Short answer: the Miller & Kreisel IW150. Both are rated 3.6/5 for sound quality (#13 and #12 of 18 in-wall speakers), and the Miller & Kreisel IW150 costs $4,998 against $7,259.90 for the JBL Synthesis SCL-4, with sound quality a draw, the lower price decides it.
What the JBL Synthesis SCL-4 does well: JBL’s own measurements show a 1.85 directivity-index deviation, the most even directivity of the JBL Synthesis in-walls, with 0.35dB average on-axis deviation. The catch: Bass is the weakest here, at 83.7Hz for -3dB and about 61.9Hz for -10dB in free air, so it needs a subwoofer.
The case for the Miller & Kreisel IW150: Erin’s Audio Corner’s Klippel measurement shows well controlled directivity (SPDI deviation 2.43dB) and a smooth predicted in-room response, with a preference score of 2.88, or 6.32 with a perfect subwoofer. Watch for: Bass is thin: measured -3dB is 95.2Hz and -6dB is 82.0Hz, and Miller & Kreisel rates it only to 80Hz, so a subwoofer is required, and even with a perfect subwoofer the score reaches only 6.32.
Buy the Miller & Kreisel IW150. Both are rated the same for sound quality, and it costs $2,261.90 less than the JBL Synthesis SCL-4.
Still deciding? The full Passive Home rankings cover every ranked option.
Specifications Side By Side
| JBL Synthesis SCL-4 | Miller & Kreisel IW150 | |
|---|---|---|
| Price | $7,259.90 per pair | $4,998 per pair |
| Ranked | #12 of 18 in In-Wall & In-Ceiling Speakers | #13 of 18 in In-Wall & In-Ceiling Speakers |
| Drivers | 7” aluminum matrix cone woofer, 1” 2409H compression driver on HDI horn (2-way) | 2x 5.25” polypropylene bass/midrange drivers, 3x 1” soft fabric dome tweeters |
| Enclosure | In-wall, integrated MDF back box | In-wall |
| Dimensions | 25”H x 16.1”W x 3.7”D (636 x 409 x 93 mm) | 13.9”H x 12.2”W (354 x 311 mm) baffle (95mm mounting depth) |
| Weight | 27.6 lbs (12.51 kg) | 18.7 lbs (8.5 kg) |
| Sensitivity | 91dB (2.83V/1m) | 90dB |
| Impedance | 6 ohms | 4 ohms |
| Power Handling | 200W RMS maximum recommended amplifier power | 25-400W recommended amplifier power |
| Frequency Response | 45Hz-33kHz -6dB (manufacturer, on-axis) | 80Hz-20kHz +/-3dB (manufacturer) |
| Crossover Frequency | 1.3kHz | - |
| Bass Extension (-3dB) | 83.7Hz (measured, JBL data on spinorama.org) | 95.2Hz (measured, Erin’s Audio Corner) |
| Bass Extension (-10dB) | 61.9Hz (measured, JBL data on spinorama.org) | 68.7Hz (measured, Erin’s Audio Corner) |
| Spinorama Preference Score | 3.56 | 2.88 |
| Spinorama Preference Score with Perfect Sub | 6.55 | 6.32 |
| DIY Kit | No | No |
| Mounting Cutout | - | 288W x 331H mm |
Related Speaker Comparisons
How JBL Synthesis SCL-4 compares with other leading options:
- Revel W228Be vs JBL Synthesis SCL-4
- JBL Synthesis SCL-3 vs JBL Synthesis SCL-4
- JBL Synthesis SCL-4 vs Revel W990
- JBL Synthesis SCL-4 vs Grimani Systems Rixos-L
- JBL Synthesis SCL-4 vs MartinLogan Tribute 5XW
Prices on this page were last checked September 26, 2026 at 11:14 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
JBL Synthesis SCL-4: $7,259.90 per pair Audio Advice eBay
Pros: JBL’s own measurements show a 1.85 directivity-index deviation, the most even directivity of the JBL Synthesis in-walls, with 0.35dB average on-axis deviation. The preference score rises from 3.56 to 6.55 with a subwoofer. A 7-inch aluminum woofer and 2409H compression driver on JBL’s imaging horn give 91dB sensitivity, and bi-wire and bi-amp terminals suit custom home theaters. Measured bass extension of 83.7Hz (-3dB).
