what determines rms?

[Hydrastas 10+ year member]

i've always wanted to picture why one sub can take more power than another. i thought i halfway had it envisioned but then i saw a sub with 180 oz magnet with 1250 rms, followed by a sub with 250 oz magnet and only 1000 rms. is excursion a big factor here?

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[dman4486 5,000+ posts]

the weight of the magnet means nothing about rms

rms is ROOT MEAN SQUARE

this is the power at which a manufacturer recommends, to keep the driver within mechanical AND thermal limits

edit: ^^^very very dumbed down basic definition

 

[528hz 10+ year member]

It's primarily dependent on motor capabilities and coil thinkness/strength right? I really don't know to be honest.....just guessing.

 

[NDMstang65 10+ year member]

No

It depends on how much mass/material you have available with the coil and its ability to either soak up or dissipate heat. Ideally you want the coil to kick off heat (which is why we have our cooling options and the new inductance heat ring option with the new BTL's)

A wise person will never rate a RMS at close to the thermal failure spot. Ideally you want to rate it much lower than when it will break...both thermally, and mechanically.

 

[Electrodynamic 10+ year member]

No
It depends on how much mass/material you have available with the coil and its ability to either soak up or dissipate heat. Ideally you want the coil to kick off heat (which is why we have our cooling options and the new inductance heat ring option with the new BTL's)

A wise person will never rate a RMS at close to the thermal failure spot. Ideally you want to rate it much lower than when it will break...both thermally, and mechanically.

+1

Enclosure size and type also has a lot to do with power handling although a lot of mfg's don't address it.

 

[PaulD 10+ year member]

^^^what the last two guys said. Speakers are very inefficient, typically around 5% iirc. That means 5% of the electrical energy is converted to sound, the other like 95% is wasted as heat - which must be dissipated.

 

[pd8731]

Drivers don't have an RMS. They have power ratings. Amps have peak power and RMS power.