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Thread: A7 Model 19 help....please

  1. #1
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    A7 Model 19 help....please

    Hi all,
    I am very new to the Altec world and despite a lot of online research remain confused......I have the following 'bits' : 902-8A, 811B, 416-8C & A7 enclosures, I do not have a crossover. I think what i have is Model 19 drivers and an A7 enclosure, is this correct?

    Money is unfortunately tight for me so I will not be buying any other driver/enclosure bits. Also due to financial constraints i am (obviously) rather nervous of blowing a driver. i intend building a crossover myself and would prefer a passive crossover (safer) but active will be quicker to whip up initially, so my questions are:

    1. What crossover frequency?
    2. What slopes?
    3. Which Altech passive crossovers (if any) can i use?
    4. If anyone has some schematics for suitable passive networks could you please pass on or point me at them?
    5. I have seen many crossover schematics but they look rather complicated obviously some additional EQing is going on what corrections are these relevant to my 'bits' of course?

    If i am posting on the wrong forum i do apologise. Any assistance will be greatly appreciated.

  2. #2
    Dang. Amateur speakerdave's Avatar
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    How could it be that an active crossover would be "quicker to whip up initially"?

    To use an active crossover would require a total of four channels of amplification. Is there some confusion about terminology?

    To build any crossover you will need to buy parts. Do you have any sense what that would cost?

    Using those 811 horns your crossover frequency should be no lower than 800Hz.

    I think you should hunt down a pair of Altec 801-8A crossovers for now.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Quote Originally Posted by speakerdave View Post
    How could it be that an active crossover would be "quicker to whip up initially"?

    To use an active crossover would require a total of four channels of amplification. Is there some confusion about terminology?

    To build any crossover you will need to buy parts. Do you have any sense what that would cost?

    Using those 811 horns your crossover frequency should be no lower than 800Hz.

    I think you should hunt down a pair of Altec 801-8A crossovers for now.
    I guess I meant active would be quicker than passive....i have a bucket-load of op amps, polyprop caps and resistors etc hunting down the right value inductors bothers me more (our postal system is a bit buggered right now so rather dubious of delivery times from overseas).

    I see on another post 1200Hz is recommended for the 811B and 902A.....

  4. #4
    Dang. Amateur speakerdave's Avatar
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    You can design and build all the necessary power supply and circuitry?

    You have the necessary amplifiers?
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Yeah i build tube amps for a hobby, never done speakers though. I am just confused re: the crossover as i asked in my questions. The drivers are all Great Plains Audio and almost brand new but the damn tings have been gathering dust for over 2 years and am tired of walking past them.....just want to be sure that i am getting the right components. I see the N1201-8A is correct for the Model 19 but will that sound/work well in the A7 enclosure?

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    Dang. Amateur speakerdave's Avatar
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    Is your question about the behavior of the A7 horn up to that frequency? I don't know the answer to that. Have you tried asking the denizens of the Altec user group board?
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Dang. Amateur speakerdave's Avatar
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    I hope my questions have not been insulting--I just can't tell from your posts what your background in these areas consists of. IN CASE you decide it might be a good idea to do some review about speaker systems and crossovers and all, the Rane Company has a library on their website which is a reliable source of information: http://www.rane.com/library.html

    If you decide to use an active-high level-electronic-crossover you can protect your compression driver diaphragms with a protection capacitor. There is a page in one of the JBL electronic crossover guides which can be used to decide what value to use. JBL 5235 Manual Section 3-3 Table 2. You can find that with Google.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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    Thank you I appreciate your assistance. I have seen some altec crossover designs but no-one says what kind of crossovers they are e,g 2nd order, 3rd order, Butterworth, Linkwitz-Riley etc. Also as mentioned there seems to be some extra EQing going in in the designs i have seen. I simulated the Model 19 crossover and it appears to use a 3rd high pass but a 2nd order low pass plus i have Model 19 drivers in an A7 enclosure.....hence my confusion. Was just hoping one of the gurus would advise me.....no doubt i shall eventually get to the bottom of it - one always does and learn something along the way!

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    Dang. Amateur speakerdave's Avatar
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    I think the gurus are all at lunch.
    "Audio is filled with dangerous amateurs." --- Tim de Paravicini

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