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Thread: 604E not equal volume

  1. #1
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    604E not equal volume

    I have a pair of 604E that were built the same year but in the cabinet one has significantly lower volume that the next. I do not detect any voice coil rubbing on the lower volume speaker. I am wondering if the low volume speaker needs to be recharged. Is there any way to discern if an alnico needs to be recharged? Currently I am using a pot between the preamp and amp to reduce the gain on the higher volume speaker.

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    First thing I would do is make sure that the cones ( are original & ) have the same printed number on them ( 21184-2 is original ).

    That's the number to look for ( the assumption when you see those numbers is that the voice-coils are also identical and original ):



    - If you see 2 different numbers on your cones then you will possibly need to recone one or both at GPA ( to obtain a matched pair ).

    One can ( with the woofer section of the crossover unhooked ) measure the DCR ( ie; dc Resistance ) of each voice-coil > looking for a close match of +/- 0.5 ohm .


    A weak magnetic system will manifest itself in the Qes value of the woofers Ts parameters > the Qes value of matched woofers should be near identical ( if the woofers both have the same cone numbers & voice-coils ) .

    The most straightforward approach to measuring a speaker's Ts parameters is to buy something like a WooferTester gizmo such as DATS 2 from P.E. or WT2 from S&L.




  3. #3
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    Both speakers have the same cone. One speaker measure DCR woofer 11.5 and 8.8 and the other is 13 and 9 ohms. The louder one is 13 and 9.

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    Have you tried swapping the crossovers from one cabinet to the other ?


  5. #5
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    Yes I have tried swapping crossovers.

    Below are the Fs of the speaker. The Fs of the 27.1 is the louder the other less volume.
    Name:  Resonance Frequency in Free Air.jpg
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  6. #6
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    Quote Originally Posted by 280SL View Post
    Both speakers have the same cone. One speaker measure DCR woofer 11.5 and 8.8 and the other is 13 and 9 ohms. The louder one is 13 and 9.
    What were the cone numbers that you found on your 604E's ? ( over the decades, there were a few possible replacement cone numbers ).

    An upward shift in Fs can be caused by the surround Goop drying up ( though typically raising the Fs a few hz won't change overall output levels ).

    A lower than expected DCR can sometimes be caused by a partially shorted voice-coil ( the woofer will continue to work, but at a reduced level ).


  7. #7
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    Since you are obviously handy with a signal generator, sense-resistor & DVM, I would recommend that you download REW to perform some more extensive parameter testing ( click the pic ).



    Additionally, the most up-to-date Beta Versions are available at AVNirvana ( REW Forum ).

    REW will ( among other things ) allow you to setup a jig to measure your woofer's AC impedances ( as well as obtain Ts Parameters ).

    From the looks of your above pic, your woofers have different voice-coils ( you'll need actual AC impedance traces to either verify or debunk that opinion ) .


  8. #8
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    The cone numbers are the same. They are in a cabinet so I don't have immediate access to them. One of the speakers was bought new by my father and I know the cone is original. That speaker has the higher volume.

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