Thiel Owners

I thought this might be of some interest to followers of this thread, though this paper is nearly 10 years old, it just recently came to my attention:

https://www.keele-omholt-technologies.com/papers/Keele-CBT-Paper-08-Oct.-2015-Time-Phase-Behavior-of-CBT-Arrays.pdf

for those that want to take a deeper dive into the subject:

https://www.keele-omholt-technologies.com/papers.php

more discussion:

https://www.audiosciencereview.com/forum/index.php?threads/constant-beamwidth-transducer-cbt-speakers.12060/

Greetings Thiel fans, I wanted to update you on a modification that i made (with the great help of my friend Bob M. who did most of the leg work on this). This was inspired by a suggestion that Rob Gillum had made to us in putting some three ohm resistors in front of the mid and tweeter in the 3.7’s.

Rather than add one three ohm resistor we put two parallel going to both mid and tweeter. This would reduce the nominal impedance by 1.5 since they were in parallel. The result was a easier to listen to top end with a bit more naturalness to it. Rob gave us the idea and Bob did some digging and came up with the idea of running them in parallel rather than Use a 1.5 resistor. of course YMMV. this is what we added and it took 8 total. Dayton Audio DPR10-3.0 3 Ohm 10 Watt Precision 1% Audio Grade Resistor. Parts Express.

I would not do this unless i was pretty proficient with a soldering gun.  i would use solid silver and it takes two to make it doable,  one to hold the driver and one to solder.  when using the resistors in parallel,  be sure to twist them together. 

@ronkent 

What did you mean by "solid silver"? Did you actually mean solder containing silver?

ronkent - Regarding your mod. Be aware that the 3.7 mod that Rob suggested applies to only some speakers, not all. There was a QC problem with FST that required Thiel to test and characterize all incoming 3.7 coaxes and apply padding resistors as needed to bring the amplitude to standard. There were also harmonic distortion problems, which were failed and rebuilt in-house. When reworking drivers, CSS would add the resistors directly to the input terminals, or as in this case specify where to put them in the crossover.

Later, the coaxes were built to proper spec and noted with black trim rings. The 3.7 has an octave-to-octave balance within ± 0.5dB. So, you don’t want to pad it down unless it is out of spec, which is possible.

Note also that the mod as described here (padding both mid and tweeter) would effectively raise the woofer level a couple of dB. Moving the speaker closer to a boundary wall should accomplish the same thing. Also, any perceived brightness could be caused by harmonic distortion rather than simple excess amplitude. In that case padding down would reduce the gross amount of distorted output, but not cure the cause.

Roxy54 - for the record, with the 1987 CS3.5 we converted from 60/40 solder to silver solder for all our speakers. Our choice was the aerospace standard Alpha SAC-305 which is 96.5% tin, 3% silver, and 0.5% copper. It is not only permanent, but is technically superior. The improvements are audible. It requires higher melting temperature, but achievable with a 140 watt soldering gun.