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
