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[Jeff Lelko]

Hi all, so coming out of my recent choir adventure (documented here) I started thinking about the possibility of adding front/center fills to my system when working on larger outdoor stages - particularly when getting my system up in the air isn't an option due to the client's wishes.

Attached is a diagram of a baseline stage, 50-60ft across.  Typically for smallish spoken-word events I just put a single 15 on a stand on each inside corner of the stairs.  This has worked okay in the past, however now with the mask situation it's tough to get sufficient GBF while also getting enough output for the speakers to be heard 150'+ back - especially when the lectern ends up in a downstage corner.

Would adding front fills here help - mainly so that I could cover the first few rows of seating with that while moving the main LR speakers to the outsides of the stairs and getting them up higher to reach the back of the venue without blocking a slightline?  I know that typically best practice is to use the fewest number of speakers possible, but I've seen this technique done on other stages and am curious if it's something that could benefit me too.  Any input is much appreciated!

As an aside, for larger events where I can ground stack a proper system this isn't an issue - it's just for the little corporate jobs that don't want an "unsightly" array of tops lifted 10ft up on trussing!

[Brian Bolly]

The short answer is yes - provided that your front fills are timed and shaded for the intended listeners.

There's a good blog post by (who else) Bob McCarthy on the subject of Uncoupled Arrays.  Which, are basically what things like front fills and under balcony fills are. 

In addition, there's a handy Uncoupled Array Calculator based on Bob's math that can help you determine your spacing and fill quantities given a few known variables like what your speaker coverage is and what your unity distance is (explained in Bob's post).

[Russell Ault]

{...} As an aside, for larger events where I can ground stack a proper system this isn't an issue - it's just for the little corporate jobs that don't want an "unsightly" array of tops lifted 10ft up on trussing!

If my math is right, according to the traditional rules, for even coverage (i.e. +/- 3 dB) 150' away from a single-box-per-side PA I'd want the mains at least 35' up, no just 10' (at which point the sight-line problems have probably disappeared as well).

As for front fills, they're basically never a bad idea. Almost every PA design is going to leave some kind of a coverage gap near the front the audience area. They can also help with imaging, too.

Brian mentioned Bob McCarthy in his post; if you'd like to really learn about PAs, McCarthy's "Sound Systems: Design and Optimization" is the book.

-Russ

[Jeff Lelko]

I appreciate the input Brian and Russ.  I've given Mr. McCarthy's blog a quick read but definitely need to go digest it a bit more and play with the calculator he published.  The question I would ask though is if front fills would help improve GBF...  Naturally the lower the speaker plays the more omnidirectional the LF becomes.  I can fight that a bit with a high pass but would really want to ensure that there would be a tangible improvement here to offset the cost and complexity of adding this.

Supposing that the answer to that question is positive, what exactly should I look for in a good front fill speaker?  Obviously low profile is a must.  The Fulcrum Acoustic subcardioid FL283T element has intrigued me since its release a few years ago, but is that more trouble than it's worth compared to something more straightforward such as the RCF HDL6-A?

If my math is right, according to the traditional rules, for even coverage (i.e. +/- 3 dB) 150' away from a single-box-per-side PA I'd want the mains at least 35' up, no just 10' (at which point the sight-line problems have probably disappeared as well).

I don't disagree.  I should rephrase to say "audible-ish" 150ft back.  These are all outdoor amphitheater-style venues so the money seats are all much closer to the stage.  The clients just prefer when the sound can be heard by those wandering by further back.  I should add that my 10ft of trussing is also on the stage, so add another 40".  Even the big A-list acts that play these venues don't take their arrays much over 20ft, but I agree with the higher the better!

[Helge A Bentsen]

Frontfill size greatly depends on the capacities of the main system and it's intended coverage.
As an example, I've used the small Meyer boxes (name escapes me), EAW JF-NT, and JBL VTX V-25 as front fill for different layout and sizes of setups...

The best thing you can do (size and coverage requirements permitting is to buy something that can double up for other tasks.
A extra pair of monitors, a pair of 12"+/horn that can work as a system on their own or similar items that fits into your inventory.

[Brian Bolly]

The question I would ask though is if front fills would help improve GBF...  Naturally the lower the speaker plays the more omnidirectional the LF becomes.  I can fight that a bit with a high pass but would really want to ensure that there would be a tangible improvement here to offset the cost and complexity of adding this.

Yes.  You have two things working to your advantage - 1. You are moving your main speakers farther away from the podium (level + time offset to podium mic); and 2. Your front fills, although much lower in level, are working to provide clarity.  Since you're talking just speech, you can easily get away with a HPF on your FF @ 200 Hz or above.  And since two identical signals that arrive at a point in space, in time, will sum in level - even if that front fill is -6dB from your main speaker at the listening location, they will still sum.

Supposing that the answer to that question is positive, what exactly should I look for in a good front fill speaker?  Obviously low profile is a must.  The Fulcrum Acoustic subcardioid FL283T element has intrigued me since its release a few years ago, but is that more trouble than it's worth compared to something more straightforward such as the RCF HDL6-A?

I agree with Helge that any fills would be beneficial if they can double up for other tasks in your inventory.  But even if it's simply a smaller speaker (something as small as a pair of Meyer UPM-1P for example) would work just fine, especially since your main system is just a 15+HF box.  But whatever your main system is, you would be well served with speakers from the same family/voicing to make your life that much easier.  (Think: System vs Boxes)

[Russell Ault]

{...} The question I would ask though is if front fills would help improve GBF...  Naturally the lower the speaker plays the more omnidirectional the LF becomes.  I can fight that a bit with a high pass but would really want to ensure that there would be a tangible improvement here to offset the cost and complexity of adding this. {...}

Like Brian mentioned, anything that will allow you to put more distance between your microphones and your PA will increase your gain-before-feedback, with the amount of the difference (at least in the LF) being roughly calculable using the inverse-sqare law: if the neatest speaker to the lectern mic was only 3' away and you increase that distance to 6' (i.e. double) the sound from the PA arriving at the microphone will decrease by ~6 dB, resulting in roughly that much additional GBF; conversely, if your lectern is already 30' away from the nearest speaker and you increase that to 33', you'll only see a ~1 dB increase in GBF. In the HF, where speakers are actually directional, you might see additional GBF gains beyond the simple inverse-square if the increased distance also places the microphones further outside of the speaker's coverage area.

Ultimately your best bet would be to do some quick mock-ups in software to see if you'll achieve your desired outcomes. As I said above, almost all PAs benefit from some kind of front fill, but GBF isn't usually the goal.

-Russ

[Scott Helmke]

  Since you're talking just speech, you can easily get away with a HPF on your FF @ 200 Hz or above.

I wouldn't even hesitate cutting below 500Hz (or even higher) for a typical front fill, except for maybe a really loud outdoor show.

[Russell Ault]

I wouldn't even hesitate cutting below 500Hz (or even higher) for a typical front fill, except for maybe a really loud outdoor show.

If the main PA is an SoS (and therefore nearly omni-directional in the LF) everything below about 1 kHz may already be sufficiently loud (or more!) before the front fills are even plugged in. That's why it's always a good idea to take measurements.

-Russ

[Dave Garoutte]

I usually put the fills on an aux out with only vocals and acoustic instruments. 
The drums and anything with and amp/speaker on stage will be loud enough in the front rows already.

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