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In Reply to: RE: No, it's audible. posted by Coner on December 13, 2016 at 09:25:14
Small correction, but your point still stands.
The 30k crossover point is the -3db point so 15k would be at -9db and 7.5k would be at -15db
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Follow Ups:
No, the turnover is still in transition at the -3db (cutoff) point. It will be -6.02db at 7.5k.
The example was a .67uf cap in series with a 8 ohm tweeter. A first order filter.The crossover point for a BW filter is the -3dB point and for a LR it is the -6dB point.
All first order filters are BW filters.
A .67uf cap in series with a 8 ohm tweeter will cause the -3db point to be 29,693 Hz.
From that -3db point on, the signal will fall an additional 6db per octave.
One octave below the crossover point will be at -9db
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/15/16
No, it isnt. At the 3db point, the slope is still transitioning. its still on the knee of the curve.
"At the 3db point, the slope is still transitioning. its still on the knee of the curve. "OK, did I say it wasn't?
My point is that the stated crossover frequency is the 3db down point when using a 1st order filter.
Do you dispute that?
"No, the turnover is still in transition at the -3db (cutoff) point. It will be -6.02db at 7.5k."
How do you figure that?
The 3db down point of his filter is at 30kHz. At 15kHz if will be nearly 6db further down and at 7.5kHz another 6db below that.
I feel like we are having some trouble communicating with each other.
Maybe it's me, maybe it's you. :-)
Sorry, I know we were talking about a high pass filter and this chart is of a low pass filter but it's the first one I found. It still show what needs to be seen.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 12/17/16
7.5k was in error. it would be -6db at one octave below the cutoff. It seems that you are saying it would be -9db at one octave below cutoff, but it is -6.
Yes, you are right.
I see that now.
My apologies.
The filter is still on the knee, as you said, for the first octave after the 3db down point. The filter only reaches the 6db per octave rate of fall after that. Actually the filter takes a little longer than that to reach the 6db per octave fall rate.
I guess that means my tweeters are playing harder at the lower frequencies than I thought.
Thanks for the correction.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
No need for apologies. Learning is what this is all about. Sharing knowledge which would be much harder before the internet. I have learned some things from you over the years.
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