How to Underpower a sub

[synikalt 10+ year member]

I hear about this all the time...But what is it really..i know HOW its bad for the sub but i really dont know why. I was arguing with a guy at work saying that underpowering a sub cannot blow it.

he thinks it can, i just explained underpowering a sub is just bad for the amp, because peole turn up amp to get more out of sub, and turn up volume on deck..and sometimes it can clip the amp...then some AUDIO guy...hes the owner of shop, looked at my subs and amp (i had 1 channel visonik 800w and 2 rockfords he with one frozen) told me that by underpowering subs, the amp goes into protect and converts the AC power to DC and sends it to the subs.

this souds reasonable but is this corect or was i missing something? or was i wrong all along //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Click to read more...

 

[mattf 5,000+ posts]

I hear about this all the time...But what is it really..i know HOW its bad for the sub but i really dont know why. I was arguing with a guy at work saying that underpowering a sub cannot blow it. he thinks it can, i just explained underpowering a sub is just bad for the amp, because peole turn up amp to get more out of sub, and turn up volume on deck..and sometimes it can clip the amp...then some AUDIO guy...hes the owner of shop, looked at my subs and amp (i had 1 channel visonik 800w and 2 rockfords he with one frozen) told me that by underpowering subs, the amp goes into protect and converts the AC power to DC and sends it to the subs.

this souds reasonable but is this corect or was i missing something? or was i wrong all along //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif

Pretty sure you are right.

 

[BASSMEKANIK 10+ year member]

well usualy distortion causes heat... when underpowering a sub and pushing it to the point where the amp starts distorting it tends to make the coils crap out on the cheaper subs...

 

[phyphoestilic 5,000+ posts]

In otherwords its overpowerin an amp.

 

[adam71 5,000+ posts]

well usualy distortion causes heat... when underpowering a sub and pushing it to the point where the amp starts distorting it tends to make the coils crap out on the cheaper subs...

Over driving an amp to clipping can burn a voice coil.

 

[BASSMEKANIK 10+ year member]

Over driving an amp to clipping can burn a voice coil.

//content.invisioncic.com/y282845/emoticons/word.gif.64b12e39f936af3b4fff38a1c0bd0244.gif

 

[Tempe 10+ year member]

http://www.audiogroupforum.com/csforum//showthread.php?t=4332

Specifically read this reply. I don't think I've ever read/heard a better explaination of "underpowering a subwoofer."

Tempe

 

[synikalt 10+ year member]

some AUDIO guy...hes the owner of shop, looked at my subs and amp (i had 1 channel visonik 800w and 2 rockfords he with one frozen) told me that by underpowering subs, the amp goes into protect and converts the AC power to DC and sends it to the subs.

Was he Right? i dont think so...Everyone goes to This guy cuz hes 1 of 3 dealers in my small hometown, i really dont think he knows THAT much about car audio, in fact i dont think he knows What hes talking about sometimes...but he knows enough to run a car audio store.

He also told me a while back that not to even attempt to Try a ported box in a mustang..theres not enough room and it will sound like shit. i built my box and it fits im about to put 2 10'' ATOMIC AP/SPL once my amp comes in ported 4 cubes tuned at 34hz WTF!!

 

[Tempe 10+ year member]

An amplifier always puts out AC power. What Manville Smith was saying is when the amp is driven normally the speaker is moving in and out in relation to the oscillating signal coming from the amplifier. When the amp is driven into hard clipping there is not that millesecond of time between each half wave cycle where the voice coil is not recieving power. Think of things this way.

Plug a 600-800 watt sub into an electrical outlet. It should handle the bursts of power. I mean hell I've even seen a video of some $15 open box special woofer taking the wall socket for some time. The power applied to the voice coil in breif bursts gives it time too cool down. Now if you plug that 600-800 watt woofer into an outlet for a very long time, you will get some stinky coils, and eventually (from lack of experience I don't know how long) I'm sure that voice coil will fry.

This is not a fair comparison, but it gives you the general idea.... I hope...

Box shape, port firing direction, and sub firing direction play a huge role too. If the box is huge in relation to the size of your trunk, the woofers are right up against the rear wall of the trunk, and there is no room for the bass to enter the cabin, yeah the bass may sound aweful.

T

 

[helotaxi 5,000+ posts]

When you fully clip an amp, it is producing way more than its rated power. Roughly double in fact. Therefore if you have a 400WRMS amp running to a 400WRMS sub but running fully clipped, the amp is theoretically supplying twice the rated power to the sub. This will usually blow the sub. Not becuase it is a clipped signal or that the sub is moving differently, cause it really won't be moving that much differently, but because the thermal power handling limit of the sub has been vastly exceeded. You CAN do the same thing with an amp rated for less power than the sub can handle because the amp could again theoretically produce 2x its rated power but again the clipping itself still has nothing at all to do with the blowing of the sub, exceeding the subs thermal capability does. A sub should be able to handle a 400w square wave just as well as a 400w sine wave. In fact the peak power on the sine wave would be higher.

 

[nauc 10+ year member]

think of it this way

if you have a 100 watt sub and a 75 watt amp, and clip the amp, it could be like sending the sub 150 watts, which will burn up your sub

so many will use a 100 watt amp or MORE so they can give the sub its 100 watts without any chance of clipping

 

[jmanpc 5,000+ posts]

Its impossible to blow a sub by underpowering it. I ran a 350w sub 50w all afternoon and overnight on a 45hz tone, unclipped, and the woofer was still cold. You can be a dumbass and crank the gains, though.

 

[pikers 10+ year member]

Its impossible to blow a sub by underpowering it. I ran a 350w sub 50w all afternoon and overnight on a 45hz tone, unclipped, and the woofer was still cold. You can be a dumbass and crank the gains, though.

OK, but the problem of course is that it won't be "loud enough" in most cars, and then the gains get cranked.//content.invisioncic.com/y282845/emoticons/eek.gif.771b7a90cf45cabdc554ff1121c21c4a.gif

 

[PatFitz9 10+ year member]

there is a huge difference between underpowering a sub, and using an amp that isn't powerful enough. i hear this all the time "underpowering a sub is bad" thats BS. if that was the case, you could never turn the volume down.

all too often, people think that the gain knob is volume control. so a hundred watts on a hundred watt amp = full tilt. sending the sub a bad signal that is less power than what it can take will damage it, but I wouldn't call that underpowering the sub.

 

[JohnBlayz142 10+ year member]

Underpowering a sub will NOT blow it.

Clipping does not equal underpowering.

Distortion (clipping) will blow a sub.

/thread.