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Monitor Audio Monitor 9

Discussion in 'audio' started by matthew, Feb 12, 2020.

  1. matthew

    matthew Member

    Hi, new member here - I have a pair of Monitor Audio Monitor 9s and wondered if anyone knew the cap value in the crossover? (I see one cap with no value printed on it). Taking a guess would 3.3uf be far off?

    Any help appreciated.
  2. Craig B

    Craig B Re:trophile

    Some of the earlier MA models with 1" metal domes were crossed over second order at circa 4.2KHz, with the bass/mid first order. This may have as much to do with the chosen bass/mid driver HF roll-off characteristics; as the Seas sourced tweeters had their power rating specified in relation to IEC 268-5, via high pass Butterworth at 2500Hz, 12dB/octave.

    8Ohm tweeter, 4.2KHz to Butterworth 2nd-order, then 3.35µF is indicated.
    6Ohm tweeter (likely if it is an OEM Seas 1" unit), 4.2KHz to Butterworth 2nd-order, then 4.46µF is indicated (4.7µF is common).

    Some of the lower end paper cone bass/mid models were crossed over lower, circa 2.9 to 3KHz (likely due in part to poorer bass/mid HF rolloff characteristics):
    8Ohm tweeter, 2.9KHz to Butterworth 2nd-order, them 4.85µF (3KHz/4.7µF is common)
    6Ohm tweeter, 2.9KHz to Butterworth, then 6.47µF

    Have you 1 x cap, 1 x resistor, and 2 x inductors?

    P.S. I've a picture of an R352 crossover here with 1 x Bennic 4µF, 50V cap in series with the tweeter, 1 x resistor, and 2 x inductors. Assuming a 6Ohm tweeter, that is circa 4500 to 4700Hz high pass at 12db/oct, assuming a 0.29 mH inductor across.
    Last edited: Feb 12, 2020
  3. matthew

    matthew Member

    Craig, thank you, interesting. The R352 crossover seems very similar.

    I actually took a flyer and removed the two caps from under the extraordinary quantity of glue and, Lo, on their backsides was printed '3.3µF', everything else looked ok and fresh so I swapped the caps out for a pair of 3.3 polypropylenes that I had lying about, reassembled, and ... they sound fantastic! Things just don't normally work out like that for me; I think probably this was something like an issue with really aged Bennics (as in Craig's R352s) or somesuch. Anyway, they sound happier.
    Craig B likes this.

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