Constant Directivity without Horns or Waveguides

My hunch is that Revel puts the sharp edges on the cheap stuff, because it creates a distinction between the top of the line Salon II, versus everything else in their product line.
Don't underestimate the added cost of large bevels and round-overs in a factory production cabinet. Such features add a lot of machining steps and complicate the finishing process. I am certain that the Salon II cabinet has a much higher production cost than the Performa series.

But your main point is a good one. I happen to believe that minimizing high frequency diffraction is an area where we in DIY can achieve a significant advantage over production loudspeakers. KEF, Harmon (and others) have a lot of technological resources and institutional knowledge to draw upon, but when they make a cabinet with minimal diffraction signature, like a Blade or Salon, it costs them money, and that is reflected in the very high price. We can achieve a similar level of diffraction performance with a ordinary shop power tools... or even just using sandpaper. All it costs us is time and effort, and since we do this for fun, spending time and effort is the point.

j.
 
Don't forget the Blade is a coaxial mid/tweeter. So the tweeter is in a waveguide.

The KEF Uni-Q is a better driver than the SEAS that I used below. And I needed to move the crossover point.
But the point is, I didn't build a fancy curved enclosure. This is a 25cm wide box with a 7" coax driver above an 8' subwoofer. Nothing more fancy than a 5/8" round over bit.

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From Erin's site and data set
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Here’s another speaker that has arguably fantastic DI and a similar concept in baffle function

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It was discussed many years back here for its performance value


While never investigated as far as I know, I always believed those slot ports on either side of the tweeter had something to do with it…….likely there’s no simulation available though.

The nearly 9” woofer I suppose drags the directivity point needed for the tweeter lower and the steep filter allows for the lower XO point and directivity match?

I have these. I bought the version with the 3/4" tweeter, based on that blind listening test.

It's funny, I've really struggled to replace these. I don't have them hooked up at the moment (I'm always swapping speakers in and out.) I've tried a bunch of comparable speakers but these are tough to beat, and at the price, it's just a no-brainer. It's a bit of a bummer that Behringer went and chased after the planar tweeter trend and changed the design. I haven't heard their replacement, but it's difficult to image there's a whole lot that could be done to improve the existing design. IIRC, the original Genelec design (that Behringer cloned) used a Seas tweeter that's quite nice. Someone online did a tear down of the internals and Behringer didn't seem to skimp anywhere, except the amp (it's noisy.)
 
Personal experience……..for my home work space studio used mostly for mixing?…..I preferred the Q150 over the LS50 Meta for nearfield use. I suspect the LS might shine in the midfield, but up close, it’s too polite….the Q150 tweeter presents more neccessary detail to make critical mix decisions.
 
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The CD behavior on a non WG speaker is something I discovered back in the 90s when I began using composite cone drivers with extended FR past the beaming. I found that when you manipulate the driver CTC spacing on a larger baffle, you can get similar behavior to a WG on the HF. It does require much higher xover on the LF, so you need a midbass or midrange with very controlled breakup.

I was working with the Vifa 10MD39 paper cone mid and discovered it could be pushed far past the usual xover crossing to a small dome. I recall the mid LP to be roughly 6k. Since then I frequently used the 10MD39, as it sounded superb on vocals and other delicate midrange focused material.

The Seas Bragi kit is an MTM with similar CD behavior. I'm fascinated by the smooth off axis FR being an MTM. It also utilizes a mixed slope xover, so that in theory also shouldn't work as well as it does. The DXT lens tweeter does utilize a WG, but its not that big and therfore as effective lower down.

So perhaps by mistake I stumbled on the same phenomenon and early on adopted a more unorthodox approach to speaker design. I had tons of arguments with other designers but in the end my designs were well reviewed. Its just difficult to find appropriate drivers with such extended FR. The MTM arrangement can be successful with larger midbass drivers.
 

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One way to view this, at least for this numbskull, is through Q. Roundovers and edge treatment lower the Q of any reflections, and this doesn't only reduce the absolute magnitude, but may also lead to a more coherent and wider bandwith destructive interference pattern from the edge, so rather than being our traditional high-q comb filtering, we get a reasonably wide range of coherent cancellation on the sides of the cabinet.

This is the first good reason I have seen against offsetting the tweeter on the baffle, as you're no longer trying to "spread" the interference pattern, but rather, aim it for consistent cancellation. The "bad" diffraction you're trying to minimize is actually best minimized by focusing it into a single, low-Q coherent reflection equidistant from the driver. Toroidal or spherical mid/tweet setups would seemingly allow for the most "round waveguide-like" patterns. EDIT- with tuned distance from driver, pure spheres would likely set the point too high to have the interference pattern "work" for a wider CD bandwidth, potentially putting the pattern narrowing as a dip within the passband rather than a tuned, matched range.
 
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The Devore driver isn’t the same except for the cone color and size…..modded and phase plug added.

The SEAS A26 crossover is for the simplicity crowd…..a single cap on the tweeter….that’s all