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Design ideas for a line array-looking reflex cab!

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kevinmcdonough View Drop Down
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    Posted: 13 March 2010 at 5:49pm
Damn, just lost a big massive post for some reason it didnt come up!Cry


Ok so to retype again and cut a long story short, have been messing about with a design all day for a friend and as I mentioned in another thread he is looking for basically a reflex cab but turned on its side and stacked vertically to give it a line array look and maybe pull in some more business through eye candy. The line wont be anywhere near long enough to really couple, normally he'll only use 2 or 3 a side but also working towards quarter wavelength spacing etc anyway just in case we ever build more and do get a decent length line.

So we started off by looking at just re-aranging my own double 12" + horn design but quickly ruled that out as it was becoming too wide. He would like to aim for about 700mm wide, 800 at most, so that he has flexability and for smaller shows maybe two can be stacked on top of a double 18 turned on its side and this can go right up to maybe 4 to 6 stacked on top of three double 18" sitting normally, which is about the biggest thing he will do just now.

So we moved onto looking at 10"s or 8"s in a concave V shape. Now for high frequency we couldn't find a horn for a 1" so were looking at using two Beyma WL4 on its horn at the centre of the V, but the depth of both the waveguide and the horn combined with being pushed back because of the V was making the cab a bit to deep.

So options are firstly to find a 1" horn that will work. I'd be happy to use a DE250 for this project would be about the right volume and sound nice, but cant find a 1" horn that will do minimum 90 horizontal, preferably 100 or so, and 15-20 vertical.

If we could get this would be a great help on many fronts because the price of the WL4 high section is coming in around £350 which is overkill for this, and a DE250 on a horn would be around £150 giving us an extra £200 to put into other parts of the cab or to build more tops.

If this cant be found then my other option is to stick with the WL4 high section and instead of using their waveguide shave a bit of depth off by putting metal plates over the V section and using that as the dispersion control, looking something like Arcline 12/Butterfly/GeoT. However modeling both the comp horns and the compression/slot firing that will now take place on the 8"/10" is all new to me how would i go about it?

Or any other suggestions are more than welcome Smile

k


Edited by kevinmcdonough - 13 March 2010 at 6:13pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mk2_ginger_biscuit69 Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2010 at 6:03pm
as you havnt asked a question ill just add some stuff.....
 
arrays are largely reflex, just with the topend being on waveguides, joining within the wavelength between cabs.
 
Need to make sure the dispersion is nice and wide, and the topend isnt going to be a combing mess on the vertical.
 
layout of dynacord cobra4.... similar to what you mean i think? reflex with waveguide, awesome with only 2 a side, more the merrier of course!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 13 March 2010 at 6:21pm
You can do the V shaped 2x10 section at the one side of the box (and save some width) and a 90-100 degrees v shaped horn for accommodating the HF wave guides. 
Marjan Milosevic
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kevinmcdonough View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 9:05am
hey

sorry GB, my questions if they weren't clear were firstly does anyone know of a good 1" horn that will do 100-110 (or at least 90) by 15-20, which will let me stick with a DE250 and solve a few problems.

Secondly if not then how do I model slot loading on a driver to get an idea of what changes will happen to the response/excursion/etc.

Yeah Marajan, we had hoped that by combining the two Vs we would be able to save on width overall (and he also liked the look of having the cab symmetrical and V shaped at the centre) but the trade off as i said is extra depth, so yeah i'm trying out a few different asymmetrical designs as well having separate Vs for the double 10s/8s and the horn.

Anyone with experience how far inward can i make the V before the small chamber created and load on the drivers will become significant enough on the response that I have to properly start to factor it into the design?




Edited by kevinmcdonough - 14 March 2010 at 9:07am
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 10:26am
You can also try the DB Q1 type of driver placement which looks very similar to this



As for using de250 i don't think that you can use that driver in a two way line array box. In order to do it as it should you will have to crossover from lf to hf at around 800Hz minimum. DE250 can not do that. You will need a driver like BMS4550. As for the horns i don't think that you can find complete line array horn. Only wave guides. But if you get wave guides than you don't need the horn. If you need any more explaining on how to do this i will elaborate more.

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kevinmcdonough View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 10:56am
hey

thanks again for your reply. However i would say bare in mind that this isn't a line array box that I'm designing. Smile  There will only ever be two to four of these used a side at a time and so i am not expecting any realistic pattern control or proper line array behavior in terms of the frequencies that the cone drivers will be producing, and as such am not sticking totally to the 1/4 wavelength bandpass/crossover ideals that you would when designing an actual line array cab.

