Stereo / Mono / Distributed Systems: Difference between revisions

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<div>

This article applies to using multiple {{L1}}s in various ways: Stereo, Mono, Distributed Systems.

;Update: The following comments are equally applicable to the L1 Pro series of products (PRO8, PRO16, PRO32)

;Summary

*[[Dual Mono]] - keep the L1s 20 feet (6 meters) apart or more

*[[Multi Mono]] - every source is heard through only one L1, there are no issues

*Stereo (pre-recorded music), distance between the systems is less critical because you are not sending identical signals to ~~two~~ multiple systems

*Stereo (pre-recorded music), the distance between the systems is less critical because you are not sending identical signals to multiple systems

</div>

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=== Stereo ===

The following applies to all L1 and L1 Pro systems

Question:

:The Compact looks really attractive as a lightweight solution for running stereo. Are there any special considerations for doing this? I am looking for differences from the way we might have approached this with the other L1® models

Answer:

Ever since the L1 approach was introduced in 2003, we've had a vibrant discussion here about the subject of instruments that work in stereo -- predominantly keyboards and occasionally guitar (Adrian Belew, Pat Metheny for example).

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* There are many reasons a player would want to hear his or her instrument in stereo. Having different sounds come from different directions can be very exciting sonically and I doubt there's much controversy about that.

* An L1 system can project a wide stereo field on stage and into the audience -- particularly the Model I and ~~the~~ Model II. Because the ~~I and II~~ are essentially 14' line arrays (7' speaker with a 7' mirror image source created by the floor reflection) they project sound at much less loss with distance than a conventional speaker. This has the effect of greatly enhancing the size of the stereo field.

* An L1 system can project a wide stereo field on stage and into the audience -- particularly the L1 Pro32, L1 Model I and L1 Model II. Because the these are essentially 14' line arrays (7' speaker with a 7' mirror image source created by the floor reflection) they project sound at much less loss with distance than a conventional speaker. This has the effect of greatly enhancing the size of the stereo field.

* It's a mistake to place stereo speakers too closely together. Not only does the area over which listeners hear stereo sound shrink but you can get undesirable interference effects caused when the same (or very nearly the same) signal is played simultaneously through two or more like speakers. (Multi-source interference can cause audible dropouts in tone.)

* For these reasons, I'd recommend spacing L1 systems used for stereo at least 10' apart. There are competing interests here. A player located too close to one of the L1 systems spaced too far apart won't hear stereo — but his or her audience will. On the other hand, space the L1 systems closer so that the player gets stereo and you won't project stereo to the audience.

* For these reasons, I'd recommend spacing L1 systems used for stereo at least 10' apart. There are competing interests here. A player located too close to one of the L1 systems spaced too far apart won't hear stereo — but his or her audience will. On the other hand, space the L1 systems closer so that the player gets stereo, and you won't project stereo to the audience.

* A player located roughly between two spaced L1 systems will hear stereo well and many in the audience will too. 10-20' feels good to me for this kind of setup although I don't want to have this come across as more than a rule of thumb.

* A player located roughly between two spaced L1 systems will hear stereo well, and many in the audience will too. 10-20' feels good to me for this kind of setup, although I don't want to have this come across as more than a rule of thumb.

* The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model I}}. As a result, it doesn't project sound as far. Said another way, the level falls off more rapidly with distance on the Compact. As a consequence, the stereo field won't be quite as large. This will translate I think to a smaller stereo sweet area for the player and for the audience. On the other hand, as has recently been pointed out on this forum, a player can buy two L1 Compacts for the price of one L1 Model I and can buy three for the price of a Model II and a T1 ToneMatch engine. For those that value a stereo instrumental sound, experimentation with the various L1 models is encourage.

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=== Mono ===

; Note :References to the L1 Compact are also applicable to the L1 Pro8

Question:

:I noticed in the {{Compact Owners Guide}} (page 7), there are instructions on how to use more than one Compact to provide additional coverage in larger spaces. This is new. It hasn't been easy to do this with the {{Classic}} / {{Model I}} / {{Model II}}.

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* I can't think of a situation like this where you would want to space the {{Compact}}s (or any other {{L1 nl}} system) closer than 20' and thus I see no issue with undesirable [[Multiple Source Interference|multi-source interference]]. I think that spacing closer to the 50' mark would be more typical in terms of covering large audiences. Said another way, I don't think an {{Compact}} has trouble throwing up to 50'.

* As said above "The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model II}}. As a result, it doesn't project sound as far." Thus, spacing of multiple {{Compact}}s would be somewhat less than the spacing of multiple Model I or Model II systems.

* As said above "The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model II}}. As a result, it doesn't project sound as far." Thus, the spacing of multiple {{Compact}}s would be somewhat less than the spacing of multiple Model I or Model II systems.

