Robert - I know a little about those add-on filters. I spoke with the maker, who would only say that he is fixing known problems with the 3.7 upper frequencies, as well as with Rob at CSS, and we ran a cost thumbnail. The Stereophile review near-field response shows a rough rising high end and the undamped oil-can tweeter resonance. Jim let that ring due to its out of band frequency and that the required notch filter imparts a veil on the whole sound. The low-treble roughness is, in my opinion, in the time domain and primarily an artifact of near-field measurement. In other words, it will not be fixed by more XO circuitry which modifies the frequency domain. Note also Stereophile’s averaged listener-position graphs, which show no hint of that alleged roughness.
Rob and I looked at the parts vs retail selling price and determined that those parts, if of Thiel quality, would cost more than his asking price for the assembled unit. So, he is inserting coils, caps, resistors and wire of lower quality, which quite probably reduces global transparency.
Neither I myself, nor Rob to my knowledge, has heard the mod. Plus, he may be doing more or differently than what I’m saying. It would be instructive to hear direct experience. But at this point we would not recommend it.
Rob and I looked at the parts vs retail selling price and determined that those parts, if of Thiel quality, would cost more than his asking price for the assembled unit. So, he is inserting coils, caps, resistors and wire of lower quality, which quite probably reduces global transparency.
Neither I myself, nor Rob to my knowledge, has heard the mod. Plus, he may be doing more or differently than what I’m saying. It would be instructive to hear direct experience. But at this point we would not recommend it.