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Speaker Internals.

Zoomup

In bookshelf and larger speaker enclosures that include a crossover circuit, I have noticed that the main large driver is wired correctly to the crossover terminals + to + and - to -. BUT, the tweeter or horn has been wired in reverse + to - and - to +. Why is this so? I do not consider this to be a mistake.

Z.

  • 0

    The the phasing is normally positive = blow, and it may be the intention to compensate for time delay/ phase shift in the cross-over or that the reflex port rather than the main face of the base drive is being phased with.

  • 0 in reply to mapj1

    Oh yes. I had not realised that, I came across this video covering just that situation. Towards the end it is covered.

    https://www.youtube.com/watch?v=NlOH-GnLu0k

    Z.

  • 0 in reply to Zoomup

    Now after watering the garden I have had additional thoughts about speaker phasing. An orchestra or even a pop group produces multiple sounds and frequencies at the same time. So, the many frequencies can never be in phase simultaneously. A 300 Hz bass note can not be continually in phase with say a 5kHz high frequency signal. So I am now confused.

    Z.

  • 0 in reply to Zoomup

    This is how I understand it.  The instrument with a fundamental frequency of 300 Hz will have harmonics.  For the instrument to sound correct from the loudspeaker the harmonics must be preserved in amplitude and phase FOR THAT INSTRUMENT.

    If you are listening to several instruments, the phase relationship between the various instruments will be different depending on where you are sitting and the acoustics of the room.  But the individual instruments will still sound “right” so long as the phase and amplitude of the harmonics of that instrument have not changed.   So what is important in a loudspeaker is that the phase of the harmonics for each instrument is preserved, but the phase between the individual instruments does not matter.

  • 0

    only identical, or harmonically related frequencies can be described as having a fixed phase relationship.

    Unrelated frequencies have a phase difference that changes continually over time, generally only returning to the same state after the time that is the lowest common multiple of the two cycle periods - so if say 400Hz and 500Hz are in phase at some instant 't' then they will not be again until 4 whole cycles of the 500Hz have passed, the  same as 5 whole cycles of the 400Hz. So the cyclostationary period is the difference frequency, in this case a 100Hz beat note.) As frequencies get really close, they approach a zero beat - in radio this is a common method to verify that the frequency is 'spot on', as zooming in to zero beat can be done by ear.

    this video shows it rather well on an oscilloscope (after about 1min introduction )

    Mike.

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