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Why would someone do this? Crossover modification...

Discussion in 'Infinity Loudspeakers' started by Ross6860, Oct 15, 2018.

  1. Ross6860

    Ross6860 AK Subscriber Subscriber

    Messages:
    1,661
    Location:
    Ohio
    Infinity RS-IIIa

    Several owners ago, they built these crossovers.

    RSIIIa1.jpg

    Any idea what they were trying to achieve? I would think Infinity put at least some cursory investigation into the crossover when they built the speaker.

    Also looks like they removed the zeners protecting the tweeter.
    RSIIIa2.jpg

    It will cost me a bit, but I'm thinking of rebuilding them with the factory specs.

    I could pass them on since I have a pair of RS-II that could also use some refreshing, and there's only so much room for floor-standers.
     

     

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  2. Brunt

    Brunt New Member

    Messages:
    45
    Location:
    San Diego
    Having heard both a fully restored pair of IIIbs and a pair of original condition RSIIs (read: in need of significant restoration), I vote the RSIIs all day. The IIIbs are nice speakers, but the dipole and odd bass crossover of the RSII put it on another level if you have the space.
     
  3. jazzmans

    jazzmans Super Member

    Messages:
    2,312
    Location:
    devils playground, NV
    as an owner of rs 4b and rs IIb, what brunt said. they are completely different sounding speakers. the rs4b aren't bad at all, but not nearly on the same level as the II a/b.

    I'd sell them with full disclosure of the crossover modifications, or try to find a rs 3/4 crossover from a pair that have been parted out?
    but no question, I'd keep the rs II
     
  4. audiotemp

    audiotemp Well-Known Member

    Messages:
    583
    That factory drawing won't give you a working crossover. The tweeter circuit, as drawn, is wrong.
     
  5. Tedrick

    Tedrick Infinity-phile Subscriber

    Messages:
    7,027
    Location:
    Gainesville, FL
    I have to concur with @jazzmans and @Brunt. Since I got IIb's, my IIIb's have been completely sidelined.
     
  6. Ross6860

    Ross6860 AK Subscriber Subscriber

    Messages:
    1,661
    Location:
    Ohio
    Would you care to elaborate? Should the cap be between the fuse and inductor?


    Just to clarify, my speakers are RS-II, not RS-IIa/b. Still very happy with them and they aren't going anywhere. If a pair of IIa/b, 2.5 or 4.5 come along, well maybe that would change.

    So far no one has conjectured what the mods were supposed to "improve".
     

     

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  7. elnaldo

    elnaldo Addicted Member

    Messages:
    7,346
    Location:
    Buenos Aires GMT-3
    I'd compare the crossovers with picts from the web. It's possible the drawing is OK and the Spec sheet is wrong. Anyway they are not too different (just another capacitor in the woofer, a bit different crossover slope, and the 1ohm resistor on the tweeter, filtering a bit the freqs going to the inductor, so smoothing the slope just a bit)

    The specs sheet says "2-way speaker", "tweeterS", and "woofer" (singular), so seems plenty of errors (and the inductor-capacitor mistake too).

    I'd search images of the crossover board, and check if that 1 ohm resistor exists in the original, if it has 2 capacitors in the woofer section, and if it has the zeners, or just the fuse. (inductors are the same , 5 on each crossover)

    Here is a pict of what seems to be stock crossovers: https://us.v-cdn.net/5021930/uploads/attachments/8/2/6/2/4/60359.jpg (no affiliation)
     
  8. audiotemp

    audiotemp Well-Known Member

    Messages:
    583
    Hey, I thought I had responded to this...sorry.
    Yes, as drawn the inductor just provides a load but does no filtering. It's possible there are other errors as well. I'd look for confirmation elsewhere before assuming the factory drawing will give you something better than what you have.
     
    BrianLW likes this.

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