What is a crossover?

[free_d20]

just wondering. i read about it all the time but have no idea what it is.

[drstawl]

That's when John Tesh records a Metallica Cover.

[drstawl]

No- seriously- it's a network of (usually passive) components (caps) in a multi-driver speaker that divides where various frequency components of a signal are sent.

Some drivers are designed to reproduce low frequency signals so the crossover splits off those frequencies from the whole signal and sends them to the low frequency driver. Same with the mids and highs in a 2 or three-way system.

[free_d20]

ohhhh, thanks man. very enlightening.

[Jblount]

crossover= sends lows to speaker cabinet capable of handeling lows, and sends the highs to the high range speakers.

[barefoot]

Expanding a little on what Ed wrote:

In any well designed speaker system the crossover will be optimized to account for the particular response, phase, and impedance characteristics of the individual speaker drivers. The biggest practical difference between active and passive crossovers is this. Passive crossovers look directly into the driver loads and, therefore, are very dependent on the frequency dependent impedance characteristics of the drivers. Active crossovers are buffered from the drivers by the power amplifiers and, therefore, only care about the speakers' response and phase characteristics.

Editorial:

"Generic" active crossover units with adjustable x-over frequencies, slopes, levels, etc. are only useful for sound reinforcement systems.... where nobody really cares much about accuracy or sound quality anyway. Why? Because, in order get a good crossover alignment with the simple filter type these units provide, the high and low frequency speakers sections must have a flat response overlap of about 2 to 3 octaves. This refers to sharp 4-order filter slopes. Shallower slopes require even wider overlap.

Systems almost never have components with this sort of frequency overlap. So the sound engineer must resort to delay (phase) manipulation in order to level out the response. This, however, only works for a very particular listening axis and creates horrible nodes and antinodes (lobes) at other listening angles.

The "optimized" crossover alignments in well designed speaker systems almost never fall into the simple types (Butterworth, Bessel, L-R, etc....) found in these generic active crossover units. Even the fancy new digital "multiprocessor" units don't yet have the flexibility to create truly optimized crossover alignments.

Thomas

http://barefootsound.com