It will basically be a standard double 10" or double 8" plus 1" comp cab on a horn. I'm looking at crossing over at somewhere between 1.2K and maybe 1.5 or 1.6K if i can push it just as high as that (which for example with 8s should be ok). The only difference from a normal trap cab is that it will be stacked vertically instead of horizontally to get the line array looks that promoters clamber over just now.

By V mounting the cone drivers so that horizontally they are within 1/4 wavelength at their centers, then at least in that plane they should combine line array style to form a single source up to crossover and be nice and even coverage horizontally, and if i can combine that with a good 1" horn (maybe 100 by 10 would be ideal, looking into making one myself) then simply stacking the boxes vertically with the bottom boxes around 10 degrees difference and the top ones maybe a bit less it should all be ok.


Interesting though what you say about waveguides not needing a horn. Although i have always kown what they done and how/why, this is the first time i've ever started looking at the specs of driver/waveguide combinations specifically and started trying to work with them, for example the Beyma WL4 that I have been looking at. It is a combination comp and built in wave guide, but in all of the data that is available on their own spec pages there is no mention of the directivity on its own. Indeed ALL of the measurements are made mounted on a horn and they make a horn specially that mounts two together, so i just assumed that it would NEED a horn to work and control dispersion in addition to the waveguide.

So if i was just to mount two or three of these on the face a cab, or for example the Fountek ribbons which is something else under consideration, to go for a proper line array cab then how would i know what kind of dispersion I was getting? Or would it just be test and see?


k



Edited by kevinmcdonough - 14 March 2010 at 11:13am
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MarjanM View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 11:12am
Then you should make some wave guides like i did.

http://forum.speakerplans.com/diy-compact-line-array_topic15820_post153170.html?KW=line+array#153170
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VPAS Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 11:19am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 12:21pm
ha, thats the ebay thing? I saw that the other day. LOL

Sad thing is though that someone will actually fall for that crap and end up very sorry Cry


In response to you Marjan now with a bit more research and a very helpful P audio document I realise the difference between a a waveguide and a horn, in that a waveguide is simply two flat pieces set at the angle you want the waves to travel out at, no complicated horn geometry or anything! :)  What benefit does the length/depth give if any, just more control or down to lower frequencies?


k
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 1:11pm
Originally posted by kevinmcdonough kevinmcdonough wrote:

ha, thats the ebay thing? I saw that the other day. LOL

Sad thing is though that someone will actually fall for that crap and end up very sorry Cry


In response to you Marjan now with a bit more research and a very helpful P audio document I realise the difference between a a waveguide and a horn, in that a waveguide is simply two flat pieces set at the angle you want the waves to travel out at, no complicated horn geometry or anything! :)  What benefit does the length/depth give if any, just more control or down to lower frequencies?


k


Both. Depth is needed for lower frequency loading of the driver but in this case has more to do with the desired narrow vertical dispersion.
As for wave guides it is a bit more needed in order to do it the right way then just to flat pieces but for me it is working quite good as they are and for what they are used.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 3:14pm
Sorry I should have been a bit more clear there. When i said about depth and the straight walls i was talking about what I could call the second part of the waveguide.

What I mean is after the compression driver there is a first wavegiude (usually some proprietary mumbo jumbo in pro cabs) that acts first. These would be the waveguide on the Beyma WL4, or perhaps things like this P Audio one, or ones from B&C and others. I assume they will be fairly complicated to design. This does all the path equalization and stuff and i assume sets the vertical dispersion etc.  I will buy a commercial one for this.

But after that you then have a second part, a much wider V shape. Shown in the first thread of yours that you linked to with your DIY waveguide, and also on this P Audio document  (half way down page 7 up to about page 10). Far as i can see this controls the Horizontal dispersion, and i assume not the vertical dispersion since its open at each end to let it combine with cavs above ane below. That was the part I was talking about when I said two flat pieces set at an angle.  And also when I was asking about depth.

If i'm trying to control the HF coming out of the first part of the waveguide to say 110 degrees, does the depth of that second part have a relation to what frequency it will be effective down to (which i'm thinking it would).  If I want to be effective down to my target crossover of around 1.6K how would I work it out, what kind of depth or mouth width am I looking at?

k


Edited by kevinmcdonough - 14 March 2010 at 3:33pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MarjanM Quote  Post ReplyReply Direct Link To This Post Posted: 14 March 2010 at 5:22pm
Both part of the horn are important. The first part on my horns (waveguide) is 28 cm long, which is determined by the desired vertical dispersion of 5 degrees. Second par is more for the horizontal dispersion then the loading. If you see some of the Renkus Heinz line array boxes or QSC Wideline, they dont have the second part in order to get to 150 degree horizontal dispersion.


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