Kindly help me with the following question.
Why speaker cables are not shielded to block EMI/RFI just like interconnects?
I haven't heard any big improvements from shielding the XLR interconnect. But when I properly shielded the speaker cable I got HUGE improvements in dynamics and low-level detail.http://forum.stereophile.com/forum/showf...&PHPSESSID=
As a general rule, speaker level signals are considered high enough above the intrusion level (in voltage) of RFI/EMI signals. There can, of course, be exceptions to this rule but they would be considered special cases where good cable design and appropriate cable dressing can't achieve the desired levels of rejection. Twisted or braided conductor legs will minimize pickup from outside forces. However, almost anything the designer does to minimize RFI/EMI pickup - and most especially shielding the cable with a braid or foil - will increase the capacitance of the cable which might then make the shielded speaker cable a not so good choice in certain applications.
The above responses are good, just wanted to add that with SS, they should be stable enough, but with tube amps and trannies, the core material itself helps to minimize the problem, esp as the frequency rises.
Another problem, though, is the cable capacitance reflects back to the primary, loading the source (output tube) and reducing the high frequency response.
Hope this helps.
Thank you all for your responses.
I do not have a technical background and therefore I do not understand the relation of shield with capacitance of the cable.
What I want to know is that if I just wrap my speaker cables in braided copper shield or in household aluminum foil, without any modification to the inner construction/structure/geometry/design of the cable, will that arrangement help in shielding the cable from EMI/RFI?
Also in the above arrangement, shield is not touching the inner conductors of speaker cable but only makes contact to outer jacket, then how will the capacitance of cable change?
In a capacitor, there is usually two plates and an insulator sanwiched in between.
The added shield becomes another "plate" with a large surface area. The jacket is the sanwiched insulator between the internal wires and the shield.
Let's discuss what you're trying to achieve. Speaker cables seldom pick up RF/EM interference. When they do, dressing the cables to keep them away from the source of such interference typically resolves the problem. Since it's very difficult to get a 100% coverage with the methods you describe, there are probably better ways to minimize noise in your cables.
Interconnects are far more susceptible to RFI/EMi pick up than speaker cables. If you're having a problem, this is where I would suggest you begin making corrections.
Have you determined where the noise is entering the system? Have you tried other methods of noise reduction?
Without those answers, the best I can say is; try the shield.
Thank you sasaudio and Jan Vigne. I got your points and now I understand why cable manufactures do not shield speaker cables.
I am not having a noise problem with my old Yamaha amplifier and even if I poke my ear into the tweeters, there is no noise. It just occurred to me during my recent attempt to add a used Krell FPB-300 amplifier in my system that perhaps speaker cables are picking up noise. What happened was that there was hiss/hum/buzz from both channels even if only speaker wires were connected to output of FPB-300 and no interconnects were connected to any of FPB-300
I would tend to think the best approach is as the article suggests, simply unplug the offending AC cable.
I haven't heard any big improvements from shielding the XLR interconnect. But when I properly shielded the speaker cable I got HUGE improvements in dynamics and low-level detail.
did you ground the shield? if yes where?
Grounding of shield is sometimes necessary. Without grounding, signal can actually become worse because shield can behave as an antenna.
Excuse me, but as an experienced electrical engineer who has been an audio enthusiast for 50 years, I have never read so much nonsense in my life as I see in this thread. Anyone who claims they have heard a difference from shielding speaker cables is in my opinion not credible.
Speaker cables carry a fairly large current and are driven by an amplifier which has a very low output impedance. Almost NOTHING will influence or change the signal in them materially.
They are immune to any significant interference because their current is too large and their impedance is too low to be materially influenced by any other electrical signals that could influence them in the environment. Any competent engineer can do the math and prove it.
That is like suggesting that the current in the Mississippi River will need to be protected against the disturbance of the air due to passing birds that might modify the flow.
The ONE exception to this would be if you were within 100 yards of a VERY powerful radio transmitter AND your speaker cable length was the EXACT length to form a tuned antenna at THAT EXACT TRANSMITTER FREQUENCY. The chance of all of this happening is about a million to one.
The idea of shielding speaker cables is absolutly ridiculous.
ANY correctly constructed balanced (XLR) connection (cable) has an inherent noise rejection of 50 db or more when terminated in the usual appropriate circuits at both ends. It has a balanced design which totally rejects common-mode (noise) signals, and it is already shielded. Trying to add another useless shield is redundant and makes no sense at all.
Until you get a degree in electrical engineering and can understand the basics of what you are talking about, you might want to stick to discussing another subject. Trying to discuss something you have NO understanding of is useless and often counterproductive.
Wow, if i could have EVER hoped for a clearer explanation. .. Thank you "commsysman"
Now to properly connect my speakers to my Lava Lamp!