Toast_Master said:
I believe the only parameter you need be concerned with is the tuned resonant frequency which you can adjust by adding or subtracting mass.
You would measure that the same way you would with a port by looking for the 1st impedance peak of the woofer when swept over its operating range.
Re: Re: Passive Radiator measurements?
No, one would measure tuned resonant frequency by looking for minimum point in the saddle made by the two impedance peaks in a ported or PR system.
IMO, when making your own PR, all you need be concerned with are PR area and PR mass. Calculate the volume of air inside a port the same diameter as your PR. Then calculate the mass of that air. If you make your PR that mass, it will be tuned to the correct frequency.
If you want to measure Fp and Vap:
First measure (from a distance of a couple feet) the very low frequency response of the PR and woofer in a test box of volume Vb. Look for a minimum in frequency response. That is Fp, and it can be rather hard to measure. In that same box, measure teh impedance and find the frequency of the minimum in the saddle. Call that Fb.
The Vap of the PR is defined by:
Fb/Fp=sqrt(Vap/Vb+1)
so: Vap=((Fb/Fp)^2-1)*Vb
Qmp can be estimated by the height of the lower peak, by trial and error, entering Qmp values into a good modeling program until the simulated impedance matches the measured. For modeling purposes, just use Qmp=~5
speaker said:
No, one would measure tuned resonant frequency by looking for minimum point in the saddle made by the two impedance peaks in a ported or PR system.
IMO, when making your own PR, all you need be concerned with are PR area and PR mass. Calculate the volume of air inside a port the same diameter as your PR. Then calculate the mass of that air. If you make your PR that mass, it will be tuned to the correct frequency.
If you want to measure Fp and Vap:
First measure (from a distance of a couple feet) the very low frequency response of the PR and woofer in a test box of volume Vb. Look for a minimum in frequency response. That is Fp, and it can be rather hard to measure. In that same box, measure teh impedance and find the frequency of the minimum in the saddle. Call that Fb.
The Vap of the PR is defined by:
Fb/Fp=sqrt(Vap/Vb+1)
so: Vap=((Fb/Fp)^2-1)*Vb
Qmp can be estimated by the height of the lower peak, by trial and error, entering Qmp values into a good modeling program until the simulated impedance matches the measured. For modeling purposes, just use Qmp=~5
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