audio quality poor on ripped movie DVDs

[JohnnyBob]

I have a Dolby Digital 5.1 sound system (Durabrand HT-3917) which works fine with ripped movies that have AC3 5.1 channels, but many of the older movies have only 1-2 channel sound. I'm noticing that many recently acquired and ripped older movies have poor sound quality. I'm not sure if it's something wrong with the ripping process, or a poor digital recording of the original DVD, or something wrong with my sound system. Most of the stereo (2 channels) movies play OK, but some of them sound very clipped or strange with an echo, like down in a barrel. Examples of older ripped DVDs with poor audio include Circus World (1964) John Wayne, and Duel in the Sun (1946) Gregory Peck.

I got this Dolby 5.1 sound system precisely for that reason, because my old TV sound system wouldn't give good audio quality. It has worked fine for almost 2 years, but now something seems to be going wrong. What? How do I troubleshoot this? Could my sound amplifier be developing a problem? In these cases the sound is also poor quality on my computer system which has 2 speakers and stereo, using PowerDVD. So I think it's for real, not just a fault of my standalone Dolby system.

I notice that with the ripped movie discs with 2 channel audio, the sound only comes out of 3 of my 5 speakers, the middle and two front speakers. The two rear speakers have no sound, so the overall volume is less. It seems to me that might indicate something, but I'm not sure.

I mostly use DVD Shrink for ripping, if that makes any difference. I doubt if it does, unless it has an audio ripping bug of some kind(?).

Would a different model standalone Dolby system render the 1-2 channel AC3 movies significantly better? If so, what model would you recommend? (must be fairly inexpensive, under $100)

Sorry for the rambling. It's difficult to compress all of this experience into a semi-logical message.

[tinker]

Poor sound quality from older DVD is just a bad production or may be there was not enough of good quality sound on original movie. I do not think there is anything wrong with your system.
Stereo sound will play only from front speakers, not from rear once, that is normal. Just play any CD from your DVD player and you will get same thing.
Sometime woofer may come alive if there is enough base in the recording, but not all the time.

[guns1inger]

If your amplifier has Dolby Pro-Logic two then you will get better rear speaker work from some stereo sources, but anything that is pre-Pro Logic (mid 70's) is likely to be front or even centre only.