Sansui SP-2500 Speaker Crossover Repair

[jtslector]

So I recently inherited a pair of Sansui SP-2500 speakers. They have actually never been used and stored in a cool dry place their entire lives so the speakers them selves are in amazing shape. Sadly however, the crossovers inside of them have not done well with time. The sound quality of the speakers is terrible and clearly not like it should be. Both of the resistors in them measure out of spec, and although I don't have a way to test the capacitors, based on the sound quality and what people say online I think its safe to say they have dried out and need replacing. I need some help figuring out what exactly I should replace these parts with. It is for sound so it needs to be some good quality parts and I don't really have any experience with that.

This is what the speakers look like. Pretty cool I think.

On the back is this panel with the input and two knobs to select how the speakers sound.

This is the crossover on the back of that panel. You can see on the left hand side on the top and bottom it has two resistors that say they are 5W 16 ohms (I think?). The bottom ones measures around 18 ohms and the top around 22 ohms. On the right side we have two capacitors that say they are Bi-Polar and one that says its Non-Polar. I have no clue what these mean. All five of these components need to be replaced with new ones, so I will need some help figuring out what exactly to replace them with.

 

[davenn]

Both of the resistors in them measure out of spec,

That would be pretty unlikely that they are faulty
what did you measure them with ? did you lift one end of them so that the rest of the circuit wont affect the reading ?
what resistance did you measure them to be ?

 

[duke37]

Capacitors have two plates or foils separated by an insulating layer, maybe air, plastic or aluminium oxide. To get reasonably large capacitance in a small component, the gap contains an electrolyte and when a voltage is applied, a very thin insulating layer is generated so giving a high capacitance. Reversing the voltage can damage this layer so for AC signals a special type of electrolytic capacitor is needed that will work either way round (bi-polar). The 2.2μF and 10μF are of this type.

Electrolytic capacitors 'go off' and need to be reformed after a long period of un-use.

The 4.7μF (not 4.7MF, that would be as big as your house) capacitor has a plastic dielectric and will work either way round (non-polar), this is unlikely to be faulty.

 

[dorke]

I think your problems are elsewhere.

Look at the switches, they are "dirty to the bone" and need argent good clean-up.
Use deoxit or similar stuff for cleaning.

Only after cleaning, you should consider replacing the caps.
If you do need to, you should replace them with non-polarized audio-grade caps, they are mucho expansive!

 

[shrtrnd]

I lean toward dorke's suggestion. Buy a spray can of electronics contact cleaner from an electronic parts supply store and spray out the switch contacts while rotating them.
This probably has nothing to do with your issue, but I'd check to make sure whatever you're using to drive the speakers matches your impedance.
One other thing I'll mention is that as speakers age, the paper of the cones deteriorates. If the speaker cones are wasted (brittle or deteriorating), they'd sound pretty bad.
I know you said a cool dry storage place, but some dampness over time could have affected them.
The one, last thing I'll say about this, is to check your wires and connections to the speakers. I can't tell you how many times I've seen audio problems that were simply because of bad wiring jobs or the connections.

 

[elebish]

Replace the "NP" caps. The resistors should be fine.

 

[Rob de Fries]

You say: The soundquality of the speakers is terrible and clearly not like it should be.
How do you know?
Have you tried the woofers are moving freely? Pushing them, gently, inward should go easy and without scraping sounds. If the woofer doesn't move in and out, or makes a scraping sound, the voice coil is bad. Mostly due to moisture. Bad sound for sure.
What others already said. The switches need to be cleaned and maybe replacing of the caps might solve the problem.
I can't think of anything else. Hope you didn't wire them "out of phase".

 

[elebish]

Check phasing in this manner: Apply the dc voltage of a 1.5 volt battery to the speaker input terminals and all speakers in the cabinet should move in the same direction. If not. they are out of phase. Check both speaker cabinets. When speakers within the cabinet are out of phase, one speaker will cancel some of the sounds of the other. Also take the advice of Rob de Fries. When a speaker takes more current then allowed, it could warp the voice coil, causing a scraping sound when the cone is moving in or out. Speakers can be re-coned if you can find a place that will do it.