On the market since 2001, Polk's LS Series Loudspeakers have given the company a well-regarded position within the affordable, high performance loudspeaker market. The series provides two floorstanding models (the LSi25 and LSi15), two bookshelf models (the LSi9 and LSi7), a center speaker (the LSiC), and a surround/rear speaker (the LSiF/X).
The two-way LSi7 utilizes two Dynamic Balance drivers, a 1 inch ring radiator tweeter with a 5 ¼ inch polypropylene woofer, crossed over at 2.4 kHz with a 18db high pass filter, and a 12db low-pass filter. Developed in conjunction with Johns Hopkins University, Dynamic Balance resulted from a laser interferometry research project that enables Polk to analyze the entire surface of a vibrating driver in real time, in order to determine the right combination of materials for the particular product. Features such as an ultra-light woven diaphragm, custom copper-clad aluminum voice coil, copper Faraday Cap, and custom waveguides and magnets make this amongst the most ambitious drivers the company has made.
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The LSi7 employs two ports, a 1 inch on the front next to the tweeter, and a 2 inch on the rear, which doubles as a wall mounting bracket. The LSi7 offers dual 5-way binding posts for easy bi-wiring or bi-amping. The LSi7 offers two side panel veneer finishes to complement its gloss black baffle: ebony and cherry. The LSi7 offers an excellent level of fit and finish, and an elegant look with or without the grills.
The hefty, 21 pound LSi7s present a nominal 4 ohm load with an 88db efficiency, and this translated into a fairly heavy load to drive. Not challenging, but not one where the user couldn't slide by with just any amplifier or receiver, either. The sound demonstrably improved as the quality of power improved. The LSi7 presented a wide, deep soundstage with high quality imaging, and sparkling dynamics. These qualities were evident regardless of material, from classical to jazz to rock, and had many similar aspects to impressions I've had about loudspeakers costing many times more. The LSi7 had an excellent ability to present the music spatially, and re-create the musical environment.
Getting into specific tonal aspects, as with all "budget" loudspeakers and especially those with ported designs, things get a little inconsistent. I found the highs simply incredible, smooth and detailed, and the low bass extended and tight, but the midrange and midbass a little colored depending on the material. Not a surprise, as once you get into the soft areas of the crossover points and the bass reflex configuration, certain sound qualities always emerge (sometimes even in very expensive speakers) that stick out more within the whole sonic palette. In the LSi7's case, the sound was pretty consistent from the midrange on up to the spectacular highs, but from the midrange down to the midbass it would get a little muddy or even a little forward depending on the material and the volume, but also just right in many situations, especially with acoustic instrumental material. The low bass was excellent, tight and extended, and world-class for a bookshelf speaker at its price.
In sum, the LSi7 produces world-class highs and lows, dynamics and soundstaging, with a good midband that could drift towards excellent or average depending on the material. Given Polk's traditional midrange-oriented philosophy, of course, these sonic impressions offer more than just a hint of irony.
Read about the high points and the low points of the Polk LSi7.