Short answer: the Klipsch R-51M, though neither ranks well in its class. It ranks #160 of 168 bookshelf speakers by sound quality, rated 1.6/5, at $289.99. The Klipsch Reference R-40M ranks #164, rated 1.4/5, at $199.99, $90 cheaper, not enough of a saving to outweigh the sound-quality gap. Both are rated below 3.0/5 among the 168 bookshelf speakers, so if sound quality matters, consider the Neumi BS5 instead, ranked #38 at $139.99.
Why pick the Klipsch R-51M: A high-efficiency 5.25-inch passive bookshelf speaker featuring Klipsch’s 90 x 90 square Tractrix horn mated to a 1-inch aluminum LTS tweeter and spun-copper IMG woofer. Watch for: Anechoic NFS measurements from Erin’s Audio Corner and ASR reveal significant tonal colorations: a sharp treble boost between 2kHz and 6kHz combined with a recessed upper midrange creates a bright, sibilant presentation that causes listener fatigue over time.
Why pick the Klipsch Reference R-40M: The current next-generation 4-inch passive bookshelf speaker replacing the Klipsch R-41M. The catch: Awaiting published full NFS preference scores.
Buy the Klipsch R-51M. It is rated higher for sound quality, and the $90 you would save on the Klipsch Reference R-40M does not close the gap.
Worth knowing: the Klipsch Reference R-40M has not been measured yet. Its rating is estimated from related models, with a likely range of 1.2 to 1.6, so treat this verdict as provisional.
Want more options? Browse the full Passive Home rankings.
Specifications Side By Side
| Klipsch R-51M | Klipsch Reference R-40M | |
|---|---|---|
| Price | $289.99 per pair Passive | $199.99 per pair Passive |
| Ranked | #160 of 168 in Medium Size Bookshelf Speakers | #164 of 168 in Medium Size Bookshelf Speakers Estimated |
| Bass Extension (-3dB) | 62Hz (measured, Erin’s Audio Corner) | - |
| Bass Extension (-10dB) | 48Hz (measured, Erin’s Audio Corner) | - |
| Crossover Frequency | 1660Hz | 1770Hz |
| Dimensions | 13.3” x 7” x 8.5” (338 x 178 x 215 mm) | 11.7” x 5.7” x 8.5” (298 x 146 x 216 mm) |
| Drivers | 1” aluminum LTS tweeter on 90x90 Tractrix horn, 5.25” spun-copper IMG woofer | 1” aluminum LTS tweeter on edge-to-edge Tractrix horn, 4” spun-copper TCP woofer |
| Frequency Response | 62Hz - 21kHz (+/- 3dB, Manufacturer specified) | 71Hz - 21kHz (+/- 3dB, Manufacturer specified) |
| Impedance | 8 ohms | 8 ohms |
| Passive | Yes | Yes |
| Sensitivity | 93dB (2.83V @ 1m) | 91dB (2.83V @ 1m) |
| Weight | 11 lbs (5.0 kg) each | 7.1 lbs (3.2 kg) each |
Related Speaker Comparisons
More worthwhile head-to-heads for Klipsch R-51M:
- JBL Control 1 Pro vs Klipsch R-51M
- Klipsch Reference R-50M vs Klipsch R-51M
- Definitive Technology ProMonitor 1000 vs Klipsch R-51M
- Definitive Technology ProMonitor 1000 vs Klipsch Reference R-40M
- Klipsch Reference R-40M vs Klipsch R-41M
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.
As an eBay Partner, we may be compensated if you make a purchase.
The Two Speakers In Full
Klipsch R-51M: $289.99 per pair Passive Amazon eBay
Newer model: the Klipsch Reference R-50M, ranked higher, estimated 1.7/5, released 2022. See every Klipsch Reference generation.
Same family: the Klipsch R-41M (smaller bookshelf, ranked lower, rated 1.3/5).
Pros: A high-efficiency 5.25-inch passive bookshelf speaker featuring Klipsch’s 90 x 90 square Tractrix horn mated to a 1-inch aluminum LTS tweeter and spun-copper IMG woofer. Delivers high sensitivity (93dB @ 2.83V/1m) that allows it to achieve loud volume levels effortlessly even with low-powered budget amplifiers. Rear-firing Tractrix port provides clean, tight punch down to approximately 62Hz at -3dB, offering noticeably fuller low-end weight than the smaller 4-inch Klipsch R-41M. Measured bass extension of 62Hz (-3dB).
Cons: Anechoic NFS measurements from Erin’s Audio Corner and ASR reveal significant tonal colorations: a sharp treble boost between 2kHz and 6kHz combined with a recessed upper midrange creates a bright, sibilant presentation that causes listener fatigue over time. Requires aggressive DSP/EQ correction to achieve neutral tonal accuracy.
Full Klipsch R-51M review and specifications →
| Released | Nov 2018 (7 years ago) |
|---|---|
| Bass Extension (-10dB) | 48Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-3dB) | 62Hz (measured, Erin’s Audio Corner) |
| Crossover Frequency | 1660Hz |
| Dimensions | 13.3” x 7” x 8.5” (338 x 178 x 215 mm) |
| Drivers | 1” aluminum LTS tweeter on 90x90 Tractrix horn, 5.25” spun-copper IMG woofer |
| Frequency Response | 62Hz - 21kHz (+/- 3dB, Manufacturer specified) |
| Impedance | 8 ohms |
| Passive | Yes |
| Sensitivity | 93dB (2.83V @ 1m) |
| Weight | 11 lbs (5.0 kg) each |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Klipsch Reference R-40M: $199.99 per pair Passive Estimated Amazon eBay
Older model: the Klipsch R-41M (ranked lower, rated 1.3/5). See every Klipsch Reference generation.
Same family: the Klipsch Reference R-50M (larger bookshelf, ranked higher, estimated 1.7/5), the Klipsch Reference R-600F (smaller floorstanding, estimated 1.8/5), the Klipsch Reference R-800F (larger floorstanding, estimated 1.9/5), the Klipsch Reference R-30C (smaller center, estimated 3.4/5) and the Klipsch Reference R-50C (larger center, estimated 3.5/5).
Pros: The current next-generation 4-inch passive bookshelf speaker replacing the Klipsch R-41M. Features the updated edge-to-edge Tractrix horn mated to a 1-inch aluminum LTS tweeter and 4-inch spun-copper TCP woofer. High sensitivity (91dB) ensures easy drivability with any entry receiver.
Cons: Awaiting published full NFS preference scores. 4-inch woofer has natural bass roll-off below 71Hz, requiring a companion subwoofer for full-range listening.
Full Klipsch Reference R-40M review and specifications →
| Released | 2022 (4 years ago) |
|---|---|
| Crossover Frequency | 1770Hz |
| Dimensions | 11.7” x 5.7” x 8.5” (298 x 146 x 216 mm) |
| Drivers | 1” aluminum LTS tweeter on edge-to-edge Tractrix horn, 4” spun-copper TCP woofer |
| Frequency Response | 71Hz - 21kHz (+/- 3dB, Manufacturer specified) |
| Impedance | 8 ohms |
| Passive | Yes |
| Sensitivity | 91dB (2.83V @ 1m) |
| Weight | 7.1 lbs (3.2 kg) each |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons