In this review, we will be comparing IW Sub Reference and UIW RLS III, two Passive In-wall speakers by Definitive Technology Let's have a brief look at the main features
of Definitive IW Sub Reference and Definitive UIW RLS III first before getting into our more
detailed comparison.
Definitive IW Sub Reference Key Specs
- 1-way Design
- " Tweeter
- 13" Not given Woofer
- 14-200Hz Frequency Response
- --- Sensitivity
- Impedance: 4ohms
- Power Range:up to 275watts
- Dimensions (H x W x D): 639.0" x 14.3750" x 4.0000"( 639.0 x 366.0 x 102.0mm )
Definitive UIW RLS III Key Specs
- 2-way Design
- 1" Hard-Dome Tweeter
- 2 x 5.25" Polypropylene Woofer
- 24-30kHz Frequency Response
- 92 dB Sensitivity
- Impedance: 8ohms
- Power Range:10-325watts
- Dimensions (H x W x D): 604.0" x 5.8750" x 3.8750"( 604.0 x 150.0 x 99.0mm )
What size room are the Definitive IW Sub Reference and Definitive UIW RLS III 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 IW Sub Reference |
Definitive UIW RLS III |
| Near-field |
Poor |
Are you nuts? |
| Small Room |
Poor |
Bad |
| Mid-size Room |
Good |
Poor |
| Large Room |
Good |
Good |
| Very Large Room |
Average |
Good |
(* 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 IW Sub Reference and Definitive UIW RLS III 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
One of the fundamental differences between these two speakers is that IW Sub Reference is a 1-way design whereas the UIW RLS III is a 2-way speaker. 3-way designs utilize a midrange driver in addition to the tweeter and woofer on 2-way designs. Designing a crossover for a 3-way speaker is a complicated process and generally increases the overall cost of the speaker.
| Driver |
Definitive IW Sub Reference |
Definitive UIW RLS III |
|
Driver Setup
|
1-way
|
2-way
|
|
Tweeter
|
-inch
|
1-inch
|
|
Midrange
|
- |
- |
|
Woofer
|
1 x 13-inch
|
2 x 5.25-inch
|
IW Sub Reference features a " Tweeter and 1 x 13" Not given Woofer . On the other hand, the UIW RLS III features a 1" Hard-Dome Tweeter and 2 x 5.25" Polypropylene Woofer .
Frequency Response
IW Sub Reference has a frequency range of 14-200Hz whereas UIW RLS III has a frequency range of 24-30kHz. With a minimum frequency of 14Hz, the IW Sub Reference can go significantly deeper on the low side and provide stronger bass compared to the UIW RLS III's min frequency of 24Hz.
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
Definitive IW Sub Reference
Impedance and Sensitivity
IW Sub Reference is a 4 ohms speaker compared to the UIW RLS III which has a nominal impedance of 8 ohms. Lower impedance speakers, especially the ones that are rated at 4 ohms may put more pressure on the amplifier unit especially when played at high volume levels, so make sure the amp you pair with the IW Sub Reference can provide this impedance level.
These two speakers also have different sensitivity levels. IW Sub Reference sensitivity is rated at --- and the UIW RLS III's is rated at 92 dB. This 92 dB difference makes the Definitive UIW RLS III a more sensitive speaker compared to Definitive IW Sub Reference, 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.
IW Sub Reference can handle a max power of 325 watts RMS from the amp the whereas IW Sub Reference has a max power handling value of 275 watts RMS , 50 watts less than the UIW RLS III.
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
IW Sub Reference features Spring post type posts and UIW RLS III 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 IW Sub Reference's and Definitive UIW RLS III's external dimensions. Definitive IW Sub Reference has external dimensions of 639.0 x 366.0 x 102.0mm ( 25.1250-inch x 14.3750-inch x 4.0000-inch) whereas Definitive UIW RLS III has external dimensions of 604.0 x 150.0 x 99.0mm ( 23.7500-inch x 5.8750-inch x 3.8750-inch) .
Definitive IW Sub Reference is clearly the larger of the two speakers. Its body is 216mm wider, 35mm taller and 3mm deeper than Definitive UIW RLS III.
What's in the Box of Definitive IW Sub Reference?
Here are the items that are included inside the box of IW Sub Reference:
In-wall subwooferGrille (attached)4 Long self-adhesive foam gaskets3 Short self-adhesive foam gaskets8 ScrewsWall-templatePaint maskOwners ManualOnline Product Registration card
What's in the Box of Definitive UIW RLS III?
Here are the items that come with the UIW RLS III:
In-wall loudspeakerGrilleSelf-adhesive foam gasketPaint maskWall-Mount TemplateOwners ManualOnline Product Registration Card
Woofer Size 
High Frequency Response 
Max Input Power 
Driver Setup 
Nominal Impedance 
Height 
Base Surface Area 
Price per pair*