Polk Audio LSi7 loudspeaker
By Robert J. Reina   •   March, 2003 In my review of Polk Audio's RT25i loudspeaker (September 2001, Vol.24 No.9), I was mightily impressed with Matthew Polk's execution of this $320/pair design. Although it has since been replaced by the RT27i, with slightly modified cosmetics and a different tweeter, the RT25i remains my favorite loudspeaker costing less than $500/pair.

Since that review, I've often wondered how Polk might fare with a speaker at a higher price. I'd been very impressed with Polk's demonstrations of their flagship LSi line at the Home Entertainment 2001 and 2002 shows, so when I learned that the least expensive entry in that series, the $820/pair LSi7 bookshelf speaker, just scraped the $1000/pair ceiling of my self-imposed "affordable speaker" price bracket. I thought I'd give it a whirl.

Design
The Polk LSi7 is a two-way, ported, design. It has a 5?" woofer and a 1" ring-radiator tweeter, both magnetically shielded for use in home theaters. The mid/woofer is made of foamed polypropylene that includes tiny bubbles of air to better suppress cone resonances. There are two ports: one 1" in diameter positioned on the front baffle next to the offset tweeter; the other 2" in diameter and positioned on the rear of the speaker. This fires into a diffusor that allows the speaker to be positioned close to the wall behind it.

The tweeter appears similar to the drivers seen in recent models from Krell, Audio Physic, and Mission. Its ring-shaped diaphragm is supported at both its outer and inner circumferences, with the voice-coil positioned midway between the two. Such a mounting is said to push the first breakup-mode resonance beyond the upper limits of audibility. Two sets of binding posts are provided to allow biamping and biwiring.

The walls of the LSi7's enclosure are made of MDF and internally braced, and finished in high-gloss laminate. Two "cheeks" are attached to the enclosure's side panels to provide further damping; these can be veneered in ebony or cherrywood. I found the cherry veneer on my review samples understated but attractive.

Testing Methodology
I listened to the Polk LSi7s on Celestion Si stands, loaded with sand and lead shot, in both of my listening rooms. Polk recommends listening with the speakers' grilles removed, which I did, but I also tried them with the grilles on. Removing the grilles squeezed an extra iota of detail and transparency from the LSi7s while leaving their tonal balance unchanged; audiophiles who like the looks of the LSi7 with its grille on won't be missing much.

Finally, Polk's instructions recommend using the LSi7 with solid-state gear. Using tubed gear is not prohibited, but Polk feels the LSi7 "likes" solid-state. Although I did most of my listening using the Creek 5350SE integrated amplifier, I also tried the Polks with the Audio Valve Eklipse preamp and Audio Research VT100 Mk.II power amp. While the LSi7 proved an excellent match for the tubed ARC amp, I found no deterioration in performance with the solid-state Creek.

Sound
I immediately noticed four areas in which the LSi7's performance excelled:

1) Continuous and extended dynamic range on all types of music, from the softest passages to the loudest bombast. Although I've heard some affordable speakers that excelled at microdynamic resolution and others that had dramatic capabilities in high-level dynamics, this is the first affordable speaker I've heard that excelled at both.

2) Extraordinary retrieval of detail and ambience.

3) Pinpoint image specificity on a wide, deep soundstage.

4) Detailed, extended, airy, and natural high-frequency resolution.

Fans of jazz drummers should die for the LSi7. On Dexter Gordon's Go (LP, Blue Note BN ST84112), I found myself analyzing Billy Higgins' crisp, tuneful percussion as it emerged from the naturally ambient space, his organic and lively snare and hi-hat work demonstrating clearly why he's one of the jazz greats. Similarly, on Shelly Manne's solo on "I'm an Old Cowhand," from Sonny Rollins' Way Out West, (LP/CD, RCA/JVC VICJ 60088), I could tell how tightly the skins on Manne's snare and toms had been adjusted. On the Modern Jazz Quartet's Concorde (LP/CD, Prestige/JVCXR LP7002), I was captivated by the intimate interplay between Connie Kay's brushwork and John Lewis' subtle piano counterpoint. Best of all, Milt Jackson's vibes sounded pristine, sharp, and resonant, but completely natural. I've never heard a more realistic reproduction of the vibes from an affordable speaker.