Mysterious Impulse Measurement Problem

[dumptruck]

Here's a 2nd attempt at a loopback test on the Lexicon. I didn't change a freaking thing and now I get this every time (compare to above), which has a flat frequency response. Things seem to be getting less clear by the second. P.S. the little dip is still there when I go back to measure from the mic.

 

[dumptruck]

Same result with loopback in HOLM, there's that trailing teardrop shape, but it's a flat response. I don't know what the heck happened the first time. No, my speaker measurement results have not changed. Is it possible the little downward start to this (and the same above) system impulse is actually the one I'm measuring at the speaker?

 

[Pano]

Thanks for the graph. I'll have to compare to my M-Audio soundcard. I do remember seeing a little dip in ARTA on my measurements.

 

[speaker dave]

Here's the laptop loopback. It's flat....

That is the standard sin x over x ringing of a linear phase filter. Looks perfectly fine.

 

[speaker dave]

Lexicon and ARTA both look like a combo of linear phase and analog. Nothing wrong there. Maybe its just the real impulse response of the woofer that you are seeing.

David

 

[Skywave-Rider]

Here's a 2nd attempt at a loopback test on the Lexicon. I didn't change a freaking thing and now I get this every time (compare to above), which has a flat frequency response. Things seem to be getting less clear by the second. P.S. the little dip is still there when I go back to measure from the mic.

And when you convert that to a FR graph, does it look as it should?

 

[dumptruck]

Maybe its just the real impulse response of the woofer that you are seeing.

Well, I don't know... here are the other two drivers I mentioned. One is a crappy 15" Goldwood, the other is a Weber 10" guitar speaker. The one used in the rest of this thread was a Lambda TD15M.

Skywave, yes, it looks good now, not sure how I got that rising response the first time.

 

[Skywave-Rider]

Have you switched amplifiers? Try that.

BTW, every once in a blue moon I will get a weird (way out) result...when I measure again, it's normal.

 

[dumptruck]

See first post Skywave 😛 Funny you should say that though, because I am about to try a third one. Gotta run some errands first.

 

[speaker dave]

We are overlookinging the impulse response of the microphone. If it starts with a downward swing it would imprint that on everything. Not sure what the significance of it is.

Not really a big deal.

David