I have a DIY project to install audio unit amp, change the speakers and add subwoofer on my 2019 Honda HR-V sport.

It depends on the speaker and receiver inputs/outputs. If The speakers have bare wires, and the receiver has spring clamps, you are in luck! Check out what I mean by spring clamps in the image linked below. If you can give the model number of the receiver and describe the wires coming from the subwoofer, I can help a lot more.

www.audioholics.com/diy-audio/how-to-use-a-speaker-selector-for-multi-room-audio/NilesSpringLoadedSpeakerSelector.jpg/image_preview

Yes just need a wire adapter

Hi there:
Check this on 2004 Ford Explorer Sport Trac Audio Wiring Schematic:

Car Radio Battery Constant 12v+ Wire: Light Green
Car Radio Accessory Switched 12v+ Wire: Yellow/Black
Car Radio Ground Wire: Black
Car Radio Illumination Wire: Light Blue/Red
Car Stereo Dimmer Wire: N/A
Car Stereo Power Antenna Trigger Wire: N/A
Car Stereo Amp Turn-On Trigger Wire: N/A
Car Stereo Amplifier Location: N/A
Car Audio Front Tweeter Size: N/A
Car Audio Front Tweeter Depth: N/A
Car Audio Front Tweeter Location: N/A
Left Front Speaker Positive Wire (+): Orange/Light Green
Left Front Speaker Negative Wire (-): Light Blue/White
Right Front Speaker Positive Wire (+): Dark Green/Orange
Right Front Speaker Negative Wire (-): White/Light Green
Car Audio Front Speakers Size: 6" x 8" Speakers
Car Audio Front Speakers Depth: 2 1/2"
Car Audio Front Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Gray/Light Blue
Left Rear Speaker Negative Wire (-): Tan/Yellow
Right Rear Speaker Positive Wire (+): Orange/Red
Right Rear Speaker Negative Wire (-): Brown/Pink
Car Audio Rear Speakers Size: 6" x 8" Speakers
Car Audio Rear Speakers Depth: 3"
Car Audio Rear Speakers Location: N/A
Car Subwoofer Speaker Size: 8" Subwoofer
Car Subwoofer Speaker Depth: 4"
Car Subwoofer Speaker Location: N/A
Car Subwoofer Speaker Positive Wire (+): N/A
Car Subwoofer Speaker Negative Wire (-): N/A

Hope this helps; also keep in mind that your feedback is important and I`ll appreciate your time and consideration if you leave some testimonial comment about this answer.

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yes, there is an amp turn-on wire from the head unit (black with a red stripe). You will need to add a power wire and fuse from the fuse box to run the amp. You can use the speaker outputs as inputs to the amp, depending on what you are trying to do. Please let me know if you need more help, and identify the amp model as well as the speakers you will connect.

Car Radio Battery Constant 12v+ Wire: Blue/Yellow
Car Radio Accessory Switched 12v+ Wire: Gray
Car Radio Ground Wire: Brown
Car Radio Illumination Wire: Black/Red
Car Stereo Dimmer Wire: N/A
Car Stereo Antenna Trigger Wire: N/A
Car Stereo Amp Trigger Wire: Black/Red
Car Stereo Amplifier Location: Under the center console.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Pink
Left Front Speaker Negative Wire (-): Violet
Right Front Speaker Positive Wire (+): Green
Right Front Speaker Negative Wire (-): Blue
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Black
Left Rear Speaker Negative Wire (-): Yellow
Right Rear Speaker Positive Wire (+): Red
Right Rear Speaker Negative Wire (-): Yellow

The HR speakers in the Miata are by default wired in parallel so if both your door and HR speakers are 2 ohms, that could present the amp with what it perceives as a short circuit. Probably won't hurt the amp but it might shutdown in protect mode for a minute or two then restart.

You could change the wiring around to make the HR speakers wired in series. Wiring info on doing this here: http://www.3rdstrategy.com/M5_specs.pdf

1) Understand the basics of all car stereo systems. A car stereo system consists of 4 main components and the wiring that connects them. These are the head unit, the main speakers, optional amplifiers and the subwoofers, which are also optional but generally considered a necessary part of any good system. 2) Know that the core of any car stereo is the head unit, which is the cassette or CD player that goes in the dash. All the other components are connected to the head unit by at least one pair of wires. 3) Know about car speakers. The main speakers are usually 2 in the front and 2 in the back, although with what are known as component speakers, each speaker is broken down into two speakers: one for the highs and one for the bass. Each speaker or speaker set (known as a channel) connects to the head unit via a pair of wires. Generally if you are installing a new head unit you want to install new speakers. 4) Know about amplifiers. Amplifiers provide extra power to your speakers and/or extra channels of power for additional speakers. The most common use for an amplifier (amp) is to power subwoofers. The amp connects to your head unit via an RCA cable and often a "remote on" wire, and also connects directly to your car battery through a fused "hot" wire and to the car's chassis with a short ground wire. This article assumes the use of a single amplifier connected to a pair of subwoofers. If you do not have these components simply ignore the steps specific to the amp, doing so will not affect the rest of your installation. 5) Know about subwoofers. Subwoofers are part of any good stereo system. They provide the deep bass that small speakers cannot achieve. Subwoofers are connected to the amplifier which can usually be mounted right to the subwoofer box. If you do not have subwoofers you can simply ignore the steps specific to them. FOR more help click on this link directly http://www.ehow.com/how_5829_wire-car-stereo.html ------ This will help. Thanks please keep updated.please do rate the solution positively .thank you for using fixya

Hi,
Please provide us with the model number and make of the amp and speakers.
In the meanwhile you can also check the webiste below
http://www.diyaudioandvideo.com/FAQ/Wiring/

Thanks for using Fixya
Proton

This one Wire should be for the +. Try connecting the + to the Head Unit and - to a Common Ground. At the Worst, You will Blow the Amp Fuse if not Correct. The Lead from the Head Unit is Only an Off and On from the Ignition. Please Rate My Response! Thanks!

My suggestion is to go to your local audio shop and pickup a dash kit and wiring harness to hook up the din head unit. I actually wouldn't recommend putting in aftermarket speakers unless you don't plan on reselling or they are blown. You could hook a sub up by running your power wire to your amp like usual, hook your amp turn-on wire to an accessory wire and buy a "line level converter" you will tap into factory speaker wires with this and it will convert it to RCAs. You will only need to do this if you are using the factory head unit. Also, unless the aftermarket unit has features that you want that the factory one doesn't, I wouldn't bother with that either. Good luck. Let me know if you need any more help.
-Andrew Hawkins

Auto cut is due to overload, check out the wattage handling capacity of the Amp & the woofer( if the impedence is too low there will be an over load for the Amp.