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Old 20th July 2012, 02:35 PM   #11
18Hurts is offline 18Hurts  United States
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I want to live in theory--everything works there!

Lessons learned by messing around with these funky speakers. They do work in theory the problem is I'd didn't know all the theories! On paper, you stack up 48 tweeters at 90 to 93dB at one watt each--they should be very loud. Compare them against 12 five inch woofers at 85dB at one watt and I was expecting a massive treble response. That did not happen. I had bass response, the mids were falling fast and I had weak treble.

Used the Aurasound 3" full ranges for mids--crossed them at 375Hz and 6K stacked 20 high and ran them at 13 ohms. Their over 10dB rise in output as the frequency went up was tilted down by the phase interference. Cranked the tweeter lines up by running them at 5.6 ohms at 6K and used a bessel filter to throw a mild bump there since the mids were starting to roll of over 5K.

My measurements indicate a +/- 3dB window from 200 to 12KHz at 1.8 meters mic distance. I was not concerned about bass since they couple and I was in a garage and all is well--in theory. A tapped horn will be built soon to shore up the 70Hz and under point so no worries.

Fired them up and the theory train derailed when operating on the reality tracks. My bass response had a thin sound--it was there but at over 3 meters away--it did not sound as full or loud as it did at 1.8 meters away. Threw a quick and nasty sub together and ran it at 80Hz on down...my sub bass was fine but the midbass was thin. I could smell a formula I missed, it was acting very predictable.

It was the critical distance between near field and far field that depends on frequency. The height of my peaked roof in the garage is 4 meters and the arrays are 1.8 meters tall--my bass was rolling off as a point source below around 600 Hz at my over 3 meter listening position. The passive solution was to increase the woofer line height to 3 meters tall or install a ceiling at 2.5 meters so the line height would be over 70% of the ceiling height.

Reality steps in (also known as my wife) the above options would not happen so it is time for EQ adjustments. Flip the loudness control on, adjust the 100Hz bass knob a touch....screw around with the subwoofer controls and I'm close. Since the tapped horn sub build will require a delay, it would be much easier to fix it with parametric EQ and DSP.

My buddy who is a studio sound guy summed it up this way "Line arrays are great speakers as long as you can fix the treble, mid range and bass response oddities". The science fair experiment will continue in the fall when the tapped horn is complete--we will haul them to the local church and power them with a Crown amp that has the dbx driverack to play with. Testing will be as a pair and stacked in a vertical mono stack. The studio guy loves the nearfield sound of them--I told him to get the CBT from Don Keele if he wants nearfield listening in his studio. The column line arrays are
party speakers for the garage after all.
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Old 21st July 2012, 01:57 AM   #12
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It's hard to say what really is going on there without posted data on individual drivers and summed up response. Perhaps I just didn't look hard enough in your threads.
I've build a number of straight arrays, heard curved arrays and waiting to hear CBT. Like any type of a loudspeaker out there, array can sound great or horrible. It depends on the design.
One of the unique advantages of line array is the stability of the vertical image and perhaps artificial recreation of a life size virtual image.
I certainly disagree that column arrays are Party Speakers only. If you are anywhere near Brooklyn NY, come by to next NY-DIY show/competition. There will be couple of arrays playing.
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Old 21st July 2012, 02:24 AM   #13
18Hurts is offline 18Hurts  United States
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I agree with you R

I originally built them for the garage, mainly to not reflect off the floor/ceiling since it has metal walls. They have that huge sound I love from large speakers and the small variation in volume is great for working in the garage--no getting blasted by output when getting close to them while working on things.

All I'm saying is vertical line arrays have issues--once you are familiar with all the things they do and why they do it--then proceed if the downsides are less than the upsides. In my case, they have a few downsides but the juice was worth the squeeze.

To limit the issue I'm having, the bass output rolls off with distance--make them as tall as possible. The array should get close to the ceiling so the bass reflects from the floor and ceiling junction "making the line array 3 times longer". That detail is something I can't perform in my garage unless I put in a suspended ceiling. The easy way is to put them in the 8 foot ceilings of my house--until my wife spots them then banishes them back to the garage.

One day I'll drag the things into the house and do some listening tests in a proper room, metal and concrete in the garage is acoustic hell. For now, I just tweak the receiver to get it close enough.
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