Introduction to designing crossovers without measurement

Next time you build, try to get the treble closer to the mid driver.
You can even trim a bit off the treble faceplate to get it closer still. 10mm cut off would be good.

The higher the crossover frequency, the more important the "closeness" becomes.
 
Dear Companion Allen B:I would like to ask you (to clarify) and specially to you, there is a lot of encountered opinions about the measurement of Thiele-Small parameters but ( I have to be sensible.there is a lot of opinions stating that small level signals, are unproper, and not reliable, others present "papers" expresing concisely that the real idea of the work of this two remarcable persons (Thiele and Small) stands basically on small signals, would you please "clarify this for me, and others?, Thanks in advance Mr Allen B, and also thanks for your work about Designing crossovers without measurement, A masterpiece, for me an many others...
 
My understanding is that a speaker is well behaved at low levels. In cases where the voice coil is running hot, and also when the cone is running close to its excursion limit, the results may be compromised.

Since neither of these cases are 'normal' it makes sense to deal with those separately, and to take the measurements at a level within the limits. The results should be the same at different levels within these limits, but if you take them at extremely low levels you'll also have to contend with the noise limits of the test equipment.