Digital Sound FAQ

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[mikeer2002ph]

Have you ever wondered how sound is generated from your PC to your speakers?

This thread was set up exactly to answer lingering questions about sound coming from your computer (whether laptop or desktop) and its eventual passing to the speakers to which you hear sound

This thread will cover 4 topics in a nutshell so you can fully understand where problems lie if ever you do have sound problems on your desktop / laptop


Topics - Electronics 101, Digital Electronics 101, PC Audio 101, PC Speakers 101


Electronics 101

Before we go straight to the more advanced topics like digital electronics, audio and speakers, lets go to the basics.

Electronics refers to the flow of charge (moving electrons) through nonmetal conductors (mainly semiconductors), whereas electrical refers to the flow of charge through metal conductors. For example, flow of charge through silicon, which is not a metal, would come under electronics; whereas flow of charge through copper, which is a metal, would come under electrical. (http://en.wikipedia.org/wiki/Electronics)

Simply put, electronics is the study of how electricity flows from one point to the other in non-metal conductors (silicon to be exact)

The PC itself (either laptop / desktop) is one BIG electonic circuit and even the processor, if broken down into its basic parts, is basically just one big collection of transistors, capacitors and resistors (made of silicon) and electrons travel through them at the speed of light.

In the interest of the thread, we shall just limit the topic of electronics in the area of sound.

In electronics, sound is produced when the electrical signals are converted from signals or voltages, into sound. (We shall deal with sound later at PC Audio 101)

To simplify further, there are basic building blocks of producing sound you need to have 1. sound input, 2. sound processing and 3. sound output

1. Sound input = As the name implies, this is the source of the electical signals where sound is generated. As far as the computer is concerned there are several inputs:
inputs where sound can be generated or produced: mic (microphone), line-in (external sound devices such as MP3 players,CD players,etc.), hard drive (through MP3s,OGGs,WMAs, etc), optical drives (DVD/CD ROMs/Re-writable CDs)

2. Sound processing = Signals coming from the sound input sometimes are too weak and/or are inappropriate to be fed directly to the speakers by itself, therefore its processed by a sound processor or amplified with the use of amplifiers. The tone (the mixture of bass, midrange, treble) is also done at this stage to further 'enhance' the signal, Equalizers are basically sound processors in their own right because the 'flat' electrical signal get's enhanced with bass/midrange/treble controls which more 'precision' because you can shape the sound signal for every frequency range on the equalizer. sound processors include the ICH (integrated controller hub), HD Audio hub and audio codecs

3. Sound output = As the name implies, this is where sound is already 'processed' and is ready to be sent to the speakers, usually at line level signals/voltages. At this stage, the signals are strong enough to drive small speakers (your headphones/earphones are good examples of these speakers) and if you want further amplification to drive larger speakers, then you connect the sound output to another thing block called power amplifier (we'll also deal with external amplifiers later at PC speakers 101)

That closes our Electronics 101 topic.


Digital Electronics 101

In Electronics 101 we've learned that signals are inputed, then processed and outputted. But as far as the computer is concerned, it cannot understand normal sound signals (either from input,processing,output) because electronic signals are analog by nature.

All computers are digital by nature and ever wondered why its digital? It only deals with numbers, specifically just 2 numbers that are numerical equivalents of voltages. Its 1s and 0s

Binary (1s and 0s) are the only 2 numbers that a computer can understand, and electronically 1s represents a presence of voltage, 0s is absence of voltage

Since computers are also high speed switching devices (imagine 1s as switched on and 0's as switched off and this is happening at least a million cycles (Mhz) per second), it theoretically can represent the analog signal stream with a digital signal stream equivalent but the analog signals need to be 'converted' first from analog to digital for the computer to understand it.

This is where DACs and ADCs come in. DACs are Digital to Analog Converters, and ADCs are Analog to Digital Converters. DACs and ADCs are semiconductor devices that are good with one thing = converting digital to analog signals (DACs) and vice-versa (ADCs)

There are also times when you need to also process digital signals (MP3 sounds flat, MP3 is too soft / too loud, sound is encoded in Dolby AC3(dolby digital), or in DTS or a combination of these) and you need a DSP or a Digital Signal Processor which is good at processing digital signals.

