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Thread: Altec 902-16HF driver on a 511B horn

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    Altec 902-16HF driver on a 511B horn

    i bought a old A7 from a decease estate the owner no longer . The 511B horn driven by a 902-16HF driver. crossover box at 500hz (N500g) bass driver is 416a.
    When i remove the back cover of the 902-16HF, i notice there is 2 capacitors(10uf & 6uf = 16uf) soldered in parallel and connected in series to the positive leads.
    Should i remove both capacitors and replace it with a straight through wire? As its already crossover at the crossover box at 500hz why the reason for the capacitors at the positive leads again ? the high pass is done at the crossover box why have another high pass capacitors on the driver positive leads again? If anyone have any idea , greatly appreciated. Can i remove those caps

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    Administrator Mr. Widget's Avatar
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    The 16 ohms in series is approximately a 600Hz first order crossover. Not sure why someone would add it to the system.


    Widget

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    Quote Originally Posted by Mr. Widget View Post
    The 16 ohms in series is approximately a 600Hz first order crossover. Not sure why someone would add it to the system.


    Widget
    Thanks, i found the altec spec the 16uF capacitors is just a protection caps, i have remove them so far so good.

    So far i am please with the sound , but feel the horns can sometime sound a little forward in the female voice on some recordings. i would like to slightly tone down just by -2db attenuation.
    Can i connect 2 resistors in L-pad on the horns (one in series to + leads and the other in parallel across the + & - leads)? The horns is 16ohm , i would like to apply a -2db attenuation. What values of the 2 resistors must i get?

    Hope u can advise?

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    Senior Member spkrman57's Avatar
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    902/511

    500 hz is pushing horn driver to extremes. You would be better off with 800 hz crossover! 511 horn loading to 500 hz already rolling off rapidly.
    Just my opinion.
    Regards, Ron
    JBL Pro for home use!

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    Senior Member RMC's Avatar
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    seetlee,

    Well the protection capacitor frequency was higher than crossover frequency! This is very curious. Normally that cap freq is one octave BELOW crossover freq as indicated by JBL. You should have a protection cap properly executed as this is a safety precaution for the driver.

    As for your L-Pad, 2 db down for a 16 ohm driver is: R1 (series) 3.29 ohm and R2 (parallel) 61.8 ohm, this is from Drew Daniels table who is a very precise man.

    Pretty much the same numbers from Eargle's Handbook of Sound System Design L-Pad table: R1 3.3 ohm and R2 62 ohm.

    Hope this helps you.

    Richard
    POWERED BY: QSC, Ashly, Tascam, Rolls Mosfet, NAD, and Crest Audio

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    Thanks for all the insightful great advise, on another note has anyone had experiment with removing the loading cap (the black hard shell plastic screwed onto the diaphragm) to improve the sound?

    i read that for domestic home setting without playing at insane level its perfectly safe to remove the loading cap but wanted to know what improvement will it make on the overall sound quality?

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    Member macsic's Avatar
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    Quote Originally Posted by seetlee View Post
    Thanks for all the insightful great advise, on another note has anyone had experiment with removing the loading cap (the black hard shell plastic screwed onto the diaphragm) to improve the sound?

    i read that for domestic home setting without playing at insane level its perfectly safe to remove the loading cap but wanted to know what improvement will it make on the overall sound quality?

    If you remove the plastic cap you should put felt at the bottom of the lid, I have already replaced that with an 808 to make it an 802 by changing the diaphragm but difficult to say if it is the felt or the change of the diaphragm that improved the sound.
    Music is emotion.

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    i have gone completely naked, remove the back lid & the loading cap.
    i can say confidently, the difference is night and day. Will stay naked no going back.
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  9. #9
    Member macsic's Avatar
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    Quote Originally Posted by seetlee View Post
    i have gone completely naked, remove the back lid & the loading cap.
    i can say confidently, the difference is night and day. Will stay naked no going back.
    Good, it's not a Pascalite diaphragm.
    I did this, not complicated.

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    Music is emotion.

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