Crap bought a bunch of worthless crossover parts [message #44983] |
Fri, 16 July 2004 21:19 ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
James W. Johnson
Messages: 199 Registered: May 2009
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Master |
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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
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The resistors that you do have... [message #44985 is a reply to message #44984] |
Fri, 16 July 2004 21:49 ![Go to previous message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
wunhuanglo
Messages: 912 Registered: May 2009
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Illuminati (2nd Degree) |
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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.
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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 message Go to previous message](/forum/theme/AudioRoundTable/images/up.png) ![Go to next message Go to next message](/forum/theme/AudioRoundTable/images/down.png) |
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Wayne Parham
Messages: 18756 Registered: January 2001
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Illuminati (33rd Degree) |
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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.
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