As per the instructions, I started with measuring around 1inch from my Rythmic subwoofer cone. I am quite alarmed to find that below 80Hz the decay is not as you have described. At 300ms there is still a lot of energy below 80Hz. I am mystified by this. Any ideas why? I could email screen grabs as well as the REW file.

Keep in mind overlapping only offers a benefit where the mains smooth the bass response of the sub positions. This won’t always be the case. I’ve seen many examples in my consulting work where one or two subs can’t be improved in this regard with overlapping. In fact, often just one or two will reveal the full potential of a particular room. So you should determine if you will actually achieve a benefit as it may not be there.

If you find you DO need overlapping, then I’d set the mains to large and use MiniDSP to create a high pass for the mains.

It’s great that three years later this 3 part tutorial still remains one of the best I’ve seen. Thank you for the comprehensive guide. One thing I would point out is that I had to read to part 3 before I realized that the overlapping mains and subs approach won’t work with even a sophisticated AVR alone. Most AVRs I know of only allow for a single cross-over point. While you can always boost the bass level, it will only boost the signal routed from the mains to the subs below the cross over frequency. That’s a bummer for me since I recently bought a Denon AVR x3000 that won’t let me implement this scheme. I wonder if it still might be possible with the introduction of say a miniDSP 2×4. Any thoughts on that?