Speaker Asylum General speaker questions for audio and home theater.

---

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

---

[ Alert Moderator ]

---

Re: ?????

Posted by Dave Kingsland on March 9, 2007 at 10:43:14

In Reply to: Re: ????? posted by Kal Rubinson on March 9, 2007 at 09:26:24:

Your math is fine but your assumptions are far from real world. An 4ohm system cannot be 8 + 8 across all frequencies (even simplifying it to resistance and not impedance) since each leg has an increasing resistance with frequencies beyond its passband, even at crossover.
...
The cable impedance does not change appreciably with frequency regardless of the crossover. It is the load represented by the speaker that changes. The amp sees that change but, since it is paralleled by a complementary change in the parallel leg, it is minimal.

Kal, because the impedance is not constant, my example is only intended to represent the conditions at a single frequency. I chose equal loads on both the high and low end because I was making a point about the effect of bi-wiring around the crossover frequency - where (as you said yourself) out the loads are roughly equal.

Also, a cable resistance of 1ohm is HUGE! Using this assumption, unreasonably magnifies all the effects you describe.

It was an example. Make the number as big or small as you wish. My point is that the single wire and bi-wire circuits are NOT equivalent, as you seemed to be claiming.

Second, any impedance variation seen by the amp in one leg is compensated for in the other and has nothing to do with the fixed resistance of the cable.

Wrong. At a frequency outside the pass band of the low frequency crossover network, the impedance of that network is very large, so the load impedance is just the impedance of the high frequency network in series with a single cable. At that frequency, it doesn't matter whether both networks share the same cable or not because there is no load from one of the networks. But around the crossover frequency, both the high and low frequency networks present a similar load, and then the bi-wire configuration will result in a smaller impedance. As a result, bi-wiring will produce an increase in speaker output in the frequency range where the crossovers overlap. It may not be big, but it can be explained and measured.

In fact, one might argue that a typical crossover benefits from single-wiring since that assures the intended complementary shunting of out-of-bandwidth impedance rises of one network/driver leg by the other. Introducing real world cables, with their complex impedances, between the legs would certainly complicate that process. Of course, I would think to suggest something as radical as that. :-)

One might conversely argue that a speaker which supports bi-wiring may have been tweaked or voiced by the designer to sound its best in a bi-wire configuration. But I have no idea whether this is common.

Dave

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

Signature Sound

[ Signature Sound Lounge ]

---

[ 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 ]

---