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Old 20th August 2010, 04:19 AM   #1
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Default Small Format PA Line Array

I would like to design and build a nice little small format line array for acoustic acts and spoken word applications... So I came up with this design after some research.

The mid driver is a 6
(this one:Dayton PA165-8 6" PA Driver | Parts-Express.com)
which I will take up to 4k

With 2 cheep piezio tweeters
(these 3-1/2" Wide Dispersion Piezo Horn Tweeter Square | Parts-Express.com)

My question(s) are:
Will it produce enough clean SPL for small acoustic acts and spoken word... and maybe a rock band or two in small venues.

I will be using it with 2 of these:
Speakerplans.com

Here's my design:

Imageshack - rig1.jpg
Click the image to open in full size.

Imageshack - rig2.jpg
Click the image to open in full size.

Thanks a lot!!!!
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Old 20th August 2010, 10:28 AM   #2
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Quote:
Originally Posted by Omeone View Post
... So I came up with this design after some research.
Why two TWEETERS per MID? To double sensitivity/output on the high frequency or dispersion? Do you know their output in frequency curve/measured them? Are you going to cross them at 1k5/1k8? And the mid driver, are you going to use it higher than 2K? These are questions you should ask.
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Old 20th August 2010, 02:11 PM   #3
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Hi,

I would ditch this whole line array idea.

First, this line will be too small to control directivity the way true line array does.
Second, your chosen x-over point is way too high. No higher than 2 kHz is advised, ~1 kHz would be better.
Third, for these kind of gigs line array is not needed, a decent point source would be much better (IMO).

Also, your driver choice is poor - two Eminence Alpha6 would be as loud as four of these Daytons and cost roughly the same. Piezos are poor choice, too - been there, done that, went to small bullet tweeter route and not regretting it.

Most importantly, combining 18" bandpass with 6" mids is NOT a good idea - you'll have a huge hole in the 80....150 Hz range, right where the bass energy of acoustic guitar and bass drum is. 12" or even 10" reflex bass modules are way better choice (I for now went double-8" route, though it's stretching it a bit. But I already had the suitable cabs and the drivers (Fane Sovereign 8-225) were cheap.).

My suggestion - something along the lines of this plus this. You can change the tweeter for Eminence APT80, do the mid-tops in MTM configuration and cross around 4 kHz. This would give you roughly 120 dB, which (while not going that low) competes with most of the commercial 10" cabs and even some 12" cabs (like RCF ART310 and FBT Maxx4) and beats them in terms of sound quality.
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Old 20th August 2010, 03:56 PM   #4
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I also vote NO on this one. For your app, there is much better you can do.

Having done many, many years of spoken voice PA, something along the lines of the JBL Eon 10" works great. That's all you need for voice. The Mackie powered speakers, too.
You do not need a 15" for speech. In fact, stay away from it.

The Meyer Sound UPM also works great for speech and it's quite small.

Once you get to live music, it's a different ball game.
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Old 20th August 2010, 08:46 PM   #5
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Hi,

I am guessing that you have either seen or heard about the Renkus Heinz IC Live or the Bose L1. Both work OK in the their intended applications. But they aren't a low cost option. I agree with the others, I don't think that you will be happy with the results of your plans.

If you really want to build a line array there are a number of options. The simplest would be a Bessel array. (Hit Google for array explanation) a 7 element 6 speaker, with a nice horn driver like the BMS 4528 in the 0 position might be an answer. The more up to date answer is the CBT array. There is a thread in this forum with links. Also you could do a clone of the L1 with full range drivers.

Simplest answer, but not the cheapest, is to build a cabinet with a 10 + 1" and use really good drivers and a waveguide.

Good Luck.
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Old 20th August 2010, 09:16 PM   #6
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Ditto above. A 10+ horn will be hard to beat for what you want to do. Not as sexy as a line array, but it works great.
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Old 20th August 2010, 10:20 PM   #7
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Thanks for all the advice... it looks like I'll be going with a 10 and a 1. What do you think about horn loading the 10? Is it more trouble than it's worth?
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Old 21st August 2010, 08:00 AM   #8
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Horn loading the 10" is just unnecessary complication. Hornloaded 10" will have narrower bandwidth, requiring lower x-over point to tweeter (1...1,5 kHz vs. 2...2,5 of direct radiating one) and probably bass support below 200 Hz if any music is to be played through (for pure speech, 200 Hz low limit would be OK), whereas direct radiating 10" can go down to 80 Hz with no problem.
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Old 21st August 2010, 02:35 PM   #9
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Ditto the above. Only horn load the 10 if you are using it as a midrange driver in a much bigger P.A. For your use, no horn.
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Old 21st August 2010, 05:22 PM   #10
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Default coax solution.

Quote:
Originally Posted by Omeone View Post
Thanks for all the advice... it looks like I'll be going with a 10 and a 1. What do you think about horn loading the 10? Is it more trouble than it's worth?
Sorry, should have asked before. What audience size, and physical area do you have to cover. Also music type, band size, and expected spl.

I hope you looked at the Bessel Array and especially the CBT array stuff before making the decision. A university over here is using the CBT + sub for their live acoustic music nights. Those using it have been very pleased with the results. Forget all the complex maths and look at the connection diagram to see how simple it is. Another really simple answer would be, to use a coax unit(cone/compression driver). The BMS units are really good value for money, 8CN552/8C250. Other makes available if the BMS is too expensive, eminence, eg Beta 8CX + your choice of compression driver.


Last edited by applehorn; 21st August 2010 at 05:32 PM.
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