Underpowering Subwoofers...


Heathen

CarAudio.com Newbie
Aug 18, 2020
17
1
Auckland
I'm sure this info is already here somewhere, but my wording/terminology is not helping my search.

If I have a sub rated to ~1,000w, and I put it in a large, ported enclosure, can I proportionately decrease the power supplied to it.

E.G, could I put ~750w through that same speaker, and produce the same effect/spl as the ~1,000w in a sealed enclosure?
 

hispls

CarAudio.com Veteran
10+ year member
Sep 10, 2009
11,281
422
Central Maine
First of all, if speakers were hurt by too little power we'd all be blowing them up any time we weren't driving them at full power.

Really though, power handling comes in 2 parts, mechanical and thermal. For the most part whatever box you use should have little effect on how much heat the coil will take before it fails, and depending on what you're doing you can put several times "rated" power into a sub without breaking it mechanically, or if you're careless you can break most subs mechanically with much less than that.

Now """power handling""" ratings are often dishonest from the manufacturer, so you also have to know the score there too, but mostly if that's all you have to go on those numbers should be considered just a suggested amplifier rating to pair with them.

I guess if you want a better answer tell us precisely which sub, your box specs, and which amp and we might give you a better idea of how much you'll need to be wary about breaking something.
 
OP
H

Heathen

CarAudio.com Newbie
Aug 18, 2020
17
1
Auckland
...
I guess if you want a better answer tell us precisely which sub, your box specs, and which amp and we might give you a better idea of how much you'll need to be wary about breaking something.
It's more the mechanical aspect of damage that I'm thinking of.

Expecting that, with no "air cushion", the enclosures in the attached images (and associated recommended Power Handling) would be a legitimate guideline.

I saw this with three manufacturers manuals.

Attached image shows sealed vs ported power handling from same manufacturer for the same subwoofer.
 

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hispls

CarAudio.com Veteran
10+ year member
Sep 10, 2009
11,281
422
Central Maine
"air cushion"
At or around tuning the port will be in-phase with the diaphragm and you will actually get very little cone movement at tuning. Improperly built port or playing below tuning is another story, that'll be like playing free-air. If you tune your box to 45hz and try playing 20hz sine waves you'll probably break your subs before the rated power.

That all said, Kicker continuous power handling ratings should be pretty honest and provided you're not actually trying to break them, if you pair them up with a Kicker (or other honestly rated) amp of that rating they should be near indestructible. If you go ported just make sure you either use subsonic filter or be careful if you're playing tracks with very low material. Also be sure your ported box is built properly with adequate port area and tuning you need to play whatever it is you're trying to play with them.
 
OP
H

Heathen

CarAudio.com Newbie
Aug 18, 2020
17
1
Auckland
Thanks for the informative reply.

So - if I build an enclosure/port to Kicker's recommendations, I can still put the full 600w through it?

Why would they say to power it at ~3/4 of it's rating? Trying to cover themselves?
 

Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,451
767
South Coast Metro, CA
Id be worried about clipping more than mechanical limits unless you listen to bass modified music with a loy of 30hz and under information. Most music out there doesn't even get close to 30hz so i doubt youll have any real mechanical issues even without a subsonic filter. The wattage stated on the amp is not the real wattage the sub sees. Theres always box rise to account for so clean wattage, the sub can handle much more than what your amp has. If you hard clip the amp, then you'll blow it regardless even with half the rms rating. Always have a lot of headroom of amplifier power so you dont have to redline the amp causing excess heat/wear along with distorted and clipped signal that comes with red lining the amp. Vs having a **** ton of headroom with a lot of power on tap having the amp barely lift a finger to get the output you need, keeping cool, efficient, and minimal THD.
 

hispls

CarAudio.com Veteran
10+ year member
Sep 10, 2009
11,281
422
Central Maine
So - if I build an enclosure/port to Kicker's recommendations, I can still put the full 600w through it?

Why would they say to power it at ~3/4 of it's rating? Trying to cover themselves?
Brands I'd consider good will rate woofers at a point where it's nearly indestructible, that way people who don't know what they're doing won't break them and if any warranty claims come in with, say, burnt coils, they KNOW that it was abused.

Anyway, Kicker box specs are going to be the box too small and the tuning too high. I'd highly recommend making a post and someone with some box design software handy can help you dial it in a little better.

Again, if Kicker rates those 600W and you get an honestly rated 600W amp to pair it with you should be safe unless you're being very abusive.

Id be worried about clipping more than mechanical limits
You would be hard pressed burning a 2" 4 layer coil off an amp that can only make 600W even with a hard clip. Clipping isn't some mysterious boogeyman that automatically blows speakers or everybody listening to rock or metal (the sound of which is largely created by driving their amps into clipping) would be blowing shit left and right. In fact the difference in power (heat) between a square wave and sine wave is only .707 which is where we get RMS vs peak to peak. This can be proven close enough by just drawing two waves with equal amplitude and wavelength on graph paper, one square one sinusoidal. Fill in the waveforms with color and count the area with the squares. Everything within the waveform is power.
 

Jeffdachef

Gunz That Turn on Nunz
Feb 5, 2013
18,451
767
South Coast Metro, CA
Brands I'd consider good will rate woofers at a point where it's nearly indestructible, that way people who don't know what they're doing won't break them and if any warranty claims come in with, say, burnt coils, they KNOW that it was abused.

Anyway, Kicker box specs are going to be the box too small and the tuning too high. I'd highly recommend making a post and someone with some box design software handy can help you dial it in a little better.

Again, if Kicker rates those 600W and you get an honestly rated 600W amp to pair it with you should be safe unless you're being very abusive.


You would be hard pressed burning a 2" 4 layer coil off an amp that can only make 600W even with a hard clip. Clipping isn't some mysterious boogeyman that automatically blows speakers or everybody listening to rock or metal (the sound of which is largely created by driving their amps into clipping) would be blowing shit left and right. In fact the difference in power (heat) between a square wave and sine wave is only .707 which is where we get RMS vs peak to peak. This can be proven close enough by just drawing two waves with equal amplitude and wavelength on graph paper, one square one sinusoidal. Fill in the waveforms with color and count the area with the squares. Everything within the waveform is power.
it would depend on how long the bassline is. Extended squarewaves will eventually overheat the coil and seriously? A hard clip on a 2 inch voice coil on 600 watts would definitely blow subs. I've seen some blow with less power not even accounting box rise.
 

hispls

CarAudio.com Veteran
10+ year member
Sep 10, 2009
11,281
422
Central Maine
it would depend on how long the bassline is. Extended squarewaves will eventually overheat the coil and seriously? A hard clip on a 2 inch voice coil on 600 watts would definitely blow subs. I've seen some blow with less power not even accounting box rise.
AC power is AC power. If the coil can hold 600W of heat it doesn't matter what shape the waveform is so long as it is less than that.
 

THATpurpleKUSH

Smoke weed everyday
10+ year member
Sep 30, 2009
7,880
663
Slums of the Shaolin
The coil needs to move to dissipate heat. When the coil tries to play the extended flat spot of a squared wave that is when heat builds and lack of movement retards air flow which inhibits cooling.
 
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ThxOne

AudioFreak
Jun 8, 2018
2,559
461
Saint Marys, GA
Think of it like the gas pedal in your car or truck... underpowering or keeping the rpms under 2,000 will get you greater gas mileage while flooring the pedal or driving near redline will raise heat and you wont get as good of gas mileage... but as we know, it is more fun. So no, it won't hurt underpowering subwoofers, they will run cooler and last longer... they just won't be as fun.
 

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