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1.6 passive line xo works!

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after my Donizetti's have been burned in, all the sonic parameters
i reported a few days ago have been gradually improving, so
passive biamping IS THE WAY if you want to know everything
about that what your 1.6 have really to offer; in particular, overall
musicality, well formed soundstage and huge reduction in the
usual congestion with grand orquestra recordings may be mentioned
as the main improvements
now i've just connected this very simple circuit with minute
resistors and caps between pre & amps to dispense with my
beloved northcreek coil & jensen/ansar caps (thanks Davey!!):
high pass: 5.49k ser - 4.53k par - 2.2nF ser
low pass: 5.11k ser - 68nF par - 49.9k ser - 22nF par
i've used CRAP components (just $3 as a whole), but
i'm planning replacing them by much better ones (thanks
Arbelos!!)
at the moment all i can say is that nothing bad happened when
i connected the circuits, one to each maggie (i was really chickening out to see
no protection at all between my amps outputs & my 1.6 drivers),
so the system is playing music!! give me time & i'll report back
best, paco

Follow Ups:

Re: 1.6 passive line xo works! CH Chang 17:04:36 02/04/01 (21)
Paco, after reading your description of your high/low-pass networks I'm a little confused with the notation you're using.
high pass: 5.49k ser - 4.53k par - 2.2nF ser
How is that to be interpreted? The "ser" and "par" I'd assume mean series and parallel. To me, it looks like you're saying the 5.49k Ohm resistor is in series with the output from your pre-amp. There is a 4.53k Ohm res in parallel with that resistor. And a 2.2nF capacitor in series with the resistors.
It seems like everyone has had positive experiences with passive bi-amping, that may be my next project after I replace the binding posts on my 1.6s. Thanks.
Chia-Hao
- Re: 1.6 passive line xo works! Davey 18:02:44 02/04/01 (19)
  This is it. Paco used a couple of resistors instead of the pot.
  http://indy.kpt.arl.psu.edu/daver/passive line level crossover.htm
  
  Davey.
  - Re: 1.6 passive line xo works! CH Chang 15:42:33 02/05/01 (7)
    Now that I see the original circuit diagram, it makes a lot more sense. But, brings up a few more questions.
    As stated elsewhere in this thread, this circuit should be placed immediately before the amps. But, how should the amps be connected to the MG1.6s? It seems to me that if you have this xo between pre-amp and amps, and the amps connected to the stock tweeter and woofer connections, you'd have two "identical" xo's in the signal path. If you still have the stock crossovers in the 1.6s, you'd have redundant xo's, correct? Would I need to by-pass the stock crossovers to use the passive line xo?
    Also, how would I scale the values of the caps/resistors to match amps with 100k input impedance? Is there a formula for this? Thanks again.
    Chia-Hao
    - resistor calculation MikeCh 16:27:31 02/05/01 (3)
      > Also, how would I scale the values of the caps/resistors to match amps with 100k input impedance? Is there a formula for this?
      
      The formula is:
      1
      r = --------
      2*pi*f*c
      - Re: resistor calculation CH Chang 22:07:34 02/05/01 (2)
        
        In Reply to: resistor calculation posted by MikeCh on February 05, 2001 at 16:27:31:
        
        Let me double check some values.
        r here is the input impedance of the amp, correct?
        f is the crossover point: 600Hz for lowpass and 1600Hz for highpass (are these the correct values?)
        c is the needed cap value.
        So, the formulas simplify down to:
        
        1
        c(lowpass) = -------------
        3768 * R(amp)
        
        and
        
        1
        c(highpass) = --------------
        10048 * R(amp)
        
        With 100k input impedance these evaluate out to
        c(lowpass) = 2.7E-9F = 2.7nF
        c(highpass) = 9.9E-10F = 0.9nF
        The value for the highpass doesn't seem too far off, but lowpass seems out of whack. I think I'm missing something here. One of my assumptions or calculations must be wrong, and after looking over it I can't figure it out. Any ideas what's going on?
        Thanks for your patience.
        Chia-Hao
        
        Re: resistor calculation Davey 10:16:49 02/06/01 (1)
        
        In Reply to: Re: resistor calculation posted by CH Chang on February 05, 2001 at 22:07:34:
        
        Another fellow has asked about recomputing for a 100k input impedance. I'll do that and update the page, and put up a little spreadsheet that will calculate for other values.
        Anything under about 50K and the insertion loss and other drawbacks make the circuit unsuitable in my view. I much prefer the active version myself.
        http://indy.kpt.arl.psu.edu/daver/Active Xover for MG16.htm
        Regards.
        Davey.
        
        Thanks! (nt) CH Chang 20:50:16 02/06/01 (0)
        
        In Reply to: Re: resistor calculation posted by davey on February 06, 2001 at 10:16:49:
        
        NT
    - Re: 1.6 passive line xo works! MikeCh 15:50:46 02/05/01 (1)
      The first requisite to low-level biamp (electronically or passively) is to remove the existing high-level XO from the 1.6QR. Both Paco and I did this long ago.
      - Re: Thanks, that's what I thought. (nt) CH Chang 16:16:40 02/05/01 (0)
        
        In Reply to: Re: 1.6 passive line xo works! posted by MikeCh on February 05, 2001 at 15:50:46:
        
        NT
  - Re: 1.6 passive line xo works! paco 18:29:15 02/04/01 (10)
    hi Davey!
    your circuit works very well so far (i already sent you an email with
    some comments), yet i noticed this:
    - the overall sound seems to me a little bit dark; this is nice
    to my ears, as any trace of the typical 1.6 brightness is gone,
    but i wonder if my cheap resistors & caps may be doing some harm
    to the higher highs
    - there is a small hum/buzz on the panels, especially on the
    tweeters, so they are no longer dead silent, as before; the buzz
    is not annoying with the music, and it doesn't depend upon
    the line xo, as it continues with the preamp turned off, but
    i wonder if it may be due to the fact that there isn't anything
    between the amps outputs and the drivers
    comments about your experience? thanks in advance!
    best, paco
    - Re: 1.6 passive line xo works! Davey 10:12:50 02/05/01 (0)
      I absolutely agree with Arbelos. Move the crossovers closer to the amps and not the preamp.
      Regards.
      Davey.
    - Re: 1.6 passive line xo works! Davey 18:53:44 02/04/01 (1)
      Listen for the hum/buzz with everything disconnected from your amplifiers inputs. If it goes away then you've most likely got some kind of wiring problem with your line level crossover. If the hum is still there then you're hearing low frequency noise from your power amp that was there all the time. (You don't have a series capacitor between the amp and your QR panel now to attenuate it.)
      WORDS OF CAUTION: Don't turn on/off your preamp or fiddle with any connections while the power amps are on. Give it a minute or so to make absolutely sure the power supply capacitors are discharged. Also keep in mind that any turn on/off transients from the power amps are now being felt directly by the QR panels. This is assuming your amps don't have some kind of mute during turn on/off. BE CAREFUL.
      Regards
      Davey.
      - Re: 1.6 passive line xo works! paco 06:13:33 02/05/01 (0)
        
        In Reply to: Re: 1.6 passive line xo works! posted by Davey on February 04, 2001 at 18:53:44:
        
        hi Davey,
        thanks again for your help!
        now it's noon and not very quiet, but i disconnected the
        tweeter amp inputs and it seems to me that the buzz is gone,
        yet i'll repeat the test tonight to make sure; in view of
        this so you think there may be a "wiring problem", but please
        what sort of problem do you have in mind?
        as for caution, i'll follow your directions, so i'll make
        changes, connections & the like only after turning my
        Donizetti's off (well, they have a "stand by" mode which
        disconnects the amps from the speakers--as for manual,
        so i think this should be preferable to make a true turning off?)
        did you notice the somewhat "dark" character of the music
        when using your passive line xo?
        best, paco
    - Re: 1.6 passive line xo works! Arbelos 18:51:11 02/04/01 (6)
      Hi Paco!
      The slight buzz comes from the bits of unscreened cable after the now higher impedance in the XO - tweeter amp connection. The attenuator increases impedance and stray fielfs are more easily induced, and before you had the low preamp output impedance soaking up any stray fields.
      A very slight attenuation comes from the 100 pF input capacitance of the amp, which forms a capacitive attenuator with the series 2.2nF capacitance, but the resistive divider plays a bigger role. You'll have to play a bit with the values. Therefore a pot isn't too bad an idea to fiddle first and then select one to three optimal divider values.
      Generally, very often an increase in resolution and reduction in distortion and grain makes the sound less bright, sometimes up to an irritating degree, in the first moment. If you eliminate diffraction you get a similar feeling: The definition isn't anymore where you expect it: In hyped harmonic or etched isolated 'details'. It is rather back there where it was first: In subtle shadings of timbre, natural and more expressive micro-dynamics and in a general feeling of 'breath', often accompanied by an extension in lower range soliidity and extension.
      - Re: 1.6 passive line xo works! paco 04:32:12 02/05/01 (5)
        
        In Reply to: Re: 1.6 passive line xo works! posted by Arbelos on February 04, 2001 at 18:51:11:
        
        hi Arbelos!
        your diagnosis of the problem seems plausible to me, especially because
        i decided to locate the small networks on the preamp side, so
        there are long runs of wire after them to the amps; do you think
        the problem might be softened if i take the reverse path and
        locate the networks on the amps side? or maybe i could separate
        the tweeter network from the woofer ones and locate the first
        on the amps side and the latter on the preamp side?
        adding a pot is beyond my skills at the moment, but you can suggest
        small changes to me, or even include some change in the networks
        with your welwyn resistors... that would be really great and i'd
        let you know what i hear in comparison
        your description of the audible effects of raising amps resolution
        is extremely interesting to me, as it seems to exactly coincide
        with what i'm hearing now; it's certainly irritating at times,
        as i've been playing just with the caps brands after the amps, but for the first
        time i can listen now to the pure amps, with nothing in between;
        now increasing the vol no longer increases the brightness!!!
        yesterday night i listened to Klemperer's EMI version of Beet's 3rd
        and the transients/dynamics of the first movement was almost
        real for the first time in my life, while the deep tension and
        emotion of the funeral march was absolutely thrilling; also,
        the low level detail in my dearest piano & guitar recordings
        have clearly increased, but in a NEW way, as i'm hearing not only more harmonics,
        but also they are related more correctly to each other in a
        much more convincing cohesive whole
        now my 1.6 continues to be extremely revealing speakers, but
        the kind of the whole "revelation" has deeply changed: it seems
        to me as if the sort of musical whole message belongs to another
        more natural & relaxed league
        best, paco
        
        Re: 1.6 passive line xo works! Arbelos 06:13:30 02/05/01 (4)
        
        In Reply to: Re: 1.6 passive line xo works! posted by paco on February 05, 2001 at 04:32:12:
        
        wherever you introduce a higher impedance, you should keep the higher impedance signal path as short as possible. Ie. you should preferably put both XOs close to the amp. The tweeter amp will be more susceptible because the mains harmonics will go unattenuated to the tweeter, whereaes the music signal is attenuated. So you you are reducing signal to noise ration in a major way, when you allow mains induced noises. BTW i don't like screening either, so really keep the high impedance connections very, very short, and you might get away with a simple non-metal box solution and unscreened cables, which is IMO the most easy and cheap way for excellent sound.
        Which mastering of the Klemperer Beethoven 3d do you have? This recording is one of my very few desert island recordings, and the funeral by Klemperer is so hair-raisingly beautiful! But EMI has IMO done mostly disastrous jobs on their remasterings (and a very mediocre one on many new recordings) The analogue recordings were very mediocre too. I have a japanese one which was quite good. I'd like to hear of a good new one on CD...
        Isn't the effect of the improved sonics similar to a better photo film emulsion: The gradations of the three coolour layers track much better, so the colours stay balanced and coherent over a much wider range of dynamics (maximal and minimal differenciable light intensities)?
        
        Re: 1.6 passive line xo works! paco 06:32:30 02/05/01 (3)
        
        In Reply to: Re: 1.6 passive line xo works! posted by Arbelos on February 05, 2001 at 06:13:30:
        
        thanks Arbelos!
        i'm very nervous, just home and all the time from the system
        to the computer, then back again, trying to understand what
        is going on with the buzz and with the very unusual kind of
        improvement which has took place after the line xo thing
        i'll reverse the connections on the line networks for them
        to be placed very close to the amps, then i'll post back, but
        in the meantime: is there any DANGER with my present setup?
        the buzz is not annoying, but i'd like to make sure it's not
        dangerous either!
        Klemperer's 3rd: recorded STEREO in 1959 with the Philarmonia Orq.,
        Abbey Road Studios; dig remast 1990 by EMI (CDM 7 63356 2);
        this is one my desert island recordings too, and i always use
        it to test everything: it's not the quality of the sound which
        matters here, but if the thing to be tested is able to convey
        the tension/emotion which i know there is on it!!
        best, paco
        
        Re: 1.6 passive line xo works! Arbelos 06:56:46 02/05/01 (2)
        
        In Reply to: Re: 1.6 passive line xo works! posted by paco on February 05, 2001 at 06:32:30:
        
        There's no danger IMO. It's just an annoying sound, which needs to be reduced.
        Power supply buzzes and internal noise is passed to the drivers also unattenuated, and this might increase with a higher impedance too, evewn if you put the XO close to the amp. Hope that's not the case. You'd need then a good buffer to eliminate it (again). This is one of the very few drawbacks of active or passive/active solutions.
        You said something about somebody from NZ telling you that this XO wan't work. What were the arguments?
        
        Re: 1.6 passive line xo works! pco 09:32:17 02/05/01 (1)
        
        In Reply to: Re: 1.6 passive line xo works! posted by Arbelos on February 05, 2001 at 06:56:46:
        
        OK, i'll deal with the new connections soon, but now i'm
        more relaxed by knowing there is no danger... :)
        Paoletti, the designer of the Donizetti's says these amps
        are very silent, with just some mechanical noise from the
        transformer, so he thinks the cause should be looked for
        somewhere else
        yes, the NZ guy says he did a simulation with Calsod (?) and
        according to his model the xover points are wrong; you can read
        the details of his arguments by opening the long attachment
        enclosed in my message; also, i sent a copy to Davey
        i've just tested for transients/dynamics: boy oh boy!! this may well be
        the department where more spectacular improvements can be found;
        for fast transients my favourite work in Walton symph 1, 2nd
        movement (Rattle good, Daniel even better, though a little forward),
        and for brutal dynamics Penderecki's Symph 3, 2nd mov (Witt);
        after listening to them i now see that the magnepan panels need
        much more control that the one which can be got through the coils;
        this is what Davey predicted and he was absolutely right!!!
        best, paco
        
        Re: 1.6 passive line xo works! Double Trouble 15:52:42 02/05/01 (0)
        
        In Reply to: Re: 1.6 passive line xo works! posted by pco on February 05, 2001 at 09:32:17:
        
        Calsod is a professional computer program for speaker modeling, crossover design, and crossover optimization. It has been around for years and is still one of the best on the market.
        Frank
- Re: 1.6 passive line xo works! paco 17:48:38 02/04/01 (0)
  > > How is that to be interpreted? The "ser" and "par" I'd assume mean series and parallel.
  that's right!
  > > To me, it looks like you're saying the 5.49k Ohm resistor is in series with the output from your pre-amp. There is a 4.53k Ohm res in parallel with that resistor. And a 2.2nF capacitor in series with the resistors.
  well, rather this: the 5.49k resistor and the 2.2nF cap in series,
  the 4.53k in parallel IN BETWEEN the former resistor and cap
  (in series with signal, in parallel from signal to ground)
  > > It seems like everyone has had positive experiences with passive bi-amping, that may be my next project after I replace the binding posts on my 1.6s. Thanks.
  yes, in biamping you get more from your 1.6, especially resolving
  power, then musicality
  best, paco
Re: 1.6 passive line xo works! MikeCh 15:05:40 02/04/01 (5)
Paco, am I correct in assuming that your Donizetti's has single-ended inputs? My configuration is balanced so I need a network on each leg.
- balanced XO Arbelos 07:03:35 02/05/01 (3)
  Mike, i don't think that you need the set twice, you'll only need the serial parts twice, the parallel ones can go from + to - direct. But it has to be re-scaled (i'd say half the parallel cap values, and double the parallel R values, parts *very* closely matched).
  - Re: balanced XO MikeCh 12:14:20 02/05/01 (2)
    Thanks Arbelos!
    - have you read... Arbelos 10:42:32 02/06/01 (1)
      http://www.audioasylum.com/forums/mug/messages/11052.html ?
      as to your hybrid passive /active bi-amping experiences.
      - Re: have you read... MikeCh 10:56:12 02/06/01 (0)
        
        In Reply to: have you read... posted by Arbelos on February 06, 2001 at 10:42:32:
        
        Yes . Thank you!
- Re: 1.6 passive line xo works! paco 16:31:44 02/04/01 (0)
  yes, i'm working single-ended (fortunately!); you can always
  start by using an adapter, then add more networks later on
  make sure about the input impedance of your amps and be
  ready to raise the vol of your preamp quite a lot after
  inserting the line xo
  i've listened a few hours today and still don't understand how
  $3 in cheap line components can overcome the more than $200
  of my coils & caps after my amps; more precise info tomorrow
  best, paco
forgot to mention... paco 09:56:14 02/04/01 (0)
the above networks are OK just for amps with 39k input impedance;
you should adapt them otherwise
best, paco

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