Old Sony SS-H551 two-way speakers, a little help?

Hello people. I have a pair of sony SS-H551 speakers from an old sony MHC-G55 system which dates back to 1996. I've only kept the speakers. Unfortunately there's little information on them on the net, I can't find any specs... this PDF is as close as it gets...


As you can see, it's made out of a 15 cm (5.9 inches) woofer and a 5 cm (1.96 inches) tweeter. The rated impedance is 6 ohms. I've googled these part numbers but there's nothing to be found about them.. I'm in the dark here. I opened them up and saw the following:


Parallel connection, a 12 ohms tweeter... to get that 6 ohms rating, the woofer has to be a 12 ohm unit too. I remember this stereo system was advertised as 45w+45w RMS, so these are 45w speakers... There's this 1.5uF capacitor at the tweeter. According to this thread it's there to set a passive crossover and protect the tweeter, but I'm not sure if this is correct or not, because I'm going to build a chip amp for these and maybe that capacitor was tuned for the specific power amp (and who knows what other circuitry, I'm speculating here) in the MHC-G55 system that I haven't got anymore. With that impedance and power I was thinking about building a LM3886-based chipamp, with a +-25V supply, which is good for 40w. I've been using them with an old kenwood KA-300B 25+25w integrated amp that is my father's. Datasheet and schematics of the KA-300 (not B) here:


It's about 30-40 years old now and has some DC offset at the outputs (60mV and 100mV); to be sincere this combination doesn't sound good at all (it could very well be the amplifier that's at fault here), yet those 25+25w are enough to make these speakers sound as loud as I want, at least in the room I listen to.

So, to sum this all up, is my choice of chipamp.. adequate for this set of speakers in particular? And what else can be done about the passive crossover in here, considering that there's not a single datasheet available? I haven't got any measuring equipment apart from a multimeter. EDIT: Now that I think about it, I can play sine waves and listen to the speaker system, see at what frequency does the tweeter start to play... I could find the cut-off point right there.. but it may not be the optimal point..

Thank you very much.

EDIT2: Fixed the images as links... thumbnails didn't work as intended.
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2010-05-04 5:02 pm
It's just a normal cheap 2-way design. The 6Ω rating is more or less the minimum impedance of the system, either in the bass or around the crossover region. The woofer is probably 6-8Ω. The chip amp should be fine. If you can build a chip amp, I bet you can also figure out how to fix the offset in the Kenwood. Designing a "better" crossover requires measurements and is no easier than designing speakers from scratch. All you can really do short of that is just replace the tweeter capacitor with a fresh film cap.
I have some experience building amplifiers the DIY way... I'm mostly a headphone guy (Sennheiser!), this would be a new challenge (higher voltages, etc) but it's not much more difficult than what I'm used to. I have read that the offset problem in the kenwood is likely caused by the input transistors, which have probably gone bad because of age or who knows what.. I've identified them in the datasheet and in the PCB, I think I can get replacements and match them, I'll have to look into that. (there's no DC offset pot in there to quick fix this). Of course it could be anything... There's lots of work to be done in there apart from fixing this little issue. It'll keep me entertained...

I'll measure the woofer later, when I get to disassemble all that cabling.

Fine then, I'll just replace the tweeter capacitors for good ones, and proceed with the chipamp. That should make these speakers sound a bit better, just for those times when a headphone just doesn't cut it and you want to hear some music in the air (and the neighbours are out) :D
Those woofers, or clones, turn up in a lot of cheap speakers.
I have a pair here nominally 6R and mine measure 5.6 Ohms DCR, quite good bass and a smooth roll-off
Real power handling is about 30 Watts program
Best modification you can make to these is also the easiest, fill the box with polyester and/or fiberglass
They make a good midrange crossed over quite low ( a single large cap[ 150/200 uF]seems to work reasonably well with these drivers) if you use a small sealed box.