Short answer: the Infinity IL10. It ranks #59 of 100 bookshelf speakers by sound quality at $160; the Polk Monitor XT20 ranks #65 and costs $279, so there is not much of a tradeoff to weigh.
What the Infinity IL10 offers: Impressively flat for a budget bookshelf. Watch for: Resonances at 600 and 5khz, which show up as distinct distortion spikes at 96dB SPL/1m in the same frequency regions.
On the Polk Monitor XT20 side: Two-way bookshelf design with a 1” tweeter and 6.5” woofer, part of Polk’s budget-friendly XT lineup (spanning roughly $200-700 across the series). Set against that: Notably bright treble, elevated roughly 1-5dB above the midrange depending on frequency - a characteristic shared across the whole Polk XT lineup, requiring either EQ or toe-out to tame.
Buy the Infinity IL10. It ranks higher for sound quality than the Polk Monitor XT20 and costs less, so there is no real case for the other one.
Specifications Side By Side
| Infinity IL10 | Polk Monitor XT20 | |
|---|---|---|
| Price | $160 used, Discontinued | $279.00 |
| Ranked | #59 of 100 in Large Size Bookshelf Speakers | #65 of 100 in Large Size Bookshelf Speakers |
| Bass Extension (-10dB) | 44Hz (measured, Audio Science Review) | 50Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-3dB) | 59Hz (measured, Audio Science Review) | 75Hz (measured, Erin’s Audio Corner) |
| Impedance | 6 ohms | 8 ohms nominal (measured, Erin’s Audio Corner) |
| Sensitivity | 86dB (measured, Audio Science Review) | 86dB (measured by Erin’s Audio Corner; 87dB manufacturer specified) |
| Drivers | 6.5" (165mm) woofer | 6.5" bilaminate paper cone woofer, 1" Terylene dome tweeter |
| Weight | 14.3 lbs / 6.5 kg | 11.9 lbs / 5.4 kg each |
| Discontinued | Yes | - |
| Dimensions | 15.6"H x 8.5"W x 11.5"D (397.0 x 216.0 x 292.0 mm) | 13"H x 7.5"W x 11"D (330.2 x 190.5 x 279.4 mm) |
| Woofer Cabinet | ported, rear | ported |
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The Two Speakers In Full
Infinity IL10: $160 used, Discontinued
Pros: Impressively flat for a budget bookshelf. Predicted in-room response is good aside from a bit of excess energy here and there. Distortion at 96dB SPL/1m stays low and controlled outside two narrow resonance-driven peaks.
Cons: Resonances at 600 and 5khz, which show up as distinct distortion spikes at 96dB SPL/1m in the same frequency regions. Discontinued.
Full Infinity IL10 review and specifications →
| Bass Extension (-10dB) | 44Hz (measured, Audio Science Review) |
|---|---|
| Bass Extension (-3dB) | 59Hz (measured, Audio Science Review) |
| Dimensions | 15.6"H x 8.5"W x 11.5"D (397.0 x 216.0 x 292.0 mm) |
| Discontinued | Yes |
| Drivers | 6.5" (165mm) woofer |
| Impedance | 6 ohms |
| Sensitivity | 86dB (measured, Audio Science Review) |
| Weight | 14.3 lbs / 6.5 kg |
| Woofer Cabinet | ported, rear |
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Polk Monitor XT20: $279.00 Amazon Crutchfield
Pros: Two-way bookshelf design with a 1” tweeter and 6.5” woofer, part of Polk’s budget-friendly XT lineup (spanning roughly $200-700 across the series). Measures more linear and has fewer/smaller cabinet resonances than its smaller sibling, the XT15, making it - by the reviewer’s own assessment - probably the better of the two based on data alone. Reasonably good bass output for the price and size, with an F3 of 63Hz. Horizontal radiation of about ±50° gives a respectable, enjoyable soundstage width. Takes well to EQ correction - the early-reflections directivity trend is decently linear, meaning tonal adjustments can meaningfully improve the sound. Provides usable, respectable volume when paired with a subwoofer crossover, even though it isn’t intended to play extremely loud on its own.
Cons: Notably bright treble, elevated roughly 1-5dB above the midrange depending on frequency - a characteristic shared across the whole Polk XT lineup, requiring either EQ or toe-out to tame. Small resonances appear around 300Hz and 800Hz, with some of that energy leaking from the port area. Vertical listening window is narrow - best kept close to the tweeter axis, with only a couple of degrees of tolerance above or below before the sound changes. Still needs a subwoofer for real low-end extension despite the decent F3. Overall linearity isn’t state-of-the-art flat, and while the reviewer found it pleasant, some artificial brightness remains even after basic EQ correction in the crossover region.
Full Polk Monitor XT20 review and specifications →
| Bass Extension (-10dB) | 50Hz (measured, Erin's Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 75Hz (measured, Erin's Audio Corner) |
| Dimensions | 13"H x 7.5"W x 11"D (330.2 x 190.5 x 279.4 mm) |
| Drivers | 6.5" bilaminate paper cone woofer, 1" Terylene dome tweeter |
| Impedance | 8 ohms nominal (measured, Erin's Audio Corner) |
| Sensitivity | 86dB (measured by Erin's Audio Corner; 87dB manufacturer specified) |
| Weight | 11.9 lbs / 5.4 kg each |
| Woofer Cabinet | ported |
As an eBay Partner, we may be compensated if you make a purchase.
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