Having examined the data sheets of 18 sound’s comp drivers in recent days, I’m intrigued by the fact that depending on the 8 or 16 ohm version, there are notable differences in the frequency response, with a tendency to more accidents and decrease in the UHF region for the 16 ohm versions.
The impedance curves also tend to exhibit more accidents with several maxima.
Only explanation I came up til now is that the 16 ohm versions involve a greater distance between core and diaphragm (due to longer moving coil??).
Anyone can comment on the above?
The impedance curves also tend to exhibit more accidents with several maxima.
Only explanation I came up til now is that the 16 ohm versions involve a greater distance between core and diaphragm (due to longer moving coil??).
Anyone can comment on the above?
Normally, all drivers with the same mass of copper in the voice coil behave the same, no matter how it is distributed. That can be easily seen with dual VC drivers where we have a 4:1 impedance ratio (series vs parallel).
With a 2:1 ratio things get tricky, for the same mass you need sqrt(2) times the wire length and 1/sqrt(2) times the wire cross section area (because (BL)²/Re must stay the same).
This is conflicts with the requirement for the same fill factor in the gap when using round wire, and for thin wire the isolation thickness plays a role, too. With rectangular wire it's easier but still the the total mass and thus (BL)²/Re will often be slightly different which makes the driver behave slightly different.
“which makes the driver behave slightly different.”
I find the differences in the drivers mentioned in my first post quite significant, even though the 8ohm response curves are probably more smoothened than the 16 ohm ones. I’m looking for instance at the nd1480A with a steep drop above 7khz for the 16 ohm version whereas the 8 ohm version remains incredibly stable.
I find the differences in the drivers mentioned in my first post quite significant, even though the 8ohm response curves are probably more smoothened than the 16 ohm ones. I’m looking for instance at the nd1480A with a steep drop above 7khz for the 16 ohm version whereas the 8 ohm version remains incredibly stable.
The datasheet measurements seem to have been produced by different measurement systems and have different smoothing applied (look at the impedance plot), different acoustic setup etc.
I don't think that allows for a fair comparison, rather I'd think one and the same specimen would just show as much variation.
