1st order Xover for LaScala

[JohnA]

The resistor flattens the impedance curve in the midrange. Otherwise it would be about 6 ohms on the woofer, 26 to 32 ohms in the midrange and 8 ohms where the tweeter operates.

[brother]

The attachment shows a revised schematic for the crossover with an additional resistor to balance the network to 8 ohms with the inclusion of the #561 power limiting bulb (the bulb adds 0.9 ohms to the high freq circuit). An additional effect is that the tweeter sensitivity is now balanced with the other drivers at 104 dB/W/m. The bulb limits the power to 2 watts and should keep the tweeter from being overpowered.

Another option would be to use a 3.0 mF tweeter cap and omit the resistor to maintain the 6K crossover point.

[brother]

In response to Al K.'s suggestion about a poly switch, I have revised the schematic to provide a .5 A polyswitch for those who may prefer it. The polyswitch will open at 2 watts and provide the same limiting as the bulb. It will automatically reset when it cools and restore the circuit. It is done in the same fashion as Klipsch applies it in some of their other crossover networks. At this point, I prefer the uninterupted limiting of the bulb to the switch. But this is offered as an alternate means of providing tweeter protection. Unless you're really cranking the system, a person won't hit the danger threshold on the 5 watt K-77's using either version. Obviously, the older 2 watt versions will be more susceptable to problems. Either solution will address the issue.