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Thread: Cross over frequency question?

  1. #1
    Gary L

    Cross over frequency question?

    I am finding a great deal of opinion in the crossover selection for my model 19 clone project and want to toss this out for some understanding.
    In my two way system I will have 811 horns with 802-8G drivers and 416-8A LFs.

    I guess it is purely personal at what point in frequency I cross over. Some say 500Hz others say 800Hz while still others say go for the original 1200Hz of the 19s. I have also been told crossing at a higher 1500Hz will also work fine.

    Altec N-8500s are selectable @ 500 & 800 Hz. and redily available.
    Altec N-1201s are 1200Hz. original and not so available and expensive for 25 year old electronics.
    The new N-1500s are available and cross at 1500Hz.

    I guess my question is what makes a cross over cross at a particular frequency and is this able to be changed.
    The 8500s can switch between 500 and 800 so can a 1201 or 1500 be made to go higher or lower and what determines the frequency cross point.

    I have no idea yet what frequency I might like best for my speakers and wonder if trying them all would be my best option to get this important factor correct. In the build process I can leave the crossover hole uncut until I decide which to use but I sure am baffled by all the information and opinions and would like to hear some discussion about the choices available to us.

    I am also not an electronics technician but if a simple soldering of a resistor or cap will change the values of the frequency then I am sure I could do this. I don't expect it to be this simple but need to know.

  2. #2

    Horn and Driver Limitations…

    … dictate c/o Frequency and Slope


    The horn should provide uniform loading at least one octave below the lowest c/o frequency used. This loading is determined by the mouth area, length, and flair (cut-off) frequency of the horn. Typically, the larger the horn, the lower the cut-off frequency.

    Due to the close proximity of the phase plug to the diaphragm, compression drivers become increasingly displacement (output) limited as frequency and/or attenuation slope of the crossover is lowered. For constant output, displacement increases inversely with the square of frequency (f^-2).

    The 811 is designed for use with 12 dB/Oct crossover with a –3db frequency no lower than 800 Hz.

    If a 500 Hz. c/o frequency is never the less required, use the Altec 511 or equivalent horn and/or an electronic c/o with a 24 dB/Oct. slope where the c/o frequency set at –6dB.

    If the venue requires high output or top quality voice, then a three-way system is preferred. Here, the 200-2000 Hz. 'speech' decade is covered by a separate driver (and even bigger horn).



  3. #3
    Gary L
    WHG, You said a mouthful above and I think there are some answers there but I could'nt hear them.
    I think I understand that I should not go below 800Hz with the 811B horns. I would agree with this.
    The 19s cross at 1200Hz. and sound fine to me there.
    What happens to the sound if I c/o at 1500Hz. ?
    Since I have a very nice set of new N1500-8A C/Os I would like to use, need I do anything to them to get the speakers to sound good? Can I do anything? Should I do anything? should I not use them and just find a pair of N1201-8As?
    I am going to use the 811B horns with 802-8G drivers and the 416-8A woofers in my speakers so this is not in question.
    The C/O network to use and at what point they C/O is.
    I do appreciate your time and effort and please forgive my lack of the technical understanding.

  4. #4
    Alex Lancaster



    Use the 1500Hz xovers and tell Us what You think.

  5. #5



    By all means try the N1500-A8 c/o’s you have.
    1) They will afford additional protection to the 802-8G drivers.
    2) The 416-8A woofers will be some what challenged by the higher frequencies passed to them. Listen to them with the tweeters disconnected to determine the extent of irregular response. When woofers are operated at higher frequencies, acoustical treatment of enclosure interior becomes critical and may require tweaking to suppress additional standing waves.

    If you want to experiment and tweak system performance, then bi-amplification and an electronic crossover will provide the prerequisite flexibility needed to adjust both crossover frequency and slope.



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