Here's a question. Does anyone have plots for HD15? Also, and perhaps more interestingly, does anyone have an impedance measurement of an HD15? Does anyone have HD15 lying around and fancies doing this? It would be super-cool to get 1, 2, 4 and 8 unit stacks in half-space. 1, 2 or 4 in quarter-space would be roughly the same as 2, 4 or 8 in half-space respectively.
I plan to build a model of HD15 so I can co-design the SD15 and take into account xover and high-pass - for seamless integration and max efficiency!
Same fromt panel dimensions so it stacks nicely, but might go back a little further (which would make the stack less likely totopple over!)
Adam, you need to feed sinewaves into the sub through a resistor. Measure voltage and current at lotsa different frequencies. Impedance is voltage divided by current. Let's leave it for a while in case someone already has this info, that would save your effort. Thanks for offering though!
"im sure this would be hard, but maybe design it so the when SD and HD
are time aligned when the fronts/backs are flush to each other. Im sure
this would be a Nightmare. Just a Thought" correct me if im wrong but wouldn't the only way to do that to have the horn path the same length? in which case that wouldn't work even vuagley, im thinking this will need a long horn path and a nice slow expansion rate?
Well, SD15 will be a bandpass, either 6th order or 8th order depending on what comes out best. This means it'll have a much larger group delay than the HD15, and so to get phase alignment the HD15s will have to be delayed.
One way of doing it is to just have a crossover at something like 70-80Hz, but another possibility is to let the HD15s run down to 0Hz (or the infra filter) and overlap the sub up to 70 or 80Hz. If we do this, we can use the shallow (12dB/octave) rolloff of the HD15 by running the sub in phase to get coupling (probably needs diagrams to explain this properly).