Auto Sensing and Power On Issue

[siuengr]

I bought a new subwoofer and there is a 1 minute delay from when it senses a signal and when it actually turns on. I wouldn't mind that problem so much, but whenever the signal isn't strong enough it shuts back off and takes another minute to turn back on. So basically it gets a signal, one minute later it turns on, its on for about 30 seconds, then shuts back off. Does anyone have any suggestions on what the problem could be, or what to look for on the amplifier to fix? I new about the delay problem when I bought the sub, but I didn't know it would keep shutting off. I could take it back, but I only paid $25 for a 12" sub with 250W amp, so I woul just like to make it work myself.

[eyekode]

1 minute to turn on seems too long and 30 second turn-off seems too short.

I think these circuits usually look something like:
http://sound.westhost.com/project38.htm

Turn-on time for this circuit is dependent on how fast the sensing circuit can charge-up the capacitor that keeps the relay on. This should be pretty quick. Turn-off time should be based on the RC time constant of the charging cap and discharge resistor and I would be very surprised if it was intentionally less then 5 mins. Maybe charging cap is bad/leaky?

[Joe L.]

siuengr wrote:

I bought a new subwoofer and there is a 1 minute delay from when it senses a signal and when it actually turns on. I wouldn't mind that problem so much, but whenever the signal isn't strong enough it shuts back off and takes another minute to turn back on. So basically it gets a signal, one minute later it turns on, its on for about 30 seconds, then shuts back off. Does anyone have any suggestions on what the problem could be, or what to look for on the amplifier to fix? I new about the delay problem when I bought the sub, but I didn't know it would keep shutting off. I could take it back, but I only paid $25 for a 12" sub with 250W amp, so I would just like to make it work myself.

It sounds to me as if the level sent to the subwoofer from your amplifier is too low. The auto-turn on circuit on the subwoofer amplifier eventually turns on when a louder than usual signal is eventually sent to it.

You might see if your receiver has an output level control adjustment for its LFE output. If it does, set it to its highest setting. Then, turn down the gain control on the subwoofer plate amplifier to keep it balanced with your other speakers.

Try the level fed to the subwoofer, before deciding the auto-turn on feature is broken and needs repair. Odds are good it is just too low.

Now, if you are not using an LFE output, but instead feeding the subwoofer from the speaker level signals sent to the L/R channel speakers, then make sure your receiver/preamplifier is set to treat them as "Large" otherwise, the receiver is routing most of the LFE signal to its LFE out, and again it would take a very loud LFE signal to trip the auto-on circuit based on any remaining LFE signal present on the front L/R speaker leads.

Joe L.