Planar Speaker Asylum Welcome! Need support, you got it. Or share your ideas and experiences.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Planar Speaker Asylum ]

---

[ Alert Moderator ]

---

Good questions.

Posted by Al Sekela (A) on March 20, 2007 at 13:40:24

In Reply to: Re: Cable resistance will not make the amps work harder. posted by Dr.Jazz on March 19, 2007 at 15:06:10:

Sorry I did not think about active shielded speaker cables. What I know about this is mostly second-hand, as a good friend of mine designs and makes his own active cables. My own speaker cables are damped with carbon fiber, which is a weak sort of shielding, and with dynamic loading. I do use actively-shielded power cords.

The DC bias in active cables makes the wire insulation more linear as a dielectric, but also can make it microphonic. The shield electrode supports the DC bias as well as shields against external noise. The problem with the shield is that it supports RF resonance modes of its own and with the internal conductors. These resonances can make RF noise problems worse unless the cable design includes damping mechanisms. I don't know if Synergistic Research cables include damping mechanisms in their designs.

Shielding also increases the total capacitance of the cables. This might present a problem with some amps, where it could drive them into instability. The shielding is not likely to be effective against magnetic fields. Therefore, its main use in speaker cables appears to be to support DC bias to make the insulation behave more like a perfect dielectric. If you have ever compared PVC to Teflon insulation, you will know that this is not a small benefit.

You are correct that a wall-wart bias supply is a possible entry path for RF noise. I don't think you can use batteries with these cables. The power connection and feed wires for the bias supply have to be designed with care to suppress RF noise carried on the house power wiring.

As for active crossovers, the main benefit is to allow direct coupling of the amps to the speaker elements. The direct-coupled amps will damp the speaker elements outside their operating ranges, while some of the Magnepan passive crossover designs prevent adequate out-of-band damping. I modified my MG-20 passive crossovers to include R-C shunt elements at the outputs of the bass panel low-pass filters, and this made a definite improvement. The stock design has a series inductor at the output, so higher frequency resonances in the bass panel cannot be damped by the amplifier.

The main draw-back, as I said before, is the additional active electronics and cabling required to implement the crossover. Magnepans can be tweaked to be very revealing speakers, and would easily reveal the distortion and noise added by the active crossover, IMO. Proponents of active crossovers always wave this argument away. I simply don't know if an active setup can be made to be as natural-sounding as a teaked passive setup.

This post is made possible by the generous support of people like you and our sponsors:

VH Audio

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---