Thiel Owners

Tomthiel wrote:
"Just a thought. I suggest running the 3.5s wide open with no EQ. I remember the bass loading as critically damped, so it should approximate 12dB / octave. (But that's old memory) If you can match that rollout with a sub, the sub HF will operate in the directionality range, so 2 subs is better than 1. I for one am most in your progress."

Now we have here a subject very dear to my heart and experience. Both my Thiel O3a and CS3.5 had equalizers. I found the O3a to sound much better with a subwoofer crossed over EXACTLY  to the same curve as the EQ,  with no filter to the main speakers at all 

 The CS3.5's equalizer was a gigantic improvement, which I found to sound just as good as no eq at all. Never-the-less, there is the original Stereophile test still on the internet, which shows its EQ curve. Take out the equalizer, add one or two subwoofers, adjust their crossover frequency and slope to match that curve, and run the main Theils with no filter at all. This purist approach works and sounds like a charm. The 10"  woofers and main power amp are no longer taxed, so theoretically, distortion should be much less, and power handling much better.

Add a Classe DR8, DR9, DR-10 or DR-100 amplifier, and all is perfect in this world.

Great posts. Just got lost with this statement. Not sure if there is a typo:
The CS3.5's equalizer was a gigantic improvement, which I found to sound just as good as no eq at all.

Rules - by "just as good", I believe Warren refers to sound quality. See this audiogon thread regarding some pros and cons.
https://forum.audiogon.com/discussions/thiel-3-5-equalizer-advice
Even if the Thiel EQ or Golden Flutes alternative were completely sonically transparent, we are left with the problem of extreme woofer and lower midrange excursion which introduces various distortions including Doppler Shift and large excursion non-linearities.

No matter where you land on this controversy, it certainly represents a major historical shift away from low-order, sealed bass tuning to higher-order, ported tuning with the passive radiator. Originally Thiel speakers were going to use ports and passives in the 1 and 2 series, and equalizers and/or active woofer or subwoofers in the 3 and higher series. Jim struggled with the issue, felt some resentment with what sometimes seemed un or thinly founded critique and lack of appreciation for what the EQ brought to the table.

I personally felt that the passive radiators in the upper models, even though superbly executed, gave up a unique signature bass performance. A matter of history interjects itself: in the 70 and 80 there was less knowledge and willingness to solve room resonance issues. The speakers were often blamed for room problems, since they went so powerfully deep.

Warren - As you know, I consider the 03, 03a, CS3 and CS3.5 to be cognitively the same design. As such, as replacement drivers and solutions are developed for the 3.5, they will be applicable to the other models in the early 3 series. By the way, I believe those early 3 cabinets were the quietest that Thiel ever produced and, with some added bracing and SoftLaunch baffle tweaking, can be brought nicely into the 21st century. The grille frames suck more than I realized at the time. They're getting attention. Also, the modern grille fabric seems better than nothing and does not alter the frequency response appreciably if at all.

thielrules wrote:
"Great posts. Just got lost with this statement. Not sure if there is a typo:
The CS3.5's equalizer was a gigantic improvement, which I found to sound just as good as no eq at all."
I meant to communicate that the CS3.5's equalizer was a gigantic sonic improvement over the O3a equalizer. Throwing away the O3a eq, and replacing it with subwoofers very much improved the sound of the O3a. But the CS3.5 crossover was so good, that using it didn't degrade the sound to my ears at all. So using it was "just as good" as not using it, in every sonic way except the obvious loss in low bass. And, except for power handling. So, for medium listening levels, I found no sonic reason to stop using the 3.5 equalizer. As Tom points out though, theoretically, using a subwoofer instead of the CS3.5 eq did have benefits to woofer excursion when playing louder. And when CDs came into being, playing louder became a problem for CS3.5 in many ways, not only the woofer excursion. Midranges and tweeters started to become over-driven too. In 20+ years of playing only records in a small bedroom through the CS3.5, I never had a problem. But when I started to use them again after 10 years of storage, well, then I was playing CDs too, and I had a much bigger room, so I burned out the midranges and noticed over-taxing the woofers.