Tom Danley and Yorkville offer more...

maybe, the c'haracteristics of a deeper horn' are just refering to the way sound becomes more omni directional as the frequency decreases,  but using this slit and a lot of pressure created by the dimensions of the waveguide, the sound will perform as a 'deeper horn' and spread out a large amount more? Sounds quite wrong.
I guess that a non variable path length would just be like a straight tube, so maybe adding a few 90 degree corners creates lots of disturbance in the path taken by the wave and consequently creates a continuously varying path length. maybe this unstability in the path taken by the wave causes a higher pressure inside the wave guide, hence they said, 'such that the high frequency......'

Slot tweeter on a horn then!

It's right under the HF drivers, the DCX50, it's a new design, I believe someone else put the link here also... Anyways, here's the link.

http://www.bcspeakers.com/index.php?sez=1&categoria=4&id_descrizione=46&prodotto=199&id_descrizione_prod=54

What is interesting about the coaxial design is that B&C also is doing a version of their own, so perhaps the idea is not as bad as I/you might think. Well, if you look at the B&C version's distortion, heh, now that's a high distortion figure!

Like I said in my previous post, I've only done measurements in practical situations, so there's always something else that might cause the feeling of a good sounding unit. Perhaps it's because in large format systems you need quite clinical drivers so that they have enough throw and the sound gets better with a little bit more distance to the speaker. This is just what I've experienced when doing concerts outside.

When I heard the F1 Res4 + F218 set in small inside space, they did sound a bit harsh but clean and crystal clear, just as the line array using the BMS top end. But go outside when there's more that 5m distance to the closest speaker and it really starts to sound good. So that's why I don't always look at the HD figures because they're close range measurements, not from a distance and they don't always tell the truth in real situations.

But like I said, that's just what I've experienced, so here's my 2 cents!

Originally posted by gazman Arthur you've mentioned distortion in BMS drivers before, is that based on measurements you've taken vs other similarly priced drivers (eg. B&C) or listening tests? I just find it hard to believe that Danley of all people would use a HF driver that let down the rest of the system, he uses BMS in the SH-50's as well...

FYI, I have a 50Hz 4PI anechoic chamber with calibrated Earthworks and Clio mics, Audio Precision ATS-2, Clio8 FW QC, EASE 4.2 with Aura module and Easera in my lab. I've made distortion measurement with more than 100 HF drivers from European & Chinese manufacturers during the last 2 years, so my claim is based on facts.

Now, I never said BMS is a bad brand. I only said that I'm surprised that many manufacturers use them despite the high distortion numbers. Personally, I don't like them, it's my taste but I can understand that others don't agree. But when you listen side by side BEYMA CP380M ad BMS 4550, it's hard for me to imagine that you can chose the BMS. The Beyma sounds so more natural, with lot of presence compare to the dry, analytical BMS and the Beyma still shows significantly lower distortion numbers...
To give you an example, with same horn (90x60 elliptical 210x210x120mm),  with 1W/1m, distortion at 2,5kHz (where the human hear is very sensitive):
H2 on BMS 4550: 3,98%
H3 on BMS 4550: 0,25%
H2 on Beyma CP380M: 0,63%
H3 on Beyma CP380M: 0,05%

with 10 and 30W the ratio is nearly the same...

--Arthur