[seadogs1]

Could someone, anyone explain the difference between point source and line source to me? And what advantage or disadvantage has as pertains to loudspeakers.

[jholtz]

I assume you are referring to a line array speaker vs. a conventional point source speaker with your question so I’ll answer it as such.

Line arrays have the following benefits in comparison to point source:

1.   Exceptional and effortless dynamics.
2.   Exceptional detail.
3.   Walk around “you are there” imaging.
4.   High efficiency so they are easily powered with low powered amps.
5.   Nearfield listening provides a very realistic “you are there” experience.

There are more but these are a few of the major ones. Arrays are VERY addictive.  Once you experience a properly designed line array it really spoils you for any other type of speaker.

HTH

Jim

[BobM]

I agree with the above, after hearing several arrays. However, setup is very important (but then again, when isn't it).

I think the most common problem I've heard with line arrays is the overly large image size, i.e. a 3 foot wide "nose" projected in the center of the speakers as the singer sings his/her merry song, or a 10 foot large saxophone playing a solo. This can be ameliorated in the line array design by "rolling off" the relative loudness of the topmost and bottom most speakers int he array, but is not necessarily done in all arrays.

The imaging can be scary when done right, and the dynamics rival a good horn system. It is definitely something to check out, but it is not everyone's cup of tea.

Enjoy,
Bob

[samplesj]

Ok, I'm not sure if this is what the original poster meant, but we're sort of confusing line source with a specific type of line source the line array.

A line array is a line source, but there are also other line sources.  Most planar (magnetic and electrostatic) speakers are also line sources.

Most of the aspects mentioned above are specific to only line arrays because of their multiple drivers (eff/dynamics).

In general a line source does have a couple of major benefits over a point source.  A line source will decrease in sound at 3db per doubling of distance vs 6db for a point source.  This does mean that less power may be needed, but it isn't directly a boost to efficency but rather a reduction of loss.  Part of the consistancy in sound from a line source is because it doesn't vary loudness in different places in the room as much.

Line sources are also impacted much less/very little by the floor and ceiling.  It is more of a cylinder vs a sphere radiation pattern.  This means that a line source doesn't necessarily need as much treatment at those reflection points.

[klh]

I would also add, and correct me if I'm wrong, that line arrays are designed specifically for nearfield listening whereas point sources can be nearfield or farfieled. This usually isn't an issue since the speakers are so tall... all but the largest rooms stay withing the nearfield. Having said that, line arrays are theoretically designed to be in phase at a particular depth. Lateral seating isn't as critical as how far you are from speakers. I would imagine "the depth of clarity" (my own phrase ) depends on how well the crossover is designed. Given the above statements and the shear amount of dynamics, line arrays can do wonders in a single row home theater.  Most people agree in that situation the imaging is so spectacular that you don't need a center channel. Moreover, it would rather difficult to integrate one with the line arrays anyways. From what I've gathered, line arrays also need a wide room to really get their wide sweet spot. The height of the room doesn't matter very much do to the previously mentioned cylindrical dispersion pattern. Also, since there are so many speakers in a line array, many modes are excited and thus you get a more uniform sound throughout the room. If you get a line array with XBL tech, the benefits of those acoustics should extend to 30Hz or even below. With that many drivers with that extension, a subwoofer would only be necessary for the craziest of people! This would also decrease (though never eliminate) the need for passive acoustic room treatments.

Bob... a quick question. You mentioned the problem of overly large imaging. Decreasing the output of the outer drivers makes sense, but wouldn't that also increase the vertical dispersion of the speakers? I'm sure it's worth the tradeoff even if it does.

