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Line array steering ?
Line array steering ?
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Old 21st February 2019, 04:54 PM   #1
mark100 is offline mark100  United States
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Default Line array steering ?

Hi all,

I'm itching to try a different design from my normal work, which could best be characterized as high quality PA builds.

The floor-the-ceiling line arrays, made to go into room corners, look particularly good to me.

From researching many line array threads, I've seen that the floor and ceiling are supposed to extend the line's length, perhaps theoretically infinitely...
I take this to be a very good thing...

But I also see more and more commercial column designs promoting beem steering such as one just announced by RCF.. Product Detail - RCF

I get that commercial designs are unlikely to be able to match ceiling height and thus take advantage of extending from floor-to-ceiling. So it seems vertical pattern control could be very beneficial then.

My question is: with a normal 8ft or so ceiling, do you see beem steering such as in the RCF being an advantage?
Or does the non-steered, reflection extended line from the floor and ceiling totally suffice? Would the extended line be harmed be steering?

I realize the need for discrete control of all the drivers in the line...I'm just trying to decide if it would be worth the effort to attempt building in steering capability.
(So far, looking at the usual 3 1/2" drivers... Yikes the channels !!)

Thx... mark
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Old 21st February 2019, 05:11 PM   #2
wesayso is offline wesayso  Netherlands
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The Infinite Line Source: analysis thread goes into the theory behind the infinite array approach. The arrays used in PA are not able to use floor/ceiling "mirror images" to virtually lengthen the array.

The CBT from Keele uses the floor and the top end is shaded which could be seen as a steering mechanism. For a finite array this could be a viable option. Shading a floor to ceiling array in a similar way would definitely mess with the floor and ceiling "mirror images". No floor or ceiling is going to be a pure sonic mirror though, so in practice things might actually work out pretty good, I haven't tried it on a straight array.

Personally, I opted to get as close as possible to that infinite line source ideal. Even though my array isn't extending all the way up to the ceiling. About 70% (or more) coverage of the floor to ceiling distance is often considered to be enough to still 'see' the advantages as a general rule of thumb.
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Old 21st February 2019, 05:23 PM   #3
TBTL is offline TBTL  Germany
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Steering in the way RCF does requires many amplifier and DSP channels and modelling that is outside the scope of most DIY guys. It mostly seems to add flexibility, allowing for the vertical coverage pattern to be set to what is needed in a certain venue. I do not think this adds value to a one-off loudspeaker that you design specifically for your home, with prior knowledge about what your home looks like. It can also be used to get even pattern control from a line that otherwise would be too short, which does not apply if a full length floor to ceiling array is an option.

Last edited by TBTL; 21st February 2019 at 05:33 PM.
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Old 21st February 2019, 05:37 PM   #4
mark100 is offline mark100  United States
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Hi Wesayso, and thanks!

Yep, I've read that thread and others about the CBT.
My thoughts match what you say,.... that any steering would have to mess up the "mirror-lines" ....but also then again, who knows how well the floor and ceiling are making the sonic mirrors....

So I'm kinda thinking maybe to build in steering....on a build just under 8ft long for my normal sized room. Just to compare...
I have a room with a tall vaulted ceiling, that I'd also like to try the build in. Thinking steering might be valuable there...

But of course, there's the reality cost of all the necessary channels.......aargh..
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Old 21st February 2019, 05:43 PM   #5
mark100 is offline mark100  United States
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Quote:
Originally Posted by TBTL View Post
Steering in the way RCF does requires many amplifier and DSP channels and modelling that is outside the scope of most DIY guys. It mostly seems to add flexibility, allowing for the vertical coverage pattern to be set to what is needed in a certain venue. I do not think this adds value to a one-off loudspeaker that you design specifically for your home, with prior knowledge about what your home looks like. It can also be used to get even pattern control from a line that otherwise would be too short, which does not apply if a full length floor to ceiling array is an option.
Yep, thx.
I get the amp/DSP implementation demands....I think I'm OK there.
If I was building solely for placement in one room, I don't think I'd even consider it.
But I REALLY like to move gear around, room to room, etc.
I find that is often the best thing I can do to make a system shine...horses for courses so to speak.
And the RCF steering just looks so dang interesting too!
Getting tempted Lol
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Old 21st February 2019, 05:54 PM   #6
wesayso is offline wesayso  Netherlands
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I'd see more value in a very closed space WMTMW (basically what a synergy horn is) and extending that on both sides with a bass array (so on top and bottom), making it sort of an an expanding array that all seems to come from a virtual point source. The bass array would make use of the floor and ceiling and thus avoid the reflections in a vertical plane, the horn avoids the rest trough it's pattern control.

