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Old 29th September 2013, 07:01 PM   #1
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Default simple and low cost line array

i will first mention about some limitations/requirements as i still have doubts if a line array is what i am looking for!!
* the room size is 15 ft x 20 ft
* max height of speaker boxes allowed is 5 ft (due to space and aesthetic reasons)
* speaker boxes would be separated by around 6 ft
* listening distance of 10 ft
* want to avoid subwoofer unless its absolutely necessary (target low freq. is 40hz)
* in local market i have access to 4" mids to 6/6.5" woofers and couple of low Fs (<1000hz) dome tweeters (make Peerless India).
* sealed compact box (if it makes sense!)
* active xover/bi-amping will be used

i am interested to build something similar to 'The ART Line Arrays' in below link
[ lonestar2 ]

questions:
* is height of less than 5 ft and room size suitable for line array speakers?
* what would be the ideal size and number of drivers per channel? or what factors decide size and number of drivers?
* how much low i can expect the drivers to go (for chosen size and number of drivers) in a properly designed sealed box (how to calculate?)
* power amp requirements
* how to calculate combined SPL of the array?
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Old 30th September 2013, 03:11 AM   #2
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Combined SPL is difficult to predict, high frequencies do not couple as low frequencies. I'd expect total sensitivity to be equal to one of tweeters that you choose, because you'll need to equalize raising bass to match tweeters.
Here is an example of that problem.
Parts Express: Project Showcase
His solution was to raise high frequencies, which I think was not a very good idea.
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Old 30th September 2013, 04:31 AM   #3
ScottG is offline ScottG  United States
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Quote:
Originally Posted by soundnovice View Post

questions:
* is height of less than 5 ft and room size suitable for line array speakers?
No.


The designer is Fred Thompson or FredT on the Partsexpress forum:

ART.com line array



It's a similar design to the old Zalytron "arrays".


Here is the "real deal" on Line arrays:

http://www.diy-audio.narod.ru/litr/nflawp.pdf


Note: you can make an array, but past a certain distance it won't behave as a line source. Fig. 5, page 8 - has a table "calculation".


..this causes all sorts of problems with a design like Fred's where you have a point-source tweeter vs. a modest line-source for a certain distance. Basically you have to design for the distance you listen at for the crossover work, otherwise you'll end up with a depressed treble region (because of the pressure loss of the tweeter when compared to the mid-bass array).
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Last edited by ScottG; 30th September 2013 at 04:49 AM.
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Old 30th September 2013, 08:35 AM   #4
Juhazi is offline Juhazi  Finland
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Hello,
my suggestion is that you could use Zaph's ZA5 MMTMM consept as guideline. It might be difficult to make large enough box for more that 4 4-6,5" woofers. Perhaps it would be wise to make a sealed box and use eq to make bass lift.
Click the image to open in full size.
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Old 30th September 2013, 08:58 AM   #5
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sealed box is what i am interested as it will be small in size (one of the important requirement due to aesthetic reasons). since i am equipped with miniDSP, EQing will be preferred method for me to enhance low end.
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Old 30th September 2013, 07:05 PM   #6
ScottG is offline ScottG  United States
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Quote:
Originally Posted by soundnovice View Post
sealed box is what i am interested as it will be small in size (one of the important requirement due to aesthetic reasons). since i am equipped with miniDSP, EQing will be preferred method for me to enhance low end.

With the mini-dsp the array problem (distance/spl) can be compensated for..

-with that in mind, the project gets the
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Old 1st October 2013, 01:58 AM   #7
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I second the motion for an MMTMM or MTMMM over a hybrid line array with the constraints you mention. Four 6.5" woofer would easily get you to your 40hz goal with available DSP but still give you sifficient dynamics and matched efficiency to most domes.

The more I think about it, a 2.5 way with the MTM MM format would be easier to accomplish with the small sealed enclosure constraints.....the bottom two with passive inductance in the 400 hz range fills in the bottom and reduces the need for BSC.

Last edited by mayhem13; 1st October 2013 at 02:00 AM.
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Old 1st October 2013, 04:36 AM   #8
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Quote:
Originally Posted by ScottG View Post
With the mini-dsp the array problem (distance/spl) can be compensated for..

-with that in mind, the project gets the
good to know there is hope!
how can it be achieved? by boosting tweeter SPL compared to bass-array?
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Old 1st October 2013, 04:57 AM   #9
ScottG is offline ScottG  United States
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Quote:
Originally Posted by soundnovice View Post
good to know there is hope!
how can it be achieved? by boosting tweeter SPL compared to bass-array?
-just measure at the listening position and formulate your crossover (with eq.) from that position.

Note that at greater distances we tend to expect a down-ward tilting response (perhaps -3db loss over the passband of 80 Hz to 20 kHz - i.e. not a lot), so a flat response at the listening position of 10 feet probably isn't ideal. "Play" with your crossover until you get something that sounds right.
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Last edited by ScottG; 1st October 2013 at 05:03 AM.
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Old 1st October 2013, 08:10 AM   #10
Juhazi is offline Juhazi  Finland
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If this was my project..
I might would also copy Joe Rasmussen's Elsinore a little. A waveguide -assisted Vifa XT25G-60 and 4 5" very linear midwoofers (like Peerless HDS). 2 of them making MTM and two in .5 boosting low end in a narrow closed cabinet. xo LR2 acoustic. .5 done passively -a minidsp 2x4 and four amplifier channels would be enough for a pair!

5" and waveguide make excellent combination when we consider horizontal directivity. mtm/Line of woofers takes care of vertical directivity.

Here are my measurements of my 5"+wg tweeter speaker Amphion Helium2
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File Type: jpg Amphion Helium2-horz.jpg (143.0 KB, 122 views)
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