Unless the two loudspeakers are identical, there will be some modification of the frequency response of BOTH speakers. It does not matter which is first and which is second in the series.
The difference may or may not be small, it depends on the specifics. Try it and see what you think.
I disagree with imhififan’s opinion that the crossover points will change. In my experience, they do not. But each speaker’s frequency response will be modified by the other speaker’s impedance curve being in its signal path. If the two impedance curves are identical, then so is each speaker’s sensitivity to the other’s impedance curve, and the net frequency response of each is unchanged. But if their impedance curves are different, then there will be changes in the frequency response of both speakers.
(For geeks only: It is tempting to think of each speaker as a resistor in series with the other, thus ruining the amplifier damping factor for both and effectively doubling the woofers’ Qes, but this is also incorrect, because each speaker also has its own motor strength. Assuming generally similar speakers the DC resistance is approximately doubled but so is the total motor strength, therefore woofer Qes is not degraded. This is a different situation from adding an equivalent series resistance, in which case only the DC resistance would be doubled [with total motor strength remaining the same], in which case the effective driver Qes would also be doubled, as predicted by the calculated degradation in effective amplifier damping factor.)
Duke
speaker designer
The difference may or may not be small, it depends on the specifics. Try it and see what you think.
I disagree with imhififan’s opinion that the crossover points will change. In my experience, they do not. But each speaker’s frequency response will be modified by the other speaker’s impedance curve being in its signal path. If the two impedance curves are identical, then so is each speaker’s sensitivity to the other’s impedance curve, and the net frequency response of each is unchanged. But if their impedance curves are different, then there will be changes in the frequency response of both speakers.
(For geeks only: It is tempting to think of each speaker as a resistor in series with the other, thus ruining the amplifier damping factor for both and effectively doubling the woofers’ Qes, but this is also incorrect, because each speaker also has its own motor strength. Assuming generally similar speakers the DC resistance is approximately doubled but so is the total motor strength, therefore woofer Qes is not degraded. This is a different situation from adding an equivalent series resistance, in which case only the DC resistance would be doubled [with total motor strength remaining the same], in which case the effective driver Qes would also be doubled, as predicted by the calculated degradation in effective amplifier damping factor.)
Duke
speaker designer