Why so few high end line arrays?

Hi, I am very interested in the line array, especially when listening to them outside. I currently use a Zero autoformer to raise my current 4 ohm speakers to 8 (anything higher than that and it didn't sound right)

I too had been advised of all the combing when I started considering line sources, but physics aside, my ears tell me something else.

I had a chance to hear a used pair of Scaena 3.2's today that were for sale. I have heard the 3.2 in various versions and systems over the past 2.5 years, so I am familiar with how it performs. In this particular demo, it was not setup anywhere close to ideally, since the speakers had just come into the dealer the day before, and there was alot of other gear around. However they didn't have a problem with me tweaking the placement and crossover levels, so I was able to coax a reasonable performance from them, even though no attempt had yet been made to pair them with best match of cables and amps in the store.

That being said, it was the best demo I have ever heard in that store by a significant margin, and that has included Magico V3's, Rockport Mira's various wilsons, Martin Logan CLX, etc. Now to be fair, none of those demos were what I'd consider proper set ups either, but I believe one can tell the basic character of a speaker, even in marginal setups such as these.

I'm not saying the Scaena is the typical line array, in that its almost baffleless design is rather cutting edge, but to my ear it what no other speaker in that showroom had ever done, and made me think that this was a product I could own for a long time. The level of detail, purity, and imaging achieved a level of realism that put them over the top for me. Plus the ability to listen from mid field and far field I thought was fantastic since they drop half of what point sources do over distance. And I didn't feel that instrument size was being overblown.

As I mentioned I am getting in some line sources to audition soon, where the drivers are positioned even closer together than the Scaena. I believe that this actually helps with combing, the closer the drivers are to each other.

Darkmoebius,

You are correct. You have to design line arrays carefully to take into account lobbing and nulls. They work very well when properly designed and will ensure a higher SPL reaches further out into the audience at a sports or rock arena event.

Tbg,

I've been researching line arrays for the last couple of weeks, but that only assures I have way more questions than answers or experience...

But, the website which you refer seems to be only concerned with is only concerned with farfield sound reproduction(stadium, club). Not that nearfield acoustic completely diverge from farfield, but the goals are significantly different.

The "lobing" and "Nulls" which you(and your link) refer to primarily become a problem for listening at the point/frequency where c-to-c spacing of the source(drivers) exceeds the distance of one-half to one full wavelength of the highest frequency produced by that particular array(low, mid, or high).

The "trick" is in designing a widerange(mid/bass) array which crosses over to the next higher frequency array below the threshold where lobing and comb filter effects become troublesome. Within the home audio industry there are a variety of drivers small enough in diameter to achieve those goals.

These issues really seem(to my inexperienced eye) to be no more difficult than the many design limitations and compromises which plague all speaker designs(including traditional 2 or 3-way "box").

Here's a far better, and more technical, analysis(besides Dr Griffin's link above) of the design parameters and limitations of array design in this ElectroVoice paper.

Tbg,

This is audiogon. Laws of physics are very often suspended here. Our favorite products do everything perfectly with no drawbacks or compromises to our favored designs. ;-)

For those with line arrays, this explanation is one of the simplest I have seen:
A good graphical explanation about lobing or "comb filtering" - which are the same thing. It shows snapshots at different frequencies but if you imagine how it will sound at a particular listening position across all frequencies then you will realize that you progressively get multiple nulls as you go higher in frequency.

You think a signal sweep disproves what I said?

09-11-09: Tbg
If you ever look at the frequency response of line arrays, you will see what looks like a comb. Each driver interferes with the others at a regular interval throughout the frequency range.

Selah Audio Alexandrite - on-access Freq Response(200hz-20K), on-access Freq Response(10-200hz)

Selah Audio Symmetrica - on-access Freq Response(200hz-20K), on-access Freq Response(10-200hz)

If you ever look at the frequency response of line arrays, you will see what looks like a comb. Each driver interferes with the others at a regular interval throughout the frequency range. I do love how quick they are, however.

I agree with those micro dynamics at low SPL's. Line arrays tend to sound louder than the volume knob would seem to show. Maybe it's all those speakers (duh)?

