Short answer: the Monolith THX-365IW. It ranks #7 of 18 in-wall speakers by sound quality, rated 4.0/5, at $999.98; the KEF CI200RR-THX ranks #9, rated 3.7/5, and costs $2,399.98, which makes this an easy call rather than a real tradeoff.
What the Monolith THX-365IW does well: Audio Science Review’s retest measured a preference score of 5.23, or 7.64 with a perfect subwoofer, with -3dB at 54.6Hz and -6dB at 42.8Hz, deep bass for an in-wall speaker. The tradeoff: ASR’s first measurement of this speaker scored far lower (preference score 1.33, or 5.10 with a subwoofer, with -3dB at 108Hz), so results depend heavily on how it is installed and enclosed.
The case for the KEF CI200RR-THX: An 8” woofer paired with a 1.5” Uni-Q tweeter (crossing over at 2.2kHz) measures a genuine 82.5Hz at -3dB and roughly 30.5Hz at -10dB, respectable low-end reach for a mid-priced in-ceiling speaker. The catch: Spinorama’s measurement of this model is a lower-confidence manufacturer curve rather than an independently verified Klippel scan, so treat the extension figures as directionally useful rather than as precise as the ASR-measured entries in this category.
Buy the Monolith THX-365IW. It is rated higher for sound quality than the KEF CI200RR-THX and costs less, so only choose the other one for a particular feature it does better.
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Specifications Side By Side
| Monolith THX-365IW | KEF CI200RR-THX | |
|---|---|---|
| Price | $999.98 per pair | $2,399.98 per pair |
| Ranked | #7 of 18 in In-Wall & In-Ceiling Speakers | #9 of 18 in In-Wall & In-Ceiling Speakers |
| Drivers | 2x 6.5” high-excursion long-fiber pulp cone woofers, 2” silk dome midrange, 1” silk dome tweeter (3-way) | 8” woofer, 1.5” Uni-Q tweeter (2.2kHz crossover) |
| Enclosure | In-wall, passive 3-way with dog-ear mounting tabs | Open-backed, in-ceiling |
| Dimensions | 22.7”H x 11.1”W x 3.8”D (577 x 282 x 97 mm) | 11.4” x 11.4” x 5.2” (290 x 290 x 132.6 mm) (126.5mm mounting depth) |
| Weight | 19.6 lbs (8.9 kg) | 7.9 lbs (3.6kg) |
| Sensitivity | 89.5dB | 90dB |
| Impedance | 4 ohms nominal (about 2.9 ohm minimum) | 4 ohms |
| Power Handling | 160W maximum | 10-190W recommended amplifier power |
| Crossover Frequency | 550Hz, 1,900Hz (4th-order Linkwitz-Riley) | - |
| Warranty | 5 years | - |
| Certification | THX Ultra | THX |
| Bass Extension (-3dB) | 54.6Hz (measured, Audio Science Review) | 82.5Hz (measured, spinorama.org vendor data) |
| Bass Extension (-10dB) | 31.1Hz (measured, Audio Science Review) | 30.5Hz (measured, spinorama.org vendor data) |
| Spinorama Preference Score | 5.23 | - |
| Spinorama Preference Score with Perfect Sub | 7.64 | - |
| DIY Kit | No | No |
| Mounting Cutout | - | 238mm (9.37 in) |
| Frequency Response | - | 33Hz-28kHz +/-6dB (manufacturer, open-backed) |
Related Speaker Comparisons
More top alternatives to Monolith THX-365IW:
- Revel W553L vs Monolith THX-365IW
- Monolith THX-365IW vs JBL Synthesis SCL-7
- Monolith THX-365IW vs KEF CI130.2CR
- KEF CI200RR-THX vs KEF CI130.2CR
- KEF CI200RR-THX vs KEF CI50R
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
Monolith THX-365IW: $999.98 per pair Amazon Monoprice eBay
Pros: Audio Science Review’s retest measured a preference score of 5.23, or 7.64 with a perfect subwoofer, with -3dB at 54.6Hz and -6dB at 42.8Hz, deep bass for an in-wall speaker. Directivity is well controlled (SPDI deviation 2.09dB) and on-axis smoothness is 0.70. It is a THX Ultra certified three-way, with two 6.5” woofers, a dedicated 2” silk dome midrange and a 1” silk dome tweeter, rated at 89.5dB sensitivity, which ASR’s measurement confirmed at 89.4dB. The 5-year warranty is longer than most in-wall speakers get. Measured bass extension of 54.6Hz (-3dB).
