Rolls SX45 stereo two-way active xover.

Discussion in 'Equipment Reviews & Opinions' started by BigElCat, Jul 19, 2017.

  1. BigElCat

    BigElCat AK Subscriber Subscriber

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    I know exactly what you're saying...but I can't find any active HPF or active LPF.

    Do you know a source for these ?
     
  2. whoaru99

    whoaru99 Epic Member

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    I think pretty much any DSP-based crossover, and a 3-way active with enough range of the low pass and high pass to allow them to overlap without even using the mid output.

    (As in the example posted in #18).
     
    Last edited: Nov 6, 2017
  3. BigElCat

    BigElCat AK Subscriber Subscriber

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    You mean a DSP or a 3-way active ? Would I need both ?

    I had the same idea of using a 3-way. So far I haven't found one with a low pass that goes high enough.

    My original crossover point is 500hz for the woofers. I think I should stay at 500 hz.

    I could crossover the mid/tweets at any point below 500 hz.

    I'll re-read #18.
     
  4. BigElCat

    BigElCat AK Subscriber Subscriber

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    This is exactly what I want, however, when I use the bi-amp switch and dual sets of binding posts on my ADS, the woofers are said to not be affected by the passive crossover any more.

    Question at a tangent...does this mean the electrolytic caps on the passive crossover are by-passed ?

    I would have to set the low pass filter to 500 hz, with a 12 db slope to mimic the original crossover, would i not ? And then the high pass at 250 hz.
     
  5. whoaru99

    whoaru99 Epic Member

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    I didn't see a schematic for the speaker crossover so can't say if the biamp switch simply separates the LF from mid/high connection, or if there is that plus bypass of any low pass elements in the woofer circuit.

    I see that you tried running horizontal(?) biamp with the mid/high full range and the crossover on low. That, for some reason, triggered protection.

    Do you have a multimeter to check if the black posts are common with and without the switch in biamp mode?

    Would you try using the crossover like you did before (crossover LPF for low, mid/high full range) but with vertical biamp arrangement? I know you want both speakers working, but this would be sorta a proof of concept thing.
     
  6. Powertech

    Powertech Active Member

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    I run a fully active 3 way system. There are no passive crossovers in the speaker cabinets.
    Trying to overlay a passive crossover with an active one kind of defeats the object of the exercise.
    Where active systems really shine is that the amplifier outputs are in direct contact with the speaker coils - no inductors or capacitors in between) although there are some systems that use a 2 way active system for bass to mid and then passive for mid to treble. This direct connection has a number of benefits. 1) Each amplifier is only operating over part of the audio band which gives them more headroom.
    2) Amplifier damping factor (driver control) is actually working (driver back emf is not damped by the crossover coils, especially the bass circuits).
    3) The filter settings remain the same regardless of volume (voicecoil heating at higher volumes affect passive crossover frequencies).
    4) Active filters have easily variable settings for setup purposes.
    5) Heavy loading (or clipping) of bass amps have no effect on the rest of the sound (not necessarily true with vertical amping where 2 amp channels share a single power supply, but is true with horizontal amping where bass and mid is from separate amplifiers).

    The main disadvantage is system complexity.
    1) The mass of wiring behind the amp rack can be horrendous, you really need to know what you are doing to wire this lot up.
    2) You really should use an audio analysis system to set this lot up properly.
    3) There is an overbearing temptation to keep tweaking it - trust me, there is!

    I have to say though, that I cannot see myself going back to a passive system as a well set up active system is incredibly dynamic.
     
  7. BigElCat

    BigElCat AK Subscriber Subscriber

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    Sorry I didn't see this before now.

    I will check the common posts (with the bi-amp switch in each position). It will be a few days though.

    I sold the Rolls SX-45 to another AK member, so I can't do anymore experiments with it.

    I'm reluctant to do anymore electronic experimenting, because I blew an output transistor in my Sansui B-2101. I was trying to set the bias.
     
  8. Harryconover

    Harryconover Well-Known Member

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    Progress causes pain , don’t give up , I am late to this I was going to recommend using two of the same Crown amp one for each side also get a good 24 db peroctive crossoaer TDM made a nice stereo single rack space tipe the results will be amazing headroom , my favorite thing in hifi
     

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