Subwoofer Questions

[djbenno]

Hi, I’m working on a pair of passive subwoofer for a PA main. Each has a single 15” in a smaller pre-fab enclosure that came with a low pass filter. I like the feature, but it forces me to limit input power to keep from frying it so I want to be able to run directly to the woofer when running bi-amp. I've already installed an additional pair of speakon inputs, and 12 gauge wire going directly to the woofer. Big question here is do I need a diode or something in the circuit to keep from energizing the low pass filter when in bi-amp mode?

Question 2: I want to better seal the ports, input plate, handles, speaker pole mount, etc. What type of mastic is best this?

Thanks for any help you can provide!

[HK26147]

do I need a diode or something in the circuit to keep from energizing the low pass filter when in bi-amp mode?

Based upon your description - you are good to go, and need nothing additional.

What type of mastic is best this?

RTV or Black Mortite.

[DrDyna]

You might want to also install a switch that cuts the wire going to the low pass filter if you're using an active crossover at the amp. The LPF that's in there might have a parallel capacitor in it that would still be connected if both the speaker terminals are connected to the internal LPF.

[djbenno]

Thanks for the input so far. I want to try to keep the audio input quality high as possible. Willa switch degrade the signal? Also, any suggestions for sources for switches?

[DrDyna]

Originally Posted by djbenno

Thanks for the input so far. I want to try to keep the audio input quality high as possible. Willa switch degrade the signal? Also, any suggestions for sources for switches?

Well, the switch would only be in the circuit if you were using the internal passive crossover, as it's between the woofer and the original crossover. Any decent spst switch should do the job, like this one:

SPST Standard Toggle Switch

[richie00boy]

3 amps? Bit weedy for a PA system. I'd look for a 10 amp rated one.

[DrDyna]

Originally Posted by richie00boy

3 amps? Bit weedy for a PA system. I'd look for a 10 amp rated one.

Oh, woops, linked the wrong one, my bad.

This one should do.

SPST Heavy Duty Toggle Switch

[djbenno]

20 amps rated one looks much better. Can you confirm please that it's an AC switch needed (vs a DC switch)?

[DrDyna]

Originally Posted by djbenno

20 amps rated one looks much better. Can you confirm please that it's an AC switch needed (vs a DC switch)?

There shouldn't be much difference at all. All you are really doing with it is divorcing the woofer from the built in crossover while you are using your direct connection.

For argument's sake however, musical signals are AC.

[weltersys]

Originally Posted by djbenno

20 amps rated one looks much better. Can you confirm please that it's an AC switch needed (vs a DC switch)?

A DC switch rated at the same amperage as an AC switch is actually better quality, as DC tends to "arc weld" and pit contacts worse than AC.
That said, if you are not switching while power is going through the switch, a 20 amp AC switch is more than enough amperage for virtually any speaker application.