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Old 8th March 2009, 06:07 PM   #1
jpetek is offline jpetek  Germany
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Default BIPOLAR Line Array

Hi,

i am planing to build a Bipolar Line Array with 2 or 3" Driver (8 or 16 on each side).

Now my Questions.

1. Did anybody build such a line Array? if yes what was his experience?
2. What is the best wire for the drivers? (combination of seriell/parallel?)
3. what is the best way to regulate the loudness of the backspeaker? (for example with a Fostex R100?)

Thank you for your help.

best regards

Josef
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Old 8th March 2009, 11:01 PM   #2
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I'm thinking you're going to need major Eq for a start due to the severe lobing issues of running FR drivers in a line. That should bring the vanishing HF back up. You may, or may not hear the combing through the upper midrange. Some people do, some don't. Depends on how suseptable you are to such things. The Hass effect does come into play; depending on the design, I can sometimes live with it, TBH, although it's usually better not to run into such issues in the first place.
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Old 9th March 2009, 03:24 AM   #3
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I have to agree, xover design will be a migraine. Then after it's built (migraine #2) you'll have to go back and tune the xo endlessly.


All that being said; your FRBPLA (or Frabpla) proposal interests me to death, and if you do design and build one successfully I'll need you to post your schematics so I can copy it
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Old 9th March 2009, 03:56 AM   #4
JinMTVT is offline JinMTVT  Canada
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c'mon guys...we are in 2009

XOVERS are handleded easily with digital equipment such as Beringher DCX ..and it is not even expensive

so other than work to tune it out,
there is no building migraine here


jpetek: i have no experience with bipolar line array
but may i ask why are you interested in building such a system ?
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Old 9th March 2009, 09:20 AM   #5
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Would that it were as simple as you make out.

The wiring isn't anything per-se to do with an XO, it's more to create a reasonable impedance, and possibly, to assist in power-tapering the line. For e.g., if no power tapering is required / desired, then, if 16 drivers were used, I'd simply divide them into 4 groups of 4 drivers, where the individual units within the groups are wired in series, then simply parallel the 4 groups.

You will need some form of Eq, digital (preferable) or otherwise, to compensate for the problems caused by the output of the driver's lobing, and creating destructive combing. This will start to occur when the centre-to-centre spacing of the drivers exceeds 1 wavelength of the frequencies being reproduced & becomes progressively worse as frequency increases. For example, assuming a 3in c-t-c spacing, then this will be from about 4.5KHz. You can Eq the progressive HF attenuation this causes up, but you can't do much about the severe nulls / roughening of the response. As noted, the Hass effect can negate some of that, but it will rather depend on the design, and also, the way you happen to listen -we all know how some things bother some people more than others, so YMMV as always, but tread with caution.
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Old 9th March 2009, 11:31 AM   #6
Piek is offline Piek  Europe
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Why bipolar? Isn't the major benefit of a line array its directivity and cancellation of room reflections? (Heard one. Have build one for testing) If that bipolar thing is used to gain more "imaging" or whatever you could gain that through a "standard" line array with a matching crossover points and maybe a little EQ. I don't think you need more Energy from "behind", after hearing the "Lightning" from Monacor, there is plenty.... But thats your try.


(I did build a line with 3", you'll need a tweeter line too. Sim it: http://www.pvconsultants.com/audio/radiation/vpr.htm)

-Micha
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Old 9th March 2009, 11:55 PM   #7
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The trouble with active/passive arguments is polarization. The "passive people" usually argue the worst case scenario, and don't always know that the Behringer can do things such as multiple simultaneous EQ. The "active people" tend to not think through the xover in the design, assuming the 'puter will fix it. This can be disappointing, especially when one finds the upgrades necessary for the Behringer to quietly and accurately process a 24/96 data stream.

I don't know anything about line arrays, but it is cool we have all these tools.

As a third option, forget that some sound cards can become the crossover on a computer driven system. I played with this approach several years ago, so I don't know the current state of the art.
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Old 21st March 2009, 09:26 AM   #8
jpetek is offline jpetek  Germany
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Hi,

I decide not to go to a bipolar Linearray.

It is too complicate.

I decide to build a Linearray with 16 NEW Bandor drivern per side.

Doreen from Bandor will build the new type for this project.

I will keep you inform.

best regards

Josef
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Old 21st March 2009, 09:33 AM   #9
jpetek is offline jpetek  Germany
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bye the way for this project I need a fast subwoofer which works till 200 Hz.

Any idea?

regards

Josef
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Old 21st March 2009, 10:03 AM   #10
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I'm thinking you're going to have lobing problems. Still, you might get away with it, on-axis.

Well, you won't get away with a single sub -sound is increasingly directional from about 72Hz upward, so you'll hear sound coming from a different location from that point up to the XO frequency. Twin subs would be mandatory, & you'd probably be better off with woofers rather than subs, which usually don't go higher than 100Hz with much grace. A couple of quick examples would be to take a look at the CSS SDX7s, or if you wanted something larger, some of the Eminence range of drivers (Beta / Gamma 15 etc).
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