That's exactly how a Bit Perfect filter should look like on an FR curve, so nothing wrong there. If you need an explanation, I'll suggest you start researching the topic of NOS (Non-OverSampling), which is what Bit Perfect filter is. Here is how all three filter settings look like: p/s: FYI, the bass roll-off on DX50 is caused by output capacitors. p/s 2: forgot to mention the above FR curve is for 16/44.1 (and 48) only. Upsampling will result in a different looking curve.
4/17/15 at 9:13am