Short answer: the JBL 708P for measured accuracy, the PSI Audio A21-M for an all-analog path. The 708P’s CEA2034 spinorama shows extremely good on- and off-axis response and excellent horizontal directivity, but a port resonance adds a mild rise around 600-900Hz and its vertical window is narrow. The A21-M skips DSP for a proprietary analog Coherent Phase Response circuit, though its bass alignment measures a Q of 0.96, close to a mild peak.
What the PSI Audio A21-M gets right: PSI Audio deliberately skips DSP entirely, using a proprietary Coherent Phase Response analog circuit to keep phase alignment accurate without adding conversion stages, tracing its design back to the Studer A3 studio monitor. Set against that: The bass alignment measures a Q of 0.96, close to the point where a port tuned system starts to show a mild peak rather than a clean rolloff, worth knowing if placed near a wall.
Buy the PSI Audio A21-M. It is rated higher for sound quality, and the $3,440 you would save on the JBL 708P does not close the gap.
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Specifications Side By Side
| PSI Audio A21-M | JBL 708P | |
|---|---|---|
| Price | $7,440 per pair | $4000 per pair |
| Ranked | #19 of 68 in Large Size Powered Bookshelf Speakers | #39 of 68 in Large Size Powered Bookshelf Speakers |
| Enclosure | ported | - |
| Drivers | 27mm handmade dome tweeter, 172mm cone woofer | 8” woofer, 2409H 1” compression driver |
| Dimensions | 15.7”H x 9.8”W x 11.8”D (400 x 250 x 300 mm) | 17.2”H x 9.8”W x 11.5”D (438 x 248 x 292 mm) |
| Weight | 28.2 lbs (12.8 kg) each | 25.1 lbs (11.4 kg) each |
| Amplifier Power | 335W total (280W woofer, 55W tweeter, Class A/B) | 500W total (250W woofer, 250W tweeter) |
| Frequency Response | 38Hz-23kHz -6dB | 41Hz - 25kHz (+/-3dB) (Manufacturer specified) |
| Bass Extension (-3dB) | 39.6Hz (measured, Audio Science Review) | 43.9Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-10dB) | 33.2Hz (measured, Audio Science Review) | 35.6Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) |
| Crossover Frequency | 2.4kHz | - |
| Warranty | 5+1 years | - |
| Country | Switzerland | - |
| Maximum SPL | 110dB short term, 121dB peak (manufacturer specified) | - |
| Spinorama Preference Score | 6.07 | 5.03 |
| Spinorama Preference Score with Perfect Sub | 7.72 | 6.91 |
| Inputs | XLR (balanced analog) | XLR/TRS combo (analog), XLR AES3 (digital) |
| XLR Input | Yes | Yes |
| RCA Input | No | No |
| TRS Input | No | Yes |
| Optical Input | No | No |
| Coaxial Input | No | No |
| USB Input | No | No |
| HDMI Input | No | No |
| AES Input | No | Yes |
| Aux Input | No | No |
| Bluetooth | No | No |
| App | - | No |
| EQ | - | No |
| DSP | - | No |
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Prices on this page were last checked October 3, 2026 at 10:26 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
PSI Audio A21-M: $7,440 per pair B&H Photo Video eBay
Pros: ASR measured 39.6Hz -3dB extension and a 2.2dB response span from 300Hz to 5kHz, giving useful bass and broadly even mids. Its 7.72 ideal-subwoofer score supports serious monitoring, with analog phase compensation offering an alternative to DSP-based systems. Measured bass extension of 39.6Hz (-3dB).
Cons: The measured tonal result is good rather than a clear advance over less costly competitors. There is no built-in automatic room-calibration system, so placement or external correction still matters. The premium construction and analog circuitry should not be mistaken for proof of better audible performance.
Full PSI Audio A21-M review and specifications →
| AES Input | No |
|---|---|
| Amplifier Power | 335W total (280W woofer, 55W tweeter, Class A/B) |
| Aux Input | No |
| Bass Extension (-10dB) | 33.2Hz (measured, Audio Science Review) |
| Bass Extension (-3dB) | 39.6Hz (measured, Audio Science Review) |
| Bluetooth | No |
| Coaxial Input | No |
| Country | Switzerland |
| Crossover Frequency | 2.4kHz |
| Dimensions | 15.7”H x 9.8”W x 11.8”D (400 x 250 x 300 mm) |
| Drivers | 27mm handmade dome tweeter, 172mm cone woofer |
| Enclosure | ported |
| Frequency Response | 38Hz-23kHz -6dB |
| HDMI Input | No |
| Inputs | XLR (balanced analog) |
| Maximum SPL | 110dB short term, 121dB peak (manufacturer specified) |
| Optical Input | No |
| RCA Input | No |
| Spinorama Preference Score | 6.07 |
| Spinorama Preference Score with Perfect Sub | 7.72 |
| TRS Input | No |
| USB Input | No |
| Warranty | 5+1 years |
| Weight | 28.2 lbs (12.8 kg) each |
| XLR Input | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
JBL 708P: $4000 per pair B&H Photo Video eBay
Pros: Erin’s measurements give 43.9Hz -3dB extension and a 6.91 ideal-subwoofer score, with useful bass from a professional active monitor. The waveguide and onboard processing make it a practical choice for a carefully installed studio system. Measured bass extension of 43.9Hz (-3dB).
Cons: The 2.6dB response span from 300Hz to 5kHz includes audible-relevance irregularities, with port-region features and vertical crossover sensitivity. High-level distortion remains a constraint. Its professional positioning and amplifier power do not make it automatically more neutral than the cheaper 308P MKII. A port resonance adds a mild rise around 600 to 900Hz, and vertical dispersion is narrower than horizontal, so stay within a few degrees of the tweeter axis.
Full JBL 708P review and specifications →
| AES Input | Yes |
|---|---|
| Amplifier Power | 500W total (250W woofer, 250W tweeter) |
| App | No |
| Aux Input | No |
| Bass Extension (-10dB) | 35.6Hz (derived, log-interpolated between spinorama.org -9dB/-12dB points) |
| Bass Extension (-3dB) | 43.9Hz (measured, Erin’s Audio Corner) |
| Bluetooth | No |
| Coaxial Input | No |
| DSP | No |
| Dimensions | 17.2”H x 9.8”W x 11.5”D (438 x 248 x 292 mm) |
| Drivers | 8” woofer, 2409H 1” compression driver |
| EQ | No |
| Frequency Response | 41Hz - 25kHz (+/-3dB) (Manufacturer specified) |
| HDMI Input | No |
| Inputs | XLR/TRS combo (analog), XLR AES3 (digital) |
| Optical Input | No |
| RCA Input | No |
| Spinorama Preference Score | 5.03 |
| Spinorama Preference Score with Perfect Sub | 6.91 |
| TRS Input | Yes |
| USB Input | No |
| Weight | 25.1 lbs (11.4 kg) each |
| XLR Input | Yes |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons