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JL Audio Stealthbox Subwoofer Upgrade Kit (15-20 Fastback)

Item 393861
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Market Price $918.99 You Save 4% ($39.00)
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$879.99 (each)

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      Review & Installation Video

      Product Information

      Features, Description, Reviews, Q&A, Specs & Installation


      • Upgrade for Mustang Audio
      • Replaces Stock Subwoofer (If Fitted)
      • Provides Huge Extra Bass
      • Sealed Enclosure
      • Handles Up to 400W
      • Easy Installation
      • Two-Year JL Audio Limited Warranty
      • Fits All 2015–2020 Ford Fastback Mustangs


      Give Your Stang Some Serious Bass. If you’re not feeling it from your Fastback Mustang’s stock audio system, it may be time to invest in some serious bass power. The JL Audio Stealthbox is a sealed enclosure design that simply fits in the location normally used by the optional Ford factory subwoofer. The built-in 12 inch subwoofer driver handles up to 400W, pumping out powerful, deep bass.

      All Fiberglass Construction. The Stealthbox is built from rugged, sturdy fiberglass, creating a sealed enclosure that is tuned to work in your Mustang. The front face is finished in a hard-wearing fabric that fits right into the trunk of your car. The enclosed 12 inch subwoofer driver features a cast alloy frame, rugged polyropylene cone, and long-lasting rubber surround.

      Installs Easily. The Stealthbox simply fits into the same place in your Mustang as the optional factory subwoofer. No drilling or cutting is needed. Any factory subwoofer must be removed.

      Two-Year Limited Warranty. JL Audio provides a limited two-year warranty on the Stealthbox.

      Application. The JL Audio Stealthbox Subwoofer Upgrade Kit fits all 2015 to 2020 Ford Mustang Fastback models.

      Technical Note. If you have a Mustang that was not equipped with a factory subwoofer, you will need additional speaker wire to install the Stealthbox properly.

      Fitment: 2015 2016 2017 2018 2019 2020 Details

      MPN# 94617

      CA Residents: WARNING: Cancer and Reproductive Harm -


      Customer Reviews (8)

      Write a Review

      Ratings Summary

      4.6 out of 5 overall rating from 8 customers

      • October 21, 2019

        4 2018 EcoBoost - ecoboosted

        some modification required

        sounds good, fits well but I had to enlarge the holes to get the mounting studs to line up. Grill keeps falling off, I just put some clear silicone on it to see if that will get it to stay on. At this price I should not have had these issues. shipping was super fast from AM.

        Helpful (2)
      • August 31, 2019

        3 2019 GT - Bea911

        Terrible Fitment.

        I will say the reviews I read about the install were dead on. This is not my first stealthbox and must say I was very disappointed in the difficulty with the install. It was impossible to get the box on as described in the instructions. I followed what others did and threaded the bolts front m inside the box. My other issue is there was a lot of leftover fiberglass around the mounting holes inside the box. I had to use a disc sander to clean up the inside just so I could get the nut on. IMO this box cost way too much money to have these kind of issues. Once you get the darn thing in it sounds as you would expect a JL sub to sound no complaints there.

        Helpful (4)
      • August 25, 2019

        5 2019 GT - DariusS

        Awesome JL Audio

        Great investment for your 2019 mustang gt and the sound quality is awesome a bit pricey but good product..

        Helpful (3)
      • June 18, 2019

        5 2016 GT - NGGM1

        Great Sound, Custom Fit!

        Well I was hesitant to buy this at first, but after seeing one in person, I had to buy it. Looks better than the factory installed sub and sounds a lot better as well. Best option not to lose a lot of trunk space. If they made one for the driver side, I would buy it as well. Solid build quality.

        Helpful (1)
      • June 26, 2018

        5 2018 GT - Mrc2u

        Great sound and fit

        amazing sound from this unit. complete factory look and still have space in the trunk!

        Helpful (17)
      • June 13, 2018

        5 2018 GT - RaymondH


        Great product and service. The product fits perfectly in the mustang.

        Helpful (13)
      • May 29, 2018

        5 2016 GT - Luna78212

        Boom Boom Boom

        JL Audio delivers again and again. It's not too much bass but enough to give you that car rattle if you want it. Nice compact deep full sound. Be sure to pair a good amp with it.

        Helpful (12)
      • April 26, 2018

        5 2015 GT - SteveN

        Great Sub!

        I love this sub and I love the fact that it opens up my trunk space. the only issue i've had with it is the speaker grill will vibrate loose and fall off and I have to keep putting it back on. I'll look to see if i can find a better way to secure it. But Overall It sounds great and fits perfectly I'd definitely recommend it to anyone looking to add some bass to their mustang. Also I'm using the factory stereo which I upgraded to sync 3 myself and an Alpine mon amp to power it.

        Helpful (20)

      Questions & Answers (11 answers)

      5 Top Rated Questions

      if you don't have the factory sub in the car already, will this still work? or is it only to upgrade the existing one.

      • This Stealthbox Subwoofer Upgrade Kit is a replacement unit however it can be installed into a vehicle that does not have a factor subwoofer with a little wiring.

      Helpful (12)

      According to my local Ford dealer the factory sub box is the same part number for the fastback and the convertible. Why won't this one work for a convertible if the factory box is the same for both?

      • The enclosure used for the JL Audio Stealthbox Subwoofer Upgrade Kit is larger than the OEM sub enclosure and will not fit into the convertible's trunk properly due to clearance issues.

      Helpful (2)

      Is there a sub woofer included? if not does the subwoofer need to be a shallow sub or will a rgular fit too?

      • Yes a subwoofer is included.

      Helpful (0)

      Is there a factory amp that will work with this if you did not have a factory subwoofer? I see it states you need speaker wire in other questions but do you need an extra amp? Does it come with instructions on installation and wiring for those that are not replacing a stock?

      • If your vehicle did not come equipped with a subwoofer, you will want to install a subwoofer amp. Also, if your stereo doesn't have pre-amp outside you will need one that does. You can find the installation guide for the JL Audio Stealthbox Subwoofer Upgrade Kit at the link below.

      Helpful (0)

      Why the new picture remove the speaker grille compare to other speaker/sub/amp combo?

      Post Your Question
      6 More Questions
      How would this mount in a vehicle that didn’t have the factory sub? Is hardware provided to mount differently from the factory box or does it use factory mounting hardware/holes? 1 answer
      I Have a 2017 eco base. 6 speaker system. didnt come with the factory sub. will this work directly or would I have to buy an amp too? 1 answer
      Is it true plug and play if you have a factory sub? Same connection and all? 1 answer
      Is it possible to to have two left and right ? Or it only comes for the right side ? 1 answer
      Why will this not fit the Convertible? Is there an option available for the convertible or can this one be modified to fit? 1 answer
      Is there a built in AMP? 1 answer

      Installation & What's in the Box

      Installation Info

      What's in the Box

      • (1) Stealthbox
      • Installation Hardware

      Will It Fit My Mustang

      • Bullitt - 19, 20
      • EcoBoost - 15, 16, 17, 18, 19, 20
      • GT - 15, 16, 17, 18, 19, 20
      • GT350 - 15, 16, 17, 18, 19, 20
      • GT350R - 15, 16, 17, 18, 19, 20
      • GT500 - 20
      • V6 - 15, 16, 17