This is why most live events play music in mono across all speakers, so that everyone hears the same music regardless of position be that a nightclub or a live concert.
You’re right - most venues do play music in dual mono (left and right speaker play the same thing). However, this maximizes the interference between the speakers. I’ve got a video with Dave Rat about this topic coming soon.
I've always found some of the effects of inverting only one speaker's phase in a stereo audio track when listening on monitors absolutely bizarre -- it sounds like something beyond what anyone should ever normally hear. Sometimes I think it would be cool to use it for effect in a mix but then I realise why people don't usually do that: on repeat exposure it can just be annoying
You're right! It's a very unnatural situation, if you think about it. The SAME signal coming from two sources is unnatural enough. Then you add in the EXACT OPPOSITE signal, and the whole stereo illusion falls apart. It has been used to "go beyond the boundaries of the speakers", but it's 100% mono incompatible.
@@AudioUniversity Yes indeed, and it's something about the human ear trying to make sense of signals that are defying how any sound signal normally reverberates/reflects in an acoustic space. It really enters the realm of 'audio illusion' and becomes so psychologically weird that it doesn't feel quite right for producing music
I agree. You can achieve a similar effect at some frequencies with time delay. One instrument (awesome for electric guitar), two copies hard panned left and right, one side delayed. This will comb filter when summed into mono, but has a widening effect.
I think it sounds good if you still pan two more guitar tracks left and right ontop of it fills in the middle without taking up room in the center where the vocals and snare are.
Nowhere in nature does a single thing make the same EXACT sound from more than one point in space. If I drop a nail on the ground, the sound that makes comes from one point in space. Something larger like a car may make sound from more than one point in space, such as the engine, the four wheels moving against the ground, etc. But those are actually MULTIPLE sound sources, despite being a part of the same object. THAT is one of the biggest challenges with reproduced audio if realism is desired.
It depends upon what you mean. While you're right about multiple sources of sound, all that matters for reproduction and listening is the sum total that is reaching any given point in space at a given time. So a binaural recording played back via intra-aural earphones will produce the same acoustic effect to the listener as it would if the listener were standing in the same spot that the recording was originally made (apart from small differences due to the difference between the shape of the binaural rig and the shape of one's own ears).
@@bricaaron3978In fairness, that assumes a mic with perfectly flat frequency response (or at least compensated) and an IEM that also has a perfectly neutral FR. Not to mention the fact that individual HRTFs vary significantly, so the difference between the artifical ears and the listener's will likely be quite significant. It also assumes that insertion depth resonances are controlled for, which is not something to take for granted.
I have a brown noise file that we play on a stereo Bluetooth speaker at night to help us sleep. While walking around the room, I noticed the phase interference in the last demo, so I created a new file with two channels instead of one and it completely fixed the problem. This was a few years ago now, but I'm still happy that I intuitively understood what was going on.
That’s brilliant! Respect. This is a principle called correlation”. I’ve got a video with L’Acoustics soon, where we discuss a modern solution for “decorrelation”. Stay tuned!
Thank god for this channel, I’ve learned so much watching these videos. And thanks to some connections my dad has im able to practice all of this stuff in a studio. Safe to say i have learned much more than my audio class in college!
Ha, when you inverted the tone I honestly thought the sound was coming from behind me. Then I realised it actually was, that is how Dolby Surround makes a basic surround channel from two channel audio! 😄
In the late 60's, my younger friend bought a used car stereo to put in the car his folks gave him for high school. Back then they didn't put stereo in from factory. He was showing me and had the two speakers ( outside the car) wired in direct series! Blew his mind when I wired them seperately with correct polarity. Guitars from different speaker than vocals. Imagine that!
One idea for live sound is separating sound into different speakers. The most wide spread practice is dividing it into frequency bands, Low, Mids, Highs, and sending them to Sub, woofer, Tweeter. The next step is to dividing based on sources starting with the subs, only sending what they need, that being Bass, Kick and sometimes Synths. Take that idea further and send the Vocals to their own set of speakers so there's more headroom per speaker and everything isn't competing on the same speaker cones. Similar to the old school guitar cabinets being the only speaker to project your sound leaving the PA for the vocalist. To go even further you get the grateful dead's wall of sound where each instrument had their own designed speaker array giving clarity and depth to the stage. Finally you go to before electrical powered sound was invented and you get an orchestra with each sound being made by an individual source and bouncing around in an acoustically designed chamber to add reverb and amplify the music. What this video shows is what happens when the same signal is sent to multiple speakers where as the more a signal is different the less this effects the experience.
