Short answer: the Infinity Primus 360 for linearity, the Polk Audio Reserve R700 for output. The 2005 Primus 360 holds on-axis linearity within about +/-2dB by modern standards, but its 93dB manufacturer sensitivity runs 3-4dB optimistic against a measured 89.4dB average. The R700 offers the higher-output three-way layout with dual 8” mid-bass drivers, at the cost of compression that climbs sharply from 96dB to 102dB.
Buy the Polk Audio Reserve R700. It is rated higher for sound quality and still sold new, while the Infinity Primus 360 is discontinued.
Looking for alternatives? See the complete Passive Home rankings.
Specifications Side By Side
| Polk Audio Reserve R700 | Infinity Primus 360 | |
|---|---|---|
| Price | $2,398 per pair | $650 per pair Discontinued |
| Ranked | #33 of 74 in Large Size Floorstanding Speakers | #40 of 74 in Large Size Floorstanding Speakers |
| Bass Extension (-10dB) | 31Hz (measured, Erin’s Audio Corner) | 37Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-3dB) | 40Hz (measured, Erin’s Audio Corner) | 53Hz (measured, Erin’s Audio Corner) |
| Impedance | 4 ohms nominal, 3.5 ohms minimum (measured above 80Hz, Erin’s Audio Corner) | 8 ohms nominal, 3.5 ohms minimum (measured, Erin’s Audio Corner) |
| Sensitivity | 87.5dB (measured average 300Hz-3kHz @ 2.83V/1m, Erin’s Audio Corner) | 89.4dB (measured, Erin’s Audio Corner; 93dB manufacturer specified) |
| Drivers | 2x 8” polypropylene cone woofers, 1x 6.5” turbine cone midrange, 1x 1” Pinnacle ring radiator tweeter | Two 6.5” mid-woofers, 4” mid-range, 0.75” dome tweeter |
| Weight | 102.1 lbs (46.3 kg) | 48.5 lbs (22 kg) each |
| Woofer Cabinet | ported, down-firing | - |
| Dimensions | 45”H x 12.6”W x 16.9”D (1143.8 x 320.7 x 428.3 mm) | 39” x 8.2” x 13” (990 x 208 x 330 mm) |
| Spinorama Preference Score | 6.38 | 4.97 |
| Spinorama Preference Score with Perfect Sub | 7.83 | 7.10 |
| DIY Kit | No | No |
| Frequency Response | - | 38Hz - 20kHz (±3dB, Manufacturer specified) |
| Crossover Frequency | - | 350Hz & 3.3kHz, 24dB/octave |
| Recommended Power | - | 10-200W |
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The Two Speakers In Full
Polk Audio Reserve R700: $2,398 per pair Amazon eBay
Pros: Three-way design with a 1” ring radiator tweeter, 6.5” mid-range, and dual 8” mid-bass drivers in a ported, down-firing cabinet. On-axis frequency response holds within about ±2dB across most of its range, with genuinely deep bass extension (F3 40Hz) reaching into the mid-30s Hz in-room. Wide horizontal radiation of about ±70°, giving a strong, enveloping stereo width and stage-extension effect on well-recorded tracks. Good low-level dynamics: solid bass thump at quiet listening volumes without over-accentuation. Strong distortion and compression control through the bass and midrange. Real nominal impedance closer to 4 ohms than the marketed 8 ohms, so with the right amplifier it can be driven hard: a $3,000 two-channel integrated brought out significantly more life than a budget $300 unit could. Excellent value at its roughly $1199/pair, ranking among the reviewer’s top picks under $2,500; outperforms the similarly-priced Klipsch RP-8000F II in bass extension and overall smoothness. Measured bass extension of 40Hz (-3dB), with a measured sensitivity of 87.5dB.
Cons: Compression in the high frequencies rises sharply between 96dB and 102dB output: a real limitation only at very high volumes (around 100dB at 3 meters), but a clear step down from pricier ($5,000+) towers. Horizontal directivity mismatch around 4-5kHz, where the tweeter flares wider than the midrange, can sound a bit forward, especially noticeable when toed out further into the room; sidewall absorption or curtains help tame it. Harmonic distortion crosses the reviewer’s 3% threshold around 7kHz at 96dB output, possibly contributing to that same forward quality at high volume. Narrow vertical sweet spot (about ±15° from the tweeter axis), typical of non-coaxial tower designs: more of a consideration for multi-row home theater seating than single-row listening. The ring-radiator tweeter narrows noticeably above about 7-8kHz, and toeing the speaker out more than about 20° causes the top end to fall off quickly. Needs at least 2 feet of clearance from the rear wall to avoid boomy, exaggerated bass, since it lacks the bass-shelf tuning some rivals use to allow closer wall placement. Compared to the pricier KEF R5 Meta, has narrower horizontal (and much narrower vertical) directivity, so seating flexibility is more limited.
Full Polk Audio Reserve R700 review and specifications →
| Bass Extension (-10dB) | 31Hz (measured, Erin’s Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 40Hz (measured, Erin’s Audio Corner) |
| DIY Kit | No |
| Dimensions | 45”H x 12.6”W x 16.9”D (1143.8 x 320.7 x 428.3 mm) |
| Drivers | 2x 8” polypropylene cone woofers, 1x 6.5” turbine cone midrange, 1x 1” Pinnacle ring radiator tweeter |
| Impedance | 4 ohms nominal, 3.5 ohms minimum (measured above 80Hz, Erin’s Audio Corner) |
| Sensitivity | 87.5dB (measured average 300Hz-3kHz @ 2.83V/1m, Erin’s Audio Corner) |
| Spinorama Preference Score | 6.38 |
| Spinorama Preference Score with Perfect Sub | 7.83 |
| Weight | 102.1 lbs (46.3 kg) |
| Woofer Cabinet | ported, down-firing |
- Links
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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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