Technics SB-M300 M2 crossover restoration

Introduction

I use very rare Technics SB-M300 M2 speakers. After 15 years of using, I decided to look inside and replace old NPE caps by new BENNIC metallized polypropylene film capacitors.

Crossover schema

Two woofers are directly connected to input terminals. Crossover PCB (SUPP98-2A) is accesible after removing tweeter.

New crossover

New crossover have identical schema for mid+high range, but for woofer I added LC filter to cut-off high frequencies. Of course big caps is not possible to place inside reprobox, so crossover must be external.

Material list

Crossover mid + high range
Mark	Type	Amount	Note
C1	3M9 160VAC/250VDC	2	capacitor
C2	10M 160VAC/250VDC	2	capacitor
C3	4M7 160VAC/250VDC	2	capacitor
C5	47M 160VAC/250VDC	4	capacitor
Crossover low range
L6	2,2 mH – wire 1,25	2	inductor
C6	10M 160VAC/250VDC	2	capacitor
Other
	AEC BI-204	4	repro connector pair , used for input
	121051	4	repro connector pair , used for output
	Cinch female	4	panel mount