Short answer: the Definitive Technology ProMonitor 1000, though neither ranks well in its class. It ranks #156 of 168 bookshelf speakers by sound quality, rated 1.7/5, at $398.40. The Klipsch R-51M ranks #160, rated 1.6/5, at $289.99, $108.41 cheaper, which does not close the gap in sound quality. Both are rated below 3.0/5 among the 168 bookshelf speakers, so if sound quality matters, consider the Ascend Acoustics HTM-200SE2 instead, ranked #7 at $368.
What the Definitive Technology ProMonitor 1000 does well: Bass distortion is well controlled per the measurements, and the slow bass rolloff means it can be pushed fairly hard for its size. The catch: CEA2034 spinorama shows severely reduced bass energy between 40-120Hz, a directivity mismatch between the tweeter and woofer, and a severe resonance/interference issue around 14kHz.
The Klipsch R-51M is the deeper-bass pick. 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. Its bass reaches about 62Hz before falling 3dB, against 95Hz for the Definitive Technology ProMonitor 1000. 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.
Buy the Definitive Technology ProMonitor 1000. It is rated higher for sound quality, and the $108.41 you would save on the Klipsch R-51M does not close the gap.
Still deciding? The full Passive Home rankings cover every ranked option.
Specifications Side By Side
| Definitive Technology ProMonitor 1000 | Klipsch R-51M | |
|---|---|---|
| Price | $398.40 per pair | $289.99 per pair Passive |
| Ranked | #156 of 168 in Medium Size Bookshelf Speakers | #160 of 168 in Medium Size Bookshelf Speakers |
| Bass Extension (-3dB) | 95Hz (measured, Audio Science Review) | 62Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-10dB) | 80Hz (measured, Audio Science Review) | 48Hz (measured, Erin’s Audio Corner) |
| Drivers | 1” aluminum dome tweeter, 5.25” BDSS mid/woofer, 5.25” planar bass radiator | 1” aluminum LTS tweeter on 90x90 Tractrix horn, 5.25” spun-copper IMG woofer |
| Dimensions | 10.88H x 6.25W x 6.5D in | 13.3” x 7” x 8.5” (338 x 178 x 215 mm) |
| Weight | 7.3 lbs (3.29 kg) each | 11 lbs (5.0 kg) each |
| Frequency Response | 47Hz - 30kHz (Manufacturer specified) | 62Hz - 21kHz (+/- 3dB, Manufacturer specified) |
| Sensitivity | 86dB (2.83V/1m, measured, Audio Science Review - reviewer noted this vs. a manufacturer spec of 91dB) | 93dB (2.83V @ 1m) |
| Impedance | 8 ohms nominal | 8 ohms |
| Woofer Cabinet | passive radiator | - |
| Spinorama Preference Score | 3.2 (spinorama.org) | - |
| Spinorama Preference Score with Perfect Sub | 6.58 (spinorama.org) | - |
| DIY Kit | No | - |
| Crossover Frequency | - | 1660Hz |
| Passive | - | Yes |
Related Speaker Comparisons
How Definitive Technology ProMonitor 1000 compares with other leading options:
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- Klipsch RP-500M II vs Definitive Technology ProMonitor 1000
- Wharfedale Super Denton vs Definitive Technology ProMonitor 1000
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.
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The Two Speakers In Full
Definitive Technology ProMonitor 1000: $398.40 per pair Amazon eBay
Pros: Bass distortion is well controlled per the measurements, and the slow bass rolloff means it can be pushed fairly hard for its size. Ships with a footer that keeps the small cabinet planted despite its light weight. Measured bass extension of 95Hz (-3dB), with a measured sensitivity of 86dB.
Cons: CEA2034 spinorama shows severely reduced bass energy between 40-120Hz, a directivity mismatch between the tweeter and woofer, and a severe resonance/interference issue around 14kHz. Distortion at 96dB SPL was so bad the reviewer limited testing to 86dB. Direct comparison to a $118/pair Pioneer SP-BS22-LR left the reviewer calling the $199/pair ProMonitor 1000 “a bad experiment that should be forgotten” and concluding “there is nothing Pro about it.”
Full Definitive Technology ProMonitor 1000 review and specifications →
| Bass Extension (-10dB) | 80Hz (measured, Audio Science Review) |
|---|---|
| Bass Extension (-3dB) | 95Hz (measured, Audio Science Review) |
| DIY Kit | No |
| Dimensions | 10.88H x 6.25W x 6.5D in |
| Drivers | 1” aluminum dome tweeter, 5.25” BDSS mid/woofer, 5.25” planar bass radiator |
| Frequency Response | 47Hz - 30kHz (Manufacturer specified) |
| Impedance | 8 ohms nominal |
| Sensitivity | 86dB (2.83V/1m, measured, Audio Science Review - reviewer noted this vs. a manufacturer spec of 91dB) |
| Spinorama Preference Score | 3.2 (spinorama.org) |
| Spinorama Preference Score with Perfect Sub | 6.58 (spinorama.org) |
| Weight | 7.3 lbs (3.29 kg) each |
| Woofer Cabinet | passive radiator |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Definitive Technology ProMonitor 1000 vs Sehlin Helium
- Definitive Technology ProMonitor 1000 vs Klipsch Reference R-50M
- Definitive Technology ProMonitor 1000 vs Polk T15
- Definitive Technology ProMonitor 1000 vs Pioneer Elite SP-EBS73-LR
- Definitive Technology ProMonitor 1000 vs JBL Control 1 Pro
- Definitive Technology ProMonitor 1000 vs Fluance Signature HFS
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- Definitive Technology ProMonitor 1000 vs Klipsch Reference R-40M
- See all 35 comparisons
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