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==== Two {{L1}}s in Mono ====

~~How much gain do you get when you run two L1® with the same source.~~

~~~~

:The most you can ever get from putting two sources fed by the same signal together is 6 dB. The reason? sound waves add in space through the principle of superposition. If the waves from two sources perfectly add, you get twice the amplitude, which is 6 dB. Now, I've been proven wrong on a number of occasions, but if that happens on this occasion, Alan, the sound engineer you've been talking to is going to get a Nobel Prize.

:The problem is that to get the full 6 dB the two sources have to be spaced very closely together relative to a wavelength of sound. at 50 Hz, where the wavelength of sound is about 20' (about 7 meters) that's pretty easy to do. Massing your B1 bass modules is done for this reason -- to get the 6 dB per doubling of B1 systems. But at 1,000 Hz, where the wavelengths are 1' (about 30 cm) you just can't do get L1 speakers close enough. As a result, you get something less than 6 dB because at some angles instead of the sound waves constructively adding they will destructively cancel (one will be partly or completely out of phase with the other.

:Once you separate the sources by several or more wavelengths, the summations and cancellations are so numerous and so complex that we say the two sources are essentially uncorrelated (not strictly true, but for the purposes of this argument, a very close approximation.) When two sources are uncorrelated the only thing you can count on is that the total amount of acoustic power going into the room will be doubled. Doubling the power is 3 dB.

~~:So what we've said is~~

~~# put B1s together if you can because they'll give you an honest 6 dB per doubling of B1 systems;~~

~~# if you are sending a mono or stereo signal to spaced L1 systems, try to space them 20' (7m) or more if you can because this will minimize any audible cancellations.~~

:Alan, you've got enough spacing of your L1 systems and so I really don't see any problem with destructive interference. On the other hand, given the maximum benefit in level is only 3 dB, and you are somewhat reducing the clarity and accuracy of localization, I question the benefit. Your willingness to experiment is a good ingredient.

~~:I'm going to work next week on a Wiki article on this subject, someplace where I can try to put these thoughts together where they can be found time and time a again.~~

~~[http://bose.infopop.cc/eve/forums/a/tpc/f/778102955/m/108102942?r=879106073#879106073 Source: Ken-at-Bose]~~

=== Distributed Systems for Covering a Large Area ===

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Yes, my instincts and experience tell me that this should be true -- say down to 10' -- but I haven't done a clean experiment to prove it to myself, so some caution is advised.

And I'll point out that below say 200 Hz, all the L1 systems are essentially omnidirectional and the spacing of 10, 20, or even 30' can create an audible "power alley". Once you get beyond these distances, the balloon animal has so many closely spaced bulges and creases -- even at lower frequencies -- that our ear doesn't hear them individually but rather hears the average. The [[{{PAGENAME}}#Balloon Animal|balloon animal]] turns into something more like a Japanese fan.

And I'll point out that below say 200 Hz, all the L1 systems are essentially omnidirectional and the spacing of 10, 20, or even 30' can create an audible "power alley"<ref>Related reading: [[Media:The-Subwoofer-Power-Alley-1.pdf]]</ref>. Once you get beyond these distances, the balloon animal has so many closely spaced bulges and creases -- even at lower frequencies -- that our ear doesn't hear them individually but rather hears the average. The [[{{PAGENAME}}#Balloon Animal|balloon animal]] turns into something more like a Japanese fan.

[http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/756102391?r=801102491#801102491 Source: Ken-at-Bose]

~~=== Delay and Mono ===~~

~~Question:~~

~~:Would a few ms delay be enough to avoid the "interference" from dual mono?<br />Do you have a value for the latency when daisy chaining Compacts?~~

~~Answer:~~

Pure delay does nothing to fix interference "globally" (I'll explain) but can be used "locally". In this case (L1 systems, spaced, all getting the same signal) I believe delay will turn out to be not useful.

==== Balloon Animal ====

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[http://bose.infopop.cc/eve/forums/a/tpc/f/3976055944/m/900104591?r=190102491#190102491 Source: Ken-at-Bose]

=== Delay and Mono ===

Question:

:Would a few ms delay be enough to avoid the "interference" from dual mono?<br />Do you have a value for the latency when daisy chaining Compacts?

Answer:

Pure delay does nothing to fix interference "globally" (I'll explain) but can be used "locally". In this case (L1 systems, spaced, all getting the same signal) I believe delay will turn out to be not useful.

----

[[Category:Stereo]]

[[Category:Mono]]

@@ Line 1: / Line 1: @@
+{{Bose Reviewed}}
 <div class="tocdiv">
      <div>__TOC__</div>
      <div>
 This article applies to using multiple {{L1}}s in various ways: Stereo, Mono, Distributed Systems.
+;Update: The following comments are equally applicable to the L1 Pro series of products (PRO8, PRO16, PRO32)
 ;Summary
