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Old 16th December 2004, 02:39 AM   #1
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Default Newbie, Line array questions with TC11MG Vifa and TB 25

I have just gotten back into home audio for a high school senior project for my son for our simple HT system.

I bought 24 Vifas on PE at $4 each and 10 Tang Band 25-302S tweeters on Ebay for $10 each.

We were going to build a modified(experimental to say the least) MTM setup, try some different large open baffels at first in either

M
M
T
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M
M
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TT
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MM
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etc, configurations and then a center of

MMMTTMMM

as that is the best we could fit into the very well built but limited space Ent Center I built years ago in an old world cabinet shop(MT joints, Rabbited where applicable, raised panel doors, leaded glass, had to gut out alot of the center to install our 42" Plasma, barely fit)


But we are now thinking of going to a line array for the front, same center channel and no rears, never really liked them anyway.

For power I have an HK DPR 1001 that I am quite fond of. I do not need 7.1 so am studying it to see about an internal mod, I imagine not to hard to do, so I can use two more of the amp channels to bi-amp the front speakers.

So, my questions are:

1) what is the minimal drivers per side in a LA? I am thinking 10 mids and 6 tweeters, recommendations are welcome

2) anybody used these and like them, or dislike them?

3) We may build in a sub in the bottom of each unit, any reason not to?

Whatever you think, we want to hear it, we just want this to work really well but are running a bit low on time so need to get hauling **** on it right after the holidays.

Anyone have car audio questions, I have quite a history in that arena and specialize in sound deadening, glad to help out.

(My last high end system in my Tacoma had an Image Dynamics ID DAC20(dual 20 bit ladder DAC last sold in 1995 and just killed any car audio HU's even my $2,500 Denon Z1) I ran balanced lines, 20 volt level through my moddified rack mount EQ's and crossovers, Rainbow Reference front speakers) I know many do not think you can do much in a vehicle, I beg to differ, the owner of one of the oldest home audio shops in the world loved my truck

Home audio is fairly easy compared to a car so we want to go a bit deeper into it and build a fun project with some killer sounds and looks for low cost, nice challenge We will use some sort of exotic veneer on them, probably just the face and the rest in black.

Thanks!
Rick
RAAMaudio
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Old 16th December 2004, 06:54 AM   #2
sqlkev is offline sqlkev  United States
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Hey Rick,
Welcome to DIYaudio
I highly suggest that you read Dr. Griffin's paper on inexpensive arrays (http://www.prism.gatech.edu/~gte929u/LinusWP.pdf)

To answer your questions,
1) There isn't a minimum requirement for a line array, at least I don't think there is. The main difference between the larger number of drivers and less drivers would be efficiency and near/far field distance.

2) I have use neither of the drivers, sorry

3) It looks like you're going to need a sub that would need to fill the bottom octaves, try to at least include BSC in your design so that your subs won't have a hard time playing too high. Be sure that your subs will be able to keep up with the line array though


Here's what I think,
Since this is your first line array project, I think you should consider the NSB line array project instead. It's an open baffle project, therefore not much work is needed. Plus, it's quite cheap compare to your planned project. (I bet you'll be amazed with the 87cent driver )


BTW Rick, I'm a frequent on ECA too, different SN on there though
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Old 16th December 2004, 08:11 AM   #3
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Thanks, really appreciate your inputs

I am looking into alot of info, already read the Doc's info as wel. My main concerns are near field, not a large listening room but then again, maybe the next one will be bigger, renting until I build on my property.

I have the speakers already so really want to use them! I do not mind buying a few more for the system if needed and want to match the drivers for the center channel, just want to make sure I have enough and a couple of spares each just in case.

I will check out the NSB array, sounds fun, love good sounding cheap stuff!

Rick
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Old 16th December 2004, 02:30 PM   #4
RJ is offline RJ  United States
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It would help if I had the T/S specs on the Vifa woofers and the size of the tweeters.
In a line array the tweeters center-to-center distance is critical to avoid combing.
There's currently three designs that a lot of people use.

W T
W T
W T
W T
etc.

W T
W
W
W T
W
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W

and
W
W
W
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W

I've built the first set described above.
10 5 1/4" woofers and 6 planar tweeters 58" high.
To hear a movie or music on these is simply wonderful and it's only in stereo.
The imaging is so good that the middle phantom image is very well placed no matter where you sit.

12 Vifa's per side would be about 56 to 60 " high.
I should have built mine to be 6 foot high. Standing up I lose the high end. I'm going to raise the speakers up by building a base to compensate. Nobody lays on the floor to listen anyways.

If you build the second or third set described above, the tweeters should be at ear level.

Need more help just ask!!!!
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Old 16th December 2004, 05:45 PM   #5
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Thanks for the info and advice



Vifa Specs:

http://www.partsexpress.com/pe/pshow...number=299-492

Specifications: *Power handling: 50 watts RMS/100 watts max *VCdia: 1" *L1: .40 mH *Znom: 6 ohms *Re: 4.25 ohms *Frequency range: 110-6,000 Hz *Fs: 110 Hz *SPL: 88dB 2.83V/1m *Vas: .07 cu. ft. *Qms: 1.63 *Qes: .60 *Qts: .44 *Xmax: 1.5 mm *Dimensions: Overall Diameter: 5", Cutout Diameter: 4", Mounting Depth: 2-3/4".

