What is (D) driver in your above post? Is it the tweeter?
Inverting the woofer when it was meant to be connected the other way is highly like to change the sound.
I would again encourage you to read this thread to understand how phase works:
Crossover mods for the AR4x - Mods, Tweaks, and Upgrades to the Classics - The Classic Speaker Pages Discussion Forums
If we take a two-way system with a crossover frequency of 2 kHz as an exaple we can first see that the tweeter is only reproducing about 3.5 out of 10 octaves of the audible spectrum. If we futher look at how much content there is at which frequency....
http://www.outline.it/articles_eng/OUT_Art_Watts_3.pdf
...we can see that the most content is below 2 kHz.
By inverting the tweeter instead of the woofer (IF inversion is necessary of course) we can reproduce the biggest part of the content with correct polarity.
Regards
Charles
http://www.outline.it/articles_eng/OUT_Art_Watts_3.pdf
...we can see that the most content is below 2 kHz.
By inverting the tweeter instead of the woofer (IF inversion is necessary of course) we can reproduce the biggest part of the content with correct polarity.
Regards
Charles
Charles,
The concept of "correct polarity", other than matching the polarity of each driver in a system is flawed for many reasons:
It is not unusual for recording consoles to reverse polarity from input to output.
A common feature of recording consoles is a polarity reverse switch.
The EIA RS.221.A standard for microphones to be pin 2 as "+" was issued in 1979, but by no means was universally adopted in mics made after that date. Prior to the standard (and many "classic" mics built before 1979 are coveted and still in use) there was no convention, other than what individual manufacturers used for their own microphones.
Bi-directional microphone's polarity is dependent on which side the sound source is on.
A dynamic (moving coil) microphone lags the phase response of a condenser microphone by 90 degrees.
As has already been mentioned, microphones can be placed on either side of instruments, the polarity is dependent on the side it is on.
In light of the possibilities for polarity reversal in the recording (and playback) system, there is roughly a 50% chance that any particular instrument or vocal you hear retains the "absolute polarity" of the original.
Art
Agree with Art. I'd go further and say that polarity, the way we are thinking of it, is a totally wrong concept. It is a non-entity, really. Who cares if you hear compression first or rarefaction first. You need to hear several cycles anyway before you can tell what it is that you are hearing. So, polarity has no meaning in the absolute. Polarity of the system, i.e., L speaker and R speaker should be the same when you listen because otherwise half the sound will be out of phase.
I agree with the above post. If you hear a kick drum at say 70 Hz and it takes 0.1/second to make that sound, there have been seven cycles so it hardly seems necessary to have 'correct' phase on the woofer.
Before looking into speaker cone behavior, how about observing some music signal amplitude in time domain, are the positive going (amplitude) always similar with the negative going? Knowing that some music shows more audible reversal than others, I guess they are not always similar. Who can record/capture the most non-similar?
Or, how about reversing the amplitude in time domain and see/compare the result in frequency domain?
Or, how about reversing the amplitude in time domain and see/compare the result in frequency domain?
Maybe on direct radiators it doesn't matter as much. But think about a bass horn with 9ms of propagation time from cone to mouth. Imagine the initial kick drum to suck in. Do you think there would be an effect on the perceived sound with regards to delay or otherwise? It may be fine if you used DSP to delay the tops to account for the extra time needed for the wave to come out. This can be simulated in Akabak of course by changing polarity - it's not the full delay of 9ms but the delay is one cycle of whatever frequency the sound is. There is almost a pre-ring followed by the main positive pulse. I have seen and heard it in a real bass horn and it sounds different.
Jay has an interesting point. I have looked at time domain traces of music and the positive side is not the mirror of the negative side. It's asymmetric in many areas - especially leading edge transients. Steady tones are symmetric about zero but when is music steady tones. I am not sure taking a FFT of inverted music does anything to frequency domain - it probanly imposes a half cycle phase shift at all frequencies.
Jay has an interesting point. I have looked at time domain traces of music and the positive side is not the mirror of the negative side. It's asymmetric in many areas - especially leading edge transients. Steady tones are symmetric about zero but when is music steady tones. I am not sure taking a FFT of inverted music does anything to frequency domain - it probanly imposes a half cycle phase shift at all frequencies.
