Position of Subs

[Albatross]

A line array in a 15m room?

Exactly. Anyone of the suppliers who has reccomended a line array in that small a room should be crossed off the list.

They are not going to give you something suitable for your space.

[azlan]

Whilst a full on line array may not be the right tool for the job, I can see how a couple of 'wide horizontal, tight vertical' boxes flown above each other could be used to give a reasonably even coverage in the room.

 

This is something I've never quite got, even if the system is not producing the cylindrical wavefront and all the jazz, the properties that make line array boxes good for arrays can make them useful in other situations too.

 

I could see the single point pickup for the rigging and the small profile of the boxes both proving useful on a smallish school hall

[Brian]

...the properties that make line array boxes good for arrays can make them useful in other situations too.

 

But that's the point isn't it? A 'line array' box on its own, or even a couple of them, do not exhibit the properties of line arrays especially vertical control.

[azlan]

If the individual box has a 20ish degree vertical dispersion, then there is nothing stopping it being used to cover 20 degrees vertically on its own?

 

I might be missing something, as most my experience is small point source systems or 'proper' arrays, but a speaker is a speaker and as long as the specs are given for a single box, I cant see how it would be any different from a conventional point source box with the same spec?

[top-cat]

I think he's probably referring to how in a 15m room there is not so much real need for a 20º dispersion speaker. You either use it for long throw applications or group it with several of them (therein referred to as an array) to get a bigger dispersion.

[sam.spoons]

I may be missing something as I have no practical experience of Line Arrays or their expensive individual boxes but I've done a fair bit of reading. So, surely the vertical dispersion of the array is dependent on the length/width ratio of the array? If that's the case then an individual box, typically a 2x12H with the LF drivers side by side and the Horn in between them would display a dispersion pattern wider in the vertical than the horizontal, and two boxes stacked (as I've seen on a rig in a local dealer) would have approximately equal dispersion angles in both the vertical and horizontal planes (at least below the crossover frequency)? The upper frequencies are pretty much dependent on the horn flare regardless of the array (high frequencies are more directional anyway).

[valooz]

...the properties that make line array boxes good for arrays can make them useful in other situations too.

 

But that's the point isn't it? A 'line array' box on its own, or even a couple of them, do not exhibit the properties of line arrays especially vertical control.

 

 

Just my 2p, any box (including point source) arrayed in "a line" is a Line Array. A Line Source is something very different, that requires a much longer "array" to actually approach the definition of a line source.

 

So yes, boxes that have the properties to create a line source when used in longer arrays (including waveguide properties that allow this...) can be used in smaller quantities to form a line array, that is sometimes very suitable for the purpose...

[Simon Lewis]

This might just be splitting hairs, but I understood the term Line Array to describe a number of loudspeaker elements (normally identical within a given passband) arranged in a line and positioned close enough to ensure coupling (at the frequency of interest) and thus tending towards acoustic line source properties.

 

While using one or two boxes close to each may modify directivity or reduce more destructive interference, it is not line array behaviour per se.

 

Many column loudspeakers serve as good examples - too few elements to produce an array that is acoustically long with respect to wavelength, and spaced too far apart to couple effectively without significant lobing in the wanted passband.

 

Of course, we can take any loudspeaker and use it as we like, but the pattern control and line source behaviour that characterises a true line array isn't achieved with just a few boxes...

[Shez]

I think "line array" has just become a marketing term now and is pretty meaningless. "Line source" is still somewhat less abused.

[sam.spoons]

I'd be interested to see a polar pattern diagram for a single LA box (just to see if my guess above is correct)

[Brian]

...a single LA box (just to see if my guess above is correct)

 

What sort of driver arrangement? Something like this....?

 

[sam.spoons]

...a single LA box (just to see if my guess above is correct)

 

What sort of driver arrangement? Something like this....?

 

 

Not quite, I've seen two way boxes with two 10" or 12" LF drivers that look not unlike those (which I guess are three way). I'd have thought a single box like that would have a weird polar pattern with the waveguide HF giving a wide horizontal but narrow vertical dispersion and the two LF drivers coupling to give a wide vert but narrower horizontal pattern. At the end of the day a single LA box on it's own is just a point source box with some special HF jiggery-pokery going on isn't it?

[ojc123]

In typical Blue Room style everyone's forgotten my original question. However, I thought I'd just let you know that I'm going to see/hear an install with subs under the stage so I can make a better judgement about whether that's the way to go.

 

Thanks for all the discussion about line arrays. I'll bear all that in mind when we get to decision time.

[sam.spoons]

I love the way these discussions go off on interesting tangents http://www.blue-room.org.uk/public/style_emoticons/default/smile.gif though I can see how it may be frustrating if they manage to bypass answering your original question. Thankfully most questions get a number of potentially useful answers before digression occurs.

[azlan]

On topic post, my old venue had 4 twin 18" subs under stage, which made the stage resonate massively, the solution was to surround them with bunkers made of concrete blocks, with a wooden frame filled with builders sand for a lid.