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A review of the Polk Audio LSi9 speakers

Polk re-writes the book on bookshelf speakers


Steve Kindig

Steve Kindig has been an electronics enthusiast for over 30 years. He has written extensively about home and car A/V gear for Crutchfield since 1985. Steve is also a volunteer DJ at community radio station WTJU, where he is a regular host of the American folk show "Atlantic Weekly," as well as the world music program "Radio Tropicale."

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Polk review The compact LSi9s are crammed with high-performance speaker technology.

Since being introduced in 2002, Polk Audio's LSi family of speakers has earned enthusiastic reviews from both audio journalists and consumers. I'd heard the LSi9 bookshelf monitors and LSi15 towers at industry shows and been very impressed by the speakers' relaxed musicality, and their ability to hold their own sonically when compared to much more expensive models. Since I've been using bookshelf monitors for years, when I was asked to do an LSi review, I chose to spend a month with the LSi9s.

At just under 15" tall and tipping the scales at 32 lbs. apiece, the LSi9 is a dense speaker that is also densely packed with clever engineering. It could be described as a "2-and-a-half-way" design — the two matching 5-1/4" mid/woofer drivers operate together below 200 Hz, but one rolls off above that point. Sitting between the two mid/woofers is the 1" Ring Radiator tweeter (made by Vifa), which is also found on other high-end speakers, some costing thousands more than these Polks. The two small ports on the front baffle aren't bass ports. Polk calls them "Acoustic Resonance Control" ports: they're tuned to different frequencies to help reduce sound-muddying cabinet resonances. There is also a bass-enhancing "Power Port" vent on the back side.

You can't see it in the photo above because the right speaker's grille is on, but the LSi9s come as a "mirror-imaged" pair. Notice that the tweeter isn't in a vertical line with the mid/woofers — it's offset a little. With mirror-imaged pairs, one speaker is designated as "right" and the other as "left." Polk's owner's manual recommends that the LSi9s be placed so that the tweeters are toward the speakers' inner edges. I tried them both ways — the recommended approach offered better image focus and more compelling sound overall, while having the tweeters toward the outside provided a slightly wider soundstage. Most of the time, I listened with the recommended placement.

speaker placement The way I positioned the LSi9s had a big impact on how they sounded. You can watch our speaker placement video to learn about the basics, or get full details in our articles on speaker placement for stereo or home theater setups.

A brief detour

A few years back, I did a lot of research on speaker placement for some of our learning content. One of the most eye-opening things I learned was how speaker placement affects the relationship between bass response and imaging. Generally, if you move a speaker nearer a "room boundary" such as a wall or the floor, you'll increase its bass output. Moving a speaker away from these boundaries reduces bass response but improves spaciousness and imaging. (In the last two houses I've lived in, I've been lucky enough to have a dedicated listening room in the basement, so I could set up my speakers for the best balance between bass response and imaging, without worrying about damaging the décor.)

Armed with this knowledge, the next time I shopped for speakers, I chose a configuration that avoided compromising either bass response or imaging. I bought the speaker system that I still own and enjoy today: a pair of Sapphire III bookshelf monitors and matching Titan powered subwoofer from Audio Concepts (ACI). I placed the Sapphires on stands well out into the room to optimize imaging, and after some experimentation, found a spot for the sub where it provided excellent extension while blending in seamlessly with the sound from the Sapphires.

The setup

I removed my usual Sapphire bookshelf speakers from the 24"-tall sand-filled speaker stands, and replaced them with the cherry-finish LSi9s. Another reason I was interested in the Polks is that, like the Sapphires, the LSi9s have dual sets of binding posts for biamping or biwiring. I've been biamping my speakers for years with excellent results.

Polk review Dual sets of binding posts permit biamping or biwiring. The LSi9s come with jumpers which connect the two sets of binding posts for regular use (left photo). For biamping or biwiring, simply remove the jumpers (right photo).

If you're not familiar with biamping, it means using four channels of amplification (either from a multichannel amp or two stereo amps) to drive a pair of speakers. Biamping provides each speaker driver with significantly more power, and typically results in greater dynamic range and lower distortion. I've been using a multichannel home theater amplifier — Carver's THX-certified AV-806x running in 4-channel mode — to drive stereo speakers. In this configuration, each speaker receives about 260 watts — 130 each to the mid/woofers and tweeter. You can read more about biamping in Dave's blog post.

