A recent post got me thinking about Crossovers, specifically first order crossovers, or 6db/octave crossovers.

Let's put 6db per octave in perspective, but before that, let's put 6 db in perspective.

3db is a slight but noticable change in volume. If you tweak your volume control up or down just enough to clearly perceive a change in loudness, that is about 3db. So 6db is two small tweaks upward or downward of your volume control.

Now let's look at 6db per octave - 1st order crossovers and for this example, let us assume a crossover of 2,000hz. One octave down at 1,000hz is like tweaking your volume control down 2 slight nudges. Dropping another octave to 500hz is like 4 downward nudges. Let's generously say that is about like turning your volume control down from 40% of a turn (4 on a scale of 10) to about 20% volume (2 on a scale of 10).

We are down two octaves and while the sound has diminished, it is still certainly playing and is certainly audible.

Now let's drop one more octave to 250hz (3 octaves or 18db total) which I say for purposes of illustration is about like turning your volume down to ONE (from 4 down to 1). That is pretty quiet, but you can still hear it.

Now let's go the other way; let's move an octave upward from 2khz to 4khz then another octave to 8khz, about like going from 4 on the Vol Cntrl down to 2. Now a third octave up to 16khz, and while the loudness is very low, it can still be heard; it is still at a functional level.

It would seem that if you intend to use a 1st order crossover, you pretty much need two full range speakers; a woofer that goes up very high and a tweeter that goes down very low.

So, briefly let's consider 12db/octave crossovers and ask the general question,

**how many DB does a speaker have to drop to be consider acoustically out of the circuit?**How far down before any sound coming from it become irrelevant?

If you are pushing a speaker beyond its rated frequency response, is it just dropping off on its own, or is there real potential for distortion outside its rated frequency range?

With 12db crossovers, you drop pretty fast; 24db in two octaves and 36db in three. While the phase relationships cause by the crossovers might be better with 6db crossovers, how does one reconcile the extreme frequency range that is forced on the speakers?

Just curious.

Steve/bluewizard