Cons: Bass is the weakest here, at 83.7Hz for -3dB and about 61.9Hz for -10dB in free air, so it needs a subwoofer. Listening-window smoothness is 0.59 inside a 3.1dB reference band, and the data is manufacturer supplied and digitized from graphs. At $3630 each it costs twice as much as the better-measuring SCL-6.
Full JBL Synthesis SCL-4 review and specifications →
| Bass Extension (-10dB) | 61.9Hz (measured, JBL data on spinorama.org) |
|---|---|
| Bass Extension (-3dB) | 83.7Hz (measured, JBL data on spinorama.org) |
| Crossover Frequency | 1.3kHz |
| DIY Kit | No |
| Dimensions | 25”H x 16.1”W x 3.7”D (636 x 409 x 93 mm) |
| Drivers | 7” aluminum matrix cone woofer, 1” 2409H compression driver on HDI horn (2-way) |
| Enclosure | In-wall, integrated MDF back box |
| Frequency Response | 45Hz-33kHz -6dB (manufacturer, on-axis) |
| Impedance | 6 ohms |
| Power Handling | 200W RMS maximum recommended amplifier power |
| Sensitivity | 91dB (2.83V/1m) |
| Spinorama Preference Score | 3.56 |
| Spinorama Preference Score with Perfect Sub | 6.55 |
| Weight | 27.6 lbs (12.51 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
Miller & Kreisel IW150: $4,998 per pair Audiolab (authorized M&K dealer) eBay
Pros: Erin’s Audio Corner’s Klippel measurement shows well controlled directivity (SPDI deviation 2.43dB) and a smooth predicted in-room response, with a preference score of 2.88, or 6.32 with a perfect subwoofer. The unusual layout puts two 5.25” polypropylene woofers beside a column of three 1” soft dome tweeters, a design meant to give even coverage across a room from a single wall opening. It is rated at 90dB sensitivity, and Erin’s measurement computed a real 88.2dB, and it accepts 25-400W of amplifier power. Measured bass extension of 95.2Hz (-3dB).
Cons: Bass is thin: measured -3dB is 95.2Hz and -6dB is 82.0Hz, and Miller & Kreisel rates it only to 80Hz, so a subwoofer is required, and even with a perfect subwoofer the score reaches only 6.32. On-axis smoothness is 0.48 and on-axis deviation averages 0.62dB, so the midrange is rougher than the better in-wall designs. At $2499 each a stereo pair costs twice that. Erin describes it as discontinued from what he can tell, so stock may be limited to remaining inventory.
Full Miller & Kreisel IW150 review and specifications →
| Bass Extension (-10dB) | 68.7Hz (measured, Erin’s Audio Corner) |
|---|---|
| Bass Extension (-3dB) | 95.2Hz (measured, Erin’s Audio Corner) |
| DIY Kit | No |
| Dimensions | 13.9”H x 12.2”W (354 x 311 mm) baffle (95mm mounting depth) |
| Drivers | 2x 5.25” polypropylene bass/midrange drivers, 3x 1” soft fabric dome tweeters |
| Enclosure | In-wall |
| Frequency Response | 80Hz-20kHz +/-3dB (manufacturer) |
| Impedance | 4 ohms |
| Mounting Cutout | 288W x 331H mm |
| Power Handling | 25-400W recommended amplifier power |
| Sensitivity | 90dB |
| Spinorama Preference Score | 2.88 |
| Spinorama Preference Score with Perfect Sub | 6.32 |
| Weight | 18.7 lbs (8.5 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons