Radio

Yes, it can handle the 4ohm impedance speakers, even though they are newer. As for your question concerning the wiring, I do not really follow what you are asking there. You should be able to just use the existing wires, as they are connected. Just unhook the old speakers and hook up the new ones. Of course I am no expert on radios, but I have installed and set up more than my share of them.

Speakers with a lower impedance will need more current flow through them to achieve the same volume. Cheaper radios will develop distortion when using the wrong speakers because the speaker itself is a major part of the audio output circuitry. That said, be aware there is resistance in the wires running to the speakers, and as far as the radio is concerned, it does not know the difference whether the resistance it sees is in the speakers, the wires, or the less-than-perfect connector terminals. Even when you use an ohm meter to measure resistance, if you start by putting the probes together first, you will find there is a good two to five ohms of resistance just in the meter's leads.

The story gets even more complicated when you consider that a speaker's resistance is listed as "impedance". That just means it is a factor in AC circuits, which speaker circuits are. The coil of wire in a speaker has basically 0 ohms of resistance, but the expanding and collapsing magnetic field when alternating current is sent through it requires energy because the movement of that magnetic field fights against itself, therefore it resists change, and that means the value of current flow, in milliamps, really does not like to change. If the radio suddenly puts out a high voltage, corresponding to a loud note, current must increase a lot, but fighting the changing size of the magnetic field opposes that change in current at first. To boil that down to Ohm's Law, the basic building block of all electrical theory, when voltage increases and resistance stays the same, current will also increase proportionally. In a speaker circuit, however, voltage from the radio increases, and current flow ends up changing very little at first because to do so requires it to fight the magnetic field that refuses to increase quickly. The only way for this to occur is if voltage goes up, and resistance goes up, current will stay the same. The resistance in the coil of wire can not magically change on its own. It is the AC resistance, (impedance), that changes, and frequency is a factor in that. Real low frequencies are approaching 0 hertz. They are almost direct current. That is where the coil of wire appears to be about 0 ohms. At very high frequencies around 20,000 hertz, the coil's impedance might be closer to 1,000 ohms or more. Related to this wondrous story, this is why it takes a real lot of current from the amplifier to run a woofer. Being sized to run a large cone, the coil does not have much impedance, so it does not develop much of a magnetic field. It takes a much higher amount of current to get the cone to move.

An off-beat way to think of this is to imagine you have a garage that you want to move further away from your house. If you hook a bulldozer to it, you could drag the garage down the road. Compare the power of a bulldozer to that of an earthquake. The earthquake is millions of times more powerful, but if the fault line runs between your house and garage, the garage might only move an inch or two further away. The bulldozer is the tiny high-frequency notes. It can do a lot. The earthquake runs the low-frequency notes. It has to expend a real lot of energy to accomplish a little.

What you are really running into with your new speakers is the four ohms of impedance only pertains to one standardized frequency it is being measured at. The electrical impedance seen by the radio will go up very high as the frequency goes up. No speaker is efficient at reproducing every frequency. That is why high-end audio speakers include woofers, tweeters, and mid-range speakers. Each one handles just part of the frequency spectrum. When you use a single speaker, those are most efficient in the mid-range, which is most pleasing to our ears. You do not want to just have a woofer. Everything will sound muddled. You do not want just a tweeter. Everything will sound tinny. Your radio is designed to reproduce those mid-range frequencies, so adding the woofers and tweeters will not do anything for sound quality.

Sorry for getting so long-winded. The bottom line is four-ohm speakers will probably sound just fine, but you will need to turn the volume control up a little further than you are used to.

Now here is a guy who knows a whole lot more on the subject than I do. I defer to him.

Yup; if you cannot baffle them with brilliance, dazzle 'em with nonsense! Once I got started, the momentum was too great to stop my fingers on the keyboard.

Happy Sunday to you Heyman1104.

You are mis-thinking this. The impedance of a speaker does not affect sound quality any more than adding a racing stripe makes a car go faster. Back up for a minute and think about the thousands of different audio products for homes and cars. They are all different sizes and shapes to be used in different applications, and to appeal to different people. Every one of them has its own unique circuitry to produce signals strong enough to run a speaker. Each circuit uses different capacitors, coils, resistors, and transistors that together combine to work best within a specific range of frequencies. Of all those carefully-selected parts, one of them is an "inductor". Meaning a coil of wire, and it is attached to a paper cone. You call that a speaker. If you change any one of those parts, you change some characteristic about the circuit's performance. It could be so extremely insignificant that you cannot tell the difference. It could result in distortion from part of the signal being "cut off" and not making it to the speaker. It could result in high notes being amplified more than lower notes.

Compare this to replacing a spark plug wire with 20,000 ohms resistance with a new wire that has 25,000 ohms. It is highly doubtful you will notice any difference in engine performance, unless, of course if the old wire was bad. Put a more free-flowing air filter on and is the engine going to take in more air? Nope. It just has to work less to do it.

To confuse the issue even more, lets suppose you measured the AC resistance, (impedance), to be four ohms at 1,000 hertz. That same speaker might present 50 ohms of impedance at 5,000 hertz. Your original speaker might present eight ohms impedance at 1,000 hertz, and the replacement four-ohm speaker presents eight ohms at 1,050 hertz. What I am not doing a good job of saying is impedance is a factor mainly of frequency, not of the actual DC resistance of the coil of wire. Impedance is also affected by the diameter of the coil of wire, the physical size of the magnet inside it, and its strength, how closely the coil sits to that magnet, and the number of loops of wire in that coil.

This is why measuring a speaker's resistance with an ohm meter is not terribly practical. If you remove the speaker wires at the radio, measure the resistance between them with the old 8-ohm speaker attached at the other end. First, to be accurate, put the meter's probes together and see what you get on the meter's lowest range. Typically you will find around two to five ohms. That is the resistance in the meter's leads and must not be part of the measurement, so it has to be subtracted from the speaker wire reading. My guess is you are going to find the total resistance of the speaker and the wire will be around ten to 20 ohms That is the number the engineers used when designing the circuit, and they designed it so it could operate properly with a range of resistances.

You also must remember that it was not all that long ago that speakers were not put in cars. When they became popular "necessities" in the 1950's and 1960's, nothing was standardized. It was real common to find an original speaker listed as a 4-ohm speaker, but there were 12-ohm speakers, and some other uncommon ones too. Eight ohms became somewhat of a standard, and today speaker manufacturers list them as such because a lot of people think it is more important than it really is.

As a side note, you will not find warning labels on consumer products warning that they can be damaged by using the wrong speaker impedance. At most, some hifi purists claim they can tell the difference in these little things, but what is important is if it sounds good to you when you are done.