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Thread: Dispersion Foam Used Around Royd Minstrel Tweeters?

  1. #11
    Join Date: Feb 2013

    Location: W Lothian

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    I'm Grant.

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    I read once it should be open then medium then closed foam. Dunno if there is anything In it
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  2. #12
    Join Date: Jun 2015

    Location: London/Durham

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    I'm Lawrence.

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    Thanks makes sense but I expected closed cell foam to absorb the treble and open cell foam to let it pass through (like some speaker grilles that are made of it do). I've seen tweeters covered in foam (eg. Proac I think).

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  3. #13
    Join Date: Apr 2011

    Location: cheltenham

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    I'm matt.

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    Quote Originally Posted by Lawrence001 View Post
    Thanks makes sense but I expected closed cell foam to absorb the treble and open cell foam to let it pass through (like some speaker grilles that are made of it do). I've seen tweeters covered in foam (eg. Proac I think).

    Sent from my BLN-L21 using Tapatalk
    Acoustic foam is a much more dense open-cell-foam than the stuff used for speaker grills.

  4. #14
    Join Date: Apr 2011

    Location: cheltenham

    Posts: 561
    I'm matt.

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    Quote Originally Posted by struth View Post
    I read once it should be open then medium then closed foam. Dunno if there is anything In it
    yes, that's what I always imagined would work best. Very open on the outside and getting more and more dense as you get further in.

  5. #15
    Join Date: Apr 2017

    Location: Cheshire UK

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    I'm Martin.

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    So what are the physics of it then in Peter and Jane terms?

    The sound radiates out from the tweeter at all angles so what is that foam supposed to do...focus it.... tame it...break it up from travelling along the cabinet? I cant see it making a significant difference.

    I see Wharfedale (well wang tung industries) recessing the tweeter now so it looks like a mini driver...is that the same aim?

    Ive just done a computer test with 16k on the screen equalizer and I can hear any change between min or max levels. I can hear the effects of the 8k slider .........probably puts my treble hearing into perspective regarding speakers.

    Dont get me wrong...I never said Minstrels were anywhere near the last word in sound. The top end can be unruly and they tend towards a tonal brightness...still put a smile on when bouncing along with fine material and a good amp...I just wanted to hear the quirky looking things. I swap speakers out regularly..... SL6... celestion 3s, Conistons and any 80s or 90s speaker I get my hands on.....I must get up to date with speakers

  6. #16
    Join Date: Jun 2015

    Location: London/Durham

    Posts: 3,166
    I'm Lawrence.

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    Quote Originally Posted by Minstrel SE View Post
    So what are the physics of it then in Peter and Jane terms?

    The sound radiates out from the tweeter at all angles so what is that foam supposed to do...focus it.... tame it...break it up from travelling along the cabinet? I cant see it making a significant difference.

    I see Wharfedale (well wang tung industries) recessing the tweeter now so it looks like a mini driver...is that the same aim?

    Ive just done a computer test with 16k on the screen equalizer and I can hear any change between min or max levels. I can hear the effects of the 8k slider .........probably puts my treble hearing into perspective regarding speakers.

    Dont get me wrong...I never said Minstrels were anywhere near the last word in sound. The top end can be unruly and they tend towards a tonal brightness...still put a smile on when bouncing along with fine material and a good amp...I just wanted to hear the quirky looking things. I swap speakers out regularly..... SL6... celestion 3s, Conistons and any 80s or 90s speaker I get my hands on.....I must get up to date with speakers
    I think most recessed tweeters are essentially gently horn loading them to increase efficiency. I don't know the effect on the signal along the edge but I imagine if diffracts a bit at the edge of the horn and again on the cabinet edge (but weaker having already diffracted once on the way). Does anyone technically minded have any computer models to run it through?

    Sent from my BLN-L21 using Tapatalk

  7. #17
    Join Date: Jan 2009

    Location: Sheffield - UK

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    I'm Mark.

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    The problem is that whenever the tweeter radiation strikes an edge it is diffracted again and can, in effect, act like a secondary echo - this is an issue with high frequencies because their wavelength is so much shorter than bass frequencies. This is the reason you sometimes see tweeters offset to one side of the baffle - this doesn't reduce the diffraction effects of the cabinet edges but it does mean that the two edges do not radiate at the same time and so their impact is minimised. The foam has two (or it can do, depending on the implementation) purposes - it can absorb some of the energy passing over the face of the cabinet and it can randomise that diffraction which does take place. Having said all that, the foam that surrounds the Minstrel tweeter is too thin to do a great deal (I think someone said this earlier in the thread)

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