"Do I need an amplifier when installing multiple speakers on a door?"

Before I answer this, let me start off by saying a couple things to pre-calm the bass-heads and professional installers.  

  1. This discussion is to help beginners who want to get started in car stereo.
  2. This discussion will focus on a budget build that can be done easily.
  3. Not everyone needs an ear bleeding, child floating, break the windshield system.
  4. You don’t need to apply 100 watts to a 100 watt speaker for it to play.
  5. Most factory stereos can output enough power to drive new aftermarket speakers.

No, you don’t need an amp as long as you follow a couple basic guidelines and have a general, basic understanding of car stereo.

Most factory car stereos put out a great signal with decent power.  The reason that most factory stereos sound like doo-doo is because of the speakers used.  A simple aftermarket speaker replacement alone will greatly improve the clarity of any system.

So why add speaker pods?? 

Why Not!  Speaker pods provide a great way to change the look of your interior, as well as bringing the speakers closer to the listener and avoiding any sound distortion caused by the door panel and factory speaker grilles.  Speaker pods are also pretty easy to install and allow you to put larger speakers than you could otherwise fit in the factory location.

Adding dual speakers on a single channel of a factory system can be done as long as the impedance is kept at or above the factory speaker.  There are a couple ways to check the ohm rating of the factory speaker: 1. remove the door panel, remove the speaker and look at the back of the speaker, 2. Search the web for this information (Crutchfield may have the information you need, their website is great for this… and other things).  If your factory speaker is 8-ohms, great!  You can wire your dual 4-ohm speakers in series to get up to 8-ohms and go about your day.  You could wire your dual 4-ohm speakers in parallel to 2-ohm, but this could lead to premature stereo failure for the gain of a couple measly decibels.

Will multiple speakers kill my factory stereo?

To answer this question we need to understand more about a factory car stereo, as well as some basics of speaker wiring.

Finding technical information about the stereo in your specific vehicle can be difficult, but there are some general assumptions that can be made for the majority. The following assumptions are made to err on the side of caution, but may not apply to your exact vehicle, so please do your own research.

Ass. 1: Most Factory systems put out about 30 Watts of power

That doesn’t seem like much, but it is more than enough to power aftermarket speakers and make them sound good.

“But my car has the Bose` Premium stereo system with 35 speakers!!”  Yes it does.  But it still only puts out 30 Watts.

Ass. 2: Most Factory speakers are rated at 4 or 8 ohms

Ohms?  The internal resistance of the speaker.  This is the most important assumption so pay attention!

This is where you can get into trouble if you mess up.  Going below the factory speaker Ohm rating will damage your factory system!  If you are confused about this one, check out the DIY Audio Guy and his explanation.

The goal here is to wire your speakers to match the Ohm rating of your factory speaker. Too much and it won’t be as loud as it can be.  Too little and the stereo can fail. BUT again, cautious is better.  If your factory speaker is rated at 4 ohms, 8 ohms will work, 2 ohms will not.

Are Multiple Speakers Better?

The goal of any stereo installation project is to upgrade and make it sound better.  As said before, any upgrade is good, so why would you want to install two speakers instead of one?

The short answer:  Loudness, or increased dB.  If done correctly, adding a second speaker can gain you the same amount of increased ‘loudness’ as doubling your amplifier output.

The long answer: Learn about how power levels relate to sound output, and how to calculate an estimated output. WARNING: interesting/boring reading ahead.

"Just tell me how to do it!"

Congratulations!  And thank you for reading my technical ramblings.  If you made it this far you either understand what came out of my brain and are on your way, or you just want me to tell you what you need to do.

If you want to install dual speakers, there are two safe ways to go:

  1. Dual 2 ohm speakers wired in series.  This will give you a 4 ohm load.
  2. Dual 8 ohm speakers wired in parallel.  This will also give you a 4 ohm load.



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