subwoofer problem.HELP!!

sachi · 23rd February 2005, 03:12 PM

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.
Sachi

richie00boy · 23rd February 2005, 05:41 PM

If it has always done it then I would suggest it's just a design issue, not a lot you can do.

Tweeker · 23rd February 2005, 06:42 PM

Would perhaps turning them on via a rheostat switch fix it/be safe?

danyel · 23rd February 2005, 09:58 PM

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.

John Hope · 1st March 2005, 12:26 PM

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

navin · 2nd March 2005, 06:53 PM

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.

sachi · 2nd March 2005, 07:12 PM

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.
Sachi

23rd February 2005, 03:12 PM	#1
sachi diyAudio Member Join Date: Dec 2003 Location: Silicon Forest	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. Sachi

23rd February 2005, 05:41 PM	#2
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	If it has always done it then I would suggest it's just a design issue, not a lot you can do. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

2nd March 2005, 06:53 PM	#6
navin diyAudio Member Join Date: Jan 2002 Location: Mumbai (Bombay), India	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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23rd February 2005, 06:42 PM	#3
Tweeker diyAudio Member Join Date: Dec 2004 Location: Cincinnati, Ohio	Would perhaps turning them on via a rheostat switch fix it/be safe?

23rd February 2005, 09:58 PM	#4
danyel diyAudio Member Join Date: Feb 2005 Location: bucharest	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.

1st March 2005, 12:26 PM	#5
John Hope diyAudio Member Join Date: Feb 2005 Location: nr Oxford UK	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

2nd March 2005, 07:12 PM	#7
sachi diyAudio Member Join Date: Dec 2003 Location: Silicon Forest	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. Sachi

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