Codecs (coder/decoder) usually is part of the DSP or handled by firmware in the DSP and is responsible for decoding / encoding encrypted digital streams (a good example of a coded digital stream is Dolby AC3 (Dolby Digital) DolbyES, DTS,DTS-ES, HDCD, SACD)

To make things simple: analog inputs (Mic / LineIn / AuxIn) need to be converted to digital in order for the computer to work on it, same is true if its a digital signal (MP3s,WMA,audio from a video file), it needs to be converted to analog before it can be passed to the speakers which are analog outputs, and true if you need to work on digital files (MP3s, WMAs) because you need to process these sounds via the DSP

That closes our Digital Electronics 101 topic.


PC Audio 101

Now that we've discussed Electronics 101 and Digital Electronics 101, we're ready to discuss PC Audio 101
We will be discussing audio in the context of PC (desktop/laptop) audio

Now that we know that audio is basically digital as far as the PC is concerned, its converted from analog to digital when recording from analog external sources (ADC), digital audio is processed and stored internally in the computer (DSP), and its converted from digital to analog as it is given out to the speakers (ADC).

Audio streams coming from the speakers are analog and its digital as far as the signal streams are processed inside the PC

Terms that we usually encounter with respect to sound (especially when buying external sound cards):

Signal to noise ratio (SNR or S/N R) usually expressed in decibels (dB)
Sampling rate (rate) usually expressed in kilohertz (KHz)
Resolution (Resolution) usually expressed in bits
Signal Gain (Gain) usually expressed in decibels (dB)
Total Harmonic Distortion (THD) usually expressed in percentage (%)
Noise floor (N) usually expressed in decibels (dB)

What do these all mean?

Lets break it down further

Earlier in electronics 101,we learn that there are 3 building blocks (input, processing, output) and these building blocks are needed for sound to be processed

In computers, since sound is inputted and converted to digital, its digitally manipulated, and sent out to the speakers in analog, obviously there are conversions going on from one state to another (analog to digital / digital to analog / digital processing)

Lets sum it all up and check where do these conversions happen:

analog input => ADC , DSP for processing, DAC for output to speakers or no conversion for output to digital
digital input => no conversion, DSP for processing, DAC for output to analog speakers/line out / headphones or no conversion for output to digital

analog inputs : mic (analog mic) ; line in ; aux; phone/modem

digital inputs: mic (digital mic array); optical; coaxial

analog outputs : headphone; line out; speaker channels (L&R,LFE&C,surround L&R,rear L&R)

digital outputs : USB/HDD/ DVD/CD(writer mode) ; optical ; coaxial


Now in a perfect world, the idea is that the analog signal or digital signal is reproduced (converted) or processed perfectly and its output given to the speakers, conversion and processing is perfect and we get perfect sound but that is not usually the case


In reality, problems with conversion and processing happens (ADC/DSP/DAC errors), and we're introduced to noise, interference, distortion or a combination of these 3, the PC (either laptop or desktop) are very 'noisy' places to process audio and this is where we encounter quality issues such as: Noise, Interference (EMI / RFI), Distortion


Noise = elements of sound that is unpleasant (usually heard as pops / scratches / hiss / buzz / hum / whine). Noise usually come from errors in conversion or processing and also from EMI / RFI

Interference = as the name implies, these are external factors that 'interfere' with the signal, as far as computers are concerned there are 2 = EMI and RFI

EMI = Electro-Magnetic Interference; EMI is introduced into sound usually as a buzzing or humming sound and the main source of EMI is the PSU (Power Supply Unit of the PC), VRMs (voltage regulator modules) on the mobo that regulate voltage for the processor, memory, northbridge / southbridge, Casing / PSU Fans

RFI = Radio-Frequency Interference; RFI is introduced into sound usually as very high pitched whine / hiss and the main source of RFI is the processor, memory, motherboard

Distortion = elements of sound that is unpleasant (usually crackling 'crumbly' sound) and usually is present because of recording errors (gain is setup too high), high volume is overloading the output circuits 'clipping' the signal and it sounds 'distorted'

Engineers have devised ways and means to minimize effects of Noise, Interference (EMI/RFI) on sound through good design of the mobo, design of the circuitry where EMI and RFI is highest and making sure the sensitive audio part is as far away as possible and shielding the audio circuitry but of course, not everything is equal from mobo to mobo

Distortion is a subjective concern since sometimes, distortion is already part of the original content (for badly ripped MP3s for example) and is just being 'magnified' by the audio system of your PC.


