Impedance question, please help me Mr. Wayne


Dear Mr. Wayne,
Hi, it's me again. I just decided to buy some speaker driver for my new system, it consist of:
Woofer, 2ohm, 94dB, low pass 400hz
Mid, 2 ohm, 96dB bandpass 400-4000hz
High, 4 ohm, 95dB hi-pass 4000hz
all sensitivity is in 2.83v/1m.
I want to know is the impedance of the driver "in the system" will affect the sensitivity? I mean, with my choice, I assumed that my system will have a sligthly weak in high and even weaker in low if the impedance is the same for all three driver (I also know that's an odd choice, but that what I want:)), but how if the impedance is like my driver choice above?
And what is the total impedance for the system above?
If I add a second same woofer (with the same lo pass and drive with different amplifier with the same watts) is that will make the sensitivity of my low section raise with 6dB (like parrarel two similar driver)?
Thank's in advance.

Regards,
Gabriel Temmy


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