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Can you share more? I would be truly amazed if you could detect 1 kHz with just 2 cycles. You are saying you heard a sound for 2 milliseconds and could identify what it was. Any sound heard for 2 ms is not a sound, it's a click. Of course, I could be wrong, but would like to see proof.
So, if I sit behind the drum player, suddenly I've ruined my musical experience? This does not make any sense guys. A wave is only a wave when you feel the entire wave. The information is in the wave not in where it starts.
You can generate a 2khz wave in Audacity and trim it to 2 cycles and listen for yourself. It would make a difference if it's cut off suddenly or smoothly tailed off with a window function as a sudden cut will generate higher order harmonics. So maybe 2 full amplitude cycles followed by a tail of a few cycles or a triangle window function 2 cycles wide with the peak amplitude lasting. For only fraction of the cycle?
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I have spent hours flipping polarity on various microphones, and suffered through many more hours listening to others doing the same during sound checks.
Reversing the polarity of a kick drum signal (alone) makes no difference whatsoever in the perceived sound listening on headphones, bass reflex, or bass horn subs.
With multiple microphones around a drum kit, the polarity of individual microphones makes some perceptible difference due to the frequency response of the combined mic response, not because of conforming to "absolute polarity".
And for the reasons outlined in post #44, there is only a 50% chance that any recording you may listen to will be representative of the absolute polarity of any instrument or voice.
Art
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Let's not compare speakers to sound recorded by mics that may or may not be flipped. If you listened to live un amplified drums sitting in audience say 15 ft away, do you think a speaker playing a recording of that same performance would sound more realistic if correct absolute polarity were observed.
This is similar to arguments by people who say phase doesn't matter and transient perfect speakers don't sound any different. If you look at the transient event on oscilloscope - the speaker that closest represents the signal as properly recorded by a mic with the correct absolute polarity has to sound more accurate/realistic.
Does a speaker that has a perfect right triangle step response not reproduce a drum strike more accurately than a speaker with symmetric LR2 XO with either the tweeter or woofer inverted? I certainly can hear the difference when the polarity of the tweeter is positive going like the woofer and time aligned. It makes a difference. Maybe a kick drum is not the best example. Maybe a bongo or a rim shot is more appropriate when accompanied by a high frequency component with a sharp leading edge. In this case having a reverse polarity woofer does not sound as realistic.
This is similar to arguments by people who say phase doesn't matter and transient perfect speakers don't sound any different. If you look at the transient event on oscilloscope - the speaker that closest represents the signal as properly recorded by a mic with the correct absolute polarity has to sound more accurate/realistic.
Does a speaker that has a perfect right triangle step response not reproduce a drum strike more accurately than a speaker with symmetric LR2 XO with either the tweeter or woofer inverted? I certainly can hear the difference when the polarity of the tweeter is positive going like the woofer and time aligned. It makes a difference. Maybe a kick drum is not the best example. Maybe a bongo or a rim shot is more appropriate when accompanied by a high frequency component with a sharp leading edge. In this case having a reverse polarity woofer does not sound as realistic.
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Do you mean changing the absolute polarity? Isn't it the topic here?
Yes, of course it is audible. For so many years I have observed the effect on the bass quality, but only since a few years ago I found that tweeters (dome in my case) were affected too.
I have found that some woofers were wired incorrectly (the plus/minus markings were wrong). Upon reversal of the wire terminals, one polarity produce better bass, so I used a battery and observed a positive DC sucked (instead of pushed) the cone, so I changed the marking.
1) OK, then first you would have to find a recording you were sure of the polarity of. Good luck with that.
2) If the recording was made with a dynamic (moving coil) microphone, a popular choice for recording, either polarity still results in a 90 degree change from the original source phase.
Picture a sine wave, start point “A” on the line, “B” above the line, “C” on the line again, “D” below the line, “E” back on the line.
----B
A____C_____E__
------------D
At maximum pressure “B”, the diaphragm is at rest, no velocity. As the pressure wave crosses “C”, the diaphragm and coil reach maximum velocity, hence maximum electrical amplitude, 90 degrees later.
