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Line array steering ?
Line array steering ?
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Old 22nd February 2019, 08:56 AM   #11
wesayso is online now wesayso  Netherlands
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Without the perfect environment, how would one now? And what is that perfect environment?

At least floor reflections are real (as far as I've seen them), just carry your favourite 3 way into the room and measure. Straight arrays are overly sensitive to parallel planes/ridges etc. to the array. Even if you tuck it away in a corner, there's still the transition from baffle to the wall to deal with.
Be sure to do everything you can to fight diffraction in your design or that may lead you to wrong conclusions.

It's not going to be easy... A CBT would be less sensitive to these parallel planes, as the driver distances vary in two planes. But I wouldn't do one extended all the way to the ceiling. Bend it the other way and it will give you a focussed array with it's own set of drawbacks, except in it's sweet spot.

I'd give up the cost for 22 of the 24 channels of amplification and go for the smaller drivers.

From all my experiments so far, getting the speaker to work together with the room is the way to more pleasing sound.
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Last edited by wesayso; 22nd February 2019 at 08:58 AM.
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Old 22nd February 2019, 09:42 AM   #12
wilbur-x is offline wilbur-x  Tibet
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Our experience is that every type of arrays got it's own strengts and drawbacks. We have built vertikal unshaded arrays, vertikal shaded arrays, CBT and focussed arrays. Differences are easily detected. Best image, pinpoint and dynamics goes to the focussed array, in the sweet spot of course. CBT give mostly rich and even sound all over the room, but with less pinpointing. Vertikal unshaded array offer good dynamics and vertical dispersion with pinpointing helped by HAAS-effect, but with somewhat bigger than life image. Vertikal shaded array is a good compromise IMHO when it comes to vocal and acoustic jazz etc. as the sound do not swell that much (less delays from ceilings etc). We did our observations in a normal living room without any acoustical treatments.
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Old 22nd February 2019, 09:54 AM   #13
TNT is offline TNT  Sweden
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This is my "cheap" build. Maybe 350USD for the pair. I love them and I will seriously consider a more elaborate build once my living location for the future is settled. Prepare for EQ and quite some power at hand. Also, prepare for a bass "null" in the place where you would like to sit - I don't know if this is mandatory but I have a hunch it might be considering the involved geometry.

My FR10HM corner-ceiling-floor-array

Click the image to open in full size.
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Old 22nd February 2019, 10:23 AM   #14
wesayso is online now wesayso  Netherlands
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Quote:
Originally Posted by wilbur-x View Post
Our experience is that every type of arrays got it's own strengts and drawbacks. We have built vertikal unshaded arrays, vertikal shaded arrays, CBT and focussed arrays. Differences are easily detected. Best image, pinpoint and dynamics goes to the focussed array, in the sweet spot of course. CBT give mostly rich and even sound all over the room, but with less pinpointing. Vertikal unshaded array offer good dynamics and vertical dispersion with pinpointing helped by HAAS-effect, but with somewhat bigger than life image. Vertikal shaded array is a good compromise IMHO when it comes to vocal and acoustic jazz etc. as the sound do not swell that much (less delays from ceilings etc). We did our observations in a normal living room without any acoustical treatments.
Well, this is exactly the reason I mentioned the room and it's influence to Mark in my reply. I have straight unshaded arrays but no larger than life image. As I've said on my thread: the FIR filtering alone "shrunk" or "tamed" my arrays. And that was a few days in on starting with FIR filtering. I continued to test and observe frequency dependent shading schemes and cooked up a recipe that worked for me in my room.

And I bet one could do the same/something similar with the CBT too! I don't have an untreated room as even before getting into this project I had the plans to get rid of all early reflections without turning my living room into a studio .

So I don't much like the generalisations even when based on actual builds, without looking what caused this. Get the data at the listening spot, analyse that data and act upon it. Instead of building lord knows how many speakers I have decided to stick to one concept and optimise it (and it's environment).

You could do that with almost any sort of speaker. But there are many variables at play here and one cannot ignore any one of those and draw conclusions from it.

Look at the graphs, listen to it, change one thing and do it again. Over and over again .
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Old 22nd February 2019, 10:54 AM   #15
wilbur-x is offline wilbur-x  Tibet
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Yes, you can achieve your favourite soundscape by those measurements. My point is that each basic design got its own identity (in nude).
Non-diy'ers buying their line array without the necessary knowledge, room or equipment should be aware of this.
I will even build more speakers, but different ;-)

Last edited by wilbur-x; 22nd February 2019 at 11:17 AM.
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Old 22nd February 2019, 02:12 PM   #16
mark100 is offline mark100  United States
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Thanks guys,

I totally get the role of the room, and resonate strongly with all comments regarding its overarching role.
Maybe a little background will help explain my line array design goals, and why I'm not trying to build to a particular room.
I've been fortunate to have been able to optimize several rooms acoustically over the years ...rooms where audio was the first priority...no WAF allowed Lol..
Anyway, I could go into the lengths i took, but for brevity just let me say I absolutely understand the value of optimizing room acoustics. Often more important than a whole lot of speaker work we do imho.
But the best room I ever hear....is no room...outdoors. I simply love a good powerful rig set up outdoors. It makes whatever I do indoors sound so poor in comparison, I refuse to tune to a room any longer.
Plus I don't like a 'listening spot' anymore...I move around and dance...with the ladies
i like to listen from adjacent rooms etc...
Too many years sitting with my head in a vise in front of electrostats i guess..

So bottom line...I want a flexible line....array that is
Hence the desire to play with steering...

Ron, I hear you preferring the smaller drivers in lieu of dsp/amps.
But the thing is, I already have the dsp/amps...the driver cost really comes down to the marginal cost to try this...and I'm looking more to experiment than trying to build a new main system.
The TC9FD and PS-95-8 are my current front runners unless advised elsewhere...
I say i already have amps, but that's not entirely true. I have 16 identical channels of 1150W, and another 8 channels of 600W or greater from a kludge of different amps. And they are used elsewhere.
If the line steering pans out as desirable, I'll want to replace all of them with some low wattage, inexpensive stuff. Recommendations will be needed..

TNT, looks nicely done on budget! What do you mean by bass null where you sit?

Wilbur-x, thx again, exactly the kind of info hoping for.
What do you mean by focused array? Or rather, how does focused differ from shaded? If shaded means amplitude varies, and focused means time varies, I think I get it. Otherwise, I'm not understanding...
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Old 22nd February 2019, 02:32 PM   #17
TNT is offline TNT  Sweden
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Bass disappears :-/ - one meter to any side and it's dandy. But I think i will put a smaller side-table there and have listening seats on each side.

//
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Old 22nd February 2019, 04:38 PM   #18
wesayso is online now wesayso  Netherlands
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Mark, I think steering could make sense if you don't want to adjust the space to the speakers. A focused array would have all drivers equal distance to one listening position.
Think of an arc shape with the center point at your ear as a passive example. With steering you could mimic that with delay and possibly SPL manipulation although it wouldn't be exactly the same.
The straight array could also mimic the CBT with shading and delay as those JBL CBT line arrays do.
Possibly the truly arched CBT arrays would be most independent from the room they are in.
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Old 22nd February 2019, 04:39 PM   #19
wesayso is online now wesayso  Netherlands
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Quote:
Originally Posted by TNT View Post
Bass disappears :-/ - one meter to any side and it's dandy. But I think i will put a smaller side-table there and have listening seats on each side.

//
Got any measurements of that? It is a pretty symmetrical room, right?
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Old 22nd February 2019, 07:24 PM   #20
Jim Griffin is offline Jim Griffin  United States
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Let me add a few thoughts on my listening to the Modified CBT24s that I completed in early 2018. After building and listening to straight line near field arrays for years, the CBTs yield a sound in my room that is more uniform and consistent throughout the room. My living room is 23 feet wide by 32 feet long with a ceiling height that extends to an apex of 18 feet across the center of the room. Thus we are talking a large/tall room that would be an echo chamber for a point source loudspeaker.

My arrays are just over 5 feet high and they benefit from the mirror image from the floor (ground plane). The SB Acoustics SB65WBAC25-4 drivers (about 2.5" square) is the driver used in my build.

CBT Godfather Don Keele's comments about the coverage of a CBT : "Constant beamwidth, constant directivity, constant coverage, constant radiated power."

I'm hearing the same sound in my listening room with my CBTs. Your CBT creates a 'sweet room' effect versus just a 'sweet spot'.

My project is detailed in this thread:

My New Line Array--It's a Modified CBT24

If the original poster wishes to have great sound all over his room, then a CBT is superior. His steered array idea sounds like a complex local science fair project.

Jim

Last edited by Jim Griffin; 22nd February 2019 at 07:35 PM.
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