Alembic F-1X phase shift

Discussion in 'Amps and Cabs [BG]' started by JRBrown, Dec 19, 2003.

  1. JRBrown


    Jun 21, 2000
    North Carolina
    There is a phase shift in the Alembic F-1X preamp which could lead to a reduction in bass response if you're not aware. This phase shift is inherent in ALL crossover networks. Some companies invert the polarity of the crossover output internally so the the shift is invisible to the user. Want to know more? See this link I started on the Alembic site:
  2. nonsqtr

    nonsqtr The emperor has no clothes!

    Aug 29, 2003
    Burbank CA USA
    I think the relevant statement is "this only applies if you're using the crossover output at the same time as the full range output".

    I'm not really sure how true that is though. I think the effect may be present naturally if you're just running a "regular" bi-amp system.

    I also think there's more to it than just the crossover, the speakers themselves can introduce phase shift. (That's why there are "time-aligned" speakers, but most people tend to think in terms of high frequencies when they hear that term).

    What you're really saying is that the filters in the Alembic crossover are introducing a natural phase shift into the crossed-over signals. This is true, it's true of "all" audio filters, and it can be quite significant, depending on the type of filter being used. Most manufacturers use the 24 db/octave Linkwitz-Riley filters for crossovers, they're supposed to have comparatively little phase shift outside of the slope region, but I haven't worked the math so I don't really know for sure.

    It's interesting that Alembic would make such a glaring omission in their documentation though. They're usually pretty anal about stuff like that. In a good kind of way. :)
  3. JRBrown


    Jun 21, 2000
    North Carolina
    I agree. But to keep things simple, I cut my discussion of filters short.

    Without doing the math: If you're running a regular biamped system, the high pass signal may not be in phase with low pass signal. The amount of phase shift is frequency dependent. Therefore, phase shift between the high and low pass signal is insignificant because frequencies above and below the crossover point are different.

    Ron is looking at updating the documentaion.