Short answer: the KEF Reference 203 for better sound quality, the Infinity Primus 360 for the lower price. The KEF Reference 203 ranks #13 of 71 floorstanding speakers at $5000. The Infinity Primus 360 ranks #40 at $650, $4350 cheaper.
What the KEF Reference 203 offers: An unusually accomplished 4-way design for its era: excellent on-axis linearity (within about +/-3dB), genuinely good directivity both horizontally (~55 degrees) and vertically (~40-50 degrees), and an estimated in-room response that closely matches what the reviewer actually heard. Distortion is excellent - under 1% harmonic above 80Hz at both 86dB and 96dB, and multitone stays around 1% even at 96dB. Bass reaches a real F3 of 51Hz (F10 37Hz), with in-room extension into the low-mid-40s. The reviewer’s overall listening notes were essentially “nothing stood out bad or good” - a genuinely neutral, accurate speaker with a distinctive rounded-baffle look that avoids the diffraction issues a flat baffle this wide would normally have. Watch for: This is a 20+ year old, long-discontinued speaker only findable secondhand (Facebook Marketplace, Craigslist, audio forums) - condition, driver matching, and component aging vary by unit, so audition before buying if at all possible. Demands a robust amplifier: impedance dips to about 3.6 ohms with an EPDR of 2.2 ohms. The small supertweeter shows minor breakup artifacts at the extremes of the vertical polar plot and some compression at very high output in the top octave, though neither was audible in normal listening.
What the Infinity Primus 360 offers: A three-way tower from 2005 (two 6.5” mid-woofers, a 4” mid-range, and a 0.75” dome tweeter, 8 ohms nominal) that holds up remarkably well by modern measurement standards: on-axis linearity is within about ±2dB, and the listening window stays consistent out to roughly ±30° horizontal and ±10° vertical off the mid-range axis. Horizontal directivity is well controlled out to about ±75° before tonality starts to drift, meaning the reflected sound in a room stays close in character to the direct sound - a speaker that takes EQ well without fighting itself. Harmonic distortion measures low at both 86dB and 96dB, and multitone distortion stays under the reviewer’s 3% threshold. Silky, smooth midrange with a rich lower-midrange/upper-bass character. No mechanical issues or surround degradation found in a 20-year-old pair, and a second unit measured within about 1-1.5dB of the first, suggesting good long-term consistency for the design. Watch for: Manufacturer-spec sensitivity of 93dB runs about 3-4dB optimistic versus the measured 89.4dB average. Bass output drops off fairly quickly below about 50Hz in-room (F3 53Hz, F10 37Hz), so a subwoofer is needed for real low-end extension. Resonances show up around 170Hz, 220Hz, and 350Hz. On-axis, the lower treble can sound a bit bright or sibilant when the speaker is aimed directly at the listener; toeing out about 10-15° (rather than the more extreme 30°) gave the best balance, and some sidewall acoustic absorption further tamed a 4-5kHz peak. Placed close to the rear wall, bass gets boomy - pulling the speakers out about a foot resolves most of it, with roughly 1.5 feet from the wall as a good compromise between bass character and typical room aesthetics. Straying beyond about 25° above or below the mid-range axis introduces audible suckout. No longer in production, so it’s a used/secondhand purchase only.
Buy the KEF Reference 203 if sound quality matters more than the price. Buy the Infinity Primus 360 if the price matters more than sound quality.
Specifications Side By Side
| KEF Reference 203 | Infinity Primus 360 | |
|---|---|---|
| Price | $5000 Discontinued | $650.00 Discontinued |
| Ranked | #13 of 71 in Large Size Floorstanding Speakers | #40 of 71 in Large Size Floorstanding Speakers |
| Bass Extension (-10dB) | 37Hz (measured, Erin’s Audio Corner) | 37Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-3dB) | 51Hz (measured, Erin’s Audio Corner) | 53Hz (measured, Erin’s Audio Corner) |
| Dimensions | 1067H mm (42" tall) | 39"H x 8-1/8"W x 13-7/8"D (990 x 208 x 330mm) |
| Impedance | 8 ohms nominal (3.6 ohms minimum, measured, Erin’s Audio Corner; 3.2 ohms per manufacturer spec) | 8 ohms nominal, 3.5 ohms minimum (measured, Erin’s Audio Corner) |
| Sensitivity | 88dB (2.83V/1m, measured by Erin’s Audio Corner) | 89.4dB (measured, Erin’s Audio Corner; 93dB manufacturer specified) |
| Drivers | 1x 0.75" supertweeter, coaxial 1" dome tweeter + 6.5" midrange, 2x 6.5" woofers | Two 6.5" mid-woofers, 4" mid-range, 0.75" dome tweeter |
| Weight | 58 lbs / 26.3 kg (58 lb) | 48.5 lbs (48.5 lbs / 22 kg) each |
| Woofer Cabinet | Bass reflex, with switchable flat/cut/lifted bass ports for wall placement | - |
| Crossover Frequency | 400Hz, 2.7kHz, 15kHz | - |
| Discontinued | Yes | Yes |
| Frequency Response | 55Hz - 55kHz ±3dB (Manufacturer specified) | 38Hz - 20kHz (±3dB, Manufacturer specified) |
| Recommended Power | 50-200W | 10-200W |
| Crossovers | - | 350Hz & 3.3kHz, 24dB/octave |
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Prices on this page were last checked August 25, 2026 at 6:19 AM 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
KEF Reference 203: $5000 Discontinued eBay
Pros: An unusually accomplished 4-way design for its era: excellent on-axis linearity (within about +/-3dB), genuinely good directivity both horizontally (~55 degrees) and vertically (~40-50 degrees), and an estimated in-room response that closely matches what the reviewer actually heard. Distortion is excellent - under 1% harmonic above 80Hz at both 86dB and 96dB, and multitone stays around 1% even at 96dB. Bass reaches a real F3 of 51Hz (F10 37Hz), with in-room extension into the low-mid-40s. The reviewer’s overall listening notes were essentially “nothing stood out bad or good” - a genuinely neutral, accurate speaker with a distinctive rounded-baffle look that avoids the diffraction issues a flat baffle this wide would normally have.
Cons: This is a 20+ year old, long-discontinued speaker only findable secondhand (Facebook Marketplace, Craigslist, audio forums) - condition, driver matching, and component aging vary by unit, so audition before buying if at all possible. Demands a robust amplifier: impedance dips to about 3.6 ohms with an EPDR of 2.2 ohms. The small supertweeter shows minor breakup artifacts at the extremes of the vertical polar plot and some compression at very high output in the top octave, though neither was audible in normal listening. Discontinued.
Full KEF Reference 203 review and specifications →
| Bass Extension (-10dB) | 37Hz (measured, Erin's Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 51Hz (measured, Erin's Audio Corner) |
| Crossover Frequency | 400Hz, 2.7kHz, 15kHz |
| Dimensions | 1067H mm (42" tall) |
| Discontinued | Yes |
| Drivers | 1x 0.75" supertweeter, coaxial 1" dome tweeter + 6.5" midrange, 2x 6.5" woofers |
| Frequency Response | 55Hz - 55kHz ±3dB (Manufacturer specified) |
| Impedance | 8 ohms nominal (3.6 ohms minimum, measured, Erin's Audio Corner; 3.2 ohms per manufacturer spec) |
| Recommended Power | 50-200W |
| Sensitivity | 88dB (2.83V/1m, measured by Erin's Audio Corner) |
| Weight | 58 lbs / 26.3 kg (58 lb) |
| Woofer Cabinet | Bass reflex, with switchable flat/cut/lifted bass ports for wall placement |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Infinity Primus 360: $650.00 Discontinued eBay
Pros: A three-way tower from 2005 (two 6.5” mid-woofers, a 4” mid-range, and a 0.75” dome tweeter, 8 ohms nominal) that holds up remarkably well by modern measurement standards: on-axis linearity is within about ±2dB, and the listening window stays consistent out to roughly ±30° horizontal and ±10° vertical off the mid-range axis. Horizontal directivity is well controlled out to about ±75° before tonality starts to drift, meaning the reflected sound in a room stays close in character to the direct sound - a speaker that takes EQ well without fighting itself. Harmonic distortion measures low at both 86dB and 96dB, and multitone distortion stays under the reviewer’s 3% threshold. Silky, smooth midrange with a rich lower-midrange/upper-bass character. No mechanical issues or surround degradation found in a 20-year-old pair, and a second unit measured within about 1-1.5dB of the first, suggesting good long-term consistency for the design.
Cons: Manufacturer-spec sensitivity of 93dB runs about 3-4dB optimistic versus the measured 89.4dB average. Bass output drops off fairly quickly below about 50Hz in-room (F3 53Hz, F10 37Hz), so a subwoofer is needed for real low-end extension. Resonances show up around 170Hz, 220Hz, and 350Hz. On-axis, the lower treble can sound a bit bright or sibilant when the speaker is aimed directly at the listener; toeing out about 10-15° (rather than the more extreme 30°) gave the best balance, and some sidewall acoustic absorption further tamed a 4-5kHz peak. Placed close to the rear wall, bass gets boomy - pulling the speakers out about a foot resolves most of it, with roughly 1.5 feet from the wall as a good compromise between bass character and typical room aesthetics. Straying beyond about 25° above or below the mid-range axis introduces audible suckout. No longer in production, so it’s a used/secondhand purchase only. Discontinued.
Full Infinity Primus 360 review and specifications →
| Bass Extension (-10dB) | 37Hz (measured, Erin's Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 53Hz (measured, Erin's Audio Corner) |
| Crossovers | 350Hz & 3.3kHz, 24dB/octave |
| Dimensions | 39"H x 8-1/8"W x 13-7/8"D (990 x 208 x 330mm) |
| Discontinued | Yes |
| Drivers | Two 6.5" mid-woofers, 4" mid-range, 0.75" dome tweeter |
| Frequency Response | 38Hz - 20kHz (±3dB, Manufacturer specified) |
| Impedance | 8 ohms nominal, 3.5 ohms minimum (measured, Erin's Audio Corner) |
| Recommended Power | 10-200W |
| Sensitivity | 89.4dB (measured, Erin's Audio Corner; 93dB manufacturer specified) |
| Weight | 48.5 lbs (48.5 lbs / 22 kg) each |
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