NSB Line Array Project

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toxcrusadr

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I got a cubic crap-ton of drivers from a fabulous AKer (Guy Ornes - thanks Guy!) and I'm starting to think about what to make. They include a bunch of the venerable No Stinking Badges driver, a super cheap 4" full ranger from a few years back at Parts Express. I've always wanted to do a line array, and these might be a good starter project. I will need a bit of help with the design.

I've printed out Griffin's Design Guide for Line Arrays and intend to do some homework.

I thought about Open Baffle but it appears you need a fairly wide baffle for good bass response, just looking at some threads. These drivers already crap out at 100 Hz (Fs=105). I would prefer a narrow tower just for the looks anyway. So maybe a sealed or ported enclosure instead of OB would give the best bass response. Obviously one might need a sub with these too.

I went to DIYAudio with the parameters and first used their Sealed or Ported Calculator. It gives a result solidly in the Ported category (EBP = 117, 'either' = 50-90, sealed <50). Qes of the driver is 0.9.

Using the box design tool - note, I estimated cone diameter at 3" since I don't have one in front of me - I get an enclosure of 0.68 cu ft with a 1" dia port - and this is weird - the port length is minus -0.52". Does that mean I should just use a vent? Surely it doesn't mean the speaker should have an 'outie' ! The horror. :p

Now, since I'm thinking of stacking up 8 or 16 of these, how big does the enclosure have to be? Minimal reading suggests that with multiple woofers, you just multiply the size of the box accordingly and either expand the port accordingly or use multiples. 16 x .68 gives 10.9 cu ft - hardly a small line array!

Still looking around on DIYAudio etc. for threads on the NSBs.

What would you do in this situation?
 
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The most enjoyable post on DIY LA's I've seen comes from DIYAudio user 18Hurts. Emphasis mine.

The war over vertical line arrays continues

Did a lot of reading on those oddities of the audio world, the beaming/lobing issues in particular. Read about the corner loaded line arrays with all 3.5" drivers running full range and they work well with EQ. I'm sure the microphone shows a classic example of comb filtering on that puppy!

Listened to Keele's presentation on curved line arrays, researched PA line arrays VS curved arrays along with the hows and whys. Read the full report on the "Velvet Hammers" with 5" Foster woofers and the Apex Jr. tweeters crossed at 5 KHz.

In theory, all line arrays--the ones running all full ranges in particular--should sound like scrambled hash. The question I have is they don't... a microphone and a brain with ears attached process differently so I'm making sawdust to check it out.

I will NEVER build another 2-way vertical line array again! As my labor hits the triple digits in hours--I fully understand why people don't build the beasts. It has been entertaining to hear just the 5" woofers running full range, they don't sound right unless you're 2 meters back so they can "mix"? Boosted the bass +6 dB and clipped my 100 watt amp while hammering in remixed Onyx (rap/metal) and shook the floor. None of the woofers got close to their 3mm Xmax even with a clipping amp hitting the little 5 inchers with 30Hz.

These are not speakers to sit back and sip cognac out of a brandy snifter by any means. Plug a guitar into the things, set the amp to +11 and hammer the strings with a wood saw. The 96 tweeters will get hammered with clipping but 90% of the power going to them is burned off with power resistors (attached to an aluminum plate to sink heat out the back) Normal party speakers/guitar speaker/PA use is crank it till it clips then back it off a notch. Eventually it will be teamed with a tapped horn to take over the deep stuff but a dozen or two 5 inchers can take quite a beating without distorting.

Sometimes you just have to raise the pirate flag, make a ton of sawdust and build the things. Tweak it until it sounds the best and pray the metal roof don't rattle, the cement floor does not mess up the sound too bad and push the lawnmower into the nulls to improve the sound. As long as I can get decent sound in a garage, they are loud, durable and protected from flying parts, lubricants and beer foam--I'll be happy. My brandy snifter speakers are in the house--the party speaker vertical arrays complete with handles, grills, bumpers and genuine house paint "finish" sit in the garage.
Speaker beaming can be cured by a liberal application of Jim Beam
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Crickets? Any opinions on the two questions:

1) Does a negative port length result from a box calculator suggest using a vent (zero port length)?
2) What do you do with multiple woofers in a line array that would require multiplying the box size to such an extent that the box becomes huge?
 
