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AR-11 Midrange (200010-1) Measurements

Pete B

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AR-11 Midrange (200010-1) Measurements 9/17/05:

Midrange #1:

Red label indicating that this was replaced

Date code : 561 8018

Fc = 464.6 Hz

Re = 3.15 ohms

Qe = .92

Qm = 3.15

Qtc = .71

Midrange #2:

Appears to be original

Date code: 561 7812

Fc = 514.9 Hz

Re = 3.18 ohms

Qe = 1.04

Qm = 3.17

Qtc = .78

The impedance curve looks primarily like a simple sealed system with a fundamental resonance of 12.9 ohms at 521 Hz. Impedance is 4.0 ohms in the pass band at 3 kHz. There is a very small secondary peak of 4.27 ohms at 1098 Hz.

The build quality looks very good in contrast to the tweeter.

Neither the midrange or tweeter utilize rear chambers and it is clear that the acoustical response is part of the crossover network. The midrange Fc being close to the crossover point, and the Qtc of .7 could form one section of a Linkwitz-Riley 4th order response. The acoustical response being one 2nd order section and the electrical being the other if properly designed.

The large increase in impedance suggests that ferro fluid was not used in these drivers.

I don't like the idea of an acoustical filter in front of the dome, however the construction of this filter appears to be well done.

Pete B.

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