Bi amp question

Discussion in 'Audio Hardware' started by merlperl, Mar 13, 2017.

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  1. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    i have heard that when bi-amping you need to use an external active crossover network.

    My system is bi-amped and has been for some time. I have wired both amps directly to the speakers using one to power the top section and the pre out from that to send the signal to the bass amp then to the bass cabinets. Even though I am only using the passive crossover networks in my speakers, it sounds very coherent and sublime.

    I had previously bi-amped my Von Schweikert vr-4jr speakers using a musical fidelity a3.2 to the top section (mid/tweet) and a parasound hca750 to the bass cabinets. That sounded great and recently I wanted to get into tube gear so I replaced the musical fidelity amp with a Cary sli-80 on top., sending the pre-out signal to the parasound (looped through a musical fidelity x-10v3 tube stage)

    To me it sounds great but I am wondering if I am missing something by not using an external crossover and relying on the passive networks in the speakers?

    I'm not new to this hobby, having been an audiophile for 35 years but recently have been reading that you can't get coherent sound bi-amping and NOT using external crossovers, particularly when using different amps.

    Do my speakers just have great passive networks? Because to me,
    My system sounds great...very coherent with satisfying frequency distribution and incredible imaging.

    I'd love to hear any opinions or expert advice!

    Thanks
     
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  2. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    First starters, when using two entirely different amps you need a way to match their gain, which you are not doing. Using active crossovers will take care of that issue as well as provide greater accuracy and effiency. Right now your speakers are receiving full frequency signals from both amps, which seriously negates the main benefit of bi-amping.
     
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  3. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    Aren't the crossover networks in the speakers filtering out the unwanted frequencies? In Von Schweikert speakers the bass cabinet has its own crossover and the mid/hi has its own. Wouldn't that take care of filtering the frequencies?
     
  4. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    Yes, but they are passive and waste a lot of energy as the signals are filtered after the amps. With active crossovers the signals are filtered before they reach the amps, so no power is wasted.


    Any speaker that has a passive crossover does the same thing, there's nothing special about your crossovers being in separate enclosures.

    Don't ignore the gain matching I mentioned, it is critical.
     
  5. Linger63

    Linger63 Forum Resident

    Location:
    AUSTRALIA
    As you are using words like "sublime" and "incredible" to describe your current SQ............ why change anything?

    FWIW if it was me though................

    1........I would be selling the amplifiers and simply getting one very good one.

    2.......Selling everything to assist in acquiring an active model.


    Option 1 will give improved SQ over your current arrangement.

    Option 2 will lift SQ to a whole new level.

    IME and IMHO.....passive bi amping is not worth wasting time on.
    Have a listen to a well built active design and you will hear just how far away you actually are.

    If you do decide to consider actives.........this article describes all the benefits quite well.

    ATC active vs passive

    Good Luck and happy listening..:)
     
    Last edited: Mar 14, 2017
  6. The FRiNgE

    The FRiNgE Forum Resident

    There may be some benefit with a bi-amp passive setup, only that the amps are not bothered as much by the crossover reactance and back EMF, since that's divided up. The hi freq section may be cleaner. This is not to negate the more significant benefits of bi-amp with active EQ.
     
    Last edited: Mar 14, 2017
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  7. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    Oh, no doubt there is some benefit to passive bi-amping, but only if the amps are gain matched.
     
  8. Linger63

    Linger63 Forum Resident

    Location:
    AUSTRALIA
    I agree with F1nut and The FRiNgE regarding potential benefits with passive bi amping.

    IME though.........I didn't consider the level of those benefits worthwhile and definitely not cost effective.
    I used 2 identical gain matched stereo power amps worth a combined $4K back when I messed with bi amping.

    I found that (in my case) simply moving up the range to a bigger better $4K model gave MUCH more benefits!!!!
     
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  9. monte4

    monte4 Senior Member

    Location:
    Ontario Canada
    Agreed. But as stated earlier, one great amp will sound better than 2 lesser amps being passively biamped. I went from passive single amp to active biamping on my Linn setup. I didn't even bother with passive biamping as it wasn't worth the cost. An active biamped setup is well worth the cost if done right. The problem is that most systems (other than Linn) aren't designed for active biamping and care must be taken to do it right (especially when you add the outboard crossovers, not to mention that the crossovers in the speakers must be disconnected which means taking the speakers apart).
     
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  10. Lenny

    Lenny Forum Resident

    Location:
    New York
    I simply bi-wire my 4JRs Mk IV using a Sim Audio amp and preamp and I am satisfied with the results. My phono pre is all tubes.
    On the Van Schweikert (Audio Circle) site there is a long thread on bi-amping begun by AVS himself. Perhaps you have seen that. He prefers tubes on top, SS on bottom and relies on the passive networks in the speakers. Level matching appears to be the challenge.
     
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  11. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    thats exactly what I'm doing and it sounds pretty great! Just am wondering if I am missing something. All the levels seem right despite the very different amps
     
  12. Apesbrain

    Apesbrain Forum Resident

    Location:
    East Coast, USA
    You are not "missing" anything. People have explained alternative ways of doing what you are doing, but your way also works. It may be the case that your two amps are not gain-matched, but you like the sound as it is. Why worry?
     
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  13. F1nut

    F1nut Forum Resident

    Location:
    The Mars Hotel
    It would be next to impossible for your two very different amps to be gain matched as they are right now even though you like the sound.
     
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  14. Apesbrain

    Apesbrain Forum Resident

    Location:
    East Coast, USA
    Exactly, think of it as using a tone control.
     
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  15. Frobozky

    Frobozky Forum Resident

    Location:
    Indiana
    Without knowing more about the drivers and X-overs in your speakers, characteristics of your listening room. and the specifications of your amps, it is difficult to know exactly what is happening? It may be a serendipitous situation where some factor in your specific set-up ended up compensating for a weakness. For example maybe the gain in the bass amp is greater and that compensates for room absorption? Maybe your speakers do not test very flat, and you lucked into an amp combination that by splitting the highs+midrange from bass got things closer? Since you like the sound better, consider yourself lucky. With an electronic crossover, matched amps, and much testing, you might find an even better combination, but you're happy now!
     
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  16. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    Ok I guess you're right. What matters is how I like the sound and I like it. The bass amp actually has variable set and forget attenuators. Right now they are set to full on.

    And I like it so... I guess never mind
     
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  17. tmtomh

    tmtomh Forum Resident

    As others have noted, if you really like it, leave it alone and enjoy!

    What @F1nut says is important though - they should be gain-matched or else the woofer or tweeter will dominate in a way that's unbalanced. It could be that you got lucky and that the amps are gain-matched, or close to gain-matched, or not gain-matched but in a way you find pleasing.

    A simple way to get a sense of the gain-matching is to get an inexpensive handheld SPL meter and look online for an audio file that contains test tones at a bunch of frequencies (at least 10 octaves). You can play the tones on your setup and take note of the SPL levels at each frequency. There will be variations no matter what because the frequency response of your speakers (and the room) is not going to be perfect. But if you notice that most or all of the frequencies above the crossover point suddenly register significantly higher or lower on the SPL meter, you'll know there's a gain mismatch. Conversely, if the SPL levels stay close, you'll know you got luck and the amps are more or less gain-matched.

    Finally, as others have noted above, amps of different designs and characteristics very well might produce a different kind of sound, and so running each speaker driver with a different type of amp might provide sonic benefits (or sonic chaos).
     
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  18. House de Kris

    House de Kris VVell-known member

    Location:
    Texas
    Many people believe that the passive crossover is the single greatest limiter to superior sound in the home. Thus, perhaps that is why people suggest that you "need" to use an external active crossover. But really, if you are happy with how it is sounding to you now, I don't think you should feel compelled to comply with their suggestions.

    I read the opening post in AudioCircle that Lenny suggested written by AVS. In a passive bi-amp system, it makes most sense to use amps of equal power output. But, AVS suggests using, for example, 200W solid state on the bottom and 20W hollow state on the top. In my opinion, this is rather a rather irresponsible suggestion, as it wastes a considerable amount of capability of the solid state amp. Merlperl's situation of using a 75WPC and 80WPC amp seems to be considerably more reasonable.
     
  19. acceler8

    acceler8 New Member

    Location:
    South East, USA
    Even the most perfect speaker crossover is a balance of trade-offs. I use a mini-DSP 2x4HD with a tube SET amp driving full range speakers and a SS amp to drive stereo subs. The 'mini' is quite powerful, and sounds great! I currently have an asymmetrical crossover with the SET @ 60hz 24db slope and the SS @ 120hz 24db slope (which allows some overlap and helps with the overall balance.) The only downside to the 'mini' is that you'll find you never stop tweaking it!
     
  20. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    I must have gotten just plain lucky!

    And I have this disease...even though I love the sound of my system I obsess over it.

    I have been perfectly happy Bi-amping these speakers using the built in crossover networks until I read someplace that that shouldn't work. All of a sudden i was wondering if I did it "wrong" and if I did then why does it sound so amazing? Sometimes it's better to remain blissfully ignorant.

    Im gonna go play this Buddy Rich record I just bought.

    Probably will enjoy it too!

    Probably.
     
  21. Linger63

    Linger63 Forum Resident

    Location:
    AUSTRALIA
    LOL...........and sometimes it's not!!!!:p

    Anyway........It's ALWAYS whatever makes YOU happy. :agree:
     
  22. CoolJazz

    CoolJazz Forum Resident

    Location:
    Eastern Tennessee
    So the Cary amp has a gain of 32db in Ultra Linear mode and 31db in Triode. Can't find a spec on the Parasound, but an up line one has a gain of 31db.

    But let's say their is a 2db mismatch. So the next question would be where the speaker crossover freq is. Well those speakers are listed as crossovers at 200hz and 2.2k. Likely, we're referring to separately powering the top end above 2.2k and below. So what does a couple db difference at that freq make? That's the question of amp gain mismatch.

    If it was the 200hz, then you'd be talking a richness or light footed difference. In either case, it's no different that using that line level active crossover and having the gain knobs between sections slightly mismatched. Some thinness or brightness, sure. Dire consequences, no...not at all.

    Getting out a crowbar ( :sigh: ) and digging into the cabinets and bypassing the crossovers means you have the potential to miss out on any built in corrections the manufacturer carefully built in and tweaked. EQ, phase shifts, efficiency differences between drivers. All kinds of things. Now can you correct for those things in some crossovers? Sure. So...you think you can do a better job than the manufacturer? They spent how long getting those things all just so and you can do better? Might be simple...might not.

    Now, look at the bi-amplification that you're already doing. Yes, the front end of each amp has full range information going to it...that an active crossover would change. But the front ends have very little distortion or IM problems. They're voltage gain stages with controlled loading. Very little difference there between full range operation or partial. The output stage also has full range info presented. But...the big difference is that the load on the output stage has a big portion of the load removed by the following crossover. The IM caused by the current demands on the output stage is changed for the better...significantly! Is it slightly cleaner with the information not present via preceding crossover? Sure.

    But the web folklore that it's somehow wrong to simply biamp.... Nahhhh!!! If your gain is reasonable matched...just enjoy! And try other amp combo's too. Their voicing may bring greater pleasure or not depending. The big spec as pointed out is the gain number. But simple biamping is not a bad thing to do at all. It actually has some strong points going for it! It isn't going quite as far as going all out and doing a truly full blown active crossover and biamping. And oh...in this case even that would not remove all components between the amps and the drivers since we have yet another crossover between drivers involved. That's where the next big step is...getting the amps directly coupled to the drivers. But vastly more complex in a multi-driver situation.

    You've got some great speakers. Enjoy them for what they are.

    CJ
     
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  23. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    Cool jazz thanks for the words of comfort! I do enjoy the sound and will continue to. As for what I might be missing the system to my ears sounds better than it ever has and that is progress
     
  24. merlperl

    merlperl Forum Resident Thread Starter

    Location:
    Omaha, NE
    For the record, here are the Spec's on my system:

    Parasound hca 750
    Input sensitivity .775v
    Output 125w into 4 ohms (driving bottom section of vr-4jr - 4 ohms). Has two attenuators in back, both set to full open, which takes them out of the signal path.

    Cary sli-80 Input sensitivity .45v
    Output 40w into 8 ohms (driving top section of vr-4jr - 8 ohms)

    Vr4jr crossover points
    200hz, 2.2khz

    And I invite any of you in or near Sherman oaks,CA to come by, have a beer and a listen and let me know what you think!
     
  25. ltusler

    ltusler Forum Resident

    Location:
    Minneapolis
    This, and if you really want to go wild look at the miniDSP DDRC88A with BM, it also has DIRAC room correction, the tweaking never ends and is great fun. You can have as many setups as you wish and save and recall them at will.
     
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