In this review, we will be comparing UIW RSS II and CWM663, two Passive In-wall speakers from Definitive Technology and Bowers Wilkins. Let's have a brief look at the main features
of Definitive UIW RSS II and B&W CWM663 first before getting into our more
detailed comparison.
Definitive UIW RSS II Key Specs
- 2-way Design
- 1" Hard-Dome Tweeter
- 2 x 4.5" Polypropylene Woofer
- 26-30kHz Frequency Response
- 90 dB Sensitivity
- Impedance: 8ohms
- Power Range:10-250watts
- Dimensions (H x W x D): 296.0" x 9.8750" x 3.8750"( 296.0 x 251.0 x 99.0mm )
B&W CWM663 Key Specs
- 2-way Design
- 1" Soft-Dome Tweeter
- 6" Kevlar Woofer
- 45-50kHz Frequency Response
- 88 dB Sensitivity
- Impedance: 8ohms
- Power Range:25-150watts
- Dimensions (H x W x D): 280.0" x 7.2500" x 3.7500"( 280.0 x 185.0 x 96.0mm )
What size room are the Definitive UIW RSS II and B&W CWM663 speakers good for?
The size of the room in which you are planning to use these loudspeakers is an important decision factor. Here we have compared their suitability to various sizes of environments considering their size and max power parameters:
| Listening Environment* |
Definitive UIW RSS II |
B&W CWM663 |
| Near-field |
Poor |
Poor |
| Small Room |
Poor |
Average |
| Mid-size Room |
Good |
Good |
| Large Room |
Good |
Average |
| Very Large Room |
Average |
Poor |
(* Approximate Room sizes: Small < 100sq. ft / 9 m2, Mid-size: 100-220 sq. ft / 9-20 m2, Large 220-400 sq. ft / 20-36 m2, Very Large: > 400 sq. ft / 36 m2.
Average Floor Height: 9" / 2.7m. Typical room sizes differ from country to country, and the actual listening experience changes depending on floor height, room shape, surface materials, listening position, speaker locations, etc.)
In the following sections, we will get into more detail in order to better understand how the Definitive UIW RSS II and B&W CWM663 compare and hopefully end up with enough arguments to decide which one of these loudspeakers is the better choice for you.
**This post contains affiliate links, and I will be compensated if you make a purchase after clicking
through my links. As an Amazon Associate I earn from qualifying purchases.
Drivers
Both UIW RSS II and CWM663 are 2-way speakers.
| Driver |
Definitive UIW RSS II |
B&W CWM663 |
|
Driver Setup
|
2-way
|
2-way
|
|
Tweeter
|
1-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
2 x 4.5-inch
|
1 x 6-inch
|
UIW RSS II features a 1" Hard-Dome Tweeter and 2 x 4.5" Polypropylene Woofer . On the other hand, the CWM663 features a 1" Soft-Dome Tweeter and 1 x 6" Kevlar Woofer .
Frequency Response
UIW RSS II has a frequency range of 26-30kHz whereas CWM663 has a frequency range of 45-50kHz. With a minimum frequency of 26Hz, the UIW RSS II can go significantly deeper on the low side and provide stronger bass compared to the CWM663's min frequency of 45Hz.
Below graphs depict how these two speakers compare with the max, min and average values of the Min and Max Frequencies of other speakers in the In-wall class in our database.
Low Frequency
In-wall Speakers
High Frequency
In-wall Speakers
None of these speakers achieves full range experience which is commonly agreed as 20Hz-20kHz. In order to achieve lower lows / deeper bass, we recommend you pair these with a subwoofer. Visit our Powered Subwoofers section to find out more about the available options.
Impedance and Sensitivity
UIW RSS II and CWM663 have the same Impedance of 8 ohms but where they differ is the sensitivity levels. UIW RSS II sensitivity is rated at 90 dB and the CWM663's is at 88 dB. This 2 dB difference makes the Definitive UIW RSS II a more sensitive speaker compared to B&W CWM663, hence will play louder with the same amount of watts.
Sensitivity
In-wall Speakers
Power Range
Power
range is the range of input power in watts RMS that a loudspeaker is designed to handle. While using an amplifier within this range ensures the nominal performance , inputting a power that is higher than the max wattage can result in a damaged speaker.
UIW RSS II can handle a max power of 250 watts RMS from the amp the whereas CWM663 has a max power handling value of 150 watts RMS, 100 watts less than the UIW RSS II.
Keep in mind that a higher max power handling value doesn't necessarily make that a louder speaker
compared to a lower max handling speaker. Loudness or the sound level is also impacted by parameters
such as Impedance, sensitivity and system efficiencies.
Input Type and Bi-Amping / Bi-Wiring
UIW RSS II features Spring post type posts and CWM663 has a Spring post type posts. None of these speakers feature bi-amping/bi-wiring.
Physical Specs
Size of a speaker can sometimes become an important decision factor due to space constraints or in some cases purely for esthetic reasons. In this section, we are going to compare Definitive UIW RSS II's and B&W CWM663's external dimensions. Definitive UIW RSS II has external dimensions of 296.0 x 251.0 x 99.0mm ( 11.6250-inch x 9.8750-inch x 3.8750-inch) whereas B&W CWM663 has external dimensions of 280.0 x 185.0 x 96.0mm ( 11.0000-inch x 7.2500-inch x 3.7500-inch) .
Definitive UIW RSS II is clearly the larger of the two speakers. Its body is 66mm wider, 16mm taller and 3mm deeper than B&W CWM663.
What's in the Box of Definitive UIW RSS II?
Here are the items that are included inside the box of UIW RSS II:
In-wall/In-cieling bipolar speakerGrille7 Foam strips2 ScrewsPaint maskWall templateOwners ManualOnline Product Registration Card
What's in the Box of B&W CWM663?
Here are the items that come with the CWM663:
2 In-wall loudspeakers2 Mounting frames2 Grilles2 Paint mask2 Cut-out templatesQuick Start GuideTemplateWarranty Information
Max Input Power 
Sensitivity 
Number of Woofers 
Passive Radiator 
High Frequency Response 
Height 
Base Surface Area 
Price per pair*