I am trying to make a few passive crossovers. I used the calculator and the coil and cap values are not coming out to even numbers, for example the coil is coming out to 8.5734mh. I know I am not going to find a 8.5734mh coil so do I just get as close to it as possible and call it a day?
Also the cap I need is 281.31ufd so says the calcualtor. Looking online I do not see any caps listed as ufd they are all just uf, is that the same thing? On top of that the closest I can get to the 281.31 is like a 250uf or a 300uf. What does one do in this instance?
First off, to create large capacitor values it's usually best to parallel multiple smaller caps to create the value you need. So to create 281 uF you might use 4 X 50uF plus one 30uF plus one 1uF in parallel (let me guess: 4-ohm high pass @ 75Hz? Passive is not the best solution for this.) Next, look at the tolerance on the caps you use. Most are +/- 5% or 10%. A few are +/- 1%. This is as close as you can get to the textbook values, so as long as you are within the tolerance of your components you are good. Third, be sure you NEVER use electrolytic caps in series with any speaker as they tend to sound really harsh. Use good poly caps at least. As far as inductors (coils) round up to the nearest tenth and then shoot for components within +/- 10% as this is the accuracy of even the best inductors. Make sure you use large enough wire gauge to handle the full system power for any inductor in series with a speaker and look for the lowest DCR (resistance) value you can find. Always solder and insulate all connections. Don't forget to match the sensitivity of your speakers and use resisters or L-pads to bring your tweeters down to match the mid/woof.
Now - and perhaps more importantly - are you relying on on-line calculators to design your crossover or are you modeling it in some sort of software? If you are relying on calculators only, do not expect the best results (unless you get really lucky.) You will get much better results using a software tool like Passive Crossover Designer or Speaker Workshop. I recommend you have a box full of various caps, resisters and coils to tweak your design after initial assembly to get things balanced perfectly.
Good luck and have fun.
-------------
Support the12volt.com