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Old 15th December 2007, 09:39 PM   #1
wixy is offline wixy  Australia
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Default Cat 5 question

I'm currently using 4 twisted strands of Cat5e cable still in the jacket for my FE206E's, run direct for about 3.5 metres from the driver to the amplifier (a KingRex T20 'T-Amp'). The wire looks like this:

Click the image to open in full size.

I'm just wondering if this is too much wire for these drivers?

Should I be using less?
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Old 16th December 2007, 12:43 PM   #2
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That cable is breath-taking! I use 4 Cat5 WIRES rather than 4 Cat5 CABLES.

Most 206E implementations, including mine, wind up with a rising frequency response. The simplest solution, although not necessarily the best, is to add series resistance. Running large gauge cables with essentially zero resistance exacerbates the problem. Thin wires is generally the way to go. Some folks use as small as 30ga wires with good results.

Hey, if it works for you, use it. That's not the way I'd do it.

Bob
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Old 16th December 2007, 01:09 PM   #3
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Agreed. Thin / high resistance wire is a simple & elegant way of adding series resistance to a driver. Better than using a separate resistor IMO -the fewer connections the better. Connections are always trouble.

I'm one of the insane people Bob mentioned who've used 30ga in the past, although that really was extreme -FF165K in pipe-horns with Audiolab monoblocks. It actually worked rather well, so long as you went easy with the old volume knob. 20 - 24ga is usually a decent compromise for FR units with a sensitivity of ~92db or greater.

There is a price to thin wire that needs to be kept in mind though, and that is that you limit the dynamic bandwidth -there's only so much current the wire can handle. Within reason, that's less of an issue with FR drivers though, because unsupported, they can't handle the huge LF transient swings of some recordings (say, Pink Floyd's Live at Pompii) anyway.
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Old 16th December 2007, 07:53 PM   #4
wixy is offline wixy  Australia
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Thanks guys, looks like i'm going to be changing wires.

Are there any better options that using 4 cat5 wires?

Am I going to get into trouble running long lengths of thin wire?

If I do use long lengths of thin wire such as the 4 x Cat5 strands, do I need to add more shielding?
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Old 16th December 2007, 08:17 PM   #5
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Frankly, I'd be thinking more about the fact that a longer run of wire will have greater resistance than a short one, than shielding the stuff.
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Old 16th December 2007, 08:47 PM   #6
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FYI my 4-strand cable is star wound -- on end it looks like this:

..+..
-...-
..+..

(disregard the ".." -- ascii art is near impossible when the editor insists on eating leading spaces!)

The cable is twisted about once an inch. This gives the cable a modicum of RF cancellation. I don't live in an RF dirty area, so this is not really a problem.

If you think that 24ga is too small, you can get 18ga 4-wire cable at HD, etc. It's used for HVAC and irrigation control applications.

Bob
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Old 23rd December 2007, 10:24 AM   #7
OzMikeH is offline OzMikeH  Australia
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I just made a set of speakers cables using old telephone wire (for fixed installation behind the wall), it's 24 AWG solid just like cat5 but much easier to untwist.

I untwisted 4m of wire, one pair for each speaker. I stretched it out and sticky taped the ends to a linoleum floor an inch apart and ran over the top with packaging tape, then peeled it off the floor foot by foot and folded the edges of the tape over the wires. I stuck it down again with the sticky side up and repeated the taping process from the other side. The tape does make a mess of the polish on the floor but that's a minor issue compared to She Who Must Be Acknowledged's reaction to crinkly bits of old packaging tape draped across the living room floor.

My big ugly amp has a huge damping factor, I think I need still more resistance to bring the bass up. But these 20 minute cables make it much more enjoyable to listen to.

I didn't bother twisting it, I dont have any RF issues.
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Old 23rd December 2007, 10:49 AM   #8
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My experience with cat5E wire is that for Fostex drivers I prefer a single twisted pair of wires, although I haven't ever used as long a run as you need.

Cat5E initially sounds very thin, with no bass and brittle highs. After 50-100 hours playing it breaks in some and smooths out a bit.

John C.
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Old 23rd December 2007, 01:17 PM   #9
soongsc is offline soongsc  Taiwan
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The right combination of CAT 5 will appropiately damp low requency harmonics probably caused by back EMF. This gives the true performance of the speakers and not the blown up bass which generally is not coherent with the image of the initial onset of the initiating musical instrument..
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Old 23rd December 2007, 02:25 PM   #10
AndrewT is offline AndrewT  Scotland
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Hi,
adding resistance between the amplifier and the speaker will raise speaker Q.

A long single pair will have more resistance than a long dual or multiple pair.
The speaker Q will be higher with the single pair than with a multiple pair of the same length.
Some speakers suit a slight raising of Q to tune them to their environment.
Most speakers tend towards a prominent bass peak when additional resistance is put into the feed.
Try your speakers and find which suits you and your room.

One thing added resistance does not do is add damping. Additional resistance reduces damping.
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