About 450,000 extra homes will be able to listen to local digital radio with plans to switch on new transmitters this summer.
Digital Radio UK says coverage will be extended in south Wales later this month and in west Wales from August.
About 150,000 homes in north west Wales will be able to receive BBC Radio Wales and Radio Cymru as well as some commercial stations by 2014.
The announcement was made at a meeting with broadcasters in Cardiff.
Listeners will need a digital radio - sometimes called a DAB radio - to receive the signal.
Steve Austins, editor of BBC Radio Wales, said: "We're always looking to improve the way our listeners are able to receive BBC Radio Wales and BBC Radio Cymru.
"So the news that 65% of the population will be able to hear both stations on DAB next month is a welcome boost."
Other stations broadcasting on the new transmitters include Radio Pembrokeshire, Radio Carmarthenshire, Nation Radio, Real Radio and Smooth.
In March DAB radio was expanded in north east Wales with new transmitters switched on in Wrexham giving over 300,000 people access to local as well as national stations.
Local digital radio in Wales will reach nearly 80% of homes when north west Wales is added in 2014.
More than 85% of homes in Wales are already covered by the BBC's national networks on DAB.
Local government minister Lesley Griffiths also attended the meeting at BBC Hoddinott Hall on Wednesday.