These are not really the same size class, and that is the honest framing here. The Infinity Primus 360 ranks #73 of 163 floorstanding speakers by sound quality at $650; the Infinity Primus 150 ranks #77 of 144 bookshelf speakers by sound quality at $200.
The Infinity Primus 360 is the more accurate, deeper-bass pick. Its measured preference score, a predictor of how neutral it sounds, is 4.97 against 4.21 for the Infinity Primus 150. Its bass reaches about 53Hz before falling 3dB, against 68.3Hz for the Infinity Primus 150. The catch: Manufacturer-spec sensitivity of 93dB runs about 3-4dB optimistic versus the measured 89.4dB average.
Why pick the Infinity Primus 150: A budget two-way with a 5.25” woofer and a 0.75” tweeter. The catch: Infinity ended its home speaker line.
One note: the Infinity Primus 360 is no longer sold new, but at #73 of 163 floorstanding speakers by sound quality it still outranks most current models, so used is worth considering.
Buy the Infinity Primus 360 at $650 for a floorstanding speaker, or the Infinity Primus 150 at $200 for a bookshelf speaker instead.
Looking for alternatives? See the complete Passive Home rankings.
Specifications Side By Side
| Infinity Primus 360 | Infinity Primus 150 | |
|---|---|---|
| Price | $650 per pair Discontinued | $200 per pair Discontinued |
| Ranked | #73 of 163 in Large Size Floorstanding Speakers | #77 of 144 in Medium Size Bookshelf Speakers |
| Bass Extension (-10dB) | 37Hz (measured, Erin’s Audio Corner) | about 56.8Hz (measured, third-party data via spinorama.org) |
| Bass Extension (-3dB) | 53Hz (measured, Erin’s Audio Corner) | 68.3Hz (measured, third-party data via spinorama.org) |
| Drivers | Two 6.5” mid-woofers, 4” mid-range, 0.75” dome tweeter | 5.25” (130mm) woofer, 0.75” (19mm) tweeter |
| Sensitivity | 89.4dB (measured, Erin’s Audio Corner; 93dB manufacturer specified) | 88dB (manufacturer specified) |
| Impedance | 8 ohms nominal, 3.5 ohms minimum (measured, Erin’s Audio Corner) | 8 ohms |
| Dimensions | 39” x 8.2” x 13” (990 x 208 x 330 mm) | 12.7”H x 7.4”W x 10.5”D (322 x 187 x 267 mm) |
| Weight | 48.5 lbs (22 kg) each | 13.2 lbs (6 kg) each |
| Frequency Response | 38Hz - 20kHz (±3dB, Manufacturer specified) | 58Hz-20kHz (manufacturer specified) |
| Crossover Frequency | 350Hz & 3.3kHz, 24dB/octave | - |
| Recommended Power | 10-200W | - |
| Spinorama Preference Score | 4.97 | 4.21 |
| Spinorama Preference Score with Perfect Sub | 7.10 | 7.05 |
| DIY Kit | No | No |
Related Speaker Comparisons
How Infinity Primus 360 compares with other leading options:
- Revel F226Be vs Infinity Primus 360
- KEF Reference 203 vs Infinity Primus 360
- JBL HDI-3800 vs Infinity Primus 360
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- Revel F208 vs Infinity Primus 360
Prices on this page were last checked October 6, 2026 at 10:23 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
Infinity Primus 360: $650 per pair 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. Measured bass extension of 53Hz (-3dB), with a measured sensitivity of 89.4dB.
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.
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) |
| Crossover Frequency | 350Hz & 3.3kHz, 24dB/octave |
| DIY Kit | No |
| Dimensions | 39” x 8.2” x 13” (990 x 208 x 330 mm) |
| 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) |
| Spinorama Preference Score | 4.97 |
| Spinorama Preference Score with Perfect Sub | 7.10 |
| Weight | 48.5 lbs (22 kg) each |
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Infinity Primus 150: $200 per pair Discontinued eBay
Pros: A budget two-way with a 5.25” woofer and a 0.75” tweeter. Sensitivity is 88dB. Measurements show a preference score of 4.21 that reaches 7.05 with an ideal subwoofer, with 0.39 listening window deviation. Measured bass extension of 68.3Hz (-3dB).
Cons: Infinity ended its home speaker line. Bass reaches 68.3Hz (-3dB) and about 57Hz (-10dB). Discontinued.
Full Infinity Primus 150 review and specifications →
| Bass Extension (-10dB) | about 56.8Hz (measured, third-party data via spinorama.org) |
|---|---|
| Bass Extension (-3dB) | 68.3Hz (measured, third-party data via spinorama.org) |
| DIY Kit | No |
| Dimensions | 12.7”H x 7.4”W x 10.5”D (322 x 187 x 267 mm) |
| Drivers | 5.25” (130mm) woofer, 0.75” (19mm) tweeter |
| Frequency Response | 58Hz-20kHz (manufacturer specified) |
| Impedance | 8 ohms |
| Sensitivity | 88dB (manufacturer specified) |
| Spinorama Preference Score | 4.21 |
| Spinorama Preference Score with Perfect Sub | 7.05 |
| Weight | 13.2 lbs (6 kg) each |
- Reviews, Comparisons and Sound Samples