Inspired by this...
"Dipol 08" Baffle Dimension and List of Crossover Parts
I decided to do my own open baffle golomb line array.
A lot of testing with previous prototypes showed that I want a narrow but long/high open baffle line array without any power or frequency tapering.
I decided to try eight units per side.
Perhaps the following will help somebody struggling with the application of the golomb ruler to such a so called sparse line array.
I found some statements that it is impossible to apply the ruler to a bigger number of speakers assuming that the base unit of the ruler needs to be the speakers vertical dimension.
So a 8 speaker golomb line array made of 10cm speakers will have a total height of 340cm because an order 8 golomb rulers length is 34.
Golomb ruler - Wikipedia
But this is a too narrow interpretation of the Golomb ruler.
Golomb rulers help to get an optimal distribution of units over a given length e.g. where you do not have enough units to cover the entire length (sparse line array).
"Optimal" means that the DISTANCE between ANY two units in the array is UNIQUE.
It is all about the distances not the values or the ruler
distributed.net: Project OGR
The 8 unit golomb rulers values are
0 1 4 9 15 22 32 34
which is written as distances
1 - 3 - 5 - 6 - 7 - 10 - 2 (= 34)
The room height is 250 cm
I wanted a line array that is at least 70% of the height and decided to make the array 180 cm high.
The speakers vertical dimension is 12cm x 8 speakers = 96cm covered by the speakers.
So there are 84cm left of my baffle
Divided spare room by the ruler length of 34 = 2.5cm
This "base unit" is multiplied with the golomb distances between the units,
e.g. from 0 to 1 = 1 * 2.5, from 1 to 4 = 3 * 2.5, etc.
Finally added arbitrarily 4 cm on top and bottom of the baffle just to have something to fix the thing somewhere.
The center of the array is at listening height.
I attached the DSP settings and measurements at different distances and heigths
They show that the speakers melt nicely together at about 350cm distance which is my listening position.
"Dipol 08" Baffle Dimension and List of Crossover Parts
I decided to do my own open baffle golomb line array.
A lot of testing with previous prototypes showed that I want a narrow but long/high open baffle line array without any power or frequency tapering.
I decided to try eight units per side.
Perhaps the following will help somebody struggling with the application of the golomb ruler to such a so called sparse line array.
I found some statements that it is impossible to apply the ruler to a bigger number of speakers assuming that the base unit of the ruler needs to be the speakers vertical dimension.
So a 8 speaker golomb line array made of 10cm speakers will have a total height of 340cm because an order 8 golomb rulers length is 34.
Golomb ruler - Wikipedia
But this is a too narrow interpretation of the Golomb ruler.
Golomb rulers help to get an optimal distribution of units over a given length e.g. where you do not have enough units to cover the entire length (sparse line array).
"Optimal" means that the DISTANCE between ANY two units in the array is UNIQUE.
It is all about the distances not the values or the ruler
distributed.net: Project OGR
The 8 unit golomb rulers values are
0 1 4 9 15 22 32 34
which is written as distances
1 - 3 - 5 - 6 - 7 - 10 - 2 (= 34)
The room height is 250 cm
I wanted a line array that is at least 70% of the height and decided to make the array 180 cm high.
The speakers vertical dimension is 12cm x 8 speakers = 96cm covered by the speakers.
So there are 84cm left of my baffle
Divided spare room by the ruler length of 34 = 2.5cm
This "base unit" is multiplied with the golomb distances between the units,
e.g. from 0 to 1 = 1 * 2.5, from 1 to 4 = 3 * 2.5, etc.
Finally added arbitrarily 4 cm on top and bottom of the baffle just to have something to fix the thing somewhere.
The center of the array is at listening height.
I attached the DSP settings and measurements at different distances and heigths
They show that the speakers melt nicely together at about 350cm distance which is my listening position.