Now Lets discuss the terms above:

Signal to noise ratio = ratio or difference of the good signal while being in a noisy environment. Obviously the higher the difference, the better the signal 'sounds' is because if it were equal or less than the noisy environment, then you'd only hear noise and not much of the sound you intend to hear (to compare: an old sound card (from the early 1990s) with a 70dB signal to noise ratio is the bare minimum set by microsoft in the early 90s for sound, now even the cheapest mobo has an audio card capable of giving out 95dB signal to noise ratio, and some special sound cards can have at least a signal to noise ratio of 115-120dB)

Sampling rate = rate by which the signal is sampled or taken (converted or processed or stored) by the system, the higher the sampling rate, the higher the quality of sound because the gradients of the digital signal is smoother as compared to a lower sampling rate where the digital signal appears jagged, therefore more prone to distortion (to compare: CD audio has 44.1KHz, MP3s have 22KHz-96Khz, DVD-audio has 48KHz, Multi-Track (5.1/6.1/7.1) sound usually has 192KHz sampling)

Resolution = the width of the signal stream, same with sampling rate = the higher the resolution, the better the quality (to compare: CD Audio just has 16 bits, MP3s have 16-24 (depends on the quality setting of the MP3), DVD-audio has 24 bits, multi-track sound (5.1/6.1/7.1) have 24 bits)

Signal Gain = is also known as signal strength (sometimes confused with signal to noise ratio but this is different), the higher the signal strength, the louder the sound is,but usually is automatically adjusted by the audio codec to normal (standard) levels ; too much signal gain is also unpleasant because if the signal gain is too high, it overloads the output circuit which introduces distortion in the signal (heard as crackling/crumbly sound)

Total Harmonic Distortion = distortion being introduced by the sound conversion/processing chips INCLUSIVE of the distortion already present in the signal = obviously the lower the better. Our ears (without any hearing problems) can perceive up to 0.1%THD. typical mobo audio cards have 0.02% THD, with better cards having lower THD

Noise floor = as the name implies, its the measurement of the noise present in the signal path (either digital or analog signals, or the combination of both). Measurements on or below the noisefloor are certain to be excluded, and signals that appear above the noise floor are the 'legitimate' signals and are fed to the DSP for further processing. One way that sound engineers worked around the noisy environment of the PC is to lower the noise floor (in effect raising the signal to noise ratio) by boosting the sound signals (inclusive of the noise) and filtering out the noise with the use of a DSP.


Onboard or offboard audio?

There are 2 movements (more like groups) that are in constant debate on whether the audio circuitry found on most motherboards is good enough, or an offboard (expansion / external card) sound card sounds better
well from an engineering point of view, it depends

If you have or bought a cheap motherboard, obviously the manufacturer cut corners, and puts the cheapest components to save on costs (hence its cheap) inclusive of the audio circuitry and would barely pass standards set by microsoft and computer industry standards

The computer industry have a more 'laxed' audio standards as compared to audiophile/broadcasting standards that are very stiff and strict when it comes to audio standards, alas, motheboard audio obviously belongs to the former.

But premium motherboards (obviously they're expensive) on the otherhand have very good onboard audio (and sometimes have the same components (DSPs,Codecs,ADCs,DACs) used in expensive offboard/expansion slot cards) that makes buying a separate sound card a redunant endeavor.

The best way to answer this debate = Follow your ears. In the end, your ears are the best audio instrument that can measure whether onboard sound or offboard sound is better

This concludes the PC Audio 101 topic

please continue reading at the succeeding post (PC speakers 101)

sources for all 4 topics: Wikipedia, Audiophile magazines, Stereophile.com, Microsoft.com, Intel.com, Texas Instruments (ti.com), Cirrus Logic (cirrus.com), howstuffworks.com, wharfedale.co.uk, mission.co.uk, bowers-wilkins.com, What!HiFi magazines and http://whathifi.com

[mikeer2002ph]

.. Continuation from above ..

