Now for a different cabinet twist...

Collapse
This topic is closed.
X
X
 
  • Time
  • Show
Clear All
new posts
  • Hank
    Super Senior Member
    • Jul 2002
    • 1345

    Now for a different cabinet twist...

    Grand Poobahs and others, I've long been intrigued by pyramid and tetrahedron cabinet possibilites and one idea in the back of my mind is a tetrahedron tower. The obvious attractions are time alignment of drivers and no parallel internal walls (no internal standing waves). A post on HTF regarding Acoustic Reality's new kit to for a monitor-size pyramid has resurected my interest.
    This website is for sale! acoustic-reality.com is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, acoustic-reality.com has it all. We hope you find what you are searching for!

    Acoustic Reality's tetrahedron towers are on their web site:
    This website is for sale! acoustic-reality.com is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, acoustic-reality.com has it all. We hope you find what you are searching for!


    J&T, please share your related thoughts/experiences. This novice anxiously awaits.
  • Andrew Pratt
    Moderator Emeritus
    • Aug 2000
    • 16507

    #2
    Interesting design...I don't know much about the various aspects of that speaker but Jon really likes that tweeter (same on I'm using in the M8a speaker) and the revalators have a good rep too....minimalistic crossover could be a point of contention though since from what I understand the XT25 isn't the easiest tweet to get right.

    PS I fixed your links so that they are clickable...in future please use the URL button when posting links.




    Comment

    • PMazz
      Senior Member
      • May 2001
      • 861

      #3
      My, we're easily distracted.

      Isn't that the way it always goes Hank? A project on the drawing board and another going into the oven.

      Not sure I'd go thru all the trouble of making the enclosure that shape. Unless you're going for looks, of course. I think a well built enclosure with some internal damping is all that's needed, myself.

      Pete
      Birth of a Media Center

      Comment

      • JohnR
        Junior Member
        • Oct 2002
        • 7

        #4
        I don't know how the link popped up again, but that was a kit that was offered well over a year ago but none were ever delivered, as far as I know.

        I was wondering about the "no standing waves". My understanding is that any shaped volume will have resonance modes, see eg pp 281-285 of F Alton Everest, "Splaying one or two walls of a sound-sensitive room does not eliminate modal problems, although it might shift them slightly and produce somewhat better diffusion". So, are there really benefits to non-parallel walls in speaker cabinets?

        JohnR

        Comment

        • Andrew Pratt
          Moderator Emeritus
          • Aug 2000
          • 16507

          #5
          John was that refering to the room or the speaker cabinate? There should be benefits of non // walls in a speaker but it depends on the freq's the speaker is playing...i.e. for subs its a non issue given the wave length of bass waves




          Comment

          • Hank
            Super Senior Member
            • Jul 2002
            • 1345

            #6
            Pete - I'm not dropping the line source pursuit and I won't be building my tetrahedron towers for a while, if ever. Now who was recently distracted by a post about horns?

            Andrew, yes, he was speaking of room walls, and I think the reason it didn't help was that he was speaking of making one or two walls non- parallel. You'd have a very strange room indeed if you made all four walls, ceiling and floor non-parallel.

            John, I think standing wave problems are related, but different than enclosure wall material resonance problems. Maybe I'm all wet, but here's my novice understanding:
            Standing waves are produced mainly by parallel surfaces, whether inside speaker enclosures or room walls. Practically speaking, you can't make room walls non-parallel, so taming the frequency emphasis nodes takes some rather large acoustic absorption materials "tuned" to absorb the excess frequencies. Wall material (room or cabinet) resonances exist with or without standing waves present and are due to the inherent mass/density of the wall material and the frequency at which it resonates.

            My point is that regarding cabinet wall resonance, if you eliminate parallel cabinet walls, you eliminate standing waves and your then left with the smaller magnitude problem of cabinet wall material resonance vs frequency, which you can deal with by selecting wall material, dampening pads, constrained layer sandwich construction, etc. I think that without standing waves, the material resonance "problem" is less of a problem and can be dealt with less expensively, ie less bracing and its associated cost and labor.
            If I'm wrong about any/all of this, remember I'm a novice trying to learn and am eager to be corrected

            John, you're right about the sub enclosure. The long wave lengths don't excite resonance in the cabinet wall material. That's why you can use the less dense plywood rather than MDF - no difference in material resonance at those low frequencies.

