Temperature effect on voice coil resistance

[AudioFreak]

How much can the resistance of a typical voice coil change over its operating temperature range assuming frequency remains constant? From the calculations I've done I figure that it will increase about 2.5ohms when temperature goes from 25 degrees celcius to 250 degrees celcius .... am I on the right track?

[GRollins]

Without going through and doing the math from scratch, I can't say whether that's exactly right, but it does sound as though it's in the ballpark.
The winding geometry (how many layers deep do they wind the coil), the coil former composition, vented spiders and/or pole pieces and other such arcana figure into how well the critter will shed heat, so it's difficult to relate the temperature rise to actual in-the-room music playing conditions. But if you're side-stepping those considerations and looking at it purely as temperature vs. resistance rise, then I'd say you're on the right track.
Doesn't the ESP site have some notes on this (perhaps in the active crossover section?), or am I thinking of another site?

Grey

[AudioFreak]

Thanks Grey,

I got my info from the 5th edition Loadspeaker Design Cookbook then did the maths.

Oh and yeah i am looking at it purely as resistance vs. temperature.

[Geoff]

Nearly right, Grey. It is in the passive crossover article:

http://sound.westhost.com/lr-passive.htm

[GRollins]

Thanks, Geoff...

Grey

[AudioFreak]

Well after reading all the data and doing the maths again i've come to the conclusion that the resistive component of the driver in question (Re 5.7) will rise to about 14-15ohms when temperature goes from 25 degrees celcius to 250 degrees celcius ........ as to whether the voice coil of this particular driver will ever get this hot under normal operating conditions i dont know cause i havent gotten that far yet....