Crossovers And Bi-wiring Question

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  • David Meek
    Moderator Emeritus
    • Aug 2000
    • 8938

    Crossovers And Bi-wiring Question

    Once again, I come before the poobahs . . . .

    Gang, I've been bumping around the edges of this question for a while and can't get a good answer, so I'll ask the horse's mouth - when you remove the jumpers on a set of speakers and either bi-wire or bi-amp them, don't you eliminate the (or one of the) crossover from the mix? And in doing this, don't each of the drivers wind up putting out a "full range" signal instead of one rolled off at some point by the cross-over?

    Curious in Houston. . .




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  • ThomasW
    Moderator Emeritus
    • Aug 2000
    • 10934

    #2
    Removing the jumpers doesn't take the passive XO out of the circuit in most speakers.

    The benefits from biwiring (running separate wires to woofer and tweeter sections) are minimal at best.

    The benefits from removing the passive XO to the woofer and actively biamping with an active XO can be quite impressive. BUT one must use an active XO that has it's circuitry tweaked specifically for the woofer/cabinet. Use of so called 'generic' active XO's isn't a proper way to go. As a result this isn't an inexpensive undertaking




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    • David Meek
      Moderator Emeritus
      • Aug 2000
      • 8938

      #3
      Thomas, then why even bother? If the crossover isn't by-passed what real difference does it make? Just marketing hype?




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      • Dennis H
        Ultra Senior Member
        • Aug 2002
        • 3791

        #4
        Thomas has it just right (of course.) I would add that passive bi-amping, not bi-wiring, can improve the sound if you like to play it loud. With a single amp, if you clip it, all the nasty high frequency stuff from the clipping goes right to the tweeter and sounds really bad. Bi-amping, if you clip the woofer amp, the HF garbage only goes to the woofer and much of it is filtered out by the lowpass filter of the woofer's crossover so it doesn't sound quite so bad. Of course, we shouldn't be clipping our amps at all but some music with loud transients can do it more often than we realize.

        Comment

        • JonMarsh
          Mad Max Moderator
          • Aug 2000
          • 15259

          #5
          The benfits of bi-wiring (whcih is what we're talking about here) are somewhat subtle, but not necessarily inaudible. They are most pronounced if you have or require long speaker leads. With a long speaker lead, the overall source impedance going back to the amplifier is increased, and there is more potential for interaction between the HF and LF.

          Now, if you biwire, each section has it's own connection back to the relatively low impedance source of the amplifier. As an example, Charles Hansen reports that bi-wiring with Cardas Neutral Reference speaker cables will often produce better results overall than simply a straight connection of Cardas Golden Reference speaker cable, and at a net lower cost, even though two sets of cables are required in the former case. YMMV.

          OTOH, my opinion is that biwiring with zip cord is probably NOT a useful endeavor. My minimum recommended speaker cable configuration if you want to get hoity toity is something like Kimber 8TC. Low resistance, low inductance, and about $12 a foot. Cheap, compared with the botique cables. I like using 4TC even for internal wiring in speakers.

          Regards,

          Jon




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          Comment

          • Lex
            Moderator Emeritus
            • Apr 2001
            • 27461

            #6
            Hmm, good thread. Thomas, good response. Pete, good point on the clipping avoidance at higher volumes relative to the separation. I'm not sure the passive crossover won't still have impact, but if you say so.

            Jon, you really need to work on other examples. This Ayre cardas thing is getting old. :LOL: But seriously, I would add to that, a slight objection to the generic classification as most cables not built yourself being "boutique". For example. Wires like my Cattails, a 2 meter pair at 149.99, hardly budget breaking, hardly boutique. I could tell you the major supplier of the wire. But I will leave that to your imagination.

            By the time a person orders the wire, pays shipping on that, orders connectors, pays shipping on those, then has to worry about the asthetics of the cable if that means anything to him, pay for materials there. He might be hard pressed to actually build these for 149.99. Especially if you consider his time involved, and the opportunity cost of what he could be doing if he wasn't building cables. So, just a case in point, that the term Boutique is really overused, and not truly accurate about "all" cables. Now cables costing 1000.00, I can begin to see the boutique lable as applying.

            My final point is, kimber 8TC at 12.00 a foot sounds pretty cheap on the surface. But by the time the cables are completed with connectors, shrink, you've paid for shipping on everything needed, your looking at a substantial amount more. Probably more like 20.00 a foot just guessing for a standard 6 foot set.

            Lex
            Doug
            "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

            Comment

            • JonMarsh
              Mad Max Moderator
              • Aug 2000
              • 15259

              #7
              Gosh, I thought this was the DIY section of HTGuide, not Audio Hideout, Home Theater, or AV Chalet! :??


