Hi Rodny,
I'm interested in your observations on the port noise. You may or may not know that I've done a fair bit of
work on the subject. The rig I used only allowed me to test ports up to 6 inches, and frequencies down to 20hz.
Your observations would add quite a bit of value to that work if you could do a small test or two.....
Do you think you could repeat the situation that produced the 10 hz chuffing at close range, whilst measuring the voltage across the driver?
From the voltage and the DC resistance of the driver, the input power can be modelled:
Input power = RMS voltage squared / DC resistance of coil
Plugging this power into WinISD allows the velocity at the test frequency to be read off.
If you could let me know this velocity, along with the actual ID of the port, and the flare radius, it would allow me to increase the accuracy of the "
flare-it" software for large ports.
I know SteveC uses this software, as do many others. With the popularity of some of the larger sonosubs, an 8 inch port is sometimes employed, and it would be nice to have a frame of reference that is derived from a large port such as yours.
If you were able to do a second test at 20 or 25hz, this would extend the accuracy even further. (you may not be able to generate enough airflow for the ports to misbehave at these frequencies)
thanks
Collo