Short answer: the AsciLab C6B. It ranks #6 of 222 bookshelf speakers by sound quality, rated 4.7/5, at $1,145. The Polk Signature Elite ES20 ranks #120, rated 3.7/5, at $397, $748 cheaper, which does not close the gap in sound quality.
The AsciLab C6B is the more accurate option. Two-way design pairing a 1” aluminum ceramic dome tweeter on a large waveguide with a 6” aluminum ceramic cone woofer, crossed over at 1.1kHz, plus a rear passive radiator. Its measured preference score, a predictor of how neutral it sounds, is 6.33 against 4.49 for the Polk Signature Elite ES20. The tradeoff: Bass rolls off around 50Hz in-room (F3 54Hz, F10 35Hz), so a subwoofer is needed for real extension below that.
The case for the Polk Signature Elite ES20: A full-size, efficient 6.5-inch bookshelf pair with unusually deep bass for the price. The catch: Predicted in-room smoothness of 0.238 and directivity-index consistency of 3.81 are average rather than class-leading.
Buy the AsciLab C6B. It is rated higher for sound quality, and the $748 you would save on the Polk Signature Elite ES20 does not close the gap.
Looking for alternatives? See the complete Passive Home rankings.
Two-way design pairing a 1” aluminum ceramic dome tweeter on a large waveguide with a 6” aluminum ceramic cone woofer, crossed over at 1.1kHz, plus a rear passive radiator.
Ascilab $1145 eBay
A full-size, efficient 6.5-inch bookshelf pair with unusually deep bass for the price.
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Specifications Side By Side
| AsciLab C6B | Polk Signature Elite ES20 | |
|---|---|---|
| Price | $1145 per pair | $397.00 per pair |
| Ranked | #6 of 222 in Large Size Bookshelf Speakers | #120 of 222 in Large Size Bookshelf Speakers |
| Bass Extension (-10dB) | 35Hz (measured, Erin’s Audio Corner) | 38.6Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) |
| Bass Extension (-3dB) | 54Hz (measured, Erin’s Audio Corner) | 55.7Hz (measured, ASR via spinorama.org) |
| Dimensions | 15.7”H x 8”W x 10.4”D (398.8 x 203.2 x 264.2 mm) | 14.8H x 8.5W x 13.8D in |
| Impedance | 4 ohms nominal, 2.6 ohms minimum (measured, Erin’s Audio Corner) | 4/8-ohm compatible |
| Sensitivity | 85.6dB (measured, Erin’s Audio Corner) | 86dB |
| Drivers | 6” Aluminium Ceramic Cone with cast Aluminium Chassis woofer, 1” Aluminium Ceramic Dome tweeter | 1” Terylene dome tweeter, 6.5” polypropylene woofer |
| Weight | 18.5 lbs (8.4 kg) each | 17 lbs (7.7 kg) each |
| Woofer Cabinet | passive radiator | - |
| Spinorama Preference Score | 6.33 | 4.49 |
| Spinorama Preference Score with Perfect Sub | 8.28 | 6.44 |
| DIY Kit | No | No |
| Enclosure | - | 2-way, Power Port bass-reflex |
| Country | - | United States (design) |
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: AsciLab C6B (measured by Erin’s Audio Corner) and Polk Signature Elite ES20 (measured by Audio Science Review), via spinorama.org.
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