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Old 11th November 2004, 03:13 PM   #1
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Default First-timer - NSB line array - please help a newb.

This is my first post on this forum, so be gentle. I have been reading for some time, and doing searches on this forum. I think I'm ready to jump into my first speaker project. Since this is my first project, I want to do it absolutely on the cheap! That said, I also want it to be done right. Here's what I thought about: NSB line arrays. MMMMTMMMM 8 NSB's with a onkyo buyout tweeter in the middle. I have a sub in the system, so these won't see anything below 80 or 100 Hz. Now for the questions...
1) do you think this will be a good arrangement?

2) I've tried some of the on-line (winISD I think?) software to try to see how big to build the box, and I haven't had much luck, as I don't know which driver I should enter the T/S parameters for, and I don't know how to deal with the multiple drivers of an array. I tried, but I somehow ended up with a negative volume...pretty sure that's not right. Does anyone have plans for such a beast - or could someone help me determine how big my box should be (prefer sealed or ported - not open baffle.) ?

3) I just need a crossover from the array to the tweeter right? a 2-way. I don't even know where to start here. Pick a XO frequency I guess... but after I pick that frequency, how do I pick components to make that happen? Again, It would really be great if someone could offer specifics here. (maybe even a schematic ).


I have searched and pretty much read all the line array threads on this board, but I found nothing exactly like what I want to do. Closest thing I saw was a 3-way open baffle design...and there wasn't that much detail on it.

Sorry for the long first post, and thanks in advance for your help in getting me started on the right foot.

Regards,
David
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Old 11th November 2004, 03:30 PM   #2
RJ is offline RJ  United States
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Most people use an open baffle with a curtain on back.
The curtain can be fiberglass or better yet dacron fiber in sheets.
Here's a link of what other people have done with they're NSB's;
http://www.partsexpress.com/projects...jects.html#ami
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Old 11th November 2004, 04:41 PM   #3
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Welcome David,

You said "first," but haven't said anything about what you plan on driving them with or what room they'll be in, or what other electronic experience you have, but here's my advice.

Cheap is a relative term, and this hobby is very addictive. Once you've experienced the sound produced from a decent project, you'll want to continue tweaking and growing your system. If you've got two amps to play with, get yourself an electronic xover for bi-amping. This will give you a good start on playing with different drivers.

Buy the NSB's, they're worth playing with, but consider a more efficient tweeter, if you only want one in that line array

I just hammered together an OB line array 8"x12"x72" using a single Audax 91dB placed about 51" off the floor and a sealed woofer in the bottom. My first tweaking session is probably not optimal for you, as I'm playing with dealing with driving 4 ohm loads to high SPLs with GC's, but here's what you might try:

Wire the NSBs 3-3-2+ tweeter (with a 5uFcap) crossed over from a sub-plate amp with one of these in each cabinet. Or better yet, bi-amp with active X, plus the sub amp. (Tri-amp)

Like RJ said, OB is a good way to go. These will be big speakers and need room, but will sound even bigger. You won't be disappointed, but you might be hooked.
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Old 11th November 2004, 05:20 PM   #4
cjd is offline cjd  United States
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I'll also suggest open baffle.

And the Onkyo tweeters will generally keep up with only a single NSB, no better.

For a full line array, consider twice as many of the tweeters as NSBs - wire them in pairs in series, then mirror the wiring of the NSBs. I like 3-3-3 (nsb) and 2/3 2/3 2/3 (tweet) which nets an 8ohm load. You could do just 9 tweeters.

I also have an MMTMM with a Tang Band tweeter. It would keep up if I series wired another four NSBs for a 16ohm load, but I think it would fall short otherwise.

As for crossover frequency, they like between 3000hz and 4000hz IMHO. In different speakers I'm using 3200 and 3800. Too much higher and you have troubles getting the breakup rolled off.

C
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Old 11th November 2004, 06:11 PM   #5
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Everyone seems to vote for open baffle... Is there some inherent disadvantage in doing a sealed or ported system with this design?

I think I only want 1 tweeter, I guess I'll just pick one that's more efficient.
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Old 11th November 2004, 06:30 PM   #6
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The disadvantage is that you won't get to hear what OB sounds like, and why many here wont go back to boxes.

The music fills the room in a way that non-bipole boxes can't, and the listening sweetspot is bigger.
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Old 11th November 2004, 07:24 PM   #7
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I just finished my NSB lines a few weeks ago.

I have 16 NSBs and 18 Onkyos wired for an 8 ohm load. The crossover is a single 2 uF cap on the tweeters and an L-pad of 3 dB attenuation on the NSBs. The tweeters cannot keep up with the mids even though there are (approximately) the same number of them.

Furthermore, the Onkyo tweeters are not very satisfying musically. They will do the job OK but you get most of your imaging and "air" (whatever that is...) from the top end of the NSBs.

I should say that I treated the cones of the NSBs with two coats of artists varnish (Winsor and Newton) to smooth out the top end a little and it seems to have worked although I did not take any measurements.

My lines are 7 foot tall open baffles with 45 degree angle tapered wings that are 2" wide at the top and 10" wide at the bottom. Open baffle, as others have said in this thread, is something you should experience as it's completely different from a conventional box. The specifications of the NSBs lend themselves to open baffle alignment so it's a no brainer in this case.

If you're truly on a limited budget, go ahead and get yourself a case of the NSBs and do 16 a side and build a line of 32 Onkyo tweeters. Then you won't need the L-pad. To do this you will need to trim off the casing of the Onkyos so you can reduce the center to center spacing of the tweeters. The NSB line will be 64" and the Onkyo line will end up something like 72".

I have some pictures that I'll post when I get them processed (analog). In the meantime, keep us informed about your progress and your thinking. This is a fun project, both before and after you cut all those holes.

Good Luck.
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Old 11th November 2004, 07:36 PM   #8
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Be very cautious about building OB line arrays! IMHO is would be hard to go back to boxes.

line array version 1

Line array version 2
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Old 11th November 2004, 08:29 PM   #9
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OK, I'm convinced! OB it is!!

I may consider doing the "half chipco3434" setup with 1 of the Dayton ribbons, and 4 NSB's on top and bottom. Chipco3434 - would I be able to use the same crossover that you used in that case?


BTW, thank you all for your informed responses - this will really help me get started.
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Old 11th November 2004, 11:06 PM   #10
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I love dipole line arrays too. I just don't know about those Onkyo's though, plus too many extra driver holes and triple the wiring. I use one of these right in the middle of the array, http://www.partsexpress.com/pe/showd...number=272-115 .

You need an Lpad to adjust their output. You'll also need to tweak out the harshness. I use 6 pencil eraser size pieces of soft foam rubber stuffed down in the horn throat around the bullet. Afterward they are a great sounding, high efficiency tweeter with wide dispersion, for only $20/ea at PE. Probably much cheaper locally, since I get them in Costa Rica for under $15/ea.

A single supertweeter in the middle of the array gives you the ability to go with a very narrow front profile. Then put wings like cytokine did on his for a cool look. If you go with deeper, more swept back wings, you need to make one an inch or 2 deeper than the other to avoid cavity resonance and avoid wing damping.
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