Announcement

Collapse
No announcement yet.

At what frequency does bass become directional??

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • At what frequency does bass become directional??

    You see all of these subwoofers with the drivers facing different directions; downfiring, twin woofers side-mounted in the enclosures, etc. When does the bass become directional and require the driver to face you?

    While on this subject, is there a rule for distance from the floor for a downfiring subwoofer?
    My "No-Name" CC Speaker
    Kerry's "Silverbacks"
    Ben's Synchaeta's for Mom
    The Archers
    Rick's "db" Desktop CBT Arrays
    The Gandalf's

  • #2
    Re: At what frequency does bass become directional??

    Originally posted by Kevin K. View Post
    ... When does the bass become directional and require the driver to face you? .
    There is a bit of confusion in regards to 2 areas:
    One: The limitation of human hearing and perception and localization ability at low frequency.
    Two: It is more of a case of how big does something have to be to control directivity:
    Think instead about the size of the sound radiator and the size of the wave it is propagating.
    To control directivity the radiating surface ( or baffle or horn mouth ) has to be LARGE in relation to the wavelength involved.
    A 2.0 cm radius piston (ka= 1.0) would be about 3 kHz.
    Significant directivity ( Ka= 2.0) does not happen for a 2 inch piston until about 10 kHz.
    ( Ka= 2.0) for a 20 inch piston until about 1 kHz.
    ( Ka= 2.0) for a 200 inch piston about 100 Hz.
    ( Ka= 2.0) does not happen for a 400 inch piston until about 50 Hz. :rolleyes:
    "Not a Speaker Designer - Not even on the Internet"
    “Pride is your greatest enemy, humility is your greatest friend.”
    "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

    Comment


    • #3
      Re: At what frequency does bass become directional??

      Bass goes from omni-directional to directional at the baffle step frequency, where the baffle is one wavelength. But as one wavelength at 100Hz is eleven feet, and it only gets longer as you go lower, directional subs are for all intents and purposes non-existent, in the home at any rate. The driver never has to face you.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

      Comment


      • #4
        Re: At what frequency does bass become directional??

        Originally posted by billfitzmaurice View Post
        Bass goes from omni-directional to directional at the baffle step frequency, where the baffle is one wavelength.
        This.
        Being defeated is often a temporary condition. Giving up is what makes it permanent.

        Scanspeak Revelator R2904/7000's, Scanspeak Revelator 15M/4531K00's, Scanspeak Revelator 22W/8857T00's, Eminence NSW6021's.
        MiniDSP 4x10HD. ICE Power amplification and an iNuke 3000.

        Sennheiser HD650's powered by TEAC amplification.

        Comment


        • #5
          Re: At what frequency does bass become directional??

          Originally posted by Ray Tremblay View Post
          This.
          If this is the case wouldn't a 1ft baffle have a baffle step frequency of 343 hz? If so that would mean frequencies below that would be omni directional? So therefore difficult to to locate?

          Comment


          • #6
            Re: At what frequency does bass become directional??

            use the KISS method for this. basically any thing below 100 hz is going to be Omni directional 99 % of the time.
            craigk

            " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

            Comment


            • #7
              Re: At what frequency does bass become directional??

              Originally posted by craigk View Post
              use the KISS method for this. basically any thing below 100 hz is going to be Omni directional 99 % of the time.
              And with this being said, if you can still clearly and honestly locate the sub with your ears...... Turn it down and get more sub/amp. Hearing the driver/enclosure is different than localizing the bass notes.

              Comment


              • #8
                Re: At what frequency does bass become directional??

                I'm not so sure about the use of the term "bass", but to determine when a drive unit is no longer omni, the beaming point is what I go by. which is approximately speed of sound divided by the effective diameter of the drive unit, divided by 2. ( you can use 1/4 wave if you like, but 1/2 wave is my rule of thumb)

                speed of sound = 13500 in/s (varies with temp; close enough for rule of thumb calculations)
                effective diameter = half-surround to half-surround. if it's a non-circular unit, use the smallest dimension.

                i.e.;
                Driver with 2" effective diameter: 13500/2"/2 = 3375hz
                Driver with 10" effective diameter: 13500/10"/2 = 675hz
                ErinsAudioCorner.com

                Comment


                • #9
                  Re: At what frequency does bass become directional??

                  yep +1
                  craigk

                  " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

                  Comment


                  • #10
                    Re: At what frequency does bass become directional??

                    For deep bass the baffle isn't important but room boundaries are. Positioning is everything to determine when the boundaries stop re-enforcing bass and we can determine location.

                    So, for every system in its room that point will be different but 100-300hz is the range.

                    Comment


                    • #11
                      Re: At what frequency does bass become directional??

                      You can begin to localize the source of the low frequencies somewhere above 100Hz. If the subwoofer has higher distortion, you can localize it even easier.

                      If you don't want to know where the subwoofer is placed, cross it over as low as possible, preferably well below 80Hz.
                      R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
                      Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

                      95% of Climate Models Agree: The Observations Must be Wrong
                      "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

                      Comment


                      • #12
                        Re: At what frequency does bass become directional??

                        Originally posted by nigelb View Post
                        If this is the case wouldn't a 1ft baffle have a baffle step frequency of 343 hz? If so that would mean frequencies below that would be omni directional? So therefore difficult to to locate?
                        A wavelength at 1130Hz is one foot. But that has nothing to do with directional location, which is based on the distance between your ears. We directionally locate via triangulation, comparing the difference in arrival time and phase shift of the sound at the two ears. If the wavelength is sufficiently long we can't directionally locate it because our ears are too close together to discern enough difference in arrival time and phase shift to triangulate the source.
                        www.billfitzmaurice.com
                        www.billfitzmaurice.info/forum

                        Comment


                        • #13
                          Re: At what frequency does bass become directional??

                          Originally posted by scholl View Post
                          So, for every system in its room that point will be different but 100-300hz is the range.
                          Bingo!
                          Wolf
                          "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
                          "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
                          "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
                          "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

                          *InDIYana event website*

                          Photobucket pages:
                          http://photobucket.com/Wolf-Speakers_and_more

                          My blog/writeups/thoughts here at PE:
                          http://techtalk.parts-express.com/blog.php?u=4102

                          Comment

                          Working...
                          X