Attachments
This So gehts: Line-Array dimensionieren - Visaton Diskussionsforum and this Dipol-08 Dipol 08 Impressionen inspired me to try it on my own so I made a prototype with 6 small Monacor speakers and an array length of only 140 cm.
Measurements looked promising and I found that a really high but narrow open baffle line array suits my listening needs and room. Ususally this would require a huge number of small drivers if placed tightly edge-to-edge as most line array enthusiasts recommend. But Golomb rulers gave me the chance to fill the space from floor to ceiling with only a few speakers. So less cost and effort.
In contrast to Dipol-08 I didn't use any frequency or power shading. In my opinion this somewhat kills the line array experience. I even tried an additional tweeter for very high frequencies but with the same result.
So all speakers play exactly the same and the main DSP is a huge notch filter at about 2.1Khz. All the rest might be a result of my not so clever speaker choice - more on this later.
However, I cannot answer your question on the golomb advantages fully qualified because this would require an exact comparision of a golomb line array setup with a fully filled line array with of the same baffle size and speakers.
In only found positive tests and applications of Golomb rulers in the radio and astronomy field but for speakers only simulations except Dipol-08 of course. But perhaps somebody knows a better source than my very simple ATB-PC measurements in my living/listening room.
On the speaker choice I will write as soon as I find some time.
In fact these are no diffusors but two wall lights made of multiple small flat stones so that the light shines trough the open edges and also the back illuminates the wall
I do not know if they have any effect on sound. I know the walls could tolerate some sound optimization but I like plain clear walls.
Overall the listening room is a mess. There is a huge panorama window on the left reflecting sound as hell but I cannot use curtains because of an amazing view.
To the right the room opens to the dining room and kitchen so left and right are completely different which makes a good stereo reproduction difficult. Perhaps this is a reason that the line arrays work better here compared to single sources.
Narrow baffle, 8 drivers, very interesting! I always wanted to try a line array, but the need for some 40 speakers steered me away from the plan. 16 is a much more sensible number and I can already see myself buying a bunch of cheap FR speakers like this one: YDT613-8SX030 - bsacoustic.com - the larger Delco speaker I bought some time ago measures very well, so there should be fine as well according to the FR graph.
I've chosen the SL 713
SL 713 - 4 Ohm | Visaton
because
+ it allows an about 1cm narrower baffle but still makes some SD and of course the high Qts but the 0.9 of the Vifa are also okay for open baffle
+ it had been already used/tested in a line array project
GRAND ORGUE | Visaton
+ and it has a nice high frequency behaviour at least in the plot of the manufacturer
+ and I got it for only 10 Euros per piece
------ I like the result, but here are some downsights I experienced
Somebody wrote in a forum and thread I cannot remember that if a chassis shows some flaws and you put it in a line array you will get the sh*t back ten times, and that really need to be considered.
The SL breaks in a bit around 4Khz I think because of the vertical beaming of this chassis around this frequency. Also this is close after the first dipole peak so we need a compensation here. And the little dip
But around 5.5Khz the SL713 shows a peak in the plot that turns out to be a really heavy peak in the open baffle. I think this is result of resonance / trapped air between cone and basket, a thing that all small cone speaker show more or less when used in open baffles.
So now we got a dip at 4Khz directly followed by a peak at 5.5Khz which isn't a nice thing to compensate resp. that requires some considerable DSP
Perhaps a more sophisticated and expensive driver will be easier to handle here.
Overall, do not use a too cheap driver in a line array.
The Golomb thing gives the chance to save some money because of the lesser number of drivers that can be put in better ones.
Thank you for your feedback Elnag, much appreciated!
You just fuelled my curiosity to look further into the colomb ruler concept.
3FE22s on sale here. They have 26 units in stock. Not enough for a full line array, but perfect for this. With the help of CNC and 3D printing, the arrays could have a closed back as well. I actually considered a slightly curved array as well with 8 drivers per side, which looked quite nicely in VituixCAD simulation.