bass loud boom when turning off headunit
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=110065
Printed Date: May 12, 2025 at 12:24 PM
Topic: bass loud boom when turning off headunit
Posted By: s_suzuki
Subject: bass loud boom when turning off headunit
Date Posted: December 26, 2008 at 9:32 PM
Hi everyone. this is my 1st post. hope im not breaking any rule or doing anything stupid :D
This is by far the greatest website about car audio ive seen. ive been reading it for a while now but today i decided to register and see if someone could give me a hand with a problem i have.I did search before posting but honestly couldnt find the words to explain my problem to the search form.
I have a monoblock amplifier and a 15' woofer just installed last week. the thing is everytime i turn off the head unit or change the source (radio/aux/cd) the woofer makes a real loud "boom", like if i was playing real loud music. it happens also when i change the volume level from 1 to 0. if i change the EQ settings on the head unit i get this "boom", and actually it is quite uncomfortable. I asked the guy who installed the system and he told me that all monoblock amplifiers behave like that and i just had to get used to it, but Im not buying that. is it true? and if it isnt, is there something I can do to stop the system from making this unwanted boom?
Thanks a lot for any information and/or opinion.
Replies:
Posted By: haemphyst
Date Posted: December 26, 2008 at 11:53 PM
Gear? Makes and models, please. Usually, this is caused by cheap equipment, and barring that, the remote lead for the amp COULD be hooked to a switch lead in the dash, rather than the remote lead on the deck.
...but no, it ISN'T the way ANY decent monoblock behaves.
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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
Posted By: i am an idiot
Date Posted: December 27, 2008 at 12:35 AM
According to my Crystal Ball, he has a Pioneer Deck. If this is the case, you need to perform the test in the first paragraph on This Page. If your radio does not show continuity between the RCA shields and the case of the radio, read on and repair it as stated. If you wish to take the radio apart and make the repair inside of the unit, I can help you with that.
If it is not a Pioneer deck, there is a problem with the muting circuit of your deck.
On what number is the volume of the deck at normal listening levels?
Posted By: s_suzuki
Date Posted: December 27, 2008 at 5:32 AM
oh soorry about not posting the details before. i was in a hurry last night. thanks for your responses. the head unit is in fact a pioneer. Im gonna do the test you provide in that link "im an idiot" today and see if that is the problem. Ill post back later. thanks a lot.
Posted By: s_suzuki
Date Posted: December 28, 2008 at 10:46 AM
ok i did the test on that link and my head unit doesn't seem to have that problem. there is continuity between the case and the RCA shields. and the resistance is about half ohm. I have two amplifiers connected, the monoblock and a regular one. what i did now was switching the RCA connections, I connected the monoblock on the other RCA output and the regular amplifier on the sub woofer output and the "boom" on the woofer was gone! but i had this horrible noise on the speakers connected to the regular amplifier. so i know this noise is coming out of the sub woofer RCA output from the head unit. I think I'm gonna take the head unit to be professionally repaired, unless there is something I can do about it?
Thanks a lot, and sorry about my bad English. is not my language :D
Posted By: i am an idiot
Date Posted: December 28, 2008 at 11:23 AM
Your radio has the problem. You may have 4 jacks mounted to the back panel of the radio and a separate pigtail with only 2 jacks on that pigtail. You need to check one of the 4 and one of the 2 on the pigtail. One set HAS the problem. This will be a very easy repair for you to perform yourself, I will be happy to help you with it. You will have to remove no more than 5 screws from the unit to be able to do this.
Posted By: s_suzuki
Date Posted: December 28, 2008 at 12:17 PM
i am an idiot wrote:
Your radio has the problem. You may have 4 jacks mounted to the back panel of the radio and a separate pigtail with only 2 jacks on that pigtail. You need to check one of the 4 and one of the 2 on the pigtail. One set HAS the problem.
This will be a very easy repair for you to perform yourself, I will be happy to help you with it. You will have to remove no more than 5 screws from the unit to be able to do this.
Hi, Im sorry, i didnt quite understand what you just said. do you mean my radio has the problem described on the link you gave me before or that my radio has some other problem? what is a "pigtail"? sorry if i didnt gave enough information before. my head unit is a pioneer Dehp-4850MP. I has 4 RCA jacks on the back. the "regular" is connected to the full range amplifier with 4 coaxial speakers. the sub woofer rca output (labeled "sw" on the back of the radio) is connected the the monoblock amplifier with a 15 inch l5 kicker woofer.
Posted By: s_suzuki
Date Posted: December 28, 2008 at 12:20 PM
I was just googling for pioneer rca fixes and found this
https://www.icixsound.com/vb/showthread.php?t=40067
would that work?
Posted By: i am an idiot
Date Posted: December 28, 2008 at 2:15 PM
You need to check all 4 of the jacks. If they are OK, you have a defective RCA cable. That fix you posted should take care of the noise,
Posted By: s_suzuki
Date Posted: December 28, 2008 at 2:25 PM
i am an idiot wrote:
You need to check all 4 of the jacks. If they are OK, you have a defective RCA cable. That fix you posted should take care of the noise,
Well ive checked all 4 jacks and they seem to be ok. I dont think the problem is the RCA cable since i connected both amps to the "noisy" RCA output using each one of the 2 cables and the noise allways comes from the SW output of the head unit. I tried that fix but it actually added noise the the system. really weird.
Posted By: soundnsecurity
Date Posted: December 28, 2008 at 3:00 PM
does your amp have a bass knob? why dont you use a splitter on a non noisy output to feed signal to your sub amp and just use a the bass knob to adjust your sub volume. normally i hate bass knobs but in this case it seems like a good last resort option if you cant fix the problem
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Posted By: s_suzuki
Date Posted: December 28, 2008 at 3:10 PM
soundnsecurity wrote:
does your amp have a bass knob? why dont you use a splitter on a non noisy output to feed signal to your sub amp and just use a the bass knob to adjust your sub volume. normally i hate bass knobs but in this case it seems like a good last resort option if you cant fix the problem
Yes the amp has it. Ill try to send the radio to see if they can repair it. if they cant, then ill have to do something like that. thanks a lot
Posted By: i am an idiot
Date Posted: December 28, 2008 at 3:12 PM
Did you try the fix behind the radio, or did you do it at the amplifier? Doing it at the amplifer would cause more noise. If you tried it at the radio and it caused more noise, there is obviously something wrong with the muting circuit of the radio. As stated above maybe some Y adapters are in order.
Posted By: s_suzuki
Date Posted: December 28, 2008 at 3:18 PM
i am an idiot wrote:
Did you try the fix behind the radio, or did you do it at the amplifier? Doing it at the amplifer would cause more noise. If you tried it at the radio and it caused more noise, there is obviously something wrong with the muting circuit of the radio. As stated above maybe some Y adapters are in order.
Yes, i tried directly behind the radio. the cable just added noise, typical alternator whine. but the "boom" when turning off/changing source/changing radio station remained the same. i guess my head unit really need to be checked by a professional :D
Posted By: soundnsecurity
Date Posted: December 28, 2008 at 3:34 PM
s_suzuki wrote:
soundnsecurity wrote:
does your amp have a bass knob? why dont you use a splitter on a non noisy output to feed signal to your sub amp and just use a the bass knob to adjust your sub volume. normally i hate bass knobs but in this case it seems like a good last resort option if you cant fix the problem
Yes the amp has it. Ill try to send the radio to see if they can repair it. if they cant, then ill have to do something like that. thanks a lot
well if you do send it off for service just make sure when you re-install it the first step it disconnect the negative terminal from the battery. it's important because it could be what caused your problem to begin with -------------
Posted By: tedmond
Date Posted: December 30, 2008 at 8:37 AM
try taking the amp turn on lead and wire it to a relay and place a diode across the trigger terminals to see if it surpresses the pop. i had issues like that too. wired in a relay and diode and no more pop.
Posted By: nitrob
Date Posted: January 06, 2009 at 6:31 AM
I have the same problem but am using a hi/low converter that is active (uses power and ground and the amp turn on is detected by the signal from the RCA) This will be taken care of when I replace the head unit. I am using all HiFonics amps. Two Brutus and one Zeus. Good luck on your repair.
Posted By: jordan61488
Date Posted: January 31, 2009 at 11:07 AM
i have one of them jensen tvs would checking the 4 jacks be the solution for me?
Posted By: i am an idiot
Date Posted: February 02, 2009 at 7:21 PM
If your unit has tons of engine noise, or it is popping as his is, then yes you should check your unit also.
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