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  #211  
Old 01-20-2010, 12:03 AM
aboutjack aboutjack is offline
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Quote:
Originally Posted by DrDavid View Post
Hi Kramster,

Exactly. Those are some of my concerns, too.

Maybe Jack will weigh in here on the issue of vertical dispersion, in venues where the BagAmp cannot be placed at ear level for all audience members.
Me? Weigh in?... Dunno... I'm pretty shy.

1. The taller the array the more pronounced the "array effect" of widened horizontal dispersion and narrowed vertical dispersion.

2. Ditto for the narrower the aspect ratio. This is different than physical height.

3. Also in play here is the complicating fact that smaller drivers produce wider dispersion patterns than larger drivers.

Crazily, you could stack four two-foot speakers vertically and technically call it an 8-foot high line array. However, the aspect ratio of the array would only be 4:1. The array effect would be minimal.

Alternately, you could stack 48 two-inch (full range) drivers to get the same 8-foot array height. But, your aspect ratio would then be 24:1, and the line array effect would be as near-perfect as you'll ever achieve in real life.

In this case, "near perfect" means the top of the upper driver would define a horizontal plane above which nearly no sound was projected. The bottom driver would also define the lower limit horizontal plane, below which effectively no sound would propagate. And, to the sides, SPL drop at 180-degrees would be negligible -- virtually the same as dead center, on-axis.

With the first example -- four two-foot drivers -- mostly none of that occurs, and you'd still essentially have a point source loudspeaker system, with a spherical drop off pattern in SPL, generally the same SPL drop off vertically and horizontally.

So, given that array height and array aspect ratio impact the dispersion characteristics, those engineering decisions define the way the product eventually performs in real life.

Bose chose a super tall and very narrow aspect ratio approach, and the L1 behaves that way: a super tight array effect -- ultra wide, with eerily chopped output above and below the end drivers... creating a 6-foot tall "slice" of sound going out at an audience. Anyone whose ears are within that vertical 6-foot space will hear a near-perfect 3dB SPL drop per doubling of distance effect of a line array. Anyone whose ears are above the top of the slice or below the bottom of the slice will hear virtually nothing. Really.

Go to store selling the L1, turn it on, walk away and stick your head above and below the "slice" and hear this for yourself. It's truly weird. Where'd the sound go?

Fishman chose to use a much shorter array with wider drivers, and then plop a tweeter in the middle that decouples the top three drivers from the bottom three drivers. While there's no published and agreed definition for this, I don't consider anything under an 8:1 aspect ratio as a line array, as the effect is minimal. The SA220 has a pair of closely located arrays (one above and below the tweeter) of about 2.5:1 aspect ratio -- very nearly a couple of simple point source loudspeaker systems. So, there is very little array effect at play. The wider horizontal dispersion of the product mostly results from simply using small drivers, not from an array effect. Go figure.

In deciding the physical approach to the BagAmp, I wanted to avoid the tunnel like effect of a near-perfect array (Bose), but still benefit from some substantial throw improvement that a line array can create. So, I compromised by using eight three-inch drivers, for an array height of about 26-inches with a width of 3-inches, for an aspect ratio of about 8.5:1 or so.

So, BagAmp is intentionally not a super aggressive line array design. Why?

I don't want people to have to "aim" my product in situations where some people may be a little above the top driver or below the bottom driver. I wanted a set it up and just use it sort of product. The result is much better than a point source speaker's throw, but without the sci-fi level tweekiness of the Bose array "slice." I consider the L1 effect too much of a good thing for most real-world small venues. There *will* be heads above and below that perfect six foot high slice of sound in many coffee houses, small clubs, juke joints, auditoriums, ballrooms, etc.

So, that's the poop on why and how on the line array effect with the three products in discussion. I left out the L1 Compact, as it twists (rotates) the drivers, breaking the plane of projection, and isn't a line array at all. It, like the Fishman, benefits in slightly wider than typical dispersion simply by using small drivers.

And, of course since I don't have a Ph.D. in acoustic engineering (by one poster's implications), you can accept or reject any of this as you see fit.

Last edited by aboutjack; 01-20-2010 at 12:26 AM.
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  #212  
Old 01-20-2010, 12:26 AM
DrDavid DrDavid is offline
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Well, Jack, thank you very much indeed for taking the time to write all of that. I, for one, find it extremely interesting and informative.

