Thiel Owners

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big_greg -I agree with Cascadesphil that Thiel’s can be more sensitive to input signal than most brands. In my opinion, that has more to do with their coherence allowing the ear-brain more scrutiny. But that discussion is beyond the scope of this response. Let’s assume that your signal is fine.

You stated your listening distance as 9’, which is fine. Design distance is 10’, and the closer you get, the more critical your ear height becomes. The propagation triangles have to resolve at your ear. Design ear height is 3’. If you sit high, you will get a treble-heavy and non-time-aligned wavefront. That’s a design constraint of phase coherence with multiple drivers and why Thiel gravitated toward coax treble sources in later models - with their own issues and challenges.

Another critical factor is early reflections, which likewise become more critical in a coherent design. The speakers are designed as point sources with very broad, even dispersion characteristics. As such they require at least 3’ between the tweeter and any reflective surface. Side-wall reflection is most often a culprit; absorption at the reflection point helps - a lot. Similarly, a low ceiling and/or hard floor can be problematic. In a small room, consider a long-wall layout.

Note that Thiel’s tonal balance is tuned for listening off-axis. At design setup the ear is 20° off-axis which is where the power (in-room) response matches the direct response. That straight-ahead position requires at least 3’ to a side wall, more is better, and absorption helps. In my experience most people aim them slightly inward to mitigate side-wall reflections. My experience is that straight-ahead with narrower speaker to speaker placement solves the issues better. Such particulars of setup are far more germane to performance than are particulars of equipment (unless grossly inappropriate.)

Thiels are articulate and precise, and for those who appreciate that, they can be very musically engaging. Many speakers are designed to be forgiving of problems - Thiels are not. Our goal is to faithfully reproduce their input signal - unvarnished. Much like a recording environment must be carefully optimized to capture a proper record of the recorded event, the playback environment must also be optimized. In the hi-fi hobby I believe we could create far more satisfying musical immersion by working on our environment and setup rather than looking to gear changes.

Keep the faith - the results can be wonderful.

I saw the recent references to the 03/03a Thiels, and had a question.  I have a pair of 03a speakers, which came to me without the equalizer.  My understanding is that they only provide a bass boost to lower the -3db point.  Would anyone know what the unequalized vs equalized response curves looked like?  Or at least the -3db points.  Did the equalizer return to flat at still lower frequencies (relying on the natural 12db/octave rolloff), or did it add additional rolloff at 6 or 12db/octave?

Also, I've seen the crossover schematic with the op amps.  Are there any hotrodded versions of the 03a equalizer?

@tomthiel Thank you for your recommendations. My ear level is about 36". My room has a lot of limitations, but has a fair amount of absorption and diffusion. There is an equipment rack between the speakers. 

I really like the 3.6s, but I need to love them to keep them. Rob at Coherent Source Service gave me a couple of things to check out to make sure they are functioning properly.

If they are, they may just not be a good match for my system and room. 

@petaluman - the 03a was a sealed box design which produces a 12dB/octave bass rolloff. I think the tuning was .707 Q which Jim considered critically (properly) damped and some call overdamped. I don’t remember the unequalized -3dB point, but a fit curve could be overlaid knowing that the EQ curve was 12db/octave with the peak centered at 30Hz and then reducing symmetrically to zero boost. I would guess the upper blend point would be around 100Hz. So, without the EQ, your bass will roll off at 12dB/octave below that blend frequency. With the EQ, you get critically damped flat response to 30Hz, then rolling off at around second order. Excellent bass. The EQ did not add cut, it merely ceased adding boost.

The Thiel eq was discrete circuitry and neither the EQ or any Crossover had op amps. However there was an aftermarket product called "Golden Flute" built in a brass tube and powered by a wall wart which used op amps to achieve the same goal. I have heard that they were well liked and successful; but I know nothing about their particulars.

I know of no hot-rodded versions of the 03a EQ. I do know that the CS3 EQ, which performs the identical function, was more sophisticated in its circuitry and execution. And that the subsequent CS3.5 was the first generation to be direct-coupled with no capacitors in the signal path. The 3.5 had variable cutoff points at 20Hz and 40Hz to side-step troublesome deep bass room modes if necessary. The 03a and CS3 families are conceptually the same product - with the addition of the Coherent Source nameplate. Even though the woofers are different, their Thiele/Small parameters and enclosure size are very similar. An EQ for the 03a, CS3 or CS3.5 would work for your 03a as would Golden Flutes for any of those same models. The 01/ 01a/ 01b also has the same 30Hz x 12dB boost and would work. Avoid the model 03 EQ, since that was both ported and boosted, so its parameters are different. I am working on a 3.5 EQ upgrade for significantly better performance than stock.

The EQ transforms the speaker from significantly bass shy to excellent in every way.