Audio crossover
 Audio crossovers are divided to 'passive' or 'active crossovers'. Typical components used with passive crossovers are capacitors inductors and resistors. If passive crossover uses resistors to adjust loudness, those generate heat. Instead, active devices typically use resistors and capacitors with other audioelectronic components and those typically don't consume so much electric power. Also, active crossovers are easily built to be adjustable. Still, that doesn't mean that using passive crossover means low quality.