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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Sun 17, 2019 5:30 pm 
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jmsent wrote:
fifties wrote:
Mike Toon wrote:
Would 300 Ohm flat twin-lead work?
That's a good idea; wire is wire. Nothing special here.
... the wire is only 22 ga. Not suitable for speaker wire. It'll work for very short runs, but I wouldn't run e.g. a set of AR3's with it.
Thanks, I'd missed that point! I agree, 22 gauge is not suitable for speaker wire. My rule is minimum 16 gauge.
Cheers,
Roger

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Sun 17, 2019 6:57 pm 
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Run a few in parallel to increase the effective gage. In fact, why don't you remove a 6" wide strip of carpet between your amp and your speaker, and pave it with twin lead. ;-)

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Sun 17, 2019 10:31 pm 
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jmsent wrote:
fifties wrote:
Mike Toon wrote:
Would 300 Ohm flat twin-lead work?

That's a good idea; wire is wire. Nothing spechul here.


Well, except that twin lead is designed for RF and the wire is only 22 ga. Not suitable for speaker wire. It'll work for very short runs, but I wouldn't run e.g. a set of AR3's with it.

I was responding to his specific question;
SparkyDan wrote:
I've been looking at "flat" speaker wire to run under about 5' of carpet.

And would believe that the 22 gauge could handle that short of a run. Additionally, two lengths of twin lead could be employed, tied in parallel, which would presumably double their current carrying capacity.

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Sun 17, 2019 11:09 pm 
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From Wikepedia:
"The characteristic impedance of twin-lead is a function of the wire diameter and its spacing; in 300 ohm twin-lead, the most common type, the wire is usually 20 or 22 gauge, about 7.5 mm (0.30 inches) apart. This is well matched with the natural impedance of a folded dipole antenna, which is normally around 275 ohms."

Assuming worst case, i.e. 22 gauge:
22 gauge is 642 circular mils, copper giving 19 ohms per 1000 ft.
16 gauge is 2,580 circ. mils, copper giving 4.73 ohms per 1000 ft.
Thus you need FOUR 22 gauge wires to equal ONE 16 gauge wire (my working target size for most speaker wire in the home.) That's a lot of 300 ohm twin under the carpet.
If you run only TWO 22 gauge 300 ohm flat-twin wires, that would be about 19 gauge equivalent. a bit small unless a very short run, e.g. less than 10 feet.
Of course, for 20 gauge twin it's a bit better, but TWO is still not equivalent to 16 gauge. It's about the same as 17 gauge, but likely OK.

Also, at least one cable supply company sells this (from website):
"Flat Under Carpet Cable Insulated copper tape to lay under carpets, thickness less than .04 inches, means it is indiscernible, yet available in sizes equivalent to 10 or 12 AWG building wire."
Cheers,
Roger

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Sun 17, 2019 11:28 pm 
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engineer wrote:
If you run only TWO 22 gauge 300 ohm flat-twin wires, that would be about 19 gauge equivalent. a bit small unless a very short run, e.g. less than 10 feet.

So apparently it's agreed that this would work for his 5 foot run.

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Tue 19, 2019 11:21 pm 
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fifties wrote:
engineer wrote:
If you run only TWO 22 gauge 300 ohm flat-twin wires, that would be about 19 gauge equivalent. a bit small unless a very short run, e.g. less than 10 feet.
So apparently it's agreed that this would work for his 5 foot run.
I think so...
5 feet of twin speaker wire is 10 ft of series wire to the VC. So, for our "300 ohm flat twin" wire to the speaker:
10 feet of 22 gauge wire is 0.165 ohms
10 feet of 20 gauge wire is 0.104 ohm.
Note: for 10 feet of 16 gauge wire, my default gauge for room speakers (not more distant PA), it's 0.0409 ohms.
If the average 8 ohm speaker has a DCR of 6 ohms, the example 5 foot of either gauge as "flat twin" speaker wire is not an issue.
But at what length does it become an issue? (reduced speaker damping and significant power loss.) I'd not run it more than 10 feet (20 ft of wire), and then only for small "undemanding" systems.
Cheers,
Roger

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Tue 19, 2019 11:28 pm 
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I was going to suggest about 7ft as a maximum run with this thin of a wire gage.

