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Thread: ebay recone kit, 2234/2235, aquaplas, cone weight

  1. #31
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    MmD

    Quote Originally Posted by Earl K View Post
    Ian,Thanks for demonstrating your complete understanding of the terms "MMS, MMD & Air-Load".( Now to put it to use ), it would be helpful if you could puzzle-out why ( or offer-up a plausible theory ) why LHF member "patallen" has an OEM 2225H cone kit ( removed intact ) that weighs in at 105grams ( when best guess is that the 2225's MMD should be around 90 grams ).Here's a pic of his 2225 cone assembly:This "outlier" in measured weight is causing quite a bit of confusion ( from what I see ).
    If You remove and weight the whole recone kit intact You are in fact weighting full weight of the surround and spider. Only fraction of their weight should be taken in the calculation, because one edge of the surround and one edge of the spider are not moving.For the surround, we can assume that only halve of the weight contributes to the MMD. while for the spider it can be less than 1/2 because of the greater difference between inner and outer diameter.Therefore recone kit always weights more than MMD.

  2. #32
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    Quote Originally Posted by Earl K View Post
    Ian,

    Thanks for demonstrating your complete understanding of the terms "MMS, MMD & Air-Load".

    ( Now to put it to use ), it would be helpful if you could puzzle-out why ( or offer-up a plausible theory ) why LHF member "patallen" has an OEM 2225H cone kit ( removed intact ) that weighs in at 105grams ( when best guess is that the 2225's MMD should be around 90 grams ).

    Here's a pic of his 2225 cone assembly:



    This "outlier" in measured weight is causing quite a bit of confusion ( from what I see ).

    Sorry l completely missed this as l deleted the subscription to all threads to re purpose my time on other things . I have been away for a month or so and crushed my finger in an accident. So l am not mad keen on typing right now.

    This stuff will do anyoneís head in. It depends on the actual data and if that data is accurate. Unfortunately those JBL tables canít be relied on 100%. Itís easy to get the entire thing mixed upÖ and completely fucked up.

    The way around solving for missing data is to use driver T/L software modeller. Some of the bass reflex software programs have a T/L modeller. You put in the main parameters and then what if determine the other parameters. They are all inter related.

    Looking at the JBL parameter sheet the 2225 MMS is 105 grams. Allowing about 15 grams for the air load the MMD would be in the vicinity of 90 grams. The problem with weighing the driver total assembly for comparison is that not all the mass of the spider or the surround is included for modelling the TL parameters.

    Mms is commonly used in loudspeaker modelling software. It is Mmd plus the Ďair loadí but JBL normally only state the MMS which includes the air load for modelling purposes.

    Use 15 grams for a 15 inch woofer as an approximation.

    The actual total MMD weighed on scales is not useful for extrapolating the FS with a simulator because not all the MMD is moving mass. This is because some of the suspension is attached to the basket. If you wanted to sacrifice a cone kit cut half the spider and half the surround off and then re weigh the cone assembly.

    The mass ring has to be accounted for. Itís all a pita. I donít like the mass rings. They limit the peak x max because the mass ring slaps on the pole piece. It also ruins the mid range due to the added mass on the apex of the motor.

    Accounting for all that if your FS is higher than it should be it could be the spider.

    But l would put it in a known ported enclosure like 5 Cu ft and tune it with a simulator and then measure that actual FB? If the tuning is out more than 10% then you know your driver is not working as it should.

    I would then measure it with the DATS3 to check the main TL parameters. I recall there are a few different ways of getting the VAS.

    I would need to sit down and go over the entire thread with a coffee to make any further comment. But the mystery 15 gram could be the air load if your taking JBLís MMS for the MMD cone mass. As l said it can be rather confusing.

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