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Dispersion questions (technical)

F

freos

Mar 5, 2009
10
0
#1
I have some DIY experience, and I'm up for more, and that's perfect since I just joined a second band. I'm thinking about building myself a lightweight 2x10 cab. I've been searching the forum and reading up on the vertical vs horizontal alignment and dispersion issues. I got a nice spreadsheet for Excel and some files from a friend and started simulating different designs.

So, here's why vertical alignment beats horizontal, this is a simulation of 2x Eminence Deltalite 10's 28 cm apart, listening distance of 2 meters plus 2 meters horizontal panning (45 degrees). Grey is horizontal alignment of drivers, and black vertical.
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Much more even projection of the mids. However, after studying the options, I realized that this is when the listener has their ear level with the bottom driver. If I lie down on the stage 45 degrees from the cab, I'll get great mids, but what happens while standing 45 degrees away?

As a guesstimate, I experimented with 130 cm listening height (height between centre of bottom driver and ear leaving room for ports and such). Here is the same graph as before, the difference being ear at 130 cm instead of 0 cm, everything else the same:
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Now both results seem crappy. As a final test, i tried a 45 degree configuration, the drivers 28 cm apart diagonally (20cm x 20 cm y), and here are the results at 2m distance, 2m pan, 1,3 m height - this time vertical is gray and diagonally is black:
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This is only true for one side of the cab. Panning 2m to the other side gives this result (vertical alignment is the same both ways):
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With the cab on the floor, diagonal alignment of the drivers seems to beat vertical, assuming the cab is on one side of the stage, and the bass player only moves away from it in one direction.

Any comments about this? Are my guesses correct, or am I talking out of my behind?

Sure, if you use the cabinet for PA with the drivers at ear level for the audience, and/or stack several cabs, vertical seems like the way to go, but when I play I only use my rig as a form of monitor for myself and the others on stage and let the PA make the sound for the audience, and I can always choose what side of the drums I want to put my rig.
 
#2
In your third graph you are actually somewhat on axis due to the angled drivers and your standing at an angle. If you stood directly in front of that third config you would probably be back to poor dispersion since the cab is still on the floor and it gets worse once you move to the other side of the stage. Once again you are nailed down to standing in one place on stage.

The solution in vertical alignment and a stand to get your cab up to ear level.
 
#3
Here's one of 2m straight in front of the speakers, no pan, 1,3m above center of bottom driver. Diagonal alignment is grey and vertical alignment is black.
[Invalid or Expired Link Removed]

I can't see why vertical would be better in that case.

What horizontal drivers does for the horizontal dispersion, vertical drivers does for the vertical dispersion, which I guess would mean issues when the speakers are not at ear level. In fact, while standing straight in front of the cab, horizontal alignment seems to be the better choice (if you always have the cab on the floor, always stand right in front of it and you are the only one who hears the cab - and I don't think that is the case for most of the bass players).

Still - from what I can see, diagonal alignment seems to beat vertical - with the cab on the floor and while standing in front or on the "good" side.
 
#4
At different heights you will have different apparent response with vertical orientation. So the 1.3m person hears one tone, and the 1.1m person hears another.

The important advantage to vertical orientation is that as people move in the horizontal plane, moving about the hall, they don't hear a change. If someone stands up, the tone may change.

In venues where people remain seated or standing, they get a consistent tone. Only where people stand and sit often will they hear a tonal difference as they change height.

See [Invalid or Expired Link Removed] for a graphical example of this. The demo shows the response as a top view for horizontal drivers. For vertical drivers, just visualize that response in the vertical plane.

Diagonal orientation would seem to provide the worst of both worlds: You'll still have tonal variation with the listeners' heights, and variation as they walk around the hall.
 
#5
To add to what Rick said, and to clarify my post, what you have in graph 3 is essentially vertical alignment when you stand 45 degrees off axis at a distance from the sound source equal to the height of your ears. That set of specific conditions is not going to happen in a live situation. Any time you move away from this point your sound will start to suck. Place your sound source--vertically, not diagonally aligned--up off the floor at ear level and you, your band mates, and everyone in the audience will be able to hear the best possible sound no matter where in the room they are standing.

The only reason diagonal driver alignment is ever used is to cram more speakers onto a small baffle.
 
#6
Rick Auricchio said:
At different heights you will have different apparent response with vertical orientation. So the 1.3m person hears one tone, and the 1.1m person hears another.

The important advantage to vertical orientation is that as people move in the horizontal plane, moving about the hall, they don't hear a change. If someone stands up, the tone may change.

In venues where people remain seated or standing, they get a consistent tone. Only where people stand and sit often will they hear a tonal difference as they change height.

See [Invalid or Expired Link Removed] for a graphical example of this. The demo shows the response as a top view for horizontal drivers. For vertical drivers, just visualize that response in the vertical plane.

Diagonal orientation would seem to provide the worst of both worlds: You'll still have tonal variation with the listeners' heights, and variation as they walk around the hall.
Click to expand...
+1. Additionally, as you move back and forth on stage with respect to the cab the angle of incidence can shift by 45 degrees or more, while out in the audience it will shift by no more than a few degrees. You can cure the first part of that equation by tilting the cab back.
As for diagonal alignments you'll get a different off-axis result to one side versus the other, but it's still a flawed and constantly changing response either way. Only with a vertical alignment does response remain uniform across the soundfield.
 
#7
All this presumes you play outside and have only one ear.
In the real world of a venue there are all kinds of reflection also cancelling eachother. Or re-enforcing each other.
And having 2 ears means that above say 2000 hertz the ears are more than 1 wavelenth apart so they may hear very different things.
 
#8
link wray said:
All this presumes you play outside and have only one ear.
In the real world of a venue there are all kinds of reflection also cancelling eachother. Or re-enforcing each other.
And having 2 ears means that above say 2000 hertz the ears are more than 1 wavelenth apart so they may hear very different things.
Click to expand...
All true, but if you start with crap and then add boundary issues you end up with even worse crap. Moreover, vertical sources have narrower vertical dispersion, and therefore are less influenced by the room than horizontal sources. The superiority of vertical alignments isn't a matter for debate, that question was settled before even I was born, let alone those of you not pushing 60. :D
 
#10
TwinTall2.jpg



:hmm: ... Convert all the bass players to vertical ... then you gotta work on the guitar guys!
 
#13
link wray said:
Guitar speakers cancelling each other is no problem. The more cancelling the better.
Click to expand...

+2 As long as the guitar is run through the PA the guitar players cab is perfectly designed to be a great directional monitor for the guitar player himself. No one else in the band wants to be blasted by a cab designed for good off axis response.

I guess the same would hold true for bass if you could count on the PA being capable of carrying the bass.
 
#16
NoGraveConcern said:
+2 As long as the guitar is run through the PA.
Click to expand...

Glad you can count on that ...

If you play a lot small venues 90% of the time there is no mic on the guitar cab! Around here (and we are a music town) only medium size venues up have a sound man and house system ... and most "working bands" carry a vocal only PA.

In the real world the whole off axis issue is not even on the radar screen of most players. Try to even talk to a guitar player about the subject and you will usually get either a blank stare, or NO way am I giving up my half-stack!


That said both me and my guitar player use vertical stacking.


:hmm: ... That leaves the other 97.652% that don't know or care.
 
#17
Kenny Allyn said:
Glad you can count on that ...

If you play a lot small venues 90% of the time there is no mic on the guitar cab! Around here (and we are a music town) only medium size venues up have a sound man and house system ... and most "working bands" carry a vocal only PA.

In the real world the whole off axis issue is not even on the radar screen of most players. Try to even talk to a guitar player about the subject and you will usually get either a blank stare, or NO way am I giving up my half-stack!


That said both me and my guitar player use vertical stacking.


:hmm: ... That leaves the other 97.652% that don't know or care.
Click to expand...


Oh, I've been to gigs with PA for vocals only. It turns into a guitar beam fest. No one can hear the guitar 2 feet to the side of the cab so they turn it up...and up...and up. :scowl:
 
#19
Kenny Allyn said:
On paper this is the dream setup ...
Click to expand...
Only if your name is Amar Bose and what you dream about every night is ever increasing profit margins. :hyper:

To say the least here's nothing wrong with a line array to cover the midbass and higher, a subwoofer to cover the lows, and digital signal processing to get the most utility out of the system, that's the basis of the PA systems used by every major pro-touring sound company. Scaling that concept down can work well for individual instruments, but not if you load the speakers with two dollar drivers and attempt to get from a two-way system what cannot be done with less than a three-way.

No, not that kind of three way. :crying:

Oh, I've been to gigs with PA for vocals only. It turns into a guitar beam fest. No one can hear the guitar 2 feet to the side of the cab so they turn it up...and up...and up.
Click to expand...
Not that bass players aren't guilty of the same thing, though you're less likely to get that when the rig is an 8x10 than something with half it's capability, simply because the 8x10 gets a few drivers up high enough so that the player can hear himself.
 
#20
NoGraveConcern said:
+2 As long as the guitar is run through the PA the guitar players cab is perfectly designed to be a great directional monitor for the guitar player himself. No one else in the band wants to be blasted by a cab designed for good off axis response.
Click to expand...

I find that a lot of the "blasting" that takes place, and the volume wars, proceed because of poor dispersion - especially on smaller stages. So I DO care about the guitarists's approach to backline, as well as the bassist's.

* * *

Kenny, thanks for your kind words the other day. Appreciated! : }
 

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