[jholtz]

I would also add, and correct me if I'm wrong, that line arrays are designed specifically for nearfield listening whereas point sources can be nearfield or farfieled. This usually isn't an issue since the speakers are so tall... all but the largest rooms stay withing the nearfield. Having said that, line arrays are theoretically designed to be in phase at a particular depth. Lateral seating isn't as critical as how far you are from speakers. I would imagine "the depth of clarity" (my own phrase ) depends on how well the crossover is designed. Given the above statements and the shear amount of dynamics, line arrays can do wonders in a single row home theater.  Most people agree in that situation the imaging is so spectacular that you don't need a center channel. Moreover, it would rather difficult to integrate one with the line arrays anyways. From what I've gathered, line arrays also need a wide room to really get their wide sweet spot. The height of the room doesn't matter very much do to the previously mentioned cylindrical dispersion pattern. Also, since there are so many speakers in a line array, many modes are excited and thus you get a more uniform sound throughout the room. If you get a line array with XBL tech, the benefits of those acoustics should extend to 30Hz or even below. With that many drivers with that extension, a subwoofer would only be necessary for the craziest of people! This would also decrease (though never eliminate) the need for passive acoustic room treatments.

Bob... a quick question. You mentioned the problem of overly large imaging. Decreasing the output of the outer drivers makes sense, but wouldn't that also increase the vertical dispersion of the speakers? I'm sure it's worth the tradeoff even if it does.

I'd like to add a few thoughts to your post. Actually, I prefer a center channel for home theater since my listening/home theater room has seating spread clear across the room. The dialogue from the center channel is then anchored to the screen a bit better. If you have a more normal seating position, a center could become optional. Centers are no harder to integrate with line arrays than point sources. Surround speakers are also easy to integrate. Nearfield listening seems to help integration.

Power tapering does control image size and make it life like without being over blown. Very realistic! Line arrays work well in just about any size room. My arrays are only 16" from the sidewalls and they image like crazy. Open would be better but smaller rooms are not show stoppers.

Jim

[klh]

That's good to know about center and surround imaging. What your saying makes sense. Other people have posted problems with integration... namely the 3dB vx 6dB dropoff and less dynamics from point source centers and surrounds. The first is easy to take care of if you level match for a specific distance. The second is a little more difficult to deal with. Basically it's been posted that the center and surrounds are drowned out during loud scenes and too loud during quiet ones. Like all things audio it probably just depends on how sensitive one is to that type of thing. As for the speaks being close to the side walls... a little absorption is a beautiful thing!

[jholtz]

That's good to know about center and surround imaging. What your saying makes sense. Other people have posted problems with integration... namely the 3dB vx 6dB dropoff and less dynamics from point source centers and surrounds. The first is easy to take care of if you level match for a specific distance. The second is a little more difficult to deal with. Basically it's been posted that the center and surrounds are drowned out during loud scenes and too loud during quiet ones. Like all things audio it probably just depends on how sensitive one is to that type of thing. As for the speaks being close to the side walls... a little absorption is a beautiful thing!

You're exactly correct about the different roll off rates of point source/line source. It doesn't seem to be an issue in my situation since the speakers are volume balanced to be exactly the same at the seating position. I use an Audio Refinement Pre/pro for both music and home theater with a RWA modified Squeezebox as the source component for music.

Dialogue is crystal clear (also a Selah Audio designed speaker) in my center channel and is never over powered by the line arrays. Panning is perfect and dynamics are incredible on exciting movies.  I love them!

Jim

[seadogs1]

Thanks for all the replies. There seem to be only line array proponents out there surely someone can speak to the point source side? Pardon my ignorance but what is XBL Tech? What brands are there that are line array?

[klh]

Selah Audio and GR Research make line arrays. Rick Craig at Selah has his standard designs (but there is nothing "standard" about them). He also does a lot of custom work... if you want something made, he can make it. Dannie Richie at GR Research does line arrays with his own line of woofers, one of which has XBL technology. XBL technology allows for much greater excursion of the woofers while maintaining low distortion which thus allows the speakers to better reproduce the frequencies at its lower limit. It won't make the speakers reproduce frequencies it wouldn't reproduce without XBL technology, it just makes them reproduce them better (sound familiar?). That isn't just hype. Unfortunately Danny's line array with XBL tech hasn't been released as of yet. Both GR Research and Selah Audio have circles at this website. Al Wooley at Raw Acoustics sold line arrays in the past... and Raw too has a circle here. His line arrays also use XBL tech, but I'm not sure if he is still making them. I would check out all three circles.

