New speakers

[volvo_boy_88]

I just bought new speakers for my 850 sedan because my used ones that I had previously bought from a salvage yard about a year ago have started to blur and sound distorted and blown out, Here are the ones I got if you would like to look:

cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=110660140013&viewitem=&sspagename=STRK%3AMEWNX%3AIT

My question here is that I know how Volvo used 8-ohm speakers to produce the proper amplification that creates the pair of 4-ohm speaker output as mentioned here in this post:

www.volvo-forums.com/t19289-1995-850-wagon-speaker-sizes-help.htm

But my question is, with these speakers that I got they are for the rear shelf and front doors, but they are 4-ohm impedance while the stock speakers I know are 8-ohm. The post about the speaker sizes posted above mentions that Volvo wired the 850 sedan to follow front doors and dash and then the rear shelf and rear doors to equalize. I've been doing some reading and I am wondering if by keeping the dash tweeters and rear door speakers at 8-ohms and then with these new speakers being 4-ohm for the front and rear shelf, will this be equalized as far as the ohms go or should I just look into getting 4-ohm speakers for the rear doors and dash to equalize the system to 4-ohms completely? I want to avoid having to take the car in to a shop to have the whole system re-done if possible, hence why I am asking here to find a better solution. Please let me know, thanks for the help.

[Ozark Lee]

I replaced all 8 speakers in my cars with 4 Ohm Infinity speakers and neither the head unit nor the amp in the case of the Platinum seems to care. The balance front to rear is off on the 8 speaker system since I took things down to 2 Ohms on the rear door / rear deck speakers that run in parallel. If you are worried about impedance just throw a 10 watt series resistor in line with each speaker.

I deal with complex impedances all day but then again I am working with RF stuff that has 20 to 50 kW transmitters. At that power level the impedance match gets a bit more critical.

...Lee

[FCPEURO]

I did the same thing in my 940Turbo and everything worked great.

[volvo_boy_88]

So I can still pretty much replace all 8 with 4-ohm speakers and still be ok without having to change anything? Is that what you are saying? I don't care much for the impedance I just want the sound to have good bass and quality, not to sound like crap or anything. Will it matter then if I just replace all 8 with 4-ohm speakers? I seem to be leaning more towards that anyhow.

[midimykeys]

Lee, I just purchased a pair of 5-1/4 Polk coaxial speakers for the front doors, but they are 4 ohms. I called radio shack and asked them if they had the 10 watt series resistors. They said they only had those available at 1, 10, and 16 ohms. They did say however that they had 20 watt resistors for 8 ohms. Do you know if installing 2 of these resistors at each speaker would work instead of the 10 watt resistors?

[fazool]

The Volvo speakers are 8-ohm elements wired in parallel to create the necessary 4-ohm impedance for the head unit.

If you replace 8's with 4's you will create reduced impedance (less resistance to current flow) allowing the amp to be overdriven.

Thats why aftermarket amps advertise "2ohm stable" if they have that capability.

Conversely, if you were to replace 4ohm elements with 8's (like connecting a home speaker to your car) you would be under-powered and lack volume.

Adding a resistor in series will protect the amp but it will slightly degrade the sound quality. You will be dropping voltage across the series resistor so the signal feeding into the speaker will be lower amplitude and thus the shape of the signal will be proportionally flatter. You want that expanded as much as possible for as much dynamic range as you can get (separate the low and high points as much as possible). By flattening the whole thing you reduce this. Increasing the volume just raises them proportionally.

[midimykeys]

Ok, well I wanted to replace the two door speakers which are blown. I am going to use a resistor in each door. Which one is better, the 10 or 20 watt 8 ohm resistors? Radio Shack only carries the 20.

[ChiNorm]

A resistor in series with a voice coil with clobber the amplifier damping factor, which is not good for bass response at all.

Your amp is much more likely to distort or die when confronted with a 2 ohm load, which is, after all, only 2 ohms away from a dead short circuit.

If you have an outboard OEM amp the problem is greatly reduced, as those amps tend to be better built. I would be very leery of running a head unit into 2 ohms. The owner of the stereo store where I once worked would refer to this as "Tuning for smoke".

You have only two good choices, either get an outboard amp stable at 2 ohms or get replacement OEM speakers out of a boneyard.

[fazool]

OK, what model car do you have and where are the current stock speakers?

The reason I ask - my S60's have a 8ohm door and a 8ohm door in parallel for the 4ohm left and right front channels.

If you need a high quality 8ohm replacement and are only replacing one piece you can buy a component speaker set (which is the separate elements detached but separately at 8ohm each.

I did exactly this.

[midimykeys]

The speakers I replaced are in the front doors, so bass isn't really a critical issue. The 4 speakers in front (2 on dash and 2 in front doors) are linked together, and the 4 in back (2 in rear doors and 2 on rear deck) are linked together. I don't want to remove the dash to replace the good speakers inside. So now I'm left with an option to find replacement speakers at a junkyard, or keep the new ones and put a resistor on each one. I am opting for the resistors, because the new polk speakers really pump life into the whole system. Lee mentioned getting 10 watt resistors, but Radio Shack only had 20 watt ones. Am I protecting the amp sufficiently with installing the 20 watt resistors with the new polk 4 ohm 5-1/4 door speakers?