Wish I could help, but I plan to follow along for future reference.

:lurk:
 
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I've been doing a little research and trying to glean what I can about what has been tried and what works and doesn't work. I'll be posting some links to threads on AK and (mostly) other forums about the NSBs.

Here are a couple things I've concluded:

Tweeters?
- There is a practical limit at the high frequency end besides just the driver's response curve - which alone is a problem with the NSB - plus there is the problem of beaminess at higher frequencies from a cone. Yet another issue with line arrays is related to wavelength and the distance between driver centers. In order to prevent bad interference effects, you should try to operate the driver below the frequency whose wavelength = the center to center distance. For a 4" driver that's 3,300 Hz.
- These drivers crap out way before 20KHz anyway. In light of these two facts, a tweeter array seems like a good idea.
- Some have used the Parts Express PT2 planar ribbon tweeter but they cost $35 each right now which runs into a lot of $ compared to the rest of the system. I'm sure they sound great but I am trying to see what I can do on the cheap.
- Another option is a single tweeter or horn in the center of the vertical array, like this guy did with a Selenium horn and AK Econowave xover:
http://www.diyaudio.com/forums/multi-way/95613-32-hi-vi-b1s-per-16-nsb-line-array.html
- PE has a sale on these 1/2" inverted dome tweeters, a pack of 10 for $25. https://www.parts-express.com/1-2-inverted-dome-tweeter-element-10-pcs--275-010#lblProductDetails
I ordered a pack just to see what can be done with them. They are supposed to go down to 500Hz so there should be no problem crossing over somewhere below 3300.
- I'm thinking of a relatively tall array like 5 ft. give or take, which would be a lot of the NSBs - maybe 16. Obviously the tweeter array wouldn't be as tall if I'm using a max of 5 drivers. But I have seen arrays with a shorter tweeter array next to the woofer array. I'm going to have to see if this will work. The inverted dome tweeters are not very sensitive (66 db!) so getting enough volume relative to the NSBs might be a problem. If nothing else I may end up using these tweeters for a smaller array for computer or TV speakers. A columnar speaker that can stand on either side of a flatscreen TV on a base cabinet is what I'm thinking for that.

One thing I find with many speakers is they lack 'air' or are harsh in the midrange or low treble. I liked this review of the 1/2" inverted domes:

"I have tried a bunch of these little 1/2" tweets, and I find the top end the most relaxed and extended. If you think even 3/4" tweets have a beaming problem and still lead to listening fatigue, using these as super tweets might do the trick. I typically use these with a 2" or 3" full range woofer. Woofers at that size will obviously beam the treble. These tweets allow me to listen at arm's length without any listening fatigue. After a couple of hours, the top end is still relaxed and airy. More airy than any larger tweeter can do at arm's length, no matter the price."

Other Design Stuff
This is an interesting design discussion thread:

http://www.diyaudio.com/forums/multi-way/45862-help-nsb-line-array-issue.html

Also this one:
http://www.htguide.com/forum/showth...y-tweaking&s=6e685f8e5c5c6c1154eb69625e6b605c

which mentions the cone treatment and also adding a phase plug to the NSB.

This thread: http://techtalk.parts-express.com/forum/tech-talk-forum/1442-anyone-have-a-documented-nsb-array
has a post by user Thylantyr recommending that if you REALLY want the best sound, go with a 16 NSB array at 2 ohms (yes you read right) and a full array of PT2's. Not in my budget.

But he also says if you're not going to do that, you can still do pretty well with some other designs.
"If you want to exploit that NSB sound, do the cone treatments, perhaps port the NSB's like I did, seal the drivers air tight using rope caulk, rabbeting the front baffle, sound condition
the chamber, etc."

I found another reference to 'Rustoleum lacquer treatment' and yet another to using diluted white glue. Apparently it makes the cones a tad heavier and stiffer and improves bass. So I would like to do that and will keep researching.

Crossovers
These will obviously need a separate sub or a woofer or two at the bottom of the cabinet. I haven't decided where to go with that yet. But assuming a sub that crosses over around 150 Hz, that can be the bottom end for the NSBs and their Fs is 106 so we're good. Someone said it was OK to run them full range because they will drop off anyway below 150, and let the sub fill in. So that would save on crossover complexity.

