Tang Band W3-881SI Line Array Help

[kctess5]

Hey guys,
This is my first post as I'm making my first project after recently becoming interested in diy speakers so here we go...

I know a guy who's been doing diy audio for years and years who I collaborated with for some basic design stuff now I'm doing the more specific plans and everything. I bought the drivers I plan to use yesterday and I'm gonna do the build during christmas break.

I looked into a ton of designs including the theory behind them before settling on a line array design for a few reasons. First of all I really like how they look, which is a big part of what I'm after, second the guy I've been talking to has made a few line arrays and they sound absolutely amazing, and third I'll be the system in small rooms so the near field response is nice.

I got 14 of the Tang Band W3-881SI full range drivers on factory buyout ($8 for the win!) for this project, though I only plan to use 6 for each speaker I wanted two extra to play with, maybe a TABAQ design for my brothers dorm room or something. I originally planned on using 8 for each speaker, but I couldn't get the impedance where I wanted it and I didn't have the budget for 12, so 6 sounded pretty good.

I was thinking about porting the speaker and tuning it to around 50 hz for some nice bass response but I decided it would be easier to not have to deal with the more complicated design and build and just go for a sealed enclosure. I plan to pair it with a (sub)woofer actively crossed over at 100ish Hz for bass response and then use a .9375 ft^3 tower which should be pretty flat above around 106 Hz. After messing around with a bunch of designs based on size limitations and preference I chose a box with internal dimensions of 5' x 6" x 4.5" for a nice tall tower. I was planning on having the six driver line start around an inch from the top. I will use 3/4" MDF which is definitely adequate for these SPL levels.

The drivers will be grouped as closely as possible, probably around 3.5" center to center, but I'll know better as soon as I receive the drivers and break out the dial calipers. This is not ideal based off of line array theory which says the CTC length should be like .678" apart but thats not even close to possible with these drivers. But I'm going to try not and worry about that haha.

I will be able to post detailed dimensioned drawings when I have time to make the things on autodesk inventor.

I plan to replace my not so good receiver with a 50ish watt T class amp as soon as I can. All I really use for music and tv/movies these days is my Mac with the 3.5mm jack output so I really don't need a full on receiver anymore.

Mostly what I want to know is what sort of things I need to take into consideration while designing it such as unwanted quarter wave resonance or whatever. From what I've read with sealed enclosures I shouldn't have to worry about this too much but I don't know for sure. Also any general advice would be awesome (especially about using a ported or sealed enclosure), its my first speaker so don't be afraid to tell me if I'm doing something wrong.

Thanks for your help!

[planet10]

With only 6 per side it is not exactly a line array.

5 could be used in an WWW(MT)W, XO at about the baffle step.

dave

[kctess5]

Thanks I'll consider that. Idk if I need a tweeter though because these drivers go all the way up to 20000Hz.

I was thinking of making another (quasi)line array of like 4 low end woofers (ie 6.5in) drivers with just a low pass filter at 100Hz to go along with these not so much for the near field effect but the higher efficiency, that way I could just use one T class amp instead of a separate sub amp which would be a bit cheaper. Of course then I couldn't easily change the relative volume without an equalizer...

[planet10]

One of the drivers is acting as a midTweeter (hence the brackets around (MT))

dave

[norman bates]

combing.... bad............

But 4 drivers may work (run wide open or crossed 100-200hz).
And 4 of those should equal about the area of a 6.5" driver.

check out a longer array (32x2") and the issues........
Parts Express DIY Project
especially the unequalized response and the jagged step response.

good luck and get back to us all.

Do you have any pics of the other guys arrays ?
Are they full range drivers ?

Norman

[kctess5]

Sorry I don't have specifics or pictures of his system cause I saw them before I really knew about speakers. I know the main line arrays are planar tweeters and I don't remenber how he arranged the midbasses.

What if i did 4 of them wide apart in a ported box, winisd seems ok with tuned to 45 Hz with .9375 cubic feet (max size I want to go) then I could cross the sub in lower around 45 Hz and i wouldn't have to have it on. What do you think?

From what I know of physics I would guess that combing is a combination of either destructive or constructive intereference based on wavelength and the resulting phase separation of the sound waves between the drivers. Is that about right?

[planet10]

Originally Posted by kctess5

From what I know of physics I would guess that combing is a combination of either destructive or constructive intereference based on wavelength and the resulting phase separation of the sound waves between the drivers. Is that about right?

yes. So getting the drivers as close together as possible is a goal. The XO of 4xW to the mid-tweeter will be in the neighborhood of f = 4560/(cabinet width in inches). One does to ideally want to set this to somewhere in the range of the bottom of the saddle of the drivers impedance curve. The 4xW are wired series/parallel to end up with the same impedance as a single driver. This is a situation where a 1st order series XO works well.

dve

[koserthal]

Maybe you're able to get a curved front (ratius is distance to your listening area) so all speaker are directed close to your ears. I build such a system with Visaton 8" BG20 and B200 . Sounds absolute phantastic

[planet10]

Note that koserthal's speaker is a true floor-to-ceiling array.

A focused array overcomes the combing issues, but at the expense of a VERY small sweet-spot. It is like giant headphones.

dave

[cogitech]

Has anyone ever done a line array configured such that every other driver is angled slightly opposite of the drivers above and below it? What I mean is, all the odd drivers "toed in" slightly and all the even drivers "toed out" slightly. Perhaps this would reduce the combing effect (?) while also increasing horizontal dispersion. The optimum angles would have to be worked out based on driver specs, I suppose...