Man, I have come to the realization that almost no one has heard an actual line source speaker. A line "array" speaker? Yes.
But that means very little.
But not an actual "Line Array" speaker that can produce the actual "Line Source Theories, Cylindrical, Expanding Wave"? No.
The closest you have heard is a line array. Producing what many call the, "Line source effects". And that? Is not even remotely close to what can be achieved with a correctly implemented Line Source design. Even if in the application of that design it is only 50% capable, "If that", in it's attempt at fully resolving the coherent primary wave which all are after.. That's about where I stand now I believe. And the results are damned astounding. And nobody has ever published it's "Actual" effects! Nor have I ever heard anyone even list them past the few that everyone talks about! And then dismiss them, because the far-field gains are only so much. And distortions can be lessened in another way as well....right? But there is more. So much more....And I cannot be the only one to ever find these "effects"?
In truth every line source design I have seen has at some point "Forgotten the original science behind and IN the theory itself". Especially when actually building a speaker, while using that theory as namesake.
This means that they all are indeed NOT, what they call themselves.
An easy trap to befall you as I myself fell into it.
I then pulled myself out and attacked every problem individually. And had some luck also I believe. Having studied Elec. Current Theories, Particle Physics and Viscous Flow all helped. As did others like Wave Mechanics and String theorem. But it still all came down to listening....If anyone would like to listen I could arrange it.
One thing everyone seems to forget though?
When you build a point source? It is still a point source no matter where it operates.
When you build an "actual", Line Source? It can only be that, dependent on several environmental criteria having been met. OR, It will simply de-fault and become a Point Source device.
"Like when an escalator shall cease to move? It simply becomes a stair!
These basics are written in the original theory. And subject to what I currently call, "Line Source Law".
Don't give up! Better things are on the horizon!
Scott
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That's high praise for Soundlabs when it comes from your keyboard, Duke. One thing I've learned to appreciate from my line arrays (which you've listened to in my home)is their preservation of dynamics and detail at low listening volumes. It's counter to the oft-given kudos for high volume listening performance that arrays generally receive. The addition of outboard subs which can be dialed in for low volume output complementary to the arrays makes for one of the most satisfying low listening volume setups for me. Wife and neighbors agree! |
Hce4, comb filtering in the vertical plane is dealt with by having the inter-driver spacing small in relation to the wavelengths produced, and/or using drivers that inherently have limited vertical dispersion anyway and therefore little or no overlap vertical overlap (like the full-height ribbons in the modules that make up the Dali Megailne).
In the horizontal plane, we want the inter-driver spacing as small a possible in relation to a wavelength at the crossover frequency. A steep crossover also helps to prevent lobing in the horizonatal plane by narrowing the frequency region covered by two drivers.
Some prosound line arrays have slot-loaded compression drivers flanked by a pair of midwoofers. The slot loading of the compression driver gives it a narrow horizontal footprint but wide horizontal coverage, along with narrow vertical dispersion (which minimizes vertical comb filtering) in a format that allows a fairly low crossover frequency so that the flanking midwoofers don't beam too badly in the horizontal plane in the crossover region. With the right crossover, it should be possible to avoid any deep nulls in the horizontal plane within the coverage angle of the array.
Duke |
That's quite a compliment Duke!
How do line arrays deal with "comb filtering", or is it not an issue? |
"Is there any inherent advantage to either of these speaker designs [Line array or point source]?" - Mitch4t
The main difference is that output from a line source or line array will fall off at 3 dB for every doubling of distance, instead of 6 dB for every doubling of distance for a point source, under anechoic conditions.
Some time ago I measured a line-source and a point-source speaker at 1 meter and again back at 8 meters, in a large living room. The reverberant field contribution was thus included.
Anechoic theory would predict a falloff of 18 dB for the point source and 9 dB for the line source (going from 1 meter back to 8 meters = three doublings of distance). The actual measured falloff (using broadband pink noise) was 11 dB for the point source and only 4 dB for the line source!
Now why this matters is, that uniform sounfield is significantly closer to what you normally experience at a live performance, and so it better conveys the "feel" of listening to live music. Also, the sweet spot is a lot wider than normal because the SPL doesn't change much as you move from side to side.
"I have heard excellent line arrays, but one respected engineer has told me that arrays have different arrival times, since the drivers are different distances from the listener, and thus could not recommend them." - Emailists
A true line source beams severely in the vertical dimension, but the beam is a coherent wavefront the height of the speaker, so different arrival times is not an issue.
The more a line array (vertical stack of drivers) departs from behaving as a true line source, the more different arrival times becomes a reality. However, different arrival times in the vertical plane is far less detrimental than different arrival times in the horizontal plane. The ears will cue off of the first arrival sound for imaging purposes, and so you may well find that the image height is at ear level whether you are sitting or standing. If there is any degradation of clarity, it is minor or negligible with a good line array.
One of the reasons I don't build line source or line array speakers is, I don't see any window of opportunity to "build a better mousetrap". I happen to be a dealer for the same line-source speaker that Essentialaudio is, and when I informed their designer (Roger West) that I was embarking on my own commercial speaker venture, I told him that my goal was to build the second-best speakers in the world. As far as the basic concept goes, I do not know how to improve on what he's doing, nor do I have the skills to even try to equal it.
