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PostPosted: August 25th, 2021, 11:00 am 
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Don Diego wrote:
Tom,

Thanks. I was going to try some 10 gauge speaker wire from Amazon like:

https://www.amazon.com/InstallGear-Gaug ... 825&sr=8-5

Since I am operating in the dark, I assumed I would have to test several long lengths (30-40 ft.) of different speaker wire before installing the best and affordable one in the walls, so any recommendations are welcome.

My current speaker cables are 12 ft. MIT Music Hose from the 1980's.

You might be better off sticking to the Music Hose. Your Music hose sports polyethylene dialectic whereas the Belden cable Tom is using sports PVC dialectic -- not even my third choice for sound reproduction. For me -- I found that any "speaker cable" has its issues much less using the Class II cable that's used in building construction. I found an exciting product that serves the music in ways I never expected. Andrew Heliax plenum-rated micro-wave cable. It is a pain-in-ass to terminate, but WOW is the time and effort worth it!! I ran it under the floor of my living room (aka. music room) and installed SO-259 female UHF connectors to the floor with 8-inch pig-tails through the floor to hook up to my amps in a conventional manner.

The cable itself is terminated with PL-259 male UHF connectors and suspended from the floor joists with cable ties to "float" the runs from the wood flooring. One important issue is to make the cables the exact same length to better support stereo imaging.


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Speaker-amplifier-interconnects.pdf [1.97 MiB]
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Andrew_Heliax_Plenum_Rated_CATVP.pdf [32.22 KiB]
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PostPosted: August 25th, 2021, 11:56 am 
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SoundMods wrote:
I found an exciting product that serves the music in ways I never expected. Andrew Heliax plenum-rated micro-wave cable. It is a pain-in-ass to terminate, but WOW is the time and effort worth it!! I ran it under the floor of my living room (aka. music room) and installed SO-259 female UHF connectors to the floor with 8-inch pig-tails through the floor to hook up to my amps in a conventional manner.

The cable itself is terminated with PL-259 male UHF connectors and suspended from the floor joists with cable ties to "float" the runs from the wood flooring. One important issue is to make the cables the exact same length to better support stereo imaging.[/color]


That's a RF cable. RF signals are so small they get easily effected by EMI and other RF interferences. So, they need exceptional shielding. The outer copper tube is the shield.

Can we say, shielding of cables is extremely important in audio use ?

Attachment:
heliax.jpg
heliax.jpg [ 10.25 KiB | Viewed 5070 times ]


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PostPosted: August 25th, 2021, 12:15 pm 
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Cogito wrote:
That's a RF cable. RF signals are so small they get easily effected by EMI and other RF interferences. So, they need exceptional shielding. The outer copper tube is the shield.

Can we say, shielding of cables is extremely important in audio use ?

Attachment:
heliax.jpg

Let's consider this thought -- if most DIY audio folks have portable phones, PCs generating RFI from the CPU clock, Wi-Fi, LED light fixtures that have DC power supplies generating RFI/EMI, lighting dimmers, modern TVs with CPU clocks, and even Blue Tooth -- then it seems that shielding can be important. Most amplifiers whether solid-state or vacuum-tube (valve if you will) take feedback off the signal feed output leg of the amplifier. Does the amplifier know the difference between the audio signal or RFI/EMI riding on the cable and finding its way into the inner-sanctum of the amplifier? NOPE!

Now twisted pairs do provide a certain amount of common-mode cancellation, but RFI/EMI still hops on the "bandwagon" and can find its way in. Plus there are speaker cables like those on offer at Amazon that is simply glorified zip-cord with parallel conductors. Anything that can be done to strip away any unwanted anomalies can serve our ultimate goal of great sound reproduction in the home.

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PostPosted: August 25th, 2021, 12:38 pm 
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SoundMods wrote:
Anything that can be done to strip away any unwanted anomalies can serve our ultimate goal of great sound reproduction in the home.


Exactly.

In the "old" days, power cords for CRT monitors used to come with Ferrite Beads.

I wonder if anyone tried Ferrite Beads on speaker cables.


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PostPosted: August 25th, 2021, 12:59 pm 
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Cogito wrote:
SoundMods wrote:
Anything that can be done to strip away any unwanted anomalies can serve our ultimate goal of great sound reproduction in the home.


Exactly.

In the "old" days, power cords for CRT monitors used to come with Ferrite Beads.

I wonder if anyone tried Ferrite Beads on speaker cables.

I added those years ago to my speaker hot feeds closest to the power amps. I forget who it was in the U.K. that was selling 3-uH inductors to put between the speakers and the amplifiers for just that purpose, but that's where I got the idea about RFI/EMI blocking (or at least reduction) on the speaker cables.

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PostPosted: August 25th, 2021, 1:11 pm 
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If you were truly fanatical you could put six fifty Ohm coaxial cables in parallel to make a 8.33 Ohm transmission line to match your speaker impedance. For a 16 Ohm speaker only three fifty Ohm cables in parallel would be needed.


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PostPosted: August 25th, 2021, 1:23 pm 
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brombo wrote:
If you were truly fanatical you could put six fifty Ohm coaxial cables in parallel to make a 8.33 Ohm transmission line to match your speaker impedance. For a 16 Ohm speaker only three fifty Ohm cables in parallel would be needed.


Not much to be gained matching impedance at audio frequencies where the cable length is <<< less than a wavelength.... Wavelength of heliax at 30kHz is 8km, proportionally longer as you go down in frequency....

Roscoe

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PostPosted: August 25th, 2021, 1:49 pm 
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brombo wrote:
If you were truly fanatical you could put six fifty Ohm coaxial cables in parallel to make a 8.33 Ohm transmission line to match your speaker impedance. For a 16 Ohm speaker only three fifty Ohm cables in parallel would be needed.

If you can find some -- there actually is speaker cable with the characteristic impedance of 8-ohms. The Polk Cobra Cable. Just be advised that it may need a special termination to prevent amplifier instability. Just ask the man that uses Polk Cobra cable to good effect -- David Berning.


Attachments:
cobracable-close-up.jpg
cobracable-close-up.jpg [ 13.08 KiB | Viewed 5063 times ]

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PostPosted: August 25th, 2021, 2:40 pm 
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Roscoe Primrose wrote:
brombo wrote:
If you were truly fanatical you could put six fifty Ohm coaxial cables in parallel to make a 8.33 Ohm transmission line to match your speaker impedance. For a 16 Ohm speaker only three fifty Ohm cables in parallel would be needed.


Not much to be gained matching impedance at audio frequencies where the cable length is <<< less than a wavelength.... Wavelength of heliax at 30kHz is 8km, proportionally longer as you go down in frequency....

Roscoe


Amen to that. Also, impedance matching assumes that you have the same impedance at the sending end as receiving end. Total mismatch with power amps and speakers. Also the speaker impedance is all over the place when using passive crossovers.


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PostPosted: August 25th, 2021, 3:21 pm 
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I heard the difference when Walt went to this microwave cable, it was significant


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