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Hi Guys.


You know when you are listening to a song in a car that has a SUB in the back. Well when you listen to metal songs for a example, when there is a big drop into a beatdown the SUB kicks in to add emphasis as the song goes into a heavier/beefy part.


Is this done on the software or does the SUB itself pick up when to do this?

If it needs to be done in Logic in this case, how do i do it? How do i set the song to boom through the SUB at a specific part?


Thanks guys.

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on the car amp there will be a special sub out, which has a "cross over" in the signal path.


The crossover is simply a filter, and for the "sub out" it will be of the low-pass variety, for example it could be 12db/oct at 120hz, or it could be much lower like 90Hz or 60Hz or even lower (or indeed higher) and have a different slope (higher db/oct is more expensive). Some amps have adjustable cross overs. Cross overs can be high pass or band pass too (its just an EQ circuit, so it can be like any EQ in theory).


As you have probably gathered, the purpose of the cross over is to reduce the audio bandwidth, and keep the audio signal within a specific frequency range. This means that different parts of the system get different components of the sound for which they may be more specialised. If this was not done, valuable headroom may get swallowed up by frequency components that a particular part of the system handles badly. ie if you have the high freqs going in to the sub it will not be able to move fast enough to reproduce them, but that part of the signal is still taking up part of the signal being sent to the sub.


So, the only sound going to the sub is the low low bass, so if the track doesn't have low low bass then the sub will not fire. If your not hearing the sub on certain tracks, it cause the track does not contain the range of frequencies that the sub responds to - they are all obove the cross over frequency.


That or the driver only turns the sub on for the tunes he likes ;-)

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