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Author Topic: Comb Filter Questions  (Read 3221 times)

Jeff Bankston

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Comb Filter Questions
« on: October 04, 2021, 04:22:14 AM »

Can someone post comb filtering images of these side by side horn configs to show comb filtering ? Crossover point is 1500 HZ 24DB LR active. Horns are not splayed. All horns are the same model. ^ ← horn symbol. Thank you.

 40404040    4 - 40 deg horns side by side butted against each other.
   ^^^^ 

 60606060    4 - 60 deg horns side by side butted against each other.
   ^^^^

 60404060    4 - 60 40 40 60 deg horns side by side butted against each other.
   ^^^^

 40604060    4 - 40 60 40 60 deg horns side by side butted against each other.
   ^^^^




« Last Edit: October 04, 2021, 05:30:27 AM by Jeff Bankston »
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Dave Pluke

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Re: Comb Filter Questions
« Reply #1 on: October 04, 2021, 03:12:48 PM »

Can someone post comb filtering images of these side by side horn configs to show comb filtering ? Crossover point is 1500 HZ 24DB LR active. Horns are not splayed. All horns are the same model. ^ ← horn symbol.

Pretty simple CAD task to draw adjacent triangles to get a rudimentary idea of where comb filtering will occur. But, it would be helpful to know the center-to-center distance between drivers and the model of waveguides/horns in question, as advertised dispersion angles are only at certain frequencies.

Dave
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Caleb Dueck

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Re: Comb Filter Questions
« Reply #2 on: October 04, 2021, 03:31:58 PM »

Can someone post comb filtering images of these side by side horn configs to show comb filtering ? Crossover point is 1500 HZ 24DB LR active. Horns are not splayed. All horns are the same model. ^ ← horn symbol. Thank you.

 40404040    4 - 40 deg horns side by side butted against each other.
   ^^^^ 

 60606060    4 - 60 deg horns side by side butted against each other.
   ^^^^

 60404060    4 - 60 40 40 60 deg horns side by side butted against each other.
   ^^^^

 40604060    4 - 40 60 40 60 deg horns side by side butted against each other.
   ^^^^

Do you have EASE Focus?  It's free and can do this. 
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Jeff Bankston

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Re: Comb Filter Questions
« Reply #3 on: October 04, 2021, 03:36:06 PM »

Do you have EASE Focus?  It's free and can do this.
No I dont and I'm still using Windows XP.
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Ivan Beaver

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Re: Comb Filter Questions
« Reply #4 on: October 04, 2021, 03:36:22 PM »

Can someone post comb filtering images of these side by side horn configs to show comb filtering ? Crossover point is 1500 HZ 24DB LR active. Horns are not splayed. All horns are the same model. ^ ← horn symbol. Thank you.

 40404040    4 - 40 deg horns side by side butted against each other.
   ^^^^ 

 60606060    4 - 60 deg horns side by side butted against each other.
   ^^^^

 60404060    4 - 60 40 40 60 deg horns side by side butted against each other.
   ^^^^

 40604060    4 - 40 60 40 60 deg horns side by side butted against each other.
   ^^^^
It is not that simple.  How large are the horns, vs where the components are in them (the spacing of the components is what is key),

What freq are you looking for? THe interference can vary a lot with freq

 What is the cut angle of the cabinets.  Very often the horn wall angles are not the same as the cabinet walls  You may see a 60* horn with cabinet walls that are 15*.  The cabinet walls should be 1/2 of the rated pattern

You really need to state the specific models you are looking at, as the rated pattern may not be the actual pattern (in most case it is not).  It may be-give or take a bit.
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Jeff Bankston

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Re: Comb Filter Questions
« Reply #5 on: October 04, 2021, 03:40:23 PM »

Pretty simple CAD task to draw adjacent triangles to get a rudimentary idea of where comb filtering will occur. But, it would be helpful to know the center-to-center distance between drivers and the model of waveguides/horns in question, as advertised dispersion angles are only at certain frequencies.

Dave
24" center to center. DDS CFD 2-60X Pro horns.  Radian 850PB 2" drivers.

http://usspeaker.com/dds%20cfd-2-60x%20pro-1.htm

http://usspeaker.com/radian%20850pb-1.htm

« Last Edit: October 04, 2021, 03:43:22 PM by Jeff Bankston »
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Jeff Bankston

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Re: Comb Filter Questions
« Reply #6 on: October 04, 2021, 03:41:40 PM »

It is not that simple.  How large are the horns, vs where the components are in them (the spacing of the components is what is key),

What freq are you looking for? THe interference can vary a lot with freq

 What is the cut angle of the cabinets.  Very often the horn wall angles are not the same as the cabinet walls  You may see a 60* horn with cabinet walls that are 15*.  The cabinet walls should be 1/2 of the rated pattern

You really need to state the specific models you are looking at, as the rated pattern may not be the actual pattern (in most case it is not).  It may be-give or take a bit.

24" center to center. DDS CFD 2-60X Pro horns.  Radian 850PB 2" drivers. Operating frequency 1500-16K. Cabinets are 24" square.

http://usspeaker.com/dds%20cfd-2-60x%20pro-1.htm

http://usspeaker.com/radian%20850pb-1.htm




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Scott Bolt

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Re: Comb Filter Questions
« Reply #7 on: October 04, 2021, 03:49:58 PM »

23" center to center. DDS CFD 2-60X Pro horns.  Radian 850PB 2" drivers.

http://usspeaker.com/dds%20cfd-2-60x%20pro-1.htm

http://usspeaker.com/radian%20850pb-1.htm
The biggest comb filtering happens because of 2 speakers set one stage left and one stage right.  The angle the horns spread the sound mostly effects WHERE the comb filtering happens.

The REASON comb filtering happens is because of time delays between when the sound from one speaker hits a position to when the sound from the other speaker hits the same position.  If your speakers are right next to each other, it is of less consequence than when they are separated by 40 feet across a stage.

While the combing is frequency dependent (because different frequencies have different wave lengths) the most obvious filtering happens at lower frequencies.

In addition to the sound being generated at different distances from the listener, most rooms also have reflections within the room that not only arrive at different times, but are reflected out of phase as well.

For inside gigs, I don't think the horn splay is anywhere near the biggest problem to think about.  Outside?  I still think there are bigger issues to consider, but lots of people seem to think it is a big deal, so it is possible I am wrong ;).
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Jeff Bankston

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Re: Comb Filter Questions
« Reply #8 on: October 04, 2021, 10:11:23 PM »

I was just asking if someone had the program that would show the differents  colors that show the hot spots of comb filtering
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David Sturzenbecher

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Re: Comb Filter Questions
« Reply #9 on: October 04, 2021, 10:35:25 PM »

I was just asking if someone had the program that would show the differents  colors that show the hot spots of comb filtering

Anyone can use Meyer’s Maap, Danley Direct, EASE Focus, d&b soundscape, L Acosutics Soundvision, plus probably a have dozen more.  All those programs are available to you at the low low cost of one hour of your time to watch a 15 minute YouTube video and 45 minutes to play around with the horn patterns of your liking.  Plus, acoustical modeling opens up a whole new world of “ah ha’s”.

And if you are using windows XP on your daily driver computer, I pray you never log onto anything that has any sort or banking or credit card info
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ProSoundWeb Community

Re: Comb Filter Questions
« Reply #9 on: October 04, 2021, 10:35:25 PM »


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