Phase Plugs & Near-field Measurement Techniques

[Loren42]

When measuring transducer near-field you typically place the mic very close to the dust cap.

Where does one place the mic when you have a long phase plug?

My guess would be parallel to and close to the phase plug base near the voice coil, but would their be any bad interactions between the cone and the vent created by the voice coil's gap about the pole piece?

[dantheman]

Since no one is chiming in here, I'd say just back the mic off a few inches but keep it in the center. See what the results look like and post'em.

Dan

[Loren42]

Originally Posted by dantheman

Since no one is chiming in here, I'd say just back the mic off a few inches but keep it in the center. See what the results look like and post'em.

Dan

I get too much crosstalk from the twin ports that are right next to the woofer. The phase plug is really long and almost comes even with the edge of the basket.

I put the mic next to the plug about 1/4" from the cone wall and got this for my AE TD15H in a 6.5 cubic foot enclosure tuned to 29.5 Hz:



Just as predicted by LEAP5 i get this port resonance at 500 Hz.

[dantheman]

Check this out:
mh-audio.nl - Acoustic

Dan