Home » Sponsored » Pi Speakers » Crap bought a bunch of worthless crossover parts
Crap bought a bunch of worthless crossover parts [message #44983] Fri, 16 July 2004 21:19 Go to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master
I thought I needed 10 8 ohm 1o watt resistors to make an 8ohm 100watt part...I used the same thinking for all of them. :( these Eagle resistors were a buck each...what a waste.


What in the heck do I really need here, I am having trouble with the math here.

thanks

Re: Crap bought a bunch of worthless crossover parts [message #44984 is a reply to message #44983] Fri, 16 July 2004 21:28 Go to previous messageGo to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master
Basically I need a 25 ohm 40 watt part, a 16ohm 40 watt part and an 8ohm 100 watt part.

I have 8 25 ohm resistors , 8 16 ohm resistors and 22 8 ohm resistors....maybe I can at least use some of these?


The resistors that you do have... [message #44985 is a reply to message #44984] Fri, 16 July 2004 21:49 Go to previous messageGo to next message
wunhuanglo is currently offline  wunhuanglo
Messages: 912
Registered: May 2009
Illuminati (2nd Degree)
the 25's, the 16's and the 8's - what are their dissipation ratings?

If the 8 ohm resistors are 20W, then two 8's in series will give you 16 ohms at 40W.

If you need 25 ohms, use three 8 ohm resistors in series for a total dissipation of 60W at 24 (close enough to 25) ohms. Power resistors are like what, + or - 10% ? So three 8 ohm resistors will give you something like 21.6 to 26.4 ohms, depending on how the tolerances stack up?

What's going to get kind of silly is making an 8 ohm, 100 watt part. You're going to have to series/parallel so may individual pieces it just won't be practical.

Re: The resistors that you do have... [message #44986 is a reply to message #44985] Fri, 16 July 2004 22:24 Go to previous messageGo to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master
They are Eagle Metal Oxide Film Non-Inductive Resistors
5%, 10Watt, 8.5mm x 32mm, 33mm leads


Re: Crap bought a bunch of worthless crossover parts [message #44987 is a reply to message #44983] Sat, 17 July 2004 02:46 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

You can use (8) 8 ohm resistors to form a high-power 8 ohm block. Connect two in series and four banks of those in parallel. Use the remaining two 8 ohm resistors for something else.

For the 12dB cable assembies, you need a 25 ohm resistor and a 16 ohm resistor. The 10dB assembly needs two 16 ohm resistors. Use all non-inductive 10 watt parts, and build them up in blocks of four. So each really uses a "resistor block" made using four 10 watt resistors.

For the 25 ohm resistor used in the 12dB assembly, we use two pairs of series connected resistors, one a 20 ohm and the other a 30. The series connection gives 50 ohms and two of those in parallel makes 25 ohms.

The 16 ohm block is easier, since it uses four of the same part, a 16 ohm resistor. Two in series, and the 32 ohms that is formed is then connected in parallel to another just like it to make 16 ohms.

There are photos of the cable assemblies here.

Obviously, I stand corrected... [message #44988 is a reply to message #44985] Sat, 17 July 2004 04:22 Go to previous messageGo to next message
wunhuanglo is currently offline  wunhuanglo
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Registered: May 2009
Illuminati (2nd Degree)
I never thought of building a "block" the way Wayne did (silly me).

Sorry for any confusion I lent to the discussion.

Re: Crap bought a bunch of worthless crossover parts [message #44989 is a reply to message #44987] Sat, 17 July 2004 08:03 Go to previous messageGo to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master
I am sorry Wayne but I am still unable to come up with an 8 ohm block using 8 ohm resistors, are you sure 16 are not required for this?

thanks

Can someone check my final crossover for correctness please? [message #44990 is a reply to message #44983] Sat, 17 July 2004 21:15 Go to previous messageGo to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master

I still have to put in a wire to connect the parts where you see the orange line. Please let me know if I have made any mistakes.

thanks

Also.. [message #44991 is a reply to message #44990] Sat, 17 July 2004 22:07 Go to previous messageGo to next message
James W. Johnson is currently offline  James W. Johnson
Messages: 199
Registered: May 2009
Master

Here is how I wired the resistors..


Re: Also.. [message #44992 is a reply to message #44991] Sun, 18 July 2004 00:27 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18783
Registered: January 2001
Illuminati (33rd Degree)

It all looks A-OK to me.


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