UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post

Ghostuser · 2nd Oct 2006, 5:38 pm

Hi,
I seem to recall that the mass and area of the driver work like a weighted piston driving the cabinet like a Helmholz resonator. I also seem to remember that the basic trick is to match the natural resonant frequency of the driver to the resonance of the cabinet when coupled to the driver mass and area. The close coupling results in a broadening or even a double-hump splitting of the resonant frequency of the speaker/cabinet combination. Damping material then smooths out the result. So, in the absence of proper mathematics and physics, choose a driver with the same resonant frequency as the Spendor unit and, if possible, the same mass. My guess, from the original BC1 response curves is that the driver had an open air resonant frequency of about 70 Hz, but that is pure speculation.
Nigel

2nd Oct 2006, 5:38 pm	#3
Ghostuser Pentode Join Date: Oct 2003 Location: Alton, Hampshire, UK. Posts: 137	Re: Bass/Midrange Drivers Hi, I seem to recall that the mass and area of the driver work like a weighted piston driving the cabinet like a Helmholz resonator. I also seem to remember that the basic trick is to match the natural resonant frequency of the driver to the resonance of the cabinet when coupled to the driver mass and area. The close coupling results in a broadening or even a double-hump splitting of the resonant frequency of the speaker/cabinet combination. Damping material then smooths out the result. So, in the absence of proper mathematics and physics, choose a driver with the same resonant frequency as the Spendor unit and, if possible, the same mass. My guess, from the original BC1 response curves is that the driver had an open air resonant frequency of about 70 Hz, but that is pure speculation. Nigel