diffrent voice coil

[palesha]

I hv got one titanium dome tweeter with aluminium voice coil. The same is alsoavailable with copper voice coil. The spl level of cu voice coil tweeter is reduced by 2~2.5 db, but the frequency reaponse is almost the same. The voice coil size is 1.75 inches. The aluminium tweeter is specified for 40W RMS. What watts(power) to assume for copper voice coil tweeter? What r other advantage & disadvantages 4 cu voice coil tweeter?

[AndrewT]

Hi,
-2db would require 63W to match the Al VC @40W.
The Cu Vc (if = section and turns) will have a lower resistance affecting Q but in a tweeter this may not be significant. The lower resistance will generate a little less heat.
However the two voice coils may not be physically the same. The wire section and the number of turns could both be different.

[palesha]

As the copper has more heat dissipation capacity, how much more power copper voice coil can handle?

[simon5]

I'd say about double, 80W.

[AndrewT]

Hi,
why should a copper voice coil have more heat dissipation than an aluminium VC?
Radiation into the pole pieces and turbulent convection (fast moving voice coil) through the air gap seem the only exit routes.

I suspect that the convection route is a significant proportion leaving only a variation in emissivity to improve the total heat dissipation of the Cu VC.
Again I suspect that the total increase from Al to Cu is likely be be less than +10%.

Is there a speaker manufacturer listening?

What effect will ferrofluid have on dssipation? Will it distinguish between CU & Al?

[sreten]

Hi,

tweeter voice coils are like fuses, long term dissapation is not really
the issue, its how quickly the tweeter will blow when overloaded.

(tweeters are like quick flow fuses, bass units like slow blow fuses)

Consequently the critical issue is thermal mass, or the thermal time
constant of the voicecoil. This obviously depends on mass and so
you have a trade off between ruggedness and the drivers ability to
produce treble.

The biggest effect of ferrofluid is the impact it has on the time constant,
by increasing thermal mass and providing a heat conduction path.

The conduction path does increase long term power handling significantly,
but only under very controlled conditions is this really relevant.

Also note the voice coil former being integral with the voicecoil
is a major influence on total thermal mass and the time constant.

/sreten.

[AndrewT]

Hi Sreten,
trying to read between the lines.
Are you confirming that the difference in dissipation between AL & Cu is minimal?

The big change is weight and it's direct affect on efficiency already confirmed by the +2db to +2.5db.