Thiel Owners

devin - Replacing like with like components is certainly the safest. Many folks underestimate the intricate co-dependence of all the elements. Even layout changes affect the subtle outcomes. Keeping values at original levels is a good start, but various parasitics also matter. The frequency response is rarely changed in significant ways; but time/phase generally is.

You may remember the maddening months to years delays between Thiel product announcements, or even live displays, and their actual release. Most of that time was tweaking, mostly in realms more subtle than most designers would pay attention to.

In our DIY / rework world, the largest trap that I’ve found is subbing foil for the original wire inductors. Foil is indeed a more pure inductor, but its parasitics are so different from wire that considerable xo tweaks would be required to re-settle the circuits.

The safest bet is subbing in Mills MRA resistors for Thiel stock. Another safe and surprisingly effective tweak is replacing any electrolytic cap with 2 x half-value cap. The ESR and other anomalies are reduced by half, plus if you turn one cap backwards, end for end, other anomalies are cancelled. If there is a bypass cap (like Thiel’s yellow 1uF), that can be stacked to make a triangle for a single field.

Replacing caps, especially larger values is quite costly and sometimes demands circuit tweaks. It’s not hard to throw as much cost into upgrades as the entire production budget of the original speaker. Not for the faint of heart.

TT

Another safe and surprisingly effective tweak is replacing any electrolytic cap with 2 x half-value caps. The ESR and other anomalies are reduced by half, plus if you turn one cap backwards, end for end, other anomalies are cancelled.

tomthiel

Interesting, I think this is the first time I hear this. To make sure I understand, you are recommending replacing, say, one 100uF bipolar with two // 50uF bipolars, correct? So, when you say "turn one cap backwards" do you mean just physically, as in making sure the writings on the caps run in opposite directions? Since both caps are non-polarized anyway.

As far as cancelling anomalies, is that because bipolar caps are internally non-symmetrical?

I had to // caps in my rebuild because original values were unavailable. The pairs are not equal in value, but close enough that hopefully the smaller ones don't act as bypass. Also, I never thought of swapping ends because I hadn't read this post yet

Thank you again for sharing your knowledge.

devinplombier

Out of curiosity what capacitor values were not available, and what manufacture capacitors are you using ?  

vair68robert

12.5uF. Replaced with 8+4.7uF house-brand caps from Parts Express. Similar quality level as OEM as far as I can tell.

I did upgrade severely heat-damaged 10% sandcast resistors (one was open) with 1% wirewounds and bumped power dissipation from 10W to 20W and 25W to 40W respectively.

How resistors got that hot in a speaker crossover of all places is not something I can claim to understand, seeing that drivers appear original and in quite good shape without evidence of having been grossly overdriven in the past.

Devin - Thiel crossover schematics state the max tolerance of each cap. Some are 5%, some 10%. Among the strategies, I prefer to try for close to equal values when splitting. I've learned end-reversal via trials. E-caps are fundamentally symmetrical, but in fact the small differences, including lead-wire directionality, are audible and supported in the measurements. Music signal is AC, so optimizing for either direction produces mixed results; splitting directionality is always superior. 

By the way, Thiel's long-term cap brand was Solen. Their house sound is somewhat dark and smooth. We later went to ERSE for a more neutral, open signature. When they became unavailable, M.D.L (Taiwan) was chosen. and the final FST (China) cap was CYC. I use M.D.L from Madisound for classic late-Thiel signature.

My new layouts honor propagation waveform integrity. When splitting any cap, build a bundle that makes sense. If 3 caps, I build a triangle separated by cork pads, with the 1uF bypass in the middle of the bottom row. Air circulates through the whole stack. A unified field is floated around the 4 cap bundle. Trials prove this arrangement superior to other layouts. By the way in series feeds, the yellow 1uF Thiel bypass cap is replaced with our new multi-sectioned cap with multiple coaxial windings that start around 0.015uF and add up to the target value. Those will be available in 2025.