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Dave,
thanks for following my point, but you're comparing apples to... wrong apples. The counter-voltages is created by the moving coil at its terminals and you can safely forget here about coil's impedance. So you shouldn't compare the added resistance to the coil's Re resistance, but to the speaker wires' + amplifier's impedance! Which in a good hi-fi setup is less than 0.1-0.2 ohm. Rs/Rline ratio, where Rs is the speaker impedance on its resonant frequency (from 15 ohm to 50 ohm for speakers relying on Qes rather then Qms; I consider such speakers to be proper ones) and Rline is the impedance of amp output and speaker cables, is called a damping factor. And you've got to trust me (unless somebody more respectful like Snow James Mobile chimes in) that it is *very* noticeable when damping factor goes changed by factor of 10! (*) (old setup with 'proper' Rline = 0.2ohm: average Rs 30Ohm / Rline 0.2 ohm = 150; new 'series' setup: 30 / (2+0.2) ~= 15)
The only scenario when a such mod won't reveal itself is when:
- the speaker is designed to rely on Qms only (low Qms, high Qes) - i.e. mechanical brakes; but these boys have poor impulse response
- the amplifier is of old design with low-performance transformer in its output stage (like those cheap-to-mainstream tube amps from '50-60s) which gives it high output impedance - poor electrical brake for the speaker
- the whole setup is *ALREADY* featuring cheap thin speaker cables having significant resistance (I won't be surprised to measure those mentioned 2 ohms across a thin 10 ft cable) - i.e. the connection between bouncing coil and electrical brake on the amplifier is very VERY weak.
For you convenience I'm including an impedance graph (blue line goes for the phase) for a good bass driver.
Cheers,
Zig
(*)
I mean 1..200 range. For sure it won't make significant difference if the damping factor goes changed from 200 to 2000 or from 0.5 to 5.
posted by 188.134.4...
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