driver configuration, tweeter always at the top..

Discussion in 'Home Cinema Speakers' started by bohane, Feb 2, 2009.

  1. bohane

    bohane
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    following on from the 'placing speakers on there side' thread where me and chris_av took the thread of topic discussing the advanages/reasons for all/most driver configurations being the same, ie tweeters at the top and drivers below.

    so what are peoples thoughts on this subject? we already have agreed that tweeters are more 'directional' than woofers, and also the fact that if woofers were at the top then balance/stabilty would be an plausable reason. and then there s the case of fashion, all speakers seem to be of this design nowadays, although it has been mentioned that mission have made speakers in the past with woofers at the top and they were very good speakers too.

    so is it just fashionable to have the tweeter at the top? or is it actualy to do with the sound dispersion or another clever reason that i am failing to discover.....

    oppinions apreciated:smashin:

    andy

    just realised tthat the q acoustics 1050i have a woofer-tweeter-woofer arangement, can anybody tell me the benefits of this please???
     
    Last edited: Feb 2, 2009
  2. markiii

    markiii
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    ideally you want the tweeter at ear height

    therefore I would say it depends on the height of the speaker
     
  3. shadesbass

    shadesbass
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    As markiii says, tweeters should be at approximately the same height as your ears when in your listening position. This is because tweeters generally have a narrower dispersion pattern than mid/bass drivers (although this varies depending on the type of tweeter: dome, ribbon, piezo horn etc.) so are more sensitive to vertical displacement relative to your ears.
    A 'normal' height bookshelf speaker + stand roughly puts the tweeter at ear-height when sat down. An inverted driver arrangement would mean that the stand would need to be higher, resulting in a two-fold increase in instability (higher stand and top-heavy speaker).

    There's nothing to stop you mounting your speakers upside-down if it means the tweeters are better placed (this is what I do in my office as my speakers are located on a shelf above my monitor), although as you've already mentioned, stability could be an issue, especially with trapezoidal cabinets.

    Centre speakers quite often have tweeters in the centre with mid/bass drivers either side. This is so that the horizontal alignment is as close to centre as possible.
     
  4. bohane

    bohane
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    thanks for the reply, and basicaly sums up what my thoughts on the matter were :)

    cheers

    andy
     
  5. BlueWizard

    BlueWizard
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    Actually, if you go to DIY speaker building sites, you will discover many configuration of speaker. Though as others have pointed out, you still want the tweeters roughly ear height, which I think is about 40 inches.

    In discussing and designating speaker configurations, we typically use a series of abreviations, and in MTM which stands for Midbass, Tweeter, Midbass. If there is a 'W' in the sequence, then likely 'M' stands for Midrange rather than Mid bass. If I have a speaker with Midbass and Midrange, I will usually designate Midbass as '(Mb)' and Midrange as 'M'.

    So, 'W' for woofer, 'M' for Midbass or Midrange, depending on the context, and 'T' for tweeter.

    The MTM is an extremely popular design for Home Cinema, and is a design conceived by DR. D'Appolito. The MTM design, when designed right, can control dispersion and lobing.

    Other expand in this design for stereo by adding some combination of woofers, as in WMTM, WWMTM, WMTMW, WWWWMTM, WWMTMWW and in cases not using MTM, we see WMT, WWMT, WMTW, etc.... In this last case, likely the 'M' is for Midrange, in the earlier examples, it is for Midbass.

    So, yes, almost any combination is reasonable.

    Consider this design WMTMW from Proac -

    ProAc - perfectly natural

    So, while there is some logic to speaker placement on the front baffle, there is also a lot of flexibility.

    In some cases, you see the woofer very low in the cabinet, while the MT, or MTM are up higher. This is because the woofer, or bass, gets a boundary boost from being close to the floor.

    If you study Do-It-Yourself speaker design, you begin to realize that it is an immensely complex process.

    Steve/bluewizard
     
  6. bohane

    bohane
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    thanks for the informative (as always) reply steve, much apreciated :smashin: so the general idea is that the tweeter neds to be level with the listeners ear height, and all/most configurations are based around this principle.

    thanks

    andy
     
  7. ChrisAV

    ChrisAV
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    Hi Steve - thanks for this. Am I right in assuming boundry boost from the floor is the same effect as created when moving speakers closer to walls/corners (i.e. re-inforcing the bass)?

    Cheers

    Chris
     
  8. stainless-steel

    stainless-steel
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    The crossover is also used to direct the radiation axes and combined wavefront of the two drivers.
    It depends on the characteristics and interaction of the drivers and crossover. Some manufacturers simply invert the driver array (Mission?) to tilt the radiation axis, or you can tilt the baffle back (Wilson), or you can use driver choice and crossover tailoring (nearly everyone else).
    Tweeters at ear level is a good rule of thumb but it doesn't tell the whole story.

    If you're interested in speaker design there's a wealth of informative publications out there, I bought Martin Colloms "High Performance Loudspeakers” a few years back, it's pretty maths heavy but there's also lots of useful and revealing information for the layman.

    You'll be surprised (or maybe not ;)) just how much speaker design relies on Maths and Engineering rather than the Divine Inspiration that's suggested by a lot of the audiophile prose you read in the mags.
     
  9. Grayman

    Grayman
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    A lot of manufacturers seem to favour having the tweeter in the middle, looking at Missions blurb they recon it is beneficial because:

    "Symmetrical driver array
    A symmetrical configuration of drivers is used to improve dispersion and to improve imaging, Placed equidistant above and below the high-frequency driver, mid-range and bass drivers create an even horizontal dispersion and a controlled dispersion on the vertical plane.

    Having the treble unit centrally placed enhances the imaging by mimicking a point-source dispersion. Interference patterns when a stereo pair of speakers are used create an almost holographic sense of presence with the listener able to discern the exact location of instruments and voices within the soundstage."

    I wont pretend I know exactly what they mean, but might help identify the reason for the config choice.
     

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