Cross at 4khz - Yea or Nay?

[BlueWizard]

This is something of a general question. No need to get too specific.

In reading this and other forums, I've gotten the sense that 4khz is an undesirable place to cross between Mid and High.

Could someone explain why? ... or why not, the the converse is true.

I have a vague idea for a speaker design, and I'm contemplating a Low to Mid cross of either 500hz or 800hz. These seem to be the preferred crossovers in old school design.

Generally three octave in the Midrange (more or less). 800hz is easy enough, though a bit of a compromise on the 3 octave rule. 800 ->1600 ->3200 -> 6400. I've never actually seen any speaker cross as high as 6400.

Most commonly 800hs Low/Mid cross in the range of 4500hz to 5500hz for Mid/High.

For a 500hz Low/Mid cross, if we go up 3 octaves - 500 ->1000 ->2000 ->4000. Which seems to be a problem.

So, did I imagine the problem with crossing at 4000hz or is there something to this? And IF there is something to this, what is the magnitude? Is this something of a disaster or more of a ...meh... whatever?

Sorry to bother you with such a trivial think, but an answer would help rest easy.

Steve/bluewizard

 

[skodaboy]

http://www.diyaudio.com/forums/multi-way/258487-why-crossover-1-4khz-range.html

 

[andy19191]

This is something of a general question. No need to get too specific.

If you are crossing a 2" midrange to a 3/4" tweeter than 4kHz looks like a reasonable choice. Similarly, if you are crossing to a ribbon tweeter with a 2" or larger midrange then it may also be a reasonable choice.

If you have a 5" mid or larger crossing to a typical 1" tweeter then 4kHz is likely to be too high because of midrange beaming, too close midrange breakup, too large a centre-to-centre spacing plus no doubt a few more reasons I have missed.

 

[system7]

Lynn Olson discusses the compromises here:

When working with rigid-cone drivers, there are some hard choices to make: if you lower the crossover frequency to minimize driver coloration, tweeter IM distortion skyrockets, resulting in raspy, distorted high frequencies at mid-to-high listening levels; if you raise the crossover frequency to improve the sound of the tweeter, the rigid-driver breakup creeps in, resulting in a forward, aggressive sound at moderate listening levels, and complete breakup at high levels. (Unlike paper cones, Kevlar, metal, and carbon fibers do not go into gradual breakup.) With the drivers we have today, the best all-around compromise is a 2nd, 3rd, or 4th-order (12-24dB/Oct.) crossover with an additional notch filter tuned to remove the most significant HF resonance of the midbass driver.

The Art of Speaker Design, Part II

I find 3-4kHz crossover with steep 18-24dB slopes just fine in a lot of cases. So does Troels Gravesen. If you go lower, you lose power handling and get increased distortion on the tweeter.

Low crossover point around 2kHz is usually dictated by needing to notch unpleasant cone breakup resonances on lively metal or reed bassmid drivers, so why go there at all? Notches sound bad IMO, good rolloff works better.