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Discussion Starter · #1 ·
All headunits put out 25w x 4 maximum. Maybe 10w x 4 rms... BIG maybe.
Speakers vary on the maker, but roughly 35w.

MP3 player is a single disc player that reads MP3 encoded discs. The 6cd changer cant read MP3 formatted discs.

Holding the clip upwards, and from left to right, these are the colors of the wires from the factory radio harness. "-" means negative, "+" means positive.


White/Black – left front +
Gray/Black – left front –
White/Red – right front +
Gray/Red – right front –
White/Purple – left rear +
Gray/White – left rear –
White – rear right +
Gray – rear right –


Orange/Black – 12v constant
Orange/Black with silver dots – 12v illumination
Yellow with silver dots – 12v ignition
Black/Green – Chassis ground

Yellow with silver dots is the wire you would want to use to power your amp remote turn on.

Both 12v constant and 12v ignition are fused at 10amps, possibly higher. 15amps at the most.

As of right now, the factory DVD navigation unit cant read DVD video discs. Noone has yet adapted video to the navigation screen either.

Speaker sizes:

6x8" midbasses, power portion of door
1" tweeters, upper corner A pillar

Lower trim levels dont have tweeters. They have blank panels.

Shorting a speaker lead together or against ground will cause the radio amplifier to go into protection mode, and all speakers will not play.

Speaker depths:

2 5/8" for the fronts
3" (almost..) for the rears
2" for the tweeters

That does not include how thick you make the speaker adaptor.

Stock tweeters have inline capacitors to protect the tweeter from low frequencies.

7", 6.5" and 5 1/4" midbasses will fit with an adaptor.

6x8" or 5x7" is a direct fit.
ALL 5x7" speakers have 6x8" mounting tabs.

6x8" will not sound deeper than 6.5". Oval shape distorts at high volume or low bass notes.

Adding amplifiers to the factory system, you will need to use a LOC (line output convertor) or have an amplifier that has high level inputs.

An LOC is installed like a speaker. It then outputs RCAs for your amps. The sound must be full range to work correctly.

High level just needs a full range or high pass input, and it converts the signal inside. No need to run RCAs since the high level input is directly in the amp. makes the best LOCs.

Never mount amps to metal. Always use a board or mount to plastic. They cause ground loops by mounting directly to metal.

Never run signal wires next to power wires. They cause noise oscillation in the system.

Power wire coming from the battery should always be fused no more than 18" away from the battery, to protect the wire of shorting.

Metal should always be bare when grounding any component, especially amplifiers.

The "Big 3" is upgrading wires around the battery. They usually start with:
Negative terminal to body
Positive to alternator
Engine to body

The stock alternator puts out 95 amps. It is always wise not to overdraw the alternator by more than 200% in long periods of time. There will be damage sustained if done so.

Grounding mod is adding more ground wires from the engine to the body, and more grounds from the negative post to every part of the engine. By adding more grounds to the system, there is more paths for electrons to be drawn through, therefore stabilizing electronics.

if you got more to add, PM me


· Registered
2,757 Posts
Discussion Starter · #2 ·
Before posting => Mazda3 Electronics/Car Audio F.A.Q

Metra has had their dash kit out a bit. The product number is #99-7504. Dont ever pay more than $25 for a dashkit. They are ripping you off.

Scosche has one too, but I dont know the model number. Best Buy and Circuit City both carry Scosche.

Power wire needs to be identical to the ground, in terms of size. So, if your amp takes 4ga in, there should be a 4ga power, and 4ga ground.

There is no need to run tremendously large wire for the speakers in the doors unless you plan to run a ton of power to them. The factory will suffice up to 250wrms.
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