Short answer: the AsciLab C6B. It ranks #6 of 222 bookshelf speakers by sound quality, rated 4.7/5, at $1,145. The XTZ Spirit 4 ranks #159, rated 3.4/5, at $477, $668 cheaper, which does not close the gap in sound quality.
The AsciLab C6B is the more accurate, deeper-bass choice. 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 4.18 for the XTZ Spirit 4. Its bass reaches about 35Hz before falling 10dB, against 40Hz for the XTZ Spirit 4. The catch: Bass rolls off around 50Hz in-room (F3 54Hz, F10 35Hz), so a subwoofer is needed for real extension below that.
What the XTZ Spirit 4 does well: Substantial 6.5-inch stand-mount with a waveguided dome tweeter, adjustable treble level and port tuning. The tradeoff: The third-party measurement is low confidence.
Buy the AsciLab C6B. It is rated higher for sound quality, and saving $668 with the XTZ Spirit 4 does not make up for the sound-quality gap.
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Specifications Side By Side
| AsciLab C6B | XTZ Spirit 4 | |
|---|---|---|
| Price | $1145 per pair | $477 per pair |
| Ranked | #6 of 222 in Large Size Bookshelf Speakers | #159 of 222 in Large Size Bookshelf Speakers |
| Bass Extension (-10dB) | 35Hz (measured, Erin’s Audio Corner) | about 40.0Hz (measured, Spinorama data) |
| Bass Extension (-3dB) | 54Hz (measured, Erin’s Audio Corner) | 42Hz (manufacturer specified) |
| Dimensions | 15.7”H x 8”W x 10.4”D (398.8 x 203.2 x 264.2 mm) | 13.8H x 7.5W x 10.6D in |
| Impedance | 4 ohms nominal, 2.6 ohms minimum (measured, Erin’s Audio Corner) | 4 ohms |
| 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” dome tweeter, 6.5” woofer |
| Weight | 18.5 lbs (8.4 kg) each | 17.9 lbs (8.1 kg) each |
| Woofer Cabinet | passive radiator | - |
| Spinorama Preference Score | 6.33 | 4.18 |
| Spinorama Preference Score with Perfect Sub | 8.28 | 6.30 |
| DIY Kit | No | No |
| Enclosure | - | 2-way passive, rear-ported |
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 XTZ Spirit 4 (measured by an independent reviewer), via spinorama.org.
Related Speaker Comparisons
More worthwhile head-to-heads for AsciLab C6B:
- AsciLab C6B vs Perlisten S4b
- AsciLab C6B vs KEF Reference 1 Meta
- AsciLab C6B vs GR-Research NX-Studio
- AsciLab C6B vs March Audio Sointuva AWG
- AsciLab C6B vs Audio First Cadentia 3
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The Two Speakers In Full
AsciLab C6B: $1145 per pair Ascilab $1145 eBay
Same family: the AsciLab C5B (smaller bookshelf, rated 4.2/5).
Pros: 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. Unusual trait: horizontal radiation actually widens at higher frequencies instead of narrowing like most two-way designs, which keeps image focus and soundstage depth consistent whether you toe the speakers in or out (5-10° off-axis was the sweet spot in testing). Vertical radiation also stays wide straight through the 2kHz crossover region, so the sound doesn’t collapse when standing up: unusual at this price. CA2034 measurements show strong on-axis linearity, listening window, early reflections, and directivity. Midrange and tweeter distortion stay very low even at 96dB, holding up against a $5,900 Arendal speaker in that regard despite roughly a 5x price gap. At $1145 shipped to the US, the reviewer calls it the best-value bookshelf speaker he’s tested, rivaling speakers 2-5x the price. Measured bass extension of 54Hz (-3dB), with a measured sensitivity of 85.6dB.
Cons: Bass rolls off around 50Hz in-room (F3 54Hz, F10 35Hz), so a subwoofer is needed for real extension below that. Low-frequency harmonic distortion increases substantially at 96dB versus 86dB, though it’s second-order and less audible than it looks on paper. Minimum impedance dips to 2.6 ohms (EPDR as low as 1.2 ohms), so it wants an amplifier comfortable driving 4-ohm loads, ideally 100W or more. At 102dB, compression noticeably eats into midrange, bass, and some treble output. Shipping to the US adds roughly $200 on top of AsciLab’s list price. Against the reviewer’s reference Audiofirst Fidelia at a similar price, has slightly less lower-midrange body (about 1dB difference) and a smaller perceived soundstage size.
Full AsciLab C6B review and specifications →
| Bass Extension (-10dB) | 35Hz (measured, Erin’s Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 54Hz (measured, Erin’s Audio Corner) |
| DIY Kit | No |
| Dimensions | 15.7”H x 8”W x 10.4”D (398.8 x 203.2 x 264.2 mm) |
| Drivers | 6” Aluminium Ceramic Cone with cast Aluminium Chassis woofer, 1” Aluminium Ceramic Dome tweeter |
| Impedance | 4 ohms nominal, 2.6 ohms minimum (measured, Erin’s Audio Corner) |
| Sensitivity | 85.6dB (measured, Erin’s Audio Corner) |
| Spinorama Preference Score | 6.33 |
| Spinorama Preference Score with Perfect Sub | 8.28 |
| Weight | 18.5 lbs (8.4 kg) each |
| Woofer Cabinet | passive radiator |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
XTZ Spirit 4: $477 per pair XTZ $477 eBay
Pros: Substantial 6.5-inch stand-mount with a waveguided dome tweeter, adjustable treble level and port tuning. Spinorama predicts 44Hz in-room extension, broad roughly +/-60-degree horizontal coverage and a 6.30 preference score with a subwoofer. Measured bass extension of 40.0Hz (-10dB).
Cons: The third-party measurement is low confidence. On-axis smoothness is only 0.248, directivity-index consistency is middling at 3.21, and the mildly downward -0.29dB/octave tonal slope contributes to a modest 4.18 raw preference score.
Full XTZ Spirit 4 review and specifications →
| Released | Nov 2018 (7 years ago) |
|---|---|
| Bass Extension (-10dB) | about 40.0Hz (measured, Spinorama data) |
| Bass Extension (-3dB) | 42Hz (manufacturer specified) |
| DIY Kit | No |
| Dimensions | 13.8H x 7.5W x 10.6D in |
| Drivers | 1” dome tweeter, 6.5” woofer |
| Enclosure | 2-way passive, rear-ported |
| Impedance | 4 ohms |
| Sensitivity | 86dB |
| Spinorama Preference Score | 4.18 |
| Spinorama Preference Score with Perfect Sub | 6.30 |
| Weight | 17.9 lbs (8.1 kg) each |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons