With the advent of modern dsp, measurements and REW, many have achieved bass nirvana with precision tuned subwoofer / mains crossover, time and phase alignment. Myself included.
However, imo there is still something to be said about the old fashioned way of analogue blending of subwoofer to stereo mains using speaker level inputs and the adjustment knobs on the subwoofer plate amp. In fact, REL still advocates this approach and provides a custom cable connector for this hookup method on their subs.
I’m not trying to debate the pros and cons of one approach vs the other. I’m looking for fellow enthusiasts who have tried and successfully implemented the analog blending setup over the years, to share their tips and tricks, and thoughts and observations on this approach.
Besides REL, most subwoofer also offer speaker level line inputs as well. However, there is hardly any documented info on placement guides and successful integrations. I have read and listened to REL’s guide. Makes a lot of sense to me.
On a related note, here’s the Flanking Stereo subwoofer setup methodology as proposed by Wayne Parham, the founder behind Pi Speakers. This can be used to supplement any stereo speakers, run full range with no high pass, and blending the subs via placement, crossover frequency and phase for optimal summation with said mains.
Todd Welti Multisub (Foundation of Harman approach)
Earl Geddes Multisub (basically random placement, advocates using height direction, and doesn’t prioritize time alignment)
Conceptually one can think of traditional multisub and room modal smoothing to focus on the sub 100hz range, while the flanking sub approach helps the 100-200Hz upper bass and lower mid areas.