During my interview with Adam Hill we discussed an AES paper he coauthored called Subwoofer positioning, orientation and calibration for large-scale sound reinforcement. During the interview, we focused mainly on the interference of stages and other boundaries on directional subwoofer arrays, but there is another large part of the paper where the authors describe a ground-based optimized subwoofer array that I thought would be fun to try to recreate.
Wondering how a gradient subwoofer array works? Check out this video explanation.
1 – Minimize spacing to avoid nodes
As a starting point, four single cardioid subwoofers were placed across the front of the stage on the ground with four meter spacing.
This initial setup gives very limited coverage across the audience area, although there are no noticeable nodes anywhere in the coverage area.
2 – Expand horizontally and vertically
Since the additional subwoofers of the system will be off to the sides of the stage, they can each be stacks of three subwoofers.
3 – Angle outside subs 45º
The optimization routine shows that simply rotating the outside subwoofer stacks away from the stage by 45° gives very even results across the audience area while keeping SPL on the stage under control
Note that I have not taken into account the potential gain difference between my 2-element gradient arrays across the front and the author’s “four single cardioid subwoofers”.
Results
15dB of F2B (front-to-back) rejection at 43Hz comparing the 1st row to DSC (down stage center). 6.75db of rejection at 90Hz.
Can this be improved?
The authors leave the design wide open for adjustment and make this recommendation about placement:
an even coverage in the audience area is best achieved when subwoofer spacing is minimized
If we add one more sub it will decrease the spacing and DSC should benefit from improved F2B rejection. Let’s also add a 2nd order Linkwitz-Riley LPF at 203Hz.
1.75dB of improved rejection at 90Hz. Otherwise, similar results.
How would you improve this design?
What are your ideas for improvement? Comment below.
You can download my MAPP file here.
I found that horizontal coverage can be expand by creating arc within the subwoofer array. Whether physical arc (moving the sub) or electronic arc (using delay). I found this with just messing around using Easefocus. Cheers!
Thanks John! Are you thinking that this design could benefit from wider coverage? Would you like to take stab a redesign?
Hi, I don’t believe that the solution presented above is a good one.
Instead I would recommend building a Cardio Delay Arc as presented in this documented that I have created for this occasion:
https://docs.google.com/document/d/19W8pt7D6qZ11Aj7cch0FF9ZEctc4s-6t0LLSxRcJ5Zg/edit?usp=sharing
Less speakers, better coverage, higher SPL, works allright even when pushed to the limit.
If anyone is interested in more detailed explanation please contact me on email which can be found at: http://www.vojtechpanenka.com
Nice work Voytech. You killed it!
And I was able to download your design and saw the same results.
I see that Voytech has each cardiod stack spaced 1.56m apart. Any idea what the delay settings are? I would be looking at three or four stacks on top of a two story flat roof house (30ft x 70ft). Amps would be Crown XTI2 series with up to 50ms of delay
Hey Chuck. Sounds like an interesting project. Aside from manufacturer’s prediction software, I recommend merlijn’s Subwoofer Array Designer. It’s great!