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snowflake View Drop Down
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    Posted: 31 March 2009 at 1:40pm
tried this out at a gig on saturday and seemed to work well. see void bass guide if you don't know what i am on about

http://www.voidaudio.com/support.asp

bass was pretty even around the room. not sure if it was down to the delta array or because we had a few more meters between stack and decks but couldn't get any bass feedback at all compared to loads in the same venue previously. also much quieter outside the venue. will definitely be trying this again.

Phil
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Points: 5189 		Post Options Post Options   Thanks (0) Thanks(0)   Quote toastyghost Quote  Post ReplyReply Direct Link To This Post Posted: 31 March 2009 at 2:20pm
We're going to be trying this on a fairly large scale for the main stage of a festival this summer - it's pretty close to housing and the hope is that with careful planning we can actually get some bass at the front of the stage.

Did you just guess roughly where to put the cabs, or do some proper calculations?
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Does anyone know how the delay time is calculated for a Delta Array? Rog uses 2.5ms in the example but I can't find an explanation as to how this was calculated.. Is it just the depth of the cabinet?
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I'd say it depends on cab dimensions and phase / group delay response. I would start with about 2,5ms and adjust until it sounds right at the stage and in the front.
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Originally posted by APMAUDIO APMAUDIO wrote:

Does anyone know how the delay time is calculated for a Delta Array? Rog uses 2.5ms in the example but I can't find an explanation as to how this was calculated.. Is it just the depth of the cabinet?


in theory it's the distance between the front and back of the array. my cabinets are 70cm but i overlapped them 20cm to get it all strapped together - so 2*70cm - 20cm = 1.2m or 3.5ms

but probably best to have a play around and see what sounds best
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Are you using Reflex cabinets like in the example?
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Yes,we will be using reflex cabs.Already tried it with 2.5ms and seems to work quite well but would like to know where this value came from..
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Originally posted by APMAUDIO APMAUDIO wrote:

Yes,we will be using reflex cabs.Already tried it with 2.5ms and seems to work quite well but would like to know where this value came from..



reading back through the paper it doesn't actualy explain where the value comes from. the distance form front to back of the array makes sense to me but that would give a value of 4.4ms for the reflex cabinets in the example (76cm deep).
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search psw study hall, theres been papers in there before with more information, but i remember the concept was meant to have been patented or something stupid, but explains in detail the ways to achieve it.
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hey

i've only had a quick flick through Rog's paper will have to read it properly later, but based on memories of some stuff i read in PSW as as to the time i'm pretty sure its to do with what frequency you want the waves to cancel out at.

from my shaky memory, for waves to cancel out we all know they have to meet out of phase, one of our basic rules, and so the path length of the sound coming from each set of subs (back and front) has to be such that it is half the length of the center frequency that you wanna cancel.

So you arrange the subs, either with physical distance/time delay/phase inversion or a combination of them, so that as the sound travels back from the front row of speakers and meets the back row, it meets it out of phase and cancels everything heading backwards towards the stage. 

Now obviously every frequency has a different wavelength, and so while this will work perfectly (theoretically) for the frequency (and hence wavelength and hence distance) you have chosen it will gradually be come less effective as you move away from that frequency and the path lengths change and so the waves arent meeting out of phase.  From what i remember you get maybe an octive eithe side of your chosen frequency before the path length difference changes enough that it stops working.

As i said but hazy memories, if you look back at the PSW articles which will be in the forums and study hall there, and also Rog's paper (which i intend to do later or tomorrow), i'm sure you'll be able to piece it together properly.

k


Edited by kevinmcdonough - 14 April 2009 at 1:48am
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Originally posted by APMAUDIO APMAUDIO wrote:

Yes,we will be using reflex cabs.Already tried it with 2.5ms and seems to work quite well but would like to know where this value came from..

 
It came from playing with the settings untill the maximum amount of rear rejection was found. I did this with real cabs and then applied the figures to the simulation software to look at the graphical outcome.
 
There are just too many variables to have a single calculation when it comes to cardiod setups. GD, port tuning freq, cab size and many more things make it impossible to have one setting that fits all. Use my settings as a starting point if you are using simular type cabinets, but you really need to measure both froward and backwards outputs and play with the settings untill you get what you need and where you need it. You can also use the method discribed by Kev as a rough starting point.
 


Edited by Rog Mogale - 14 April 2009 at 5:29am
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Points: 2020 		Post Options Post Options   Thanks (0) Thanks(0)   Quote kevinmcdonough Quote  Post ReplyReply Direct Link To This Post Posted: 14 April 2009 at 9:15pm
hey

for anyone interested in Cardioid arrays check out this PSW thread, which has LOTS of good info and a pile of real world testing done by some of their guys. was the original thread i read way back when i learned about most of this stuff....

http://srforums.prosoundweb.com/index.php/mv/msg/3954/0/0/0/

also other PSW threads that have good info on various different ways of controlling sub patterns and steering the sound in lots of different ways depending on what your looking for......

http://srforums.prosoundweb.com/index.php/m/125153/0/?srch=%22cardioid+array%22#msg_125153
http://srforums.prosoundweb.com/index.php/m/233721/6671/#msg_233721
http://srforums.prosoundweb.com/index.php/m/235311/0/?srch=%22cardioid+array%22#msg_235311
http://srforums.prosoundweb.com/index.php/m/314119/0/?srch=%22cardioid+array%22#msg_314119

Lots more if you do a search on PSW but they seemed to be the best ones.

I think between these and the two parts of Rog's sub guide when the second one becomes available you'd have a pretty good handle on the whole situation.


kev
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