Nope, not a Polariser..... They looked like this:
car_audio_dash_equalizer.jpg
Some of them might have boosted the sound a bit but the purpose of an equaliser was to be able to make better adjustment of base, treble and midrange sound responses. Many of them had a "loud" function as well. It was streets ahead of what was available in the 70's, yet so primative when compared to what has come later. An AM/FM tape deck with an equaliser and a set of 6 inch front speakers and a set of 6x9's in the rear was a pretty good deal in the mid 80's. Late 80's for big gains in sound - CD players for starters.
Sad, isn't it....

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