Keith, I love you. you are awesome.Thanks for giving back and helping our next generation. I'm just and old FOH A1 in Vegas and have been sending my techs to your videos to help them out. Keep it up, you're making a difference. Peace to you.
Keith, can’t knock you for making a decent video. However, you failed to show your students the full picture when it comes to possible differences between your polarity inversion vs. time alignment. For one, it was by chance (or perhaps by design for the sake of your video) that polarity inverting your subs aligned the phase traces. That’s going to be a shot in the dark for many deployments. A student should see what happens in the crossover region after you’ve applied the two different actions outlined in your video. With the polarity inverted on the subs, what does the measurement look like with the main array added back in? Do you have proper summation above and below the crossover frequency you were focused on? With both systems energized, do you have significant cancellation in the crossover region if you flip polarity back on the subs? How does this compare to the delay method? If the subs remain in relative phase and you time align them to the tops, do you have more or less summation in the crossover region? If you flip polarity on one of the systems in this case, do you have more or less cancellation. You may be misleading your students by not showing them this additional context for measuring and tuning crossover points. You might be “in phase” at that one crossover frequency by overall out of time. You may be giving away “free” energy of the systems aren’t properly time aligned through the crossover region. You should see distinct summation through the crossover region with both systems time aligned and and in proper polarity. If this summation produces undesirable frequency response, apply corrective EQ. This way your system design is benefiting from the “free” summation energy. You may have been there with what you demonstrated with the sub polarity flip, but I feel you need to demonstrate how to validate it with additional measurement.
Nice job Kent. Some food for thought... not that I have a conclusive answer or the point is mostly academic... but in this scenario we're looking through the perspective of a continuous signal. What about a transient? Polarity or delay the better choice? Also, important for everyone to understand the alignment is only as good as the design allows the alignment to be consistent over as much audience area as possible. A whole other topic....
First step to use smaart is to synchronize the reference jumper on it. I didn't see you do that. So I think you screw up Dude! This Is why your lines look so awkard.
@@snapascrew The only thing I heard him said was as long as Smart has a reference of time he doesn’t bother time delaying it. Well I as far as I’m aware of you need to time delay so it knows the distance between the speakers and measurement microphone. I just never seen it done this way. Why reinvent the wheel if is already round?
My question is "aligned from WHERE??!" Measuring from one spot/seat in the room will make for a varried results from other locations of measurement, depending on relation from seating locations vs subwoofS locations, and sub to sub respectively and in assocation??? Seams one sub will be close and one far from any given seating, so how do you balance and for Phase on that?! Seams challenging if impossible to balance for all seating locations in this particular instance. Besides my marbles, what am I missing here???
Its at 0. You need to have a 0 point to define all other mathematical things youre doing. Doesnt matter where zero is. It's like 'at X i measure this' . Ofcourse in this field of work there are sweatspots. Spots where phase cancels out in some frequencies. Standing waves with the room etc etc. But 0 = your absolute 0 point of measurement and aligment. Heck it can be 20cm in front of the subs. it can be 500meters in the distance . Doesnt matter where you put that after that the equations start.
Good video. But more people might have a deeper understanding if he defined his terms. Plot the trace, phase wrap, delay locate. These are all Smaart terms that are simple in concept but students may not know.
Problem with polarity inversion vs. time delay in this case: what does polarity inversion do to frequencies above and below the crossover? It may be perfectly aligned at the exact crossover frequency, but is it combing out energy anywhere else outside of the crossover frequency? I think Merlijn van Veen has probably the best solution for a situation like this. Do separate measurements with both time delay and polarity inversion and not only check the phase at the crossover, but check about 1/3 octave above and below the crossover as well. (If your x-over is 100hz, 1/3 octave below and above would be roughly 80hz and 125hz, respectively). If polarity inversion causes weird buildup or cancellation of frequencies, then it's not the ideal solution (likewise with time delay).
The method you describe is pretty solid with delay. The phase inversion doesn't have to be exclusive of delay, either. I tend to not invert, because (in outdoor scenarios), I will often try to employ Endfire-type techniques for sonic containment. This requires at least 4 points of sound, though a 4.3 system (tops in each corner, summed sub array in front, rear corners are full range) has worked best so far. Essentially, you measure from the center of the space, first aligning the front tops with the front sub array, then aligning each rear top with its respective subs. Once you have that done, you move to the rear line and you delay the rear stacks until you are 90° out of phase from the front stack. Step back maybe a foot further away from the front stack. If you have adjusted things correctly, you will get a summing of the signals inside your sound space and almost total cancellation outside of if. You may have to fiddle a bit with your times, and the more bands of delay you have, the more profoundly you can create this effect. When I say fiddle, I mean tenths of a millisecond for mids and highs, so lightweight processing isn't going to do the job. It does work, I've done it, however, it's not easy, it's very time consuming, and I would only suggest even thinking about trying this if you own the system, or have a very supportive owner and team who are willing to give you the time to try and fail until you get the hang of this. If you can get it right, you absolutely blow minds because if you are outside of the field, you will question whether the system is even on, and then as soon as you cross the threshold, the sound hits you like a wall.
Thanks for your videos.. i was a student/graduated in 2006.. been working in live sound, post production & system installations ever since. Thanks to everyone at CRAS for your work! God bless
Have you compared this method to using the "delay locator" method? If I wanted to align the tops to the subs or vice versa - I would want my crosshairs (cursor) to be exactly on the crossover point on the magnitude trace AND I would want the phase traces to align at that position as well. That is why you have the straight line going into to the upper screen with the crosshairs up there as well. They (Rational) made it easy for us to lock it in this way. It seems you are choosing a different point to align the boxes that is not at the down-point on the crossover where they cross. Can you explain further? In my mind when it comes to delay vs. polarity - I usually go with whichever option uses less delay.
I wouldn't invert the polarity at all. In my experience, I got amplitude reduction significantly. Also to me it's much more easier by overplotting the impulse response of each individual driver.
Why would you 180 invert? What about if you have a kick drum being played on PA, on initial transient array speakers will move out while subs will move in. Not ideal, in my opinion...
Well man., prstty damned amazing. He set up a sub real quick with out employing any music! To me, that’s a bit like a blind man calibrating my new OLED!
Keith, I know this videos been up for a bit. Just wanted to ask how you were sure you weren't working off reflections when measuring the sub? Where was the mic here?
Great video, just a bit confused, is the oscillator still on 5.20seconds, just low that we couldn't hear it? (otherwise surely it's just matching the output time which I know you aren't doing) or is thee a way to monitor the differences without noise?
Thank you Keith.. Delaying or Polarity inverse would essentially be the same in this case, 8ms delay would be half cycle of 62.5hz which you spotted the alignment is needed. correct me if I am wrong , thanks in advance...
Keith, you're a badass. Thanks for teaching me the skills to be successful. I'm still trying to nail good mixes fast but it'll come with time, I'm sure
Fernando Ventura theres a video on youtube to crack smaart v6, in portuguese but its pretty easy to follow just looking at the screen. Ive done it, takes 10 minutes
Open Sound Meter. It's basically Smaart Light but also has some cool features like being able to move captured traces forward and backward in time. It's also free for Mac/PC and around $50 for iPad OS.
Keith, very good video! Thank you very much! My question is if the subs are really far from the main.. let say the the main is 10ft behind the subs, then do we have to find the delay time between sub and main first and then phase match them?? And how do we find that delay?
Nice video Keith, thanks for sharing. I like the idea of introducing delay to emphasize the phase traces. Do you have a preferred bunch of settings for the FFT: window shape, window length, averaging? Can you think of any pitfalls that would result in an unreliable phase measurement?