If the recording was made with a condenser mic the phase response will (could) be accurate, but I have never noticed a polarity reversal on a single microphone to sound more or less accurate or realistic.
3)Smooth phase response does indeed make for better transient response, but correct absolute polarity does not affect the transient response.
4) A speaker with perfect step response would indeed reproduce a drum strike more accurately than one without, regardless of polarity.
5) Phase alignment certainly can make an audible difference, but can be achieved with different crossover types, which may or may not require reversal of polarity.
6)Kick drums are often recorded with a combination of moving coil and condenser microphones, so absolute polarity would be difficult to determine. Bongos are often recorded from underneath, typically with moving coil microphones, so review point #2. Snare drums are typically recorded with the top mic (also usually a moving coil mic) at nearly 90 degrees to the head.
Musical amplifiers are often polarity inverting, and vintage JBL speakers favored by many guitarists are opposite polarity from the usual convention.
The bottom line is pop recordings are such a mish mash of polarity that even if you could tell the difference in absolute polarity, you couldn't find an example of it other than a recording using just a single condenser microphone (non-existent in the pop world, and rare in the classical world) assuming it went through a non-inverting path all the way from console, processing, and the recording and playback devices.
Considering the source (recorded music) has no standards regarding absolute polarity, I can't believe that anyone could possibly tell the difference in reversing polarity on their speakers in a double blind test.
Art
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In my experience, crossover induced phase shifts are inaudible at frequencies 2000 hz or higher, but audible in the 200 hz range. I haven't tested the range between 200 and 2000, nor the range below 200.
I have performed 3 tests that support this conclusion:
1) I used DSP to correct the frequency and phase response of a 2-way bookshelf speaker (without extending the frequency response). In this case, the passive crossover (at 2Khz) resulted in a frequency response that was +/- 0.5 dB from 200 hz to 16,000 hz. I was able to ABX turning the correction FIR on and off. I couldn't tell the difference.
2) I induced the phase shift associated with LR2 and LR4 crossovers onto wav files. I did this for varying crossover frequencies. Using ABX (in Foobar) and listening with headphones, I was able to detect differences for 200 Hz xo (but not with a preference). At 2000 hz and above, I couldn't detect a difference.
3) I repeated test 2 with tower speakers, and observed the same result. 200 hz was identifiable, (again, no preference) and 2000 hz was not.
Maybe my ears just aren't as sensitive as some others. Certainly a measurement microphone can show the difference.
On the other hand, I completely ignore the testimony of anyone regarding this issue who hasn't performed ABX testing.
Is there a file sharing place where we can upload wav files with different phase characteristics?
If the file is less than 1.82MB (about 15 seconds of high res FLAC or 45 sec of 320kbit MP3) you can rename the file to .asc extension and upload here as attachment on DIYA thread. That's what I do for all my Subjective Blind Tests of full range drivers for folks to listen and compare. That way it is preserved in perpetuity (as long as DIYA is around and maintains their servers).
I believe I can hear wierd "phasiness" on my speakers up to 6kHz when too much steep PEQ's are applied. A blind virtual audition of phase effects would be most interesting. I can definitely hear non-flat phase non-transient perfect (LR2 symmetric) speakers vs quasi-transient speakers (Harsch XO). Perhaps I should make some blind test sound clips to demonstrate?
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Try it on two tower speakers that are phase coherent. To me, it's easy to get "wowed" for a few seconds, like could happen in ABX testing.
I've done my share of ABX in the past with headphones trying to decide which lossy codec to use in my Car. Lossless wasn't an option for USB devises.
But long term listening is what I base my preference on. Regarding things like balance and EQ curves. Headphones don't give me the pleasure I get from coherent towers that make me feel as much as hear the sound.
So I wouldn't discount ABX, but I don't want to rely on it either, long term pleasure in listening counts just as high for me. I've done a lot of testing on the subject of time coherency. Not to try and convince others, just to hear for myself. I'm sold. You guys figure out what you want to do. That doesn't matter to me. Trying is believing. Or not... your choice.
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