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Thread: Going Back in Time

  1. #21
    Join Date: Nov 2013

    Location: Yorkshire

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    I'm Andr'e.

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    Yep thats why i threw mine in the scrap pan


  2. #22
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,144
    I'm Hugo.

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    Quote Originally Posted by walpurgis View Post
    Imagine the tweeter emitting high pressure water and you'd get an idea (not exact).
    That's is so incorrect - not even close to what happens! A decently designed dome tweeter actually emits an even hemispherical wave when fed a pulse but actually that's not unrepresentative of what happens with a music signal. Tweeter output does become more directional as the frequency rises, though.

    NPL have posted a short video showing part of the research findings, but the technique goes much further than this in terms of resolution:

    Last edited by Ammonite Acoustics; 26-10-2014 at 15:04. Reason: Clarification and added comments re directivity

  3. #23
    Join Date: Aug 2009

    Location: Staffordshire, England

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    I'm Martin.

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    So more like a lawn sprinkler then?
    Martin



    Current Lash Up:

    Technics SL1200 with Sumiko h/s & Nagaoka MP50 * Firebottle valve MM phono stage * Parasound CDPi1000 * NVA P90SA passive pre / Krell KSA50S Power amp * JM Lab Electra 926 loudspeakers *



    "I hate to advocate drugs, alcohol, violence, or insanity to anyone, but they've always worked for me." - Hunter S Thompson

  4. #24
    Join Date: Jan 2009

    Location: Norwich

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    I'm Hugo.

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    Quote Originally Posted by hermit View Post
    Edit - I recently restored a pair of AR94s that had a square of felt about 7-10mm thick around the tweeter (see pic). What thickness would you recommend? Also should the ring be quite tight to the each tweeter dome or should I try to frame both tweeter and supertweeter within a triangularish felt box a bit like the AR94s?
    Around 7mm thick is ideal, I reckon. I have some old Russ Andrews Focus Rings ( see http://www.russandrews.com/product.a...ULFJOFCYNGOWZN ) that work very well and which are quite fairly priced. The ring should not be tight to the dome - do that and you end up absorbing too much of the peripheral tweeter output. And, yes you do need to treat the tweeter and supertweeter separately.

  5. #25
    Join Date: Jan 2008

    Location: Forest of Dean, Glos & Cambrian mountains, Wales

    Posts: 8,410
    I'm Jerry.

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    Quote Originally Posted by hermit View Post
    Edit - I recently restored a pair of AR94s that had a square of felt about 7-10mm thick around the tweeter (see pic). What thickness would you recommend? Also should the ring be quite tight to the each tweeter dome or should I try to frame both tweeter and supertweeter within a triangularish felt box a bit like the AR94s?
    Careful with the materials you use - some (softer) felt can affect the perceived frequency response quite drastically, rolling it off - ime, coarse fibre felt is the best.

    There was a US guy on here - diffraction begone - or similar who ran a company that had it sussed very nicely. .... Jim Goulding, that was it! http://www.stereomojo.com/Diffractio...GONEREVIEW.htm
    Jerry

    Main systems:
    Spotify Premium streaming, DAC3 NOS TDA1543. Philips Black Tulip 270 pre / Black Cat mono power amps. Speakers: MBL 116F. Atratus3 i/c & Western Electric 16GA spkr cables. ProJect and Nordost Magus power cables

    Headphones: AKG 551, JBL Synchros S700, B&O H6, PSB M4U-1, B&O Form 2 & 2a and Sony XBA-H1 & SoundMagic E50 IEM headphones

    2nd system: Spotify Premium streaming, Audiolab MDAC, Philips 370 power amp, Chario Syntar 100T speakers. Headphones: Beyerdynamic DT-150, SoundMagic E10 IEM headphones

    3rd system: Portable CD player, Kinter MA-180 T amp, Klegg Symphony 102 speakers

  6. #26
    Join Date: Jan 2008

    Location: Forest of Dean, Glos & Cambrian mountains, Wales

    Posts: 8,410
    I'm Jerry.

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    Quote Originally Posted by Ammonite Acoustics View Post
    Around 7mm thick is ideal, I reckon. I have some old Russ Andrews Focus Rings ( see http://www.russandrews.com/product.a...ULFJOFCYNGOWZN ) that work very well and which are quite fairly priced. The ring should not be tight to the dome - do that and you end up absorbing too much of the peripheral tweeter output. And, yes you do need to treat the tweeter and supertweeter separately.
    Argh, no, awful things! - sounded like someone had thrown a blanket over my speakers!
    Jerry

    Main systems:
    Spotify Premium streaming, DAC3 NOS TDA1543. Philips Black Tulip 270 pre / Black Cat mono power amps. Speakers: MBL 116F. Atratus3 i/c & Western Electric 16GA spkr cables. ProJect and Nordost Magus power cables

    Headphones: AKG 551, JBL Synchros S700, B&O H6, PSB M4U-1, B&O Form 2 & 2a and Sony XBA-H1 & SoundMagic E50 IEM headphones

    2nd system: Spotify Premium streaming, Audiolab MDAC, Philips 370 power amp, Chario Syntar 100T speakers. Headphones: Beyerdynamic DT-150, SoundMagic E10 IEM headphones

    3rd system: Portable CD player, Kinter MA-180 T amp, Klegg Symphony 102 speakers

  7. #27
    Join Date: Jan 2009

    Location: Norwich

    Posts: 2,144
    I'm Hugo.

