Noobster 5.0 (by a noob)

[TopherGreen81]

First I want to thank everyone for all the info on this site you guys/gals are an amazing superabundance of knowledge.
So, I finally have a house now and no longer have to worry about the other ppl in the apartment building. I am about to start my first Home Theater DIY project and I want to keep the cost below $500 for LCR RR and LR. So I decided on the Noobster concept. I say concept cause I will be building the Cabs still .5 cubic ft but not using the PE Cabs to keep cost below 500. I am not new to audio just home audio I have build many car sub cabs and some home audio sub cabs. So heres my problem I am a complete noob to XO's, I want to learn how they work but for now I will use what is known to work and I have 2 questions on the (augerpro)MTM XO. Brandon says to use a 1.5mH for L2 and unwound 3.5 times I don't understand that. Also R3 and R7 are not needed right? Thanks for the help.

Here is the link to the XO.

http://htguide.com/forum/showpost.php4?p=413818&postcount=80

[james5]

Just unwrap 3.5 coils of wire from the inductors loose end and cut it off with wire cutters. This end that you just cut will now be the new "connection" or "solder" point for the inductor.

I'm new at this too...but if I understand correctly you are reducing the resistance of the inductor by reducing the overall length of the wire to the optimal level that Brandon has figured for the crossover.

[TopherGreen81]

That makes sense. OK now I noticed that PE does not have a 28.9uF Cap can I string together a 20uF, 5.6uF and a 3.3uF to make that 28.9uF Cap.

[ThomasW]

If you read the specs for any crossover component you'll find they're built to a tolerance +/- 5%, +/- 10%, whatever.

This means there's little no need to fixate on nailing 0.9uf given the tolerances of the components...

[Curt C]

That makes sense. OK now I noticed that PE does not have a 28.9uF Cap can I string together a 20uF, 5.6uF and a 3.3uF to make that 28.9uF Cap.

I'll let Brandon make the final call on this, but IMO, save some cash and just buy a 30 uF. this will be within 4% of 28.9 uF, and the caps generally have a 5% tolerance anyway.

C

[augerpro]

I usually pick the closest value for the caps that can be made with two or less caps in parallel. So for the MTM, C8 is 25+3.9uf, C5 is 10+1.5uf, C9 is 33+5.6uf. All of these values are available in both the Jantzen Crosscap and Dayton Metalized poly.

In a design this simple though, Curt is right, small changes will have little effect. You could use C8=30uf, C5=12uf, and C9=39 or 40 depending on whether you went with the Jantzen or Dayton cap. Hmm, I may just modify the XO schematic to reflect these values since this is a high value design and buying 3 instead of 6 caps would be helpful.

And about the inductor, yes unwind 3.5 turns from one of the ends. and yes, R3 and R7 just represent the inductor resistance.

[Dean100]

If you unwind the inductor and cut it off, don't forget to scrape off the coating on the end of the wire so that you can get a good solder connection.

[augerpro]

Updated the MTM crossover schematic to reflect the cheaper cap values.