, ▁while ▁some ▁units ▁also ▁had ▁a ▁mini ▁disc ▁player . ▁The ▁system ▁features ▁a ▁high - per formance ▁digital ▁to ▁analog ue ▁( D / A ) ▁converter , ▁ 2 0 - bit ▁B urr - B rown ▁ch ips , ▁Dol by ▁B ▁noise ▁reduction ▁( ta pe ), ▁dual ▁anten na ▁AM / FM ▁radio ▁and ▁Mc Int osh ' s ▁Power ▁Guard ▁technology , ▁which ▁gives ▁low ▁dist ort ion ▁at ▁high ▁sound ▁pressure ▁levels . ▁A ▁ 6 - band , ▁ 4 - channel ▁paramet ric ▁equal iser ▁has ▁also ▁been ▁tun ed ▁specifically ▁for ▁the ▁B 4 . ▁ ▁Se par ate ▁to ▁the ▁head ▁unit ▁– ▁under ▁the ▁front ▁passenger ▁seat ▁– ▁is ▁the ▁system ▁ampl ifier . ▁The ▁output ▁power ▁handled ▁by ▁each ▁of ▁the ▁ 4 - ch annels ▁is ▁ 2 4 W ▁and ▁the ▁sub wo o fer ▁is ▁ 6 0 W . ▁The ▁total ▁harm onic ▁dist ort ion ▁of ▁the ▁system ▁is ▁as ▁low ▁as ▁ 0 . 0 5 ▁percent ▁– ▁compar able ▁to ▁a ▁good ▁home ▁audio ▁system . ▁ ▁The ▁speaker ▁system ▁compr ises ▁ 2 0   mm ▁soft ▁d ome ▁twe eters ▁in ▁the ▁sail ▁areas , ▁ 1 6 5   mm ▁poly pro py l ene ▁cone ▁ 2 - ways ▁in ▁the ▁front ▁and ▁rear ▁doors ▁and ▁a ▁ 1 5 2 ▁x ▁ 2 2 8   mm ▁sub wo o fer ▁offset ▁to ▁one ▁side ▁on ▁the