Saturday, February 5, 2011

The perfect Tact impulse

Well, there it is, I connected one channel Tact output to it's very own input through a Harrison Labs 3dB attenuator.  Inside the attenuator is a 2k or thereabouts resistor, which actually causes more like 60dB attenuation into the microphone input load.  (Perhaps that explains why previous numbers were in something like the -60dB range.)

Notice that the pulse is positive only.  And notice that the pulse has leading and trailing ringing caused by digital processing.  If the speaker had perfect response, it would have identical leading and trailing ringing in it's Tact measurement also.

The leading edge ring relative amplitude looks like about 5% and the trailing edge about 10%.  That is considerable.  If the speaker lacks those (as, say, the Acoustat by itself might) that actually means it rolling off the highs.  If the supertweeter adds them back in, it is not adding ringing so much as restoring the ringing "in the signal" (though it's really in both the signal and the measurement thereof through limited digital means).

It's possible the ringing is at precisely the kinds of high frequencies the supertweeter is supposed to be adding too.  Actually, I can test that precisely, by measuring the supertweeter line signal...

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