how do you measure acoustic performance of planar?

Hi, I am not experienced with loudspeaker measurement.
I have done some of my boxed speaker following the guide for REW prepared by the author of Vituix cad.
The measurements i took from the Magnepan are full of peaks and null for relatively close measurements. I used gating, and i think i did it right.

The only measurement that seems to make sense is from 8 feets, non gated.
But I know this includes too much of the room, non-quasi-anecoic.

How do you measure, and what are you looking for in the measurement?

REW has gating in proportion to freq, I believe. I think some amount of room reverb is fairly added to FR.

1/12 curve smoothing is a good Goldilocks setting and popular at this forum.

For most R&D purposes, I leave the mic near my chair and adjust with that constant.

For final FR picture, REW lets you average a few runs (but not average the distortion which I think is real important too). So I use 3 mic locations around where my head would be and average them.

Important to spend a few dollars for a floor-standing mic stand with boom.



2009-10-19 7:47 pm
One meter and near field measurements and corrections work with smaller speakers because they behave more like a point source, but those assumptions are incorrect for more directional speakers, ones with large driver spacing, or dipoles.

For any line source, planar, or other large speaker, you typically need to get back about 2 meters or at the intended listening distance to get more reasonable results. Stereophile talks about this in many of their measurement discussions for larger speakers.

If you gate out reflections, this typically means you won't be able to measure very low in frequency in a typical home environment.

Outdoor measurement is often used to try to improve low frequency resolution.

Or you can just go where you wound up and measure the room contribution too. Since it's where you are going to be listening, it's not a bad solution. I tend to do both, depending on what I'm working on. Ultimately, the response with room drives some of the decisions, especially when it comes to bass/midbass level vs. midrange and up.

When I'm working on midrange/treble issues or crossovers, I rely more on quasi-anechoic measurements.
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2009-10-19 7:47 pm
In case you haven't tripped over other discussions of this topic, the older Magnepan tweeters used aluminum wire. You can't match its mass and resistance simultaneously with copper.

Copper in a tweeter section normally causes high frequency roll-off due to increased moving mass when resistance is matched.

As bentoronto suggested, some smoothing is normally applied to measurements. High resolution scans without it tend to have a ragged appearance. A shorter time window will do some of this for you.