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Old 16th February 2013, 02:21 AM   #1
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Default Tang Band W3-881SI line array problems

Hey everyone, so I have built a few sets of speakers/amplifiers in the past, and recently got the urge to build a new set of speakers. This was all triggered after finding all the glowing reviews about the Tang Band W3-881SI drivers. I had always wanted to build a line array type speaker before, but they have always been too cost prohibitive; until I found the W3-881SI drivers. At $8 each making a set of line arrays becomes a lot more feasible. So I opened up WinISD and designed a set of ported enclosures that would house 9 x W3-881 Drivers each, wired in a series parallel configuration to maintain an 8 Ohm impedance with no corossover or filtering. The enclosures were designed to be 52.75" tall, 4.75" wide, and 12" deep and would use 0.75" thick MDF which made the internal volume about 1750 in^3. Tuning the ports to 70 Hz would give a decently extended and flat bass response. I was excited about these speakers and ordered everything online and built the enclosures and assembled them all (pic below) . However when I hooked them up I was very disappointed. The bass response was decent as I expected it to be, but the rest just made me sad. The speakers just sounded dead, and lifeless, and somewhat echoey. Not pleasant to listen to at all. The off axis response was awful as well. Going from a standing to sitting position or from left to right changed the sound drastically. Especially the highs which seem almost non existent sometimes. Needless to say I am pretty disappointed. For future reference I am wondering if there is something I did wrong, or could do differently in the future. I am thinking that maybe some internal dampening (stuffing/felt/foam) might help some, but am wondering if there is something else I could do in addition to that. Currently I don't even want to use them, so I figured I might get some input form all of the experts on the forum before I put them away in the basement to rot.

Any advice you can give would be much appreciated.

Thanks for the help,

Charlie

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Old 16th February 2013, 02:56 AM   #2
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From what I know - which is very much - but it seems like:
1) drivers are too far apart
2) line array isn't tall enough which is probably causing the vertical issue (I think if it were from floor to ceiling the issue would be resolved)
3) short line arrays should have some curvature and possibly a crossover to limit high frequency reproduction to the central-most drivers

Please feel free to correct me on any of this as I'm still learning.
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Old 16th February 2013, 03:12 AM   #3
xrk971 is offline xrk971  United States
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Charlie,
First let me say the cabinets look great - really nice job.
I'm sorry to hear that they did not work out. These drivers should have nice mids and highs when used as single full rangers, so it is odd that you report their highs are lifeless when used in an array. How much damping/stuffing are you using inside? I suspect that what may be happening is that you have a long transmission line and the drivers are distributed at peaks/valleys of the waves and causing destructive interference. There may be a way to check to see if thus is what is going on.
1. Disconnect the bottom 5 drivers and run just the top 4 in 2x2 at 8 ohms. 2. Add stuffing to top 2/3 of cabinet. See if this improves the lifelessness. The bass will not have as good extension because port is too big, but sound quality should improve. If it does, I would go with just 4 drivers which will reduce effect of listening position in vertical. Seal off bottom 5 drivers and recalculate new port size. Now you have 10 more drivers for other projects. If you want to keep all 9 drivers, stuff entire cabinet densely to make it aperiodic. Bass will not be as good but it should sound better overall. The lots of stuffing is easy to try. Use cheap polyfill from pillows or open cell gray foam. In general, spacing of drivers should be as tight as possible for line arrays. If you go with 9 drivers, you will still have spatial up down sensitivity to listening position as array focuses sound into a vertically narrow beam - which is why line arrays are tall floor to ceiling deals or are curved.

If you want to use about same driver numbers convert back panel to have 4 drivers firing backwards in bipole config. Lose just one driver and seal bottom 5 front cutouts. The bass response of existing port should be ok still. Still need to stuff upper 2/3 of line.

Last edited by xrk971; 16th February 2013 at 03:20 AM.
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Old 16th February 2013, 05:58 AM   #4
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The drivers are far apart. You are hearing comb filtering. Also you will need BSC if there isn't one already. Seeing that you have 9 drivers, you could do frequency tapering, and call it a point source. Just apply a first order x-over around 500Hz, having the middle one be the HF driver. This will take care of the baffle step loss as well. You might even get away with keeping the same port, it will just be tuned a little lower.
By the way, they look really nice.
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Old 16th February 2013, 11:01 AM   #5
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Indeed ideally they should be touching each other. I would even double the number of drivers per side. Ps it is normal that the freq response changes dramatically when you stand.
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Old 16th February 2013, 09:04 PM   #6
mikje is offline mikje  United States
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I'm building a pair of line arrays with these The Madisound Speaker Store. I don't have the tweeter dialed in yet, but they sound pretty good.
Mike

$1 aurasound drivers in an array?
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Old 16th February 2013, 10:11 PM   #7
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Thanks for all the replies everyone. I tried "tweaking" the speakers some today by adding stuffing to the cabinets, as was suggested. This did seem to remove some of the muddiness from the sound, and it became much more clear sounding, but still it doesn't sound right. I read some more on line arrays, and I agree that I am getting some sort of combing effect with upper mid range frequencies, and reduced output in the high frequency range. That being said, if I sit with my ears at about the height of the center speaker they do sound fairly decent, but even moving a foot out of this sweet spot they sound poor again. Lesson learned on my part, I should have done more homework before rushing into a project like this.

I probably wont be using these speakers at all, especially since the "budget" speakers I made about a year back (pic below) sound much much better. Crisp highs, smooth mids, and deep lows, no matter where you are in the room. Plus they are pretty sensitive witch makes them great for parties. Oh well at least the line arrays look kinda cool. I don't suppose anyone wants to take them off my hands. I would be willing to part with them for a small price. :P

Charlie

Click the image to open in full size.

http://i193.photobucket.com/albums/z...h/speaker2.jpg
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Old 17th February 2013, 12:26 AM   #8
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actually, it is good you made it. That way you learn.

Combing is bad.

A flat full range driver array is bad.

You could try a focused array if you can tolerate a tiny sweet spot.

Norman
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Old 17th February 2013, 12:38 AM   #9
xrk971 is offline xrk971  United States
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Did you still want to try running with just 4 drivers to see if you can recover the investment? Here is a crazy idea: leave bottom 5 drivers in place but wired with a power resistor to act as a passive radiator, and seal off port. That's a lot of work into those nice cabinets so I am just looking for a way to recover.
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Old 17th February 2013, 12:54 AM   #10
Dissi is offline Dissi  Switzerland
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A simulation of the speaker at 1 m:

SimulationCharliepuch.jpg

And the off axis response at 3 m:

HorizontalSplCharliepuch.jpg
VerticalSplCharliepuch.jpg
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