Or something like the paraline array from Danley which still mimics that point source ideal by bending the resulting wave shape with it's lenses.
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Last edited by wesayso; 21st February 2019 at 05:56 PM.
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Old 21st February 2019, 08:14 PM   #7
mark100 is offline mark100  United States
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Originally Posted by wesayso View Post
I'd see more value in a very closed space WMTMW (basically what a synergy horn is) and extending that on both sides with a bass array (so on top and bottom), making it sort of an an expanding array that all seems to come from a virtual point source. The bass array would make use of the floor and ceiling and thus avoid the reflections in a vertical plane, the horn avoids the rest trough it's pattern control.

Or something like the paraline array from Danley which still mimics that point source ideal by bending the resulting wave shape with it's lenses.
Yeah, the synergies really do make sense.
But I kinda feel I have very close to a synergy already, with a build that has a coaxial CD mounted in between horn loaded mids (the Peter Morris boxes)
I don't have any desire to get bass above and below .... I honestly don't think there is any sense in trying to direct bass (100Hz sub xover).
I'm happy just keeping the floor sub within 100Hz 1/4 WL, of main speaker.

I sense a synergy project would be more lateral in nature to my existing speakers, and am thinking a line-array would be spankin new territory ...
Paraline is too much acoustic plumbing I think....

So studying drivers right now...ye ole TC9FD looks like a good benchmark
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Old 21st February 2019, 08:58 PM   #8
wesayso is offline wesayso  Netherlands
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If you're planning to use sub support anyway, you could go for smaller drivers, like the SB Acoustics SB65WBAC25-4, just more of them as they would give you closer spacing in a straight line than the 3.5" drivers. They look cute in person! But they are also quite impressive drivers!

I'd still stick to keeping floor to ceiling a line array to behave as a line source, as opposed to using beem steering with it. I'd only use that principle with finite arrays.
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Old 21st February 2019, 10:54 PM   #9
wesayso is offline wesayso  Netherlands
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By the way, my suggestion for bass array was to avoid the usual floor reflection dip (usually happens well above 100 Hz), not trying to direct bass.
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Old 21st February 2019, 11:46 PM   #10
mark100 is offline mark100  United States
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Originally Posted by wesayso View Post
If you're planning to use sub support anyway, you could go for smaller drivers, like the SB Acoustics SB65WBAC25-4, just more of them as they would give you closer spacing in a straight line than the 3.5" drivers. They look cute in person! But they are also quite impressive drivers!

I'd still stick to keeping floor to ceiling a line array to behave as a line source, as opposed to using beem steering with it. I'd only use that principle with finite arrays.
Looks like a very nice driver !
I'd like to keep driver cost down on building a "first try" experimental column.
So driver cost is a constraint, and fewer drivers are better.
The other constraint is, if I continue with the goal of beam steering, I currently have at most 24 channels of amp & dsp using the same platform. So ideally 24 drivers max (for one speaker)
But 24 drivers doesn't get me near 8ft tall with any drivers I've found, that are both affordable for an experiment, and have good VHF response.
I figure I can group drivers at the array center to overcome the 24 driver constraint and still beam steer, but still, more complication....

My gut says all arrays are finite, floor and ceiling mirrors or not,...hope my gut gets proven wrong !! Really hope... Wouldn't mind beam steering to be totally worthless for floor-to-ceiling.
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