PC Speakers 101

For PC speakers, this is a subjective matter since even if we all have ears, listening and hearing faculties, the way we perceive sound varies from person to person.

"What makes a good hi-fi loudspeaker? Well although opinions vary, Peter Walker - the founder of our sister company Quad, summed it up very nicely when he said you should get out exactly what you put in." (www.wharfedale.co.uk)

Again, basing on experience with Broadcasting, Audiophile (entry to high end), DJ (Home to Professional), and Computer audio (entry to high end), even if audio standards exist in every industry, alas, broadcasting standards are the 'standards' being strived to be achieved by the audiophile, DJ and computer audio industry

To set the tone of the topic on PC speakers lets put things in historical perspective.

There isn't ANY audio standard as far as PC speaker is concerned, PC speaker manufacturers merely copied of concepts and technology derived from historically 'stable' audio standards (mainly from the broadcasting and audiophile industry) and applied them on PC speakers, or evolved from early PC speaker models.

Speakers as far as the PC is concerned, is an afterthought, or mainly used for diagnostics (beep codes / buzz codes are the only function of speakers in early computer systems) until Creative Technology revolutionized the PC audio industry with the first sound blaster external card in the late 1980s (yes, motherboards then didnt have onboard audio then, a speaker connected to the mobo is simply meant for beep codes = error codes for diagnostic purposes)

The stir that creative created was the launch of the PC from a mere work/computing device to its new role = a multimedia machine, and the the multimedia age was born (multimedia = sights (computer graphics / video) and sounds) (http://en.wikipedia.org/wiki/Sound_Blaster)

But that is the birth and evolution of the sound card, PC speakers meant for audio are still nonexistent then, and if they were, they were in the stone age compared to the technology behind the PC itself (http://en.wikipedia.org/wiki/PC_speaker)

During the time when the soundblaster and a host of other cards went mainstream and met commercial success, PC manufacturers were the first one to market speakers made from nothing more than glorified TV speakers (because they were magnetically shielded) a very desirable speaker because they prevented magnetic anomalies from developing if placed close to the CRT monitor.

These speakers were good with voice, MIDI sounds and game effects but lacked basic audiophile sound qualities until the speaker manufacturers also wanted a piece of the lucrative PC market and began selling their idea of a 'proper' PC speaker some with success (example: Creative's partnership with Cambridge soundworks and Altec-Lansing (which was actually a dying audiophile speaker brand (related to the lansing brothers that originally founded JBL) until the PC multimedia frenzy resuscitated it, and placed them back in the audiophile roadmap)

Of course, the other audiophile speaker (and PC) manufacturers moved in after seeing initial success of these brands (Bose, Acoustic Energy, Logitech, Boston Acoustics, Mission, B&W) but because of the unique needs of the PC speaker (primarily dialog and in game sound effects) most audiophile speaker manufacturers dropped out and went back to their respective markets which was mainly to sell audiophile speakers to the audiophile market. In the audiophile circles, PC speakers are the example of sound qualities to be avoided in an audiophile setup (uncontrolled bass, lots of treble and piercing treble) which in turn is the selling point of PC speakers for games and for dialogue (synthesized voice or voice from teleconferencing)

Event up to now, speakers meant for the PC (even the flagship multimedia speakers meant for the PC) are mostly less than par compared to budget audiophile setups


Why?


Aside from the unique requirements of the PC speaker, This has something to do with the PC speaker meant as an 'accessory' rather than the object of being (to wit: in the broadcasting industry, speakers are designed and tuned to bring the studio sound experience to the closer to the masses ; for the audiophile industry, the speakers are designed and tuned to bring the concert hall or the solo artist in front center of the listener ; for PC speakers = for mere dialog (VOIP applications) and sound effects of games)

Since the PC speakers are mere 'accessories', and for the PC speakers to become more 'sellable', manufacturers decided to only concentrate on the teleconferencing/gaming experience as far as PC speakers are concerned, hence the experience with music and movies on the PC are still missing in the formula (in an average middle class household, movies are watched still on plain old fashioned separate home theatre systems (big screen TV/LCD/Projector/Plasma) or on dedicated separate stereo equipment(for stereo music)).

