Short answer: the SunAudio Purified 4. It ranks #9 of 168 bookshelf speakers by sound quality, rated 4.3/5, at $3,650. The SunAudio Purified 4 4XA25A Fiber+Alu ranks #21, rated 4.2/5, at $3,300, $350 cheaper, not enough of a saving to outweigh the sound-quality gap.
Why pick the SunAudio Purified 4: On-axis response is essentially dead flat from 100Hz to 20kHz, staying within about ±1dB through most of the band and widening only to a gentle +1.5dB rise in the top octave. The tradeoff: A 4-inch woofer means real bass extension is limited (-3dB around 71Hz and -10dB around 53Hz) so a subwoofer is needed for anything below the low-100s.
Why pick the SunAudio Purified 4 4XA25A Fiber+Alu: A variant of the modular SunAudio Purified 4 with a Purifi 4” fiber cone woofer and a BlieSMa 25mm aluminium dome tweeter, each driver in its own CNC-machined aluminium sphere on a tripod stand. The tradeoff: The 4” woofer limits bass to 71.3Hz (-3dB) and about 54.2Hz (-10dB), so it needs a subwoofer.
Buy the SunAudio Purified 4. It is rated higher for sound quality, and the $350 you would save on the SunAudio Purified 4 4XA25A Fiber+Alu does not close the gap.
Still deciding? The full Passive Home rankings cover every ranked option.
Specifications Side By Side
| SunAudio Purified 4 | SunAudio Purified 4 4XA25A Fiber+Alu | |
|---|---|---|
| Price | $3,650 per pair as tested; modular kit, pricing varies by driver/finish configuration | $3,300 per pair |
| Ranked | #9 of 168 in Medium Size Bookshelf Speakers | #21 of 168 in Medium Size Bookshelf Speakers |
| Bass Extension (-3dB) | 71Hz (measured, manufacturer spinorama data) | 71.3Hz (measured, manufacturer spinorama data) |
| Bass Extension (-10dB) | 53Hz (measured, manufacturer spinorama data) | about 54.2Hz (measured, manufacturer spinorama data) |
| Sensitivity | 84.4dB (2.83V/1m, measured, manufacturer spinorama data) | 84dB (manufacturer specified) |
| Drivers | BlieSMa T25A beryllium-dome tweeter (own CNC aluminum enclosure), Purifi 4” Ultra Low Distortion Extended woofer (PP-coated paper/fiber cone) | A Purifi 4” fiber cone woofer and a BlieSMa 25mm aluminium dome tweeter |
| Impedance | 4 ohms | 4 ohms |
| Power Handling | 200W long-term max (woofer) | - |
| Woofer Cabinet | sealed, separate spherical driver modules on tripod stand | sealed, separate spherical driver modules on tripod stand |
| Spinorama Preference Score | 6.73 (manufacturer spinorama data) | 6.44 (manufacturer spinorama data) |
| Spinorama Preference Score with Perfect Sub | 9.44 (manufacturer spinorama data) | 9.17 (manufacturer spinorama data) |
| Dimensions | 34.6” x 12.2” x 11” (880 x 310 x 280 mm) | 34.6” x 12.2” x 11” (880 x 310 x 280 mm) |
| 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.
Measurement data: SunAudio Purified 4 (measured by the manufacturer) and SunAudio Purified 4 4XA25A Fiber+Alu (measured by the manufacturer), via spinorama.org.
Related Speaker Comparisons
More worthwhile head-to-heads for SunAudio Purified 4:
- KEF LS50 Meta vs SunAudio Purified 4
- SunAudio Purified 4 vs Arendal 1961 Monitor
- SunAudio Purified 4 vs SunAudio Purified 4 4XA25B Alu+Beryllium
- SunAudio Purified 4 vs SunAudio Purified 4 4XA25A Alu+Alu
- KEF Q150 vs SunAudio Purified 4
Prices on this page were last checked October 11, 2026 at 4:59 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Speakers In Full
SunAudio Purified 4: $3,650 per pair as tested; modular kit, pricing varies by driver/finish configuration SunAudio eBay
Same family: the SunAudio Purified 4 4XA25A Alu+Alu (larger bookshelf, ranked lower, rated 4.2/5), the SunAudio Purified 4 4XA25A Fiber+Alu (larger bookshelf, ranked lower, rated 4.2/5), the SunAudio Purified 4 4XA25A tw35mm (larger bookshelf, ranked lower, rated 4.1/5) and the SunAudio Purified 4 4XA25B Alu+Beryllium (larger bookshelf, ranked lower, rated 4.3/5).
