Emotiva subwoofer cable - AVS Forum
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Old 11-17-2011, 06:55 AM - Thread Starter
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I'm currently looking at different subwoofer cables, namely bluejeans and monoprice. After reading another thread, I looked at Emotiva's website and saw they had two cables with RCA connectors. I emailed them to ask about the cables in relation to using them with a subwoofer and was told that either would work fine, but the digital coax cable would most likely be the better choice.

So, my question is: what exactly is the difference between their "RCA Cable" and their "Digital/Coaxial Cable" in relation to using them with a subwoofer?

The cables can be seen here: http://emotiva.com/interconnects.shtm

I'm new to subwoofers (don't have one yet...I'm in the "research" phase) and their cabling so any help is greatly appreciated.

Cheers!
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Old 11-17-2011, 07:10 AM
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The digital cable is a 75 ohm coaxial cable. For subwoofers, this is the one you want.
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Old 11-18-2011, 06:57 AM - Thread Starter
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Thanks for the response. I'll be sure when the time comes to get the 75ohm cable.

At this point I'm trying to better understand the reasoning behind using such a cable for a subwoofer. I'm not questioning the use of the cable, just hoping to understand why coax is used over other RCA-type cables, such as the other Emotiva cable I mentioned. I'm just curious and wanting to learn. Anyone?

Cheers.
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Old 11-18-2011, 07:12 AM
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Coaxial cable consists of a central conductor surrounded by shielding:

http://en.wikipedia.org/wiki/Coaxial_cable

This shielding prevents the low level signal from picking up interference from other electrical sources.

Regular RCA WIRING has NO shielding and is therefore inferior to the coaxial cable for use as a subwoofer cable.

Bill C
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Old 11-18-2011, 09:34 AM
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Quote:
Originally Posted by vertigo4 View Post

So, my question is: what exactly is the difference between their "RCA Cable" and their "Digital/Coaxial Cable" in relation to using them with a subwoofer?

Technically, there is no such thing as a subwoofer cable and either the RCA or the digital will work fine.

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Originally Posted by KidHorn View Post

The digital cable is a 75 ohm coaxial cable. For subwoofers, this is the one you want.

Why? Analog audio connections are not 75ohms so that spec is irrelevant.

Quote:
Originally Posted by vertigo4 View Post

At this point I'm trying to better understand the reasoning behind using such a cable for a subwoofer. I'm not questioning the use of the cable, just hoping to understand why coax is used over other RCA-type cables, such as the other Emotiva cable I mentioned. I'm just curious and wanting to learn.

There is no difference. A digital cable with RCA connectors is an RCA cable. The problem is that it is not a symmetrical issue. Standard analog RCA cables are generally not suited for digital use because they need not adhere to any impedance spec.

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Originally Posted by BillCinLR View Post

Coaxial cable consists of a central conductor surrounded by shielding: This shielding prevents the low level signal from picking up interference from other electrical sources.

True but, to a degree, twisted pairs do this, too. Note that both suggested cables have "100% double shielding using a solid mylar wrap overlaid with tin-plated, oxygen-free copper braiding."

Quote:


Regular RCA WIRING has NO shielding and is therefore inferior to the coaxial cable for use as a subwoofer cable.

Untrue. Regular "RCA WIRING" is usually coaxial in construction unless you buy the very cheapest junk you can find. Every audio cable I have terminated or re-terminated over the past 50 years has been coaxial.

So, the bottom line is that either of these cables will be fine for the subwoofer and the only difference is the single core conductor of the digital necessary to have the 75ohm spec.

Kal Rubinson

"Music in the Round"
Senior Contributing Editor, Stereophile
http://www.stereophile.com/category/music-round

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Old 11-18-2011, 09:35 AM
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Almost every home electrical system runs at either 55 or 60 Hz. Long cables have a tendency to pick up extraneous signals in these frequencies. The signals tend to be faint, but they exist. For short connections, like say between a CD player and an amp, this likely won't be an issue. But longer connections, like between a speaker and a receiver it can be.

Regular speakers don't play 55 or 60 hz very well and they don't amplify the signal so the faint 55 or 60 Hz signal doesn't effect the overall sound much. Subwoofers, on the other hand, amplify the signal and they play 60 Hz really well.

Coaxial cable is shielded and hence the 60 Hz signal doesn't make it to the central conductor. RCA cable isn't and the signal does make it to the conductor(s).

In most cases, you can get away with a regualr RCA cable or even regular speaker wire, but in some cases, you'll get a constant 60 hz hum unless you use a coax cable.
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Old 11-18-2011, 09:50 AM
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You're being way too nit picky about the responses.

