Thiel Owners

Unsound, the chamber volume for the coax requires almost a doubling of the space that the 3.5 offers for the mid-range driver (using space measurement of the cavity of the 2.7 compared to 3.5). Most practical way would be an expansion of the chamber on the back of the speaker, using a cardboard tube and wood. The front bevel opening would need to be enlarged with an extra inch or so, for which there is enough room. The new coax drivers are about $550 each, not sure about shipping costs. Depending whether you have the tools and skills to do the woodwork, you can estimate your "investment".

Wow the level of expertise of Thiel DIY'ers is amazing .

Thank you @stspur for your impression of Mills resistors with them being your first upgrade .  
They are next on my list .

A correction about the wire used in the Tennessee CS2.7 ,
after replacing the wiring with Cardas 15.5 AWG 
I looked at the original wire using a 30X magnifying glass
and can now see the missing dot making a 16 and not an 18 AWG .

A lot of work replacing all the wiring , 
BUT I'd have to say it's worth it given the improvement I'm hearing .
Jimi Hendrix  "And the Gods Made Love"
never swirled with such detail before .
One more thing ,
I replaced the fiberglass batting with wool quilting batting . 

Rob

Just picked up a pair of 3.5s 2 days ago. Paid $275, but the cabinets are pretty beat up… delaminated veneer, minor moisture damage, scratches & broken grill frames. Also, pushed in tweeter domes & a small dent in one mid-range frame. Nevertheless, the drivers reportedly all work and sound great. We shall see.  

 

For me… this is the perfect purchase.  Beautifully engineered audiophile speakers, highly successful design, years of development by experts with audio skills that far exceed mine.  A great platform to work with.  Woodworking is no problem; but, I’ve got several projects I’m still working so this one will have to wait a bit.  Just starting research on these speakers and what may be my best approach.  IF I were jumping in right now with the limited research done.  I would look at:

ESOTAR T330D tweeters (a favorite of mine)

Scanspeak Illuminator 12MU/8731T-00, 4.5” Midrange

Vifa M25WO-35 6 ohm 10" original Woofer

Shelve the Bass Equalizer & add a 10” or 12” powered subwoofer to each speaker.  I like to build powered sealed downfire SWs into the bottom of the speaker. 

The Illuminator mid-range is interesting as it solves some of the problems experienced with the original.  SPLs a little higher, but it’s able to go lower (300Hz Xover no problem) and has 150W long term max power rating compared to around 50W with the original & 30W with the 10F.  It would take a lot to burn up the voice coils on these.  Appears to also be a little easier load on the amplifier and it reportedly sounds very good. But Oh-boy is it expensive & will require a bit more breathing room in the cabinet.

Driver Name    Fs   Diameter  Vas   2.83V/1m  Re   Freq/Res  Power Price  

SS12MU/8731T 66Hz  86mm   5.8L   87.2dB  5.9  100-10KHz  150W  $291

SS10F/8424G  90Hz    68mm   2.1L   86.6dB  5.8  150-12KHz   30W  $190

SS12W/8524G  52Hz   86mm   8.2L   85.8dB  5.7  150-12KHz   70W  $63

@thielrules, Thanks again. Excellent information. The price of the drivers doesn’t seem unreasonable. The required cabinet work might be more than I bargained for. Not to mention the crossover tweaking.
@sljhigb, the original 3.5’s  mid’s 50 Watt rating was an 8 Ohm minimum recommendation. It was capable of handling 500-600 Watts into it’s 4 Ohm load.

Hello rules - I suggest that the 3.7 chamber is probably larger than the 2.7 because the 3.7 XO frequency is lower than the 2.7 judging by the larger capacitor bank at the infeed of the 2.7.

Redesigning a speaker is a massive undertaking. Budget a man-year more or less depending on your knowledge, skills and hardware.