Speaker Impedance Mismatch?

I have a 1995 Blazer 4D 4X4. The rear door stock speakers I'm replacing say Delco ERS 9.5 Ohms on the back (they're 6.5"). I purchased a couple of nice Kenwoods (50 Watts RMS) that say 4 Ohms. The Kenwoods sound horrible. Do I have an impedance mismatch? Do I really need 8 Ohm speakers or something?

Thanks for any replies.

***I love my Blazer 'cause it comes with Metric bolts on the top of the front shocks and standard on the bottom!***

It is possible to have speakers other than 4 ohms. The impedance is resistance to the flow of electricity provided from the stereo. If your replacement speakers are of lower impedance, more electricity will flow through them resulting in the stereo having to produce more power. This could very easley result in distortion. Example

Factory stereo 16 watts RMS ( per channel ) @ 9.5 ohms
Stereo will consume 12.3 volts and 1.3 amperes of current

Now lets say you replace the factory 9.5 ohms with 4 ohm after market speakers

The stereo will still consume 12.3 volts but will require 3 amperes of current resulting in the stereo putting out 36.9 watts of power RMS.

36.9 watts of power is well above what the stereo is designed to produce. Also most amplifiers are designed to operate on a specific impedance. This will result in the signal to noise ratio dropping dramatically and you will hear a lot of distortion.

You will either have to replace the factory radio with a standard 4 ohm stereo or you will have to get speakers as close to 9.5 ohms as possible, to remove the distortion. Continuing with your current setup may result in damage to your factory radio. Your stereo may not distort if the volume is turned way down, no more then 1/4 the way up to full volume but this will depend on several factors.

zorexjonny,

Thanks for the spectacular response. That's more information than I was able to get off many websites about car audio.
I follow what you're saying, so here a few follow up questions.
If I replace the stereo with a 4 ohm stereo, will I have to also replace the other 4 speakers in the system? (front dash L/R and Front door L/R)
or
Can I simply place a 5 ohm resistor inline to each of my 4 ohm speakers?

You will not be able to user a resistor to match impedance because stereos use alternating current to produce sound, AC current is not necessarily slowed down by the use of a resistor ( there is alot involved with this subject ). I have heard of impedance matching circuits or impedance matching transformers used to lower impedance but this is a very complicated subject and if not done correctly could result in damage to the equipment. For maximum and most efficient power transfer impedance from the source must be as close as possible to impedance from the load. Basically in order for your stereo and speakers to function properly as designed without the possibility of damage you will need to have the same impedance in both the speakers and stereo.

What it sounds like is you have the six speaker premium sound system in this blazer. I am not too familiar with how this system is set up. Conventional aftermarket car stereos only have four channels thus they only power four speakers. I suspect the blazer stereo has 6 channels or both the front door and dash speakers are powered off of one channel. There are several ways this specific system could be set up so replacing speakers may be an issue. You may want to consider professional installation as the techs will be familiar with GMs 6 speaker sound systems.

I am in the process of replacing the factory stereo in my 96 2 door blazer and hope to son figure out this 6 speaker sound system. What I am doing for my replacement is factory speakers with aftermarket speakers, running the back speakers and the front dash speakers of of the aftermarket stereo. Then for the door speakers I am purchasing a amplifier to run these. However I purchased the truck with the factory speakers and an aftermarket stereo. Currently all six speakers run off of the aftermarket stereo ( 4 channel ). So it is possible to replace the factory speakers and the factory stereo without purchasing an amplifier. How this is done I am not sure.

What I suspect makes this work requires a knowledge of speaker wiring. You can wire different amounts of speakers together resulting in a change in impedance.

Example:

Two 9.5 ohm speakers wired together in a parallel configuration results in a total impedance of 4.75 ohms seen by the stereo on this channel.

Two 19 ohm speakers wired together in a series configuration results in a total impedance of 9.5 ohms seen by the stereo on this channel.

The blazers six speaker setup could be wired in a specific configuration to yield the desired impedance. Or the blazers front dash and front door of either given side could use a specific circuit that allows for two speakers to run off of one channel. Or the blazers stereo could have six channels to power all six speakers. Also, as much as I wish I don't know everything so there is always the possibility of .D None of the above.

What I can tell you for sure is that it is very important to match impedances, the stereo must be designed to work with the impedance of the speakers. Running 4 ohm speakers off of a 9.5 ohm source will most likely result in damage to the equipment.

I hope to finish my stereo upgrade in the next few weeks so I may possibly be able to discover how GM's 6 speaker system is set up. If you discover how this is set up please enlighten me.

Thanks again for the info.
I'll try to find some 9.5 or 8 ohm speakers for now.
The 9.5 ohnm factory speakers I'm replacing just don't work. Everything on them seems to be intact (no tears, no degredation of any of the materials, wires from terminal to cone seem OK). But absolutely no sound, not even a crackle or hiss.

Standard aftermarket speakers are usually 4 ohms.

Do NOT go for 8 ohms. They are waay to expensive and are not needed.

Get a different CD player for cheap and install it the same time as the new speakers.

The stock speakers and head unit are meant to be used together.

Check out my 1995 Blazer LT 4x4 Stereo here:

http://www.cardomain.com/memberpage/519698/3

Kicks at 140db and will numb your brain.

BlazerLT,

Great looking truck and nice system.
The problem with getting a new head unit is I then have to replace all 6 speakers instead of just the 2 rear door speakers. I was initially looking to just take out the bad and put in the new. This obviously won't work with this vehicle, so I'll just suffer for a while.
Oh well.

Speakers and a new head unit are so cheap lately.

TRUST me, you will absolutely love it.