What is behind the dome in dome tweeters?

organ
organ Posts: 4,969
edited April 2013 in 2 Channel Audio
I've never taken one apart but was just wondering what exactly is behind the dome in dome tweeters?
Post edited by organ on
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  • F1nut
    F1nut Posts: 50,546
    edited April 2013
    Air.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • tonyb
    tonyb Posts: 32,962
    edited April 2013
    I ask women in strip clubs that question all the time.

    OOPS....missed a "w".:lol:
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  • Face
    Face Posts: 14,340
    edited April 2013
    Magnet, or in better tweeters a chamber designed to help with resonances with some foam or polyfill.

    http://www.speakerdesign.net/scan_speak/tweeters/6600/6600_tweeter.html

    035a88e72a.jpg


    http://www.wavecor.com/TW030WA05-to-08_cross_section.png

    http://www.wavecor.com/TW030WA05to08_exploded.png
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • FTGV
    FTGV Posts: 3,649
    edited April 2013
    Depends on the tweeter.Some it will be just the top of the pole piece,some will have damping material glued to the pole piece to reduce reflections back into the dome.Dome tweets with extra rear chambers have vented pole pieces to allow the back wave passage into the chamber where it will be atleast in part absorbed by damping material.


    Edit.looks like Face beat me to it.
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  • lightman1
    lightman1 Posts: 10,788
    edited April 2013
    Dark sorcery......
    Beware should you peer behind!
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  • drumminman
    drumminman Posts: 3,396
    edited April 2013
    Smallies wrote: »
    getting a Mr T for that one Face

    Would you mind, every once in a while, posting something that makes sense, and that contributes to the discussion?
    "Science is suppose to explain observations not dismiss them as impossible" - Norm on AA; 2.3TL's w/sonicaps/mills/jantzen inductors, Gimpod's boards, Lg Solen SDA inductors, RD-0198's, MW's dynamatted, Armaflex speaker gaskets, H-nuts, brass spikes, Cardas CCGR BP's, upgraded IC Cable, Black Hole Damping Sheet strips, interior of cabinets sealed with Loctite Power Grab, AI-1 interface with 1000VA A-L transformer
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  • pitdogg2
    pitdogg2 Posts: 25,441
    edited April 2013
    FTGV wrote: »
    Depends on the tweeter.Some it will be just the top of the pole piece,some will have damping material glued to the pole piece to reduce reflections back into the dome.Dome tweets with extra rear chambers have vented pole pieces to allow the back wave passage into the chamber where it will be at least in part absorbed by damping material.

    As Fred alludes to "damping material" on Polk's tweeters they have a felt piece glued to the pole piece.
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  • skrol
    skrol Posts: 3,375
    edited April 2013
    JBL titanium domes have foam... that usually degrades over time and gets gummy.
    Stan

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  • zingo
    zingo Posts: 11,258
    edited April 2013
    ring-radiator-tweeter-diagram.jpg
    Jake
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  • Face
    Face Posts: 14,340
    edited April 2013
    Here's the cutaway of a high end compression driver.

    M9NHv9D.jpg
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • mhardy6647
    mhardy6647 Posts: 33,801
    edited April 2013
    Nice look at the phase plug, but one cannot really see the diaphragm, much less what's behind it.

    Here's another cutaway view of

    Note that a compression driver isn't really all that different than a direct radiating dome driver; the diaphram is dome-shaped and operates the same way - but it is loaded differently (coupled to the air in th eroom via a horn or waveguide serving as an acoustic tranformer, instead of directly coupling to the air in the room).

    page1.jpg
    http://www.lansingheritage.org/images/altec/specs/components/802d-804a/page1.jpg

    In most cases (but not all) the dome is "inverted" relative to its use in a typical dome tweeter. Then again, there have, over the years, been several inverted-dome direct-radiator tweeters. The best known is probably still the Burhoe (EPI/Epicure/Genesis/Burhoe) "airspring" tweeter - a nice-sounding little driver.


    EPIsprings.jpg
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  • Face
    Face Posts: 14,340
    edited April 2013
    There's not a whole lot behind it.

    mbuK3rT.jpg
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • organ
    organ Posts: 4,969
    edited April 2013
    Thanks a lot guys! Face, those pics really help, I appreciate it.
    Even though the diaphragms are small, it's amazing how fast they need to move back in forth.
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  • FTGV
    FTGV Posts: 3,649
    edited April 2013
    mhardy6647 wrote: »
    Then again, there have, over the years, been several inverted-dome direct-radiator tweeters. The best known is probably still the Burhoe (EPI/Epicure/Genesis/Burhoe) "airspring" tweeter - a nice-sounding little driver.


    EPIsprings.jpg
    Back in the day Burhoes and EPI's were my first exposure to real "hi fi"speakers.Those tweets definately have a homemade look to them.I would argue that Focal are the best known manufacturer of inverted domes.They have been building them since the 80's using various dome materials through the years.Some were less than pleasant sounding however, especially the early fibreglass domes that exhibited a a nasty break up mode in the 15-17khz region IIRC.Rumour has it given the years of development the newer generations are much more refined sounding but still not everyones cup of tea.
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  • mhardy6647
    mhardy6647 Posts: 33,801
    edited April 2013
    Tangband had an inverted dome for a while - there was a German (?) mfgr. with one as well. I don't recall the Focal inverted domes (or maybe I do and I am thinking they were someone else's!). The Burhoe inverted domes are pretty well behaved from an aural perspective (although I have no idea how well they measure).

    Speaking of tweeters, this site is always a fun read - and given this thread's topic, might be of great interest to the OP :-)
    http://www.zaphaudio.com/ specifically: http://www.zaphaudio.com/nondomes/ and http://www.zaphaudio.com/tweetermishmash/
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  • FTGV
    FTGV Posts: 3,649
    edited April 2013
    mhardy6647 wrote: »
    I don't recall the Focal inverted domes (or maybe I do and I am thinking they were someone else's!).
    They of course use them in their own speakers but also were main stays in Wilson Audio's speakers for a couple of decades.I believe they have now moved on to soft domes possibly sourced from Scan Speak.
    Speaking of tweeters, this site is always a fun read - and given this thread's topic, might be of great interest to the OP :-)
    http://www.zaphaudio.com/ specifically: http://www.zaphaudio.com/nondomes/ and http://www.zaphaudio.com/tweetermishmash/
    Zaph's site is a great resource unfortunately he does'nt update it much anymore.I even built a pair of his ZA5's that are currently serving desk top duties.The little budget Vifa neo metal dome tweet he chose for the design is quite good considering it's low cost.(purchased before the price of neodymium sky rocketed) .http://www.zaphaudio.com/ZA5/
    z1.JPG 249.6K
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  • organ
    organ Posts: 4,969
    edited April 2013
    Wow! Great work on the build. I bet they sound fantastic.
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  • theshawn
    theshawn Posts: 70
    edited April 2013
    When I opened up a Vifa within some older Def Tech DR7 bookshelfs I saw this, consistency was hard so I wondered if this is why they sounded harsher than I anticipated? Anyway....

    20130101_181912.jpg
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  • organ
    organ Posts: 4,969
    edited April 2013
    theshawn wrote: »
    When I opened up a Vifa within some older Def Tech DR7 bookshelfs I saw this, consistency was hard so I wondered if this is why they sounded harsher than I anticipated? Anyway....

    20130101_181912.jpg

    Makes sense. When it's hard, it's reflecting the energy back and forth instead of absorbing it. It's just foam right? I wonder what caused it to harden up. Maybe a reaction with the glue they used?
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  • theshawn
    theshawn Posts: 70
    edited April 2013
    organ wrote: »
    Makes sense. When it's hard, it's reflecting the energy back and forth instead of absorbing it. It's just foam right? I wonder what caused it to harden up. Maybe a reaction with the glue they used?


    That's what I thought too, if it was meant to absorb sound then as hard as it was it wasn't absorbing much if anything. I bought them at the Salvation Army though and they looked like they'd been in someones garage for years but still cleaned up well. I have the DR7 Towers too, I wonder if removing this blob and replacing it with something else would improve those because they get bright/harsh under higher volume too and were bought at the same time.

    I don't know if it started out as foam or not because it's definitely not foam now. lol
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  • theshawn
    theshawn Posts: 70
    edited April 2013
    Well I emailed Def Tech about it and Chet said the substance was a bit on the harder side so I guess that shoots my theory. lol
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  • jumpindick
    jumpindick Posts: 428
    edited April 2013
    wow you guys are great. I always enjoy reading on this forum. Thank you for some quality education. I have been here for more than a year now and since the time I joined, I certainly have learned a lot. Thanks to all of you who share good info.
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  • organ
    organ Posts: 4,969
    edited April 2013
    theshawn wrote: »
    Well I emailed Def Tech about it and Chet said the substance was a bit on the harder side so I guess that shoots my theory. lol

    lol. Maybe the speakers are on the brighter side of neutral. I find that increasing the distance from the listening position can really help with brighter speakers.
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  • theshawn
    theshawn Posts: 70
    edited April 2013
    organ wrote: »
    lol. Maybe the speakers are on the brighter side of neutral. I find that increasing the distance from the listening position can really help with brighter speakers.


    Yeah playing with the spacing and distance helped some but they were just too fatiguing so I recently purchased some Martin Logan Motion 12 that are wonderful compared to the DR7. They were definitely on the brighter side of neutral for my tastes.
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  • Goldenboy72206
    Goldenboy72206 Posts: 126
    edited April 2013
    I want some martin logan motion
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  • Face
    Face Posts: 14,340
    edited April 2013
    Many things can make a speaker sound bright or harsh, the damping behind a dome is probably the least likely culprit.
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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  • EndersShadow
    EndersShadow Posts: 17,590
    edited April 2013
    Goldenboy72206 wrote: »
    I want some martin logan motion

    Hurry up and get those remaining posts so you can stop thread crapping everyone to access the Flea Market!
    "....not everything that can be counted counts, and not everything that counts can be counted." William Bruce Cameron, Informal Sociology: A Casual Introduction to Sociological Thinking (1963)
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  • organ
    organ Posts: 4,969
    edited April 2013
    theshawn wrote: »
    Yeah playing with the spacing and distance helped some but they were just too fatiguing so I recently purchased some Martin Logan Motion 12 that are wonderful compared to the DR7. They were definitely on the brighter side of neutral for my tastes.

    Then I guess there is no need to worry about the DR7 anymore. The ML's are on a different level. Congrats.

    Face,
    Makes sense. I know I've heard a few people say Def Tech are on the brighter side. I've never heard them however.
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  • Face
    Face Posts: 14,340
    edited April 2013
    http://www.speakerdesign.net/scan_speak/tweeters/7100/7100_tweeter.html
    "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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