Likleyhood of blowing a subwoofer

Zaigrith

I have an SVS 20-39pci and am thinking of using it for music at a party. I am going to want to have it turned up as much as I can safely get away with while maintaining quality. It has its own amp built in, but I do not know much about it. I would imagine that the amp limits itself before going to unsafe levels but i have no idea. Any thoughts on this?

TNRabbit

Most new subs have built-in protection; I'd confirm with the manual, though.

treitz3

Yeah, if you hear the sub bottoming out and/or producing distortion even once? Turn it down.

Zaigrith

From SVS: "There is a basic limiter in the amp but it's not tuned to be very aggressive. That is, it'll help prevent overexcursion but it's still possible to overdrive and bottom (and eventually damage) the woofer at high enough levels. Common sense and proper calibration are the key to maximizing the lifespan of the sub."
They also sent me a manual which I could not find on their site.

Gulfstrings

treitz3 wrote: »

Yeah, if you hear the sub bottoming out and/or producing distortion even once? Turn it down.

Can you help me understand what "bottoming out" is?

Much appreciated.

jbooker82

Gulfstrings wrote: »

Can you help me understand what "bottoming out" is?

Much appreciated.

When the speaker cone trys to exceed its limit of travel. Like a dog that is on a chain. Running full speed until it hit the end.

treitz3

Gulfstrings wrote: »

Can you help me understand what "bottoming out" is?

Hmmm, that's kind of hard to describe. It's kind of a weird sound that a sub will male when it bottoms out. This can include, but not be limited to, a click or a cardboard-like sound that would kind of emulate the sound that would be heard if you tapped the side of a hollow cardboard box with a blunt hammer. That's a real good question that is hard to put into words.

Once you can recognize it, turn it down. Maybe someone else can offer a better description of what you might hear when bottoming out a sub.

What happens is that basically, you are throwing the woofer excursion beyond the limits of the voice coils and/or beyond the limits of the surround. Both are a bad thing that you want to avoid at all costs.

zarrdoss

Subwoofer bottom out is where you exceed the mechanical limits of the sub and the voice coil slams into the backing plate, sometimes it will bend the voice coil and it will sound blown, or the spider will become separated from the cone as well. It can range from a gentle sounding tap to sounding like someone shooting a deck of cards out of a gun into a steel plate.


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Gulfstrings

Thanks, appreciate the explanation. Never have experienced anything like that.

Guess I need to turn it up a little ...

aboroth00

Gulfstrings wrote: »

Thanks, appreciate the explanation. Never have experienced anything like that.

Guess I need to turn it up a little ...

It's pretty damn scary when the sub bottoms out. First time I heard it I thought a gun had gone off in the soundtrack. Basically it's metal on metal and it doesn't sound pretty more like a loud "clunk."

PerfectCreature

A polk rep I talked to advised me to flick the cone of the woofer with your nail (not to hard that it hurts!) when it is not in use and keep that sound as a rough estimate as what it would sound like when tuning.

Tour2ma

zarrdoss wrote: »

... sounding like someone shooting a deck of cards out of a gun into a steel plate.

That's pretty damn accurate... and a great deal more PC than the "metallic ****" description that lept to my mind.

One thing for sure.... once heard it's not easily forgotten.

VR3

http://www.youtube.com/watch?v=VsQFRoqmOIE

Sounds like that ^^^

thetawave2

One thing you can do to keep your sub happy is running a desk fan over the heat sink. My sub used to get really hot and even smell when it ran at high volumes for a long time, but running my roommate's Vornado over the back of it completely fixed that.

VR3

That is a good way to fry your amplifier more than likely.

If it gets to hot and the fan is cooling it externally the protection circuits may not kick in... thus roasting your amp.

Amps get hot - let it get hot. It will let you know if it doesnt like it. Most all of these amps have clip lights. Use them

Tour2ma

^ I see what you're saying, but don't agree with your conclusion.

Heat is the destroyer thus the thermal nature of the protection circuits (vs. current, voltage, etc.). If a fan removes heat generated in excess of the design convection rate and thus prevents the protection from kicking in, the amp doesn't know the difference.

VR3

I only speak from experience..

The problem I encountered was you are cooling the heat sink - not the board itself. The board is just as hot as before but the heat sink was cooler. I have fried an amp this way...

Could just be a coincidence.

treitz3

Fellas, I believe both of you are right. It may just be dependent upon the design of the amplifier itself.

thetawave2

But cooling the heatsink allows it to draw a lot more heat off the amplifier. It's why computers have fans. The purpose of the heatsink isn't just to get hot, it's to dissipate heat. Circulating air around it lets it do that better.

Airplay355

I think he's saying while cooling the heat sink does help, there's a point where you can abuse the amp so much that it will produce damaging amounts of heat faster than the heat sink can dissipate it. After all, the heat originates in the board and then must move into the heat sink and then transfer to the air.

So while it may help, you are removing one of the warning signs of an amp being driven to the max and won't be able to tell how much is too much until it goes boom.

Sure it will help, but it's not guaranteed way to save your amp.

thetawave2

Oh certainly it's no guarantee, but I really don't consider a couple hours of music where the sub isn't close to distorting and it isn't receiving clipped signal to be dangerous.

felipecryte2011

I'm new here in the forum
sorry to bother,
but need help from you guys!
http://www.polkaudio.com/forums/showthread.php?t=118707