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Floor-to-ceiling array vs CBT
Floor-to-ceiling array vs CBT
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Old 13th October 2013, 04:48 PM   #21
Juhazi is offline Juhazi  Finland
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This is perhaps the best story with measurements of a line array go to kimmosto's diy archive and select KS-160-21

Keele's origila paper can be found at www.audioartistry.com and here we see that shading is important
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Old 13th October 2013, 07:49 PM   #22
jeno is offline jeno  Norway
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Thanks!

This is interesting:

KS-160-21_FR_250x100-118cm_0deg_R_.png

Both this and Keele's simulations are only on finite arrays.
Still wonder if this apply on a full floor to ceiling array.
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Old 14th October 2013, 08:40 AM   #23
Juhazi is offline Juhazi  Finland
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Lines need shading delay on curve to sum well, we can see that Kommosto's straight line with no delays exhibits bad vertical lobing with very small offset. His xo was 3300, way too high!
I don't think long fullrange lines suit homes at all unless
- they are curved or straight with delays
- they use fullranges or coaxial 2-way drivers to prevent horizontal lobing

A curved or delayed line has very strong directivity sideways because of it creates
cancellations. Radiation pattern must be like a dipole without back radiation.
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Old 14th October 2013, 09:14 AM   #24
Juhazi is offline Juhazi  Finland
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Ooops, I meant this

Lines need shading delay or curve to sum well

Kimmosto's line is 200cm high and rooms here at 250-260cm. I think it works as infinite line in a room. He doesn't show horizontals but says that there is bad lobing. Overall they were really good speakers, but didn't deliver the bass mode control that he wanted
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Last edited by Juhazi; 14th October 2013 at 09:19 AM.
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Old 14th October 2013, 10:17 AM   #25
wesayso is offline wesayso  Netherlands
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That particular array (KS-160-21) has a tweeter line that is not floor to ceiling in length. The tweeter line isn't anywhere near 200 cm.

I've read a lot of material on line arrays and most boil down to this:
Floor to ceiling line array: not advised to use shading.
Shorter array: shading is needed.

A lot can be found on this forum, look for posts by "speaker dave" among others:
Constant Beam Width Transducers line arrays

So I don't really agree with this without further information:

Quote:
Originally Posted by Juhazi View Post
Lines need shading delay or curve to sum well

Kimmosto's line is 200cm high and rooms here at 250-260cm. I think it works as infinite line in a room. He doesn't show horizontals but says that there is bad lobing. Overall they were really good speakers, but didn't deliver the bass mode control that he wanted
By the way, don't show Keele's papers as that piece of information because he uses the mirror floor image to enhance the CBT performance but in the straight line example there's no mention of either the floor or ceiling mirror effect.

The strangest design choice of the CBT to me is that it mimics a point source that is coming from the floor level. I've been told it does not sound that way but to be sure I'd consider hanging it from the ceiling, or better yet, do what Geddes once said and put it on it's side and hang it in the corners:
http://www.diyaudio.com/forums/multi...ml#post3411297

Last edited by wesayso; 14th October 2013 at 10:34 AM.
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Old 14th October 2013, 01:57 PM   #26
Overkill Audio is offline Overkill Audio  United Kingdom
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Default Good research

Hi all,
I found the original Line Array papers, very helpful.
Cheers
Derek.
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File Type: pdf Line Arrays Part1 (1).pdf (193.6 KB, 125 views)
File Type: pdf Line Arrays Part2.pdf (194.8 KB, 55 views)
File Type: pdf Line Arrays Part3.pdf (185.0 KB, 53 views)
File Type: pdf Line Arrays Part4.pdf (158.3 KB, 58 views)
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Old 14th October 2013, 02:32 PM   #27
Overkill Audio is offline Overkill Audio  United Kingdom
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Default New driver.... New rules?

I am still experimenting with full range driver single column arrays (as well as twin and triple column ) and finding that one over riding factor counts more than any other.

When using full range drivers the power response is crucial ie A very even on and off axis response out to plus minus 90 degrees is the key.

Using a version of the 4.5 inch Neo magnet BMR driver I have been getting great results, esp when used in very shallow curved wall cabinets which can hang on the wall. ( See pics)

Also the min height is interesting....It is less important than driver choice for sure. But the 1.6m tall ( 8 driver version) sounded identical in terms of imaging, 3D accuracy, texture, detail etc Vs the 1.8m tall ( 16 driver version) , but the 16 driver version could go louder with lower distortion and was more sensitive....
All simply a function of more Sd... Double the surface area of cone moving and you half the distance it needs to move for a given SPL / distortion.

Even increasing the driver to driver centre spacing has no audible in room effects ( slight measurable differences) ie 112mm tight spacing Vs 210mm spacing with the dome array's.

The bottom line is that the unique ability of the BMR to sound and measure within a couple of Db from on axis to plus / minus 80 to 90 degrees ( giving almost perfect 160 to 180 degree coverage when wall mounted) is changing the way domestic line arrays can perform in real world rooms.

Still learning and experimenting but the sonic results are so good I am now in the strange position that I will have designed something that sounds better than anything else I have ever built and yet I don't fully understand exactly how it works...!!

Cheers
Derek.
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File Type: jpg Christmas Eve 2012 ..Hogworts! 096.jpg (291.5 KB, 519 views)
File Type: jpg Christmas Eve 2012 ..Hogworts! 103.jpg (538.7 KB, 519 views)
File Type: jpg LA16 unfinished 12 03 13 004.jpg (660.4 KB, 516 views)
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Old 14th October 2013, 03:31 PM   #28
wesayso is offline wesayso  Netherlands
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Derek,

Have you ever tried a Beveridge like setup with the arrays on the long wall facing each other?
Floor-to-ceiling array vs CBT-1258338370-jpg
Source of picture: http://cgim.audiogon.com/cgi-bin/vs....tem&19&showall
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Last edited by wesayso; 14th October 2013 at 03:34 PM.
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Old 14th October 2013, 04:08 PM   #29
Juhazi is offline Juhazi  Finland
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That old thread is superb! I have no experience of them, but the basic principle is interesting. They are definitly not the holy grail answer to everything, like advertized.
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Old 14th October 2013, 08:04 PM   #30
Overkill Audio is offline Overkill Audio  United Kingdom
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Default Beverage

Hi wesayso,

Not really , I have one pair of on wall arrays either side of the fire place which I use for two channel music, they fire across the short ( 4.5 meter width) dimension of the room.

Also have 2 more pairs in the same room for the home cinema set up, firing up and down the 5.5m length of the room.
I have had several folks comment that music still sounds great 90 degrees of axis ie on the home cinema sofa, and also guys on the two channel sofa still get a fab home cinema sound...
Don't think its Beverage related just very broad and even off axis coverage.
Cheers
D.
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