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Old 30th March 2007, 06:00 AM   #31
Foxx510 is offline Foxx510  Australia
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Here is an interesting calculator that shows the effect of wire gauge/length on damping factor.

http://www.bcae1.com/dampfact.htm
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Old 3rd April 2007, 02:53 AM   #32
GM is offline GM  United States
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Location: Chamblee, Ga.
Quote:
Originally posted by Cloth Ears
Thanks GM.

How did you come by the figures - or is it a trade secret?
Greets!

You're welcome!

No trade secrets, I use to list the math, but folks primarily just wanted an answer, so quit posting it. Here's one response I saved from years ago, so the values aren't pertinent to your app:

When wire is used as a filter element, then this subject can get
complicated, otherwise you select wire based on voltage drop over distance.
Solid core has the lowest losses/ft and can't oxidize between the strands
like lampcord, so my preference is solid core, preferably silver plated.

WRT tiny wire in the cab, the wire to the LF/one side of the XO should be
the same size as what you ran from the amp, and its length should be
included in the gauge calc. The rest of the wiring can be sized based on the
distance from XO since its the actual run for the mids/HF.

FWIW, I use 10ga ROMEX less the sheath, etc., and twisted together at ~eight
wraps/ft. After the XO is 24ga magnet wire twisted together. Terminations
are the weak link in any wire run, so if you're up to it, converting the
typical pitiful terminals on the back of the amps and the speakers to screw
lugs so ring tongue connectors can be used is a cheap/effective tweak. I
also recommend using an anti-corrosive conductive paste, such as T&B or
Burndy's available at an electrical supply house to ensure the best
practical current carrying junction, and stay that way.

To calculate the required gauge:

Assuming you don't want the wire to act as a resistor to either flatten a
rising response or better match the impedance of a tube amp, then the size
is determined by how much voltage drop you consider acceptable.

Using the driver's Pe, Re (or total Pe, Re if multiple drivers are used),
then with the formula:

I = sqrt P(Pe) / R(Re)

you can calculate ~ max current draw capability. If this number is >the
amp's rating, then you may clip it on loud passages.

To determine wire size required:

Circular Mils (CM) = (2*L*I*10.8)/Vd

Where:

L = length of wire in ft
I = max current of circuit
Vd = voltage drop

Some rounded off CM values:

32ga = 64
30ga = 100
28ga = 159
26ga = 320
24ga = 404
22ga = 640
20ga = 1024
18ga = 1624
16ga = 2580
14ga = 4109
12ga = 6529
10ga = 10384
8ga = 16512

Example:

Pe or short term peak rating = 400W
Re = 3.4 ohms
wire run (one way) = 20 ft
VD = 1V (this is considered the max acceptable, I usually use 0.3-0.5V)

Sqrt 400/3.4 = 10.846A

(2 x 20 x 10.846 x 10.8)/1 = 4685.472CM, or 12ga.

As you can see, small wire/long distances can eat up amp headroom. Conversely, if the amp is near/on the speaker, acceptable wire size becomes tiny (or Vd vanishingly low if a large gauge is used).

At what point downsizing the wire becomes audible is of course dependent on the individual and his system/room.

HTH,

GM
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Old 3rd April 2007, 04:26 AM   #33
OzMikeH is offline OzMikeH  Australia
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I see very few people use Neutrik Speakon connectors. Why is this? they look like a good design to me. Especially if you parallel the contacts and use them only for 2 poles.
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Old 4th April 2007, 05:41 AM   #34
GM is offline GM  United States
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Greets!

If you mean for consumer or DIY, there's no need for the quick connect feature/high cost.

GM
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Old 7th April 2007, 02:47 AM   #35
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Altec Lansing had a chart based on length of the run to figure the gauge size of the wire needed. I'll see if I can locate a amplifier manual and post it.
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Old 7th April 2007, 04:49 AM   #36
OzMikeH is offline OzMikeH  Australia
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Genuine Neutrik Speakon plug = $13, chassis socket = $9 australian.

Not expensive. about $50 for two sets with freight.

I went this way because I didnt want to cut a 2.5 inch hole in my cabinets for a binding post style terminal plate. I only needed a 24mm hole.
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