To time align your Main to your Front-fill using Smaart, first find the acoustic crossover point where they have matching level, then match their arrival times using the delay finder.
Setting the delay for the front-fill speakers is a very easy process using Smaart. The challenge is in choosing the correct measurement microphone location. If your mic location is too far into the audience, your front-fills will be too loud, tearing off the faces of the season ticket holders in the front row. If the mic location is too close to the stage, timing errors and comb filtering will worsen.
Here’s an overview of the process:
- Set relative solo level and EQ for Main and Front-fill at on-axis positions.
- Find the acoustic crossover point.
- Set delay.
Crossover (acoustic): The frequency and/or location where two separate sound sources combine together at equal level.
ONAX: A mic position used for calibration located at or near the horizontal and vertical center of a given speaker or array.Sound Systems: Design and Optimization by Bob McCarthy
A system can only be optimized as well as it is designed. For this example, we are going to assume that the system has been perfectly designed so that it has minimum level, spectral, and ripple variance from vertical top to vertical bottom of the audience area covered by the Main. In laymen’s terms: it sounds the same everywhere we expected it to.
Now, all we need to do is fill in the gap left in the front of the stage with our Front-fills.
Let’s get a little more detailed.
Set relative solo level and EQ for Main and Front-fill at on-axis positions.
Another way to say this would be ONAXL (on-axis with left) = ONAXF (on-axis with front-fill). And it goes like this:
- Measure the Left Main solo @ONAXL. Set EQ. Capture trace.
- Measure a single Front-fill solo @ONAXF. Set EQ and level to match ONAXL.
Before we combine the Left Main and the Front-fill, we need to match their solo on-axis response and level. Otherwise, it will be difficult to create a seamless transition at the acoustic crossover point.
Here are the solo measurements of my Main and Front-fills. Pink is the Left Main array and green is the Front-fill.
Find the acoustic crossover point.
Now that the sub systems are playing nicely alone, let’s schedule a play date. Where L solo = FF solo we will find XLF (crossover between left and right).
- Start at the geometric mid-point between L and FF or wherever your ears find matching level.
- With both arrays playing at the same time, move the mic while watching the Live IR until the peaks match.
The way I used to do this was very slow. I would guess the position of XLF, measure each system solo, resetting the delay each time, look at the magnitude graph, then move the mic, over and over again until I found matching level.
A turning point for me was discovering the option in the Transfer Function Options page called proportional panes. This makes the Live IR graph bigger, which really helps for tracking it on an iPad screen.
Measuring two sources at once can be tricky. If you don’t see two distinct peaks, they may be out of bounds of the graph, already on top of each other, too low in level, or something else. If I zoom out, zoom in, and still don’t see them, I’ll go back to solo measurements to track them down.
Now that you have found XLF, the process of setting the delay for the front-fill is simple.
- Measure Main solo. Use the Delay Locator to set the compensation delay in Smaart.
- Solo the Front-fill.
- Click Find in the delay locator. Observe the delta delay value. This is the difference in the current delay and the measured delay. Put this number into the delay line for your Front-fill.
- Click Find again to verify the change. Delta delay should be very close to 0.
- Measure L+F @XLF to verify summation.
You could also just mouse over the second peak in the Live IR window to see the time offset, but you have to get your mouse in the exact right spot. I find using the Delay Locator a bit easier.
Don’t worry if you don’t get a full 6dB of summation at every frequency. Focus on the areas where both traces have high coherence. If you suspect a misalignment, take solo measurements again, observe their phase relationships and adjust.
Have you tried this method for aligning Mains to Front-fills in Smaart? What were your results? Do you use a different method? Let me know in the comments below.
If you’re curious, here’s my microphone map and system tuning checklist for the example above.