For what its worth, here are some tricks I learned living with a Velodyne DD18:
-do as much of the setup in the analog domain as possible. Move the sub, adjust position, height etc before doing anything digital / EQ. In my ears, the less EQ the better.
- if you have a big heavy sub, consider a low trolley or similar. Positioning is not just a one-time issue. You may want to vary the sub position between "good" closer to a wall, and "optimal" more into the room, with different components in the system, room tweaks, etc.
- give it a sandbag on top (big improvement), better feet like Cerapucs (some improvement), plus a better power cable and interconnect (some).
- I have done a bit of room tuning including two Daad3 bass traps (that don't really catch much low bass, but help a bit in the 100hz or so region), but I don't believe in overinvestment at this point. It is very room-dependent. I have a fairly large 20 x 27 feet room.
-timing - better subs, materials etc may be a solution, but for now, move the sub closer to the listening position (DD18 is forward-firing). Often not so practical, but it can work.
-in some contexts the sub sounds better with the EQ and the crossover defeated. I was ridiculed for this viewpoint, in another thread, but sometimes it works, to get the best blend of sub and big speakers. The trick is to turn the sub volume REALLY LOW (like 4 of 30 steps at the DD18), so there is just a touch of deep bass. After awhile you'll notice that no more volume is needed.
- listen for the music not the bass as such. With optimal tweaking positioning you will hear more depth, more juicy treble instruments also, like flute in front of the speakers, bells sounding in the room, and similar.
- the speakers and sub should "grip" the room. Or make the room play along. I can hear this, for example, listening from a nearby room. I make better salads in our kitchen if the system plays well in the living room... But as noted above, this is a balancing act, hard to achieve perfectly.
- shifting phase 90 degrees can help cure standing modes (or a sub array).
- run the speakers full range, if they were designed for it. The sub is an add-on into the lowest frequencies. I have never had success cutting the bass to the main speakers. Even most monitors I have tried sounded best getting the full signal.
It is good to see that there are many ways to reach the same goal. I tried several subs ten years ago, before settling on the DD18. Mostly, they were too slow, lazy, or what one might call it (B&W ASW 800, REL Stratas) but I also remember a funny little over-active Sunfire that wheezed and danced on the floor when pushed. I had the Krell FPB600 / Dynaudio Consequence mk2 for ten years, and with this combo, I often liked the EQ and crossover defeat ("stealth"?) method. With my current Atma-sphere MA1s / Audiokinesis Dream Makers combo, however, it sounds best with a conventional setup, crossover at 44hz, a little EQ and 90 degrees phase. I can hear it, and it appears when I measure (using Rode mics and the REW program) also.
My problem, now, is that my new preamp (Einstein The Tube mk2) only has one set of volume-controlled outputs, going to the speakers, so if I want sub integration, I will have to use speaker level connections (or use the line out outputs on the preamp, and then adjust sub volume manually each time I adjust preamp volume - not realistic). In my experience this means worse sound (except for the REL subs, that were built for it) compared to preamp level connections. I have not tested yet, and the reason is that the new preamp sounds great and makes the whole system more muscular not least in the bass. So I am seriously thinking that perhaps the sub goes out the door. Yet I sometimes thought so, with the Krell/Dynaudio combo also, supposed to be bass leaders. So I guess the sub stays. Even if I don't use it for now, testing with / without sub is a luxury problem, compared to missing something and then pay a lot to try. And I still remember that great first impression late evening, with the DD18 in place: "hello, bass player".
