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Jim Treanor

Some weeks ago, after listening extensively to my solid-state Conrad-Johnson MF2500 and my hybrid Alta Vista Audio NP100 (a Mike Elliott-modified Counterpoint SA-100) each drive my 1.6�s full-range, I concluded that bi-amping wasn�t in the cards for at least the time being, given the amps� sound quality differences and level-matching issues. I decided instead to upgrade the passive crossover and leave the 1.6 driving chores to the NP100.
I had enough Cardas binding posts, Symdex speaker cable (four individually-jacketed 22ga. solid-core copper wires in a twist configuration per run), and scrap plywood on hand to do the first-pass external enclosure, so all I had to acquire were the high-pass and shunt caps, the inductors, and�because I wanted quick cable interchange capability if I decided to go on a tweaky comparison binge�3/16� female disconnects to permit connection to the 1.6�s solder tabs.
Budget and an admitted bias (I don�t like ganged capacitor arrays because of the solder joints required and potential smearing issues) helped determine the choice of caps: Auricap 22mfd for the high-pass (sourced from SonicCraft) and Clarity SA 25mfd (a 630VDC physical monster available from Madisound) for the low-pass shunt. For the inductor--again, with budget in mind--I selected the Erse SuperQ 3.5mh 16-gauge iron core (source: Parts Express). A problematic choice, because its DCR is spec�d (at 0.2 ohms by Parts Express, 0.217 on the Erse website) at roughly half that of the stock 1.6 coil and posed a potential level-matching issue.
The Auricaps arrived first, quickly replaced the stock Solen array, and had about 50 hours� playing time on them before UPS delivered the Clarity SA�s. The SuperQ inductor arrived about a week after that. For listening evaluations (initially restricted to CD and SACD for convenience) I used a variety of symphonic, opera, choral, jazz, vocal, and film scores, among them: the Fiedler/Wild Gershwin (Living Stereo SACD), Paavo Jarvi�s Prokofiev Romeo and Juliet suites (Telarc SACD), Ashkenazy�s Rachmaninoff Symphonic Dances (London CD), Tchakarov conducting Borodin�s Prince Igor (Sony CD), Ormandy�s Orff Carmina Burana (Sony CD), Bernstein�s 1989 Candide (DG CD), Thelonious Monk�s 5 by Monk by 5 (Analogue Productions SACD), Dave Brubeck�s Time Out (Sony SACD), Sarah Vaughan�s Gershwin Live (Columbia CD), Mel Torme�s The London Sessions (Audio Fidelity SACD), Jerry Goldsmith�s Film Scores (Telarc SACD), James Horner�s Sneakers (Columbia CD), Mancini�s Greatest Hits (Telarc CD), and Jerry Goldsmith�s L.A. Confidential (Varese Sarabande CD).
With just the Auricaps as the only upgraded components in the otherwise stock XO�s, the presentation initially exhibited a tad more openness and breadth in the soundstage. As they burned in, intra-soundstage space began to expand and voice, strings, woodwinds, and brass acquired a more nuanced, fuller-bodied cast. As neolith indicates at http://db.audioasylum.com/cgi/m.mpl?forum=mug&n=98709&highlight=crossover+frequency
the 1.6�s high-pass cutoff (3db down) is 1600 Hz. I suspect that what I heard as a more transparent, more developed-midrange (160Hz to 1300Hz) reflects a better �teasing-out� of partials--overtones which may or may not be whole even- or odd-order harmonics of the fundamentals of the instruments producing them�rendering vocal and instrumental timbre more accurate. But that wasn�t the end of it. After about 80 Auricap break-in hours (I didn�t keep exact track, and the Clarity SA shunts had been in the circuit about 30 hours), the top end seemed to break out of a straitjacket, suffusing the presentation with more air, imparting a near-filigreed character to chimes and brushes on cymbals. With that, space expanded again, particularly on large-scale orchestral and choral works, with consequently more detailed and three-dimensional placement and layering and the unmasking of previously obscured venue ambient cues. Moral: Don�t judge a new cap on your first listen.
Does the low-pass shunt cap really make a difference? I�ve heard varying opinions on this, but I didn�t want to cheap out any more than I had to. And I�m glad I didn�t. Nor do I consider the $30 630VDC-rated 25mfd Clarity SA �fatty� overkill�certainly not after hearing the initial drum strike on the second track of the Goldsmith SACD after the SA had about 30 playing hours under its belt. With the MF2500 driving the 1.6�s, that drum strike would initiate a seismic-scale roll-up-the-concrete-floor delay. The less powerful (but in my estimation, more musically satisfying) NP100 pushed out the delay all the way to the listening chair, but not with the serial-thump impact of the 2500�not with the stock low-pass components in place, anyway. But with the Clarity SA (and the stock inductor), vibrational decay rolled up to the chair with a persuasive close-that-counts-in-horseshoes rumble.
I listened to the SA with the stock inductor for about 20 hours to get a feel for not only its bottom-end impact contribution but the overall tonal balance with the Auricap-Clarity combination in place. Then I replaced the stock inductor with the Erse SuperQ. And confirmed my suspicions about the lower DCR and how it might elevate the bass/mid panel�s response.
Bass impact? In spades. The NP100 was suddenly on steroids. With the Goldsmith, not only must the first drum strike have registered on a USGS seismograph 90 miles away, but the second as well. Same with the bass drum on the Horner Sneakers. But�
With bottom-end impact came a price I�m not willing to pay. The mids thickened. What had been nuanced transparency in voice and instrument was overlaid with a patina of chestiness that obscured timbre. Sarah Vaughan�s voice had an incredible range as it was, and she didn�t need the hormonal boost that renders throatiness subterranean. Moreover, male voice took on a near-shouty quality reminiscent of some mid-fi midrange horns I remember from long, long ago in a galaxy far, far away. The overall impression was that I was listening to a less-than-satisfactory mating of cones with panels.
The bottom line: The Auricaps and Clarity SA�s stay. So does the stock inductor for the time being, until I decide (and budget permits) whether to go Alpha-Core or the 10-gauge Solen Hepta-Litz air core with a DCR close to that of the stock unit. This isn�t a knock on the Erse. Rather, it�s a testament to the need to consider all the applicable parameters of a given component when you contemplate an upgrade.

Jim
http://www.geocities.com/jimtranr/index.html

Edits: 07/17/08 07/17/08 07/17/08

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