Why the resistor change from 2.5 Ohm -> 2.0 Ohm in the Model 10 Crossover Schematic?

StantonZ

I'm thinking about rebuilding the crossovers and replacing the tweeters in my 10B's again (although still uncertain whether to go with RD0-194 or -198), and noticed this resistor value change from the 1984 schematic to the 1989 schematic. Why/which value should be used, and is it tweeter type dependent?

TennMan

Use the resistor value in the schematic for your 10B. The earlier model used a different tweeter and that is probably the reason it had a different resistor. You have the sl2000 tweeter in your 10B. The RDO-194 sounds much better.

StantonZ

So WHICH schematic? One has a resistor value of 2 Ohms, the other 2.5 Ohms. Which one goes with the 194's?

TennMan

Same answer to the same question.

TennMan wrote: »

Use the resistor value in the schematic for your 10B. The earlier model used a different tweeter and that is probably the reason it had a different resistor. You have the sl2000 tweeter in your 10B. The RDO-194 sounds much better.

westmassguy

StantonZ wrote: »

I'm thinking about rebuilding the crossovers and replacing the tweeters in my 10B's again (although still uncertain whether to go with RD0-194 or -198), and noticed this resistor value change from the 1984 schematic to the 1989 schematic. Why/which value should be used, and is it tweeter type dependent?

The 1984 "original" schematic shows a fuse in series with the tweeter, while the later 1989 schematic shows the Polyswitch. Since everything else is equal, the difference in resistance between the 1 amp fuse and the Polyswitch is most likely the reason for the lower value. If your planning on using the RDO-198s, instead of the drop-in RDO-194s, be aware that the resistor value is different, and the hi-pass shunt inductor must also be changed. Refer to the M10 SL3000 Mod schematic.
I just rebuilt a pair of 10s for a customer and put the 198s in, along with all the other changes. The difference was stunning to say the least.

StantonZ

westmassguy wrote: »

The 1984 "original" schematic shows a fuse in series with the tweeter, while the later 1989 schematic shows the Polyswitch. Since everything else is equal, the difference in resistance between the 1 amp fuse and the Polyswitch is most likely the reason for the lower value.

Now THAT makes sense. So if/when I rebuild the crossovers and decide to eliminate the Polyswitch (I have 2 w/fuses and 2 w/Polyswitches), I'll need to adjust that resistor accordingly; if I were to examine the crossovers I bet I have 2 each with different resistor values. I think I'm going with the "drop-in" 194's, but thanks for the schematic reference if I don't.

westmassguy

StantonZ wrote: »

Now THAT makes sense. So if/when I rebuild the crossovers and decide to eliminate the Polyswitch (I have 2 w/fuses and 2 w/Polyswitches), I'll need to adjust that resistor accordingly; if I were to examine the crossovers I bet I have 2 each with different resistor values. I think I'm going with the "drop-in" 194's, but thanks for the schematic reference if I don't.

The polyswitches suck, and fuses can add additional complexity, and problems due to corrosion of the fuse holders, different fuse manufactures etc. As long as you're using quality amplification, I'd eliminate the fuses and polyswitches altogether, and go with one 2.5 ohm so they all match.