Planar Speaker Asylum

RE: How to measure Magneplanars

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This Post Has Been Edited by the Author

In Reply to: RE: How to measure Magneplanars posted by SteveJewels on March 24, 2021 at 03:20:05

A quick, cheap and easier way to get started with REW is to use a USB mic (like the miniDSP UMIK-1 (limited to 48kHz) or the new UMIK-2 (44.1 to 192kHz and lower noise floor) that come with a factory calibration file (not necessarily the most accurate calibration).

Be advised that using a USB mic and USB DAC has the downside of having 2 different clocks which are not in sync. The next best thing is to use a single soundcard for both the mic and the DAC so the clocks are in sync. The downside is it costs more is more complex. You can also Master/slave clock both devices if they provide such features, but again, it adds more complexity and expense.

Since you said you do NOT have a PC source in your signal chain, you will have to follow a different procedure than many here. You will have to use REW to create some sweep wav files with timing chirps and then burn the REW generated wav files to a CD so you can play them on your CD player. The sweeps need to be of the same sample rate as your intended measurement sample rates (e.g. limited to 48kHz for the UMIK-1 so you would need a DVD player). It also requires the reference timing channel to be able to play high frequencies so if you are going to measure a sub by itself on the left channel, the timing chip should be on the right channel that is capable of a HF output.

This allows you to measure a playback system without physically being attached to it.

If you intend to measure each driver independently, you will have to protect each driver and only send it a signal within its usable range. This can be done in a variety of ways depending on how you are measuring.

If you measure with a higher sample rate, you will get a better HF measurement if your mic and playback chain is capable of handing the higher sample rates.

You can get a calibrated mic from Cross-Spectrum Labs or they will calibrate your mic if you already have one. They will generate files readable by REW. Note, they are slow. My experience has been that mics are off the most at low and high frequencies.

As for XO's. That is another issue. You need to level set your drivers first because the XO point changes as the magnitude of the individual drivers change.

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