Associated gear used in the review:

  • Adcom GFP-750 stereo preamp
  • Carver AV-806x multichannel amp (biamped configuration)
  • Onkyo DV-SP800 universal DVD/CD/SACD/DVD-Audio player
  • Panamax MAX 5500 line conditioner

The sound

High-quality speakers seldom sound their best right out of the box. They usually benefit from a "break-in" period of a few days to a few weeks. So, after connecting the Polks, I let them play non-stop for a few days, to get the drivers limbered up. (I also turned off my subwoofer because I wanted to start off hearing the LSi9s without any low-frequency assistance.)

Over the course of several sessions over the next few weeks, I listened mainly to CDs, but also played a few SACD and DVD-Audio tracks (stereo only, of course). From the get-go, the LSi9s sounded clean, dynamic, and exceptionally smooth. The sonic characteristic I value the most is imaging, and these compact Polks created a very believable 3-D soundstage with precise imaging. One other striking aspect was the bass response — the LSi9s had impressive low-frequency extension and impact.

For example, on Kathleen Edwards' terrific Failer CD, the song "Hockey Skates" has deep electric bass pulses that had startling presence through the LSi9s. These pulses didn't fill my room the way they do through my subwoofer (not surprising, considering its 12" driver and 250-watt amp), but to hear these deep sustained tones coming from the LSi9s was almost eerie — it just didn't seem possible that such taut and tuneful low frequencies could be coming from these bookshelf speakers.

The LSi9s' rated frequency response is 50-26,000 Hz (-3dB), but it sounded like they were going deeper. Their low-frequency output was so startling that I dug out a bass test CD to try to confirm what thought I was hearing. In my room (always a major factor) the LSi9s delivered solid output down to 40 Hz, and were still producing sound at 30 Hz! The LSi9s' bass was so potent, that I did virtually all of my listening without using my subwoofer.

You know a speaker is doing something right when you notice new details on familiar recordings, and that happened a lot with the LSi9s. On several of the songs on Failer, I could hear every time Kathleen Edwards drew a breath, and it made her singing seem that much more natural. In general, vocals — and especially female vocals — sounded spectacular through the Polks.

When I switched gears to the Donnas' Spend the Night, I wondered if the Polks might be a bit too smooth. On the CD's high-voltage opener, "It's on the Rocks," the LSi9s took a little of the stress and strain out of Donna A.'s vocals, which was welcome, but they also seemed to slightly tame the snarl of Donna R.'s electric guitar. The Ring Radiator tweeter has the remarkable ability to reveal loads of musical detail without ever seeming to shove it in your face. This helped the LSi9s be more forgiving of less-than-perfect recordings. A lot of CDs from the '80s sound uncomfortably harsh through my Sapphires, but the Polks made discs like David + David's Boomtown very enjoyable.

The Polks' presentation of music is what audiophiles refer to as "laid-back" — the soundstage starts behind the speakers. Overall, they had great front-to-back depth, though their soundstage wasn't as broad side-to-sde — it was generally confined to the space between the speakers. The Polks' sound also possessed outstanding rhythm and snap, accurately conveying the drive and energy in everything from bluegrass to Afropop. These speakers don't just sing, they swing!

Over the review period, the more I listened to the LSi9s, the more I liked them. It reminded me again that when you're buying speakers, whether at a retail store or online, it's essential to be able to listen to them in your room, and to be able to return them if the sound doesn't suit you.

Polk review Polk's LSi9s deliver very impressive performance for the money.


Polk's LSi9s are amazingly good speakers, and a tremendous value. To hear their full potential, you should drive them with either a high-quality receiver or a separate preamp/amp combination. Their smoothness, 3-D soundstaging, and startling bass output let you hear deep into the mix. It's obvious that they weren't simply designed using computer programs — someone did a lot of listening. Their clarity would make them a fine choice for home theater use as well, although you'd probably want to add a subwoofer to accurately reproduce the deep-bass frequencies which occur much more often in movie soundtracks than in music.

I still really love my Sapphires/Titan system, but the LSi9s provided stiff competition in several key areas, yet at $900/pair, are priced several hundred dollars less than current-model Sapphires. And for music listening, the LSi9s represent an even bigger bargain because their powerful bass response will satisfy many listeners without the addition of a subwoofer.