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Mounting Drivers front vs back side of baffle?

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  • Shawn_K
    started a topic Mounting Drivers front vs back side of baffle?

    Mounting Drivers front vs back side of baffle?

    I'm wondering in there are any acoustic advantages mounting a driver on the back side of the baffle vs the front side; I can only think of one. I have seen drivers mounted on the back side on production and DIY speakers.

    Acoustic Advantages
    1. Thickness of the baffle doesn't restrict the air flow on the inside.

    Acoustic Disadvantage
    1. Places the acoustic center point of the driver farther behind the front baffle surface. This can make the time alignment with the tweeter worse.

    Non-Acoustic Advantages
    1. Hide an ugly driver frame behind the baffle.
    2. Lower cost stamped steel frames are hidden.
    3. Aluminum frames don't need to be painted; probably more common on production speakers.
    4. Lower cost clear zinc plated screw can be used to mount the driver since they will be out of sight.
    5. Looser tolerances for the mounting hole locations are possible with slightly oversized holes in the driver and the use of washer head type screws.

    Non-Acoustic Disadvantages
    1. Baffle or Back panel of enclosure needs to be a separate piece so that the driver can be mounted on the inside.

    Shawn

  • Pete Schumacher
    replied
    Seems that the driver basket was acting like a bell when the flange was rigidly mounted. Perhaps a saddle for the magnet would do the trick and help dampen the ringing.

    Then again, maybe all they did was confirm that decoupling works well for stamped frame shortcomings.

    Leave a comment:


  • replied
    Originally posted by badman View Post
    http://www.linkwitzlab.com/Driver%20Decoupling.doc

    Linkwitz indicates that a decoupled magnet system is actually better behaved as a ground reference for driver motion. Incidentally, KEF, NAIM, and others have all utilized decoupled drivers in various models, what the commercial utilization indicates (gimmick or legit) is another issue, but Linkwitz is generally a pretty respectable source for this kind of thing.
    ​Interesting article, the conclusion surely seems to indicate that decoupling definitely has merit. Thank you for the link.

    Leave a comment:


  • badman
    replied
    http://www.linkwitzlab.com/Driver%20Decoupling.doc

    Linkwitz indicates that a decoupled magnet system is actually better behaved as a ground reference for driver motion. Incidentally, KEF, NAIM, and others have all utilized decoupled drivers in various models, what the commercial utilization indicates (gimmick or legit) is another issue, but Linkwitz is generally a pretty respectable source for this kind of thing.

    Leave a comment:


  • Pete Schumacher
    replied
    Originally posted by Chris Roemer View Post
    The way I see it, IF you COULD mount a driver (a woofer, let's say) that was completely decoupled from the box (baffle), then when the V.C. got energized, there'd have to be SOME kind of distortion introduced - 'cause the V.C./cone would be moving somewhat, but the driver frame would also end up moving SOME (one of Newton's Laws of Motion - no?). The cone would not be moving the "designed" amount of air molecules, would it? Now, I DO believe that decoupling a tweeter could be beneficial, provided that the woofer was making the tweeter's mounting vibrate (which SEEMs like it could introduce some kind of H.D. or I.M. distortion).
    Exactly right. The ideal baffle would be one of infinite mass. Decoupling defeats the purpose. What you want is a baffle that doesn't vibrate and offers high inertia.

    Leave a comment:


  • Chris Roemer
    replied
    The way I see it, IF you COULD mount a driver (a woofer, let's say) that was completely decoupled from the box (baffle), then when the V.C. got energized, there'd have to be SOME kind of distortion introduced - 'cause the V.C./cone would be moving somewhat, but the driver frame would also end up moving SOME (one of Newton's Laws of Motion - no?). The cone would not be moving the "designed" amount of air molecules, would it? Now, I DO believe that decoupling a tweeter could be beneficial, provided that the woofer was making the tweeter's mounting vibrate (which SEEMs like it could introduce some kind of H.D. or I.M. distortion).

    Leave a comment:


  • PWR RYD
    replied

    ​Many years ago in an issue of Speaker Builder Magazine, they described a flush mounted decoupled driver mounting technique using RTV Silicone. Basically you cut an oversized hole in the baffle maybe an eighth of an inch in diameter larger than the driver. Then you mask the hole (masking tape or whatever) and place the front baffle flat on its face. Then you set the driver inside the opening also flush with the front of the baffle and then fill in the gap with RTV Silicone. If you do it carefully, you have a very neat flush and decoupled driver. The driver doesn't make direct contact with the baffle, but is held in place by the Silicone.
    Why do YOU give a darn?

    Leave a comment:


  • replied
    Originally posted by badman View Post
    behind baffle also makes decoupled mounting easier.
    ​Many years ago in an issue of Speaker Builder Magazine, they described a flush mounted decoupled driver mounting technique using RTV Silicone. Basically you cut an oversized hole in the baffle maybe an eighth of an inch in diameter larger than the driver. Then you mask the hole (masking tape or whatever) and place the front baffle flat on its face. Then you set the driver inside the opening also flush with the front of the baffle and then fill in the gap with RTV Silicone. If you do it carefully, you have a very neat flush and decoupled driver. The driver doesn't make direct contact with the baffle, but is held in place by the Silicone.

    Leave a comment:


  • badman
    replied
    behind baffle also makes decoupled mounting easier.

    Leave a comment:


  • replied
    Originally posted by Shawn_K View Post
    Thanks for all the input! I don't see much advantage to mounting the woofer on the back side of the baffle and will stick with front mounting. I was reading a review for the Sonus Faber Venere 1.5 speaker which has the woofer mounted on the back side of the baffle; technically the driver is mounted on the front side, but the frame is covered with a facade that sets the woofer back from the front surface, This speaker has a waveguide on the tweeter and effectively sets the tweeter back behind the baffle front surface. Sonus Faber sells stands for these speakers that tilt the speakers back about 5 degrees. The test reviewer determined that at the crossover point 2kHz they summed better when the speaker was tilted back 5 degrees. So I guess if you don't use the optional stand you have to put spikes on the front or block underneath or put them on a higher bookshelf to get the 5 degree tilt back. If they would have surface mounted the woofer they wouldn't have need to be tilted back 5 degrees. I think this is a case where someone thought aesthetics were more important. I'm not saying that I dislike the look of speakers that are tilted backwards slightly but it doesn't make sense with a bookshelf speaker like this. My $.02.
    ​Tilting also helps a bit with tweeters that are too bright directly on axis. At least so in my experience.

    Leave a comment:


  • Shawn_K
    replied
    Thanks for all the input! I don't see much advantage to mounting the woofer on the back side of the baffle and will stick with front mounting. I was reading a review for the Sonus Faber Venere 1.5 speaker which has the woofer mounted on the back side of the baffle; technically the driver is mounted on the front side, but the frame is covered with a facade that sets the woofer back from the front surface, This speaker has a waveguide on the tweeter and effectively sets the tweeter back behind the baffle front surface. Sonus Faber sells stands for these speakers that tilt the speakers back about 5 degrees. The test reviewer determined that at the crossover point 2kHz they summed better when the speaker was tilted back 5 degrees. So I guess if you don't use the optional stand you have to put spikes on the front or block underneath or put them on a higher bookshelf to get the 5 degree tilt back. If they would have surface mounted the woofer they wouldn't have need to be tilted back 5 degrees. I think this is a case where someone thought aesthetics were more important. I'm not saying that I dislike the look of speakers that are tilted backwards slightly but it doesn't make sense with a bookshelf speaker like this. My $.02.

    Leave a comment:


  • replied

    That's nice to know.

    The reason you chamfer the baffle when mounting on the front is because the basket and motor structure can completely block the rear air flow. When mounting to the back of the baffle, air flow out the front isn't a problem since there's no motor structure in the way.

    Apparently, that's not obvious to everyone.
    Blah, blah, blah.

    Leave a comment:


  • Pete Schumacher
    replied

    Well, I don't give a darn whether you mount your drivers from the front or back of the baffle.
    That's nice to know.

    The reason you chamfer the baffle when mounting on the front is because the basket and motor structure can completely block the rear air flow. When mounting to the back of the baffle, air flow out the front isn't a problem since there's no motor structure in the way.

    Apparently, that's not obvious to everyone.

    Leave a comment:


  • replied

    That only matters for very small drivers. An 8" woofer, mounted on the back of a 1" baffle wouldn't see any appreciable diffraction anomalies over its typical operating band.
    Well, I don't give a darn whether you mount your drivers from the front or back of the baffle.

    Leave a comment:


  • Pete Schumacher
    replied
    Baffle thickness affects open frame drivers regardless whether the driver is front (from the outside) or rear (from the inside) mounted, that is why we chamfer or round over the offending edge, be it the inside or the outside.
    That only matters for very small drivers. An 8" woofer, mounted on the back of a 1" baffle wouldn't see any appreciable diffraction anomalies over its typical operating band.

    Leave a comment:

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