What makes low quality speakers become distorted when at high volume?

Question

Specifically speakers for tablets, phones, and laptops. I purchased a tablet in 2014, I got a tutorial on how to perform a modification of the system audio file which me very grateful when comparing the before and after maximum volume capability of my tablet.

It's good but obviously, it becomes quite distorted at about halfway. I've been told from professionals online that with the exception of Blu-ray sound systems, almost all speakers in gadgets sound bad. My friend £1200 Lenovo laptop seems to be the exception to that. When I was blasting music at high volume, it had maintained the 'clarity' that my good quality earphones have unlike my tablet which gets distorted.

I suppose that's what I'm getting to if you can understand. From my experience, low quality speakers make any music or voice sound 'muffled' at a high volume even with the audio itself being of high quality whereas good quality speakers sound as if 'the music is being next to you' along with hearing the clarity of individual instruments. Almost as if you're listening to music through earphones.

Is there a way to remedy this issue with my tablet through adjustments with an equalizer or do I need a DIY replacement of the speakers themselves?

Answer 1

There are a number of factors involved here but mainly frequency response, transient response, signal to noise ratio (S/N) and total harmonic distortion (THD).

Frequency response is largely dependent on the size, shape and mass of a speaker cone and there is no such thing as a speaker with perfect frequency response. But most significantly, the size of a speaker 'tunes' the frequency response of a speaker around a frequency band. This is why most speakers have more than one cone and a crossover to split the input signal and distribute it to the speaker that will reproduce it best. Usually tweeters for high, and speaker cones of varying sizes for the other (lower) frequencies. Laptop speakers usually have one speaker (cone) per channel which is 'pushed' hard to reproduce frequencies it really shouldn't so you can't expect a lot from them.

Transient response depends mainly on the amplifier used, as well as the mass of the speaker. Again, a lot of concessions are made to miniaturize these and fit them into a laptop.

Signal to noise ratio depends on the design of the whole system, even the cabling used and the PCB design. The motherboard of a laptop is a very (electromagnetically) noisy place but most signals are digital and not really affected by this but a digital signal has to be converted to analogue to be sent to the laptop speaker and from what I've seen in laptops I've opened up for repairs, all have single (unshielded) wires.

Total harmonic distortion is probably the most audible effect and is what happens when you're nearing a system's maximum limit. It is all about compromise here. It is a trade-off between having clear sound and having loud sound. Given the same amplification stage, a designer has to make a decision and that's usually done according to the consumer demand and the focusing to certain market. Very few laptops (if any) are focused to audio use and I'm pretty sure they would count on an external audio interface to do all the A/D and D/A conversion.

A way to remedy this would be to use an external sound system. There's nothing wrong with the analogue signal coming out of your laptop, tablet or phone audio out in terms of the factors mentioned above as long as it's for non-professional use.

If you're still not happy with the quality, you could also benefit from an external audio interface. Both tablets and laptops have USB ports so I would look at USB audio interfaces first.

Answer 2

Schizomorph makes a solid answer for all the technical details, but I'm going to break it down more basically.

• Sound consists of pressure changes.
• A speaker makes sound by moving a diaphragm that pushes air to make pressure changes.
• The volume of a sound is determined by how much air moves and how fast it moves.
• Small speakers can only move so much air. If you try to drive them too hard, it exceeds the range of motion of the diaphragm and it starts to distort as parts of the sound don't get reproduced because the speaker is stopped by its physical limitations.
• Larger speakers move more air and can generally produce loud sounds more easily.

Answer 3

Where as the other answers talk about technical measurements, they don't actual answer why sounds distort on speakers. This happens because of physical deformation of the cone, as well as travel limitations of the cone being reached.

Cheap speakers are made of thin cheap material like paper or thin plastic. When volume goes loud, the speakers move more vigorously, and the physical shape of the cone deforms, and this deformation is inherited by the resulting waves.

Also the current to the speaker could be driving the voice coil to the maximums of its throw, resulting on physical clipping of the sound wave.

More expensive speakers have much more rigid cones. They are made of more expensive material, and require more watts and larger magnets to move, since they usually weigh more as well. But the result is a cleaner sound at louder volumes.