              BTW, Lex, what's the approximate loop back resistance and inductance of a two or 2.5 meter pair of Cattails? :W


              Regards,

              Jon




              Earth First!
              _______________________________
              We'll screw up the other planets later....
              the AudioWorx
              Natalie P
              M8ta
              Modula Neo DCC
              Modula MT XE
              Modula Xtreme
              Isiris
              Wavecor Ardent

              SMJ
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              Ardent D

              In Development...
              Isiris Mk II updates- in final test stage!
              Obi-Wan
              Saint-Saëns Symphonique/AKA SMJ-40
              Modula PWB
              Calliope CC Supreme
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              Natalie P Supreme
              Janus BP1 Sub


              Resistance is not futile, it is Volts divided by Amperes...
              Just ask Mr. Ohm....

              Comment

              • Lex
                Moderator Emeritus
                • Apr 2001
                • 27461

                #8
                Hmmm, I guess you got me there Jon. lol. In short, I was talking people out of DIY. What was I thinking. ops:

                I'd be glad to tell you that just as soon asI figure out how to measure it all I've got a pretty good meter, just not had time to do much with it.

                I guess I felt like I was grouped in there, and just wanted to clarify that. Sorry, never happen again.

                Lex
                Doug
                "I'm out there Jerry, and I'm loving every minute of it!" - Kramer

                Comment

                • David Meek
                  Moderator Emeritus
                  • Aug 2000
                  • 8938

                  #9
                  Originally posted by Thomas
                  Removing the jumpers doesn't take the passive XO out of the circuit in most speakers.
                  Originally posted by Jon
                  Now, if you biwire, each section has it's own connection back to the relatively low impedance source of the amplifier.

                  Ooof - wading into (for me) deep water, here. Thinking further about this, if each section is separately connected back to the source, why at that point, wouldn't you want the cross-over out of the circuit? To keep the bass- and mid- drivers from outputting the same notes and cancelling (or re-inforcing) each other, maybe?

                  Sorry if these are silly questions. I'm just trying to learn . . . .




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                  Comment

                  • JonMarsh
                    Mad Max Moderator
                    • Aug 2000
                    • 15259

                    #10
                    Hi David,

                    The crossover filter divides the frequency ranges for the drivers, keeping them operating in the safe part of their passband (tweeters will blow up real quickly if you feed them lows at any significant power; most midwoofers have resonances in the upper part of their range (just above the typical tweeter crossover) which will add grit and grunge to the sound).

                    Additionally, the passive crossover for most speakers has some level of baffle step compensation; that is, it provides equalization to compensate for changes in radiation resistance and effective level that occur as a frequency dependent function based on the size of the speaker front panel. Example, with a baffle width of 10-12", above 1 kHz, the driver's radiate into two pi space; below, they must radiate into 4 pi space (omnidirectional) this results in a neary 6 dB droop in the response, depending on how far they're put from the rear wall. If the speaker is flush with the rear wall, no baffle step compensation is necessary, but this is usually not the case.

                    Voltage drops in cable occur as a function of current times both the inductance and resistance, the former being frequency dependent. When you biwire, the HF current only goes through one cable (though it sees the full voltage range); the LF range current goes through the cable connected to the woofer terminals only.

                    If you use monoblock amps with very short speaker cables, I don't think you'll see any benefit to bi-wiring. But for longer runs, you probably will. It's all a matter of degree, and the overall "resolution" of the system, too.

                    There are so many things you can do that make small differences in performance, sometimes these differences can add up to something quite important. I think that intelligent use of bi-wiring when circumstances justify it can be easily as beneficial as an interconnect upgrade.

                    But this is something for you to evaluate over time, and by how the system sounds. It's the kind of thing where if you're considering it, borrow a set of cables, and hook it up for a weeks listening- see what you think, then go back to your original setup, and listen for a while again- if it takes that long. It may not. :W

                    ~Jon




                    Earth First!
                    _______________________________
                    We'll screw up the other planets later....
                    the AudioWorx
                    Natalie P
                    M8ta
                    Modula Neo DCC
                    Modula MT XE
                    Modula Xtreme
                    Isiris
                    Wavecor Ardent

                    SMJ
                    Minerva Monitor
                    Calliope
                    Ardent D

                    In Development...
                    Isiris Mk II updates- in final test stage!
                    Obi-Wan
                    Saint-Saëns Symphonique/AKA SMJ-40
                    Modula PWB
                    Calliope CC Supreme
                    Natalie P Ultra
                    Natalie P Supreme
                    Janus BP1 Sub


                    Resistance is not futile, it is Volts divided by Amperes...
                    Just ask Mr. Ohm....

                    Comment

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