 *[[Dual Mono]] - keep the L1s 20 feet (6 meters) apart or more
 *[[Multi Mono]] - every source is heard through only one L1, there are no issues
-*Stereo (pre-recorded music), distance between the systems is less critical because you are not sending identical signals to two multiple systems
+*Stereo (pre-recorded music), the distance between the systems is less critical because you are not sending identical signals to multiple systems
      </div>
 </div>
@@ Line 13: / Line 15: @@
 === Stereo ===
+The following applies to all L1 and L1 Pro systems
 Question:
 :The Compact looks really attractive as a lightweight solution for running stereo. Are there any special considerations for doing this? I am looking for differences from the way we might have approached this with the other L1® models
 Answer:
 Ever since the L1 approach was introduced in 2003, we've had a vibrant discussion here about the subject of instruments that work in stereo -- predominantly keyboards and occasionally guitar (Adrian Belew, Pat Metheny for example).
@@ Line 24: / Line 27: @@
 * There are many reasons a player would want to hear his or her instrument in stereo. Having different sounds come from different directions can be very exciting sonically and I doubt there's much controversy about that.
-* An L1 system can project a wide stereo field on stage and into the audience -- particularly the Model I and the Model II. Because the I and II are essentially 14' line arrays (7' speaker with a 7' mirror image source created by the floor reflection) they project sound at much less loss with distance than a conventional speaker. This has the effect of greatly enhancing the size of the stereo field.
+* An L1 system can project a wide stereo field on stage and into the audience -- particularly the L1 Pro32, L1 Model I and L1 Model II. Because the these  are essentially 14' line arrays (7' speaker with a 7' mirror image source created by the floor reflection) they project sound at much less loss with distance than a conventional speaker. This has the effect of greatly enhancing the size of the stereo field.
 * It's a mistake to place stereo speakers too closely together. Not only does the area over which listeners hear stereo sound shrink but you can get undesirable interference effects caused when the same (or very nearly the same) signal is played simultaneously through two or more like speakers. (Multi-source interference can cause audible dropouts in tone.)
-* For these reasons, I'd recommend spacing L1 systems used for stereo at least 10' apart. There are competing interests here. A player located too close to one of the L1 systems spaced too far apart won't hear stereo &mdash;  but his or her audience will. On the other hand, space the L1 systems closer so that the player gets stereo and you won't project stereo to the audience.
+* For these reasons, I'd recommend spacing L1 systems used for stereo at least 10' apart. There are competing interests here. A player located too close to one of the L1 systems spaced too far apart won't hear stereo &mdash;  but his or her audience will. On the other hand, space the L1 systems closer so that the player gets stereo, and you won't project stereo to the audience.
-* A player located roughly between two spaced L1 systems will hear stereo well and many in the audience will too. 10-20' feels good to me for this kind of setup although I don't want to have this come across as more than a rule of thumb.
+* A player located roughly between two spaced L1 systems will hear stereo well, and many in the audience will too. 10-20' feels good to me for this kind of setup, although I don't want to have this come across as more than a rule of thumb.
 * The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model I}}. As a result, it doesn't project sound as far. Said another way, the level falls off more rapidly with distance on the Compact. As a consequence, the stereo field won't be quite as large. This will translate I think to a smaller stereo sweet area for the player and for the audience. On the other hand, as has recently been pointed out on this forum, a player can buy two L1 Compacts for the price of one L1 Model I and can buy three for the price of a Model II and a T1 ToneMatch engine. For those that value a stereo instrumental sound, experimentation with the various L1 models is encourage.
@@ Line 37: / Line 40: @@
 === Mono ===
+; Note :References to the L1 Compact are also applicable to the L1 Pro8
 Question:
 :I noticed in the {{Compact Owners Guide}} (page 7), there are instructions on how to use more than one Compact to provide additional coverage in larger spaces. This is new. It hasn't been easy to do this with the {{Classic}} / {{Model I}} / {{Model II}}.
@@ Line 51: / Line 56: @@
 * I can't think of a situation like this where you would want to space the {{Compact}}s (or any other {{L1 nl}} system) closer than 20' and thus I see no issue with undesirable [[Multiple Source Interference|multi-source interference]]. I think that spacing closer to the 50' mark would be more typical in terms of covering large audiences. Said another way, I don't think an {{Compact}} has trouble throwing up to 50'.
-* As said above "The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model II}}. As a result, it doesn't project sound as far." Thus, spacing of multiple {{Compact}}s would be somewhat less than the spacing of multiple Model I or Model II systems.
