HCLAF Speaker Project

[agedhorse]

Steve, you bring up another excellent point.

 

Another way to alter the effects of horizontal spacing is to "bend" the baffle by a few degrees (effectively taking the horizontal drivers out of a common plane).

 

The effects of multiple drivers can be minimized by using the most efficient and high powered drivers you can buy, and thus using a smaller quantity keeping thge overall dimensions in thge horizontal plane at a minimum.

[agedhorse]

I've got another idea to think about... since line arrays are always used in multiples, what about building the equiv. of say 3 or 4 individual cells (cabinets) into a single module. This would be a bigger, heavier cabinet, but far fewer of them, and then we have more flexibility with area and interdriver spacing since there are not a bunch of tops and bottoms to deal with. Also, total weight would be much less.

[Steve_B]

I

[agedhorse]

I was considering bending the baffle either in or out just a few degrees. Either way, it alters the comb filtering. Angle the baffle in and the driver pattern crossfires at distance, out and it doesn't crossfire, but the pattern will look similar at whatever far-field distance you choose to measure.

 

My suggestion to look at a larger cabinet comes from the fact that the smaller cabinets must be used in multiples of a minimum of approx. 4 in order to take advantage of some of the primary benefits of linear arraying technique. With a 4 box module built into 1 cabinet, you eliminate 6 tops/bottoms from the weight of the module, and all the box to box rigging hardware other than what's needed for the actual box (module). I understand the weight issue... so how light could we make it using high quality drivers like even the new JBL N-dyms which are very light. If the individual cabinets were say 50 lbs, it is possible that a module of say 3 could be built using lighter weight (more expensive) drivers and poplar plywood and come in at around 95 lbs, but that would still be a rather compact and powerful package. SLS had i cute integrated box line array system, not very wide, but about 8' tall and I have heard it... sounds very nice. a couple of those cabinets per side hang would be quite a "perky" PA.

 

This is just an idea to consider. Even doubling up so that the modules were the equivelant of 2 boxes would save some weight.

[Ford Audio Serv]

HCLA participants;

 

As we set out on this adventure a short time ago I had hoped to gain some knowledge as well as share what little knowledge I have in the design of a line array speaker system. As we progress I feel we are looking on to something far greater. It is rare in this day and age that people from all over the world come together in an attempt to achieve something that is not driven by corporate advancement.

 

The ideas and knowledge that have been shared here so far may seem basic and rudimentary to some but to me and many others it is golden. We are all busy people

[Steve_B]

Apologies to agedhorse. I was running short of time on my last post and probably (no probable about it) didn

[agedhorse]

The J hang is appropriate for many larger venues, where you have the height available to enable using the bottom-most splay. If you are playing in rooms with 20 ft. ceilings, then you will not need much of a bottom-fill splay. Also, the smaller venues might be better served by dedicated front fill boxes?

 

Looking at a typical venue that we have targeted, and the fact that many of the venues just are not practical for flying PA in (with lower production budgets), groundstacking of the system is something that must be considered as a common configuration. With groundstacking, the J is not an issue... but more appropriately, a balcony "tip" would be more common but the angle of the tip and the longer throw would indicate that you would want to tip back at least a module of 3 boxes to retain some pattern control for that zone.

 

A 9 box a side system (using 10" LF's) would end up being about 8 feet high, so using 2 modules of 3 drivers high, the top box bottom surface would be at 5-1/2 feet which is an easy lift for a third module in a deck stacked orientation. (subs lined up to the offstage side) Add your balcony tip front blocks (we have found that typically about 3 - 5 degrees is about right) and it's a done deal.

 

If you only needed 2 modules a side, they could be stacked on subs to keep more compact. A small venue with only 1 module a side would still kick some ass.

[Steve_B]

I agree. It makes sense for people building their own to adapt the design to what suits them best. I can

[agedhorse]

This is just another option to consider... for my uses, individual boxes make more sense since I do (or did) lots of diverse and large rooms, but for 1000 seat and under ground stacked systems it would be more economical.

[kevinnemrava]

I agree that some thought must be put in to the hoizontial coverage of the system. I do not think this will really be that much of a problem- high freq will be on a horn, so all we nee is the right horn. the mid frew can be on a wave guide (like one of the designs given), and for the low freq it is not very directionial anyway(and there is not much we can do with this size box ).

 

myself and jeremy are looking in to a coaxial driver that may help us too.

 

The 1/2 wave lenght number that was quoted I believe applies to the verticial spaceing of the line array , not the horizontial spaceing of compnents. Although it is genrally acepted that you want the 2 drivers of a cross over to be as close together as possible.

[agedhorse]

The problem that I see with arraying coax drivers is that the driver-mouth spacing may be an issue within the context of an array. They are a great option for wedges though!

[kevinnemrava]

ahh yes, ... an oversight on my part you are very right.

[Steve_B]

Kevin,

 

The half wavelength thing works in all directions and in my opinion should definitely be considered in the horizontal direction. If you follow the existing designs for a line array, the problems are not in the high frequencies but the mid frequencies. There seems to be a common fallacy in the sound reinforcement world that the directivity of a loudspeaker is defined by the horn. That a 15

[kevinnemrava]

you make some good points.

 

my thoughs are that it is importand that we even coverage in teh horizontial. To do this we need to 1 pick our horn , then build a wave guid for the other components at that same dispertion angle.

 

The 1/4 wave lenght will not happin the the horizontial if we do this. I believe that that guideing pricible is being used incoertly here though. The idea behind the 1/4 WL, as I uderstand it is this:

 

In an array of many points, emmiting the same , but any number of waves (at different freq but same amlitude) the waves spaced about 1/4 or less will combine in to an approximation of a flat wave front.

