Short answer: the Ascend Acoustics CBM-170 SE2. It ranks #114 of 222 bookshelf speakers by sound quality, rated 3.8/5, at $468. The Polk Monitor XT20 ranks #157, rated 3.4/5, at $279, $189 cheaper, not enough of a saving to outweigh the sound-quality gap.
The Ascend Acoustics CBM-170 SE2 is the more accurate pick. On-axis response is impressively flat from about 100Hz to 2kHz, staying within roughly ±1dB, with a clean, gradual bass rolloff below that. Its measured preference score, a predictor of how neutral it sounds, is 6.30 against 4.71 for the Polk Monitor XT20. The tradeoff: A narrow dip in the on-axis and listening-window response appears in the 3-5kHz range (down to about -2.7dB), mirrored by a matching dip in the directivity index at the same frequencies: likely a brief widening of dispersion right at the tweeter/woofer crossover.
The case for the Polk Monitor XT20: 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). The tradeoff: 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 Ascend Acoustics CBM-170 SE2. It is rated higher for sound quality, and the $189 saving on the Polk Monitor XT20 is not enough to make up the difference.
Still deciding? The full Passive Home rankings cover every ranked option.
On-axis response is impressively flat from about 100Hz to 2kHz, staying within roughly ±1dB, with a clean, gradual bass rolloff below that.
Ascend Acoustics $468 eBay
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).
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Specifications Side By Side
| Ascend Acoustics CBM-170 SE2 | Polk Monitor XT20 | |
|---|---|---|
| Price | $468 per pair | $279.00 per pair |
| Ranked | #114 of 222 in Large Size Bookshelf Speakers | #157 of 222 in Large Size Bookshelf Speakers |
| Bass Extension (-3dB) | 70Hz (measured, manufacturer spinorama data) | 64.5Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-10dB) | 50Hz (measured, manufacturer spinorama data) | 43.4Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) |
| Sensitivity | 86.8dB (2.83V/1m, measured, manufacturer spinorama data; 87dB manufacturer specified) | 86dB (measured by Erin’s Audio Corner; 87dB manufacturer specified) |
| Drivers | 27mm custom SEAS soft dome tweeter, 6.5” proprietary composite polygel cone woofer | 6.5” bilaminate paper cone woofer, 1” Terylene dome tweeter |
| Dimensions | 12H x 9W x 9.5D in | 13”H x 7.5”W x 11”D (330.2 x 190.5 x 279.4 mm) |
| Weight | 15 lbs (6.8 kg) each | 11.9 lbs (5.4 kg) each |
| Impedance | 8 ohms | 8 ohms nominal (measured, Erin’s Audio Corner) |
| Power Handling | 200W continuous, 400W peak | - |
| Woofer Cabinet | ported, rear | ported |
| Spinorama Preference Score | 6.30 | 4.71 |
| Spinorama Preference Score with Perfect Sub | 8.66 | 7.07 |
| DIY Kit | No | No |
Frequency Response Compared
Both speakers’ spinorama measurements, overlaid. A flatter line is more neutral: peaks sound forward or harsh, dips sound recessed. Each curve is shifted so its average from 300 Hz to 3 kHz sits at 0 dB, so loudness differences between the two are removed and only the shape is compared. The two were measured by different sources, so small differences, especially in the bass, can come from the measurement setup rather than the speakers.
Measurement data: Ascend Acoustics CBM-170 SE2 (measured by the manufacturer) and Polk Monitor XT20 (measured by Erin’s Audio Corner), via spinorama.org.
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