In- phase out of phase, absolute polarity is one different from the other?My pre-amp has a polarity button when I use it my system seems to sound better is it correcting something that's not right? Mike
Magfan...I rebuilt my MG1.6 crossovers, so I am familiar with them. The low pass (woofer) is 12dB and the high pass is 6 dB. The break frequencies are quite different (I can't remember the exact numbers).
The phase of the passed signal changes over the range of frequencies from below to above the break frequency, with the total change being as I cited. It is not a fixed phase shift. I suspect that there is a frequency between the MG 1.6 high and low break frequencies where the phase difference is closer to 180 degrees than zero, and that's why the tweeter is hooked up "backwards". Physical spacing of the drivers are also a factor. When both drivers are generating sound you want them to be in phase or they will tend to cancel and there will be a sharp notch in the overall frequency response. As a matter of fact, the best way to determine the crossover frequency is to reverse the polarity of one driver and look for that sharp notch.
Eldartford, silly question, than. If 6db / 12db are 90degrees apart, how could you get the drivers back to phase in the Magnepan 1.6, which I have confirmed does use 'one of each' in its x-over? Seems they'd be 90degrees out?
Also, with most if not all modern rock, absolute phase is strictly of academic interest, since no effort is made to preserve or even identify phase. On some recordings in the past, my absolute phase switch made a difference, on most recordings, not.
Magfan, I was trying to keep this simple as the primary concern was phase versus polarity. Yes, most speakers don't just have no phase shifting at all in their crossovers. Perhaps I should have limited what I said to single driver speakers.
Eldartford, again I know this but was trying to keep it simple and again there are no such complications with a single driver. As I said before, I had dealt with different manufacturers how to deal with the onset wave at the microphone and from the drivers. I had a pair of Tannoys long ago and like JBL they treat the onset wave as a withdrawal of the drivers. I always reversed the speaker leads for better sound.
It's not even that complicated. 6db filter preserves phase. 12db filter inverts phase. On my 1.6 maggies, the x-over has both 6 and 12 db/octave elements....can't for my worthless life remember hi or low is which, but as a result, the HF part of the panel is hooked up out of phase with the LF part of the panel.
Tbg...As I read your comment about some drivers being hooked up out of phase, it seemed as if you had no idea why they would do this. So I explained.
Even if cone excursion matches the electrical signal without delay (doubtful) the resulting sound wave will reach maximum pressure when the cone RATE of movement is maximum...not when the excursion is maximum. That's worth 90 degrees. Similar things with the mic. All in all it's more complicated than you suggest, and it's hardly surprising that opinions vary about phase. Some driver manufacturers (JBL for one) define polarity as cone move IN for a positive electrical input. I learned this when I was connecting a JBL driver in parallel with one of another manufacturer.
Eldartford, as I said. But I don't know what you mean that speaker cones don't move in synchronically with the electrical signal. What do they move in synchronically with? If you mean, some manufacturers put some out of phase, I said that also.
When a crossover has a 180 degree phase shift at the crossover frequency (12 dB) connection of the driver out of phase is the right thing to do.
Neither the mic diaphram nor the speaker cone moves in sync with the electrical signal, so it is not as simple as Tbg suggests. Some speaker manufacturers (JBL for example) have the cone pull IN for a positive signal.
Chazz, I really don't understand this confusion, nor do I understand why Krell would call it a phase button. I have owned two line stages with polarity or invert buttons. Invert makes sense as it changes the polarity on both inputs. I guess also that it would make sense to call a subwoofer phase knob either phase, polarity, or even invert as there is just one speaker being controlled.
It is also confusing that some speaker companies invert the midrange driver and that some see the onset wave as negative and others positive. It seems to me that the withdrawal of the microphone represents an onset of the sound wave so the microphone signal should be inverted to push the drivers out.
Part of the problem, IMHO, is that most recording engineers care little about this. As Clark Johnson always says many, if not most, recordings are a mix of polarities as mikes are connect both ways. While presently I do not have the capability to invert or switch the polarity for recordings, in the past I have often found one setting sounded much better. Other recordings, perhaps because of what Clark says, yielded no best setting.
Why don't I have the capability to switch polarity. Both of my line stages could easily have such capability. The H-Cat has parallel outputs, so when used as single-ended, you could just switch the negative and positive leads to change polarity. My Exemplar line stage is parafeed as just changing the leads to the outputs would allow a polarity switch. Neither designer focussed enough concern to both with this, although both said they could alter my unit to provide the switch.
TBG Read your last post to the phase question.It makes sense what you say that phase would be both speakers IN PHASE that is each going out at same time together.But on sub they have 180 degree polarity knob so why wouldn't that be called phase?And if you are doing things right and have your speakers together wires properly why does my Krell have phase button (I assume for recordings out of phase with way recoding done) and isn't a polarity switch? It is a bit confusing to the simple of us. Cheers Chazz
They both entail switching the phase of the signal that gets to the speakers, but phase means making sure both speakers are the same and polarity means that both speakers have their positives and negatives changed together. The real question is whether on a positive signal from the mike inputs the drivers of the speakers should retract or move forward. I think they should move forward to duplicate the wave onset.
Srajan did a nice bit on this.I have seen many pre's with phase control but not polarity.Even Wayne Dockery did a VTL 2.5 and said they were same thing. Chazz http://www.6moons.com/industryfeatures/polarity/polarity.html
Wow, how frequently words fail us. Most test records use the word "phase" to deal only with whether both speakers share the same positive and negative connections throughout all that goes before them. Usually if you experience the signature disconcerting location-less sound, one speaker's connections are wrong, the red connection on the speaker wire is connected to the black binding post.
Polarity involves whether what you get in the drivers moving outward when the microphone at the recording retracted as the sound impacted on it. This would work only were recording engineers meticulous in wiring all microphones the same. Since few are concerned with this, what you hear is unlikely to have similar polarities across all microphones. All you can do is to use your polarity button the way it sounds best on each record.
This is further complicated by how your manufacturer accomplishes polarity change. Most do so by adding another stage of amplification to invert the signal. This usually sounds worse than the preamp without this additional stage.
Elizabeth - In addition to that there are two different definitions of pinout for balanced cable. If amp and pre don't follow the same pinout phase will be reversed.
Planar speakers are nice because they don't create peaks and valleys of the bass with the distance.
It is important to distinguish between absolute phase and relative phase. There is no standard in the recording industry for absolute phase , that is why so many records sound better reversed. Relative phase means the speakers being in phase with each other. Perhaps they should be called polarity rather than phase, but no one does.
If you reverse (interchange) (+) and (-) wires you shift phase by 180 degrees, at all frequencies. That's why "polarity" (which way the wires are connected) is often described as "in phase" or "out of phase".
Sorry, Hotsauce, but you are wrong. Reverse the connections to one speaker and you reverse polarity on one channel. Reverse the connections to both speakers and you reverse polarity on both channels.
Now, perhaps, you were trying to say that, if you reverse the polarity of one speaker, the two will be said to be out of phase with each other.
It is estimated that about 50 percent of recordings are recorded in reverse polarity... so about half of your recordings should sound a little better with the polarity inverted.
Phase is frequency dependent as Kal said, and it is used by many as a synonym for polarity, which is not correct.
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