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Multi-Way Conventional loudspeakers with crossovers

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Old 25th May 2007, 01:49 AM   #871
JoshK is offline JoshK  Canada
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To tell the truth, I haven't heard PB...I just started to associate all the audiophile pop with the Diana Krall's/Norah Jones types...incredible mediocrity.
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Old 25th May 2007, 02:09 AM   #872
jamikl is offline jamikl  Australia
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Default Re edge difraction

Years ago I meddled around with chuck gliders ( model aircraft). One was very good - could stay airborne for 12 to 15 minutes. An unusual feature of this one was that three steps were carved into the trailing edge of the elliptical wing. On a 4 inch cord the steps were even over the trailing one and threequarter inches. Steps were .050", .040" and .030 inches. This affected the flow of air over the trailing edge. Has set me to wondering whether this might have any effect on baffle edges, particularly a baffle shaped like the stradivarius. The shelves would have to be deeper but would it work?
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Old 25th May 2007, 02:25 AM   #873
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As my system gets better, I'm often surprised at what music now draws me in that I never liked before. Even "Jazz at the Pawnshop" has its place. Of course, the system still has to play Shpongle and Tool and Pink Floyd and Arvo Part...

I do agree that large scale music with large dynamic range is the hardest to do correctly.
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Old 25th May 2007, 02:38 AM   #874
MBK is offline MBK  Singapore
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Just for completeness sake, phase tracking is important off-axis as well, and this is where driver polar response comes in. In the crossover region, if the polar patterns diverge significantly between drivers, you might achieve a perfect on-axis response with deep reverse nulls, but your off-axis response might end up with severe lobes, boh horizontally and vertically.

Off-axis lobing at X-O can be addressed through careful X-O fine tuning, including anything from asymmetric X-O's to different HF and LF X-O frequencies, but, but.... this is much more time consuming than working with drivers that have matching polar patterns at X-O to begin with.

Incidentally this is another area where even digital X-O's just can't fix physics.
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Old 25th May 2007, 03:58 AM   #875
GregOH1 is offline GregOH1  United States
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Default side panels/ edges

I presently have 2 12"triangular side panels cut to mount to the front panel . I was considering putting half round on the leading edge?? Is there any negative or positive effect with this treatment. I haven't been able to keep up with the edge treatment discussions. The 2x4 front panel is my own rendition of Lynn's drawing way back. ( offset drivers with a large flowing curve from the mid top to near mid side. Also what about quarter round on this inside corners?? Thanks for putting up with all my questions. I am cutting the holes Friday for the drivers and my design has the Bass at 6inoff the floor. I prefer not to go to 2in or so unless I am would seriously benefit from much lower. ( I do have hard wood floors, I presume that helps)
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Old 25th May 2007, 07:29 AM   #876
jirka is offline jirka  Czech Republic
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Does anyone know how many people from this forum use Azura horns or Oris/Orphean horns?
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Old 25th May 2007, 09:34 AM   #877
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Default Re: side panels/ edges

Quote:
Originally posted by GregOH1
I presently have 2 12"triangular side panels cut to mount to the front panel . I was considering putting half round on the leading edge?? Is there any negative or positive effect with this treatment. I haven't been able to keep up with the edge treatment discussions. The 2x4 front panel is my own rendition of Lynn's drawing way back. ( offset drivers with a large flowing curve from the mid top to near mid side. Also what about quarter round on this inside corners?? Thanks for putting up with all my questions. I am cutting the holes Friday for the drivers and my design has the Bass at 6inoff the floor. I prefer not to go to 2in or so unless I am would seriously benefit from much lower. ( I do have hard wood floors, I presume that helps)
I would get the bass drivers as close to the floor as possible. This is quite important. Not only do you get more bass, it's better bass since the drivers are closer to their virtual images. This speaker ain't no minimonitor, and a different set of rules apply.

I see no problem with the quarter rounds. It is desirable to cover the back surface with thick wool felt, and you'll need to figure out a strut system to support the drivers and stiffen the panel.
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Old 25th May 2007, 12:07 PM   #878
GregOH1 is offline GregOH1  United States
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Close it will be then -- bracing is still in the thought process. A friend has a cnc router that could make both artistic and functional rear bracing. Thanks
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Old 25th May 2007, 01:00 PM   #879
fred76 is offline fred76  Philippines
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Quote:
Originally posted by Lynn Olson


Beats me too, but that's what I hear, and I've heard plenty of live acoustic music. I've noticed that phase-plug geometry has an effect on this, so I'm surmising that turbulence effects are involved - no other form of audio reproducer has such extremely small internal acoustic surfaces and transmission paths.

Another interesting topic that arose from the discussion is that horn theory relies on a true plane wave entering the horn, but in practice, the wavefront from a cone driver, or the exit from a CD phase plug, isn't very close to a plane wave. The horn doesn't magically "straighten out" the wavefront - if anything, it gets more disordered, not less, as it makes its way through the horn expansion.

