The R645v3, and to a lesser extent, the R630v3 have been the focus of a huge amount of audio enthusiast attention in terms of modification and upgrading.
At least three companies, Sonic Craft, Madisound and North Creek offer crossover upgrades and Sonic Craft offers also BlackHole acoustic damping kits. The Coaxial Ribbon LineSource based models can also benefit from this kind of upgrade approach.
For the most part these speaker tweaks are going in the right direction. Newform cannot justify the cost of these modifications in a production loudspeaker where 10 to 15% of owners are motivated to make the upgrades. However, the use of higher quality capacitors, whether Hovland, Theta or Sonic Craft and foil inductors can only improve the sound quality. Improved damping along the lines of Blackhole or Blachford on the cabinet walls again, can only be an improvement to older models but keep in mind that the v3 models incorporate multilayer damping and panel damping.
Our only strong recommendation is that the tweakers keep the upgraded crossovers outside the enclosure. There are two reasons for this. One is to keep the large caps and inductors from restricting airflow inside the cabinet. The second is to facilitate easy changes to the values of the crossover components and to allow the "inevitable DSP crossover /biamp" upgrade to be installed easily.
To this end, Newform has developed an external terminal plate for mounting the crossover and allowing easy direct hookup of the "inevitable full digital chain". Plug and play!
The upgrades discussed on the web in numerous forums range from simple (the upgrade cap simply bypasses the internal unit so there is no need to go inside the cabinet) to almost a complete rebuild of the speaker. When you undertake the modification project, be sure you have the background to see it through.
In looking at the modifications you might be considering, always keep in your mind the possible upgrade path to digital crossovers. DSP crossovers and digital amps with built in crossovers are here now and they are becoming more common. Several receivers and preamp processors have both digital crossover and room correction built into them. This is an extremely potent combination.
Where you choose to jump in on these curves is your decision but choices are available now from Tact, Hypex, Lyngdorf, Emotiva, DEQX and Behringer. Onkyo now has digital crossovers built into some of its receivers. That plus room correction and the great sounding amplifier sections, make these Onkyos a bit of a killer ap. Call us for an update as this is a rapidly developing area.
In terms of ultimate tweaks, we have the No Holds Barred (NHB) models which address all of the upgrade issues and go several steps beyond in terms of advances in enclosure technology. As well, you can browse through the "Owners Projects" page to see some really well done individual approaches to solving the acoustic imperfections inherent in any loudspeaker design.