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Old 3rd April 2005, 08:48 PM   #1
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Default Line array tweeter and sub configuration

I have recently started looking into a Line Array design to build the fronts for my home theatre setup.

Based on what I have read so far, I want to use 24 NSBs in a line array to create an 8' woofer line. If what I am reading is correct, this will give me response from the low hundreds Hz to a cutoff at 3kHZ.

Having decided upon this for my woofer line, I went to investigate drivers for a tweeter line, and was dismayed to find that I couldn't find conventional tweeters that I could use with a small enough c-t-c distance to achieve stable frequency response, and planar drivers are a bit out of my price range.

Does anyone know of a tweeter that has a small enough c-t-c and can be driven at 3kHz?

If not, how can I design point source tweeters into the cabinet to achieve a fairly flat response for a decent listening area?

In addition, my home theatre's sub has very nice response up to around 180Hz, but I am concerned this will leave me with a frequency gap in the response of audio that is routed through my fronts. Do I need to add a small sub to each of my line arrays, or will this be unnoticable as a cohesive unit?

Finally, as a contruction note, do I need to have a front panel in which circular cut-outs are made for the drivers in my line, or can I run essentially rails down either side, and just screw in the drivers on either side (I noticed the NSBs have square panels). This would save me a lot of work, but I am curious if there is an accoustic reason not to do this (it doesn't seem like anyone else has used this method).

Thanks in advance everyone,
Scott

oh, and if this idea seems to outlandish, please tell me, I'm still pretty much a newbie to all of this stuff.
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Old 3rd April 2005, 08:50 PM   #2
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oh, and will I have to put an equalizer in line with the NSBs to flatten out their frequency response?
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Old 3rd April 2005, 11:08 PM   #3
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Default NSB Line Array

try this tweeter. http://www.partsexpress.com/pe/pshow...number=269-708

they won't go down to 3000, but if you severly underlap the NSBs (say around 1500) with a first order electrical, and then cross the tweet at around 5000 - 6000 it should tone down the nasty midrange of the NSB.

i am currently thinking about building this setup using 12 or 16 NSBs per sideand have put a little effort into modeling a x-over. if you want i can email you the Passive Crossover Designer files (along with the frd and zma files). i don't know if the design is any good, but it might be a good starting place for you. and the price of the tweeter can't be beat!

to answer the subwoofer question, you might notice a little separation if you cross the sub in near 180, but it shouldn't be too bad, so long as you keep the sub nearly equidistant between the two arrays. it would probablly be less noticeable crossed at 100 or 120, plus the natural roll off of the NSBs is around 100, which would help as well. if you don't have a particular budget in mind though, it wouldn't hurt to have a sub in each tower, just much more expensive.

as far as running the NSBs along two rails, i wouldn't recommend it. it would be far too unstable and leak a lot of air. as far as i can tell, there really isn't a good way to mount the NSBs on anything with out a certain amount of time (and frustration). i've used them in 3 different designs and had trouble mounting them everytime. one thing i have yet to try, and what might work good for you, would be to try rear-mounting them. that way you can cut simple circular holes instead of trying to fool around flush mounting them from the front. but that's up to you. i would suggest playing around with them on scrap board before cutting out the final baffle, that way you can choose the one that seems easiest for you.

finally, active equalization can do wonders for these inexpensive drivers.

try checkin out this site for other ideas:
http://www.ipee.com/NSB/NSB.html

hope this helped, or at least gave you some ideas.
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Old 3rd April 2005, 11:51 PM   #4
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That cleared up alot. Thanks.

Just to clarify, I can use those tweeters to make a line array of their own (and at $1.50 per foot, I might go pretty close to the full 8' length of the woofer line). My one question is what did you mean by underlapping the NSBs? I'm sorry, crossover design is the one area I have absolutely no knowledge of.

And if the NSBs don't roll off until 100Hz, I'll just really on them I suppose -- I can always stuff or port the box.

If anyone else has information that might help me in this project I would much appreciate it.
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Old 4th April 2005, 06:55 AM   #5
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normally you would crossover both the woofer and tweeter at the same (or nearly the same) frequency. underlapping (in this case) means crossing the woofer over at a lower frequency than the tweeter. by doing that the frequencies above the crossover are attenuated fairly slowly and the end result is that the nasty mids that the NSBs are infamous for will be tamed. unfortunately the tweeters are then forced to go a little lower than normal, but if you cross it in at about 5500 or 6000 it should be ok. you can always experiment, capaciters can be fairly cheap, and you can always buy better ones later once you finalize the crossover.

i used the NSB with a different tweeter (another buyout onkyo) as satelites for my PC speakers and they worked great with a sub. and with that many drivers per side, you should have no problem getting a decent output down to 100hz. they do definitely require a sub though.

hope that helped
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Old 4th April 2005, 02:46 PM   #6
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My NSB line array project 'diary'. Maybe you can dig up something
of interest.

http://www.caraudioforum.com/vbb3/sh...d.php?t=210115

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Old 5th April 2005, 02:37 AM   #7
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I've been doing some numbers with those tweeters, and I am still concerned that I won't be able to get them close enough together. It seems that the research says it won't sound too bad in the near field (which for an 8' tower should easily fill my room) (is this correct?), but I had an idea for possibly solving the problem. Would staggering the tweeters (two lines side by side, such that the center of the tweeters in one line were in between the centers of tweeters on the other line), effectively create a line array with half of the spacing?

Thanks in advance,
Scott
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Old 5th April 2005, 07:05 AM   #8
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that's where my knowledge stops unfortunately. i can deal with crossovers, but i don't know much at all about the physics of line arrays. try going to this forum:

http://www.pesupport.com/cgi-bin/config.pl

post your question again there and see what comes of it. they're a pretty good bunch of guys that should be able to give you a hand with it.
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Old 5th April 2005, 12:54 PM   #9
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Nano Man-

I have a set of OB Line Arrays (3-way active) and dozens more of both the NSB's and the 25 cent Onkyo tweets you're playing with. I'd love to learn more about your passive xover designs.

Would you share your info with me? (xonasis2000 (at) yahoo) Thanks.
__________________
onasis
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Old 5th April 2005, 03:02 PM   #10
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Does anyone know of a tweeter that has a small enough c-t-c and can be driven at 3kHz?

You should buy one of each tweeter that you are interested in
and do some listening tests before committing to a big array.

Try these;
http://www.partsexpress.com/pe/showd...number=275-035

I've notice that alot of people want to build line arrays with
the 50 cent midrange but they skimp on the tweeter selection.
Because it's a 50 cent midrange doesn't mean that it's a cheap
sounding line array. You can make those midranges sound pretty
good if you pay attention to the details of the design. If planar
are out of your price range then you should look at those $4 domes with 1.5 ctc spacing. Any other tweeter will be a compromise, either the spacing is too large or the quality of
the speaker won't be that great. That is why you should pick
up some samples to try.
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