Buying used Compression Drivers – What Condition is acceptable?

Some days ago, I bought a pair of used JBL 2447J compression drivers at a well known German selling platform. The seller rated the condition of the drivers as very good but showed only one photo in his sales advertisement:

Offered JBL 2447J

I contacted the seller and asked for more photos to show the condition. However, the seller refused, saying that the drivers were built into his setup and that the drivers would only be removed after the sale. However, he literally assured me that the drivers were in perfect original condition. In retrospect, I’m obviously annoyed with myself for not insisting on taking more photos, but so far I’ve had consistently good experiences. Until now…

Continue reading

A True Grand Cinema Horn

Recently, I was involved in a private discussion with a guy who introduced himself as expert for home cinema setups. The topic was about a horn that could be used for a really large home cinema setup. Not what many would imagine immediately like a small room for 2-3 people. No, truly large for 10 or more people and the listening rows / seats have a third dimension in the vertical direction the more far away they are from the source. For such a setup, the horn should have very good directivity control. The person tirelessly promoted the TAD TH4003 as the ultimate solution for such setups. At that time I only knew the TH4003 horn from some pictures. But over the last years I have developed an eye for whether a horn profile meets certain requirements or not. That’s why I expressed my biggest concerns about the vertical pattern control of the TH4003. However, since I had no mesh file or STEP file of the TH4003 available at the time, no final assessment could be made. The discussion then more or less fizzled out. Some months later, a STEP file for TH4003. A few months later, a STEP file literally “fell off the back of a pssing truck” ;-), which gave me the opportunity to examine the horn more closely. I also remembered one of my first William Neile waveguides and the experiments with gentle diffraction slots and realized that I actually already had something much better in the drawer.

Continue reading

A Nice DIY Project Using my JMLC Inspired Horn Calculator

Recently, I got a request to help with some questions regarding the use of JMLC inspired Horn calculator. Usually, I have not much spare time to help in detail, but this time was indeed different because there was a well balance of give and take.

Adam contacted me with a very nice performance JMLC horn using PETF to optimize the profile with respect to better directivity control while greatly preserving loading. It is not as good as my WN300, but I was surprised about the results. With some minor suggestions from my side to further optimize PETF parameters, Adam worked almost without my help using his own workflow. It has been proven that my splines export function is working perfectly to create a step file and then mesh the BEM components using GmsH.

Continue reading