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Old 23rd February 2005, 02:12 PM   #1
sachi is offline sachi  United States
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Unhappy subwoofer problem.HELP!!

hey guys,
i plugged in my dad's subwoofer and it seems to make a loud thump when it is turned on/off.
why is this happening? how do i eliminate this?
if i continue using the sub as is, will i risk damaging the sub if i'm unable to eliminate the problem?
any help will be much appreciated.
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Old 23rd February 2005, 04:41 PM   #2
Did it Himself
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If it has always done it then I would suggest it's just a design issue, not a lot you can do.
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Old 23rd February 2005, 05:42 PM   #3
Tweeker is offline Tweeker  United States
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Would perhaps turning them on via a rheostat switch fix it/be safe?
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Old 23rd February 2005, 08:58 PM   #4
danyel is offline danyel  Romania
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The problem is in the amplifier.If u'r amplifier is supplied with differential voltage( +/- , gnd),due to the the filtering capacitors(there is allways differences between them as a value),when u turn it on, it gives a voltage peek that can blow your speaker.What can u do? U can build a speaker protection that connects your speaker 5-10 secondslater from the moment u power it up.
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Old 1st March 2005, 11:26 AM   #5
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Hi Sachi

You can buy a kit from Maplin which has relays connecting the speaker/s and provides a switch on delay of a few seconds. If I recall it also continuously senses for a dc voltage across the speaker (indicative of an amp failure) and will disconnect the speaker/s in this event.

I don't know if there's a Maplin in your area - their main website may have this info and will have some details of the kit.

Hope this helps

John Hope
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Old 2nd March 2005, 05:53 PM   #6
navin is offline navin  India
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if it is just a sub i would not worry. most subs can handle quite bit of power for the 5-10ms that the thump is there for. if it is a fullrange speaker the Xo should protect the mid and tweeter if not the tweeter or mid could blow. i suppose the thump is audible but not loud.
...still looking for the holy grail.
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Old 2nd March 2005, 06:12 PM   #7
sachi is offline sachi  United States
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hey Navin,
its just a sub. its a deftech Prosub100Tl. i wrote to the manufactuerer and he says that it is normal for the sub to make that thump when turned on/off due to the signal sensing circuit which causes the thump when a transient occurs.
it is audible but not loud.
so i guess, that takes care of that.
thanks anyways guys.
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