Interesting because what I have seen in most coax drivers without a dedicated horn is quite a bit more ripple in the response of the tweeter.
Something wicked this way comes... (2020 speaker teaser content)
- Thread starter Duke LeJeune
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Yes they do, but my impression is that it's not as bad as in a fullrange driver. In a fullrange all of the high frequency output is modulated by the low frequency output. In a coaxial, tweeter output which comes in contact with the walls of the cone is modulated, but I don't know whether that directly affects tweeter output which misses the walls of the cone. I wouldn't think so; or at most, not very much.
Yup, it's a trade-off. And I'm not sure that my general preference for horn-less coaxials would hold up to a really well-designed coaxial with a dedicated horn.
But with a dedicated horn you juggle adequate horn size versus "breathing room" for the woofer. And the round-over around the mouth of a horn also matters, which adds to the size requirement for a "good" horn. So a horn big enough to work well will maximally reflect/diffract the woofer's output up near the crossover region, while a horn small enough to not mess with the woofer won't have good pattern control down into the crossover region.
I guess with one you will affect the tweeter and with the other you impact the midrange. Which is more detrimental to what we hear?? The most famous coax of all time, the ALTEC 604, obviously had a dedicated horn. They can sound as good as anything out there. Other famous ones, like Tannoys, did not have a dedicated horn and some swear by those. Until I heard the Radians is was not convinced by the non-dedicated horn types. Those are just damn good.
You're absolutely right, it's a tradeoff.
[blasphemy]I have heard at least three different loudspeakers with either the Altec 604 or a modern version thereof, and to me the horn coloration was distractingly obvious. [/blasphemy]
[more blasphemy] I wanted to add a high-efficiency speaker to my lineup to complement my SoundLab electrostats, so I eagerly sought out several different models of big Tannoys to listen to. I went into it with the expectation of becoming a dealer, based on their reputation. Unfortunately to my ears they lacked clarity, especially as the volume level went up. [/more]
I did not seek out the less expensive Tannoys which have a separate woofer because at the time I hadn't figured out that that might make a worthwhile improvement. But since then I have heard several hornless coaxials with separate woofers which sounded magnificent.
I have heard Mark Seaton's speakers twice. Mark uses a prosound coaxial (B&C maybe?) with separate woofers handling the low end. They sounded superb on both occasions.
Also Clayton Shaw (Spatial Audio) uses a Radian coaxial in a dipole system with a separate woofer. He went so far as to design a custom housing for the backside of the Radian which allows the compression driver's diaphragm to radiate backwards as well as forwards. Superb.
Danny Ritchie (GR Research) also makes a dipole system with a big prosound coaxial modified so that the compression driver radiates to the rear. I think he did that before Clayton. Again, in my opinion, superb.
And then of course there's the great Andrew Jones, whose more modest-efficiency custom coaxials also use a separate woofer.
So I THINK hornless coaxial + separate woofer = a winning format. It's what I would do anyway.
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All valuable experience. I have heard 804s twice as well as Urei’s once. Once was fantastic, once was colored and the Urei’s were pretty great as well. Dynamikks don’t really sound colored in an obvious way...for sure there is some (like all speakers) but this classic “horn “ coloration cliche.
Not yet. I finally got the custom tooling for the horns only two days ago, so we are probably still two or three months away from a photo shoot.
Hence the word "teaser" in the thread title.
Actually when I started this thread, January 1st 2020, by late June we were expecting to have shown at either Axpona or T.H.E. Show, as well as at Lone Star Audio Fest (which is about forty-five miles from me). So we DID NOT intend to be running the "teaser" thing for this long!
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The tannoys and Altec 604 are very different in sound, not one better than the other. Those who like the tannoy do so for its point source coherence and its earthy sound. Duke is right when he says they lack clarity, but with tannoy that doesn't matter to those who like it. And as Duke was looking to represent, the modern tannoys are just not good enough.
The Altec 604 are quicker than the tannoy in the upper mids and can be run with lower watts. Many 604 users move to boxes with small format Altec for mids and 15 inch for mid bass below. I heard one open baffle 604 which was quite nice and pleasant, especially at under 3000 quid. The stock 604 was supposed to be quite shouty and users usually mod the crossovers. With tannoy many mod crossovers as well. But suffice to say, both with Altec and vintage tannoys set ups sound quite different due to varying DIY styles and amps used
I haven't heard the Radian coaxial (was planning to visit Germany before the lockdown to do so) but based on what I regularly hear with the universum, the Radian sound is in different from both Altec and tannoy, it is more like TAD with focus on clarity, resolution, transparency.
The Altec 604 are quicker than the tannoy in the upper mids and can be run with lower watts. Many 604 users move to boxes with small format Altec for mids and 15 inch for mid bass below. I heard one open baffle 604 which was quite nice and pleasant, especially at under 3000 quid. The stock 604 was supposed to be quite shouty and users usually mod the crossovers. With tannoy many mod crossovers as well. But suffice to say, both with Altec and vintage tannoys set ups sound quite different due to varying DIY styles and amps used
I haven't heard the Radian coaxial (was planning to visit Germany before the lockdown to do so) but based on what I regularly hear with the universum, the Radian sound is in different from both Altec and tannoy, it is more like TAD with focus on clarity, resolution, transparency.
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You need to complete this speaker so Jonathan will stop making untrue claims!
Ha! Good for Jonathan! He's a first-rate ambassador for horns. He makes beautiful horns, and he helps make horns beautiful.