Sounds to me like your "compromise" decision on the BagAmp's design is sensible and well-considered, given the physics of line arrays you have explained, and the intended application of the BagAmp in relatively small venues, with audiences who won't necessarily be "staying put" either horizontally or vertically!

Thanks again.
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  #213  
Old 01-20-2010, 12:33 AM
aboutjack aboutjack is offline
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Quote:
Originally Posted by DrDavid View Post
Well, Jack, thank you very much indeed for taking the time to write all of that. I, for one, find it extremely interesting and informative.

Sounds to me like your "compromise" decision on the BagAmp's design is sensible and well-considered, given the physics of line arrays you have explained, and the intended application of the BagAmp in relatively small venues, with audiences who won't necessarily be "staying put" either horizontally or vertically!

Thanks again.
As with any audio product, the result is merely the manifestation of the design decisions made early in the process. Line arrays are tricky beasts... just ask any pro sound guy who does architectural arrays (churches, auditoriums, public spaces, etc.) and he'll quickly verify the complexities and trade offs involved.

Perhaps the clearest example of how implementation of an array impacts the dispersion behavior is a church with a balcony. In these facilities you typically see two sets of arrays -- one set is about the height of the ground floor seating area, tall enough to catch the tallest ears in the back. The other is separated a bit, above those units, and mates to the listening height needed to cover the ears in the balcony -- basically two separate vertical line arrays to cover one room.

Super long and narrow arrays like that really do put out almost no sound above the tallest driver and below the lowest driver. "Slice" is the best word I have found to convey the thought.
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  #214  
Old 01-20-2010, 06:23 PM
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I for one would be very interested in BA or SA type system with no verb,eq, or FX . Just clean amp to speakers . So as to use my relatively nice outboard front end .
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  #215  
Old 01-20-2010, 07:08 PM
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Quote:
Originally Posted by KevWind View Post
I for one would be very interested in BA or SA type system with no verb,eq, or FX . Just clean amp to speakers . So as to use my relatively nice outboard front end .
+1! Basically, just an active speaker array that can take a good hot full signal from an outboard front-end stocked with quality gear. As they say on the street, "It don't get any better than that!"

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Last edited by SpruceTop; 01-21-2010 at 08:43 AM.
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  #216  
Old 01-20-2010, 07:12 PM
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Jack, I just want to add my voice thanking you for the extensive explanation of all these systems. I have to admit that much of it is over my head... but its finally starting to make sense.

The only problem with all this information is that its giving me some serious "AAS." Dang, another thing to save up money for. I'm really looking forward to hearing your BA when it comes out at Robb's in nearby Boulder. Till then, smooth travels and thanks again!
-jay
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  #217  
Old 01-20-2010, 08:45 PM
kramster kramster is offline
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Great explainin' Jack.. thanks.
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  #218  
Old 01-21-2010, 02:15 PM
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Looking on your site at the pic for the BA sub, Jack, it looks like it's designed to serve as a base for the BA tower, correct? It appears a mounting post is included with the sub. IOW, you wouldn't use the tripod when coupling with a sub cab?

I could see where a couple of those assemblies would serve well as a conventional FOH PA system.
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  #219  
Old 01-21-2010, 03:41 PM
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Default Correction regarding height of the Bose L1® Model I and Model II Line arrays

The Bose L1® Model I and Model II Cylindrical Radiators are closer to 7 feet than 6.

Model I is 83" (6 feet 11 inches) Source: L1® Model I

Model II is 84" (7 feet) Source: L1® Model II




Quote:
Originally Posted by aboutjack View Post
Me? Weigh in?... Dunno... I'm pretty shy.

1. The taller the array the more pronounced the "array effect" of widened horizontal dispersion and narrowed vertical dispersion.

2. Ditto for the narrower the aspect ratio. This is different than physical height.

3. Also in play here is the complicating fact that smaller drivers produce wider dispersion patterns than larger drivers.

Crazily, you could stack four two-foot speakers vertically and technically call it an 8-foot high line array. However, the aspect ratio of the array would only be 4:1. The array effect would be minimal.

Alternately, you could stack 48 two-inch (full range) drivers to get the same 8-foot array height. But, your aspect ratio would then be 24:1, and the line array effect would be as near-perfect as you'll ever achieve in real life.

