Existing owners of those models can add the upgrade via a home firmware upgrade for £70.
The Audyssey Dynamic Volume system monitors the volume level of the programme or film being watched millisecond by millisecond, maintaining the desired listening level for all content, while optimising the dynamic range to preserve impact.
Regular adjustments are made as volume levels on different programmes or from different sources can sometimes vary by as much as 10dB. Normally the listener has to adjust the volume manually, but the Audyssey system does it automatically.
As part of the upgrade, Denon AVR-3808 and AVR-4308 users also get Audyssey Dynamic EQ and CEC (Consumer Electronic Control) HDMI protocol support (already installed as standard on the AVC- and AVP-A1HD models).
Th EQ loudness correction technology solves the problem of deteriorating sound quality as volume decreases by taking into account human perception and room acoustics, says Denon.
Full details of the Audyssey upgrade are available on the Denon website.