JL Audio C1-400x 4″ 2-Way Coaxial Speakers – Pair – #99040

Brand: JL Audio
Model Number: C1-400X
UPC: 699440990400
Model Number: C1-400X
UPC: 699440990400

JL Audio C1-400x 2-way Coaxial Car Audio Speakers #99040 – Pair

  • Injection-molded mineral-filled polypropylene woofer cone with rubber surround
  • 3/4″ aluminum edge-driven dome tweeter
  • Handles up to 35 watts RMS (50 watts peak power)
  • Frequency response: 64-24,000 Hz
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Product Description

Features & Specifications




JL Audio C1-400x 2-way Coaxial Car Audio Speakers #99040 – Pair

The JL Audio C1-400x are starter speakers like no other. C1-400x woofer drivers benefit from proprietary FEA modeling and JL Audio’s expertise in low-frequency driver design. This knowledge is used to create speakers that can play loudly, while maintaining a smooth, dynamic, low distortion sound. At the core of the C1-400x is a proprietary, stamped, steel 4-inch (100 mm) frame and a DMA-optimized motor system. A mineral-filled, injection-molded polypropylene cone is suspended with a rubber surround on the front, and a carefully engineered spider at the top of the voice coil, to precisely control motion and prevent impact between the voice coil and the back plate. Tinsel leads are carefully routed and attached to the spider to prevent fatigue and buzzing. These are the same kinds of features and materials normally found on much more expensive loudspeakers.

Equipped with a true, edge-driven, aluminum dome tweeter, C1 speakers stand further apart from others in its category with superior high-frequency clarity and definition. The tweeter’s design has inherently excellent off-axis response and high-frequency extension. It also benefits from the damping of a silk surround suspension and Ferrofluid in the voice coil gap, along with the superior strength of a neodymium magnet circuit. A true, 2nd order high-pass filter is employed to further enhance smoothness and improve power handling.

Starter speakers like no other

After an extensive tour of JL Audio HQ, their engineering and development team talked about the current JL Audio lineup and upcoming projects. Given all the work they’re doing with premium car audio, many were surprised by how excited they were for customers to hear their workhorse C1 Series speakers. Designed for drivers simply looking for a sensible factory speaker replacement, not necessarily an audiophile-grade solution. Every JL Audio speaker must uphold the quality and sound associated with the name. You may be looking for something that’s just listenable, but what you’ll get with the JL Audio C1-400x is an audio experience that puts it at the top of its class. And then, just maybe, you’ll end up being a JL Audio fan for life.

What sets C1 apart?

JL Audio designed the JL Audio C1-400x speakers to be the very best they could be for the price. You’ll find solid construction and finish, along with some eye-popping flair in its striking yellow mineral-filled polypropylene woofer. That woofer delivers impactful lows and is specially designed for a natural roll-off transition to the highs handled by the tweeter. And it’s the aluminum edge-driven tweeter that gives the C1 Series its distinctive sound, setting it apart from other speakers at this price. You’ll hear crisp detail in the high frequencies, incredible imaging, and minimal distortion no matter how you power them.

Lineart Bottom-View and Side-View of C1-400x Coaxial Midrange with dimension labels A-E

Frame Outer Diameter* (A) 4.03 in / 102 mm
Grille Tray Outer Diameter (B) N/A
Motor Outer Diameter (C) 2.33 in / 59 mm
Frontal Coaxial Tweeter Protrusion** (D) 0.61 in / 16 mm
Frontal Grille Protrusion (E) N/A
Mounting Hole Diameter (F) 3.70 in / 94 mm
Mounting Depth (G) 1.81 in / 46 mm


Woofers: Each JL Audio C1 speaker features a mineral-filled, injection-molded polypropylene woofer cone with a rubber surround.

Tweeters: The 3/4″ edge-driven, aluminum dome tweeters are damped by a silk surround suspension.

4/2 Hole Compatibility: Most 4″ factory speakers use four mounting screws, however, in some vehicles, only two are used. The JL Audio C1-400x mounting tabs can be removed, allowing installation in 4-hole or 2-hole applications. Care should be taken handling the speaker after any tabs are removed because the broken edges may be sharp. Please enter your vehicle information to confirm fit.

Power Handling: JL Audio lists two power figures in the manual; 35 watts continuous power handling and recommended amp power 10-50 watts RMS. We’ve listed the RMS power recommendation in the specs table.

Brand JL Audio   Model JL Audio C1-400X
Product: JL Audio C1-400x 4″ 2-Way Coaxial Speakers – Pair – #99040

Speaker Size: 4"
Design: 2-way
Tweeter Design: 3/4" Edge-Driven Dome
Impedance: 4 Ohms
Tweeter Composition: Aluminum
Woofer Composition: Mineral-Filled injection-Molded
Woofer Surround: Rubber
Sensitivity (1W at 1 meter): 84.5
Sensitivity at 2.83 volts: 87.5
Frequency Response: 64 – 24k Hz
Minimum RMS Wattage: 10
Maximum RMS Wattage: 35
Peak Power Handling (Watts): 105
Top-mount Depth (Inches): 1 7/8
Cutout Diameter or Length (inches): 3 11/16
Mounting Height (Inches): 0.617


Speaker Design


RMS Power

Speaker Sensitivity

Speaker Size

Tweeter Size

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JL Audio 1 Year Limited Warranty