I think the one design issue with line arrays is the number of speakers themselves. They do sound good even with low quality drivers. But to get the true best out of them you need better drivers, and that gets expensive. Most of the ones I've heard have been the former, and that could account for my bias against their soundstaging size.

Hi Ptmconsulting,

My arrays stand 5.5 feet tall, shorter than the really big 'uns. Image height is not noticeably exaggerated where I sit (the back of the "nearfield zone").

As well, the image "forwardness" at high volumes in my system goes away below 80 Hz, and is nicely centered/deep at my listening volume sweet spot (about 75 dB average).

In fact, one trait of my arrays is exquisite expression of low level detail and tight, (relatively) impactful bass at such modest spls. It's a benefit that perfectly suits how I prefer to listen. Most array discussions seem to focus on the clarity and dynamics at very high spls - yet at low/modest levels these characteristics transcend any other loudspeakers (lots) I've had in my systems.

I've heard several line arrays. Like any design they seem to do some things wonderfully, but also seem to have issues of their own to contend with and overcome. It's always a trade off for what you consider important.

In my experience and on the ones I've heard, they seem to have:
- very good dynamics, both micro and macro
- very good imaging and soundstaging
- however the image can tend to be overly large, like a 6 foot tall saxophone or a 3 foot wide nose on the singer

From what I understand the overly large image can be compensated for in the design of the crossover and speaker connections. I'm sure newer designs have done this.

It's also important to have proper amp matching, but this is true of any speaker.

I am referring to these speakers.

http://www.audience-av.com/loudspeakers/index.php

Has anyone heard the Audience line arrays?

Emailists:

Your system is impressive. You take your vinyl as seriously as I do my cds!

Headsnappin:

Have you heard the effect of comb filtering in more than one line array model designed for home audio? Can you elaborate on what I should be hearing (or not hearing) that is deleterious to the music? How would you compare/contrast it to the comb filtering of the much more commonplace MTM designs?

JB

Thanks for the response regarding higher impedance speakers. I currently use a Zero autoformer to raise my current 4 ohm speakers to 8 (anything higher than that and it didn't sound right)

Your system looks great as well.

Comb filtering is a problem

There is another approach that is worth considering - The Genesis Horn from Danley Sound Labs. In essence Danley's interpretation of a line array http://www.danleysoundlabs.com/pdf/GenesisHorn-anewbeginning.pdf
As for all line arrays, you are going to need a large room. It is pro audio so it needs a face lift if in the home environment and on display.

Emailists,

I use Atma MA-1s with mine and the arrays are custom wired to yield 13 ohms nominal, 10 ohms minimum. I wasn't prepared for the difference that proper impedance matching makes with OTLs. You are likely in for a treat.

As for comb filtering, diffraction effects manifest in all manner of speakers - even single driver/baffle interactions occur. Not unlike our listening rooms themselves.

It is what we perceive that matters. I hear the bass nodes/nulls in my room quite well, ameliorated as best as possible with traps and PARC. Comb filtering in the "line array physics" sense is imperceptible in my setup. FWIW, I sit 10-11 feet back.

After hearing some outstanding line arrays, I totally understand why people like them. I am about to get a just released line array from a manufacturer for an audition. I was worried about combing as well, but the drivers are small and quite close together, so I suspect at normal (not nearfield) listening distances this should not be a problem.

I'll post back in a few weeks with some initial thoughts, but at 16 ohms, (perfect for my OTL's) and no crossover, I'm thinking this might be an ideal speaker, (for me anyway).

Darkmoebius,

For the sake of brevity I did not go into as much detail. Yes it is true that a line array of woofers operating below 300 Hz is generally no problem due to the wavelengths of low frequencies. As you go up in frequency the problems start, unfortunately right in the mid range is where it can begin to be a problem.

It is much the same reason that some people argue that center channels are more trouble than they are worth....

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.

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.

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.

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.

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.

I think Mapman has the best explanation. Two best I've heard, both from the same designer, are the Nearfield Pipedreams and the Sceana speaker system. There are other speakers that do things better, but I tend to like the presentation these speakers give. My wife will not allow them in our living room (my listening room), though, for the same size reason I wasn't able to get Duntech Sovereigns years ago.

Line arrays are expensive to do well and work best in larger rooms only as well, I believe, hence limited market.

Despite that, there are some good ones out there I believe.

vintage mac