Beyond the Ariel

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GregOH1

GregOH1

Member
Joined 2006
The Horn
I took to heart all suggestion related to fit and finish. My neighbor is retired and is a first class wood man. He and I spent 3 hours today on the horns making sure the horn profile and finish is near perfect. The 745 drivers have arrived and Radian puts a nice approx 4" rubbery type gasket on the face. The barrel is dead flat and 6in. Diameter and we should have no problem with alignment. The 4 bolts will be tapped into the barrel with access to the nuts from an enlarged hole in the barrel side . Details of Mounting in a photo format soon. Making the 15 lb beast adjustable for time alignment is still in the ahh maybe tripod effect or brass ring on a sliding dovetail on the back brace. Happy to hear your measurements on the 745.
 
Lynn Olson

Lynn Olson

Member
Joined 2004
nutshellhifi.com/
GregOH1 said:

Happy to hear your measurements on the 745.
Click to expand...

They're not mine, I just looked very carefully at the Radian measurements on their website. They take a bit of interpreting because they are 1/3 octave smoothed and printed in a vertically compressed format, with 10 dB/div. To read them, you need to actually count out the peak/dips in dB's and see where they are.

The 850PB, for example, drops a substantial 10 dB in the 10~20 kHz region, while the deviation for the 745PB is half that. The 2" drivers also have more ripples in the 2~5 Khz region than the 1.4" drivers, despite the fact that the 1.4" drivers appear to be mounted on a horn with a 1.4" -> 2" adapter. Maybe the adapter is actually improving the unmentioned test horn!

Can't quite figure out the differences between the two lower models of Radian 1.4" drivers, though. Same diaphragm mass, same number of flux-lines in the gap, yet fairly different FR curves. The voice-coil mass and winding might be different, though, as it is with the two 1" Neodymium BMS drivers.

Let us know how you like the 18Sound and Radian drivers - we're all curious how it comes out.
 
J

JoshK

Member
Joined 2004
Lynn Olson said:

The whole point of subjective fine-tuning isn't to make the speaker sound great on Patricia Barber or Jazz at the Pawnshop (although that's what many audiophile mfg's do), but to get the speaker subjectively flat.
Click to expand...

I hear you loud and clear. PB & JATPS would be about the absolute last recordings I would use to test any system. That is what I call short fat bald middle-aged audiophile's little girl with a guitar music (sorry if I hit any nerves).

I like highly dynamic music, busy music, complex if you will...from Dream Theater/Tool to Tchaikovsky/Stravinsky. Jazz is lower than Rap on my preference scale. Anyway...not that Jazz sucks, I can appreciate it somewhat but I have a strong belief that audiophiles tend to like music that makes their system sound good rather than make their system sound good for the music they like. That is my audiophile pet peeve.

It is much easier to make your system/room sound good with small scale music as the acoustical space is closer to an audiophile's typical room. Not many of us have rooms the size of orchestral halls.
 
jeff mai

jeff mai

Member
Joined 2002
You want smooth - here it is:

http://www.azurahorn.com/Yamaha_on_204.pdf

After acquiring a pair of the same Yamaha drivers, I emailed Martin at Azurahorn and he sent me the above measurements. I believe they are un-smoothed 1/24 octave measurements. After seeing this I couldn't resist buying the horns.

I've taken my own measurements and they correspond quite well, although the combo has less LF response and more HF response in the far field than Martin's measurements show, which are taken at the mouth. I use a Hiraga style notch filter to flatten things out to around 10kHz.

JM Le Cleac'h is on to something good with this horn profile. And I highly recommend trialling his 3rd order, phase corrected crossover methodology. The improvement in image focus and detail over the standard 4th order L-R arrangement I was using is impressive.

Now if I could figure out a way to get the top octave without messing up the rest...
 
J

jamikl

Member
Joined 2005
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?
jamikl
 
jeff mai

jeff mai

Member
Joined 2002
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.
 
M

MBK

Member
Joined 2002
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.
 
GregOH1

GregOH1

Member
Joined 2006
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)
 
Lynn Olson

Lynn Olson

Member
Joined 2004
nutshellhifi.com/
Re: side panels/ edges

GregOH1 said:
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)
Click to expand...

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.
 
F

fred76

Member
Joined 2005
Lynn Olson said:


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.
Click to expand...

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...
 
M

MBK

Member
Joined 2002
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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