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In Reply to: RE: TAD 4002 crossover advice posted by JLH on November 05, 2009 at 05:56:43
If the TAD driver is 'voiced' for 10-12db of resistive attenuation, and for the response anomolies of a specific (TAD) horn, then the best way tio ensure neutral response is to use the driver under the same conditions it was voiced for (same horn and method of attenuation), as you said. Using non-resistive attenuation alters the driver voicing by substantially decreasing Qe (essentially this strengthens the motor). This is much like using non-resistive attenuation on a horn-loaded cone driver that has been voiced for a specific horn with series resistance used for attenuation.
What I don't understand is why a more 'neutral' horn would resolve the driver response deviations that might arise due to not using resistive attenuation. If the driver has been voiced with a specific horn or horn family, so that it has built-in compensation (response anomolies) for response errors in the horn, then using the driver with a different horn or family of horns leaves the drivers built-in voicing response changes (peaks and dips) without a corresponding (and opposite) horn response error. For example, built-in driver peaks have no corresponding horn dips to cancel out, so they are left exposed as peaks. It would seem that switching to a 'more neutral' horn would consistently result in improved response only in the case of a 'neutral' (non-voiced) driver. For voiced drivers the result would be a hit or miss proposition. While this oversimplifies things (there are many other design considerations including compression chamber shape and volume, phase plug design, diaphram mass and stiffness, surround damping, etc.), the motor strength is an important determinant of driver performance, so substantially changing it should produce response changes. It would be interesting to see the response graphs of a voiced TAD driver (into a plane wave tube) with and without resistive attenuation, just to see the impact of changing the motor strength.
Of the commonly used drivers (TAD, Altec, JBL, B&C, Radian, etc.) do you have any idea which drivers are voiced and which are 'neutral' (for example, designed for flat response with a plane wave tube). If we don't know this, then driver-horn selection is a try it and 'see' proposition.
Regards,
Bob
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