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Old 06-22-2006, 09:31 PM   #1
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Subwoofer pulsing with no sound

This is the second time I have noticed this happen:

After installing a new amplifier for my subwoofer and having it work fine for the first few minutes, I turned the ignition or deck power off and then on again, then the subwoofer made some distorted sounds (even at low volume) and then started heaving (for lack of a better word) in and out at a rate of about 1 second per heave. It looked like the sub was going in a n out to max excursion but very slowly. What is going on with the sub or amp?????

The first time this happened was with an Xtant x1001. After switching the amp from non-balanced-input to balanced-input setting it worked fine (I don't have a balanced signal by the way).

Today, after installing a Diamond Audio D7152 to run the same subwoofer (Diamond TDX 12 inch) I had no problems for the first 10 minutes of tuning and playing around with the set up etc., and then after a the vehicle was off for a few minutes, I happened to turn it on again and, at a low volume, the subwoofer was making some small static/burping sounds and I looked at the cone and it was heaving in and out again! I turned the deck on and off about 4-5 times with the same result each time until it finally began working in a normal way.

My concern is that I am damaging the subwoofer or the amp (or both) somehow. The vehicle is my wife's truck so she won't be listenging for strange noises and I am worried she might drive for a long period of time with this going on.

Anybody have any idea what could be causing this?? I do have a line driver running to the amp, but I had a different unit running to the last one so I don't think that is where the problem is.

Any input will be helpfull thanks.

PS - this Diamond amp/sub combo it THE BEST I have ever heard.

KENWOOD H/U - ZAPCO DIGITAL SERIES AMPS - FOCAL FRONTS - JL SUBS
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Old 06-22-2006, 10:41 PM   #2
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i do not know 100% but here goes

i would suspect that the remote wire that you are using.....that is coming from the head unit....does not have enough voltage thru it....i would suspect that you are playing it and after a few mins, it does this...and with out even asking you i can only imagne that this is happenig either while you are throttleing it....or if you are doing it with the car off.

if the voltage goes down then the quickest test that you can do is take off the remote wire, and just use a jumper from the main amplifier power and jump it to the remote wire(the acurate test to do is to se what the voltage is with a DMM).... if that solves it then you will have to use some accessory wire to turn on your amp(s) or use the normal remote wire to activate a relay that comes from battery, that way it controlls it i nthe same manner but uses direct power from batt for the remote.

this is the biggest fear.....that your voltage is not just going down on your hreadunit and it is going down on tha amplifier too.....if your voltage is dropping too much, your will current will jump up and kill the amplifier....if it hasnt already.


now here is why i suspect this...same identicle thing was happening to my friend at a show....but his reason was because he had 5 amplifeirs in the car and the remote wire didnt have enough voltage when the car was off. it ra n ok when the car was running. i hope that it is this and not that it is a dead amp....

keep us posted on what it is...good luck
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Old 06-23-2006, 08:45 AM   #3
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I do have a relay module - I will install it in the vehicle and hopefully have no more problems with this. Thanks for the advice!

I always thought the amplifier would shut down automatically with insufficient voltage...
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Old 06-23-2006, 09:27 AM   #4
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you have to test to make sure it is that...cause this is just one factor that might be making the woofers pulse after a few mins....you really should get the voltages checked at your remote and see if it dipping to 10 volts at bass hits.
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Old 06-23-2006, 09:35 AM   #5
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i had this happen once a couple of yrs ago when I used a splitter block for my remote....damn thing sounded like there was an apache helicoptor right in my car.
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Old 06-23-2006, 10:21 AM   #6
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I use a splitter block for my remote. One in from the HU, three out to amp1, amp2 and line driver.
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Old 06-23-2006, 10:54 AM   #7
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What deck are you running? could it be the same deck as before with the other amp? does the woofer still moves with rca dissconnect from the amp?

It almost sounds like the deck is putting out dc or ref gnd is open. you could try a passive subsonic filter and see what happens or try a portable amp and see if there are movement on the woofer with no music.
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Old 06-23-2006, 01:46 PM   #8
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It is the same deck as before (Kenwood Excelon - 1 year old). I did have a JL Audio 500/1 hooked up for awhile and never had problems with it, or if I did I didn't notice.

The sub seems to be running fine today. I will try it again later with the engine off to see if low voltage might be causing the problem. I will also install the relay, but I am still not clear on why this might help - I always thought the voltage came through from the power wire, not the relay switch.

I also wonder if the fact that I am using a line driver might be causing issues. Could I be trynig to pull too much voltage from the battery with the line driver??

Thanks for all the input so far.

KENWOOD H/U - ZAPCO DIGITAL SERIES AMPS - FOCAL FRONTS - JL SUBS
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Old 06-24-2006, 04:23 PM   #9
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Motorboating noise

Sounds to me like you have a "motorboating" noise problem.
http://en.wikipedia.org/wiki/Motorboating this may help explain.
And Team Shadow has a possible answer.
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Old 06-24-2006, 07:13 PM   #10
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Whatever the problem was it is not happenning anymore. I switched the amp sensitivity to high (the -12db switch) and instantly had bad noise come from the sub (again the vehicle was not running). I waited a minute, switched it back to -12 and the amp has been fine since. Obviously the problem has to do with the system needing more power than is supplied. Thing is I only have two amps, one is 650RMS and the other is 200RMS.

My next question is - do I need a capacitor? I don't think so but...
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Old 06-24-2006, 07:13 PM
 
 
 
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