Newbie question about power handling

[dan5505 10+ year member]

Whats the difference between "thermal power handling" and RMS. For instance, on Re's website, all their sub specs have thermal handling. On Fi's website, they report RMS.

http://www.reaudio.com/specs.html#sp_se

https://ssl.perfora.net/www.ficaraudio.com/sess/utn;jsessionid=1547329b437a573/shopdata/0020_Q/product_overview.shopscript

Click to read more...

 

[Tiiimay 10+ year member]

i dont know what thermal is and im not going to guess because i have no idea. but RMS is constant power handling, thats all thats ever mattered to me.

 

[Immacomputer 10+ year member]

They are very similar stats and both are useful. Often times, thermal power handling is the RMS rating and other times it is not. Thermal power handling is how much power the voice coil can take before burning up. RMS power is how much the sub is able to take before doing damage to the sub/coil. Power handling can be mechanical or thermal as you can blow a sub while not burning the coil and you can fry a voice coil without causing mechanical damage to the sub.

 

[dan5505 10+ year member]

ok, cool. Thank you

 

[helotaxi 5,000+ posts]

Every RMS rating I've ever seen is thermal power handling. Thermal rating is independent of enclosure. Mechanical power handling is entirely dependent on enclosure. As such it is basically impossible for a manufacturer to provide a mechanical power handling spec without specifying a box along with the rating.

 

[BassBallin]

They are very similar stats and both are useful. Often times, thermal power handling is the RMS rating and other times it is not. Thermal power handling is how much power the voice coil can take before burning up. RMS power is how much the sub is able to take before doing damage to the sub/coil. Power handling can be mechanical or thermal as you can blow a sub while not burning the coil and you can fry a voice coil without causing mechanical damage to the sub.

good explanation

 

[Immacomputer 10+ year member]

Every RMS rating I've ever seen is thermal power handling. Thermal rating is independent of enclosure. Mechanical power handling is entirely dependent on enclosure. As such it is basically impossible for a manufacturer to provide a mechanical power handling spec without specifying a box along with the rating.

MTX actually uses free-air mechanical power handling for their RMS ratings or at least they used to back in the MTX 7000 days.

 

[businessjournal 10+ year member]

RMS and thermal power handling specs are set for a reason, of course, so how is it that some subs are able to take more - sometimes MUCH more - than they're rated? it differs across subs, of course, but how does one tell if it's safe -- aside from what you would hear on the forums and such?

I've got a guy in another board claiming that he can send 500 watts to an 8" sub rated at 150 watts RMS "as long as it's clean power." I call bullshit on this dude because we're not talking about AA or SS here - it's MB Quart.

 

[Immacomputer 10+ year member]

People think putting a sub on an amp rated at 500rms means that the sub is handling that power. This isn't the case as the gains and volume knob control how much power the sub is actually getting.

Some subs are overbuilt in the thermal power handling department but that doesn't mean they need that much power to reach decent output levels. My av12 can take around 1krms thermally but I had it approaching mechanical limits around 400-500rms. I don't need any more power past that but I know that the coil can take it.

 

[businessjournal 10+ year member]

People think putting a sub on an amp rated at 500rms means that the sub is handling that power. This isn't the case as the gains and volume knob control how much power the sub is actually getting.

understood by me, but that's not what I was really talking about. this isn't about running a sub on a monster amp with the gains down - it's about people saying "yeah that sub is rated at 500w but you can throw 1000w daily no problem."

if a guy says he's going to power a 150wrms sub with 500wrms, he's not talking about turning the gains down to compensate. he's talking about running it at 500wrms -- gains adjusted to that level and at a high enough volume to bump max.

 

[helotaxi 5,000+ posts]

500RMS means that the sub can shed the heat from that amount of power indefinitely without failure. This means a constant sine wave of that power fed to the sub. Music is nowhere near constant and the amp is nowhere near averaging out to that amount of constant output. RMS only matters on test tones. With music, it means nothing.

 

[Immacomputer 10+ year member]

Unless then the music you're listening to has constant tones in it close to 0dB. This can be present in some rap and electronic music.

 

[helotaxi 5,000+ posts]

Ah, yes the constant, annoying, loud as F hum in the background, or more like the only thing you would be able to hear. Not exactly music at that point.

 

[Immacomputer 10+ year member]

But some of us like music like this and listen to it often:

http://media.putfile.com/Nightmare-On-Bass-Street---Season-Of-Bass-29

 

[helotaxi 5,000+ posts]

Nowhere near constant. Sorry. I've got a lot of stuff with a more constant hum than that.