+* As said above "The {{Compact}} uses a significantly shorter array than the {{Model I}} or {{Model II}}. As a result, it doesn't project sound as far." Thus, the spacing of multiple {{Compact}}s would be somewhat less than the spacing of multiple Model I or Model II systems.
@@ Line 58: / Line 63: @@
 ==== Two {{L1}}s in Mono ====
-How much gain do you get when you run two L1® with the same source.
+{{Two L1 Systems}}
-<!--This is an excerpt from a recent post from Ken-at-Bose. He will be updating this soon. -->
-:The most you can ever get from putting two sources fed by the same signal together is 6 dB. The reason? sound waves add in space through the principle of superposition. If the waves from two sources perfectly add, you get twice the amplitude, which is 6 dB. Now, I've been proven wrong on a number of occasions, but if that happens on this occasion, Alan, the sound engineer you've been talking to is going to get a Nobel Prize.
-:The problem is that to get the full 6 dB the two sources have to be spaced very closely together relative to a wavelength of sound. at 50 Hz, where the wavelength of sound is about 20' (about 7 meters) that's pretty easy to do. Massing your B1 bass modules is done for this reason -- to get the 6 dB per doubling of B1 systems. But at 1,000 Hz, where the wavelengths are 1' (about 30 cm) you just can't do get L1 speakers close enough. As a result, you get something less than 6 dB because at some angles instead of the sound waves constructively adding they will destructively cancel (one will be partly or completely out of phase with the other.
-:Once you separate the sources by several or more wavelengths, the summations and cancellations are so numerous and so complex that we say the two sources are essentially uncorrelated (not strictly true, but for the purposes of this argument, a very close approximation.) When two sources are uncorrelated the only thing you can count on is that the total amount of acoustic power going into the room will be doubled. Doubling the power is 3 dB.
-:So what we've said is
-# put B1s together if you can because they'll give you an honest 6 dB per doubling of B1 systems;
-# if you are sending a mono or stereo signal to spaced L1 systems, try to space them 20' (7m) or more if you can because this will minimize any audible cancellations.
-:Alan, you've got enough spacing of your L1 systems and so I really don't see any problem with destructive interference. On the other hand, given the maximum benefit in level is only 3 dB, and you are somewhat reducing the clarity and accuracy of localization, I question the benefit. Your willingness to experiment is a good ingredient.
-:I'm going to work next week on a Wiki article on this subject, someplace where I can try to put these thoughts together where they can be found time and time a again.
-[http://bose.infopop.cc/eve/forums/a/tpc/f/778102955/m/108102942?r=879106073#879106073 Source: Ken-at-Bose]
 === Distributed Systems for Covering a Large Area ===
@@ Line 93: / Line 80: @@
 Yes, my instincts and experience tell me that this should be true -- say down to 10' -- but I haven't done a clean experiment to prove it to myself, so some caution is advised.
-And I'll point out that below say 200 Hz, all the L1 systems are essentially omnidirectional and the spacing of 10, 20, or even 30' can create an audible "power alley". Once you get beyond these distances, the balloon animal has so many closely spaced bulges and creases -- even at lower frequencies -- that our ear doesn't hear them individually but rather hears the average. The [[{{PAGENAME}}#Balloon Animal|balloon animal]] turns into something more like a Japanese fan.
+And I'll point out that below say 200 Hz, all the L1 systems are essentially omnidirectional and the spacing of 10, 20, or even 30' can create an audible "power alley"<ref>Related reading: [[Media:The-Subwoofer-Power-Alley-1.pdf]]</ref>. Once you get beyond these distances, the balloon animal has so many closely spaced bulges and creases -- even at lower frequencies -- that our ear doesn't hear them individually but rather hears the average. The [[{{PAGENAME}}#Balloon Animal|balloon animal]] turns into something more like a Japanese fan.
 [http://bose.infopop.cc/eve/forums/a/tpc/f/7521050644/m/756102391?r=801102491#801102491 Source: Ken-at-Bose]
-=== Delay and Mono ===
-Question:
-:Would a few ms delay be enough to avoid the "interference" from dual mono?<br />Do you have a value for the latency when daisy chaining Compacts?
-Answer:
-Pure delay does nothing to fix interference "globally" (I'll explain) but can be used "locally". In this case (L1 systems, spaced, all getting the same signal) I believe delay will turn out to be not useful.
 ==== Balloon Animal ====
@@ Line 124: / Line 104: @@
 [http://bose.infopop.cc/eve/forums/a/tpc/f/3976055944/m/900104591?r=190102491#190102491 Source: Ken-at-Bose]
+=== Delay and Mono ===
+Question:
+:Would a few ms delay be enough to avoid the "interference" from dual mono?<br />Do you have a value for the latency when daisy chaining Compacts?
+Answer:
+Pure delay does nothing to fix interference "globally" (I'll explain) but can be used "locally". In this case (L1 systems, spaced, all getting the same signal) I believe delay will turn out to be not useful.
 ----
 [[Category:Stereo]]
 [[Category:Mono]]