Thiel Owners

Correction: I have read that the SS2.2 was introduced when Kathy was still president, so it would be an update of Jim's design. The conversation and questions I am remembering must have come later in the game.

Speaking of boundary compensation (that is correction for SBIR --- Speaker Boundary Interference Response), Thiel smart subs have SBIR correction to compensate for reflections off the front and side walls, but not the rear wall (behind the listener). It turned out I had a major rear-wall SBIR problem that could not be fixed by adding forward facing subs along or near the front wall of any size or quantity. The only cure was a sizeable array of *tuned* bass traps on the rear wall, tuned in my case around 50 Hz (where regular bass traps have very little effect). The key diagnostic for rear-wall SBIR is that the drop-out frequency shifts with distance from the listening position to the rear wall, but not with sub placement along the front wall. Once that problem was fixed, I did go with a 2-sub solution that works very well.

The distance from the LP to the rear wall gives you the quarter-wavelength of the SBIR dropout. From that you can find the dropout’s center frequency. If that frequency is well above your bass range, you can feel safe that you don’t have a rear-wall SBIR problem.

My room dimensions are roughly 15’ (front wall width) by 22’ x 8’3". I wish I had higher ceilings, but otherwise the room sounds great –– after treatment for early reflections, general bass control, and the aforementioned tuned bass traps for SBIR.

I strongly agree with other posters that emphasize the importance of getting your room’s bass response under control before going too far with adding subs. If your bass reverberation times are too long, adding more bass is likely to seriously degrade your sound.

....

I’m likely the guy with the Thiel SI-1 active crossover that @tomthiel mentioned. Although the passive PXO crossovers also do a fine job blending subs with mains, active crossovers also relieve the mains from reproducing low bass. This audibly improves the sound of my 3.7s (for a number of physical reasons): sweeter highs and plays louder w/o distortion. I was looking at Marchand active crossovers just before my SI-1 came up for sale. I wanted a crossover with balanced circuitry, and one of the Marchand variants was the only one I could find, other than the SI-1, that had this feature. In principle, a properly configured Marchand X-over should bring similar benefits, but the SI-1 was designed by Jim Thiel to make configuration a snap, even for non-experts.

@warjarrett, I'm envious of your potential setup! I'm confident that such a configuration will compete with systems that cost multiplies of your proposed Thiel system.
I'm not trying to tell you what to do or how to decorate,  but...,there is a strong argument to be made for using even more than 2 subs. Using even more multiple smaller subs to even out room induced anomalies that particularly effect bass response, might be more effective than a couple of larger subs. DSP can also be quite helpful with bass peaks though much less so with nulls. Of course vertical space loss might be less intrusive than extra footprint room space loss. Not to mention the extra cabling required. With so much invested in bass response, one has to wonder if the 3.7's could be modified for sealed bass response? Perhaps replacing the passive radiator with another woofer and appropriate cross-over to compensate for differing proximities to the floor and the variables that brings.

What ever you decide, I wish you the best of luck and do hope your report back on your decisions and results. I'm sure many here share my envious curiosity.



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Does anyone have information about the 02A floor standers. I have a pair and had the mids rebuilt. I finally convinced my wife that we should "test" them out in our main listening/living room. Now, she won't stop listening to them and the pretty newish non-Thiel speakers that had been in that room are relegated to my home office.

I am trying to see about having the crossovers rebuilt. Also, they have the black built-in pedestal stands where the terminals are located, which are made of MDF and have absorbed moisture over the years. Any tips on getting replacement pedestals is greatly appreciated. 

Thanks all.

@robrink, You might want to start here:

https://www.coherentsourceservice.com/