Hi I am new to building speakers and I could do with help to understand which crossover I should use. In my passive 15 inch subs. I also have top cabs to build as well they will be 10 inch and a horn sealed. All the help will be appreciated thanks. Benjamin1
Buy the "Loudspeaker Design Cookbook", a web search will find it, read it, and enjoy building your speakers.
Passive xovers should be your goal but you can avoid a lot of time with the hit n' miss issues of speaker design by picking up a decent active xover with such things as multiple slopes, adjustable cutoff points and maybe even delay. I haven't built a speaker in years so there may be some simple software available but you can find quite a few (digital) xovers from Rane, Ashly and even Behringer that will speed up the process and wont break the bank. Once you fine tune and determine the parameters needed to integrate the drivers and speaker, you can order the right parts and build a proper xover.
There is no substitute for experimentation when it comes to building a passive crossover. You never know how it will sound until you try. Years ago I took a piece of plywood and drove a bunch of long screws through it, sticking out the other side a good inch. The screws were 3" apart and ran vertically and horizontally, four columns wide and tall, so that there were twenty screws in a checkerboard pattern. I crimped alligator clips onto the ends of the screws that went through the plywood. I then bought from my favorite crossover supply company, Madisound, a bunch of really cheap capacitors, coils and resistors of various values. Those three components make up the guts of a passive crossover. Using values determined by a speaker crossover calculator, I would connect these components in various ways and try them out. I'd hook this breadboard test crossover up to my speakers and listen to it. Many attempts survived less than 15 minutes. Others lasted a day or two before they were further refined. As to which design I used, a first, second or third order crossover, we could get into that here but you can also read up about all that and more at numerous places on the Internet. I also assume that information is in the book recommended upthread. Once I discovered a crossover that sounded right, I went back to Madisound and bought expensive crossover components using the values determined by my experimentation. I'd then solder up the crossover on a piece of Masonite or in a gadget box. The final version always sounded better than my test one, I'm sure because of the better quality components used in the end result. While I used this in designing crossovers for car stereos, the technique would work for you, too. I would strongly recommend playing around with your crossovers before you settle on one for your speakers. It will save you money in the long run, you'll learn a lot, and you'll end up with a better crossover. Plus, as an audiophile, I found this fun.
online crossover design calculator http://www.the12volt.com/caraudio/crosscalc.asp#ccc online sub box design / volume calculator http://www.diyaudioandvideo.com/Calculator/Box/ great quality caps (i used and loved the clean sound of the premium sonicaps) http://meniscusaudio.com/capacitors-c-101.html