crossover frequency

Laufer · 20th October 2003, 10:57 PM

Hi everyone,

First time posting here. This gentleman crossed a tweeter at 1800 Hz. However, the tweeter's Fs is 1200 Hz. I did know that was possible. Should one not stay at least an octave above Fs. Would someone care to explain this a little more?
I have been wanting to build a central channel with these or similar drivers.

This is the link:
http://member.newsguy.com/~stigerik/html/body_gnurk.htm

Thank you in advance

HobbesJunior · 21st October 2003, 02:27 AM

The closer you get to the fs of the tweeter the more you need a series notch filter (to even out the sharply rising impendence of the unit --- unless you use ferrofluid - or something! - tweeters...

However, the main problem with getting to close to the fs of a unit is that the cut-off rate of the filter is usually just 12/ 24 db/oktave
meaning you still play rather loud below cutoff because the filterslope is too horisontal ... a 6db filter fx would only be -6 db down at 900 Hz if cut-off is 1800 Hz...

At loud levels that would lead heavy distortion and possibly blowing the tweeters after a while, depending on the quality of the unit.

Hobbes

Eric · 22nd October 2003, 06:52 PM

While I am not an expert in this area, there are a few general guidelines that are often followed. I'm sure others will chime in...

In many applications (typical second order XO?), it is recommended that you cross at tweeter at 2-3 times its resonant frequency (Fs). If you use a higher order crossover, you may get away with crossing it at a point that is closer to the resonant frequency, and maybe 3-4 times Fs for a first order crossover.

With woofers, a recommended point is to low pass the driver at a point where the responses at 0 degrees and 30 degrees off axis remain within 3-4dB of one another.

20th October 2003, 10:57 PM	#1
Laufer diyAudio Member Join Date: Sep 2003 Location: Toronto	crossover frequency Hi everyone, First time posting here. This gentleman crossed a tweeter at 1800 Hz. However, the tweeter's Fs is 1200 Hz. I did know that was possible. Should one not stay at least an octave above Fs. Would someone care to explain this a little more? I have been wanting to build a central channel with these or similar drivers. This is the link: http://member.newsguy.com/~stigerik/html/body_gnurk.htm Thank you in advance

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21st October 2003, 02:27 AM	#2
HobbesJunior diyAudio Member Join Date: Oct 2003 Location: Copenhagen	The closer you get to the fs of the tweeter the more you need a series notch filter (to even out the sharply rising impendence of the unit --- unless you use ferrofluid - or something! - tweeters... However, the main problem with getting to close to the fs of a unit is that the cut-off rate of the filter is usually just 12/ 24 db/oktave meaning you still play rather loud below cutoff because the filterslope is too horisontal ... a 6db filter fx would only be -6 db down at 900 Hz if cut-off is 1800 Hz... At loud levels that would lead heavy distortion and possibly blowing the tweeters after a while, depending on the quality of the unit. Hobbes

22nd October 2003, 06:52 PM	#3
Eric diyAudio Member Join Date: Nov 2000 Location: Central PA, USA	While I am not an expert in this area, there are a few general guidelines that are often followed. I'm sure others will chime in... In many applications (typical second order XO?), it is recommended that you cross at tweeter at 2-3 times its resonant frequency (Fs). If you use a higher order crossover, you may get away with crossing it at a point that is closer to the resonant frequency, and maybe 3-4 times Fs for a first order crossover. With woofers, a recommended point is to low pass the driver at a point where the responses at 0 degrees and 30 degrees off axis remain within 3-4dB of one another.