Proac R2 Crossover Mod


Back to Tobes' Links

After playing about with numerous system 'tweaks', I thought I'd take a look at possible component upgrades for my speakers. A peek inside the box revealed that the ties holding the inductors were loose, likewise the nuts holding the (cheap automotive style) connectors to the binding posts. The stranded (QED Audio) copper cable was showing signs of oxidation. For those interested, here is the circuit schematic.

Below is the original crossover and drivers:
Original Proac Xover & Drivers

I decided to rebuild the crossovers with upgraded components and cable.
Since I was using the Goertz MI2(bi-wire) as speaker cable, I thought I would use this internally as well. This cable can be fairly inflexible to work with but its wide surface provides convenient solder pads.
After searching and posting some questions at the Tweakers Asylum I decided on replacing the existing Solen caps with Hovland Musicaps and using a power film resistor in place of the standard wire-wound type (all values as original). The original inductors were retained.

Here are the finished crossovers:
New Crossovers

Bass and treble circuits are on separate boards - so I could shoehorn the new crossover through the woofer cutout - and screwed to the backwall with some 'Blutack' in between.
The binding posts in the boxes are positioned right behind the bass port making soldering very tricky. I decided to retain the 'bolt on' connection(for the moment). Use of the Goertz cable eliminated the need for connectors, I used a paper punch to make holes in the ribbon cable.
Note: the 4.7uF cap was replaced with 4uF and .68uF caps - Wilmslow Audio, were out of 4.7uF caps but supplied the aforementioned at the same price.
The heatsink on the film resistor is overkill (dissipates 20W!) - I should have looked closer at the catalog but what the heck.
Here is the new crossover mounted in the box:
New Xover in Cabinet


Sound

I've had an opportunity to compare my modded Proacs with a friends stock factory pair - a slightly later build, but still the front ported version. The sound of the two share more similarities than differences. Nevertheless the modded pair had an edge in clarity and transparency from the upper-mids to the highs that was quite worthwhile IMO. The stock pair were a bit 'gray' sounding by comparison. My friend also thought the bass was a bit more heft through my modded pair.
However both communicated the music with the typical R2 verve.

Postscript 

I suggest that any R2 owner thinking of changes, firstly check for connection tightness to the binding posts (inside the cabinet) and loose components on the crossover boards. Also, be sure the drivers are firmly bolted down - don't get silly though, you'll break something.
Then, instead of the wholesale rebuild I did, perhaps try replacing just the tweeter caps and see what that gets you. Because of their size, the Hovland caps I used aren't really convenient replacements if retaining the stock crossover boards, so perhaps something like Auricap or Ansar might be worth trying.

Back to Tobes' Links