need plans for a good line array |
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7810 |
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Posted: 09 March 2010 at 7:40am |
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Not the old one. New one is ok. And Oberton, B&C, Beyma, BMS all makes wave guides ready to use. |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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Wish I had the time to further develop the HF and add the low mid section ...... |
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mykey-
Old Croc Joined: 03 March 2010 Location: ID/UK Status: Offline Points: 6114 |
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mykey-
Old Croc Joined: 03 March 2010 Location: ID/UK Status: Offline Points: 6114 |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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I don't think half the commercial manufacturers know either ! |
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Sibulus
Registered User Joined: 11 October 2006 Status: Offline Points: 901 |
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probably best not to bother then. |
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http://soundcloud.com/judas-beast
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7810 |
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Yeah we all know the theory very well and you dont have to remind us. But at the end it is all in the way you are using it. I have 4 boxes per side and do events for some 1500 or 2000 people with it and i dont have to throw the sound 40 meters. So in a environment that i am using my system it does not have to achieve that 3db attenuation per doubling the distance. So it is working for me.
And now you can get "real" wave guides from P-Audio or some other manufacturers for arround 50 uer per lens and just stick in the box and you have it done. |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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SebP
Registered User Joined: 02 February 2010 Status: Offline Points: 127 |
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No, the path lenght is very important for a line source. If you want to
produce a front plane wave, the path lenght must be the same, especially
at high frequencies (because of the short wavelength) Attenuation on a real
line source is in theory 3 dB each time the distance double (6 dB for a
spherical source). Ruban tweeters have this caracteritic, this is why
some companies use them.
So call the video waveguide "line array" if you want, but it will not work as a line source at high frequencies. |
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Centauri
Old Croc Joined: 29 November 2004 Location: Newcastle Aus Status: Offline Points: 1792 |
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And maybe I should have done too ......
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MarjanM
Old Croc Joined: 10 February 2005 Location: Macedonia Status: Offline Points: 7810 |
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SebP,
that is theoretically true. But having 2-3 cm of path length difference only maters if your ear is close to the source. having in mind that this is not how you use a line array box , which means you are at least 6-10 meters away from the source that imperfections smooths out with distance. Aahhh... I should have patented that wave guide :-) |
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Marjan Milosevic
MM-Acoustics www.mm-acoustics.com https://www.facebook.com/pages/MM-Acoustics/608901282527713 |
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staiper
Registered User Joined: 26 February 2004 Location: Croatia Status: Offline Points: 545 |
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I do not know dimensions of slots in video but if we take those are
roughly ~25cm deep and ~19.5cm height it will give front difference
(curvature) of 18-19mm which will satisfy full ideal up to ~4600Hz
(nearfield conditions - 1/4wl max difference satisfied) and up to ~9200
(far field conditions -max 1/2wl diff. satisfied)
This is not perfect but for most PA situations if setup is correct this may work fine as linearray HF. (..considering that MF and LF unit distances and crossover points are set correctly in respect to "line array" rules/acoustic physics ) Better situation will be if he have used 3 HF slots in same space so every slot will be ~13cm height and than wavefront curvature will be ~8 mm which will satisfy fully up to ~11kHz (~22kHz theoretical in far field -not optimal) which is more than enough for any real world situation for such simple to make device. More critical range with line arrays is MF drivers placement and setup (human vocal range .. where ears are far less forgiving at phase and time imperfections) |
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Just do it! ..or do not.. ;)
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SebP
Registered User Joined: 02 February 2010 Status: Offline Points: 127 |
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It's not simply marketing. If you want to produce a cylindrical wave (as opposite to spherical wave), the paths lenghts of the waves must be equal (as much as possible).
With the waveguide in the video, the path of the wave are shorter in the mid of the waveguide than the extrimities. And with this design, you have at least 3 cm path lenght difference, so it can't works as a line source no more higher than 3KHz. Edited by SebP - 08 March 2010 at 8:05am |
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