chaudio wrote: Not quite answers to your questions but a few things I mentioned at the meet you might want to look at....
The horn I mentioned, definitely worth a look: www.eighteensound.com/index.aspx ... ct&pid=269
Looks fairly similar to the TI2000 horns I'm using. They're CD, I think. There's a lot of vertical spread below 1K in the plots, which probably means some unloading of the driver.
chaudio wrote: Although your compression drivers will work down to 500Hz, unless you go for a very large horn they won't properly support that frequency. I think you should be aiming for a crossover point more like 800Hz. The 18Sound XT1464 will probably go a bit lower than that, as will the larger EV horns but you're trying to keep the cab smaller.
Yes, I'm very concerned about unloading the comps. But in the spirit of compromise, I think I'll be OK. Consider that the BMS mid has a 0.8mm excursion, made possible by the fact it does not have to play above 6K. Also, this being a small system, I don't expect to run it at full power. The provisional TY designs add a 1-2 inch baffle all the way around the horn. All things considered, I hope to get away with something like 650-700Hz.
chaudio wrote: I think it's worth looking more at the D&B Q Series boxes. They use two 10" drivers and manage to run them up to 1.3kHz.
I'd be interested in seeing plans - though the Q tops do sound a little thin IMO (not hugely). I guess they had to make compromises too.
chaudio wrote: I'm assuming you're going to be looking at some slightly meatier low mid drivers, the D&B boxes are B&C neo loaded. I think it might be worth looking at the PD 10MH25 as a fairly cost effective high performance driver. For a higher end driver, the 18Sound 10NMB420 looks good.
PD 10MH25: Mms 37g, EBP 360Hz
10NMB420: Mms 31.5g, EBP 200Hz
Delta 10: Mms 32g, EBP 200Hz
So the 10NMB420 has similar specs to the Delta 10s (but probably handles more power). The PD is a different proposition - I just ran a quick model of my proposed design and I think its higher mass may be problematic.
chaudio wrote: While I'm impressed at the grasp you have on the design of bandpass enclosures I personally find that they never seem to integrate into a system nicely, especially at higher frequencies.
Then you won't like what I plan to do for the midbass in the TY :shock: Yup, that's right... I'm looking at a midrange bandpass, running (hopefully) from 140Hz to 650Hz at about 106dB sensitivity. That's not quite horn levels, but the TY will be much smaller.
Usually with bandpass cabs, the driver's EBP is an effective upper limit on frequency range. That's because in a bandpass, the varying gain of the resonators must be counterbalanced perfectly by the loading on the driver. This only works when the driver presents an essentially resistive source impedance. Above EBP, the driver's mass gets in the way - at some frequencies it reacts with the cab to give a boost and at others it adds to give a cut. It's hard to "tweak" these ripples away.
But I've got to thinking that the phase plugs we see in mid horn throats might be doing some "magic" that appears to reduce the Mms, giving control up to maybe 1 or 2 octaves higher. This is why so many practical horns seem to out-perform the predictions of standard formulas. If I can harness this effect, I can build a bandpass with the above specs.
So I think I'm looking at driver with phase plug, set up to act as the A chamber. If it can "magically" cut Mms from 30g to say 15g, then it can work as a bandpass A chamber, (2.5l tuned to 500Hz). Then I cascade that into a C chamber (7l, 260Hz) and now I have flattish 105dB response from 650 down to 220. Finally, I port the rear (B port, 10l, 100Hz) to lift the bottom end a bit, getting to 150Hz cutoff. I can fit two of these into a 40l box which is only a little bigger than the current TX. I can reproduce similar results in Hornresp and my own software, as long as I bodge the Mms down by half.
I know using a bandpass for midrange will be distasteful to many, but I bet you're curious to know what it sounds like. As am I.