In this case, "near perfect" means the top of the upper driver would define a horizontal plane above which nearly no sound was projected. The bottom driver would also define the lower limit horizontal plane, below which effectively no sound would propagate. And, to the sides, SPL drop at 180-degrees would be negligible -- virtually the same as dead center, on-axis.

With the first example -- four two-foot drivers -- mostly none of that occurs, and you'd still essentially have a point source loudspeaker system, with a spherical drop off pattern in SPL, generally the same SPL drop off vertically and horizontally.

So, given that array height and array aspect ratio impact the dispersion characteristics, those engineering decisions define the way the product eventually performs in real life.

Bose chose a super tall and very narrow aspect ratio approach, and the L1 behaves that way: a super tight array effect -- ultra wide, with eerily chopped output above and below the end drivers... creating a 6-foot tall "slice" of sound going out at an audience. Anyone whose ears are within that vertical 6-foot space will hear a near-perfect 3dB SPL drop per doubling of distance effect of a line array. Anyone whose ears are above the top of the slice or below the bottom of the slice will hear virtually nothing. Really.

Go to store selling the L1, turn it on, walk away and stick your head above and below the "slice" and hear this for yourself. It's truly weird. Where'd the sound go?

Fishman chose to use a much shorter array with wider drivers, and then plop a tweeter in the middle that decouples the top three drivers from the bottom three drivers. While there's no published and agreed definition for this, I don't consider anything under an 8:1 aspect ratio as a line array, as the effect is minimal. The SA220 has a pair of closely located arrays (one above and below the tweeter) of about 2.5:1 aspect ratio -- very nearly a couple of simple point source loudspeaker systems. So, there is very little array effect at play. The wider horizontal dispersion of the product mostly results from simply using small drivers, not from an array effect. Go figure.

In deciding the physical approach to the BagAmp, I wanted to avoid the tunnel like effect of a near-perfect array (Bose), but still benefit from some substantial throw improvement that a line array can create. So, I compromised by using eight three-inch drivers, for an array height of about 26-inches with a width of 3-inches, for an aspect ratio of about 8.5:1 or so.

So, BagAmp is intentionally not a super aggressive line array design. Why?

I don't want people to have to "aim" my product in situations where some people may be a little above the top driver or below the bottom driver. I wanted a set it up and just use it sort of product. The result is much better than a point source speaker's throw, but without the sci-fi level tweekiness of the Bose array "slice." I consider the L1 effect too much of a good thing for most real-world small venues. There *will* be heads above and below that perfect six foot high slice of sound in many coffee houses, small clubs, juke joints, auditoriums, ballrooms, etc.

So, that's the poop on why and how on the line array effect with the three products in discussion. I left out the L1 Compact, as it twists (rotates) the drivers, breaking the plane of projection, and isn't a line array at all. It, like the Fishman, benefits in slightly wider than typical dispersion simply by using small drivers.

And, of course since I don't have a Ph.D. in acoustic engineering (by one poster's implications), you can accept or reject any of this as you see fit.
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  #220  
Old 01-21-2010, 09:38 PM
jennconducts jennconducts is offline
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Photo of BagAmp booth at NAMM.

Jenn

http://www.flickr.com/photos/jennconducts/4293965797/
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  #221  
Old 01-21-2010, 10:34 PM
DavidE DavidE is offline
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Quote:
Originally Posted by KevWind View Post
I for one would be very interested in BA or SA type system with no verb,eq, or FX . Just clean amp to speakers . So as to use my relatively nice outboard front end .

Like a Bose L1?
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  #222  
Old 01-22-2010, 12:23 AM
lodi_55 lodi_55 is offline
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Quote:
Originally Posted by -ST- View Post
The Bose L1® Model I and Model II Cylindrical Radiators are closer to 7 feet than 6.

Model I is 83" (6 feet 11 inches) Source: L1® Model I

Model II is 84" (7 feet) Source: L1® Model II
Hmmm.. Good point, ST.. And when I gig, there are not many 7 footers in the audience.
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  #223  
Old 01-22-2010, 05:44 AM
kramster kramster is offline
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With the "big" Boses the 24 wee speakers go from about 10 inches to 7 feet so the very short and very tall get some easy enough.
The Compact with it speakers all up high yet all angle this way and that a wee-er person should be about 10 feet away from the tower to get it all. Or what I have done (though not recomended by Bose), ues one extension or even none.
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