I have heard a horn that was driven with a nearly perfect plane wave. The horn was a large circular Tractrix with a 3" throat, driven by a single JansZen electrostatic element. It basically sounded like you'd expect, a REALLY BIG electrostat with lots of headroom and midbass presence. In tonal terms, no horn coloration at all, but it also had some of the physically forward, in-the-room spatial perspective of large-format horns - quite different than the faraway perspective of a typical large electrostatic panel.

Aleksandar at RAAL had similar experiences with his experimental horn-loaded ribbons - the horns sounded really good, but not the same as the open ribbons, with the most of the difference being a different sense of perspective on the music. That was my take on the electrostat-horn as well - the difference between transported to the musicians, versus the musicians being in the room. Much of this is due to polar-pattern differences illuminating the local environment, but I also suspect the ear is directly sensitive to the shape of the wavefront itself. I suspect a highly curved spherical wavefront is interpreted as coming from a location nearby the listener, and as the listener moves further off-axis, the smooth curvature becomes more disrupted.

In a later conversation with John Atwood, I was mentioning how the large-format Tractrix and Le Cleac'h horns have 90-degree dispersion in the technical sense - they sound good, FR response seems all there, etc. - but the real 3D quality and hyper-vivid tonality extends to about one seat-width. So in effect, the horns have 90 degrees of high-quality sound, but only 10 degrees of super-quality sound. If you're sitting where you can see the entire surface of the driver without obstruction, that's the super-quality zone. (In my experience, at least.) In a really dialled-in top-quality horn system, the best sound is either directly on-axis - looking right smack into the drivers - or just ever so slightly off-axis, depending on how the system was set up. When you sit far enough off-axis so the drivers are no longer visible and disappear behind the curve of the horn, there's a loss of focus and precision, compared to the on-axis (or close to on-axis) listening experience.

JA and I were wondering whether this is an artifact of the rough wavefront entering the horn - it emerges reasonably intact in a narrow beam (where the horn isn't doing much), but gets more disordered further off-axis, resulting in time dispersion and small-scale irregularities in the polar pattern. Cone drivers seem to be the reverse of this - they commonly have highly directional colorations that fall in a narrow 5~10-degree window, and sound smoother, more natural, and less "megaphone-like" slightly off-axis. It's part of the reason I'm considering a 5 to 10-degree slope on the open baffle, with a separate aiming assembly for the tweeter.

It would take an interesting measurement protocol showing impulse response vs off-axis, a sort of 3D waterfall. I think JVC once did this in an early 1980's AES paper, making some interesting graphs that looked like waves breaking on a beachfront. The ribbon/horn had much nicer looking off-axis impulse response than the usual CD/horn, with the mundane dome tweeter looking best, as expected.

P.S. About the Edge simulations - you're getting close, just use a greater rake angle, maybe 200 to 250 mm of overhang, larger drivers (315 mm), even spacing between the 6 drivers, and measure at 3 and 12 meters.
Hi Lynn,

On a related topic, here's a thread on another forum where Jean-Michel Le Cleac'h discusses his POV:

WRT Dispersion, directional pattern, aes papers, etc...

Somewhere in that thread it's interesting to note that he also mentions this:

Specialised music lovers may try to retrieve a part of the missing information using some acoustic treatment of their listening room, playing with constant directivity loudspeakers, more or less reflecting zones in the listening room, etc... Some of them obtain convincing results in having the atmosphere of a jazz cavern by example, but don't play any symphonic music in the same listening room or a choir...
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Old 25th May 2007, 05:08 PM   #880
MBK is offline MBK  Singapore
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Some more thoughts on "dynamics: exaggerated or not in horn systems?"

It occurred to me that we all often listen to horn systems: clubs, PA systems, and most unnoticed, movie theaters (often horn arrays as well). I don't recall having impressions of exaggerated dynamics in these instances. My direct experience of home horn systems is rather limited, some Lowther/Azurahorns, some vintage systems... and those I heard rather surprised me by the intense level of detail, not so much by the dynamics.

Not to mention that I am always surprised by the really explosive nature of live instruments. A piano attack up close is quite a transient, it really jumps out at you, and a single piano at live SPL level is not trivial to reproduce in terms of dynamics. We have an African drum in the living room, and even a moderate slap on it would test an average system to its limits in terms of SPL and dynamics.

So I am not sure if horns really do exagerrate dynamics. If so, then it must be some domestic horns rather than pro systems. And here I have two possible explanations:
- too close a listening distance. Maybe some elements of horn physics demands a proper unfolding of the sound field that only comes with distance
- home systems not properly EQ'd due to passive, even minimalist X-O's.

Both would go a long way to explain the extensive detail heard in domestic horns, and why pro horn systems (movies, PA etc) don't seem to have either unbelievable detail nor unreal dynamics (to me at least). Simply put, Pro systems are EQ's without qualms. And a broad, un-EQ'd peak in the 3-7k range in some home brewed horn can very well enhance the impression of detail, easy to try on headphones.

WRT the nonlinearity of air: not sure if this is a factor. IIRC it leads to distortion in sealed boxes, via addition of 3rd harmonics. And seeing how compression driver manufacturers like to claim if the 3rd harmonic is well behaved it must also be an issue there. But, 3rd harmonics would rather indicate a compression effect, not an extension.
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