In-wall NSB line array!

[mazeroth]

Building a cheap line array with the 4" NSB and the 3/4" Onkyo buyout tweeters. My brother's townhouse basement has 2x4 studs separating 2 rooms with 1 layer of drywall in the finished room. We have a small recording room down there with his killer Roland V-Drum setup, my 6-string and my other brother's bass. With our gear there's not much room for speakers to listen to music while we're chilling down there. What I did was hang 3/16" HDF and rear mounted the speakers to the HDF and then to the 2x4s. I ran 6 NSBs per side initially full-range to see if that was enough; PLENTY of volume but I could hear that 7khz. peak and it killed me. So I put in 6 tweeters per side, all speakers as close as possible, and now I need a CHEAP crossover. I used an online crossover calcualtor and got these results:

NSBs = 5.33 ohm 86db (8+8 8+8 8+8)
Tweets = 6.00 ohm 85db (4+4+4 4+4+4)

1st order Butterworth @ 3350hz (so PE's parts will closely match)
Capacitor C1 = 11.87 uF (PE sells a 12 uf)
Inductor L1 = 0.25 mH (PE sells a 0.25 mH)

I know the NSBs are 1db more efficient but that's ok, 1db isn't much and I'm not a super treble kind of guy. As far as the 3350hz, I'm not sure if this would be optimal? What do you guys think? Think the 1st order will cut it? Remember, cheap is the key word here

Also, would you spend $3.55 and get the better cap or get the cheapy?

http://www.partsexpress.com/pe/pshow...=027-430&DID=7
http://www.partsexpress.com/pe/pshow...=027-342&DID=7

You guys rock!

Thanks!

EDIT: I will be taking pics so you guys can check it out. We've only had it up with the NSBs and man, it looked COOL, especially since I rear mounted them! Not sure how it will look once we mount it with the tweeters!

[BillFitzmaurice]

The Onkyos don't handle much power, so go to 5-6kHz on the crossover. Having two lines and needing to tame the peak both require a high slope, so go 3rd order. With 1st order you'll have comb filtering until you toast the tweeters,which wouldn't take long. Use Dayton caps and Janzen coils.

[mazeroth]

Bill, thanks for the reply.

I remember reading a while back about guys running their NSB 4"ers full-range and just using a cap on the tweeters and having good results. This is a very cheap project just for kicks and I wanted it to sound better but only spending a few dollars. We sit 4-8 feet away from it tops so I'm not sure how bad the combing will be. I picked 3350ish because I thought using a 1st order it would help to knock down the 4" nasty 7db peak at 7khz. The wall was listenable with just running the 4" speakers full-range so I just want it to sound a tad bit better.

As always, any comments are greatly appreciated!

Thanks!

[BillFitzmaurice]

Using a 1st order LP on the woofs the only way it does anything at 7kHz is to have it cross too low to protect the tweets, which don't work below 5kHz anyway. Crossing at 6kHz requires 3rd order to tame the peak, but the smaller parts required to cross at 6kHz helps keep the cost down and the results are well worth the few extra bucks.

[mazeroth]

The problem going with a 3rd order is my brother. He didn’t even want to put the speakers in the wall because he’s beyond tight with his money. I then offered to put them up for free, on me. He agreed. After they were up he was quite shocked at how good they sounded for being so cheap, but we could both notice the lack of high-end and the 7khz peak was pretty obvious. For me to tell him he now needs ~$25 for 2 crossovers he’ll laugh at me and tell me I should have just left the 4” speakers by themselves. So with that, do you think it will sound better with the 4”ers and ¾” tweeters running a 1st order at say 50-6khz or better to have just let the 4” speakers run solo? I know the Onkyo tweeters have 4.7uF caps on the back of them that I could probably salvage so I’ll only need to get the inductors. Might cost 3 or 4 bucks. We plan on running this off a computer and can use an EQ on the computer to help tame that 7khz peak, I think

[johninCR]

Nice idea for using them in IB. Before you decide on a crossover, it seems like you'd want a much longer array especially for that type of use so you're in the plain of the array sitting down or standing up. Have you listened above or below the ends of the array? It's a huge difference.

[BillFitzmaurice]

Your brother is so tight that he squeeks. I'll bet if he took a dollar bill out of his wallet Washington would have to cover his eyes, it being so long since he'd seen any light. I wouldn't want to be the waiter when he goes out to dinner. Oh, that's right, no waiters at 7-11. He sounds almost as bad as my insane sister who only flushes her toilet with gray water reclaimed from the kitchen sink after doing dishes.

[cjd]

eesh.

You can do this with three components crossing with a 4th order acoustic slope at ~3800hz.

The guys with no crossover on the NSB must have dead ears or something, IMHO. Same goes for those liking to cross at 5k or higher. whee.

A single NSB + single Onkyo (269-702) looks good with a 1.1mH inductor/5.6uF cap-2ohm resistor zobel, and a 4.7uF cap on the tweeter (phase shield removed) - I believe the tweeter comes with the 4.7uF cap. If you series two of the Onkyos per NSB change the cap on the tweeters to 2.5uF. Tweeter is inverted.

C

[mazeroth]

johninCR - It's kind of wierd how it's set up and you'll see better once I get some pictures of it. I'll try to take my camera tonight and snap a few shots. We will be sitting 95% of the time down there so I'm not so worried about the line height. He basically said he wanted a little music down there and I showed him what I could do for about $15. We also have a few thousand dollars of music instruments down there and on the other side of the drywall is our little woodworking shop. There are some gaps at the floor that let saw dust through so we put up a cheap HDF wall to stop the dust from coming in. He's only renting the place for the time being so it's a quick fix. I saw the opportunity for the easy line array install and took it. I know the baffle should be thicker and secured better but for this application is makes do.

Bill - You nailed my brother. Some things he can spends thousands of dollars on (his drums and computers) and some things, like speakers, that don't mean much to him he won't spend more than 8 cents on. He has his priorities backwards. Oh, and he's actually a pretty good tipper, IF the waiter/waitress does their job.

Another thing I forgot is the ratings from Parts Express were done with 2.83 volts. The tweeters are 4 ohm 85 db while the NSBs are 8 ohm 86 db. This means the NSBs are actually ~4db more sensitive. Gah, something else to fix! I'll probably just throw some more of the tweeters up there to help compensate. I mean, hell, I do have 128 of them to use!

Thanks again for all the replies. I'll have to consider them and figure out what I, errr, my brother wants to do.

[johninCR]

Don't be a cheapskate, add $5 more worth of drivers, you'll be glad you did.