Fair points.
The sub is a PSB Subseries 200, NAD powered. You would think it should work properly out of the box as it did with the Yamaha streamer I used previously. I am aware of the reported issue of the sub output being low and subsequently fixed, but I don't believe that's the issue.
I opened up a ticket with Lenbrook where the low sub output has been reported widely. In their response, its apparent its a design thing.
"When your volume is set to 50%, 10% voltage is sent to the main speakers as well as the subwoofer output. If the sub output is not strong enough at your preferred listening level, you will need to use your Dirac Filter or use the 12v trigger to the SVS sub.
As an alternative, you will get more voltage from the M10 preouts as these will output 3.2V max. You will need to disable the subwoofer output and use the line input on your subwoofer as the output will be full range."
Max sub output is 2V (1.969Vrms), you can see the issue. I don't have an SVS sub as it happens, and they couldn't tell me how much signal was required to wake the PSB sub. it's going to be worse if you have two subs as the output then drops to 1.2V.
Its the same service desk for PSB, Bluesound and NAD as it happens so when you open a ticket (I opened 3, one for the M10, one to Bluesound, one to PSB), it ends up in the same ticketing system and indeed, was attended by the one agent. I was not at all impressed with the interaction with Lenbrook support, they seemed confused and closed the ticket continuously despite not having answered the question. I certainly expected much better.
As you know the sub out when used also drops low frequencies to the main speaker, so using the suggested workaround defeats the purpose. It didn't work anyway.
I digress.
Can you advise where I might find your review.