The soundtracks for most films on DVD are mixed so that most, if not all of the dialogue is located in the centre channel. Music and environmental sounds are distributed through all of the channels, but are usually kept at fairly low levels in the centre channel to help with clarity. The symptoms you describe are typical of a situation where the centre-channel signal or missing or is very low in amplitude. I would start by checking the wiring, to ensure that the centre channel is properly connected to the centre-channel output from the amplifier. If the speaker cable was damaged or if the centre-channel was wired to another channel by mistake, most of the dialogue would be missing. You can check the centre-channel wiring by swapping the speaker cable with one from another channel. I would also check to make sure the centre-channel speaker is working properly by connecting it to either the left- or right-front channels. This is a quick way to check for a faulty speaker. If there are no problems with the wiring, there may be a problem with the setup or operation of the system. The centre-channel level may have been set too low relative to the other channels when the system was configured. The signal level of each channel in a surround-sound system can be adjusted to ensure that all speakers are equally loud at the listener’s normal seating position. Many surround-sound receivers and preamp / processors can generate a pink noise signal during setup to help the user balance the audio level of each channel. Another possibility is that a fault could be present in the centre-channel circuit in your amplifier, preamp / processor, and/or receiver. If the operation of the speaker and speaker cable have been validated and the volume levels of the three front channels have been set to the same level, you should hear the pink noise test signal at approximately the same volume level, assuming the centre-, left-, and right-channels speakers are equally sensitive. The noise signal should also sound the same on all three channels, again assuming that the tonal balance on all three speakers is approximately the same.