dtossan

speedmadness posted both stock and GRR circuits on Posted August 12. A search on the net came up with most values for the parts. I then created a spreadsheet to calculate for the upgrade xo circuit: the input impedance, and the split of power sent to the tweeter vs the bass driver over the freq range 20Hz to 20kHz. I then upgraded the xo on 1 spkr and compared to the stock spkr. I initially put a 3.9ohm series R at the input to the twitter xo. The twitter sounded lifeless. The spreadsheet confirmed tweeter was getting lower % of power above 5kHz compared to the stock circuit, and that a 1.5ohm would be a better value at which point the hi freq accentuation would be more or less tamed. But at this point, I had burnt the xo in for 200hrs and I really loved the highs. When Amir in AudioScienceReview said that the stock RP-600M freq resp "peaking above 10kHz will sound bright", John Atkinson (of Stereophile) commented #116 that wasn't his experience. And that "If the excess above 10kHz is small and the tweeter's dispersion is limited in this region (as they almost all are), then it can actually result in a neutral top-octave balance in all but small rooms. Brightness, I have found, tends to be due to too much energy between 5kHz and 10kHz." My own listening tests agree, and I loved the highs so much that I set the series R=0. There is a degree of elegance and organicness to not only the highs, but to the entire freq band with the upgrade xo. Choosing the ClarityCap CMR 2.5uF for the tweeter, bypassed by a Cornell Dubilier 940C 0.01uF 3000VDC bypass cap was probably most responsible for the mid and high freq improvement. The ClarityCap was chosen based on strong humblehomemadehifi ratings, plus a 25% sale at partsconnexion. Perhaps the Duelund DCA16GA tinned copper hookup wires also helped. I went with a slightly cheaper 3.3uF AuriCap XO for the woofer notch filter. The problem at this point was too much boominess from the cabinet. The 1.3mH 14awg Solen Hepta Litz inductors probably contributed to that. The bass was getting prodigious. That's when I implemented the constrained layer damped cross brace - an idea I borrowed from KEF's LS/50 White Paper. A stunning discovery. Correction: My previous pics mislabeled my spkrs as RP-160M. In fact my Klipsch are the RP-600M. Pics have been corrected.

Klipsch RP-600M Upgrade Encouraged by speedmadness and various comments about the GR Research upgrade, I did the following: 1. More or less use a circuit like GRR. 2. Replaced wires with Duelund tinned copper hookup wires. 3. Built a cross brace employing Constrained Layer Damping. 4. Glued the xo parts to a hardwood plywood flooring board using Goop. 5. Wrapped tweeter caps with QuietPutty. 6. Attached xo board to base of cabinet using Butyl tape to form another constrained layer damping. The results are stunning - sounds like an entirely different spkrs. Before, I thought the RP-600M was nice for the price, but not great. Having been in the hobby and also tracked Stereophile for a few decades, I think their C ranking of these sprks is fair. The striking characters are their aliveness which makes for listening to Jazz and classical enjoyable in a not-large room. They are relatively not shouty like horns sometimes tend to be. But missing a degree of elegance, refinement and realness (which I admit normally come at a much higher price.) But I must say I'm blown away by the SQ after the upgrades and after a couple hundred hours of burn-in. Not only is the tone so much more organic and real (I have season subscriptions to symphonies and jazz performances, until Covid) - but there is a much more enveloping sense of the density of the soundstage. High hats, brushes and drum snaps are captivating. Voices and reeds are enchanting. Bass notes are much more emotional. Not as accurate and neutral as my KEF LS/50 or as massive or as real a sound stage as my highly upgraded Magnepan 1.7. But totally enjoyable nonthelsss. Now, watching movies are also breathtaking. I had my doubts about spending this money (~USD180) on such a spkr. But I am totally surprised by how the upgraded Klipsches have transformed into a jewel of my 2nd system (in my office). I look forward to listening to them all the time! A few pics: