Thiel Owners

Unsound - I like seeing you think outside the lines. Indeed that coax is a work of art that should find additional uses. To add some perspective, let me summarize Jim’s design process.

•The drivers are developed against their optimum criteria.•Each driver is measured thoroughly in an infinite baffle, and in the cabinet.•The cabinet including baffle shape, chamber parameters are optimized to align the driver to its infinite baffle state (as much as possible).•Driver anomalies such as resonances, enclosure effects, etc. are evaluated regarding which ones can benefit from electronic (shaping) circuitry.•Iterative process of driver changes (surround compliance, mass, etc.) with XO circuitry to bring each driver closest to its 6dB/octave slopes.•Continual comparisons of components, layout, etc. for optimization within the cost constraints.
It may be clear that changing a major element such as the driver, chamber size or baffle geometry for a different will have interactive effects on most of the design parameters. It was common for a speaker in development to get cabinet changes during development. It is likely that the new coax driver would have required different cabinet geometries, enclosure volumes, etc. to ’work’ as a colorless transducer at a level to satisfy Jim.
Indeed with much smaller changes such as replacing the original CS2.2 midrange with the ScanSpeak 10F, there are significant XO changes required because all the resonances and T/S parameters are different from the original. In steep-slope designs a driver can be ’dropped in’ because most of the anomalous behavior is in the extended overlap zones which are attenuated by the steep slopes. We don’t have that luxury.

Just my little peek behind the curtain regarding how everything is hooked to everything, nothing is simple, and no good idea goes unpunished.

@vair68robert
How would you characterize the sonics of the wool batt? And did you attempt to approximate the same volume as the ‘glas?

The wool quilting batting is very light ,
so I learned that it is to light and I ended up filling the back half
of the coaxial with the origninal fiber glass and the front with the wool I originally was using .
I changed because after installing the new wiring the sound was bright ,
and compressing the insulation and wool eliminated the brightness .
Using all wool the cost would become a factor ,
Maybe I'll try some bulk wool that is or can be more compressed ,
like the fiberglass .
I haven't used the wool in the bass or passive radiator chamber yet ,
but queen size quilting batting is on it's way .
I'm really enjoying the sound with the Cardas wiring ,
but I'm thinking about trying to reduce the gauge to the tweeters 
to see if that alone can or will affect the brightness .
I can't say about the sonics of wool ,
it's less itchy and healthier to handle .

 

Happy Friday! All

Rob - a word for the record about insulation. There's quite a bit to it.Common wisdom is that wood  is 'better' than glas, etc. , which I believe oversimplifies the situation considerably. The various materials act differently, so even at equal cost, specific application criteria apply. I ran extensive insulation comparisons at Thiel in the 80s. We landed at pure wool felt on the back wall of midrange enclosures - nothing else comes close to how well that acts in controlling reflections and so forth. In fact, we called the various engineered foams, batts, etc. "wishful engineering" due to their relatively poor performance. When it comes to filling cavities, polyester fiber-fill of various densities and fiberglas are the front runners. Wool has a bad habit of 'unloading' as frequency drops, which is contrary to what is often optimum. Polyester falls somewhere in the middle. Fiberglas has enough crooks and nodes to stand up to bass resonances without squirming. It outperforms the rest in my experience. That opinion is shared by some other designers of note.

Big problems with 'glas include irritating dust and a sharp hand. But wait! all 'glas' is not created equal. Thiel's 'glas is not builder's fiberglas insulation, it is a clean, graded product for industrial use. I got our fiberglas certified to our insurer's satisfaction.

If you want to compare different kinds of stuffing, I suggest measuring the outcome with REW, etc. to make sure you aren't  compromising performance. Your correct dose will depend on outcome, not on comparative density, mass or volume. Most of the non-'glas products are likely to unload the bass to produce a lower Q with less flat response. Some folks might like that. Jim's goals were toward flat, uncolored bass extension with a 0.7 damping factor, which he considered the ideal. Some folks might prefer a fuller, looser bass from other materials. Let us know what you learn.