prototyping a design. You'll find his early OS papers were done using an elliptical implementation, but if there have been updates relating to the current effort, I have not seen them posted here....
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I believe Earl has addressed that -- steeper filters dig higher-Q holes, is all....
Works for me. I'll take higher Q holes anyday.
Hmm, that is odd. In a vertical off angle measurement the woofer is going to move closer to the mic in one direction and farther away in the other but this seems like quite a change. Maybe the center of the waveguide was chosen as the rotation axis so there's an even more pronounced change in woofer to mic distance as it's rotated?
Or as you say, maybe the room isn't perfect at the difficult low end.
It also states they were done in an anechoic chamber; see "Notes on the measurements" here:
3D3A Lab at Princeton University
The chamber is described here:
3D3A Lab at Princeton University
3D3A Lab at Princeton University
The chamber is described here:
3D3A Lab at Princeton University
Yes, I read the debate. Yes, an elliptical OS would be a great choice but even then we need a LARGE one to go below 1000Hz. I think its more important where we push the woofer then the CTC issue. CTC is a DIYers read herring, too much focus on something not exactly audible.
There is only one true fact....Both ways of thinking produce excellent results so its a lot about nothing. I use active XOs for everything so honestly CTC is not even a concern but I think its unfair to push people into any one way of thinking. I think the discussion about the CTC is overblown when it comes to the overall differences with larger waveguides.
I believe Earl has addressed that -- steeper filters dig higher-Q holes, is all....
steep filters and linear phase control......its all good!!
It "sounds" as if it's a binaural convolver with cross-talk cancellation (like RACE).
The literature specifically mentions a recorded audience sounding as if it's near the listener as opposed to being "flipped" and as far away from the listener as possible (which is unfortunately normal for current stereo reproduction). I've only ever heard that effect on binaural recordings with headphones.
Of course like RACE, cross-talk cancellation is far from perfect (without regard to "coloration" problems).. so they recommend more directive loudspeakers (at least at higher freq.s).
The "requirement" that they measure at your location and your own HRTF's for the convolving is a bit over-blown IMO. For the convolution it's better - but a broad range of "dummy" head settings should have one that get's you 95% "there", and the on-location correction (RACE et al) could easily be made for auto correction by the user with the appropriate hardware/software. In fact, they mention that you can simply "encode" the recording (rather than real-time processing) - and it it should largely work for most people.
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Record from your hears and listen through headphones, recording can be mistaken for reality.