Bookshelf Speakers Sitting On Dual Subs?

@normb  👍

Stereophile:

While the 8c is big for a stand-mounted speaker, its cabinet isn’t big enough to develop a lot of bass; Hofmann’s Iron Law has not been repealed ... D&D takes advantage of placing the speakers close to the front wall with what they call Boundary Coupled Bass. When the 8c is positioned from 4" to 20" from the wall, the direct output of the rear drivers is acoustically coupled to the energy reflected by the wall such that they act as a single source ...

So it seems desirable to place D&D close to the front wall. Now the issue you have to cope with is whether which location is optimal for Elac sub. if you want to stack them up ...

What is the end goal you are trying to achieve? Louder over all playback levels, more thump? The 8C’s appear to have a sub out, is it full range or do they have low and high pass filter capabilities? The drivers in the 3070’s appear to be on angled baffles, are you using them in a side firing configuration or a front and back configuration? Are the 3070’s currently in the room now and if yes are you having any issues?

The first potential issue that jumps out to me could be a phase issue. A lot of drivers facing different directions, specially if the 8C’s are run full range. Potentially a lot of different paths for the sound waves from different sources to take on their journey to your listening position could make for some muddy bass.

The another possible issue if the 8C’s are full range is that your subs may not have much to do. According to the 8C’s spec’s they are good down to 30 Hz, not much in recorded music gets that low, not too mention lower.

@sumadoggie 

Can you do it? Sure.  Will you get good sound? Probably not.  Most people set their speakers 3-4 feet from the front wall and have the subs much closer to the wall to avoid getting boomy bass.

All the best.

Scaling back from dedicated room with audiophile rig into a new home with a great room serving multiple uses. The 8c will sit nicely atop the 3070s about a foot from the brick wall in a room which is open to the second floor, the foyer and the kitchen, and rises from about 8’ on one side to about 20’ on the other. The system is going along a rising 8’-20’ wall, firing across a very asymmetric room. This is a compromise system until a dedicated room appears again. DSP in the subs and the 8c will be this room's best friend. The original question was about the stacking aspect of the 8c on the sub really. I believe that D&Ds DSP correction will even take care of the sub’s behavior when the signal is run through the monitors (even though the 3070s have their own optional DSP). The goal is more bottom octave, and fuller dynamics through the space. I have no doubt that the DSP will do its job, my interest was ore concerning the stacking aspect and, honestly, @normb nailed the landing quite succinctly, I’ll bet.