Line Array tweaking?

**JonMarsh** · 29 March 2005, 08:43 Tuesday

Without more data (impedance plots, measured FR or Mfr's specs on drivers) it would be hard to comment meaningfully- your comments on the sound indicate there are some response irregularities, but whether they're possible to "fix" or not, and the best way to do so, is hard to say. Did you design the crossover with baffle step compensation for your actual baffle width (it's not hard to at least model a basic BSC function into a simulated crossover, say, using one of the FRD consortium free tools or Speaker Workshop (also free).

But it's hard (if not impossible) to do really meaningful work without measured data, especially if you're working near the limits of the driver performance (in frequency extension) because that has to be included in crossover transfer function target.

Certainly you didn't spend too much money for your first experiment of this type.

Myself, if I was going to make a low buck line array, I'd first listen to a single set of the drivers, maybe play around with an electronics crossover or simulation in LspCAD and see if as a small speaker (like desktop computer) you could get them to sound good together- then consider building a line with them, because it's just going to be more of the same- a lot more. If the basic sound isn't working for you, a bigger louder version with nearfield properties to 10 or 15 feet won't improve much on things.

What are you planning for measurement gear? It's surprisingly cheap to get going these days- for example, you could get LspCAD 5, which comes with JustMLS for measurements, and a Behringer mic and preamp. Or for free software, download SpeakerWorkshop. I use LspCAD 6 myself, really like it, but it's a bit pricier.

~Jon

**Jonasz** · 29 March 2005, 12:00 Tuesday

Ryan: You can read this thread.http://www2.hififorum.nu/forum/topic.asp?TOPIC_ID=36043
I know it's in swedish but you can always look at the pictures.

I guess this guy (avr7000) is going to build a line array similar to yours.

Jonas

**thylantyr** · 29 March 2005, 12:44 Tuesday

The NSB line array projects are sprouting all over the internet (fertilizer on weeds)

I'm building an NSB array also for a friend but the budget
is higher. The goal is to get great sound. The NSB midranges have potential to sound better with a
few mods, but it requires work. Mating those mids to
Dayton PT2's is a great combo, but you are looking at
$25 tweeters in a line [not cheap].

I have a 'diary' of my progress here;

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

The $4 Rustoleum lacquer mod does wonders to improve
the SQ of those NSB's.

The next audible mod was the phase plug mod, it requires
more work to make and it cost about $1.5 for EACH rocket
nose cone. You notice the SQ improvement mostly at the
higher frequencies.

I have a test box with two PT2's and five NSB's in a ported
box tuned to 100hz w/option to close the port. It's all
fully electronic setup and I can tweak the crossover to
get the best sound. Right now I use 2.5khz crossover, 18dB
slope.

I ran some full range tests with a modded NSB (lacquer + plug) and it sounds way better vs. a stock NSB, you can
actually tolerate the sound. The NSB's have the nasty 7khz
peak.

I also have those same tweeters and I was hoping that
maybe there was a way to mod the tweeters to allow
a closer center to center spacing but it doesn't look good.
You will have some comb filtering gremlins to deal with
or tolerate with those tweeters.

Right now I would disconnect the tweeters and focus on
getting the NSB's to sound best then figure out what
you can do with the tweeters later. One step at a time.

**Ryan T** · 29 March 2005, 13:53 Tuesday

Thanks for the responses guys. I have the behringer UB802 mic preamp and the ECM8000 meausrement mic. But my sound card is just trashy onboard and I havnt been able to get it working. So I'll be getting an E-MU 0404 sound card in a week or so.

The tweeters are about 3" center to center so I think they start having problems at 12K hz. Which is ok I guess. There doesnt seem to be much stuff past 10Khz in music anyway. I didnt use any BSC on the drivers. The enclosure is 3.5 Cu ft. With two 4" x 4" ports. I know the FR with 16 NSB's in that enclosure looks kinda nasty. But they wanted a much larger enclosure and I couldnt swing 10 cu ft

. There is a 1 dB boost starting at 240 Hz and it runs down to around 100 hz. The F3 should be around 80 Hz.

I did listen to them in a two way configuration and they sounded pretty good. I just think there are a few valleys and peaks in the FR that could maybe be tammed out. I was thinking of moving to a 3,800 Hz 3rd order crossover but I can see that before I can get any real wrok done I need those graphs. So I guess I'll have to shelve this one untill I can get my speaker workshop calibrated and running correctly :/.

EDIT: Heres the wiring diagram if this would help any.

thylantyr,

Are there any websites that show how to do the mods to the NSB drivers by any chance? I'd like to mess around with some of them. I have a few extra NSB's and those dome tweeters laying around so I might use them for testing.

Ryan

**thylantyr** · 29 March 2005, 22:49 Tuesday

I was researching google, diyaudio.com on the NSB's.
I got clues on what others were doing. Treating the paper
cone with various 'stuff', glue, lacquer, etc., I saw a phase
plug mod somewhere, unsure if it was for the NSB.

Page not found

http://www.partsexpress.com/projectshowcase/nsb/nsb2.htm

I tried the mods as suggested above.

Mod #1 - dampening the basket. I didn't hear any improvement in this mod so I ditched it.

Mod #2 - hole in the dust cap. Since I did the phase
plug mod which requires the removal of the cap, this
is moot.

Mod #3 - Coating the cone. I used Lacquer, 4 coats.
This improved the sound alot.

Mod #4 - For line array, the trim ring is a waste of time,
rabbetting is better. I don't hear any diffraction gremlins
as is.

Mod #5 - [not listed in above link] cutting the spider to reduce the resonant frequency. This made it sound worse.

Mod #6 - [not listed in above link], make a phase plug.
This is a good mod, but sorta expensive in relation to the
cost of the NSB. /hehe It cost me $1.5 per drive plus
sanding sealer and paint and 1 wood screw.

Mod #7 - [not listed in above link], add ferrofluid to the
NSB to improve power handing. This mod was very cool
<pin intended> .. The jury is still out though, I had some
issues to resolve after 1 month of testing it. I think the
sawdust in the garage clogged the driver. I re-doing the
test in a more controlled scenario.. I controlling the amount
of fluid on each NSB to see what happens.

I have a log here of details;

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

**ryoshu** · 05 April 2005, 22:59 Tuesday

A few suggestions

I built a pair of arrays a year or two back using the same drivers:

404 Not Found

http://www.ryoshu.com/line_array_full.jpg

I don't know that any amount of tweaking will make them sound "good", but they do sound impressive. A few suggestions:

- A steeper crossover. I used a 24 db/octave. Tricky and expensive so it may not be worth it.
- Coating the cones. Big improvement.
- Power tapering. Another big improvement.
- The bass is anemic, best to make an array of cheap woofers

Other thoughts...

Comb filtering is always going to be a problem even if you trim the plastic on the tweeters.

These are quite impressive in an "oh my god" kind of way, considering the money spent. They do okay on music and quite well on movies. The only downside I see is that you'll want to build a set of line arrays with better drivers.

Is that a downside?

/me stares at the rd75s in the corner

**denverdoc** · 05 April 2005, 23:36 Tuesday

The Rd-75's are very good but w/o EQ are both irritating and fantastic, and over the long haul likely to disappoint or lead to an ever diminishing number of "good" recordings, Just one guys opinion before and after DEQX,
J

Line Array tweaking?

Line Array tweaking?

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