Announcement

Collapse
No announcement yet.

Box alignment/tuning - different perspectives

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

  • #16
    Re: Box alignment/tuning - different perspectives

    A couple comments on rooms and bass. Because rooms are acoustically small spaces at low frequencies all of them have a "Schroeder Frequency". This is the frequency at which the room begins to take over and control the preceived response of the speaker. The Schroeder Frequency is based on the rooms volume and wall / ceiling/ floor surface area, the average absorption coefficient of the surfaces, and the T60 reverberation time of the room.

    Based on this formula my family room has a Schroeder Frequency of 197 Hz. Most rooms will typcially fall in the range of 180 - 250 Hz. What happens below this frequency is that the acoustically small dimensions (with respect to the long wavelengths at low frequencies) and parallel walls of the room begin to control the behavior of low frequency propagation. This is where room gain gradually begins to roll-in along with any near-boundary effect, as Allison demonstrated. And, because of the parallel surfaces between walsl and ceiling and floor, standing waves develop with nulls and peaks at different locations in the room.

    This is why Pallas (and many others, includeing Toole) recommend multiple subwoofers. When placed properly within the room their combination of peaks and nulls can be made to fill-in and significantly smooth the response in the room. While everything Pallas said is correct, there are a couple of things that change the weighting of these effects.

    First, if you are like me you tend to sit in the same place when you listen to music or the home theater. If this is the case, you are likely much less concerned about how evenly distributed your bass response is veruse how it sounds where you are sitting. For me it was not hard to find subwoofer placement that gave me very nice bass where I sit, and I don't worry so much about other places in the room.

    Second, when I turn the subwoofers off and listen to speakers with differing bass characteristics from my Continuums that are -3dB around 70hz to my Kairos that reach near 40hz there is most definitely a difference in how the bass sounds in my room. In addition, I can listen to the Kairos both vented and sealed. The differences here are all below 50Hz and it is quite obviously apparent. Even changing the tuning frequency changes the perception of the bass. So, it really isn't correct to say that the F3, slope, and Q of the bass are irrelevant. These are easily seen to make a difference, even when the room still controls much of our perception of the bass.

    Now, I don't want to poo-poo efforts made to reduce the room's influence. The method Pallas gave is certainly valid and useful, so are bass traps, Room EQ, and use of dipole speakers to change the pressurization of the room . I'm just saying two things - If you listen in one location it doesn't have to be that complicated, and the differences between different bass alignments can certainly be audible.

    Jeff B.
    Click here for Jeff Bagby's Loudspeaker Design Software

    Comment


    • #17
      Re: Box alignment/tuning - different perspectives

      Originally posted by lsiberian View Post
      I personally aim for low Q systems. I'm not sure I qualify as an FM though.

      Jeff B does seem to have quite the fan club here.
      There's nothing special about me. I don't even know what an FM is?
      Click here for Jeff Bagby's Loudspeaker Design Software

      Comment


      • #18
        Re: Box alignment/tuning - different perspectives

        Originally posted by Jeff B. View Post
        There's nothing special about me. I don't even know what an FM is?
        FM = Frequency Modulation :D
        "We are just statistics, born to consume resources."
        ~Horace~, 65-8 BC

        Comment


        • #19
          Re: Box alignment/tuning - different perspectives

          Originally posted by Tin_Ears View Post
          FM = Frequency Modulation :D
          Hmmmmm doesn't seem to fit the context. Somehow I figured it was something like Frequent Mor0n. Which probably fits me fine.
          Click here for Jeff Bagby's Loudspeaker Design Software

          Comment


          • #20
            Re: Box alignment/tuning - different perspectives

            I've gotten used to alignments where the passband is tuned as flat as possible, even for small systems. Yes, the bass does sound a bit lean with that type of alignment, but OTOH with a bump in the pass-band at or before Fb, the bass just sounds "wrong" to me.

            If I ever want to bump the bass up a bit, that's what the bass knob or EQ is for.

            As always, YMMV.
            Brian Steele
            www.diysubwoofers.org

            Comment


            • #21
              Re: Box alignment/tuning - different perspectives

              FM = Forum member

              Comment


              • #22
                Re: Box alignment/tuning - different perspectives

                I prefer Bass Reflex with a sub-sonic electronic filter for Xmax issues. Horn would be great though size for most rooms would be low on the WAF. This is for home theater applications. Diffferent system for music and different room. Even though you can DSP the response flat that is only one location and the more drivers you add the more difficult I believe it is to resolve phase issues coming frmo multiple directions. Also in a home theater most of the action occurs in front of you not around you. Take a space shuttle launch sequence. You used to be able to compare a real event to what was being recorded and if you could reproduce that sound your system has it "right". I know not anymore with movies but a standard that I think stills applies.

                Just not a fan of turning my movie room into a massive car system....to each his own like every opinion everyone has one.

                Comment

                Working...
                X