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TimK Posted - 03/12/2017 : 11:12:43 AM
We've moved from a 1960s house where over a period of 15 years I installed some HA (mostly insteon & X-10) stuff. Our new house was built in 2006 and is modern by comparison. The builder put in a structured wiring cabinet and even ran coax and a few Cat5 cables.

Now here is the real kicker, somebody thought it was a good idea to run 18 cables, each 4-conductor, 18 ga unshielded (like thermostat wire) from the structured wiring cabinet through the attic to various places. Even though these cables terminate in the cabinet, I have no idea where the other ends are located. Is there any possible use for these wires in a HA sense, or should I just abandon them?

Tim in AZ
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Geo Posted - 03/20/2017 : 12:39:37 PM
Once again, agreed.
This reminds me that some years ago, because of the cost of copper, manufacturers began making their coax cable with iron wire with just a few mils copper plate on its surface. Our local cable TV has been using it for years because for their bean counters it's "dirt cheap". But it's not. Theoretically its OK, why use expensive copper when just a few mils carry the signal? In reality, because of the temperature changes the wire stretches and contracts, then there are mechanical forces due to the use and the thin copper layer does not like it. They had to replace parts of my wiring (I put good cooper coax in the walls when I built the house) over and over again. I don't know the numbers but I'm sure the coax is no longer dirt cheap for them.
oberkc Posted - 03/20/2017 : 11:52:13 AM
More thoughts....if you get really lucky regarding the end points of these wires, you could use them to connect magnetic sensors for doors and windows.

Some around here get really crazy with this stuff and have their HA system make announcements ("someone is at the door", "dryer is finished", "Intruder!", etc.). Hook these wires to speakers and use them for this type of purpose.

Connect these speakers to an echo-type device. Get your news and weather broadcast through the house.
oberkc Posted - 03/20/2017 : 09:37:50 AM
And, back to the original topic...Depending on where the wires go, they could be used, potentially, to power a wireless camera or motion sensor, I suppose. Cannot come up with a lot of uses in the HA arena.
oberkc Posted - 03/20/2017 : 09:31:53 AM
Despite the fact that I am not as smart as some others around here, I still think that this wire was intended as speaker wire.

I did stay at a Holiday Inn once. That must count for something.
Geo Posted - 03/20/2017 : 09:17:29 AM
As I said before, the only technical reason for using a stranded wire for audio is its flexibility. For an in-wall distribution solid AWG18 is fine.

Generally, all audio signal sources must be limited to about 16kHz to 20kHz. This is not just because only some kids can hear 18kHz but, more important, there is the unavoidable Nyiquist frequency limit for sampled, that is digital signals, be they FM stereo (the 38kHz subcarrier) or CDs.

Skin depth in a copper wire at 17kHz is 0.5mm. The diameter of the AWG18 wire is 1.02 mm, leaving merely 20 micrometers of the internal wire core unable to carry that top frequency. Such attenuation due to the increase of the wire resistance begins at that point. Increasing the wire size will not fix this.The skin depth remains constant. On the other hand, using a smaller wire, such as AWG24 with only 0.511 mm diameter means that the skin effect would begin about 65kHz, so the resistance of the wire remains constant but higher than that of the AWG18 and thus less suitable for feeding powerful speakers. BTW, much audio signal distribution such as telephone, intercom etc. use AWG20 to AWG24 wiring. These signals are generally limited to about 3kHz to 5kHz. Their wiring skin-depth attenuation kicks in at much higher frequencies than their equipment bandwidth allows, so the effect cannot be used for noise filtering. On the other hand, Ethernet cable carrying 100 megabits (comparable to 100MHz, the FM radio range) uses four twisted pairs of AWG24 wire. All that means the wiring is a complex issue much affected by impedance matching of the source and the load, well beyond the scope of this forum.

Literature states that at audio frequencies stranded and solid wires of the same AWG behave identically. This is claimed to be caused by all the strands being in electrical contact with each other - I did not test it. The difference is with Litz wires where all the individual strands are isolated.

