His approach (at least as initially described) largely ignores the last decade (couple of decades?) of improvement in DSP, which allows us to not just even out frequencies by adding subwoofers, but also by actively employing EQ, which changes the game a bit. Also, as most other things, it's a matter of compromise. The benefit of highpassing the speakers (in addition to smoother integration in many cases) is significant increase in capacity in the midrange, since the speaker now aren't forced to play deep bass, they can play louder without the woofers bottoming out. The result is lower distortion and cleaner playback. In a 2-way system this is also the same driver that plays all the way up into the midrange. Good and even bass is important, but midbass is also important, and often neglected.
Definitely. His work dates back decades, and the diyaudio.com thread dates from 2008, so you see significant evolution/changes in his approach. Rather than looking for a cookbook, I learned from the back and forth, weighing the ideas, supporting scientific explanations, etc.
And yes, high-passing small mains would be required to fully benefit from the increased dynamic capabilities of adding multiple subs. He uses 15" pro woofers, previously vented, now sealed, and we know that pro woofers in
relatively small sealed enclosures will lead to a fairly high F3.
My mains have a vented 12" woofer (I have thought a lot about plugging the port if only to see the effects of the lower slope/different phase characteristics, but haven't experimented with it yet). With four subs, I have a low shelf to bring the bass into balance. Combined with parametric eq at my stubborn 35Hz and 78Hz nodes, the mains' woofers are receiving less signal. Last night I played music at a very high level and they moved much less than I was expecting.
"Good and even bass is important, but midbass is also important, and often neglected."
I think so too. I have found that getting < 100hz is fairly straightforward. It is 100-200hz that is the struggle. I have been in a (probably ridiculous, or maybe just insane, per my family, as they listen to seemingly endless signal sweeps) experimental phase with mains placement and sub adjustment over the last week. Thankfully after last night I am back to "leave it alone and listen to music, dummy."
I am nervous about showing images of how it went, but I am pleased with my 100-200hz results, so will show them and they are perhaps illustrative.....please ignore if too much! Or maybe pictures are worth a thousand words? Above 300 hz there are SBIR effects and multiples of room modes. I have convinced my wife to do some radical acoustics work (after I finish the back porch project....), mainly the ceiling and rear wall (currently just treating first reflection points), so this will get better. Right now I am just using PEQs in my RME DAC to fine tune. First two subs are under the mains, fed L/R signals, other two subs fed mono. All 1/48 octave smoothing, 50db scale with target room curve I was shooting for:
Mains:
Add sub under left main (blue):
Add sub under right main (orange):
Clearly, because they are co-located with the mains, their effect on modes isn't huge, though there is some "moving around" and a bit of filling in the nulls.
Add Left rear sub (green):
Add fourth sub, R rear. Fascinatingly, the response was good, but there was one deep null at around 120hz remaining. I thought hmmm...let me try moving it a bit. After 3 or 4 moves I ended up with this (pinkish?):
Mains only and mains with 4 subs, no EQ:
After a bass shelf starting at approx. 85hz (relieving the mains to some degree as described above and 2 bands of parametric EQ in the RME (35 and 78Hz):
Sounds pretty good to me at this point. You will notice I don't have huge extension (subs are sealed 10" JBL studio units), but there is good dynamics and "power." I did have a bit of a learning curve to be able to do this in fairly short order, and I am NOT suggesting the OP (or anyone, really) takes this route. It is only for illustrative purposes. With his proposed equipment he will have an easier go of it with their built-in capabilities. I don't know how I could have smoothed > 100hz without higher crossovers.
Now I am praying that when I hit "reply" my formatting will stay and this won't look like a jumbled mess......
Bill