Quote:


Why? Analog audio connections are not 75ohms so that spec is irrelevant.

Untrue. Regular "RCA WIRING" is usually coaxial in construction unless you buy the very cheapest junk you can find. Every audio cable I have terminated or re-terminated over the past 50 years has been coaxial.

My point wasn't based on the impedance. It was that a coaxial cable should be used. If both cables are in fact coaxial, then you're probably right that it doesn't matter, but it's not 100% clear to me that the RCA cable is a coaxial cable. If you're given a choice between 2 cables and one of them is 100% guaranteed to be the one you want and the other isn't 100% guaranteed, why would you pick the later? Definately is better than usually.

Quote:


Technically, there is no such thing as a subwoofer cable and either the RCA or the digital will work fine.

RCA cables are not defined by the type of cable, but by the type of connection. So if there's no such thing as a subwoofer cable, then one could argue there's no such thing as an RCA cable either.
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Old 11-18-2011, 09:59 AM
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Quote:
Originally Posted by Kal Rubinson View Post

Technically, there is no such thing as a subwoofer cable and either the RCA or the digital will work fine.

Why? Analog audio connections are not 75ohms so that spec is irrelevant.

There is no difference. A digital cable with RCA connectors is an RCA cable. The problem is that it is not a symmetrical issue. Standard analog RCA cables are generally not suited for digital use because they need not adhere to any impedance spec.

True but, to a degree, twisted pairs do this, too. Note that both suggested cables have "100% double shielding using a solid mylar wrap overlaid with tin-plated, oxygen-free copper braiding."

Untrue. Regular "RCA WIRING" is usually coaxial in construction unless you buy the very cheapest junk you can find. Every audio cable I have terminated or re-terminated over the past 50 years has been coaxial.

So, the bottom line is that either of these cables will be fine for the subwoofer and the only difference is the single core conductor of the digital necessary to have the 75ohm spec.

Great post Kal. I guess some don't realize that you have been at this for 50 years and that you are a reviewer for Stereophile magazine. And that your response didn't push anyone towards an expensive cable when it isn't necessary.

Keep up the great work
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Old 11-18-2011, 10:27 AM
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Quote:
Originally Posted by spyboy View Post

your response didn't push anyone towards an expensive cable when it isn't necessary.

The two cables cost the same.
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Old 11-18-2011, 10:45 AM
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Quote:
Originally Posted by KidHorn View Post

The two cables cost the same.

The OP also mentioned blue geans and monoprice which are either more expensive (blue jeans), or less expensive (monoprice) than the Emotiva.

Kal also has followed the greater cable/speaker wire/power cord controversy for decades. So, I found his post refreshing seeing as he could have recommended something more expensive.

You might be surprised how many people use monoprice cables for most of their wire/interconnects with no hum or other noise.
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Old 11-18-2011, 04:43 PM
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Quote:
Originally Posted by spyboy View Post

You might be surprised how many people use monoprice cables for most of their wire/interconnects with no hum or other noise.

Hum/noise is easy. The objections are usually to less palpable features.

Kal Rubinson

"Music in the Round"
Senior Contributing Editor, Stereophile
http://www.stereophile.com/category/music-round

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Old 11-23-2011, 06:09 AM - Thread Starter
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Thanks so much for taking the time to give such great information! I definitely feel better informed.

I'm thinking I might give the Emotiva coax cable a shot.

Cheers!
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Old 11-23-2011, 12:22 PM
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Quote:
Originally Posted by vertigo4 View Post

Thanks so much for taking the time to give such great information! I definitely feel better informed.

I'm thinking I might give the Emotiva coax cable a shot.

Cheers!

You would be surprised how little difference there is with cables, interconnects and speaker wire.

Years ago a few guys took a metal wire coat hanger and used it as a "digital coaxial cable". It worked perfectly.

In a well done comparison of various speaker wire, 8 gauge copper car battery jumper cable was compared to esoteric woven/braided speaker wire as well as a number of other kinds of wire, I think including the cheapest 12 gauge stranded copper speaker wire. The biggest difference was the jumper cable was down 0.25 db at 20,000Hz.

There is a good reason MonoPrice does so much business.
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Old 11-23-2011, 04:06 PM
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I am going to make my own sub interconnect. A friend of mine used to use a name brand cable but got a lot of hum from his sub woofer. He made his own interconnect with quad shielded RG59 and soldered two RCA fittings to each end. As soon as he used this cable, the hum went away. I suppose it was a issue with the name brand cable not using enough shielding.
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Old 11-23-2011, 04:09 PM
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I used Belden 1694A for my sub cables (and all my interconnects) and am hum-free.

$.64/lf @ markertek, all wire colors for the new coding system available (if you care)...
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