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Short Line Array (line source) build
Short Line Array (line source) build
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Old 1st March 2014, 04:00 AM   #21
geraldfryjr is offline geraldfryjr  United States
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If you wired each set of 4 in a 2x2 configuration and then used the two sets with a crossover, Then Yes, It would be an 8 ohm configuration for the system as a whole.

However I would configure the drivers with a WMTMW configuration.
What you have shown is WTM from the bottom up.

jer

Last edited by geraldfryjr; 1st March 2014 at 04:03 AM.
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Old 1st March 2014, 11:40 AM   #22
perceval is online now perceval  Taiwan
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Yes! So I am indeed learning and getting it right!

WWMMTMMWW, that's what I meant, but for the sake of clarity, I just went with that simple design...

Looking at those little 3"... there's not a lot of space from the side of the basket to the outer rim to mount them. A few mm at best! I'll need a precision cut. And the magnet is bigger than the woofer! Strong magnets too!
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Old 1st March 2014, 04:06 PM   #23
GM is offline GM  United States
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I'm wondering if wiring these short arrays in a Bessel alignment might not be better overall, so does anyone know if it's been tried?

GM
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Old 2nd March 2014, 08:45 AM   #24
perceval is online now perceval  Taiwan
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Bessel? Who's he? I guess it's time to hit Google...

In the mean time, how do I design a cabinet for an array?
Most cabinet calculators do so for a single driver... So how do I convert the data into a line source cabinet?
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Old 3rd March 2014, 11:08 AM   #25
perceval is online now perceval  Taiwan
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I am a believer!

So, just for kicks, I took one driver out and listened... meh... kinda sounds like a cheap Radio-Shack-one-speaker radio.

So, wired up all my 8 drivers to a quick open baffle I made (can't believe I got the wiring right on my first try!) and... wow, I'm starting to like it! Now, we are moving into the good stuff!

But, the OB is indeed not working. Too much cancellation and it just doesn't sound right... I can hear I am on the right track, but just not there yet. Also, I don't think I'll need tweeters with those little 3". The highs are there. Will probably need EQing.

So now, my plan is to get another 16 drivers, adding to my 16 I already have, so I will be at a total of 16 for each tower. Wired up in 4x4, it will stay at 8 Ohms. (with 8 drivers I am at 6.4 Ohms now)

Starting to look like a short array?

Been reading around here and I believe each series of 4 drivers will need to be sealed into their own space. My previous question stands. How do I know how much volume I will need for each series of 4? I couldn't find anything yet...

Also, should I go ported or sealed with a short array of 16 drivers?
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Old 3rd March 2014, 01:50 PM   #26
Scottmoose is offline Scottmoose  United Kingdom
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Run them through a free programme like WinISD or similar for the suitable Q -use the pro. version so you can adjust damping in the box since it otherwise assumes acoustic suspension sans damping.

Depends how you're planning to Eq them, but I'd be inclined toward sealed in any case. You don't need separate volumes, but something to break up the longituding standing wave is no bad thing, so solid bracing should do the job nicely.
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Old 3rd March 2014, 03:00 PM   #27
geraldfryjr is offline geraldfryjr  United States
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Winlsd seems to only like a sealed configuration for your driver with the data from the sheet that you posted.
A cabinet volume of 1.5 to 3.0 cubic feet is good.

The program just kicks out the data for a vented alignment and shows no real benefit for a ported system.

In the screenshot that I have included, I have set the power levels for an Xmax of 3mm at 30Hz with a box volume of 2.020 cubic feet.

The power level set for the Blue SPL curve is 3.0 watts for a SPL of 101.16db.

This includes a linkwitz filter as shown that is calculated by the program.
Except, I did change the low frequency setting to 50Hz instead of the normal 20Hz as the drivers excursion just shoots through the roof at 20Hz.

The power level for the Yellow curve is set at 123.4 watts for the same conditions but without the Linkwitz filter for an SPL of 117.458db at 200Hz.

This is only 7.7125watts per driver.

It will be a pretty impressive system with all 32 drivers using only a 50 to 120 watt per channel amplifier!!!

The curves do suggest to use a separate subwoofer with the system.
Although, You may just get all of the sound you will need on a few watts using a linkwitz transform filter.

Cheers!!!

jer
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Last edited by geraldfryjr; 3rd March 2014 at 03:06 PM.
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Old 3rd March 2014, 03:06 PM   #28
GM is offline GM  United States
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Quote:
Originally Posted by perceval View Post
Bessel? Who's he? I guess it's time to hit Google...

In the mean time, how do I design a cabinet for an array?
Most cabinet calculators do so for a single driver... So how do I convert the data into a line source cabinet?
Bessel Array; it's a way to wire up a line array to fool us into perceiving a single point source with the trade-off that efficiency is only whatever a single driver is.

There's also a way to make a line array into a stereo speaker, so I imagine some [all?] of the consumer soundbars are Bessel Arrays: https://www.google.com/search?q=bess...sm=93&ie=UTF-8

For the basic simming of multiple drivers, just increase the Vas spec by the number of drivers required to get the net volume [Vb] and vent design [if desired].

GM
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Old 3rd March 2014, 04:36 PM   #29
perceval is online now perceval  Taiwan
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Thanks GM, I've read a bit about Bessel Array, but I think I'll keep it simple for my first run...

jer, thanks for the calculations, you got me excited. Sounds like good news. I have an older version (alpha, 0.5-something) of Winlsd on my computer, but couldn't get any of that info you showed me.

Learning about the Linkwitz filter as I write. Best way to implement it? MiniDSP, Behringer DEQ2496 or homemade circuit?

I guess I'll need to upgrade my receiver as well, since I do not have pre-outs on my current receiver/amp.
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Old 4th March 2014, 12:02 AM   #30
geraldfryjr is offline geraldfryjr  United States
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Here is the data I used to create the model.
I have also included the file in a ZIP so that you can just add it to your Winlsd drivers folder.

Since Winlsd checks all of the parameter the only one I changed was the Qes by erasing it and letting Winlsd to recalculate it or else it won't let you save the file.

I can't tell how to go about using the digital stuff but implementing the filter with a single dual (or quad) opamp would be by far the cheapest method to use.

I am in the process of designing a preamp and active crossover design for my Desktop ESL system and it requires such a filter.

I am think about implementing the filter with a boost and cut function so that I can adjust the level of low end boost with the overall power level.

The Higher the power level the lower the low end boost will be to keep the high excursions at frequency's lower than 40Hz or 50Hz under control for my 5.25" woofer.

jer
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File Type: zip AES AES 3inch.zip (982 Bytes, 9 views)

Last edited by geraldfryjr; 4th March 2014 at 12:09 AM.
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