Hello all, looking at the D&B Q series boxes and wondering how they achieve directivity control down to a claimed 400Hz from this configuration? The drivers are roughly facing the ends of the cabinets and this apparently achieves 'dipolar radiation' but I can't see how...
Is each driver assigned it's own amp channel and some sort of processing applied to each or is this really simple and I'm missing something??
Just interested really!
Unless you own and use some of the gear, it's unlikely that anyone will know, apart from theorizing. I would try to get hold of the specs from the web site, they might explain it in detail. D and B, whether you like the gear or not, has always had a strong technical reputation and a reason for doing things.
Thanks for the reply Tony (increasing activity on this sites forum is a good thing!) There is no real technical info even in the user manual but there are drawings of the cabinet with grille removed.. Doesn't look anything special or clever to me so just wanted peoples opinions on how it might work.. Probably DSP knowing D&B!
I think fig 10 is the most important graph: horizontal spread in line array config. We see a reasonably controlled spread over 1K, which is the horn at the centre of the cab. Below 1K it pinches in rapidly, then expands, eventually getting omni at low freqs.
Reading off 400Hz at -6dB, I see 90 degrees total spread, which seems controlled, BUT it is trending at around 50 degrees per octave.
The graph looks like what you would expect from two sources a certain distance apart, which is probably what dipole means, and from the engineering sketch it looks like the two 10s are positioned at each end of the cab. I don't think the ducts are important, probably just a way of making the cab smaller. And I don't think DSP is needed for the directivity graphs shown.
I think they might use DSP to remove the sharp resonant peaks resulting from the ducts (TX design had this problem too). DSP *could* be used to reduce the narrowing seen in the graph by simply fading out one of the drivers, but I guess they found these results good enough. Eventually, compromises must always be made, and D&B's good reputation suggests they are probably making the right compromises.
Nonetheless I would do things differently... of course!