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Thread: Lowering Peerless 830669 30Hz resonance

  1. #1
    Join Date: Jul 2017

    Location: Pinecrest, FL, USA

    Posts: 192
    I'm Horacio.

    Default Lowering Peerless 830669 30Hz resonance

    I have just purchased four Peerless 830669. Will painting the cone and foam surround with a suitable substance such as the glue used in fitting the gasket, diluted, lower the resonance frequency and help protect the surround?

    Cheers,
    Last edited by F575M; 20-08-2017 at 15:40.

  2. #2
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

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    Self defeating to an extent. Painting 'Plastiflex' type materials on cones will add mass and potentially lower resonance, but painting the same on surrounds will make those slghtly stiffer and raise resonance.

    I use Allene's Original Tacky Glue for doping. It gives a slightly tacky to touch finish similar that on KEF bextrene cones and Tannoy 'Tannoplas' foam cone surrounds.

    Diluting it for use on paper cones is not a good idea in my view. That causes it to soak in rather than provide a coating.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  3. #3
    Join Date: Apr 2011

    Location: cheltenham

    Posts: 746
    I'm matt.

    Default

    The surround should be rubber, so no need to protect it.

    To lower fs, I'd add weight to the cone. I'd most likely sit the driver flat on It's magnet and pour some neoprene glue around the outside of the dustcap.

    Why do you want to lower fs?

    Edit:
    Just remembered that there Is an online calculator somewhere. Just put the T/S parameters In and your desired weight and It will show you the changes.

  4. #4
    Join Date: Jul 2017

    Location: Pinecrest, FL, USA

    Posts: 192
    I'm Horacio.

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    According to Gradient's driver replacement recommendations for the Gradient SW-63 subwoofer, the 830669 has a resonant frequency (30 Hz) that intrudes into the audio band that I will be using [QUAD ESL-63].

    Diaphragm Mass Inc. Airload (Mms)74.11g
    Maximum Linear Excursion (Xmax)8.3 mm
    Surface Area of Cone (Sd)522.8 cm²
    Qts 0.54 Fs 31 Hz

  5. #5
    Join Date: Apr 2011

    Location: cheltenham

    Posts: 746
    I'm matt.

    Default

    Quote Originally Posted by F575M View Post
    According to Gradient's driver replacement recommendations for the Gradient SW-63 subwoofer, the 830669 has a resonant frequency (30 Hz) that intrudes into the audio band that I will be using [QUAD ESL-63].

    Diaphragm Mass Inc. Airload (Mms)74.11g
    Maximum Linear Excursion (Xmax)8.3 mm
    Surface Area of Cone (Sd)522.8 cm²
    Qts 0.54 Fs 31 Hz
    Not sure why an fs of 30hz would "Intrude into the audio band". It has a 9db peak around 2k but that shouldn't be a problem.

    For open baffle use 'Qts' is the figure to look at. In a sealed box, you'd look at that figure combined with the frequency response and try to design a box with a flat response. With open baffle, It Isn't any different. For a flat response with that driver a 'Q' of 0.8 to 0.85 looks nice to me.

    If you add 90 grams to the cone, you'll get a 'Q' of 0.8, and an fs of 20.8hz but spl will go from 86.8db (1w/1m) to 79.89db.

    Added mass calculator - LINK

  6. #6
    Join Date: Jul 2017

    Location: Pinecrest, FL, USA

    Posts: 192
    I'm Horacio.

    Default

    Thank you so much for the mass calculator link.

    Cheers,

    Horacio

  7. #7
    Join Date: Jul 2017

    Location: Pinecrest, FL, USA

    Posts: 192
    I'm Horacio.

    Default

    Is this the glue you that used for doping, does it glide easily?

    Cheers,

    Horacio

  8. #8
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

    Default

    No. The clear tacky glue is useless for speakers (handy for other things though).

    This is the correct one:



    It paints on easily.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

  9. #9
    Join Date: Jul 2017

    Location: Pinecrest, FL, USA

    Posts: 192
    I'm Horacio.

    Default

    Thanks, just one coat is enough?

  10. #10
    Join Date: Apr 2012

    Location: N E Kent

    Posts: 51,624
    I'm Geoff.

    Default

    Maybe. Or maybe two.

    I use one coat on Tannoy surrounds and have been known to need two on paper cones if they are a bit absorbant like Goodmans felted paper. It's not something I'd do normally though. Better to select a driver that meets requirements to start with really.

    By the way. This glue is good for restoring KEF bextrene cone doping that has started lifting off.
    It is impossible for anything digital to sound analogue, because it isn't analogue!

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