Passive Biamping: How much improvement?

Discussion in 'AV Receivers' started by Jigesh Patel, Jun 18, 2003.

  1. Michael R Price

    Michael R Price Screenwriter

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    Crossover modifications are great! But passively highpassing your midwoofers at 70Hz is crazy. [​IMG]
     
  2. Brett DiMichele

    Brett DiMichele Producer

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    Lowpassing at 70 isn't nuts.. (Highpassing a mid at 70?
    that would just be WEIRD!) [​IMG]
     
  3. Chu Gai

    Chu Gai Lead Actor

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    hey I know it's been done Richard, but it's not for the feignt of heart and certainly not for someone who's going to rely upon something called 'builders ear'. nice link though...ought to run that by Lee, seeing as he's contemplating the 3.6's. critical to the success of something like that, i think is having the ability and desire to run various measurements. too often i see people doing active approaches with off-the-shelf x-overs and invariably they make little effort to accurately determine the transfer functions. i know it sounds good to their ears, but those are builder ears.

    i agree with your general statements about the benefits of active crossovers, but few have or want to obtain a deeper knowledge. maybe we're just quibbling over ½ empty and ½ full. might be a project for those white van speakers!
     
  4. Chuck Kent

    Chuck Kent Supporting Actor

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    After reading all of the above, I thought I'd throw in a couple of thoughts...

    First, there is an easy (or should be relatively easy) to do biwiring, passive biamping and active biamping comparisons. Drive to your nearest Linn dealer. Linn makes speakers, crossovers and amps that allow all 3 pathway choices. (One can start with a regular mono-wired speaker, move up as the budget allows to biwiring, passive biamping and finally go active.) The dealers I've been to over the years have always been happy to demo their wares. While their line may not be something that we'd all agree that we'd have in our living rooms, the comparisons are valid and the quality of their products is excellent. (I don't own Linn but I do admire their product line for it's ingenuity.)

    Last thought is my personal opinion on this general topic.

    I'm not golden eared but I seem to be able to hear things that many of my friends and family don't. That said, biwiring and passive biamping don't hold improvements I can hear with any certainty. But active biamping is a whole 'nuther thing. I've heard a few good quality setups over the years and it is better. Literally on just about any level I can think of. But I'm not a speaker designer and don't want to be. I didn't want to make the money investment (or more to the point, couldn't) to go manufactured "active", so I searched out and eventually went with speakers that have passive 1st order crossovers. To my ears, these speakers have a sound that I find very appealing. (BUT and that's a big BUT, they aren't a free lunch either. 1st order designs have SPL limitations due to the large frequency range each driver must cover (the tweeter is the most vulnerable.)) I'm very pleased with my setups, but they wouldn't be for everyone. But I do feel that 1st order designs are about as close to active as passive can get...

    (BTW, all of my comparison comments are based on music listened to thru a stereo setup. While I do like music surround alot (especially DPL II Music mode) 2 channel thru 2 channel still sounds very very good to me.)
     
  5. Michael R Price

    Michael R Price Screenwriter

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    Is the 1st order design best because there are less distortion inducing components in the signal path, or because there's less phase distortion? Do you think an optimum active system would have shallow or steep slopes?
     
  6. Chuck Kent

    Chuck Kent Supporting Actor

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    I'm no scientist but my own thoughts lean toward the phase side. But truthfully, I don't know for sure. From a passive point of view, 1st order crossovers are about as close as we can get to no crossover at all. (There have been a few speakers out there that are crossover free. But they seem to be few and far between.)

    Still, I'm reasonably sure that the active setups I've heard used higher order filtering. And if it's done right, higher order filtering shouldn't be a limiting factor in an active setup like it could be in a passive one.

    As I mentioned above, 1st order designs have SPL limitations. All drivers still get signals 2 or more octaves from their best operating frequency range (especially worrisome is the vunerable tweeter.) Since one of the goals of going active is higher, more distortion free output, I would assume that most active setups use more agressive filtering than 6 db/octave (1st order.)
     
  7. RichardHOS

    RichardHOS Second Unit

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    Once you go active, steeper slopes become much more desireable (with passive, the number and size of components required to get a steep slope have some pretty nasty effects on the signal). Using 24dB/oct slopes it should (theoretically) be a much less challenging task to reproduce square wave response accurately.

    That's another reason I'm not convinced that the transition from passive to active crossover should be all that frightening... once active, you have at your disposal a class of crossover slopes that the original manufacturer simply didn't have available due to the limitations of passive networks. It may not be such a challenge after all to "one up" the factory crossover. It is a simple measure to calculate the stock crossover points, so you at least have a place to start.

    BTW, there are also line level delay circuits to do baffle-step compensation, for those who were asking about this. Pretty much anything that can be done at speaker level can be done at line level, and with less negatives. The inverse is not true though.

    Good modeling tools would certainly be useful for anyone seeking to go down this path.
     
  8. BruceD

    BruceD Screenwriter

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    Chuck,

    I may not understand the reason either (maybe phase), but I also happen to prefer 1st order crossovers in my speakers. If the speaker drivers are over-designed enough (like Dynaudio) high SPL levels are less of a problem.

    To complement my 1st order 2-way main speakers(-3dB @32Hz), I also happen to use an active 4th order L-R crossover @60Hz to my sub(s).

    Maybe the best of both worlds? Who knows, but I like it.
     
  9. Keir H

    Keir H Second Unit

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    Guys, question for those who know about Linn speakers..my Keliedhs have options to passive biamp or go aktiv using Linn amps. If I go the passive biamping route, will I get any benefits driving each speaker section since my speakers are setup to take advantage of such configurations?
     
  10. Frank_S

    Frank_S Supporting Actor

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    Brett said,
     
  11. Chuck Kent

    Chuck Kent Supporting Actor

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    Keir H:
     
  12. Jigesh Patel

    Jigesh Patel Stunt Coordinator

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    Thanks a lot friends...and thank you Frank for trying it out with a 200wpc amplifier. Good debate and wealth of information so far.

    I just added a Sony 222ES SACD player so monetarily I need to postpone biamping for the time being by adding two additional200wpc channels to Sherbourn 5/5210 (although sonically it might enhance my SACD experience!).

    Thank you.

    Jigesh
     
  13. Chu Gai

    Chu Gai Lead Actor

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    Well this is an area, as Brett and Frank and no doubt others, where personally, I'm not sure if the term is improvement or different. It can definitely be a very personal semantical issue where subtle shadings of the words may suggest positive or negative connotations. Far be if from me to argue or debate individual issues of preferences. What is obvious to me, is that both of you have made an alteration in the 'sound' of your system and if it's good to your ears, then by all means you've only yourselve's to satisfy. Until Brett gets married that is!
     
  14. Frank_S

    Frank_S Supporting Actor

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  15. RichardHOS

    RichardHOS Second Unit

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    I think there's little doubt that with such highly mis-matched amplifiers, there is going to be an audible change. Better, worse... depends on the amps, speakers, and individuals I suppose.
     
  16. Chu Gai

    Chu Gai Lead Actor

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    I'm sure I would enjoy it Frank. I simply think that things changed for the individual and I'm loathe to make it a blanket generalization of better. After all, you're running tubes on top and SS on the bottom where the bottom half has no audible interaction with the speakers per se, while the top half, depending on specific considerations can have audibly subtle or profound interactions. And if you haven't or chosen not to match gains it gets more interesting. When someone unknowingly mismatches gains during a biamp setup and then comes back and says gee, the violins were so much more articulated, is that something to hang one's hat on as a reason to champion passive biamping? Are those alterations benefits? Maybe it's not so bad if people know or get a valid gut feeling as to what's going on when they do something.

    I'm not looking to spin science or invent questionable theories. If I make a factual error, then I'd hope you'd step up to the plate and show me where. There's all kinds of experience Frank, sighted, unsighted, controlled, etc. Myself, I like to make sure that if i'm hearing something, it's real and not a result of my biases. There's enough malarkey in the audio world that doesn't need my financial support.
     
  17. Frank_S

    Frank_S Supporting Actor

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  18. Chu Gai

    Chu Gai Lead Actor

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    use a VOM or just ears?
     
  19. Frank_S

    Frank_S Supporting Actor

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    VOM off the taps. [​IMG]
     
  20. Michael R Price

    Michael R Price Screenwriter

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    I would imagine bi-amping would be an improvement in the objective sense because the amplifier distortion is reduced, and active bi-amping even more so. And I don't think the matching issues are so bad, provided the frequency response remains the same (matched levels and minor impedance variation). I'm waiting on parts so I can get to a humless bi-amp (passive, or active which I'll build soon enough) setup with my 15-40w Zen and the 400-? watt sym amp. I did try passive bi-amping with the Zen and my old solid state amp. It worked as advertised. The highs sounded like the Zen, and the mids and lows sounded like my old amp. If only the midrange could have been carried by the Zen, too. (See, that's why smarter people use 3-way speakers... or just good amplifiers all around.)
     

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