To be safe, I recommend some welding cable, or a flattened 3/4" coopper pipe (AKA a buss bar). :-D. If you go with welding cable, it should be about 1/2" diameter for each lead.

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Wed 20, 2019 6:28 am 
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I once did a service call on an audio system in a building close to an airport
where the customer heard a strange sound every few moments.

I was decided that a sweep radar of some type was causing it.

300 ohm TV lead makes a fine transmission line.

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Wed 20, 2019 8:35 am 
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Get some 24k gold foil and adhere it directly to the floor. Make it as wide as you like (and can afford).

For the win! :mrgreen:
-Ed

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Wed 20, 2019 10:44 pm 
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Barry H Bennett wrote:
I was going to suggest about 7ft as a maximum run with this thin of a wire gage.
I'll buy that! 7 is better than 10!
Barry H Bennett wrote:
To be safe, I recommend some welding cable, or a flattened 3/4" coopper pipe (AKA a buss bar). :-D. If you go with welding cable, it should be about 1/2" diameter for each lead.
You forgot about car battery boost cables!
Cheers,
Roger

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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Fri 22, 2019 1:09 am 
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jmsent wrote:
fifties wrote:
Mike Toon wrote:
Would 300 Ohm flat twin-lead work?

That's a good idea; wire is wire. Nothing spechul here.


Well, except that twin lead is designed for RF and the wire is only 22 ga. Not suitable for speaker wire. It'll work for very short runs, but I wouldn't run e.g. a set of AR3's with it.


A 15 ft (30ft total) run of 22 gauge wire has .5 ohms of resistance. I don't expect that
to be noticeable to most golden ear listeners.
Mikek


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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Fri 22, 2019 3:29 pm 
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qmavam wrote:

A 15 ft (30ft total) run of 22 gauge wire has .5 ohms of resistance. I don't expect that
to be noticeable to most golden ear listeners.
Mikek

Here's a graph of an amplifier with a series output impedance of .7 Ohms feeding a simulated 2 way loudspeaker load (the kind you'd find on many audio systems). The red line shows the response into an 8 Ohm resistor, and the black line shows the response into the simulated load. This is the same scenario as having an amplifier with 0 Ohms output impedance but .7 ohms in series with the speaker. That much variation over a broad frequency range would certainly be audible on pink noise, and quite possibly on music as well. Beyond the power loss, the speaker's varying load impedance at different frequencies causes the change in response you see. On something like a pair of AR3's you'd see even more variation. If you consider a 4 ohm load, a .5 Ohm series resistance would reduce the damping of an amplifier with a damping factor of 1000 at the output terminals to a damping factor of 8 at the speaker terminals.
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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Fri 22, 2019 6:11 pm 
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Could you could run regular wire between to the tackless strip and the pad? I ran some "low voltage" 14 ga wire yesterday. It was thinner than a tackless strip.


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 Post subject: Re: Flat speaker wire?
PostPosted: Nov Fri 22, 2019 7:26 pm 
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jmsent wrote:
qmavam wrote:
A 15 ft (30ft total) run of 22 gauge wire has .5 ohms of resistance. I don't expect that to be noticeable to most golden ear listeners. Mikek

Here's a graph of an amplifier with a series output impedance of .7 Ohms feeding a simulated 2 way loudspeaker load... the black line shows the response into the simulated load. This is the same scenario as having an amplifier with 0 Ohms output impedance but .7 ohms in series with the speaker. That much variation over a broad frequency range would certainly be audible on pink noise, and quite possibly on music as well. Beyond the power loss, the speaker's varying load impedance at different frequencies causes the change in response you see. On something like a pair of AR3's you'd see even more variation. If you consider a 4 ohm load, a .5 Ohm series resistance would reduce the damping of an amplifier with a damping factor of 1000 at the output terminals to a damping factor of 8 at the speaker terminals.
Good graphs... thanks. The black line is about +/- 0.5 dB in the audio band. I don't think that is audible on any signal. However, I favour larger than 22 gauge to keep good damping and virtually no power loss. My short run default size for 8 ohm speakers is 16 gauge, but my other room (some 40 feet away) large speakers (Ditton 440's) are fed by 12 gauge wire (0.13 ohms in series with VC and amplifier))... it's bulky, but well hidden!
Cheers,
Roger

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