Why so few high end line arrays?

Real Long

I am a fan of the concept and have had the good fortune to hear the best pair of IRS Vs in existance a number of times.
If you think I am overstating the IRS Vs , they were made by and owned arnie Nudell as an example of the worlds absolute best speaker ever concieved. They were vetted to the press played a couple of days and went into their crates until Miller Speaker's Bill Legall aquired them.
He owned one set of the few that were made already. Being as meticulous as he is each driver was rebuilt and reinforced. His specialty was repair of infinity and he is a true obsessive perfectionist.
The bass arrays consist of only 6 12 inch drivers with 1000 watt amps per siide. The panels ahave special IRS V size Emims. I think there are 16. A peculiar unanticipated fact Bill tells me is that they are smaller than other IRS mims and easier to drive. Then the 32 emit tweeters on each each panel.
How did they sound ..... the absolute most overwhelming musical experience I have ever known. It is as if they evelop you in sound.
Think of the cost. Arnie used the best stuff he could as he eagerly greeted the challenge of making the best on earth. The magazine called New York had them on the cover. It stating that in 1987 dollars that these cost $100,000 to make. That seems a bit paltry nowadays with that kind of price attached to a number of TOTL showcase pieces. At the time it was an unheard of indulgence.
I never did ask him what paid for them and the value of his effort he put into them including hand rubbing ten coats of tung oil into the rosewood each month or so. That made them look like a million too.
He sold them much to my dismay, to one of his friends and admirers of him and those speakers. The buyer whose dream came true.
He said yes the other set isn't as pedigreed as those but they sound good enough. I was upset because his integrity cost him an additional $15K over the lowest price they should have been offered for, when yet another friend and customer offered more when the first guy was having difficulty scrambling to liquidate the funds.
The truth is that most of todays behemoths don't use parts and even remotely as expensive these. Even though they cost a lot more than these. Building them today is unthinkable there isn't any more of that wood left just to start. Imagine a giant panel of cone and domes lets say diamond tweeters or Esotars at a min of about 1,000 a pair times 32 pairs then 16 Ceramic or aerogel mids and 12 custom woofers with a great on board amp per etc.

I used to stack 4 pairs of every speaker I had as a teen. I guess that will be the only line array I will know.
Don't dispair I have a dozen pairs of speakers. I could use all my amps and do it again. I think the sound would be more cacophony than hi fidelity. So I stay with my JMs or old BLs or Older JBLs or my Klipsch La Scalas and heresys or the Tannoys......

My latest outrageous speaker notion is... .(like you give a )...To get even poorer fast. A column of those Feastrex drivers allrange at $50K/Pair. A stack of 12 in a voluminous tower but each in its own reiforced dampened enclosure but back horn style vented into one big tuned port to reinforce the bass.

Like you, Jb, I have a pair of Selah Audio line arrays. They're very impressive and really envelope you in sound. But yes, they're big and dominate a room, invoking the WAF factor (it did in my case). And yes, the cost of 16 quality drivers per side ups the ante in terms of cost (though Selah's designs are a real bargain).
Also, the sound isn't for everybody. It's very dynamic and 'throws' the sound forward. Some like a mellower sound that draws you in. But the life-size soundstage and realistic dynamics make for a lively sound that's hard to resist, IMO.

They work great at concerts and for sports stadiums....definitely a mistake for home audio, IMHO.

You are getting serious comb filtering from listening close up to multiple drivers with the same bandwidth.

I discuss what I call "LSESL", or Line Source ESL design, in my most recent article at Dagogo.com. I'm referring in that term to the Kingsound King, a large planar (You can tell I'm just a BIT excited about this technology). Quad has used a similar concept in their speakers for years, and we all know how that's been received. To my ear, the multi-driver concept with the ESL technology is a fantastic combo. One can certainly achieve a tremendously satisfying result implementing multiple ESL drivers as opposed to cones.

09-04-09: Shadorne
You are getting serious comb filtering from listening close up to multiple drivers with the same bandwidth.

Not entirely true. Comb filtering is NOT an issue in nearfield listening if the center-to-center distance of the drivers used does not exceed a distance equal to the speed of sound (at ocean level) divided by the highest frequency handled by that particular line of drivers (bass, mid-bass, treble).

Dr. James R. Griffin, Ph.D, has a fairly definitive white paper on the subject titled "Design Guidelines for Practical Near Field Line Arrays"(.pdf) that discusses the subject in-depth. In the paper, he provides all the basic criterion for creating a successful line array:

Center-to-center Driver Separation (Circular drivers). We want our discrete driver array to approximate a continuous line source. This spacing is the separation between the centers of the adjacent drivers in the line and includes any mounting allowances and the flanges surrounding the drivers. In the limit the closest spacing would be dictated by the flange diameters of the drivers although some drivers have truncated flanges that would allow closer spacing. Two different solutions (Table I) for the driver separation guidelines are presented in the literature for circular drivers. These cases are:

1. Far Field. Ureda [3] uses driver directivity to determine that circular drivers need to be positioned within one wavelength center-to-center at their highest operating frequency. Wavelength is equal to the velocity of sound (344 m/s or 1130 feet/s) divided by the frequency. Directivity of the multiple drivers in the line increases until one wavelength spacing is reached and starts to decrease beyond this spacing. Figure 7 illustrates how the sound wavefront is created by a line array. Spacing less than one wavelength creates a constant phase front but comb lines start to form beyond one wavelength separation. At two wavelengths separation the first cancellation occurs. Directivity continues to decrease with more severe comb line effects as the spacing increases beyond two wavelengths.

2. Near field. Urban, et al [1] derives a more restrictive criterion of no more than a half wavelength separation between drivers at their highest operating frequency. Fresnel analysis is used and a disruption grid is used to shutter a continuous line source in their work. This analysis is based upon their desire to place any far field dips (nulls) in the angle off axis response of the array beyond p/2 (90 degrees). This assures that secondary (off-axis) lobes in the sound field are greater than 12 dB down from the on-axis response (main lobe)...

For the tweeter line very close center-to-center spacing is difficult to attain as very small circular drivers would be necessitated for either the one wavelength or especially the half wavelength criteria. Consider operation to 20 kHz where one wavelength is 17.2 mm (0.68”) and a half wavelength is only 8.6 mm (0.34”). Without regard to their surrounding flanges, dome tweeters are available in 25 mm (1”), 19 mm (0.75”) and 13 mm (0.5”) diameters. Hence, with any mounting flange allowance at all, the one or half wavelength c-t-c criteria are very difficult—if not impossible--to satisfy at 20 kHz. But, if we relax the c-t-c criterion, more secondary lobes would appear in the 10 to 20 kHz frequency range. Fortunately, in this octave the ear is less sensitive (per Fletcher-Munson curves) so any secondary lobes likely would be less audible to the listener. Thus, if one wavelength spacing at 10 kHz is adopted as a compromise, then tweeter spacing would need to be 34.4 mm (1.35”) c-t-c apart. While more off axis secondary lobes would be generated in the far field, small flange tweeters are available to meet this dimension. The tradeoff is possible sound degradation from comb lines near 20 kHz.