[simpsons]

Hmmm. Well a picture says a thousand words and so it is with the Hitachi speakers you have.

From just a cursory look at eBay, the foam surrounds are the weak link and can easily be replaced for pennies.

The picture also tells me that the tweeter was made by Goodmans and I guess so will the bass unit.

The small printed circuit board is, as said, designed to filter or split low notes for the bass large speaker and the tweeter.

Goodmans made 2 tweeters which look the same. DT3 for low cost boxes and type 571071 which according to Pink Fish Media are as different to chalk and cheese. Both are said to 8 ohm units. The better ones are used in the Goodmans Magnum and Minister Loudspeakers both also specified as 8 ohm impedance. Look at the back of yours to find out which type you have.

Using a "Car" loudspeaker, even if you could find one 20cm or so, would be, in my opinion, throwing good money after bad as the printed circuit board is designed to be used with specific speakers only.

Replacement 20cm or 8" (as when made) speakers are expensive and to answer you question 8 or 4 ohms I wonder if the bass is 4 ohms to tame the brightness of the tweeter.

To cut a long story short, my recommendation would be to re foam them.

Sorry if I was a little long winded but when a label says one thing "4 ohms" and the speaker manufacturer says something different, the first question must be why.

Chris