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    Horses for courses, I suppose. I have a set currently doing transformative work on some old Videoton Minimax 2 speakers which have the same sort of recessed front baffle as the IMFs.

  8. #28
    Join Date: Jan 2008

    Location: Forest of Dean, Glos & Cambrian mountains, Wales

    Posts: 8,410
    I'm Jerry.

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    Interesting. Are they tonally neutral on the Minimax or smoothing a bright treble?
    Jerry

    Main systems:
    Spotify Premium streaming, DAC3 NOS TDA1543. Philips Black Tulip 270 pre / Black Cat mono power amps. Speakers: MBL 116F. Atratus3 i/c & Western Electric 16GA spkr cables. ProJect and Nordost Magus power cables

    Headphones: AKG 551, JBL Synchros S700, B&O H6, PSB M4U-1, B&O Form 2 & 2a and Sony XBA-H1 & SoundMagic E50 IEM headphones

    2nd system: Spotify Premium streaming, Audiolab MDAC, Philips 370 power amp, Chario Syntar 100T speakers. Headphones: Beyerdynamic DT-150, SoundMagic E10 IEM headphones

    3rd system: Portable CD player, Kinter MA-180 T amp, Klegg Symphony 102 speakers

  9. #29
    Join Date: Oct 2011

    Location: Glasgow

    Posts: 689
    I'm Paul.

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    Quote Originally Posted by Ammonite Acoustics View Post
    Around 7mm thick is ideal, I reckon. I have some old Russ Andrews Focus Rings ( see http://www.russandrews.com/product.a...ULFJOFCYNGOWZN ) that work very well and which are quite fairly priced. The ring should not be tight to the dome - do that and you end up absorbing too much of the peripheral tweeter output. And, yes you do need to treat the tweeter and supertweeter separately.
    The fact that the ring should not be tight to the dome means that I couldn't treat the supertweeter as the inner edge of the wooden grill frame is only about 10mm from the top edge of the supertweeter. I suspect that at my age I cannot hear the supertweeter anyway so I will try a pair of the Russ Andrew's Focus Rings around the tweeter only.

    Might it be worthwhile idea to get some thin 1 or 2mm felt and line the inner top edge of the grill frame above the supertweeter?

    Quote Originally Posted by jandl100 View Post
    Argh, no, awful things! - sounded like someone had thrown a blanket over my speakers!
    Maybe worth a try anyway. At £12 it's a cheap experiment. I found this info tucked away on the Focus Ring page on the Russ Andrew's site which tries to alleviate your concerns:

    "With speakers placed close to hard reflective surfaces you may hear a reduction in high frequency energy, due to a reduction in early sidewall reflection. At first you may feel that the sound has become 'dulled'. Don't panic! Once you become accustomed to the change, you will hear a noticeable improvement in clarity, depth of image and soundstage focus. The degree of improvement will vary depending on the design and quality of the tweeter."

    Quote Originally Posted by jandl100 View Post
    Careful with the materials you use - some (softer) felt can affect the perceived frequency response quite drastically, rolling it off - ime, coarse fibre felt is the best.

    There was a US guy on here - diffraction begone - or similar who ran a company that had it sussed very nicely. .... Jim Goulding, that was it! http://www.stereomojo.com/Diffractio...GONEREVIEW.htm
    Looks interesting but diffractionbegone.com is down or no longer exists. Also whilst looking into this I read somewhere that his product was designed specifically for flat baffle speakers.

  10. #30
    Join Date: Jan 2008

    Location: Forest of Dean, Glos & Cambrian mountains, Wales

    Posts: 8,410
    I'm Jerry.

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    Quote Originally Posted by hermit View Post
    ..... At first you may feel that the sound has become 'dulled'. Don't panic! .....
    Trust your ears! - it really has.

    But as you say, Paul, it's only £12 in the great scheme of things, worth a go.
    Jerry

    Main systems:
    Spotify Premium streaming, DAC3 NOS TDA1543. Philips Black Tulip 270 pre / Black Cat mono power amps. Speakers: MBL 116F. Atratus3 i/c & Western Electric 16GA spkr cables. ProJect and Nordost Magus power cables

    Headphones: AKG 551, JBL Synchros S700, B&O H6, PSB M4U-1, B&O Form 2 & 2a and Sony XBA-H1 & SoundMagic E50 IEM headphones

    2nd system: Spotify Premium streaming, Audiolab MDAC, Philips 370 power amp, Chario Syntar 100T speakers. Headphones: Beyerdynamic DT-150, SoundMagic E10 IEM headphones

    3rd system: Portable CD player, Kinter MA-180 T amp, Klegg Symphony 102 speakers

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