2:07 when you did this test I was surprise complete cancellations of the bass thought a moment I have a sum sub so it was Electric sum😊 I’ve often out of Phase stereo speakers when they face each other and when they are 90*
Interesting! When the both channels had the same phase, it sounded as if the sound came from the center, but with and inverted phase, sound appeared to come from the sides
Good lessons. I am an olde school Sansui Quad enthusiast and have never stopped enjoying the Phase matrix options on my Sansui to convert Stereo into Surround sound (yes quad sound). When people accustom to their surround system listen to my Sansui sound systems I find that 40% enjoy the old Effects in the Sansui better than the surround Dolby. It depends on the source for me. Obviously movies come across better on my modern surround system. But most music sourced or streaming, whether surround encoded or not sounds more enjoyable on the Sansui.
This is exactly what I was looking to learn. I want to build a set of box speakers, acoustic. I have already made my sub woofer. I am always eager to learn more. Thanks so much!
We figured this out the hard way in the 80s by wiring subwoofers against each other. "Going Back to Cali" went from being one of the hardest hitting songs of all to having Less Than Zero bass. (See what I did there? 😁) I have a question regarding relative stuff: Why is it that a song like the above-mentioned will part your hair in the car with the signature "boom" of rap music but inside the house, when playing it in my wall-knocker stereo system, the boom is nonexistent? There's still bass, but the boom is not there. Another good example song for testing this is "The Last Rebel" by Lynyrd Skynyrd. It hits HARD in the car but you don't hear the boom at all on said wall-knocker. However, you DO hear the bass guitar & bass drum utilizing the latter. Thanks in advance! 👊🏻 🇺🇸
Hi, Your a real expert and you know very well what's going on. I had countless discussions in the past about the exact same thing and most of them was a fight against windmills. Speaker placement and even the positition of the chassis in their depht on the sound wall of the speakers are very difficult. In the transit frequency of the dividing network it's highly importent that they are very well alingned in their " sound center" of the membranes. Otherwise the speakers are producing the same problem by themselves.
Last example: - "Gosh, that sounds like flanging!". Listen and learn. When I was a trainee Telephone Exchange Technician in the early 70s I was allowed to spend an hour a day on work time to go through my printed training assignments. I was sent to the Power Room, where all the rectifiers converted the Mains 240V 50Hz AC to the Exchange's 50V DC. I enjoyed that big high-ceilinged room because if you walked around you could hear the (loud) 50Hz hum get louder and softer as you walked through the standing waves. You could also sing harmonies with the 50Hz and its overtones coming from those big rectifier cabinets. Amazingly, in those days smoking in there was allowed. :-)
I got dedicated mono system for old mono recordings, and i noticed that having only one good mono speaker in the corner of the room adds some clarity to the sound. And all instruments sounds more heavy!
Nothing much can beat a Tannoy concentric loudspeaker. The SGM series 10" is my fav. It is tight and fast. It stands out in my mind as visceral. Isn't this why we pay the big bucks to go to live concerts - it's those fast transients and body penetrating attack.
Of course things can change once you put the driver into a cabinet. The design of that cabinet is essential to how the sound travels and is shaped, and depending on whether the cab is a sealed unit or ported can have a physical effect on the movement of the cone, especially at high volume.
I remember the first time i tried this at home, was mind blown that adding a speaker and power could reduce the noise by cancellations, another reason why box design is very important, you dont want the rear wave of the speaker interaction negativeltyy with the front or the same effect will happen. Horn speaker and reflex speaker boxes use this to delay the rear wave so that it positively effects output at a specific frequency , when they combine after the delay (1/4 wave theory)
Intersting! But experiments like this needs an anechoic chamber (or at least a good studio/listening room that's close to anechoic - where all walls and ceiling are covered by sound absorbing material. A smaller sound aborber can then also be put under the speakers, to get rid of direct reflections from the floor). Then, the interference pattern should show up as a function of wavelength and distance to the speakers (like the classic double slit interference experiment) The interference pattern got pretty much random there because the room was an acoustic mess (I heard it just when you were talking, how much reflections there was), so reflections are coming from everywhere, interfering with each other and the direct sound in an uncontrolled way. But still cool. The white noise at the end really show how different frequencies are cancelled out and boosted differently.
At 2:03 I in fact heard a _much_ greater difference when listening just in front of (small poor-quality) speakers separated by ~24" than I did when listening on intra-aural earphones, which of course have as much separation as one can get. I was very surprised.
This is the real world quick test for making sure a source is phase aligned. In the real world, you will hear more cancellation in bass than in mids or highs. When they are in phase, the "body" comes back into the speakers (or stereo pair of mics).
When listening on speakers to the in phase portion, it sounds as if the sound is coming from the middle of my head. When they are out of phase I hear a sort of pseudo stereo sound as some frequencies seem to come from the left and others from the right. When wearing headphones, the effect was actually less pronounced as one might expect as there is almost no interaction with the sound waves before they hit the ears.
Opposite polarity sound seems to come either from under the desk or from behind. This was used in some computer music to inexpensively create a sense of space, and it was certain to be listened on stereo speakers. Vinyl rumble with opposite polarity sounds like wind blowing into one ear and out of the other.
Using the word phase would make sense here. As in, in-phase and out-of-phase. A home stereo two speaker system will lose it's punch and certain tonality if speakers are wired out-of-phase, as you say, work against each other. My girlfriend had her stereo speakers out-of-phase and I just flipped the polarity on one of them and the difference was dramatic when they pumped together.
WTF!? When the polarity in the first bit of music 2:25 is inverted, in my left ear I "hear it" in the middle of my ear and in my right ear I "hear it" in MY FUCKING EAR LOBE???????????????????
With multiple speakers, there is interference between the direct sound of each speaker. So it might sound great in the sweet spot, but not one step to the left or right.
I think we are close to understanding why two identical instruments that are very slightly out of tune will produce a wow wow sound as volume rises and falls from partial cancellation.
Yes! I need to make a video on this in the future. If you play two sine waves together (slightly different frequencies), they will totally cancel at a frequency that is proportional to the difference between the frequencies. It's actually very easily predictable: 1 Hz beat at 1 Hz difference, 2 Hz beat at 2 Hz difference, etc. So, 400 Hz and 401 Hz would cancel 1 time per second. 400 Hz and 402 Hz would cancel 2 times per second...
Hmmm this came up in my feed randomly and you helped me solve my problem with my truck audio system I didn’t even really realize I had 😂😂😂😂 my left front door speaker was inversed
2 Points he missed out: 1) The affect of phase change on speakers through crossover/network cards. 2) The phases of the freq for both speakers should not be different. So if I plug them both in the wrong direction (+ to - and vice versa) and they both are in the same phase, I would assume it to work fine. Many old speakers will come with wires coming out of the box, one of the 2 wire will be striped and you dont know if that striped wire should be negative or positive.
I have a Vizio SB3651 e6 sound bar Connected thru HDMI eARC & a XIBERIA 7.1 Surround head set. i could really hear the differance with the Phase Change in theVizio better than on the Head set. Go Figuer.
You know whats weird about mono is its completly in your head even though your right ear is completly isolated from your left (wearing headphones for example) you still hear mono. So if you had two armies moving identically making exactly the same noise from east and west would the ppl in the middle not know from which direction the armies are coming from?
A thing I've noticed with car audio systems is that, from the driver's seat the sound from the radio sounds like it's coming from the LF speaker in factory systems, but when you install an after market radio, the sound seems to be coming from the RF speaker. What's up with that?
some of the early releases of surround sound in the 70s and 80s, called quad amps, used signal inversion for the rear speakers. this tech gave a fooled dimension of sound.
There are 180 degree phase shift between two invert speakers. Human ears cannot hear the different sounds of those two speakers. Except for surrounding sound with larger delays from the phase shift. Surrounding sounds are the better for movies in theater. I prefer to hear the music with true sound but not surround sound.
So I have a question about guitar amps. If I have 2 guitar amps with 1 speaker each, but one is 12" and one is 10", will I get interference? My reasoning is that a different size speaker will have to move differently to create the same sound. So even if you start off in phase and play the same music eventually you will get to a point where there is negative interference! Am I correct?
Is it just me..?? I'm listening on a pair of headphones and when you invert one of the channels I can notice the bass sounding a bit deeper.. Please explain..
This principle applies all throughout an analog signal chain. So if you had accidentally wired one of your XLR cables between the mixer and the powered speaker backwards, you'll get the same effect.
Hey i hope you’ll see my message, i would like to have some insight on this, what makes a line array a line array? (Surely it is not just stacking point source speakers on top of each other) And is it possible to build one yourself? Hope someone will be able to answer. Thanks ya’ll
If you type "Line Array or Point-and-Shoot Speakers - JBL Professional" into your browser you will find a pdf explaining the concept. JBL also have an excellent book called "Audio Engineering for Sound Reinforcement" which has a chapter on line arrays. I spent 25 years working in a venue which changed to a line array 15 years ago. The difference was staggering due to some of the challenges we faced. They work as described. As a receiving house we also hosted many visiting line arrays, L-Acoustics, D&B Audiotechnik, Meyer etc. All of these are superb and no point source system ever came close in all sorts of ways.
I'm a autistic man I'm able to hear or perceive a noise frequency's overs can not around me, and it hurts my ears and makes me feel sick, I can hear it coming from a nabers house, and its turned on when I get home, they also vibrating the house like a heart beat, can I find out the frequency of the sound wave? can I then duplicate the sound wave to cancel it out? what would produce this kind of wave. Thank you
To determine the frequency or mix of frequencies we can normally hear we would use a spectrum analyser. You can get apps for phones/tablets and PC/MAC versions. These tools display a real time graph of loudness across the audio spectrum. You would simply look for the peak(s) and look at the x-axis to read the frequency or range of frequencies. However, we must consider that there could be unhelpful limitations when using spectrum analysis tools. The hardware and software may limit the frequency range of the tool which won't help if your troublesome noise is outside of that range. Remember though, if you are sensing something real it CAN be measured, you just need the correct measuring tools. I could speculate as to the possible causes but even that would require much more detail. Is this a low or high frequency sound? Or is it mixed? Is it continuous like a hum or intermittent like a drum beat? Is it a single tone which you could hum in tune to or is more like the wind or rushing water? Is the pitch and level altering over time or are these constant? Does it always happen at one period of the day or does it vary? Does it change with the seasons or is it the same all year? These are a few questions I would be asking myself to help narrow down the cause.
@andrewlefay2091 Hi thank you for replying, I think it's low frequency as its pentrating walls, it's hard to describe, it's on, off, siren like, it starts when I get home and the power of it is high, the power of it goes up when I go in the garden or clean my car, it's on all the time I'm home, the power goes up early in the morning ,2am 4am, 6am. There is also a vibration to, which comes on when I return home and goes off when I leave home, iv proven this with equipment iv hired and I have a machine recording a vibration and the pattern of the vibration is like a heart monitor, I can feel the house vibrating like a heart beat, this also on all the time just the power get turned up and down, high when I get home, high early hours 4am. I can hear and feel it coming from a house near me, but others can not, I have autism and ignored sensory difcultuys, I believe I'm being targeted. Thank you for your reply, if I manage to work out the frequency, could I cancel it out be sending the same frequency pattern in the direction of were I can hear it coming from, it hurts me like hell when i Power is high, I'm only able to cope by using medication. Thank you
@@Jasonnewlook In the video there is a demonstration of why this cancellation concept works on paper (2D space) but when we use real loudspeakers things get complicated (3D space). Therefore your suggestion of duplicating the signal to cancel the source won't work I'm afraid. I should make you aware that low frequency audio can deceive the ears and your noise may not even be coming from next door. A low frequency cyclic pattern as you described does sound mechanical like a train rolling along its tracks or trainers in a tumble dryer. I understand your feelings, my daughter is autistic and highly sensitive to certain stimuli. I tell her that her sensitivity isn't a problem, it's a superpower. Please ensure your doctor is made aware of this problem, your mental health is important. Stay well.
@@andrewlefay2091 Thank you for your help Andrew, have you heard of Mariana Alves-Pereira a scientist who has been researching the biological effects of infrasound and low frequency noise exposure, its very interesting, I wish there was a way for me to let others, experience what I can, it easy to understand something if you can experience it, may be one day doctor's will have a dives that will be able to experience a persons physical pain or semses. my GP is aware, but there is not much they can do. Thank you for your help Jason
In theory, yes. But this doesn't work in the real world. The most ideal speakers are coaxial or coincident designs. The only true point-source speakers you'll find that are full range, phase linear, with nearly flat FR, and can go as loud as you want are Danley Sound Labs designs.
Sometimes the science in fact can make quality of sound simply boring...The person can make a more colorful and enjoyable sound all together.... Digital sound is ugly compared to what is being left behind.... analog is colorful and beautiful....Same goes with light 🕯️🚨
Yeesh.... the demo at the end was fake. The idea you were presented does present that way under certain circumstances but man.... lying to people is not the way to present it. Also, you never really explained "the downside of multiple speakers in a sound system". Speakers that are well designed and properly integrated into a room with proper treatment will not present a downside.
It was the audio straight from the measurement mic! I’d recommend watching the next video on comb filtering. You can’t overcome the interactions between the speakers (discussed in this video) with acoustic treatment.
@@AudioUniversity no sir, I thoroughly understand. I work on systems design and integration for line-arrays. You stopped moving the mic stand at the end of the video but the comb-filtering continued to change as if you were still moving the mic.
