Short answer: the Infinity Primus 360. It ranks #32 of 56 floorstanding speakers by sound quality at $650; the Klipsch Heresy IV ranks #34 and costs $3198, so there is not much of a tradeoff to weigh.
On the Infinity Primus 360 side: 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. Set against that: Manufacturer-spec sensitivity of 93dB runs about 3-4dB optimistic versus the measured 89.4dB average.
What the Klipsch Heresy IV gets right: Very high 94.5dB/2.83V/1m sensitivity in Erin’s anechoic measurement—well below Klipsch’s 99dB in-room claim, but still excellent—and strong short-term output from a 12-inch woofer plus horn-loaded midrange and tweeter. The catch: Erin measured a 77Hz F3 and response rolling away near 100Hz in-room, so a subwoofer is required for modern full-range reproduction.
Buy the Infinity Primus 360. It ranks higher for sound quality than the Klipsch Heresy IV and costs less, so there is no real case for the other one.
Specifications Side By Side
| Infinity Primus 360 | Klipsch Heresy IV | |
|---|---|---|
| Price | $650.00 Discontinued | $3,198/pair |
| Ranked | #32 of 56 in Large Size Floorstanding Speakers | #34 of 56 in Large Size Floorstanding Speakers |
| Bass Extension (-10dB) | 37Hz (measured, Erin’s Audio Corner) | - |
| Bass Extension (-3dB) | 53Hz (measured, Erin’s Audio Corner) | 77Hz (measured, Erin’s Audio Corner) |
| Drivers | Two 6.5" mid-woofers, 4" mid-range, 0.75" dome tweeter | 1" horn-loaded tweeter; 1.75" horn-loaded midrange; 12" woofer |
| Sensitivity | 89.4dB (measured, Erin’s Audio Corner; 93dB manufacturer specified) | 94.5dB/2.83V/1m (measured, Erin’s Audio Corner) |
| Impedance | 8 ohms nominal, 3.5 ohms minimum (measured, Erin’s Audio Corner) | Approximately 4 ohms minimum (measured, Erin’s Audio Corner) |
| Discontinued | Yes | - |
| Dimensions | 39"H x 8-1/8"W x 13-7/8"D (990 x 208 x 330mm) | 24.8"H x 15.6"W x 13.3"D |
| Weight | 48.5 lbs (48.5 lbs / 22 kg) each | 45 lb each |
| Frequency Response | 38Hz - 20kHz (±3dB, Manufacturer specified) | - |
| Crossovers | 350Hz & 3.3kHz, 24dB/octave | - |
| Recommended Power | 10-200W | - |
| Woofer Cabinet | - | ported, rear |
Related Speaker Comparisons
More useful head-to-heads from the same speaker class:
- PSB Imagine T65 vs Definitive Technology BP-9020
- Definitive Technology BP-9020 vs SVS Ultra Evolution Pinnacle
- Klipsch Forte IV vs Polk T50
- ELAC DF63 vs Klipsch Heresy IV
- Polk Reserve R500 vs Klipsch Heresy IV
The Two Speakers In Full
Infinity Primus 360: $650.00 Discontinued
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 |
As an eBay Partner, we may be compensated if you make a purchase.
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Infinity Primus 360 vs Definitive Technology BP-9020
- Infinity Primus 360 vs Klipsch Forte IV
- Infinity Primus 360 vs Linkwitz Lab LXmini
- Infinity Primus 360 vs Polk Reserve R500
- Infinity Primus 360 vs KEF Q11 Meta
- Infinity Primus 360 vs ELAC DF63
- Infinity Primus 360 vs Klipsch RP-5000F II
- Infinity Primus 360 vs PSB Imagine T65
- See all 14 comparisons
Klipsch Heresy IV: $3,198/pair Amazon Crutchfield
Pros: Very high 94.5dB/2.83V/1m sensitivity in Erin’s anechoic measurement—well below Klipsch’s 99dB in-room claim, but still excellent—and strong short-term output from a 12-inch woofer plus horn-loaded midrange and tweeter. The compact, furniture-grade Heritage cabinet is easier to place than most high-efficiency designs, and dynamics at moderate levels can sound lively. A stable four-ohm-capable amplifier can produce substantial SPL with relatively little voltage.
Cons: Erin measured a 77Hz F3 and response rolling away near 100Hz in-room, so a subwoofer is required for modern full-range reproduction. The impedance dips to about 4 ohms, reducing the practical amplifier advantage implied by its sensitivity. Pronounced directivity mismatch at the driver transitions, impedance/response resonances and elevated distortion spikes around the crossover remain audible concerns that EQ cannot fully solve. At 102dB Erin measured roughly 1.5dB midband compression; at 96dB distortion rises around crossover. Performance is difficult to justify at the price, and Erin explicitly did not recommend it.
Full Klipsch Heresy IV review and specifications →
| Bass Extension (-3dB) | 77Hz (measured, Erin's Audio Corner) |
|---|---|
| Dimensions | 24.8"H x 15.6"W x 13.3"D |
| Drivers | 1" horn-loaded tweeter; 1.75" horn-loaded midrange; 12" woofer |
| Impedance | Approximately 4 ohms minimum (measured, Erin's Audio Corner) |
| Sensitivity | 94.5dB/2.83V/1m (measured, Erin's Audio Corner) |
| Weight | 45 lb each |
| Woofer Cabinet | ported, rear |
As an eBay Partner, we may be compensated if you make a purchase.
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Klipsch Heresy IV vs Klipsch Forte IV
- Klipsch Heresy IV vs KEF Q11 Meta
- Klipsch Heresy IV vs Definitive Technology BP-9020
- Klipsch Heresy IV vs Klipsch RP-5000F II
- Klipsch Heresy IV vs SVS Ultra Evolution Pinnacle
- Klipsch Heresy IV vs Polk Reserve R500
- Klipsch Heresy IV vs ELAC DF63
- Klipsch Heresy IV vs PSB Imagine T65
- See all 14 comparisons