Thiel Owners

@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.

Thanks for all the information you share here, Tom!

Just to get on the right side of Thiele & Small, the term "critically damped" refers to a total system Q of .5, and "maximally flat" refers to the more commonly used .707 Butterworth configuration, which is slightly underdamped and is tuned to use a 3db hump in the bass response to lower the -3db point.

Thanks Unsound, your thinking makes sense to me.

Re bright Thiels, it was the one thing I didn't like when I first got my 2.3s, but it can be tamed.  For me it meant that each and every upgrade/improvement had address this, and room treatment amd arrangement (rack to the side wall), careful speaker placement (including height), speaker cables (AZ Holograph, thanks Eric Squires!), and Isoacoustic GAIAs all helped in different ways, the clincher was upgrading the digital source (went with bel canto 3.7).  All the while I was rolling tubes, and one thing I have learned to appreciate is being able to hear most (not all) of these little changes.  One reason I went for Thiels in the first place as a newbie audiophile was bc of their reputation to be very revealing of the signal, as TT mentions above.  I knew I'd be cycling through equipment cables etc and wanted good chances to be able to hear the differences.  Thiels have delivered!

You are correct - I didn't cross-check my rusty memory. The CS3.5 bass in its enclosure is 'critically damped' Q.5 for no bass hump, which some critics consider 'dry' or over-damped.

Also my apologies for my final statement of 'excellent in every way'. I meant that the bass configuration was optimized for performance in the phase, time and frequency domains. In particular the EQ'd sealed bass keeps the fundamentals in time with the upper harmonics, whereas reflex bass places the (reflex-supported) fundamentals a full cycle behind the rest of the signal. Lots of controversy around whether such bass coherence can be heard or matters. I'm among those who say it does 'to me'.

^I too have often (perhaps too often) gone on record record here on my strong preference for sealed boxes, not only for bass output, but for overall coherence as well.