If the manufacturers do succeed in introducing audiophile/videophile technology to the PC speakers (like how some big speaker companies have in recent time - Bose, Polk, Acoustic Energy, Mission, B&W), the price of the PC speaker systems by itself is astronomical that it will even surpass the price of the PC itself (which is also true with speaker systems found in budget audiophile / videophile equipment) and this would obviously drive the prospective PC speaker buyers to purchase budget audiophile speakers instead and route the PC signal to a typical A/V(audio/video) or stereo amplifier and get better results because again, it just sounds better.

To wit: the most expensive commonly used 5.1 PC speaker system to date is the Logitech Z5500 (flagship model with T.H.X. certification) which is more expensive than an average desktop PC, sounds almost too good to be true but when compared to a typical budget audiophile quality 5.1 speaker system from Wharfedale, you'd hear the stark difference and that is when reality bites.

Again, as they say, even amongst audiophiles and videophiles, these are all just opinions and subjective remarks. The best audio equipment one has is his/her hearing and experience with how music sounds on different places and different genres. Your ears are still the judge, your experience the jury, and your wallet the executioner.(http://www.bowers-wilkins.com/display.aspx?infid=763)



How do speakers work?

Lets start with the basics before we deal with more 'deep' stuff

Speakers work by translating or converting electrical signals (again, going back to electronics 101, difference between electrical and electronics) into mechanical movement; this mechanical movement displaces free air as vibrations and this vibrations when heard from the ear is what we hear as sound. (in our ears (middle ear if im not mistaken), a membrane is attuned to pick up vibrations in the air and this is how our brain processes the vibration as sound)

Vibration varies by time = and is expressed in Hertz (Hz). The lower the vibration, the lower the frequency, the higher the vibration, the higher the frequency
Hertz (Hz) can also be expressed in thousands (KHz) , or millions (MHz) or billions (GHz) , which coincidentally, is also pegged to the speed of the computer/processor (but that off topic! back to speakers)

In a perfect world, a perfect speaker is just 1 per channel, radiating ALL the frequency of the audible spectrum (an average human ear with normal hearing can hear low vibrations of 20Hz up to the high vibrations of 20KHz)

But as we very well know, real life is less than perfect and even with 21st century technology, only tiny speakers (earphones/headphones are actually speakers in their right) have been able to do that

As for larger speakers, it needs to be broken down into speakers specializing in certain frequencies or vibrations in order to sound good

There are several types of speakers used in the PC as far as frequency delivery is concerned:

full range : a speaker that delivers ALL the frequencies (20Hz-20Khz) (similar to how earphones/headphones work)
woofer : a speaker that just delivers the low frequencies (20Hz-1KHz)
tweeter :a speaker that just delivers the high frequencies (1Khz-20KHz)
midrange : a speaker that just delivers the middle frequencies (900Hz-2KHz)
subwoofer : a speaker that just delivers really low frequencies (10-100Hz)
supertweeter: a speaker that just delivers really high frequencies (18Khz and beyond)


There are several ways that speakers can be bundled together to deliver the frequency response desired (which forms speaker systems)

1 way = a single full range speaker
2 way = a speaker with a woofer and tweeter
3 way = a speaker with a woofer, midrange, tweeter
4 way = a speaker with a woofer, midrange, tweeter, super tweeter

subwoofers are considered separate entities and are added to a speaker system to provide low frequency 'kick', when woofers are still not enough


which leads us to:


Types of speaker systems according to size

small bookshelf = also known as mini-monitors (when used in the studio) ; a small woofer (3-4 inches) and a small tweeter, in a small enclosure that represents a complete standalone system when used in stereo ; usually use a  pedestal to raise the speakers to ear level

bookshelf = also known as standard monitors (when used in the studio) ; larger than a small bookshelf, has a larger woofer (5-6 in) , a larger tweeter, and a larger enclosure. Its the standard bearer for stereo listening ; usually use a pedestal to raise the speakers to ear level

big bookshelf = also known as mini-floorstanders (because of its size) ; the largest of the bookshelf speakers (you need a very sturdy or wide bookself for this), has a large woofer (7-8in), a tweeter, and for some systems, a midrange. because of its size, its also hard to use normal pedestals used in typical small bookshelf/bookshelf speakers. usually speakers of this size is placed on a low platform for the speakers to reach ear level

floorstanding = the largest of the speaker systems, can be from 3 feet tall (standard ear level when sitting down) to as high as the ceiling (10-12 feet high in some custom installations) and can have a large woofer or several small woofers and tweeters and midranges. On some floor standing speakers, the speakers are even wired differently depending on the location of the speaker in relation to the enclosure=the bass woofer is the one at the bottom, the mid bass is at the bottom middle, the midrange is at the middle, a tweeter at the middle top, and a super tweeter at the topmost