[Rick Craig]

I would also add, and correct me if I'm wrong, that line arrays are designed specifically for nearfield listening whereas point sources can be nearfield or farfieled. This usually isn't an issue since the speakers are so tall... all but the largest rooms stay withing the nearfield. Having said that, line arrays are theoretically designed to be in phase at a particular depth. Lateral seating isn't as critical as how far you are from speakers. I would imagine "the depth of clarity" (my own phrase ) depends on how well the crossover is designed. Given the above statements and the shear amount of dynamics, line arrays can do wonders in a single row home theater.  Most people agree in that situation the imaging is so spectacular that you don't need a center channel. Moreover, it would rather difficult to integrate one with the line arrays anyways. From what I've gathered, line arrays also need a wide room to really get their wide sweet spot. The height of the room doesn't matter very much do to the previously mentioned cylindrical dispersion pattern. Also, since there are so many speakers in a line array, many modes are excited and thus you get a more uniform sound throughout the room. If you get a line array with XBL tech, the benefits of those acoustics should extend to 30Hz or even below. With that many drivers with that extension, a subwoofer would only be necessary for the craziest of people! This would also decrease (though never eliminate) the need for passive acoustic room treatments.

Bob... a quick question. You mentioned the problem of overly large imaging. Decreasing the output of the outer drivers makes sense, but wouldn't that also increase the vertical dispersion of the speakers? I'm sure it's worth the tradeoff even if it does.

XBL doesn't make much sense in an array because there's very little excursion of the woofers to make use of the technology (constant BL vs. excursion). From my tests the XBL motor has a significant flaw that makes it a non-starter for most applications. I'm not the only one with this opinion either 

[klh]

Rick... please elaborate. I've heard something of this mentioned by others, too, but I've read nothing beyond vague statements. BTW, I don't doubt you. I'm just curious.

[Rick Craig]

Thanks for all the replies. There seem to be only line array proponents out there surely someone can speak to the point source side? Pardon my ignorance but what is XBL Tech? What brands are there that are line array?

Most line arrays are 2-way designs and still have a few tradeoffs that are a part of any 2-way design, regardless of the number of drivers. Given similar driver quality a good 3-way or 4-way floorstanding point source can have better tonality because the drivers are operated more conservatively. Bass extension can also be better with the point source if you're running the typical 4"-7" array drivers versus a 10" or 12" in the point source. Unless you're running multiple large woofers in your point source then the array will still move more air and have greater dynamic ability. If you add a DEQX or other front end equipment that can extend (EQ) the bass then an array with 7" woofers can be pretty impressive down to the bottom octave.

Point source speakers are better for smaller rooms where the side walls are fairly close to the speakers. I've found that arrays can still sound pretty good in smaller rooms but the sense of envelopment that makes them so appealing is not as apparent.

[Rick Craig]

Rick... please elaborate. I've heard something of this mentioned by others, too, but I've read nothing beyond vague statements. BTW, I don't doubt you. I'm just curious.

The high Qes (lack of motor strength) seems to be the problem. This results in poorly defined bass and lower sensitivity. You can make the cone lighter to help alleviate this but then you end up with a driver that has mediocre bass extension.

[Rick Craig]

I would also add, and correct me if I'm wrong, that line arrays are designed specifically for nearfield listening whereas point sources can be nearfield or farfieled. This usually isn't an issue since the speakers are so tall... all but the largest rooms stay withing the nearfield. Having said that, line arrays are theoretically designed to be in phase at a particular depth. Lateral seating isn't as critical as how far you are from speakers. I would imagine "the depth of clarity" (my own phrase ) depends on how well the crossover is designed. Given the above statements and the shear amount of dynamics, line arrays can do wonders in a single row home theater.  Most people agree in that situation the imaging is so spectacular that you don't need a center channel. Moreover, it would rather difficult to integrate one with the line arrays anyways. From what I've gathered, line arrays also need a wide room to really get their wide sweet spot. The height of the room doesn't matter very much do to the previously mentioned cylindrical dispersion pattern. Also, since there are so many speakers in a line array, many modes are excited and thus you get a more uniform sound throughout the room. If you get a line array with XBL tech, the benefits of those acoustics should extend to 30Hz or even below. With that many drivers with that extension, a subwoofer would only be necessary for the craziest of people! This would also decrease (though never eliminate) the need for passive acoustic room treatments.

