6th order BP kick section

I have had some problems in the past with Doppler effect in a design similar to this

I don't say you shouldn't try, just make sure the speed of air in the ports is as low as possible so there won't be a lot of air moving along with the mid and HF, atrough I am still not shure that this is the corect way to cure the problem after some recent tests.

This can also be observed when running stupid amounths of sub right next to midtops

above a certan limit everything starts to sound muddy when you unmute the sub section.



Edited by Mircea Bartic - 11 January 2011 at 9:40pm

It's not the group delay as it only displays how long it takes till the signal will be coming out of the system. It can be compensated by delay as long as the group delay over frequency diagram won't be a wild ride around the crossover frequency. It is the decay time of the resonator. A resonator is a very high Q system, that means energy will be stored in and then put out of the resonator, and this won't happen in an instant, especially the "puting the energy out" will take some time AFTER the original signal stopped and even AFTER group delay time has passed. What a resonator does to the original signal is NEVER a good thing, it's always a degradation. Below 60, 70, 80Hz it is acceptable, but still not great. Above 80Hz it's just ugly compared to real "kick bins".

Most double-12 tops are tuned to 80Hz or below, and crossed over around 120Hz. That's ok in my opinion, still there is coming some "noise" coming from the resonator. Stuffing the port for top usage comes to mind. Ported tops tuned to 100Hz or above are just flawed designs, I wouldn't like to use them at all.

I agree with Mark, the driver should have a Qts around 0,3 and a lowish BL around 23, that makes the response nice and smooth. I think that the 0,2 Qts high-fs drivers that Johan mentions are more for pure horns without a front chamber. They'd make a peaky response in a BPH. I made a pair of 6th order BPH based on L15P200AK, but they were rather aimed at low extention.

As to 'real kick bins': they're all 4th order band pass horns, Turbo TMS, F1, HD15, so if you like that sound, go for it. They all have front chambers, otherways they wouldn't play that low. A straight 15" horn without a front chamber kicks like madness (think Martin MK1) and I can understand that people find that sound way better than a BPH, but then the only thing that makes it play lowish (70 Hz) is horn length.