Shielded speaker cable, how does the shielding work? - diyAudio
Go Back   Home > Forums > Loudspeakers > Multi-Way
Home Forums Rules Articles diyAudio Store Gallery Wiki Blogs Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Thread Tools Search this Thread
Old 10th March 2004, 07:17 PM   #1
diyAudio Moderator
Cal Weldon's Avatar
Join Date: Jan 2004
Location: Near Vancouver
Default Shielded speaker cable, how does the shielding work?

I remember years ago when we used to run wires through auditorium floors, that you always used shielded speaker cable because it was in proximity of power cables. So I understand what it is used for and why but it's the how that has me confused.

I thought that for a shielding to be effective it required a ground loop to be created. So, if I used the shielded cable, I can hook the amp end up to a ground but I'm not sure what to do at the speaker end. Am I on the right track or does the hook up at the amp do this for me. Again, I thought there had to be a loop. It's so far back, I simply can't remember.

Please help, the neuro-transmitter synapse thing isn't at top speed today.

  Reply With Quote
Old 10th March 2004, 07:25 PM   #2
diyAudio Member
Nappylady's Avatar
Join Date: Feb 2003
Location: Salt Lake City
Send a message via ICQ to Nappylady Send a message via AIM to Nappylady Send a message via MSN to Nappylady Send a message via Yahoo to Nappylady
No, in fact, a ground loop is a bad thing. There will be, in this instance, three conductors--the red and black wires form the circuit, and the shield is simply connected to ground, but ONLY on one end. If you connect it on both ends, it could actually make the AC hum even worse.

You should be aware that the shielded lines that were run before were probably line-level or microphone-level, and so they needed sheilding. Amp-level signals usually don't require shielding because the mains hum from adjacent wires is usually miniscule.

If you sheild wire that will be used by a power amplifier to drive speakers, you should probably NOT shield it, as it can cause the amplifier's load to be overly capacitative, hurting high frequency performance, and potentially causing oscillation. This oscillation can destroy the amplifier.

If the wires are running next to AC power for more than a foot or so, then perhaps some shielding is called for; I'd say try it without, and only shield it if you find it necessary.
  Reply With Quote
Old 10th March 2004, 08:52 PM   #3
markp is offline markp  United States
diyAudio Member
Join Date: Oct 2003
Location: L.A., CA
Don't shield high level signal wires like speaker wires. In addition to the capacitance problem there are other issues. Very high signals can generate a field larger than the diameter of the shield.
If it sounds good... it is good!
  Reply With Quote
Old 11th March 2004, 07:47 AM   #4
lucpes is offline lucpes  Romania
diyAudio Member
Join Date: Dec 2003
Location: Romania, EU
Send a message via Yahoo to lucpes
Actually, it would be best to make sure that your cables don't mix up too much with power line ones, and note that at these impedances & currents (amplifier close to 0 ohms, speaker ~4-8Ohms, some serious amps) shielding won't matter anyway.
  Reply With Quote
Old 11th March 2004, 08:01 AM   #5
SHiFTY is offline SHiFTY  New Zealand
diyAudio Member
SHiFTY's Avatar
Join Date: Jul 2002
Location: New Zealand
In old auditoriums, and some modern PA equipment, the amplifier has a large output transformer which steps the voltage up to 100V line. Each speaker has a small transformer which steps down the voltage. This is done so you can have 100 speakers on a single cable without too much resistance losses.

It also makes the speaker more prone to interference, as spikes cause excitation in the transformers. So that might be why you used shielded cable. Or maybe your boss just got a sweet deal on some shielded cable from his friend?
  Reply With Quote


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Shielded input cable Rob11966 Tubes / Valves 2 14th August 2007 10:37 AM
shielded power cable rkreim Vendor's Bazaar 6 23rd March 2007 02:33 AM
shielded cable vs ribbon cable Leolabs Parts 2 23rd July 2006 05:21 PM
Multiple Inputs in One Shielded Cable? Sherman Tubes / Valves 8 18th August 2005 01:21 PM
Should Intercnnects & Speaker Cable be Shielded? ralph-bway Everything Else 4 5th January 2004 02:28 PM

New To Site? Need Help?

All times are GMT. The time now is 09:06 PM.

vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999-2017 diyAudio

Content Relevant URLs by vBSEO 3.3.2