No expert here, but normally, a ported box has to be measured twice, once near field (and I mean near field, like 0.01m, not 1m) to capture actual driver response, and once in the port, then merged. Otherwise the room plays too large a part. Alternatively, assuming port and driver face the same way, ground plane measurements will give you an anechoic response.
Next is to set expectations - tuned boxes aren't that sensitive to perturbations around a good center point. I did a sensitivity analysis some time ago, looking at the affect on tuning frequency of several perturbations. Box size and port size are strong drivers, port length and port end correction, not so much. 50% change in port length should be barely audible, even if it's quite measureable.
If you want large changes, play with the XO components that adjust driver level, padding resistors, L-pad, whatever's used to match driver levels. I can easily hear changes in tonal balance. I can also easily hear a tweeter that's crossed too low - high harmonic distortion.
Part of your listening lab projects should be calibration of the listener. All people are not equally sensitive to all aspects of sound reproduction. I'm sensitive to HD and tonal balance; you may notice timbre I don't. We're all different, and Harman has a great resource in this regard.
Have fun,
Frank
Next is to set expectations - tuned boxes aren't that sensitive to perturbations around a good center point. I did a sensitivity analysis some time ago, looking at the affect on tuning frequency of several perturbations. Box size and port size are strong drivers, port length and port end correction, not so much. 50% change in port length should be barely audible, even if it's quite measureable.
If you want large changes, play with the XO components that adjust driver level, padding resistors, L-pad, whatever's used to match driver levels. I can easily hear changes in tonal balance. I can also easily hear a tweeter that's crossed too low - high harmonic distortion.
Part of your listening lab projects should be calibration of the listener. All people are not equally sensitive to all aspects of sound reproduction. I'm sensitive to HD and tonal balance; you may notice timbre I don't. We're all different, and Harman has a great resource in this regard.
Have fun,
Frank
