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RE: Apologies for the long post, answers and some speculation on the ribbons

I don't know which item you are referring to as "not bad at all" as all issues in the prior post refer to the mid/bass crossover.
I find that you can tell low frequency direction from the event aspect of their initiation - which we localize perfectly even if we can't hear the actual tone. Which is why I always suggest to people that they get two subwoofers - not one.

Thanks for the figure on reflection audibility threshold. I remember that the 20ms rule is the threshold for separating "events". so if I can manage the reflection's path to go beyond 20 ms, or decay that much (17 db) then I effectively controlled them and the reflections become "reverberant field cues". So all you need is to have the speakers over 10 feet away from the first surface behind them. So that the distance back and forth would be over 20 feet, and thus have a 20ms delay for the straight back wave, and all the side bounces would have a longer delay than that. So if the mid/treble is 30 deg from the front wall with the tweeter's corner 6 feet away from it, then I get 7.4 feet to the first reflection, which bounces away from the listening seat axis to the side wall and from there back to the speaker - in my room the path comes to 17 feet, so I would just need to move the speakers just about 1 foot further into the room. And people with narrow long rooms can position their speakers straight ahead 10 feet from the front wall, or toed in a little and have the speakers 9 feet from the front wall and get no event smear.

Will try that out.

I don't think you got my point, the locations of the line sources are not that important. They just need to be:

1. located symmetrically to their counter channel line source in the room,
2. located more than 15 deg from the listening axis to either side (I have not managed to get good stereo at separations narrower than that)
3. Be roughly the same distance from the listening seat and in phase or orthogonal (makes for better transient behavior). OR
4. at least be in phase from the listening seat (by placement or electronic delay).
5. Radiate towards the listening seat from the front

I have had the speakers set up insie and outsie and got nearly the same soundstage I put them one in front of the other at 3 foot distance from each other and played with different positioning of the mid/treble panel just keeping the distances 3 feet different. Outside of wall effects I got substantially the same soundstage.

At the current crossover, there is a 1.5 inch wavelength. When the tweeter was crossed over in third order (same Fc), there was a serious head in a vice problem and things shifted if I tilted my head one direction or another. With the broad overlap of the 1st order crossover there is no problem, theory be damned. I wondered why Magnepan keeps the QRs first order on the tweeter. Well I see now. I also see what PG was after (even if he didn't know himself). By my calcs, this should be roughly transient friendly if not transient perfect.

The point of lowering the tweeter HP was in part to get the 11-12 khz area with less phase. The line array drops rather steeply around that area, so I wanted to give it an extra push like magnepan does with the second order LP for its midranges . since with a 1st order electronic slope on top of a 1st order acoustic I get a second order - but less phase.

Re the horn loaded idea, the lobing effect is interesting and makes me more curious to experiment further at some point, since getting a 3db gain with a horn is not a big deal.

Looking at your confines, I think there should be no downside to having a line array of Neo8 in front of a bass panel, and crossing over at a frequency that works for you to make the distance between the panels right for positioning in your room, or use a Behringer DCX2496 on the bass only and adjust the delay for the distance. I am inclined to go that way myself if I can't make a PLLXO work 2nd order or quasi 3rd (3rd with low Q). The ribbon tweeter (I am assuming you want one) can go next to the Neo8 array like the Tympani IV and IVa as I have it. But don't fear putting the ribbon in front of the Neo 8 line.

BTW there are about 6" between the center of the neo8 midrange and the tweeter. At the current crossover it is a 5 wavelength distance. Using my Marchand crossover at 5khz LR4 it is still 3 wavelengths. There is one cool thing to remember, that you are getting output from the entire array both on the tweeter and the midrange, so that lobing does not work as it does in point source drivers. There is the interaction of the center of the midrange and the center of the tweeeter, but most of the output comes from the rest of the array where the distance between say the output from the midrange area 5 feet up interacts with say the tweeter output 2 feet up (ref. floor). Meaning that there is a broad range of interaction distances rather than the narrow range in point sources, so while the average would be like a point source at the center of the mid or tweeter, the actual cancellation and construction are very broadly distributed - to the point where you can ignore them if the crossover slope allows it - the shallower the slope the broader the interaction. am I thinking right? is this sensible?



Edits: 09/16/10

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  • RE: Apologies for the long post, answers and some speculation on the ribbons - Satie 01:39:46 09/15/10 (0)

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