The above linked thread also has a post from someone who built crossovers and 2d order seemed to work well for them. He used an active crossover to work out parameters.

"When I ran the line full range, it got very shouty and shrill at higher volume. I'm running the 8 NSB series-parallel for a 4 ohm load. With first-order at 160 and ~3300 it sounded tolerable, better with 2nd order L/R at 160 and 3300, and better yet with 4th order L/R at 160 and 3100. Fourth order I'm not even going to try as a passive."

I'm thinking a 2d order L-R at 3300 is simple enough to execute as a start.

More later as I glean ideas. I still don't know how to do the enclosure (size and ports) but I'm sure I'll find it. There are some open baffle advocates but these drivers seem to want a ported enclosure, from the specs.
 
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Tylantyr says here:

http://www.htguide.com/forum/showth...y-tweaking&s=6e685f8e5c5c6c1154eb69625e6b605c

that the phase plug has its best effect on the NSB at higher frequencies and that they have 'a nasty peak at 7 KHz.' I won't be using them in that range so the $1.50 each rocket nose cones probably aren't necessary at this point.

He did 4 coats of spray lacquer on the cones. There's a link to another tweak thread in a car audio forum there but it's dead so some searching is in order.
 
I've also been reading about a line array that's reverse curved - the Dayton Audio Epique: http://www.daytonaudio.com/index.php/epique
The curve is supposed to do something fantastic in the floor and ceiling reflection department, and makes the darn thing have an extremely stable response curve in a much wider area around the room than a straight array. It has a 36 degree arc to it - although I'm not sure how far behind the speaker that point is located.
 
Power tapering is another way to correct some issues with LA's as discussed by Griffin ( http://www.audioroundtable.com/misc/nflawp.pdf ). A simple way to do it is to put combos of different numbers of drivers in series to increase impedance/reduce output as you go out from the center of the array. Unfortunately there are limits: the overall impedance can't drop too low, and you have to have the right number of drivers to allow combinations that reasonably taper the output. Things have to add up. I was considering a small array of 8 NSBs for starters but I may have to go to 12 to do power tapering. Some comments at DIYAudio suggest you need more than 9 of them anyway to get the advantages of a LA. I have 96 of them so there is no shortage.
 
User cptomes says here

http://techtalk.parts-express.com/forum/tech-talk-forum/1260-nsb-line-array-question

that 8 NSBs is a pretty short array anyway, and I believe this is right now that I see it again. There is a rule of thumb that 70% of ceiling height is either ideal or minimal. So a longer array is in order.

Only problem with that is having enough tweeters which always comes down to $. I will have at most 12 of the 3/4" inverted domes I ordered, per side. This can't be longer than a foot or so when placed as close as possible (to avoid combing at the highest possible frequency). What kind of effects will this have on the sound field for NSBs vs. tweeter array, especially in the region of the crossover...also if there's power tapering on the long NSB array, and none on the short tweeter array...yikes this is complicated.

I don't know if anyone is reading this but it's an interesting journey either way. :cool:
 
I found it - the nugget I was hoping for. An actual design that sounded good and was documented.

http://techtalk.parts-express.com/f...38-thylantyr-others-power-tapering-experience

My budget array has no power tapering in either tweeters or mids. I didn't want to use power tapering that would force an unequal power distribution across the drivers and force the
center drivers to 'work harder' because distortion would rise and power handling would
drop. I wanted the highest SPL and power handling possible.

There is no sound quality issues with the array. Everyone who hears the array is amazed,
unbeknowst to them the drivers cost 49 cents for the mids and $25 tweeters. Once they find out the driver cost, they scratch their head confused as the old stereotype comes into play
[cheap drivers can't perform well], lol.

Also, I haven't heard of anyone complaining about the lack of bass when playing music as
there is no other woofers or subs in the room only those NSB's in a ported design. lol

If I were to add a sub, the results would be sweeter, but his isn't my main audio system
so I don't care about doing upgrades to the 'TV room'.

>>Is there an audible muddying?

