Why is the DVD lounder than the Blu-Ray?

[Blu-21]

I only have a HTIAB Pioneer HTP-522 set up which I've had for a few years now and is more than serviceable given my budget and living arrangements, but today I did a comparsen of The Expendables 2 on DVD and Blu-Ray (both included in the Blu-Ray steelbook), and for some unknown reason the DVD sounder 'louder' and 'fuller' despite the DVD being compressed Dolby Digital 5.1, and the Blu-Ray being uncompressed DTS-HD Master Audio 7.1. Both were set to the same volume in the comparsen.

I'm wondering why this is? because in general, the vast majority of the time, its the uncompressed DTS Blu-Ray which sounds louder and more powerful than the DVD, but in this case it's the other way around which doesn't seem right to me. It's even evident in the menu screen with again the DVD sounding louder.

Is there a reason for this? Does it have something to do with the Neo:X on the Blu-Ray that is not complimenting with my set up thus making the Blu-Ray quieter?