Crossover
quote: I'm familiar with the term 'crossover,' but not really with its meaning.
Audio crossovers are a class of electronic filters designed specifically for use in audio applications, especially hi-fi. A commonly used dynamic loudspeaker driver is incapable of covering the entire audio spectrum all by itself. Thus, crossovers serve the purpose of splitting the audio signal into separate frequency bands which can be handled by individual loudspeaker drivers optimized for those bands. A combination of multiple drivers each catering to a different frequency band constitutes most hi-fi speaker systems. An audio crossover may also be constructed mechanically and is commonly found in full-range speakers. -- more at Wikipedia
If you play Guitar then you should be able to relate to the frequencies I will mention to describe the crossover idea. You can use the picture of the Keyboard to help if that works better for you. (Lowest notes are at the top). (click the keyboard to see that image in its original context).
Your bottom E string has a fundamental frequency of about 82 Hz. (Cyles per second). That is just a reference for this discussion.
When there is nothing attached to Amp 3 output (where we normally connect the blue B1 cable) the Powerstand does this:
- Frequencies above 110 Hz are sent to the L1 Cylindrical Radiator™ This is less of a "crossover" and more of a cutoff just because there's no point sending frequencies to the L1 that it can't reproduce.
- It doesn't mean that if the L1 cutoff is set to 110 Hz, you won't hear anything from the low E string. Our perception of tones is based not only on the fundamental (in the case of the low E at 82 Hz it is lower than 110 Hz), but it is also based on the harmonics we will hear in multiples of the fundamentals (2 x 82, 3 x 82, 4 x 82).
BUT
Add the B1 (with all four conductors working) and the PS1 does this:
- Frequencies above 180 Hz are sent to the L1 (the crossover is moved up).
- Frequencies from 40-180 Hz are sent to the B1 (and some processing (EQ) is applied to the 40-180 Hz range) to optimize things with the design of the B1.
For reference, 40 Hz gets us into the range of the low E string on an Electric Bass (an octive below our low E on an Acoustic Guitar).
Here's a bit more from Hilmar-at-Bose about the really low notes: