Quick update on the measurements confusion.
Based on what I know now, I believe that the jzagaja's measurements posted on Auto-tech SEOS-12 product page
are most likely incorrect.
I do not think the chart was mislabeled because that just does not happen by mistake, all the labels are generated by the software.
More likely explanation in my opinion, which jzagaja seem to share, is simply imprecise positioning due to wrongly calculated acoustic center or angles. As MBentz pointed out
, even small mistakes at such a short measuring distance can lead to significant measuring errors.
Another reason for my conclusion is that there is a more recent set of measurements that jzagaja performed, this time using B&C drivers and measured at a larger distance. They look very much in line with BWaslo's measurements.
jzagaja kindly allowed me to share the ARTA files, attached.
DE250.zip 3257k .zip file
Here's is my attempt to plot a directivity sonogram using the data.
My ARTA skills are limited at best, I could not figure out how to change the degree axis to a more useful scale. But even at this level of details it seems to be very close to Bill's results, which is to say both measurements show SEOS12 as roughly 100 degree horn, slightly wider than the 90 degree target.
I do not want to overstate the difference 10 degrees make. LTD02 has argued rather convincingly that it does not. My opinion is that it is application depended.
Edit: to expand on my last point, in large rooms or outdoors the wider beam width may be an advantage. In small rooms typical for HT, all else being equal, horns with tighter directivity control are a better choice. A problem with LTDs chart, in my opinion, is that it assumes 45 degree toe in. If my experience is any indicator, 45 degree toe in is rarely an option, most people use less aggressive angles.
Here's Wayne's take on the subject