Geoff Hill's Tetrahedral Test System?

[siavashr]

Does anyone have any experience with Geoff Hill's Tetrahedral Test System?
Taking reliable and repeatable measurements of drivers (especially at low frequency) has always been a challenge.
This Tetrahedral Test System promises to solve those issue without having to go to an anechoic chamber.
Has anyone here made their own? They seem relatively easy to make.

 

[simon7000]

It works. Soon to be an AES reference design. Not as simple to build as it seems. Also a bit tricky as to combining measurements.

 

[siavashr]

I just finished reading their white paper. It looks like TTC does a great job for low frequency measurement, but not so good for high frequencies.

 

[simon7000]

I just finished reading their white paper. It looks like TTC does a great job for low frequency measurement, but not so good for high frequencies.

You use different techniques for low frequency and high frequency then you combine the two curves.

High frequencies are actually easier to measure.

 

[planet10]

Reading the white paper:

Loudspeaker on an IEC Baffle as a ground plane

Since the baffle is mounted flush to the ground it is no longer an IEC baffle. The baffle is as big as the ground plane.

This leads to some questionable statements further on.

The rest is interesting.

dave

 

[siavashr]

The thing is, I'm more interested in harmonic distortion measurements than frequency response. Currently, I'm using Steps from Arta software. The issue is with steps you can't do gated measurements, so room reflections affect the measurement. If I place the mic near field (to minimize effect of the room), I'm afraid the SPL level is too high for the mic to handle and the distortion introduced by the mic corrupts my measurements.
At this point the solution seems to be to find a mic that can handle 110 ~ 120dB level without distorting.