BillFitzmaurice.info

Hi all. I visited another forum seeking additional reference material for the design and implementation of Line Array systems.

http://audioroundtable.com/misc/nflawp.pdf


I found this pretty interesting. Thanks to Bill's forum, I feel I was able understand the majority of what was written.

Bill.......? Would you agree with the theories written in the above link? They appear to make sense.

Very intriguing.

Titanium Hand wrote: Bill.......? Would you agree with the theories written in the above link?

Some of the recommendations are too strict, relying too much on blind adherence to formula without regard to real world results, but all in all it's mostly accurate.

It certainly appeared immensely strict, especially driver c.t.c. spacing for near field purposed arrays.

The reason I'm researching is because I'd like to build some type of Line Array Cabinet for everyday listening at home.

Unfortunately I don't feel one of your cabs will fit the bill as I have a maximum external width allowance of 5 and a half inches.

Given the linked theory I aim to build the cab utilizing 3 inch mid / full-range drivers in conjunction with the smallest economically available tweeters of some type.

Any help or guidance will be greatly appreciated.

Thanks again for the knowledge

Maybe the SLA system ?

djtrumptight wrote:Maybe the SLA system ?

I'm pretty much using that cabinet as a model. I wish that it would fit within my space parameters

The more I research in conjunction with the space I have available, the clearer it becomes that I may have to settle with a primitive speaker.

To get even a line height of an insignificant 22 inches the total cabinet length will need to be around 2 metres long to support sufficient cu.ft. given my max internal width is only 4.72 inches and ultimately I'd like to have a depth not exceeding 4 inches internally.

Its a big ask. Got to crunch more numbers. See if I can compromise more real estate laterally, off the face of the wall

A faital pro 3 inch driver I'm contemplating can deliver a f3 point of 112Hz in a 0.12 cu.ft. cab. I'm really chasing an f3 ultimately between 90 and 100Hz though so I can cross to sub lower to keep it hard to pin point.

AAAAAAAaaaaaaarrrrrgggghhhhh So much respect for Bill right now for having the skills and knowledge to design these amazing loudspeakers.

If you can afford it in multiples ...... http://www.usspeaker.com/faital%20pro-3fe20-1.htm
Slight EQ boost to 100hz, might not even need tweets.

That is an absolute killer of a 3" driver. I mean a monster. If you want to go with them drop me a line.

I think using only full range drivers you will always need eq or dsp to bring up the treble and the bass. Here's another take on a narrow line array using small drivers, but it must be in a corner. I was considering building a pair using the Madisound 3" Aura drivers at $1 each.

John Murphy's Corner-Line-Array:
http://www.trueaudio.com/Array/

That Faital Driver looks pretty good.

That Corner Line array looks incredible. Great concept for sure. Unfortunately I don't have two corners that I can use for placement.

Got to do a bit more research.

Titanium Hand wrote: That Corner Line array looks incredible. Great concept for sure.

There are a two points that need to be raised. First, an array gets no more benefit from corner loading than any other speaker. It's good to do so when it's practical, but not a deal breaker when it isn't. Second, the 'mirror effect' of ceiling and floor reflections aren't significantly different with a floor to ceiling array than with a shorter array, or for that matter a point source if the frequency is low enough.

That mirror reflection did appear to be way to good to be 100% true.

Could anybody enlighten me to a minimum length for an array to be worthwhile?

When I sit at the viewing position my ears are spot on 1000mm / 39 or so inches above the ground. When I stand my ears are 1630mm / 64 or so inches above the ground.

That would give my ears a potential listening area of 630mm vertically. I read somewhere that to determine the length of array needed you would add either 200 0r 300mm / 8 to 12 inches beneath the lowest listening position and above the highest listening position.

Taking guidance from that paper, the array i build would be best at 1230mm / 48 & 3'8's long, commencing 700mm above the floor level. The more I read however, I feel that the different lengths the sound has to travel to reach my ears from the top and bottom of the array compared to the centre may require me to delve into 'Power shading' or 'Power tapering' perhaps?

Those who know about this sort of thing can you please help to enlighten me?
Giving more detail into the project. Ceiling Height is 2450mm. Its a false ceiling of Gyprock / plasterboard (Aussies) Jib (Kiwis) Sheetrock (Americans) which hides the original concrete roof sprayed with ugly vermiculite from the 70's.
The floor is a floating Bamboo timber product on double thickness underlay (to conform with body corporate by-laws)
Walls are rendered double brick.
The backrest of my couch is 3000mm / 118 and a bit inches from the wall which my TV is just in front of (circulation) and I wish to mount the line arrays onto.
I have precisely 142mm / 5 and a half inches approx. of width at either end of the wall and 1780mm / 70 inches of height at my disposal
As far as depth goes I don't want to push the W.A.F. past 150mm / 6 inches however I could potentially extend to 200mm / 8 inches if I could extract sufficient extension "Shock Horror" to omit the need for a dedicated subwoofer.

I presently have only 290mm of width for a Sub anyway so I will need to 'cut and shut' my TV unit by at least 91mm to accommodate a real one anyway (real = BFM)

Line Arrays seem to be a good option to give me what I want which is a wide and tall soundstage, within the design parameters set by my limited space and gracious wife

All help is greatly appreciated. I will do some sketch up mud maps of floor plan, potential designs and links to any research and calculations that I undertake.

Thanks all

Titanium Hand wrote: Could anybody enlighten me to a minimum length for an array to be worthwhile?

Two drivers have 6dB more output than one, with half the vertical dispersion. There is no minimum for it to be worthwhile. OTOH my experience is that there's no benefit in an array that's higher than 1/3 the distance to the listening position, as that can create as many problems as it solves, which your post touched on. When they are higher than that additional hoops must be jumped through for good results, such as power shading.

Bill Fitzmaurice wrote:OTOH my experience is that there's no benefit in an array that's higher than 1/3 the distance to the listening position

Thanks for that vital piece of information Bill.

It will help me immensely as I am hopeful not to have to use power shading.

The doubling of drivers increase is what I'm chasing, as I'm not going to get the output or extension that I desire out of a single 3 or so inch driver.

With consideration to your last post, the height of my line array should not exceed 1/3 the listening distance; 1/3 x 3000 = 1000.

I'm going to do a sketchup.

Thanks guys