Edgar= wrote:

N-Set, I invite you to make your own recording of the phase of your Dunnoy. I used my phone camera to do it and a free online sweep generator. I had Tannoy, Scanspeak and laptop screen all in shot when I filmed and shot from as side on as possible. I didn't observe another phase flip like you mention below 20hz. Definitely out of phase from 1hz to 20hz.

Edgar= wrote:

If you do film your Dunnoy you will get insight into the conundrum of integrating more bass. I'll give you an example. For the sake of this argument let's pick a design frequency of say 40hz to crossover. When I watched my footage I observed the phase drift start around 55hz. Im calling from 55hz and up, in-phase and from 55hz down out-of-phase. It's not technically in phase yes, also it not just suddenly out of phase either, and for that matter it doesn't start at 55hz but there is an observable shift around there, both visually and acoustically enough for me to choose that frequency for this argument.So at 40 hz what driver do you want to interface with? That is which driver do you want to time align with? If we choose the tannoy then we will be out of phase with the PR. If we choose the PR we will be out of phase with the Tannoy. As we go lower and the difference of phase between active and passive radiators increases, the issue gets worse. Which ever way you cut it, if you add another driver to your room delivering sub 55hz energy, it will be out of phase with Dunnoy.

N-set wrote:

QRD diffusers on the ceiling