AFAIK, All Ren 90's come standard with a 0.5R resistor in series with the EMIT and 2x 0.5R resistors in series (1R) at the input to the tweeter crossover. The tweeter crossover is identical to that (same values) used in the Sigma / Epsilon but the latter drive 2x EMITs in series. The crossover values are actually optimised for 8 ohms, not 4 ohms and the response exhibits a pronounced peak at 4kHz followed by a saddle at 5-7 kHz before rising above 10kHz. My guess is that this gives a reasonably flat response at 30 degress off axis, although I've not performed measurements to confirm.
The other point to note about the Ren's is that the EMIM crossover is not quite as well optimised as it in the Sigma or Epsilon, thus allowing scope for considerdable improvement which means a flatter response and a less demanding load on the amplifier driving it.
With a few value changes and component upgardes plus fitting of a fabric acoustic disperser to the EMIT, it's possible to gain a ginat lift in accuracy and purity.
The other point to note about the Ren's is that the EMIM crossover is not quite as well optimised as it in the Sigma or Epsilon, thus allowing scope for considerdable improvement which means a flatter response and a less demanding load on the amplifier driving it.
With a few value changes and component upgardes plus fitting of a fabric acoustic disperser to the EMIT, it's possible to gain a ginat lift in accuracy and purity.