crazy-in-az,
The info that sreten offers is more than good. I have edited his post, below, to strip it down to what I believe are the keys:
....Using c/o calculators is a sure recipe for not getting it right, its simply not that simple.3 ways are far harder to get right than 2 ways, more mistakes....
....Prebuilt crossovers are a very poor choice....
....Your flying blind with no driver specs, measurements or measuring equipment.....
...Lots of building effort with no idea how it will turn out is not good ....
The links he provides are very good as well. I am not familiar with all of them, but the ones I are recognize are the real deal.
The fact that pre-made crossovers exist and
are offered for sale leads to the incorrect assumption that putting together a good speaker is as easy as choosing either 4 or 8 ohm drivers to wire up to it. Additionally, people follow this approach all the time and often they post glowing reviews of their results, further solidifying the myth.
But if you want to design and build a DIY speaker that compares to commercial offerings the process is complex.
The first complication is that driver impedances are never exactly 4 or 8 ohms. Impedances also vary with frequency. For a given crossover slope, i.e. 6/12/24 db per octave, crossover caps and coils must be chosen to match the
actual impedance of the drivers involved, not the nominal impedence (i.e, 4 or 8 ohm).
When incorrect matches are made, inevitable with pre-made crossovers, the result is either spikes or dips in the frequency response. How bad these anomalies are depends on luck basically. My first DIY speaker was a 3-way using a pre-made crossover. I thought I had carefully chosen the crossover frequencies, power ratings, etc.
But at the time I was not aware of how to measure actual speaker driver impedance. I discovered a major frequency response problem few years later when I got a professional RTA and took a look at my speakers. BTW, the speakers had never sounded right, in fact not good at all, but I was flying blind as to how to correct the problem. What I discovered with the RTA was a spike of approximately 10 db at around 1k. And 1k was not even one of the crossover points.
Another complication of
good speaker design is level matching between drivers. You can not simply rely on the published spl specs. And 3-ways are much trickier than 2-ways in this regard.
I love DIY'ing and am not trying to dissuade you. But achieving a positive result will require an investment of time and effort much greater than the simple process that is often inferred by reading crossover and driver specs offered by those who sell these items.
I realize that many enthusiastic first time speaker builders would forge ahead in spite of warnings. I have done similarly myself a few times. Sometimes learning from mistakes leaves a greater impression. But I wish I had the information available to me back then that sreten has kindly offered you.