I am a bit concerned with the low freq limit, should of thought that one over more before buying 24 of these!


Tang Band tweeters:

http://www.partsexpress.com/pe/pshow...number=264-804

Specifications: Power Handling: 70 watts RMS/100 watts max * Voice coil diameter: 1" * Nominal Impedance: 8 ohms * Re: 6.0 ohms * Frequency range: 2,500-25,000 Hz * Fs: 1,700 Hz * SPL: 91 dB 1W/1m * Dimensions: Overall Diameter: 2-3/4" x 2-1/8", Cutout Diameter: 1-15/16", Mounting Depth: 1"

My only concern is cost if I used a bunch of them, best deal I have found is $10 each on Ebay. I do have ten of them.

I believe it would work fine to have two side by side as they are quite small and the flanges would permit having a 2" seperation between the center of the domes, I know, not 1.5" I could stack them or even have four of them if needed to keep up with the mids.

Like this:

M
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M
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or

M
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or

M
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and can add more mids if needed as well, ten per array would be nice, leaves me enough for a center channel

MMTTMM

I have room for this in the center

MMMTTMMM which would be good and at the price I can always order more mids.

Or not even use a center, I have a decent store bought one I could use as well but not going to sound as good as anything I build

If these mids do not play low enough I can make a change and add some midbasses to the array or the bottom of it, whatever is best.

Open to suggestions!

Thanks!

Rick
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Old 16th December 2004, 11:51 PM   #6
RJ is offline RJ  United States
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I just modelled the 10-Vifas they come out to 97 - 98 db.
Those 91 db tweeters are not going to make it.
You'll probably need a Pro Audio type tweeter in the same db range or higher (you can attenuate with a resistor).
The c-t-c of those TB tweeters is too large anyways.
Also, if you port those Vifas to get down to 90 hz. you'll have to buid them in seperate boxes. Tower designs have standing waves anomilies to contend with and woofer loading baffles don't cut it.
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Old 17th December 2004, 01:27 AM   #7
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Something your must consider with line arrays is their affect on dispersion. With the vertical arrays for your mains, you need to be within the plane of the array for listening. Above the topmost or below the bottom driver, the sound is seriously attentuated unless you aren't in the near field, which would defeat the purpose of having an array. You want the woofer array to be as long as practical, so you are in the nearfield at the lowest frequency possible. If you are going to use multiple tweeters, the same thing applies except the far field projection requires a shorter line at the higher frequencies, but you need to be in the array plane at your listen position(s). As a party type speaker or group use for HT where people may be sitting on the floor, you need the tweeter array to be quite long. The simplest solution for me is to use 1 super tweeter with an Lpad to adjust it instead of an array of tweeters, but you must use a tweeter that is 4-6db more efficient that your entire array of woofers so it can keep up at the listening position. Another alternative is to use 5 tweeters in a Bessel array so you get good dispersion and some efficiency gain from multiple drivers.

Because of the serious attentuation past the ends of an array, you can't just turn an array on its side to use as a center channel. 3 options are 1. Go without a center channel. Build your array pair first and listen that way. 2. Use an arc for the baffle to achieve good dispersion left and right. 3. Make the center channel a Bessel array so you get wide dispersion.
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Old 18th December 2004, 01:52 AM   #8
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Thanks guys! The more I learn, the more I learn I don't know!

I have built a few nice but simple systems over the years, little sat sub setups, even with Dynaudio drivers in some large baffel designs, MTM's, etc. This is deffinately more challenging and confusing.

It seems I may of bought a bunch of speakers I can't use that effectively. Maybe I should sell all or most of them and get something easier to work with, hmmmmm, any takers? lol!


I won't have much time to look into this for a couple of weeks so will mostly do a bit more research before making any major decisions.

Thanks again, really appreciate the help!!

Have a great weekend
Rick
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Old 18th December 2004, 06:41 AM   #9
sqlkev is offline sqlkev  United States
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Rick,
I think the most challenging part about ur project is baffle making and cost , especially the tweeters each at $10

to keep the dispersion equal with the mids, you'll need plenty of the tweets
so consider if you were to do 8 mids per side, perhaps 16 of the tweeters will be needed

I'd save the drivers that you have now for another project

Here's what I have for my array,
16 nsb (partsexpress pioneer 4" full range $69cent driver) per side + 32 apexjr tweeters ( apexjr.com, steve sells these tweeters for 50 cent each..just ask)
baffle width is 16" open baffle
very simple xover, i believe it as a single octave HP for the tweeters at 7-8khz

after some time listening to this (a few months now)
I've found it to be a bit fatigue on the midrange possibly due to the cone break up at 6khz or so, but if you can take care of that problem, the $100 project is so very well worth the time spent

I'm planning to do an 8 nsb + some sort of high efficiency tweet ported array soon,
we'll see how that goes
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Old 18th December 2004, 08:21 AM   #10
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Thanks, I have some serious thinking to do right now. This project has to be done soon for my son's senior project and it is getting a bit complicated to say the least, very interesting though

I have a new tweeter to think about as well,

http://www.partsexpress.com/pe/pshow...number=275-035

Alot more money but sure sounds interesting, let me know what you guys think!

Rick
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