Editor’s Note: This product has been removed from our side-by-side comparison because it has been discontinued. You can still read our original review below, but Top Ten Reviews is no longer updating this product’s information.
Car subwoofers generally perform one of two purposes – they fill out the audio with crisp and clear low end or big and thunderous bass. The Polk DXi subwoofers are more in line with the latter. The audio is full and punchy but distorted. This makes the Polk DXi a great subwoofer for genres with heavy low end, like hip-hop, metal and punk rock. However, if you want to hear the bass notes clearly underneath the guitars, you'll be disappointed.
One of the downsides to the DXi subwoofers is the frequency response. The 12-inch subwoofer only reaches as low as 27Hz, and the 10-inch subwoofer only reaches as low as 28Hz. For comparison, the best car subwoofers we reviewed reach as low as 20Hz, which is the basement of human hearing. A lower frequency response produces a fuller, more present sound. If you were listening to a piano, the 27Hz response would barely handle the lowest key. Electronic music and hip-hop often reach lower.
Another downside is the comparatively inefficient woofer. With a sensitivity rating of 88dB, it's more efficient than many car subwoofers, but it still doesn't compare to the 96dB sensitivity of the best subwoofers, which are almost three times as efficient. The power handling is also low at 360 watts of continuous power with a peak of 720 watts. While you can still rattle your rearview mirror with this type of power, you have to feed the subwoofer much more power to match the output of the best subwoofers, which would cause damage to your woofer.
One of the best features of the Polk DXi subwoofers is the ideal size of the enclosures, which means you won't have to sacrifice much trunk space. While you can install the subwoofer to any size of enclosure that you want, the ideal size represents the cubic feet needed for optimal performance. The ideal sealed enclosure for the 12-inch subwoofer requires only .88 cubic feet, which is among the smallest of the optimal sealed enclosures. Since the woofer has to push against the surrounding atmosphere while the internal air pressure remains the same, this type of enclosure produces a cleaner, more accurate low end.
However, if you want the big and thunderous bass, the ported enclosure is ideal. The hole in the enclosure allows the woofer to move freely like a piston. This movement creates a more violent movement of air in front of the woofer and out the port, producing the big, punchy bass sound. This enclosure only requires 1.5 cubic feet for optimal audio reproduction.
Polk also offers excellent customer support features. Each Polk DXi subwoofer comes with a one-year warranty, but the best support feature is the Polk University section of the website. There are many articles and tutorials to help you learn how to get the best audio for your car.
The Polk DXi subwoofers are excellent if you prefer bigger low end over accurate low end. The frequency response bottoms out at 27Hz, which is equal to the lowest key of a piano. The 88dB sensitivity rating is well below the best car subwoofers, but higher than most subs.