 

in the case of the cross over point we know that we will not be combining wave of the same freq+ aplitude(the whole point of useing a cross over) with the exception of the specific cross reagion. This is with out consifering the phase effects of the crossover.

 

Also the 1/4 wave length rule implys the use of many emitters, in case of crossover we have only 2 (the high and low), and so a combine wave front will not form anyway. This is not a problem though, when considering that if you go an octave above or below the cross over point there is effectively only 1 driver working in that range anyway. hence we are back to a vertical array of drivers.

 

My conclusion is that we should sacrifice the 1/4 spaceing between drivers (horizontially), in favour of some form of wave guide, that will give us the horiziontial coverage we need.

[Steve_B]

I guess we will have to agree to disagree on some of our design philosophies. As the manufacturers have shown there are a multitude of approaches all which seem to have some degree of success. This bodes well for the home constructor in that it sort of slackens the tolerances we need to work to.

 

With regards to why you think that the summation of sound sources doesn

[J the D]

Would it pay to have a cone with multiple drivers that are mechanically aligned for phase and comb purposes like the new Yorkville Unity Series?

[Steve_B]

The Yorkville Unity loudspeaker is more like a conventional cabinet and presumably would array in a similar manner. If your idea was to just use a design similar to the mid high section then the 60 x 60 degree (surely it should be 60 degree conical for a round horn?) has the wrong dispersion pattern.

 

Despite my comments on some of the marketing claims by a number of the manufacturers, it is still important to reduce the spacing between each individual drive unit to a minimum. With the unity design, although the drivers are closely coupled in each horn, the spacing between each horn would be too great. Redesigning the horn so that it was shorter and wider would improve things; a bit like the EAW730.

 

Note that the

[J the D]

The Unity arrays horizonally in a tight pack of three cabinets. It shows a polar plot that is remarkably smooth when arrayed that way. I did not know if the mechanical phase alignment principles for different drivers on the same horn could be could be applied to a more traditional array. The inherent avoidance of interference seemed attractive.

[Steve_B]

I

[J the D]

My primary question is would the multiple driver horn used on the Unity series be as effective in a vertical line array as it appears to be in a horizonal array?

[agedhorse]

A line array is a different way to combine the output of cabinets.. the goal of a conventional array is to avoid unnecessary overlapping of the boxes (at least the horn part of the box).

 

With a line array, the overlapping is in fact an essential part of achieving pattern control.

[Steve_B]

Agedhorse must have been typing at the same time as me and makes my first paragraph somewhat superfluous. Being a non-typer I

[Jack Arnott]

This response is to many of the recent posts.

 

For J the D about the unity horns.

The Unity works on the horizontal, and adds coverage in degrees. somewhat like adding slices to a pie. It works because the HF drivers are very close to each other, at the apex of the slices. If the splay was taken out of the cabinets, and the horizontal were turned to the vertical you have now defeated the purpose of the unity horn. The drivers are no longer close to each other, and they are each covering the same area, not each covering their own slice. So there is now destructive interference. This is the crux of the line array, to get each source close enough together, or to appear close enough together to couple as one source. To produce one coherent wavefront. This is fairly easy up to 1K, but after that it becomes physically harder to get the sources close enough together to be one wavefront. IE, the 1/4 wavelength of 1K works with a 6"cone, so if you have a bunch of 6" cones stacked on top of each other they will couple as one vertical unit.

So basically the idea is to get all the drivers on one horn, but it needs to be implemented much differently than the unity style. (I do applaud the unity idea and use both the factory SPL and proriatary designs.)

 

Another point of Steves that seems to be lost is the 1/4 wavelenght in the horizontal. What he is saying is that if the horizontal placement is not close enough together that there will be cancelations in this dimension. And that the crossover point is determined by where the cones are coherently adding on this plane. Speaker manufactureres use some of this to control the directivity. See the EAW add for the speakers with the side firing lows (~30" wide). There is cancelation on the sides, and addition to the front and rear, for a bipolar dispersion. But if the drivers are too far apart for their bandwidth, there will be ripples in the intended dispersion pattern, not just nulls on the sides of the boxes.

 

Also, not that it matters much, but I think the coax that Kevin is talking about is a compression driver with a single 2" exit, not a cone with HF attached.

 

And finally to Mr. Ford. (Who directed my attention here in the first place.) I love the drawings, and the speed with which you addapt to each new proposal. Also your overall enthusiasm and direction on this project. My one concern is with your intended flyware. There is a reason that ATM is at the price point that it is, and the standard air cargo rails are cheap. Air cargo rails are meant to secure cargo to the inside of a plane and keep it from shifting. I am all for a ground stacked system to be built on the cheap. But if this system is intended for overhead use, money cannot be pinched, and saftey ignored. This is one portion of the project that must be designed, tested, and implemented by the pros.

 

Keep it up everybody. I am planning on a line array project of my own, and some of my views differ from those expressed here. I think it will be hard to get everybody to aggree on one single project design, but it is great to hear everybodys input, and some ideas expressed here have changed my intended plans already.

 

Regards, Jack

[Steve_B]

Jack,

 

Would you care to elaborate on your project and some of the which, hows and whys of your differing views? I

[agedhorse]

 

Originally posted by Jack Arnott This response is to many of the recent posts. My one concern is with your intended flyware. There is a reason that ATM is at the price point that it is, and the standard air cargo rails are cheap. Air cargo rails are meant to secure cargo to the inside of a plane and keep it from shifting. I am all for a ground stacked system to be built on the cheap. But if this system is intended for overhead use, money cannot be pinched, and saftey ignored. This is one portion of the project that must be designed, tested, and implemented by the pros. Regards, Jack

 

 

This is why I have always used ATM Flyware in the cabinets that I have designed. It's not just the hardware, but the integration of the hardware into the entire structural package that is what makes the system safe.