Subs keep blowing
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=30665
Printed Date: May 15, 2025 at 5:53 AM
Topic: Subs keep blowing
Posted By: kiteman
Subject: Subs keep blowing
Date Posted: April 19, 2004 at 10:54 AM
A friend has a boss monoblock 1100 amp, and he has 2 12" power acoustic dual 4 ohm subs. The subs are wire up to Parallel so as to bring them to a 1 ohm load. The subs are also mounted reverse in the box. He seems to blow a sub a week? anyone have any ideas?
Replies:
Posted By: DYohn
Date Posted: April 19, 2004 at 11:06 AM
Lots of ideas, including low quality build on those brand names, but the most likely is the amp is clipping heavily due to gain being set incorrectly, and/or the enclosure is way too big. ------------- Support the12volt.com
Posted By: kiteman
Date Posted: April 19, 2004 at 12:38 PM
The box is about 1 to 1.25 prefabe box, would it have anyting to do with the subs being mounted in rev. ? Also what does the phase button do?
Posted By: kickerstang
Date Posted: April 19, 2004 at 12:42 PM
when a sub is inverted it is basically playing backwards. phase is used to control this, being inverted shouldn't have anything to do with the subs blowing
-------------
what!?!?! you want some??
Posted By: southside
Date Posted: April 19, 2004 at 1:08 PM
remember that he has to reverse the wiring if he has the magnet out of the box too. so postive would go to neg an so on. from what i read on here that is what u have to do.
-------------
southsider
Posted By: DYohn
Date Posted: April 19, 2004 at 1:15 PM
With the subs inverted, they add about 0.1 cuft to the enclosure volume, so at worst you are at 1.3 cuft. Is this per sub or is it shared by the two? I strongly suspect the amplifier is clipping, probably because it is being over-driven or the gain is way too high. A boss amp is about 50% over-rated, so your "1100 watt" amp is probably more like 500 watts, so he may have cranked it up trying to get more out than it is actually capable of delivering. RESET THE GAIN! ------------- Support the12volt.com
Posted By: forbidden
Date Posted: April 19, 2004 at 1:25 PM
I smell.......CLIPPING.....anyone else?
-------------
Top Secret, I can tell you but then my wife will kill me.
Posted By: kiteman
Date Posted: April 19, 2004 at 1:32 PM
When you say clipping, wouldn't the amp be shutting down into protecting mod, and the cumming back on? And Kicherstang you mentioned that fhase would control this? The phase switch on the amp and controls the RCA outputs coming out of the amp right? Also southside mentioned wiring up the speakers up backward is that the right way? Thanks
Posted By: DYohn
Date Posted: April 19, 2004 at 1:40 PM
No, a car audio amp will not shut down if it is clipping - well, some very expensive ones actually have clipping detenction circuits in them, but BOSS does not and they are VERY prone to clipping. This will fry your speakers. TURN DOWN THE GAIN! Set it properly. A phase switch on an amp or crossover will do the same thing as swapping the wires at the woofer. Turns + in - and vice versa. ------------- Support the12volt.com
Posted By: forbidden
Date Posted: April 19, 2004 at 1:41 PM
Throw phase out the window, it has no place in blowing a sub for this discussion. No an amp will not shut down due to clipping (unless it has a really really amazing protection circuit - not in this amp though). Wiring up the speakers backwards is also a phase issue and again it will not be affecting our outcome. Are you familiar with clipping and what it is and the same for phase? ------------- Top Secret, I can tell you but then my wife will kill me.
Posted By: Alpine Guy
Date Posted: April 19, 2004 at 4:50 PM
For those that don't know what clipping sounds like, , it kida goes like this. You hear boom boom boom, , then you turn it up more and hear humm humm hummm, , , that would be the signal clipping. Basically the sound waves are running into each other and makeing the sub try to fire out and in at the exact same time......That equals lots of heat, and a melted sub. Turn the gain down to about half way to 3/4 . What kind of cd player is he useing? ------------- 2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.
Posted By: customsuburb
Date Posted: April 19, 2004 at 5:21 PM
1. Set gain at zero on amp. 2. Turn your head-unit up untill you hear distortion coming from your mid and high speakers, then back down the volume to just before this point. 3. Now keep the volume at this point and turn the gain on your amp up untill you hear distortion coming from your subs. Turn the gain down just before that point. Some fine tuning will probobly be needed if you want to hear bass at lower volumes still.
Posted By: kiteman
Date Posted: April 20, 2004 at 9:16 AM
Okay, Clipping is what must be happening. He stated that he would be booming then he hears a small humm followed by the smell of something burning. The amps gain was only at 3/4 . I will go back and set it up the way customsuburb sugested. But one last question? should the speakers be wired out of phase? Thanks for all of your help guys.
Posted By: DYohn
Date Posted: April 20, 2004 at 9:51 AM
The setting (ie: "only at 3/4") of a gain control means nothing. It is NOT a volume control. The purpose of gain is to set the INPUT sensitivity of the amplifier to match the OUTPUT voltage from the head unit. Your amp is clipping and sending DC voltage to your speakers. They can't handle it. Wired out of phase? Huh? NO! They should be wired the SAME. Do you mean in reverse polarity? Yes, in general, loudspeakers mounted inverse should be wired + output from amp to - input on speaker. Unless the amp or crossover has a polarity switch, then you can use this to make the change if its needed. Try it both ways and if one connection gives you more apparent bass than the other, leave it there. But for crissakes set your gain properly first! ------------- Support the12volt.com
Posted By: kiteman
Date Posted: April 20, 2004 at 9:58 AM
Okay, Thanks again I'll try that later today when he shows up.
Posted By: flatulatta
Date Posted: April 22, 2004 at 9:26 AM
wow.... DYohn make a sticky post that shows how 2 properly set gain and wut it can do b/c there seems to be an excese of this questions
|