The sound is very clean, I crank the system to >115dB on average, upper midbass is
>126dB[c] with no muddying of the sound, clean as a whistle. After experience this array and it's full potential, I made plans to upgrade my main system, in the works, to a larger design. Also, I got addicted to DVD concerts now vs. audio CD. In spite that the DVD is compressed audio, the whole concert experience on the 53" screen is sweeeeet..... The audio in conjunction with the video makes the experience more enjoyable than just listening to audio without the video. This makes me want a 100" screen, lol.

>> I am running a line of 30 Dayton Neo tweeters and 22 NSBs for the mains.

Don't fear making a bigger array. One you experience the big array you might get addicted and realize that 'big' might give you a more life-like audio experience.

Four chamber per cabinet.
Four NSB per chamber.
1.5 cu. ft. per chamber.
6" port in the rear of each chamber.
Port length = ~ 1 3/8" [cabinet wall thickness
with roundover].
100hz tuning.

There is a peak in modeled response when you do this. Looks ugly to the naked eye, but real world performance is pretty sweet. It's easier to attenuate the peak with an EQ if there is too much bass vs. boosting bass which would overdrive the poor ole' NSB's into mechanical damage. I wanted to let the port do the hard work. I also have 12 presets in my digital crossover that alter gain, crossover, EQ, etc. I can select a preset that matches the material being playback better.

When you stand in the corner of the room, 32 NSB's playing, kilowatts of headroom, you can feel the upper midbass hit you. Pretty good for 49 cent drivers.
 
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There are some other bits I need to retrieve where he talks about using a Behringer 2496 crossover and biamping them, what worked for crossover frequencies, etc . I happen to have that same crossover and have not messed with it. :thumbsup:

Sounds like he built that 4-NSB module and got it to work and just multiplied it. I'm thinking of a single cabinet, if all the woofers are playing the same thing no reason to have separate ones. As long as the volume is right and there is a port for each 4 NSBs. I don't know how he worked out the box and port, but I trust the description of how this turned out.

16 NSBs is only 4 ft of array though [Correction: 5'4"], and as you can see above "don't fear making a large array". I'm thinking of adding two modules for a total of 6, that's 24 NSBs, so 6 ft tall [oops - no - 8 ft which is too much]. In 3 series pairs, those sets paralleled, you get 5.3 ohms [maybe 20 NSBs would be better, that's 6'8"]. A little demanding but not too bad. I gotta work on how to wire up the tweeters to get something close impedance-wise.

He used the PT2 planar ribbons which will be a major difference from mine. I did a little figuring and I may need a lot more of these little inverted dome tweeters to equal the output of the NSBs. Which would be OK since they are so much smaller they make a much shorter array anyway. I think I'll try it with the tweeter array centered vertically. I read something about breaking up tweeter arrays but without some definitive guidance I think that's too dangerous, comb filtering wise.

Making progress!
 
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Glad you guys are reading along with my journey. I hope you can tell I ain't no design engineer. I know just enough to be dangerous but hopefully I know my limitations. Please feel free to comment and make suggestions - this isn't a tutorial, it's a learning experience. ;)
 
I was discussing line arrays with Ed today (oldphaser). He knows quite a bit about them and more importantly, knows people who build them right. He will be at my house tomorrow morning at 9am so I will show him this thread and let him post his thoughts as to your questions

If you have a moment, check the Phoenix Audio Forum and drop him a PM and he will be more then happy to help or put you in contact with people who build serious line arrays. The kind where you can converse easily with the person next to you yet your experiencing 122dB+ SPLs. We were discussing 10ft high ones BTW
 
I was watching a few episodes of Long Strange Trip last night. I think it was #4 that dealt heavily with Owsley's Wall of Sound. Could this be considered the Grandfather of line arrays?
 
I experimented with line arrays back when I was married and had a house :) read all the white pages, talked with some gurus, and made some sawdust...

I went the open Baffle route with NSB's originally... I used an active xover, with a pair of Altec 15's in some Karlson cabinets. Sound was impressive in my 14 x 22 sunroom with vaulted ceilings...

v 2.0 I went with klh full range drivers - 8 per side. No power tapering...

I preferred the klh arrays, but there's many ways to skin a cat :)
 
Had some trouble posting yesterday and this morning. Northwinds, I must have skimmed over your post and missed the invite! I've joined Phoenix and will follow up on that. Thanks! There was also a thread over there on the Danny Ritchie Epiphany line array that's being discussed on a different thread here right now. Small world.
 
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