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In Reply to: Re: Backward Maggies - Not so backward? posted by wazoo on March 12, 2007 at 07:11:35:
My bad - Original post had TWO topicsTopic 1) Maggie sound with pole peices in front
Topic 2) The forces/control on the mylar diaphragm when it is close vs far from the pole pieces. I should have posted them (my random thoughts) seperately.
Thank you for picking this up and cogitating on it.
I don't think this has any affect on the frontwards/backwards sound. This has me wondering about how the actual waveform is created/controlled by Maggies.
When the diaphragm's oscillation brings it near the pole pieces, the attracting/repelling forces are much stronger than when the diaphragm is away from the pole pieces. This means that the side of the sine wave/oscillation/mylar travel closest to the pole piece is going to have more power and more control. The side of travel away from the pole pieces will have less power and less control.
I am wondering what this does to the sound wave. It seems like it would create waves that were different on one half of their waveforms.
Follow Ups:
First of all, be careful when thinking about sound as a sine wave - that is merely a representational convenience. Actual sound is a longitudinal wave, not a transverse wave.Secondly, your logic concerning the behavior of the diaphragm in relation to the distance from the pole piece is faultless, but I'm puzzled how this relates to what we hear. If we only heard the compression of air molecules this would make absolute sense, but the rarefaction is just as much a part of what we hear as the compression is. The magnitude of change is the same regardless of which is the stronger (compression or rarefaction).
There is little doubt that the two sides sound different since they radiate through different materials - on one side through a nearly transparent piece of cloth, and on the other side through small holes in mostly solid matter. If dirty socks (or socks vs. naked - see the thread about socks) can affect the sound, surely the pole piece does as well.
I'm *NOT* insinuating that anyone is crazy, or even just wrong for preferring one orientation over the other. I'm just trying to understand why this should be so. Of course, I'm thinking about it from an engineering perspective which may be completely foolish. On the other hand, there may be some euphonic effect which arises from forcing the sound of the front wave through those little holes while the back wave is unimpeded - they *are* planars after all.
In any case, I need to try it for myself and reverse my speakers. This brings up one more thing which I’m finding difficult to comprehend – concern over absolute phase. Relative phase is one thing, and maintaining it is critical, but who knows which absolute phase is correct? How many times is the phase flipped through a signal chain? That chain starts, by the way, with the actual recording of the performance. Am I missing something?
I sincerely apologize to anyone who might be offended by this post.
WazooI understand that sine waves only represent amplitude and wavelength (strength and time). Sound waves are propogating waves of compression/rarefaction.
The question of difference of force/control of the mylar changing with distance from the pole pieces is interesting. There must be a difference. But like you said: How does affect what we hear?
As to the "Backward Maggie", I knew they would sound different. I thought they would only sound good one way. Less "stuff" in front of any driver is a good thing. I was surprised that I didn't dislike the sound. They sound different, but good . They should sound worse, but they don't. I don't understand.
Absolute Phase - I'm absolutely clueless
I don't understand why it matters. Does the human ear and brain care? A recording starts from silence, and then builds in amplitude. At some point the amplitude becomes great enough that we begin to hear it. When does phase start to matter? Does it matter? Why?The more I know, the more I know I don't know.
Ignorance is bliss.
It's good to know that I'm not the only one struggling to comprehend the issue of absolute phase. This weekend (when I have the time to mess around with such things), I'm going to conduct a few experiments and switching phase will be one. One of the problems with listening tests is that they can be colored by a priori beliefs. I'm going to construct a method that permits me to listen blindly (of course, I still believe that there won't be a real difference) - only my wife will know what the phase will be. At least I'll be able to settle the issue for myself.As I mentioned elsewhere, I would expect there to be a difference in the sound of each side of Maggies due to the different transparency of the materials on each side. I suspect that is the better explanation than the inverse square law effect, but what do I know? My other question should not be taken lightly - how do you know the absolute phase of each recording? There is NO standard to my knowledge. I haven't received an answer to the query about the alternations of phase throughout the entire chain of electronics - beginning with the actual recording. Is absolute phase maintained absolutely? To my thinking, this makes clear assertions about absolute phase highly suspect, but what do I know?
As for absolute phase, if you reverse your speakers, you should change the speaker cables to match. This is so that you are making a fair comparison and that you are not just hearing differences in absolute phase.Not that you are likely to hear them on maggies anyhow.
Yeah, you are right about the recording and also that few recordings are actually done so that all the parts are in phase. Most have some part if not many in different phase.
I plan on conducting experiments this weekend, so I'll have more to say later. For the moment (until I prove to myself that I'm mistaken), I don't really think it's a real issue. In any case, I'd bet about half of the recordings in my collection are out of (absolute) phase from the other half - should I be flipping my speaker wires back and forth trying to figure out which orientation is "right" for each disc? This sounds like a real PITA to me!Back in the late 60s, I had a receiver (Voice of Music) that had a phase switch on it, but I haven't (to the best of my recollection) owned a piece of electronics (except for subwoofers - for the obvious reason of RELATIVE phase) with such a switch since. There must be a reason for that, no?
The biggest problem with phase, to my knowledge, has to be the partial, frequency dependent shifts induced by various reactive components of a passive crossover.
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