Why are capacitors at times connected to the terminals of speakers and how do they vary in their different sizes
If the capacitor is in series with the speaker, it may be there as a DC blocker and/or a high pass filter. The corner frequency where the lower frequencies will start to roll off can be calculated. You did not provide the speaker impedance. eg: 8 Ohms, 4 Ohms or 3.2 Ohms, etc. You did not specify the capacitor value in microFarads (uF). If it is several hundreds of microFarads or higher, it's just a DC blocker. If it is only a few (less than 10 uF), it's a tweeter high pass filter.
Use the equation to calculate the -3dB corner frequency of the high pass filter:
f = 1 / (2 * Pi * C * Xc) where:
f is the corner frequency where the signal is down 3dB (voltage down to 70.7% & power down 50%)
Pi = 3.1416
C is the capacitor's capacitance in Farads ( 1uF = 0.000,001 Farad)
Xc is the loudspeaker impedance in Ohms.
I have an old Sony STR110 receiver upstairs. Internally, its amplifier has 470uF capacitors in series with the output terminals for blocking DC. I can tell by using the above equation that, if I connect it to 4 Ohm speakers, the bass rolloff starts about 85Hz. Hardly acceptable for Hi-Fi with no bass below 85Hz!
Bob