At any rate, wiring itself is just a small part of audio signals distribution. Speakers represent an inductive load with varying impedance. It grows at high frequencies so that any potential increase in resistance due to the skin effect is balanced out. Damping of the speakers may become a problem and speakers, in general, are the major culprit when it comes to the sound quality, not the wiring. Personally, I run fairly short stranded leads to my speakers, but if you should connect yours to a remote location using in-wall solid wires I doubt you will hear any difference.

Finally, I wholeheartedly agree with oberkc. In one of my past lives I designed audio equipment as we called it Hi-Fi. The fundamental problem was that nobody ever defined what exactly Hi-Fi means. One can never reproduce the sound and the ambiance of a live performance. So it all comes down to personal preferences - and, unfortunately, a lot of marketing hype. We claimed to "hear" a difference between 0.1% and 0.01% THD. And now we have compressed MP3s and earbuds. And some of us have wives who don't like loud music.
stusviews Posted - 03/19/2017 : 6:14:21 PM
I'm an audiophile. Anyone and everyone who has listened to my system has remarked that they never heard sound so clear and realistic.

The gear is McIntosh (the audio company, not Apple, Mc not Mac). I probably spent more on one of my FM only tuners than a teenager spends on their first car.

In particular, I have a 200W/ch amp (MC2200), a pre-amp (C28), two FM tuners (MR80, MR500), a CD changer (MCD7008) and a control center (CR7). All the gear is vintage and used, I could not possibly afford new McIntosh components.

The speakers are four Acoustic Research AR58S's plus a Sunfire HRS subwoofer. All interconnecting RCA cables are Monster Cable. The speaker wire is Monster XP High Resolution 12AWG speaker wire.

There is no one item that makes a difference, it's the combination.

I can, but don't often, raise the volume to the threshold of pain with no discernible distortion
oberkc Posted - 03/19/2017 : 5:25:21 PM
I once (more than a couple of years ago) read a story of someone connecting some speakers using coat hangars. The general consensus at the time was that it sound as good as speaker wire. (No, I am not advocating using coat hangars for speaker cables.)

I still hear talk that expensive HDMI cables give better picture quality. (I don't believe this either.)

Some people swear by vinyl records over digital. (matter of taste, in my estimation. I guess people are nostalgic for pops and hisses.)

For most practical applications, I suspect most of us could not tell the difference between stranded and solid wire for speakers. We play music via compressed MP3 files on speakers that sound like $10 earbuds.

Count me in the camp that suspects that bundle of wires was intended for whole-house audio.
stusviews Posted - 03/19/2017 : 3:13:18 PM
The "skin effect" (higher frequencies travel on the surface of the wire) matters very much as a solid wire has only one surface, stranded has many.

I've never encountered anyone knowledgeable using solid wire for audio. Come to think of it, I've never encountered anyone at all using solid wire for audio except for an intercom where minimizing higher frequencies make speech clearer. Telephones also use solid wire for the same reason.

If you're interested in fidelity, then use only stranded wire for speakers.
Geo Posted - 03/19/2017 : 1:35:01 PM
The opinion that solid wire is unsatisfactory for audio is debatable. It depends on the length and the power you want to pump into the speakers. A stranded wire is flexible, but that is not needed for installation in walls. In terms of the skin effect, a stranded wire at audio frequencies behaves exactly as a solid wire, unless it is an expensive Litz. But the skin effect is no issue until you get into the radio frequencies. The major characteristic that counts is the resistance. A solid AWG18 wire resistance is only about 11% higher than the same gauge 19/30 stranded one, which may not be an issue for wire runs of a reasonable length.

This is from the electrical engineering standpoint. The issue becomes a can of worms when the audiophiles and "golden ears" enter the picture. One can purchase a few feet of wire costing a few cents to make for a hundred dollars from a specialty store with the guarantee of "great sound" - they even specify which end has to be connected to the amp and which to the speaker. It's all subjective and I'm not getting into that debate.
stusviews Posted - 03/12/2017 : 4:30:29 PM
If the wire is "like thermostat wire," then it's solid which is unsatisfactory for audio.
Tfitzpatri8 Posted - 03/12/2017 : 4:21:40 PM
Whole-house audio prewiring?
stusviews Posted - 03/12/2017 : 4:04:54 PM
Virtually useless for HA. Use a continuity checker to identify which is which and use the old cable as a drag for wherever you want a different cable over time.

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