            J&T, are you listening (reading)?

            Comment

            • ThomasW
              Moderator Emeritus
              • Aug 2000
              • 10934

              #7
              Hank

              I'll be posting more tomorrow. At this point the $.50/min connection fee is a little pricy to play around on the forum Jon is still in Germany and will be home this W/E.

              The Everest quote pretty much explains how these enclosures operate. Nonparallel wall enclosures offer somewhat better performance over a standard box. But neither Jon nor I feel that the benefit is worth the work, when compared to a properly build 'normal' box.

              If the goal is to create a time aligned design, people should understand that the drivers must be aligned with in 1mm. And an 'o-scope' is needed to ensure that alignment is accurate. 8O

              We will roughly physically align the drivers on the front baffle. That's why there are pieces of 1/4" material used, and why sometimes we rebase the drivers and at other times we don't. With that rough physical alignment in place, the XO is then used to create the best phase response for the system.




              theAudioWorx
              Klone-Audio

              IB subwoofer FAQ page


              "Complicated equipment and light reflectors and various other items of hardware are enough, to my mind, to prevent the birdie from coming out." ...... Henri Cartier-Bresson

              Comment

              • Dennis H
                Ultra Senior Member
                • Aug 2002
                • 3791

                #8
                If the wavelengths are short enough to resonate inside the enclosure, they are easily damped by the stuffing. I'd think non-parallel walls would only be useful in an enclosure with no stuffing.

                Comment

                • JonMarsh
                  Mad Max Moderator
                  • Aug 2000
                  • 15259

                  #9
                  Hey, here's my 0.02!

                  It is of some value, because it distributes modal frequencies over a range. It doesn't elminate them; if you want to do a finite element analaysis to approximate the behavior, you might say you knock down the Q and energy at anyone frequency, and this is a good thing.

                  This is also the basic concept/advantage of the B&W Nautilus principle, with the taped cabinet, the side to side mode is distributed, and by using damping material through the length, the long mode is greatly attenuated.

                  Once you get serious about internal cabinet damping, and particularly when, with a cabinet like the M8, you have a variety of effective internal dimmensions because of the extra baffles, you reach a point where you have to carefully weigh the effort and expense against the results.

                  I'll use non-parallel walls in the "Mano e' Mano" arrays, becuase it will give me more usable LF volume for a given external box volume, and then effectively I will have a "lateral" nautilus system for the ribbon, which will be highly damped.

                  Still pondering whether or not to leave space for a small HF ribbon array. That would probably actually just used a routed trapezoidal groove with damping for the rear chamber. But it may result in too wide a front panel, compared with what I would like.

                  Analysis not complete.

                  As I think Dennis or other raised the question there could be issues regarding the lateral dispersion at the crossover point for two side by side ribbons- but in Thomas's system, which only uses an L-R 4th order, it works pretty well. I'd probably use (or at least try) my Hi-Finite Slope crossover, since it would reduce overlap to less than 1/2 an octave. (48 dB/octave slope for 1st 50 dB attenuation).

                  Regards,

                  Jon




                  Earth First!
                  _______________________________
                  We'll screw up the other planets later....
                  the AudioWorx
                  Natalie P
                  M8ta
                  Modula Neo DCC
                  Modula MT XE
                  Modula Xtreme
                  Isiris
                  Wavecor Ardent

                  SMJ
                  Minerva Monitor
                  Calliope
                  Ardent D

                  In Development...
                  Isiris Mk II updates- in final test stage!
                  Obi-Wan
                  Saint-Saƫns Symphonique/AKA SMJ-40
                  Modula PWB
                  Calliope CC Supreme
                  Natalie P Ultra
                  Natalie P Supreme
                  Janus BP1 Sub


                  Resistance is not futile, it is Volts divided by Amperes...
                  Just ask Mr. Ohm....

                  Comment

                  Working...
                  😀
                  😂
                  🥰
                  😘
                  🤢
                  😎
                  😞
                  😡
                  👍
                  👎
                  Searching...Please wait.
                  An unexpected error was returned: 'Your submission could not be processed because you have logged in since the previous page was loaded.

                  Please push the back button and reload the previous window.'
                  An unexpected error was returned: 'Your submission could not be processed because the token has expired.

                  Please push the back button and reload the previous window.'
                  An internal error has occurred and the module cannot be displayed.
                  There are no results that meet this criteria.
                  Search Result for "|||"