Duke |
I have heard excellent line arrays, but one respected engineer has told me that arrays have different arrival times, since the drivers are different distances from the listener, and thus could not recommend them. I have seen a curved line array online that solved the distance issue, but I can't seem to find a link.
Here is a an interesting discussion on line arrays.
http://www.diyaudio.com/forums/multi-way/17948-line-source-speaker.html |
Johnk: No, virtual line source. Sound Lab full range electrostatic. You can read about it here. |
Essentialaudio you mean point source? |
"All of the line source speakers I have heard in my life sounded better and played with less distortion to my ears than any point source speaker. Line sources are better but they are much more expensive. The best usually is.'
Agree, expensive line source designs with multiple drivers are probably best in general for larger rooms where you want to go loud with lower distortion.
For smaller rooms, fewer drivers and designs that simulate a point source more work better in general. Some with larger drivers like the larger OHMs in particular can work very well in larger rooms also. |
All of the line source speakers I have heard in my life sounded better and played with less distortion to my ears than any point source speaker. Line sources are better but they are much more expensive. The best usually is. |
The speakers I use and sell have single drivers...they just happen to be very large and are designed to operate as full range virtual line sources. |
"The so called 'point source' is an attempt to construct a
microphon in the 'reverse': as a sound source. The only one
that works or that I know of is the Manger midd/high speaker. The Kef and the TAD are actualy a compromise."
The CLS Walsh type drivers in OHM Acoustics Walsh line speakers actually approximate a very wide dispersion (pseudo omni) point source extremely well in most setups, especially in but not limited to the horizontal plane.
The key difference between a well executed line source versus point source is mostly in the geometry of the sound dispersion pattern which is a primary determining factor for imaging and soundstage.
Whether point or line source works better in this regard has largely to do with size, shape and perhaps liveliness of your listening room, the location of the speakers within it, and your location as the listener within it as well. |
If I am well informed the line source has less problems with two boundarys: ceiling and floor. BTW I wish I owned
Alberts Megaline. The ordinary kind will also do.
The so called 'point source' is an attempt to construct a
microphon in the 'reverse': as a sound source. The only one
that works or that I know of is the Manger midd/high speaker. The Kef and the TAD are actualy a compromise.
There are also those German Ascendo speakers by wich you
need to measure the distance between the tweeter and your
own ears and move the tweeter to the right distance like
a geometre. The version M (?) is realy very impressive but
also very ugly to see. This however is taste dependent.
Regards, |
Hello,
Actually Dali Megaline uses multiple tweeters in a line array.
IMO and in absolute terms a line source will give better performance than a point source.
regards, |
This really IS an interesting question--one that very few people will probalbly agree on an answer to.
Having been closely associated with the Nearfield Acoustics Pipedreams, I'm hesitant to say that focus is 'better' with a single tweeter/line array/panel/omnipolar and so on.
These guys (certain model 21's) had 42 tweeters, one inch domes...with 21 4"+ inch mid's crossing over to a sub, or subs that were 18" cylinders. If all this sounds unusual, I thought so too. Then spent a couple of years 'setting them up' the right way (after many hours of listening).
One might think that (and some may even claim) there would be 'confusion' from the multiplicity of tweeters in a vertical array--AND one may point out, rightfully that 'comb-filter effects' are created by such--however, to my silly little ears, they sounded really remarkable and did not seem to have problems with this effect.
In fairness, there were 'supposed' technologies in place to ameliorate such issues, but I've never been able to gleen what those technologies might have been.
I only knew the Pipedreams to have been very dynamic and impressive, and to have had wonderful presence.
(Read Johnathan Valin's raves for a reference point).
There are many ways to achieve Nirvana, I suppose...so I'm, at this late stage of my existance, unable to say emperically which method of loudspeaker tech is 'better'.
Great question...and fodder for lots of interesting responses.
Best,
Larry |
Al
Thank you for exercising restrain in your response.
Jim |
Line array loses less SPL with distance point source should image a bit better but this all depends on total design. Line arrays are large, point source designs usually not so large. |
Line arrays have dynamics across the band. A dozen bass/mid drivers that go down to 40Hz each still only go down to 40Hz but they can do it really well. Might seem silly to add subs to such large speakers but haven't seen an Incredarray in a while.
Impedance can be tailored with some brands.
They say that distortion is lower because the load is spread but that, like most things audio, means less than the perception.
Coming from an Infinity/Genesis background, like yourself Mitch4t, line arrays are naturally attractive. You might want to set them up lengthwise in your room to sit far enough back.
http://audioroundtable.com/misc/nflawp.pdf |
To me a point source if well executed should sound more coherent with much more focus. I have no idea why anyone (except Al Porter) would go down this road. Instead of ten tweeters why not use just one? Actually Dali Megaline have only one tweeter per channel, it just happens to be 7 feet tall, so yes it's a line source :^). I like them a lot but also like point source speakers with Dynaudio, Kharma and Avalon immediately coming to mind. Each design has advantages and there's probably white papers on the web explaining why each is superior to the other. The obvious answer, there's no substitute for listening to every speaker that interest you and then considering room size and budget try to pick a winner. |
To me a point source if well executed should sound more coherent with much more focus. I have no idea why anyone (except Al Porter) would go down this road. Instead of ten tweeters why not use just one?
Let me know if you disagree and tell me what speaker you love and I will take a listen at the next RMAF. |