Bob... a quick question. You mentioned the problem of overly large imaging. Decreasing the output of the outer drivers makes sense, but wouldn't that also increase the vertical dispersion of the speakers? I'm sure it's worth the tradeoff even if it does.

I've found the listening distance can be pretty flexible with an array but I prefer to be about 8-12 ft. away in my room. There's not a sharp transition in phase that would limit you to one sweetspot distance. I've talked to some people that actually like to be really close, say 4-5 ft. away. Like any speaker you can experiment to find what works best for you.

[Danny Richie]

The high Qes (lack of motor strength) seems to be the problem. This results in poorly defined bass and lower sensitivity. You can make the cone lighter to help alleviate this but then you end up with a driver that has mediocre bass extension.

Actually this isn't true at all. Just like any other woofer you can hang as much or as little motor structure on it as you like and hit any figures that you want.

Now you do have to use a larger motor structure to hit the same figures as the same woofer with a more typical motor design, but having to hang a slightly larger magnet on it is not a problem.

The XBL^ motor stays more linear and maintains a more constant BL factor. Distortion remains lower and low bass extension is improved.

[Rick Craig]

The high Qes (lack of motor strength) seems to be the problem. This results in poorly defined bass and lower sensitivity. You can make the cone lighter to help alleviate this but then you end up with a driver that has mediocre bass extension.

Actually this isn't true at all. Just like any other woofer you can hang as much or as little motor structure on it as you like and hit any figures that you want.

Now you do have to use a larger motor structure to hit the same figures as the same woofer with a more typical motor design, but having to hang a slightly larger magnet on it is not a problem.

The XBL^ motor stays more linear and maintains a more constant BL factor. Distortion remains lower and low bass extension is improved.

But your own curve for the M130X shows the same response problem I noticed with the Extremis 6.8   - maybe it's something more than a Qes issue ? 

And by the way, I would've been happy to use the Extremis because it would've cost me less than most of the other 7" drivers I've used 

[Danny Richie]

But your own curve for the M130X shows the same response problem

Lower sensitivity is not a response problem. The response is great. It's as smooth as glass. 

The lower sensitivity is deceptive though. The response can mirror image the baffles step loss of a standard sized box. With the standard M-130 I wind up with about 87db sensitivity in an application like the A/V-1. With the XBL^ version I will wind up with a sensitivity of about 86db in the same application.

And by the way, I would've been happy to use the Extremis because it would've cost me less than most of the other 7" drivers I've used 

My issues with that driver is simply how it sounds. That plastic cone driver just doesn't do mid-range justice for me. The response is a little on the rough side for me too. But it does make a killer little sub driver.

[Rick Craig]

But your own curve for the M130X shows the same response problem

Lower sensitivity is not a response problem. The response is great. It's as smooth as glass. 

The lower sensitivity is deceptive though. The response can mirror image the baffles step loss of a standard sized box. With the standard M-130 I wind up with about 87db sensitivity in an application like the A/V-1. With the XBL^ version I will wind up with a sensitivity of about 86db in the same application.

And by the way, I would've been happy to use the Extremis because it would've cost me less than most of the other 7" drivers I've used 

My issues with that driver is simply how it sounds. That plastic cone driver just doesn't do mid-range justice for me. The response is a little on the rough side for me too. But it does make a killer little sub driver.

Actually I was referring to the peaking in the response curve from 300hz on down. I do understand that you're using that to counteract the baffle step but there's no free lunch