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In Reply to: RE: Tweeter Alignment Results posted by unclestu on August 09, 2014 at 15:17:52
Wouldn't drivers being partially out of phase with one another do to lack of physical alignment cause frequency response abortions?
Might not be the final word but I would say it's some indication.
Of course I would want to see the FR/phase curves for each driver to help shed a little light on what the overall FR curve is telling us.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
If you need a test signal to check your alignment, I put one on my web site. You can use any electret mic to pick up the acoustic wave and a scope to display the result.
The OPs post makes perfect sense taken in context with his previous thread. If you haven't read that, not so much.
Thanks Bill I hadn't realized that until you pointed it out...
Anyway it looks like I may need to attenuate the tweeter or bump up the mid driver to get a better balance. I can attenuate the mid driver from my xover so not a big deal...
What was the difference soundwise?
Are you kidding??? Did you look at the two graphs??? There was a huge difference in sound quality, everything got cleared up. The soundstage opened up quite a bit and the highs are much more pronounced..
Jajaja, you dont have to convince me! Just trying to make a point.
I know how drastic the difference is...
Now, after measuring, doing all the graphs and listening experience, knowing roughly the right position: would you be able to time align by ear next time?
Maybe I am not sure, I would rather be exact and I like measureing electrically makes me feel better.
Hi
Measuring is the best way to arrive at the optimal result.
If you can, get a copy of ARTA or other low cost measuring software and a half decent measurement microphone.Fwiw, impulse response and step response are actually poor ways to judge this, the acoustic phase (phase once the fixed time delay has been accounted for) is the best view as it shows the relationship to the input signal or between the upper and lower frequency range.
The impulse and step response emphasizes the HF response portion and makes the LF hard to see.
Best,
Tom Danley
Danley Sound Labs
Edits: 08/12/14
Let me clear the air some, yes I am using a different tweeter that's why the huge difference in the two plots. As for alignment I used RTA with the polarity fliped on the tweeter to create a null or peak at the xover point while playing that frequency with a generator. Hope that explains it better.
Hi
The problem with not including time (which an RTA does not) is that one will get a null (with polarity flipped) every 360 degrees of phase rotation. In other words, the measurement will have a null if you are in the correct time but also every wavelength (360 degrees of phase error) as the sources are 1,2,3 etc wavelengths either ahead or behind in time as well.
Since some music is very “time variant” and not a continuous signal, one can have what appears to be a correct alignment with an RTA but in reality be off by one or more wavelengths with one source being far ahead or behind in time.
Best,
Tom
Thanks Tom I plan on remeasuring this weekend using impulse with a time reference.
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