At the moment i have got surround sound from tv through my old hifi system of 10 years old.Will i notice any difference with a modern dedicated home theatre system.

Infinitely – although that depends very much on your intended set-up.

Blu-ray, HD sound amp/receiver, 7.1 dedicated speaker set-up giving you the best, or somewhere inbetween what you have now and that.

At the moment it,s a surround system through a technics sterio system. It has 5 speakers, but is 10 years old now.
To be honest i always struggle to hear the speech clearly in films.

What’s your budget (please tell me it’s around a grand)?

£300-500 will get you something (all in one) that will sound better than your system. £600-750 will get you a half decent system. £800-1000+ will get you a very nice Blu-ray/Amp/Speaker system

I upgraded from a 10 year old Yamaha amp to, er, a new Yamaha amp, largely because I needed a HDMI switcher. The difference really is startling (more so than the visuals) and I always thought the old Dolby Digital kicked bottom. Exponentially less interconnect spaghetti too.

Without a Blu-ray or comparable source though, there’s probably little difference.

To be honest i always struggle to hear the speech clearly in films.

Maybe your centre speaker is duff, and you’ve that channel turned-down.

Sorry, I meant to reply to that, too. It’s probably a setting.

When Dolby Digital came in, it was preferable to have the same / similar speakers for all five of your main 5.1. If your system predates that, it might be your amp is assuming they’re all the same when they aren’t.

Assuming you’re not sending a 5.1 signal through four speakers, of course. That’d do it.

I have the two larger speakers, left and right corners of room, either side of tv. Centre speaker, in front, underneath tv on cabinet. Then two rear speakers in the back corners of room.
The centre speaker and the two rear ones are the same size, but are smaller than the front two corner speakers.

You may need to reduce the amount of bass going to them (“large” vs “small” in Yamaha parlance) and increase the volume on them. Perhaps.

Got a full Sony set up in mint condition for sale