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Re: Backward Maggies - Not so backward?

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QuadTodd

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In Reply to: Backward Maggies - Not so backward? posted by DragonEars on March 10, 2007 at 19:00:18:

Did you reverse your speaker cables too?
Listening to the back side would make the "Absolute Polarity" (where's Geo Louis when we need him?) of what you were accoustumed to, move from a + to a -. In other words, if I have this right, the mylar panel in the stock listening mode vibrates out/towards you on a certain note. If you flip the speaker around without switching the speaker cable + & - around, on that same note, you would be listening to a suck in/away from you. Does this make sense?
If not, I'll go back to my cave...
Todd

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Re:Did not switch speaker wire polarity. - DragonEars 22:49:06 03/12/07 (6)
No, I did not switch speaker wire polarity.
I am not clear on "absolute polarity". Since the speaker receives an AC signal and puts out a sine wave, I don't understand why absolute polarity matters. Music/sound will have both components of the wave form (diaphragm push/pull = both sides of sine wave). A note/sound would have to be very low and VERY brief ( ie - 20hz tone for less than 1/20th of a second) to have only one side of the wave.
I need to understand "absolute polarity" better.
- Here's another try... - QuadTodd 03:25:39 03/13/07 (5)
  The classic example is of a trumpet player when they hit that first blast is an example of an outgoing wave. IF it was all recorded and played back with the correct phase, your stereo would produce a duplicate outgoing wave. By reversing the position of your speakers, this would no longer be outgoing and the correction for that would be to also flip the red/black speaker cable legs on both speakers. Otherwise you have another listening variable there.
  A better example would be a kick drum (especially since we are all planer people here). By listening to your Maggies' backsides, you would be hearing a kick drum with the petal towards the audience, instead of by the drummer's seat, so when he pounds on it, the wave moves away from the listener instead of towards him. OK, another one would be talking while breathing in instead of out - didn't I see that as a TV commercial lately?
  I also understand what you are getting at with the "inverse square law" with more control on the magnet side, but to my thinking - and what do I know, a pair of Quad 63s live here with no magnets - this would only apply if there were two mylar diaphragms (and two sets of drive wires. Since the wires are glued to the panel, this is effectively one piece so the force would be the same on either side. If there were more force or control on the magnet pole side than on the plain side, the result would be a loosening or, in the extreme, tearing of the mylar away from the wire.
  - Re: Soundwaves are compressed/decompressed air... - DragonEars 00:38:06 03/14/07 (4)
    Trumpets, kick drums and voices are all waves of compressed and decompressed air propagating out from the source. They are not like an object in motion or a wind blowing. Sound propagates as the molecules crash into each other and transfer their energy. Sort of like a compression wave in a slinky toy. The wave travels through the slinky, but the slinky does not go anywhere. The sound wave is a series of high and low pressure rings propogating out. If the music caused the air to blow like wind we would all look like that old Memorex ad with the guy sitting in the chair in front of his stereo with his hair blowing back. LOL (you can feel wind from bass ports, but that is different)
    I'm not familiar with how Quads work. Don't they use two charged screens that push and pull the diaphragm back and forth? Magnepans use wires glued to a mylar diaphragm. One side has many thin vertical magnets. The signal causes the wires to attract/repel to the magnets, vibrating the mylar. Since there are magnets on only one side, the forces changes as the distance does. Wires on Magnepans do come loose. They peel off the mylar eventually. This is from time, humidity and poor adhesive.
    - Re: Soundwaves are compressed/decompressed air... - QuadTodd 17:53:21 03/14/07 (3)
      A kick drum is not an object in motion? All these years I thought I've seen the skin move! What you are not following is that I was talking about the first transient - the inital blast of the trumpet, as I called it.
      By positioning your speakers backwards, instead of "the sound wave is a series of high and low pressure rings propogating OUT" (my emphasis), they are moving away from you towards your front wall, throwing 2 variables (position and wave front launch) into your new listening procedure. It might take two minutes to switch your speaker cables around to see if you can tell a difference.
      Quads use an electrically charged diaphram between the two stators. The first set of Magneplaners I heard was about 30 years ago so they are pretty familiar territory but the point was that the panel would tear itself apart if there was more force on the magnet side than the other.
      - Re:Ah, I get it now - DragonEars 22:27:21 03/14/07 (2)
        
        In Reply to: Re: Soundwaves are compressed/decompressed air... posted by QuadTodd on March 14, 2007 at 17:53:21:
        
        QuadTodd
        Yeah, I see what you mean. The first transient would definitely have a direction. A kickdrum definitely has a directional launch of energy. I'll try listening with cable polarity swithed.
        All bipolar speakers by definition launch the wave front and back, opposite polarity. The back wave reflects off the front wall and returns with, but slightly off the front wave. I know the space from the front wall is important, but the whole idea seems problematic to me. Now I'm trying to understand absolute polarity and reverse polarity and it is confusing me.
        Absolute polarity is dicussed elsewhere in this thread.
        Maybe I should stop thinking about it and just enjoy the music. It's a truly amazing thing, audio and the human ear. I've never heard Quads, only Magnepans and Martin Logans. I love the way bipolars sound.
        
        Re:Ah, I get it now - not so fast! - wazoo 05:17:20 03/15/07 (1)
        
        In Reply to: Re:Ah, I get it now posted by DragonEars on March 14, 2007 at 22:27:21:
        
        "A kickdrum definitely has a directional launch of energy." Yes, the initial compression zone leads the rarefaction zone, but is that what we *hear*? The most vexing problem when thinking about this issue arises from analogizing across phenomenological domains. Consider the post from "gymwear5@hotmail.com" which suggests the ultimate arbiters of hearing operate as "threshold triggered digital signal" generators. If this is so, we are insensitive to absolute phase. We simply hear the changes in pressure.
        Like you, I intend to settle this issue for myself this weekend.
        
        "Jazz is not dead - it just smells funny" FZ ♬
        
        This is my take - QuadTodd 13:58:05 03/17/07 (0)
        
        In Reply to: Re:Ah, I get it now - not so fast! posted by wazoo on March 15, 2007 at 05:17:20:
        
        I can hear polarity on some recordings, others have mixed results. For me, there is just not enough time to listen to all the music I want, now and in the future, let alone to spend it on deciphering if each recording is a + or - and then switching speaker cables accordingly. It may be more important to others, but then I don't the VTA on my tonearm either. Majority rules in this system and it sounds good on most recordings; if it doesn't, I chalk it up to 'it could have been better' whether it be polarity, mike technique or a tin-eared producer!
        DragonEars, I know exactly what you mean by the bipolar sound. 18 years ago, I was looking for a better amplifier and walked out with a pair of Quad 63s, thinking "What the hell just happened?".

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