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Sub alignment questions with Smaart

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Jose Peralta:
I have purchase and been using Smaart for a year now as a learning curve. Due to my schedule, going to a training may not be possible so on my own I have been learning how to use the software and the idea and concept behind it. Now comes my questions, when aligning subs, do I delay locate the tops first at any given position and use that for the subs or do I need to find IR of the subs since the wavelength of bass frequency are longer which make it hard to locate?  My other question is, if I were to use use indoor measurements, can I ground plane the measurements to reduce comb filtering?

Tim Verhoeven:

--- Quote from: Jose Peralta on April 20, 2023, 06:43:34 PM ---I have purchase and been using Smaart for a year now as a learning curve. Due to my schedule, going to a training may not be possible so on my own I have been learning how to use the software and the idea and concept behind it. Now comes my questions, when aligning subs, do I delay locate the tops first at any given position and use that for the subs or do I need to find IR of the subs since the wavelength of bass frequency are longer which make it hard to locate?  My other question is, if I were to use use indoor measurements, can I ground plane the measurements to reduce comb filtering?

--- End quote ---

You can check out Michael Curtis his YouTube channel for some of the basics, also Rational Acoustics has a whole bunch of interesting video's online.

To answer your specific questions:

Main/Sub alignment: yes, you put your mic where you want to align the mains and subs, send audio through the mains, delay locate to the mains and take a measurement. Without changing the location of the mic and without touching the delay settings, you switch the audio to the subs. Then the goals is to make the phase trace of the subs overlap with the one of the mains around the acoustic crossover region (the frequency range where the magnitude of the mains and subs is close to equal), you do this by changing the delay on the sub output.

Measuring on the ground plane: yes, it is a good idea to put the mic on the floor for this process to avoid any floor bounces that cause comb filtering. It doesn't really matter if this is indoor or outdoor.

Art Welter:

--- Quote from: Jose Peralta on April 20, 2023, 06:43:34 PM ---Now comes my questions, when aligning subs, do I delay locate the tops first at any given position and use that for the subs or do I need to find IR of the subs since the wavelength of bass frequency are longer which make it hard to locate?  My other question is, if I were to use use indoor measurements, can I ground plane the measurements to reduce comb filtering?

--- End quote ---
This article and it's links should answer your questions and give you a solid foundation for sub alignment:
https://www.merlijnvanveen.nl/en/study-hall/166-subwoofer-alignment-the-foolproof-relative-absolute-method

Generally, the output of the subwoofer lags in time behind the top cabinet, if delay is required the top cabinet, not the sub requires delay.

Caleb Dueck:
Minor note - don't forget polarity.  If the phase traces cross sharply but not overlay, try polarity.  This is especially true with some tapped horn and other non-front-loaded/non-ported subs. 

Jose Peralta:
Thank for the responses! I appreciate all the help. Art, good detail information on the link. Another thing I want to be aware is have the subs ahead of the tops for X reasons. I dont know if this true but the physics of the subs in relation to the tops, just the nature happens to have some sort of delay. Let just say I have to put the top about 3 feet behind the subs, does that mean I have to delay the subs plus the delay of the sub driver producing actual sound in time with the bass driver at the crossover frequency? I know their is a mathematical equation to this.

Caleb, I have gone through this situation especially when using various crossover slopes. I have a dbx driverack PA+ which does not have a polarity inversion but only delay.

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