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RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition)

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In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by josh358 on October 06, 2010 at 09:27:14

Josh, I hear and understand your 'materials' based ideas.

However, please consider that 2 different designs with the same material can have different characteristics.

Where I am heading is that while I have been thinking about the mass of the frame and total system mass, I've also been trying to think of ways to minimize such frame mass while maximizing rigidity....in all planes. If the resonant frequency is raised past the bass / midbass region, I would hope for greater clarity.
This consideration is also why I will NOT use metal 'bridgework' in any additional supports for my reframe project. The difference is 'speed of sound', at the metal / wood interface may actually reflect vibrations back into the frame......muddiness could result.

Too much is never enough

Follow Ups:

RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - josh358 07:15:18 10/07/10 (8)
Hmmm . . . it seems to me that a rigid frame coupled to a high mass (your house and the earth) should be functionally equivalent in some regards to a massive frame.

Anyway, I don't think you want to raise the resonance frequency, rather lower it, because the ear is more sensitive to midrange frequencies than to bass ones.

I wouldn't worry about reflections from the metal. Yes, they will occur, but the same reflections occur when the wood contacts the air, there's just as bad an acoustical impedance mismatch. What you want is damping, and metal attached to wood is a good way of damping resonances.

I still tend to think that the right way to do this is with a massive, rigid, well damped frame. The frame should not make sound. The diaphragm should move with respect to a fixed origin, not a moving one. Transverse waves should be absorbed by the Milloxane and edge damping strip. But of course that's just theory, I haven't played with most of this myself (though I plan on finishing my own stands one of these days, I'll probably put some metal strips on the edges to stiffen the frame and maybe some Mye-style rear braces if I can accommodate them).
- RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - pictureguy 09:01:03 10/07/10 (7)
  I'm still mulling this whole thing over.
  
  When I started reading this thread I thought that maybe somebody had done enough real measurements to begin to get a theory together. A proper theory will allow predictions to be made...accurately.
  
  I need to figure out just what was measured and what all the parameters mean. Someone (the OP?) was getting excited about a 1db increase in RMS power or some such.
  
  Also, I don't know the procedures that were followed. Was there a 0db point established with test tone and an independent meter? The OP also writes about what appear to be different places to set the gain. and has, to his credit simply left the microphone gain alone after the initial setting. Some mention is made of Windows 7 having new abilities. Is this program available for MAC? didn't think so. Any equals?
  
  The reason I don't want metal is not only the reflected vibration aspect but the darn stuff, in a beam form, will also store a lot of energy....which will 'slur' the sound, eventually. My design concept will provide increased rigidity for the panel in the torsion / bending moment sense while providing a 'tripod' of contact points.
  
  And while the OP writes that he briefly experimented with a single speaker I never found out if differences between drivers existed...at least observable.
  
  Nope, I'm not yet convinced, though remain open to this data. Let me continue to read and try to understand what was done. So, while I'm still a little skeptical, I'm also optimistic that this path may lead forward to what I consider the 'holy grail' of Magnepan 'research'.....a reasonable theory leading to practical results which improve the breed.
  Too much is never enough
  - RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - josh358 09:50:01 10/07/10 (6)
    The stored energy and reflection problems are really two sides of the same coin. However, reflections are advantageous in one sense -- they're what allow the diaphragm to make sound! An infinitely massive frame would have an infinite impedance mismatch with the diaphragm, meaning that all of the energy would stay in the driver and either be transferred to the air or be damped by other means. Which, I think, is what you want in a loudspeaker, although there are those who disagree.
    
    Keep the frame and pole pieces stationary -- I can't be sure that it's the right approach, but I don't think you'll find a speaker designer who has ever taken a different one, because anything else reduces output, and probably increases coloration.
    
    Anyway, metal will store energy, sure, as will wood, but the behavior of these materials when they're constrained to one another can be far superior to the behavior of either one on its own. That's easily demonstrated by knocking on some wood, banging on some metal, and then fastening them to one another and banging on the combination. Since with a given dimension their resonances are at different frequencies owing to the differing velocity of sound in each, they tend to damp one another. This is why forex Magico uses an aluminum faceplate in tight contact with baltic birch.
    
    I'm not sure that that makes metal the best solution. For one thing, high Q resonances can actually be less audible than low Q ones. (Has anybody ever experimented with tuning the resonances *between* notes, as opposed to *on* them, to see what it does to the sonics?). I've read in Olive and Toole that a resonance has to be a full 10 dB at Q=50 to be audible in music! And in this case we're spreading resonances. My pet hypothesis is that wood frames sound better because the resonances are musical, and this suggests that they may sound better because they have a high Q and so are less audible as well. That isn't true of MDF, which is fairly amorphous and so has a low Q. It also may not be true of a metal/wood sandwich, or of plywood.
    
    I think there's room for experimentation here, to verify and explain what PG and so many users of wood frames have reported about the beneficial effects of wood frames on sound quality. Blind listening tests would be good -- MDF vs. wood, say, or wood vs. metal-reinforced wood. So I think would the frame stimulating experiment I suggested elsewhere -- attach a voice coil to a piece of frame material, record the sound, and try adding it back at the right level to the original source material while listening with headphones to see if you can hear a difference, and, if so, which materials sound best. Because I don't think direct measurements of the frame of the sort John Atkinson does will tell you that, they can tell you that a frame is more or less resonant at various frequencies but not what it does to the sound.
    - RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - pictureguy 12:36:02 10/07/10 (5)
      re: constrained layers. This is good for 'box' speakers where an inert enclosure of zero flexibility would apparently be best.
      We have a very inert frame in the current Magnepan and a live material is seen as nothing but an improvement. So, I won't try to use most box speaker theory and practice to predict what will happen to a panel when modified.
      