At first glance his little horn in that video clip looks a lot like the one we use in the Gina speaker, which is also solid wood, BUT ours is not a "Conical". My understanding is that a Conical has a straight, constant-angle wall from the throat all the way out to where the mouth round-over starts. In my opinion the theoretical drawback is the virtually inevitable angular mis-match between the exit angle of the compression driver and the entry angle of the horn, which will cause diffraction.
Ours is an "Oblate Spheroid", which uses a specific constantly-changing-radius curve to make the transition from the exit angle of the compression driver to the coverage angle of the horn. The Oblate Spheroid shape was found by Earl Geddes to introduce the least amount of disturbance to the wavefront for a given amount of angular change, the intention being to minimize coloration. In other words, the Oblate Spheroid prioritizes transitioning from the exit angle of the compression to the horn's wider constant-coverage angle in the most benign way possible.
However IF the exit angle of the compression driver MATCHES the coverage angle of the horn, there would be no need for a transition, in which case I think a conical would be the ideal.
That little "phase plug" thingy is interesting. I'm not sure what its net effect would be, but I think it will break up reflection modes within the horn, which would be beneficial. He says that it helps with "dispersion", so it's apparently doing things that I can't yet wrap my head around.
My forthcoming bighorns will be Oblate Spheroids, so I think Jonathan will remain the ONLY one doing solid wood Conical horns.
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Doesn’t OMA also do conical horns? I guess they have matched the driver’s exit angle and the horn angle or it would likely sound very uneven. The phase plug Thingy in this case would introduce diffraction, no?
Yes. Fleetwood Sound Company is a division of Oswalds Mill Audio, hence the resemblance.
Maybe so, but the exit angles of compression drivers are generally considerably narrower than the typical coverage angles of horns.
I don't know. I guess so, but my (unreliable) instinct is that it would not be as severe as a kink in the wall of the horn.
The phase plug might just be to stop intense beaming. I wonder if that could also reduce some horn sound if the right frequencies relative to horn size?
It's not obvious to me that a conicial horn would beam the high frequencies, at least not as much as something like a tractrix or exponential would. But I could be wrong.
(With a Tractrix or Exponential or other similar horn, in general the rate of curvature increases as we go from throat to mouth. The pattern width of the shorter wavelengths is controlled by the region near the throat, where the curvature is least and the coverage angle is narrowest. As the wavelengths grow longer, the pattern width is progressively controlled closer and closer to the mouth, where the walls of the horn are flaring out ever moreso, thus the pattern width tends to widen as we go down in frequency. In contrast the Oblate Spheroid has its tightest curvature closest to the throat, and then almost becomes straight-walled, until we reach the mouth round-over. Each type does some things better so it's a juggling of tradeoffs.)
If the phase plug does indeed reduce "horn sound" - which it might! - imo that would be a big deal. I presume at some point they auditioned it "with" and "without", and liked the sound better "with".
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External phase plugs reduce high frequency interference near the driver due to lateral reflections. They are placed in the voice coil cavity in place of a dust cap in conventional drivers, so that area is filled and the cavity doesn't cause high frequency weirdness, for the OMA application it may also have an effect on dispersion or even be the primary use. Those "bulbs" on the end of some single driver phase plugs are intended to effect dispersion while the more bullet shaped ones don't seem to effect dispersion much. My 4.5" wideband midrange drivers use the bullet type phase plug, I've experimented with a few different designs.
In the vid I think it was mentioned the goal is constant directivity from the conical horn, and I believe the phase plug is used to achieve this via diffraction.
In the vid I think it was mentioned the goal is constant directivity from the conical horn, and I believe the phase plug is used to achieve this via diffraction.
I was guessing he might be using a fairly large driver so his lower driver wouldn’t have to play as high, given that it needs to be higher sensitivity so maybe if it was geared towards bass it could work.
It was my understanding that a conical horn has the narrowest dispersion and thus would beam the most and be the most directional.
You may be right. I've been focusing on the thin vanes but the plug in the middle may be the key feature. It's obviously intentional.
A conical horn's pattern would depend on the angle of the walls of the horn, at most frequencies. It's hard to tell from the video what that angle is, but I'd guess ballpark 30 degrees each side (for a radiation pattern width of ballpark 60 degrees). At high frequencies the exit diameter of the compression driver (1" in this case) could be controlling the pattern width, such that it inherently beams like a 1" tweeter would and largely "misses" the walls of the horn. The phase plug might be designed to address that situation.
Incidentally I can't tell what that compression driver is, except that it apparently has a very powerful Neodymium motor. At first glance it looks like one of the more powerful B&C 1" drivers, but the back cover doesn't really match any of the ones in their current catalog. Close but not quite. My inclination is to suspect that it's a custom B&C, for which they use a slightly different back cover so that it can be differentiated from a stock item.
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Phase plug or a lens was common back in the 70's specially with studio monitors. Typically they focus the sound and extend high frequency response which is what I believe is it's purpose in the Fleetwood speaker. I have a sneaky suspicion that aside from extending the higher frequency it's positioned to break up some of the horn's coloration.
david
david
Very interesting! I had never seen anything quite like it before, the closest being the "vanes" in something like the TAD TH-4001, which (if I understand correctly) are there to manage the horn's cross-sectional area so that the expansion rate is exponential. But maybe they do other things (such as help with high frequency dispersion) as well.
My impression of Bill Woods, horn designer for Oswalds Mill, is that he's a very smart guy with a lot of tricks up his sleeve. I bet he has found work-arounds for any audibly significant issues, and I bet that little speaker sounds magnificent.
But he's not the ONLY guy doing a small speaker with a round (though not "conical") wooden horn!
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