genelec style monitor mimic dipole at some freqs?

mazurek · 16th August 2006, 12:59 PM

I have been doing a small study of directivity control in professional speakers, and also am doing the zaphaudio waveguide mod (will post measurements as soon as expoxy dries adequately).

I came across this thing, and was wondering if they intentionally make it sideways like that so that people can get d'apolito style cancellation lobes on each side of the room, except at woofer frequencies. They would produce a lobe at the crossover point, and the lobe is oriented horizontally, such that it would minimize sideways room reflections. To me this is similar to the dipole cancellation concept. If I were doing it, I would set the crossover from 100-200 Hz, do you think the lobes would be too wide to minimize room reflections? Anyone have a lobing at crossover frequency calculator?

http://www.genelec.com/products/1034b/1034b.php

pinkmouse · 16th August 2006, 01:33 PM

It's only that way round by default, you can pull out the mid/hi module to rotate it whichever way you desire.

mazurek · 16th August 2006, 02:52 PM

Hehe, I was wondering more about the concept of horizontal d'apolito at low crossover freqs to mimic dipole nulls. I'm not actually in the market to buy these

Tenson · 16th August 2006, 03:40 PM

I think the point pinkmouse was making is that they did not do it on purpose, its just a side effect of the design.

I'm not sure how much use it will be but have a look at a program called ArrayShow. It is not very accurate for small scale stuff as it is intended for PA systems but it gives you a general idea of the outcome of different arrangements.

mazurek · 16th August 2006, 08:46 PM

Thanks Tenson, it looks like the drivers have to be at least a half a wavelength away to get any side cancellation, so the concept would only work if the subwoofer is crossed fairly high, so its a no go. I thought this might be the case, but it was an interesting idea.

I wonder if the mid-tweet crossover point sometimes affects lobing patterns and room reflections, and people sometimes end up choosing a given point for that reason rather than distortion or other issues.

Tenson · 16th August 2006, 08:59 PM

Well, most speakers are designed with the mid and tweeters as close as possible so it is unlikely it causes much of a problem. Also remember that most are in a vertical arrangement so it would only effect vertical dispersion.

Remember that introducing a delay to one of the drivers will do a similar thing to changing the spacing.

Salas · 16th August 2006, 09:06 PM

It looks to me that they are achieving near cardioid with this baffle sculpture. At least they sounded as such to my ears in Prolight & Sound.

16th August 2006, 12:59 PM	#1
mazurek diyAudio Member Join Date: Aug 2005	genelec style monitor mimic dipole at some freqs? I have been doing a small study of directivity control in professional speakers, and also am doing the zaphaudio waveguide mod (will post measurements as soon as expoxy dries adequately). I came across this thing, and was wondering if they intentionally make it sideways like that so that people can get d'apolito style cancellation lobes on each side of the room, except at woofer frequencies. They would produce a lobe at the crossover point, and the lobe is oriented horizontally, such that it would minimize sideways room reflections. To me this is similar to the dipole cancellation concept. If I were doing it, I would set the crossover from 100-200 Hz, do you think the lobes would be too wide to minimize room reflections? Anyone have a lobing at crossover frequency calculator? http://www.genelec.com/products/1034b/1034b.php

16th August 2006, 01:33 PM	#2
pinkmouse diyAudio Moderator Join Date: Apr 2002 Location: Chatham, England	It's only that way round by default, you can pull out the mid/hi module to rotate it whichever way you desire. __________________ Al I conceive of nothing, in religion, science or philosophy, that is more than the proper thing to wear, for a while. Charles Fort

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16th August 2006, 02:52 PM	#3
mazurek diyAudio Member Join Date: Aug 2005	Hehe, I was wondering more about the concept of horizontal d'apolito at low crossover freqs to mimic dipole nulls. I'm not actually in the market to buy these

16th August 2006, 03:40 PM	#4
Tenson diyAudio Member Join Date: Feb 2006 Location: Kent	I think the point pinkmouse was making is that they did not do it on purpose, its just a side effect of the design. I'm not sure how much use it will be but have a look at a program called ArrayShow. It is not very accurate for small scale stuff as it is intended for PA systems but it gives you a general idea of the outcome of different arrangements.

16th August 2006, 08:46 PM	#5
mazurek diyAudio Member Join Date: Aug 2005	Thanks Tenson, it looks like the drivers have to be at least a half a wavelength away to get any side cancellation, so the concept would only work if the subwoofer is crossed fairly high, so its a no go. I thought this might be the case, but it was an interesting idea. I wonder if the mid-tweet crossover point sometimes affects lobing patterns and room reflections, and people sometimes end up choosing a given point for that reason rather than distortion or other issues.

16th August 2006, 08:59 PM	#6
Tenson diyAudio Member Join Date: Feb 2006 Location: Kent	Well, most speakers are designed with the mid and tweeters as close as possible so it is unlikely it causes much of a problem. Also remember that most are in a vertical arrangement so it would only effect vertical dispersion. Remember that introducing a delay to one of the drivers will do a similar thing to changing the spacing.

16th August 2006, 09:06 PM	#7
Salas diyAudio Chief Moderator Join Date: Oct 2002 Location: Athens-Greece	It looks to me that they are achieving near cardioid with this baffle sculpture. At least they sounded as such to my ears in Prolight & Sound.

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