      The idea is to get a rigid frame. This reduces 'flex' and 'twist' in the driver.
      Get the mass down. You've only got so much energy to put into the system. Too much mass and you may lose the liveness of the frame. Again, perhaps opposite of a box design.
      
      I've lost track of who / what / when / where I first saw an accelerometer mentioned. Cheap ones are available at Radio Shackup. running one to a little preamp than to audio analysis software should do the trick. I have seen accelerometer apps for my Ipod Touch....But they may be more automotive than analytic.
      Gather data, compare to listening tests, figure out what drives what, come up with a theory, make some predictions and than test. Repeat as necessary.
      Go around the circle until you have a theory which when you do as theory suggests results in predictable changes.
      Too much is never enough
      - RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - josh358 14:07:14 10/07/10 (4)
        
        In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by pictureguy on October 07, 2010 at 12:36:02
        
        A box frame has additional requirements. In particular, it has to constrain the backwave without transmitting it to the room. However, beyond those requirements, the goal is the same -- provide a fixed attachment point for the drivers, one that doesn't "play along" with the speakers and distort the sound by moving in antiphase and resonating.
        
        An undamped vibrating wooden cabinet can't reproduce sound cleanly. It's way too massive. That means it will produce frequency-dependent amplitude variations in the frequency response, and ringing in the time domain. Exactly the sort of resonant phenomenon we try to eliminate in our speakers and listening rooms.
        
        That being said, many people have had good results with wood frames (which I haven't heard myself and can't, no pun intended, opine on). To the extent that cabinet resonances are impossible to eliminate, I do believe that the high Q resonances of wood may be more euphonic and similar to the sound of musical instruments. That would correlate well with the audible difference between the distortion + noise of cone and ribbon speakers. The ribbon spectrum distortion sounds better, because its more euphonic.
        
        Getting mass down is, I think, problematic. Speaker technologies may differ, but Newton's laws still apply, and the diaphragm wants to push against a high mass. As I said earlier, rigid frames help in that regard since they can couple the drivers to the mass of the base, of the house, eventually of the earth. But we're talking torsion with a long moment arm here, as well as resonances, and even a very rigid frame will twist. So the ideal frame is neutronium, as far as I'm concerned, though I'd settle for iridium or even depleted uranium in a pinch. As I said, I'd also be concerned about pushing the resonant frequency up, rather than down. You really want the resonances to be outside of the audible range, if possible, and in the least audible parts of it if not.
        
        In practice, a number of people have reported good results with sand bags, lead shot in their Mye frames, etc., which lends real world credence to theory. Also the OP, JBen, had bad results with less massive wood frames.
        
        PG's frames don't have very high mass, but they aren't rigid, either, his design philosophy allows -- encourages -- them to resonate.
        
        RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - pictureguy 15:38:57 10/07/10 (3)
        
        In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by josh358 on October 07, 2010 at 14:07:14
        
        I believe PG is on to something.
        
        Now, mass and rigidity are not related. You can have all 4 cases. Hi and lo mass with hi or lo stiffness. Design must 'play into' the characteristics of the materials used to execute it. Wright and Gropius were masters of this.
        I'm going for low mass and high stiffness. And to not confuse things I will use some back support on the panel. Think in 3 dimensions, not planar.
        
        I am not going to discuss my actual design just yet. I'm taking woodshop classes so I can get at the toolset. After I take the 2 intro classes, I'll be able to take a class as 'self directed' and spend a couple hours a week working on just what I want. Frames first....
        And where I'm going to school, they have access to some real special wood. I bought some Sipo for my project. Man, that will look terrific with an oil finish.
        Than a new TV / Stereo support. I have a 60" bigscreen sitting on a cabinet which I hate. That will be replaced with something also of novel design. Think allthread and thermopane.
        Too much is never enough
        
        RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - josh358 16:01:30 10/07/10 (2)
        
        In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by pictureguy on October 07, 2010 at 15:38:57
        
        If you change what he does, though, there's no guarantee you'll get the same results.
        
        RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - pictureguy 16:15:38 10/07/10 (1)
        
        In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by josh358 on October 07, 2010 at 16:01:30
        
        Agreed. However, I'm willing to take a chance on my personal theory.
        What PG says makes sense to me and has some theoretical framework. I'll believe PG until I learn otherwise. If I could go listen to some of his modd'd speaker, here and local, i'd do it in a heartbeat. What I keyed into was the demonstrable difference between real wood and 'the other stuff'.
        If the principle is sound, than I'll get similar results. Note that I'm not going to do any crossover stuff...at least not right away. Part of the reframe will be the construction of a pair of crossover boxes.....which will be large enough to take large aircores and the larger caps needed for upgrades. Don't know why, but good caps are nearly always LARGE.
        
        If there is not a theoretical, predictable basis for any of this, it all works out to some kind of voo-doo. I'll go into business making your stereo sound better by holding a seance. Wait till you get THAT bill! And think of the frequent flier miles as a fly all over, making good systems better and communing with 'The Audio Spirits'.......
        Too much is never enough
        
        RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) - josh358 19:13:42 10/07/10 (0)
        
        In Reply to: RE: Measuring Maggie stuff with Cool Edit Pro (or Adobe Audition) posted by pictureguy on October 07, 2010 at 16:15:38
        
        So check this out -- scroll down to the five waterfall plots in the comments:
        
        http://www.avguide.com/blog/the-best-loudspeaker-i-ve-heard-the-magico-q5?src=Playback
        
        These are of enclosures rather than frames, of course, but they're pretty interesting nonetheless. I wonder what Magico's "heavy damping" consists of (I've seen the pictures of the "heavy bracing" ad nauseam in their ads). Maybe they borrowed Dawnrazor?

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