Cons: ASR’s first measurement of this speaker scored far lower (preference score 1.33, or 5.10 with a subwoofer, with -3dB at 108Hz), so results depend heavily on how it is installed and enclosed. Monoprice positions it for rear and surround channels and suggests in-room speakers up front, and the ASR reviewer said he would pick something better for a front left or right. Impedance dips to about 2.9 ohms, so the amplifier needs to be comfortable with a low load. At $500 each a stereo pair costs twice that.
Full Monolith THX-365IW review and specifications →
| Bass Extension (-10dB) | 31.1Hz (measured, Audio Science Review) |
|---|---|
| Bass Extension (-3dB) | 54.6Hz (measured, Audio Science Review) |
| Certification | THX Ultra |
| Crossover Frequency | 550Hz, 1,900Hz (4th-order Linkwitz-Riley) |
| DIY Kit | No |
| Dimensions | 22.7”H x 11.1”W x 3.8”D (577 x 282 x 97 mm) |
| Drivers | 2x 6.5” high-excursion long-fiber pulp cone woofers, 2” silk dome midrange, 1” silk dome tweeter (3-way) |
| Enclosure | In-wall, passive 3-way with dog-ear mounting tabs |
| Impedance | 4 ohms nominal (about 2.9 ohm minimum) |
| Power Handling | 160W maximum |
| Sensitivity | 89.5dB |
| Spinorama Preference Score | 5.23 |
| Spinorama Preference Score with Perfect Sub | 7.64 |
| Warranty | 5 years |
| Weight | 19.6 lbs (8.9 kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
KEF CI200RR-THX: $2,399.98 per pair Amazon eBay
Pros: An 8” woofer paired with a 1.5” Uni-Q tweeter (crossing over at 2.2kHz) measures a genuine 82.5Hz at -3dB and roughly 30.5Hz at -10dB, respectable low-end reach for a mid-priced in-ceiling speaker. The 238mm cutout accepts a large enough driver to move real air in a family room or media room. At $1200 each, it costs about half of KEF’s flagship Ci3160RLM-THX while carrying the same THX certification. Measured bass extension of 82.5Hz (-3dB).
Cons: Spinorama’s measurement of this model is a lower-confidence manufacturer curve rather than an independently verified Klippel scan, so treat the extension figures as directionally useful rather than as precise as the ASR-measured entries in this category. No Harman-style preference score has been published for it.
Full KEF CI200RR-THX review and specifications →
| Bass Extension (-10dB) | 30.5Hz (measured, spinorama.org vendor data) |
|---|---|
| Bass Extension (-3dB) | 82.5Hz (measured, spinorama.org vendor data) |
| Certification | THX |
| DIY Kit | No |
| Dimensions | 11.4” x 11.4” x 5.2” (290 x 290 x 132.6 mm) (126.5mm mounting depth) |
| Drivers | 8” woofer, 1.5” Uni-Q tweeter (2.2kHz crossover) |
| Enclosure | Open-backed, in-ceiling |
| Frequency Response | 33Hz-28kHz +/-6dB (manufacturer, open-backed) |
| Impedance | 4 ohms |
| Mounting Cutout | 238mm (9.37 in) |
| Power Handling | 10-190W recommended amplifier power |
| Sensitivity | 90dB |
| Weight | 7.9 lbs (3.6kg) |
- Links
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons