Infinity Primus 503F
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Infinity Primus 503F 5.25" 2-Way Coaxial Car Speakers
Product Overview:
The Infinity Primus 503F is a 5-1/4" coaxial speaker designed as a direct high-fidelity upgrade for factory car audio systems. Part of the refreshed Primus line, these speakers focus on compact fitment, high sensitivity, and the signature "lifelike" sound Infinity is known for. They are particularly effective in vehicles with low-power factory head units that need a boost in clarity and volume.
Key Features
Plus One™ Woofer Cones
Infinity uses its patented Plus One™ polypropylene cones, which extend the cone surface area closer to the edge of the basket. This provides up to 35% more radiating surface area than other speakers in the same size class, resulting in deeper bass response and higher efficiency without needing a larger mounting hole.
Edge-Driven Silk Dome Tweeters
Unlike cheaper balanced-dome tweeters, the 503F features edge-driven silk dome tweeters. This design provides a broader high-frequency dispersion and smoother response, ensuring that vocals and high-frequency details remain crisp and natural even at high volume levels.
True 4-Ohm Architecture
These speakers utilize a 3-ohm low-impedance voice coil. This design is engineered to compensate for the high resistance found in thin factory speaker wiring, allowing your head unit or amplifier to deliver more power. This "true 4-ohm" setup safely extracts every watt possible for a stronger, clearer sound.
Vented Basket Design
The super-rigid vented basket does more than just look sleek; it acts like a fan to wick heat away from the motor structure as the cone moves. This cooling effect results in lower distortion at high output levels and increases the overall longevity of the speaker components.
Technical Specifications
| Category | Specification |
| Performance | |
| Speaker Size | 5-1/4" (130mm) |
| Power Handling | 40W RMS / 120W Peak |
| Nominal Impedance | 3.0 Ohms |
| Frequency Response | 75Hz – 20kHz |
| Sensitivity (2.83V@1m) | 91 dB |
| Construction | |
| Woofer Material | Polypropylene with Rubber Surround |
| Tweeter Material | Edge-driven Silk Dome |
| Crossover Point | 6kHz @ 6dB/octave |
| Dimensions | |
| Mounting Depth | 1-13/16" |
| Cutout Diameter | 5-1/8" |
What Others Are Saying
Eddie was great - SDCS installed a new head unit in my 2019 4Runner. He was honest in his opinions regarding the options I was considering. Pricing was also good - he was able to reuse some of my existing installation kit so I saved a bit of $$.Installation was clean and fast and he took the time to walk through the features before I left. Highly recommend!!
I had a great time at this shop! The staff really knows their stuff and took the time to explain the different options without pressure. Installation was quick, clean and professional. Everything looks factory and sounds amazing. The prices were fair and customer service was above and beyond. I highly recommend this place if you're looking for quality car audio and excellent service.
Those guys are really professional! I had a new Alpine floating head unit installed in my 2008 Mercedes, and it feels like a brand-new car. The installation was super clean. At first, the sound wasn’t the same as the factory stereo, but Kevin tuned it to be just as good—if not better—without adding any new amps. They even used my factory GPS antenna so I don’t have extra wires hanging out. On top of that, they matched the online price. Big thanks to Kevin and Eddie—highly recommended!
Kevin was awesome, he took his time and explained everything to me. I went in initially for a dash cam install and then decided to get a sub and amp installed as well. Both turned out great and will be returning if I need more work done.
Came In not knowing what to expect when suddenly my stereo stopped working. Spoke with Kevin in the front and after a VERY fast diagnosing they discovered my wiring was incorrect. After only about 45 minutes total being in the store I was on my way to the beach with a working stereo again! Thank you so much SDCARSTEREO
Highly recommend Kevin and the team at San Diego Car Stereo for any issues with aftermarket stereos. I bought a car with an aftermarket stereo and AC unit that wasn’t working properly—specifically, the heat wasn’t functioning due to an improper setup. I had several people look at it with no luck, and even the dealership basically refused to help because it was an aftermarket install. I came to Kevin and his team over the holidays feeling pretty defeated, but he was confident he could get the heat working before I headed back to a Colorado winter. Sure enough, he got it done.
FAQ
Do products purchased from San Diego Car Stereo come with a warranty?
Yes, all products come with a 1-year manufacturer warranty unless otherwise stated. This covers any defects excluding physical damage.
Are these products brand new?
Yes, every product we sell is 100% brand new, unused, and comes in original manufacturer packaging unless clearly marked otherwise.
Do you offer installation services?
Yes, we offer professional installation services at both of our San Diego Car Stereo locations. Our expert technicians have over 50 years of combined experience to install all of your car, marine, or offroad audio needs. Stop by or give us a call to schedule an appointment to get a quote in person.