Pros: On-axis response is essentially dead flat from 100Hz to 20kHz, staying within about ±1dB through most of the band and widening only to a gentle +1.5dB rise in the top octave. The listening window curve tracks on-axis almost exactly, meaning off-axis output stays consistent rather than diverging. Both directivity index curves rise smoothly and monotonically from the bass straight through to 20kHz with no bumps, dips, or discontinuities: a sign of very well-integrated driver-to-driver handoff from the beryllium-dome tweeter. Early reflections and sound power both decline smoothly with frequency, with no resonant peaks anywhere in the response. The manufacturer’s own preference-score modeling comes out to 6.65 unequalized (rising to 9.36 with an ideal subwoofer) with a frequency deviation of just 0.8dB across 300Hz-5kHz: genuinely flagship-tier numbers for a 4-inch woofer design. Distinctive modular build: separate CNC-machined aluminum enclosures for the Purifi 4” woofer and BlieSMa T25A beryllium-dome tweeter, mounted on their own tripod stand, with cone-material and finish options. Measured sensitivity of 84.4dB.
Cons: A 4-inch woofer means real bass extension is limited (-3dB around 71Hz and -10dB around 53Hz) so a subwoofer is needed for anything below the low-100s. Measured sensitivity of 84.4dB is on the low side, meaning it needs more amplifier power than more efficient designs to reach the same volume. This is manufacturer self-measured data with no independent third-party review, so there’s no outside verification of distortion, unit-to-unit consistency, or how the reference crossover performs outside SunAudio’s own lab. The modular two-sphere design and tripod stand is unconventional, and pricing is steep for such a small woofer given the niche, boutique nature of the brand.
Full SunAudio Purified 4 review and specifications →
| Released | Mar 2024 (2 years ago) |
|---|---|
| Bass Extension (-10dB) | 53Hz (measured, manufacturer spinorama data) |
| Bass Extension (-3dB) | 71Hz (measured, manufacturer spinorama data) |
| DIY Kit | No |
| Dimensions | 34.6” x 12.2” x 11” (880 x 310 x 280 mm) |
| Drivers | BlieSMa T25A beryllium-dome tweeter (own CNC aluminum enclosure), Purifi 4” Ultra Low Distortion Extended woofer (PP-coated paper/fiber cone) |
| Impedance | 4 ohms |
| Power Handling | 200W long-term max (woofer) |
| Sensitivity | 84.4dB (2.83V/1m, measured, manufacturer spinorama data) |
| Spinorama Preference Score | 6.73 (manufacturer spinorama data) |
| Spinorama Preference Score with Perfect Sub | 9.44 (manufacturer spinorama data) |
| Woofer Cabinet | sealed, separate spherical driver modules on tripod stand |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
SunAudio Purified 4 4XA25A Fiber+Alu: $3,300 per pair SunAudio eBay
Same family: the SunAudio Purified 4 (smaller bookshelf, ranked higher, rated 4.3/5), the SunAudio Purified 4 4XA25A Alu+Alu (smaller bookshelf, ranked higher, rated 4.2/5), the SunAudio Purified 4 4XA25A tw35mm (larger bookshelf, ranked lower, rated 4.1/5) and the SunAudio Purified 4 4XA25B Alu+Beryllium (larger bookshelf, ranked higher, rated 4.3/5).
Pros: A variant of the modular SunAudio Purified 4 with a Purifi 4” fiber cone woofer and a BlieSMa 25mm aluminium dome tweeter, each driver in its own CNC-machined aluminium sphere on a tripod stand. SunAudio’s Klippel measurements show an exceptionally flat response (0.17 on-axis and 0.12 listening window deviation), for a preference score of 6.44 that reaches 9.17 with an ideal subwoofer.
Cons: The 4” woofer limits bass to 71.3Hz (-3dB) and about 54.2Hz (-10dB), so it needs a subwoofer. The data comes from SunAudio and uses its reference DSP crossover, which the buyer has to reproduce, and no independent measurement exists. It needs separate amplification and DSP for each driver.
Full SunAudio Purified 4 4XA25A Fiber+Alu review and specifications →
| Bass Extension (-10dB) | about 54.2Hz (measured, manufacturer spinorama data) |
|---|---|
| Bass Extension (-3dB) | 71.3Hz (measured, manufacturer spinorama data) |
| DIY Kit | No |
| Dimensions | 34.6” x 12.2” x 11” (880 x 310 x 280 mm) |
| Drivers | A Purifi 4” fiber cone woofer and a BlieSMa 25mm aluminium dome tweeter |
| Impedance | 4 ohms |
| Sensitivity | 84dB (manufacturer specified) |
| Spinorama Preference Score | 6.44 (manufacturer spinorama data) |
| Spinorama Preference Score with Perfect Sub | 9.17 (manufacturer spinorama data) |
| Woofer Cabinet | sealed, separate spherical driver modules on tripod stand |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons