Short answer: the SunAudio Purified 4 4XA25A Fiber+Alu. It ranks #21 of 168 bookshelf speakers by sound quality, rated 4.2/5, at $3,300. The SunAudio Purified 4 4XA25A tw35mm ranks #24, rated 4.1/5, at $2,800, $500 cheaper, a saving that is not big enough to make up the sound-quality gap.
What the SunAudio Purified 4 4XA25A Fiber+Alu does well: 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.
The case for the SunAudio Purified 4 4XA25A tw35mm: A variant of the modular SunAudio Purified 4 with a Purifi 4” woofer and a BlieSMa 25mm aluminium dome tweeter in the configuration SunAudio labels tw35mm, each driver in its own CNC-machined aluminium sphere on a tripod stand. The tradeoff: The 4” woofer limits bass to 73.4Hz (-3dB) and about 42Hz (-10dB), so it needs a subwoofer.
Buy the SunAudio Purified 4 4XA25A Fiber+Alu. It is rated higher for sound quality, and the $500 saving on the SunAudio Purified 4 4XA25A tw35mm is not enough to make up the difference.
Still deciding? The full Passive Home rankings cover every ranked option.
Specifications Side By Side
| SunAudio Purified 4 4XA25A Fiber+Alu | SunAudio Purified 4 4XA25A tw35mm | |
|---|---|---|
| Price | $3,300 per pair | $2,800 per pair |
| Ranked | #21 of 168 in Medium Size Bookshelf Speakers | #24 of 168 in Medium Size Bookshelf Speakers |
| Sensitivity | 84dB (manufacturer specified) | - |
| Drivers | A Purifi 4” fiber cone woofer and a BlieSMa 25mm aluminium dome tweeter | A Purifi 4” woofer and a BlieSMa 25mm aluminium dome tweeter in the configuration SunAudio labels tw35mm |
| Woofer Cabinet | sealed, separate spherical driver modules on tripod stand | sealed, separate spherical driver modules on tripod stand |
| Impedance | 4 ohms | 4 ohms |
| Bass Extension (-3dB) | 71.3Hz (measured, manufacturer spinorama data) | 73.4Hz (measured, manufacturer spinorama data) |
| Bass Extension (-10dB) | about 54.2Hz (measured, manufacturer spinorama data) | about 42Hz (measured, manufacturer spinorama data) |
| Spinorama Preference Score | 6.44 (manufacturer spinorama data) | 6.14 (manufacturer spinorama data) |
| Spinorama Preference Score with Perfect Sub | 9.17 (manufacturer spinorama data) | 8.74 (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 4XA25A Fiber+Alu (measured by the manufacturer) and SunAudio Purified 4 4XA25A tw35mm (measured by the manufacturer), via spinorama.org.
Related Speaker Comparisons
How SunAudio Purified 4 4XA25A Fiber+Alu compares with other leading options:
- SunAudio Purified 4 vs SunAudio Purified 4 4XA25A Fiber+Alu
- SunAudio Purified 4 4XA25B Alu+Beryllium vs SunAudio Purified 4 4XA25A Fiber+Alu
- SunAudio Purified 4 4XA25A Alu+Alu vs SunAudio Purified 4 4XA25A Fiber+Alu
- SunAudio Purified 4 4XA25A Alu+Alu vs SunAudio Purified 4 4XA25A tw35mm
- SunAudio Purified 4 4XA25A tw35mm vs Radiant Acoustics Clarity 4.2
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 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
SunAudio Purified 4 4XA25A tw35mm: $2,800 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 Fiber+Alu (smaller bookshelf, ranked higher, rated 4.2/5) 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” woofer and a BlieSMa 25mm aluminium dome tweeter in the configuration SunAudio labels tw35mm, each driver in its own CNC-machined aluminium sphere on a tripod stand. SunAudio’s Klippel measurements show an exceptionally flat response (0.20 on-axis and 0.17 listening window deviation), for a preference score of 6.14 that reaches 8.74 with an ideal subwoofer.
Cons: The 4” woofer limits bass to 73.4Hz (-3dB) and about 42Hz (-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 tw35mm review and specifications →
| Bass Extension (-10dB) | about 42Hz (measured, manufacturer spinorama data) |
|---|---|
| Bass Extension (-3dB) | 73.4Hz (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” woofer and a BlieSMa 25mm aluminium dome tweeter in the configuration SunAudio labels tw35mm |
| Impedance | 4 ohms |
| Spinorama Preference Score | 6.14 (manufacturer spinorama data) |
| Spinorama Preference Score with Perfect Sub | 8.74 (manufacturer spinorama data) |
| Woofer Cabinet | sealed, separate spherical driver modules on tripod stand |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons