How Do Tiny Speakers Produce High-Quality Sound?

[anorlunda]

TL;DR Summary

How do tiny phones and bluetooth speakers produce such high quality and high volume sound?

Somebody please update me or provide a study link for modern sound technology.

I ask because I am looking at the tiny 1-2 mm hole in my phone where the sound comes out. Ditto for Bluetooth speakers that produce great sound quality and sound volume from a small box. In the hi-fi era, speakers were huge pieces of furniture.

I should clarify that my hearing cuts off at 3 kHz, so high quality sound to me may not be high to you.

How has the technology changed?

 

[marcusl]

I disagree that phones have “high quality sound.” To me they sound tinny and, at high volume, distorted. Still I get your point given how small they are.

 

[tech99]

They seem to have a wafer thin flat horn. You can buy these speakers very cheaply.

 

[JBA]

The above comments are interesting to me because I have hearing only below the 5 kHz level and, to me, my small cell phone has great sound quality and clarity regardless of the selected volume level.

 

[anorlunda]

The above comments are interesting to me because I have hearing only below the 5 kHz level and, to me, my small cell phone has great sound quality and clarity regardless of the selected volume level.

You have seen past threads on audio quality. When the audiophiles get started, consideration of hearing impaired people like us is quickly forgotten.

To be fair, few of them have heard the world through an impaired hearing filter. That's too bad, it should be a demonstration that is easily arranged. Perhaps there is an audiologist reading who can point us to recordings of such demonstrations.

 

[anorlunda]

They seem to have a wafer thin flat horn. You can buy these speakers very cheaply.

Is the answer no new technology other than miniaturization of a conventional speaker?

I guess you mean like this model available on alibaba for as little as 2 cents each.
I would have guessed that small size cuts off low frequency performance. For example, the speaker below says frequency range starts at 400 Hz, and its size starts at 10mm.

Rich sound Mylar speaker 20mm 25ohm 0.5W piezo tweeter speakers

2. Main feature of micro speaker:
-Size range from 10mm to 100mm in diameter;
-Wide frequency range (200Hz~20kHz);
-Rich sound reproduction;
-Paper or plastic cones, metal or plastic frames.
3. The main parameter values for micro Speaker, as follows:

1, Dimension (mm): various alternative sizes;
2, Impedance (ohm): 8~35 ohm;
3, Sensitivity(db): 85~100db;
4, Frequency Range (Hz): 400Hz-20kHz;
5, Rated power (mw): 3~5mw.

This image says it is the speaker from my S7 phone. It is not clear how many mm it is in size.

 

[NTL2009]

You have seen past threads on audio quality. When the audiophiles get started, consideration of hearing impaired people like us is quickly forgotten.

To be fair, few of them have heard the world through an impaired hearing filter. That's too bad, it should be a demonstration that is easily arranged. Perhaps there is an audiologist reading who can point us to recordings of such demonstrations.

My sympathies for having hearing that cuts off at 3 kHz, that really does reduce much of what we hear (consonants in speech for example).

Without needing to go into audiophile teritory, that really does change the context of "high quality sound". Even many of us old timers would consider a source that cuts off above 3 kHz to not be "high quality". I think it would be more helpful to re-phrase this as "How do modern small speakers manage to provide fairly low distortion sound in most of the bandwidth of speech, at the volume levels they do?" It would be far better to put some numbers to that, X db SPL at 1 meter at specific frequencies. Your phrasing is really open ended.

In general I agree though, that the sound from these small speakers has greatly improved in recent years. But there is simply no comparison to a hi-fidelity speakers that are furniture size. These phones do not put out anywhere near the SPL, especially in the bass area, say even 150 Hz, let alone 30 Hz. And anything even remotely considered "high-fidelity" will be able to produce significant SPL levels at 30 Hz, even if it is rolling off. That's not the snake-oil audiophile territory, ask any musician. And I'd bet the distortion in these phone speakers, while good, is no where near as low as a hi-fi speaker.

I'll try to find some sources, but my guess is (physics being what it is), that they have managed to increase the displacement (throw) of the diaphragm over a fairly linear range. A typical dynamic speaker looses linearity as the coil moves out of the magnetic field.

Oh, and anyone can easily experience sound cut off at 3 kHz. Just load a sound file into the free-ware program Audacity (or similar), and run a filter on it.

 

[anorlunda]

These phones do not put out anywhere near the SPL, especially in the bass area, say even 150 Hz, let alone 30 Hz.

Interesting. As I recall the plots of my own hearing tests, that low frequency region is not even tested. I can't be sure if I can hear (or have ever heard) 30 Hz.

I just ran an experiment with tone generator apps. On my phone, I can't hear any tone below 170 Hz, with full volume next to my ear. On my iPad, it was 130 Hz. But that doesn't tell me the difference between the device's low cutoff and my hearing's low cutoff.

But I and @JBA both like the sound quality from our phones. I listen to Ravel's Bolero on my phone all the time. Might praise for phone sound quality correlate with bad hearing? That would be interesting. Like asking color blind people to rate color paintings.

What do others say?

1. My hearing is good/bad.
2. I think phone sound quality is good/bad.

No intermediates please, just good/bad.

 

[JT Smith]

I'm not sure a poll is all that great a way to achieve a useful answer but...

1. My hearing is damaged in some way. There is clearly an asymmetry in my hearing. I have terrible discrimination when it comes to understanding speech with significant background noise. But a simple online tone generator, coupled with a decent pair of headphones, suggests that I can hear between 15 an 14,500 Hz. That's not too bad.

2. I think modern phones sound amazingly good, relatively speaking. Still kind of tinny though.

 

[cjl]

I just ran an experiment with tone generator apps. On my phone, I can't hear any tone below 170 Hz, with full volume next to my ear. On my iPad, it was 130 Hz. But that doesn't tell me the difference between the device's low cutoff and my hearing's low cutoff.

My guess is that that's the device, not your ear. Pretty much everyone can easily hear down to at least 50-60hz or so, even if they have relatively poor hearing, and the majority of people can hear down to more like 25hz or so (though producing sounds below 40-50hz with reasonably high volume and low distortion is not an easy task without large speakers)

 

[NTL2009]

Interesting. As I recall the plots of my own hearing tests, that low frequency region is not even tested. I can't be sure if I can hear (or have ever heard) 30 Hz. ...

I assume these plots were done by an audiologist? They would be focused mostly on your ability to understand speech, and understand-ability in speech is more in the band of:

from wiki - en.wikipedia.org/wiki/Voice_frequency

A voice frequency (VF) or voice band is one of the frequencies, within part of the audio range, that is being used for the transmission of speech.

In telephony, the usable voice frequency band ranges from approximately 300 Hz to 3400 Hz. It is for this reason that the ultra low frequency band of the electromagnetic spectrum between 300 and 3000 Hz is also referred to as voice frequency,

The voiced speech of a typical adult male will have a fundamental frequency from 85 to 180 Hz, and that of a typical adult female from 165 to 255 Hz.[1][2] Thus, the fundamental frequency of most speech falls below the bottom of the "voice frequency" band as defined above. However, enough of the harmonic series will be present for the missing fundamental to create the impression of hearing the fundamental tone.

On the low end, you don't even need to have hearing down below about 170 Hz (the 2nd harmonic of the lowest typical range of male voices) to understand speech. Many musicians will be aware of this phenomenon, you can eliminate or greatly attenuate the fundamental frequency of a musical note, but it will still be recognized as being the note name of the fundamental - the brain seems to fill in the missing fundamental as it just expects it with that harmonic series.

On the high end, you just keep missing more and more cues from consonants and other noises above ~ 4,000 Hz.

But music will have fundamental notes down in the 40 Hz range (Low E on the standard bass guitar is ~ 41.2 Hz), and percussion sounds can be lower. When listening over a small speaker, you'll mostly respond to the harmonics to identify those notes. The notes won't just be "missing" in the music.

But I and @JBA both like the sound quality from our phones. I listen to Ravel's Bolero on my phone all the time. Might praise for phone sound quality correlate with bad hearing? That would be interesting. Like asking color blind people to rate color paintings.

What do others say?

1. My hearing is good/bad.
2. I think phone sound quality is good/bad.

No intermediates please, just good/bad.

Not really a useful way to look at it. Good/bad is not only subjective, but requires context. A phone might have relatively "good" sound, but is awful compared to any half-way decent (not going anywhere near 'audiophile' standards) full sized speaker. The phone just cannot fill a room with low frequency sound.

You already know your hearing is compromised (on the high end). It's probably fine on the low end (but there are exceptions, a torn/scarred ear drum may attenuate the lower frequencies). But you would need to test your hearing with something that can output a decent level of low end sound. Most headphones/earbuds do pretty good. I'll run a test a little later.

 

[sysprog]

Interesting. As I recall the plots of my own hearing tests, that low frequency region is not even tested. I can't be sure if I can hear (or have ever heard) 30 Hz.

I just ran an experiment with tone generator apps. On my phone, I can't hear any tone below 170 Hz, with full volume next to my ear. On my iPad, it was 130 Hz. But that doesn't tell me the difference between the device's low cutoff and my hearing's low cutoff.

But I and @JBA both like the sound quality from our phones. I listen to Ravel's Bolero on my phone all the time. Might praise for phone sound quality correlate with bad hearing? That would be interesting. Like asking color blind people to rate color paintings.

What do others say?

1. My hearing is good/bad.
2. I think phone sound quality is good/bad.

No intermediates please, just good/bad.

My hearing is good.

I think my Samsung Galaxy S6 sound quality is good.
I think my HTC One M9 sound quality is good.
I think my LG V20 sound quality is good.

The LG V20 can produce much better sound when connected via its 3.5mm audio jack to an external sound device, because then its 'hi-fi quad DAC' is activatable. The internal speakers produce good quality sound but cannot produce adequate volume. If you push the volume with a booster app you get significant distortion.

 

[anorlunda]

If you push the volume with a booster app you get significant distortion.

I never heard of that. What is an example of a booster app?

 

[sysprog]

I never heard of that. What is an example of a booster app?

They are apps that increase the audio volume beyond the max that can be realized just by maxing the hardware volume control on your device. I think that in general they work by a combination of increase in input signal gain and increase in output signal amplitude. There are dozens of them: https://play.google.com/store/search?q=sound booster&c=apps&hl=en_US

 

[cjl]

The LG V20 can produce much better sound when connected via its 3.5mm audio jack to an external sound device, because then its 'hi-fi quad DAC' is activatable.

This is probably not the reason for the much higher quality. The real reason is simply speakers - feeding exactly the same fidelity of signal that the internal speakers get to a high quality external set of speakers will give you much better sound.

 

[sysprog]

This is probably not the reason for the much higher quality. The real reason is simply speakers - feeding exactly the same fidelity of signal that the internal speakers get to a high quality external set of speakers will give you much better sound.

Certainly the external speakers account for the improvement in volume without loss of sound quality, but when the device is connected to an external audio device, the 'hi-fi quad DAC' can be switched on and off, and when on, there is a noticeable improvement in sound quality. Here's a pre-release article on the LG V20 hi-fi quad DAC: https://www.androidauthority.com/lg-v20-quad-dac-explained-713587/

 

[cjl]

If you can hear a difference, one of a few things is happening:

1) The regular DAC is spectacularly, inexcusably bad
2) They're doing some kind of extra signal processing to make it sound "better" (very common with audio "improvements" like the "beats audio" available on a lot of laptops)
3) The output levels are different. Most people perceive slightly louder sound as better quality

It's trivially easy these days to make an absolutely audibly transparent dac, and once you're at that point, further "improvement" is completely inaudible.

 

[sysprog]

If you can hear a difference, one of a few things is happening:

1) The regular DAC is spectacularly, inexcusably bad
2) They're doing some kind of extra signal processing to make it sound "better" (very common with audio "improvements" like the "beats audio" available on a lot of laptops)
3) The output levels are different. Most people perceive slightly louder sound as better quality

It's trivially easy these days to make an absolutely audibly transparent dac, and once you're at that point, further "improvement" is completely inaudible.

I firmly disagree. Your highly superficial '1) 2) 3)' analysis is a false trichotomy. The 'none of the above' reply comes to mind.

The signals from each DAC path adds together but noise does not, resulting in higher signal with less increase in noise. Each doubling of converters results in half the decimation noise.
. . .
The Quad DAC’s low power mode shuts down three of the four DACs when they’re not needed, to increase battery life when playing lower quality audio or using lower quality headsets.

If you read, or even skim, the article to which I linked, I think you'll see that the dismissiveness you evinced is in this case not warranted.

 

[NTL2009]

I firmly disagree. Your highly superficial '1) 2) 3)' analysis is a false trichotomy. The 'none of the above' reply comes to mind.

If you read, or even skim, the article to which I linked, I think you'll see that the dismissiveness you evinced is in this case not warranted.

I remain somewhat skeptical as well. Though it is a matter of degrees. You said the difference was "noticeable". OK. But from what I gathered from the linked article, this can reduce noise/error (I'm pretty sure that most DAC error ends up presenting itself as noise, as the errors are fairly random).

So the context I'm looking for is, is the noise of current designs an issue for most listeners? I can understand wanting to reduce noise in a home listening room, a quiet environment and good equipment. But is this significant for the kind of listening the vast majority people do on their phones? Typically they have rather cheap ear buds in a noisy environment, and are just casually listening. So the difference may be noticeable to some in an A/B comparison, but I'm not sure very many people would notice or care, unless one or more of the other 3 items that @cjl listed were in place.

 

[sysprog]

I remain somewhat skeptical as well. Though it is a matter of degrees. You said the difference was "noticeable". OK. But from what I gathered from the linked article, this can reduce noise/error (I'm pretty sure that most DAC error ends up presenting itself as noise, as the errors are fairly random).

So the context I'm looking for is, is the noise of current designs an issue for most listeners? I can understand wanting to reduce noise in a home listening room, a quiet environment and good equipment. But is this significant for the kind of listening the vast majority people do on their phones? Typically they have rather cheap ear buds in a noisy environment, and are just casually listening. So the difference may be noticeable to some in an A/B comparison, but I'm not sure very many people would notice or care, unless one or more of the other 3 items that @cjl listed were in place.

I don't much care, in most situations, but I do find the difference to be noticeable. I can easily hear the noise difference (increase) when I plug the LG V20 into an Altec-Lansing M604 and switch the quad DAC from on to off. The difference between the quad mode and low-power (single DAC) mode is different from the difference between on and off (off causes the device to use the internal Snapdragon DAC instead), but it's still quite detectable -- I think that the LG V20 hi-fi quad DAC is not merely a gimmick.

 

[marcusl]

And now we’re back to the “audiophile” arguments that will go on forevermore.

 

[sysprog]

And now we’re back to the “audiophile” arguments that will go on forevermore.

What do you think about the sound quality of modern speakers that use neodymium magnets?

 

[NTL2009]

And now we’re back to the “audiophile” arguments that will go on forevermore.

Hardly.

@sysprog says he can hear the difference when plugged into an external speaker, and there appears to be some legitimate technical reason that can be attributed to a lower noise level. I'm oversimplifying, but if I followed, they seem to be averaging the outputs of several different DACs? If the noise/error of each is somewhat uncorrelated to the others, that should improve the S/N ratio, and that is most likely pretty easily measured with good equipment. Seems like that would be a small difference compared to a standard DAC, but it certainly could be noticeable with an external amp/speaker. That's a long way from some of the audiophile woo-woo we hear about, that has no basis in physics and no way to measure it (these cables make the sound more 'intimate' and 'alive'?).

 

[sysprog]

Hardly.

@sysprog says he can hear the difference when plugged into an external speaker, and there appears to be some legitimate technical reason that can be attributed to a lower noise level. I'm oversimplifying, but if I followed, they seem to be averaging the outputs of several different DACs? If the noise/error of each is somewhat uncorrelated to the others, that should improve the S/N ratio, and that is most likely pretty easily measured with good equipment. Seems like that would be a small difference compared to a standard DAC, but it certainly could be noticeable with an external amp/speaker. That's a long way from some of the audiophile woo-woo we hear about, that has no basis in physics and no way to measure it (these cables make the sound more 'intimate' and 'alive'?).

Well, ok, I agree that I'm not being a promulgator of "audiophile woo-woo". I acknowledge that the differences to which audiophiles pay attention may be negligible to many or most other listeners, but to use an analogy to oenophiles, if I can't tell, or don't care about, e.g., the difference between a common table claret and a St. Emilion Grand Cru Classe e.g. Chateau Cheval Blanc, why shouldn't I get just as merry off my $10 bottle as they do off their $700 bottle, and not begrudge them their indulgence in their expenditures on the rarities?

This thread is supposed to be about modern speaker technology -- I think that by reasonable extension, it can also be about modern audio signal technology, but I think it shouldn't be hijacked into being a soapbox for rants against audiophiles who are willing to pay high prices for pleasantnesses and acuities some of which arguably may not exist and some of which certainly their ears cannot hear.

So I re-pose my question, originally posed to @marcusl, to you, @NTL2009: what do you think about the newer speakers that use neodymium magnets? I think rare Earth magnets and mylar cones and high-precision tolerances in the manufacturing processes make for smaller speakers that are more robust and deliver great sound -- what do you think about those things?

Edit: my two favorite personally-owned pairs of speakers are: Celestion DL4 (bookshelf speakers -- reference monitor sound quality -- that can handle an electric guitar (Fender Starcaster) being played through them using a soft-clipping power amp from NAD driven by a Yamaha mixing board) and '70s Henry Kloss Advent -- old-school big cabinet hand-built -- maybe not the most accurate in terms of input-to-output spectrum match, but extremely precise and great-sounding and they move a lot of air to fill a room with first-rate sound.

 

[cjl]

I remain somewhat skeptical as well. Though it is a matter of degrees. You said the difference was "noticeable". OK. But from what I gathered from the linked article, this can reduce noise/error (I'm pretty sure that most DAC error ends up presenting itself as noise, as the errors are fairly random).

So the context I'm looking for is, is the noise of current designs an issue for most listeners? I can understand wanting to reduce noise in a home listening room, a quiet environment and good equipment. But is this significant for the kind of listening the vast majority people do on their phones? Typically they have rather cheap ear buds in a noisy environment, and are just casually listening. So the difference may be noticeable to some in an A/B comparison, but I'm not sure very many people would notice or care, unless one or more of the other 3 items that @cjl listed were in place.

I firmly disagree. Your highly superficial '1) 2) 3)' analysis is a false trichotomy. The 'none of the above' reply comes to mind.

If you read, or even skim, the article to which I linked, I think you'll see that the dismissiveness you evinced is in this case not warranted.

It's pretty easy to make a DAC these days with noise 100dB or more down from the signal. Better noise performance only matters if your reference design sucks in the first place. Assuming you're starting with a decent DAC, better noise performance will only help your spec sheet, and it won't be even slightly audible. If you can hear noise from the DAC under normal circumstances, that falls very clearly under option 1 that I had above: your baseline is spectacularly bad. This is certainly possible of course - many modern products have bad designs. However, you don't need "quad dac" designs to achieve inaudibly low noise.

EDIT: On the other hand, differences in speakers are very clearly audible. Among all of the things audiophiles focus on, speaker differences are the one where you should clearly focus the most, since that's where you'll get by far the best return.

 

[NTL2009]

...
So I re-pose my question, originally posed to @marcusl, to you, @NTL2009: what do you think about the newer speakers that use neodymium magnets? I think rare Earth magnets and mylar cones and high-precision tolerances in the manufacturing processes make for smaller speakers that are more robust and deliver great sound -- what do you think about those things? ...

I don't have any particular insight, but I think it is a very interesting question, and I hope someone with knowledge will come forward, or maybe one of us will find a good source on the matter (I'll be busy today, but maybe I'll find time later).

But I'll take a semi- educated stab at it, and I'd say it's been an evolution, not a revolution. I think most would agree that sound quality in these small devices has generally improved over the past decade. I'd attribute it to mostly small improvements in materials, design, and also more attention to detail,and consumer demand. Early on, people were satisfied with (edit: "amazed by") what a device could do. As time went on, those features became expected, so manufacturers needed to do other things to differentiate themselves, and one of those things was better sound quality.

Materials play a role, probably more computer modelling, and design-wise, I suspect they have been more clever in placing the speaker(s) and using the empty space in the device to provide a resonant cavity (like the box/port of a standard bookshelf speaker does).

 

[NTL2009]

It's pretty easy to make a DAC these days with noise 100dB or more down from the signal. Better noise performance only matters if your reference design sucks in the first place. Assuming you're starting with a decent DAC, better noise performance will only help your spec sheet, and it won't be even slightly audible. If you can hear noise from the DAC under normal circumstances, that falls very clearly under option 1 that I had above: your baseline is spectacularly bad. This is certainly possible of course - many modern products have bad designs. However, you don't need "quad dac" designs to achieve inaudibly low noise.

EDIT: On the other hand, differences in speakers are very clearly audible. Among all of the things audiophiles focus on, speaker differences are the one where you should clearly focus the most, since that's where you'll get by far the best return.

I'd agree with all that. But again, that's not contrary to @sysprog saying he can hear the difference, but I would tend to attribute it to a poor DAC in comparison, rather than this DAC being so superior. Maybe the multiple DACs are marketing hype, maybe it is a way to get better overall performance with lower overall power? I think the link said that some DACs could be shut down when you are in a 'non-Quad' mode? So maybe each single DAC is a low power design with higher noise/error as the trade-off, but by averaging 4 of them when desired, they can lower the noise level, and therefore balance noise/power on demand. That would also be consistent with observing that switching between the two modes is noticable.

I just tried an experiment with my good headphones, and my kinda-budget smart phone (Moto- G4, ~ $220 USD unlocked). Unfortunately, I have developed mild tinnitus over the past 4 years or so, so I really can't differentiate noise levels this low anymore anyhow . I would need some decent test equipment, or, if motivated enough, I suppose I could rig up my good-quality ADC (I use it for digitizing some of my old LPs), and use the freeware Audacity audio editing/analysis program to record the noise levels. If I boost the signals with a low noise amp, I might be able to measure differences. But with my tinnitus, I probably won't get that motivated.

I also used my good headphones and good DAC to test my hearing again. Sadly, it drops off by about 10 kHz, and is just gone by 12 kHz. I got similar results straight out of my laptop headphone jack with cheap earbuds, which tells me even budget components are actually pretty good these days.

 

[sysprog]

I think much of the sound quality advancement in small speaker tech used in phones and laptops has grown out of the steady work that's been done over the past decades on headphones.