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The Kicker 51KSS6904 is a KS Series 6x9" 2-way component speaker system, rated at 150W RMS, featuring 1" silk-dome tweeters and polypropylene woofers — suitable for parcel shelf or door installs.
Other sizes in the KS 2-way component range: the 5.25" KSS504, 6.5" KSS6504 and 6.75" KSS6704.
Key specifications
- Woofer: 6x9" (160 x 230 mm) polypropylene
- Tweeter: 1" (25 mm) silk dome
- Power: 150W RMS, 300W peak
- Impedance: 4 ohms
- Sensitivity: 92 dB (1W/1m)
- Frequency response: 35Hz–21kHz
- Woofer mounting: 143 x 215 mm hole, 81 mm depth
- Crossover: 12dB high-pass at 4,000Hz, tweeter attenuation 0/4.5/9dB
KS 6x9" (160 x 230mm) Component Speaker System
51KSS6904
KS Series speakers handle high volumes while retaining smooth, detailed sound. Internally dampened polypropylene cones and rubber surrounds deliver precise midrange and bass, while silk-dome tweeters produce natural, detailed highs.
Use them as a component system with separate tweeters, or as a high-end coaxial system. The woofer's removable bullet-style phase plug can be replaced with a special adapter, allowing the 25mm silk-dome tweeters to rotate and tilt — giving more installation options and better off-axis performance. Recommended power: 15–150W.
Features
- High power handling
- Silk-dome tweeters for smooth, detailed highs
- Polypropylene woofer with rubber surrounds
- Thin-mount design fits behind factory grilles
- Four tweeter mounting options
- Articulating tweeter pod included
- Compact crossover for easier mounting
- Grilles included
Explore the full range in Kicker KS Series Speakers.
Specification
| Woofer Size (in) | 6x9" |
|---|---|
| Tweeter Size (in) | 1" |
| Style | Component |
| Impedance | (Ohms) 4 |
| RMS Power (W) | 150 |
| Peak Power (W) | 300 |
| Sensitivity | (dB @ 1W/1m) 92 |
| Frequency Response | (Hz) 35-21k |
| Dome Material | Silk |
| Depth (cm) | 8.1 |
| Woofer Mounting Hole Diameter [in, mm] | 5-5/8 x 8-7/16 , 143x215 |
| Woofer Bottom Mount Depth [in, mm] | 3-3/16 , 81 |
| Flush Mount Tweeter Depth [in,mm] | 11/16 , 17 |
| High Pass [dB], at Frequency [Hz] | 12, 4,000 |
| Low Pass [dB], at Frequency [Hz] | none |
| High Frequency Output Attenuation [dB] | 0, 4.5, 9 |
More specs
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What's Included
- Kicker 51KSS6904
Kicker
About the Kicker 51KSS6904
From our tech experts at CEN
The Kicker 51KSS6904 is a KS Series 6x9" 2-way component speaker system rated at 150W RMS (300W peak). It pairs polypropylene woofers and rubber surrounds with 1" silk-dome tweeters, and comes with a compact crossover, articulating tweeter pod, and grilles. Sensitivity is 92dB and frequency response runs from 35Hz to 21kHz.
Who it suits
These suit anyone upgrading a 6x9" position who wants separate tweeter placement for better stereo imaging. They can also be used as a high-end coaxial system. For a coaxial 6x9" alternative, see the Kicker 46CSC6934 CS Series.
Our tech experts advise
The woofer cut-out requires 143 x 215mm with 81mm depth — measure your space before ordering. Recommended amplifier power is 15–150W into 4 ohms. The crossover offers 0, 4.5 and 9dB tweeter attenuation settings to balance the highs to your preference. Component speaker installation is priced per vehicle; see our Nottingham fitting service for details.
Explore the full Kicker range at CEN, with fast UK dispatch and expert advice from our Nottingham team. Shop all Kicker
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Frequently Asked Questions
Q: Will these speakers fit my car?
A: Most car speakers are standard sizes, but mounting depth and fitting rings vary by vehicle. Check the size in the Specification tab against your vehicle, or contact CEN with your registration and we will confirm fitment and any adapters or fitting kits you need.
Q: Do I need an amplifier to run these speakers?
A: Not always. Most speakers will run from a standard head unit, but a dedicated amplifier lets them perform at their best, particularly for component sets and higher power handling models. The RMS figure in the Specification tab is the guide to how much clean power they can use.
Q: What is the difference between coaxial and component speakers?
A: Coaxial speakers combine the tweeter and woofer in one unit for a simple like-for-like upgrade. Component sets separate the tweeter and woofer with a crossover for better imaging and detail, and suit installs where sound quality is the priority.
Q: Do these come as a pair?
A: Unless stated otherwise, car speakers are sold in pairs. Check the product title and What's Included tab, which lists exactly what is in the box.
Q: Can CEN fit these speakers for me?
A: Yes. CEN offers professional installation from our Nottingham premises. Contact us to book an installation slot or ask for a fitting quote.
Q: How much power does the Kicker KSS6904 handle?
A: It is rated at 150 watts RMS and 300 watts peak at 4 ohms, with a recommended amplifier power of 15 to 150 watts.
Q: What is the mounting depth of the KSS6904 woofer?
A: The woofer bottom mount depth is 81 mm and it needs a 143 x 215 mm mounting hole.
Q: Can the KSS6904 be used as a coaxial speaker?
A: Yes. The removable phase plug is replaced with an adapter so the 25 mm tweeter can sit on the woofer, rotate and tilt.