Still, speakers (whether audiophile, broadcasting, DJ, PC) still adhere to standards to wit: (And this is also a good way to jumpstart your knowledge in buying speakers for your stereo / home theatre)

Frequency Response: expressed in (X)Hz to (X)Khz
Impedance: expressed in (X)ohms
Sensitivity:expressed in dB/W (decibel per watt)
Input Wattage: expressed in (X)watts - (X)watts
Crossover frequency: expressed in Hz


What are those?

Frequency response: usually denoted from (X)low (where Xlow is the lowest frequency that can be measured from the woofer or subwoofer (if part of the system)) and (X)high is the highest frequency that can be measured from the tweeter) and expressed in Hz - KHz (note: the human threshold of hearing for low frequency is an average of 20Hz, and the threshold of hearing for high frequency is an average of 20KHz) example .. mini bookshelfs usually have a frequency response of 70 to 80Hz to 20-24KHz

Impedance: average resistance of of the speaker systems expressed in ohms (impedance as far as the speakers are concerned are now electrical instead of electronic in nature since speakers are just basically a wound of wire tied up to a cone or dome of relative density and hardness) (http://en.wikipedia.org/wiki/Electrical_impedance)

To simplify: the higher the impedance, the easier it is to drive the speaker (by the amp), the lower the impedance, the harder the amp works to drive speakers.


Sensitivity: This is the measure in decibels per watt (dB/watt) obviously, the more sensitive the speaker, the louder it sounds at a given wattage

To simplify: for example if you audition a speaker with 88dB/watt as compared to a speaker with 91dB/watt (at the same volume level on the amp/or at the same wattage), the 91dB/watt speaker will sound twice as loud as the one with 88dB/watt (decibel ratings are logarithmic, the perception of sound doubles for every 3dB increments)


Input wattage: just like any electrical appliance, speakers are rated in watts, and its safe to say that you should only use an amp that is within the input wattage of the speakers, or safer if you use a larger amp (with more wattage) as compared to a smaller amp and just use caution not to overdrive the speakers.

to simplify: you can use a 40 watt amp to drive an 80watt speaker, but if the speakers are not sensitive then it will sound soft or you need to max out the amp in order to fully appreciate your speaker, but in doing so, you also raise the problem of clipping the amp ; better to use a larger amp with (100-150W) so you can max out the 80W speaker system, but just be careful not to max out the amp because in doing so, you destroy your speakers because it cannot handle the wattage of the amp


what is clipping? - as the term itself, the amp 'clips' or cuts the signal, so instead of hearing music, you just hear distortion from the speakers.

Is clipping harmful? - YES! Because when clipping happens, high frequencies is the first thing to get clipped hence the tweeters are the first to get damaged. (when clipping happens, DC voltage from the amp gets substituted instead of the musical signal, and since tweeters are the smallest speakers in the speaker system, and tweeters have the finest (really fine) wire wound, its easily damaged by a clipping amp.



crossover frequency: as the term implies, its the frequency where the crossover happens (handover from the woofer to the tweeter, or the handover from the subwoofer, to the woofer , to the midrange, to the tweeter, to the supertweeter)

to simplify: if you have a 2 way system, you have a single cross over frequency (usually at 2.5KHz or 3.3KHz) it means that at 2.5Khz or at 3.3KHz, the woofer hands over the signal to the tweeter

for 3 way systems (woofer,midrange,tweeter) .. there are 2 crossover frequencies (one crossover from the woofer to the midrange, one crossover from the midrange to the tweeter)

for 4 way systems (woofer,midrange,tweeter, super tweeter) there are 3 crossover frequencies (one crossover from the woofer to the midrange, one crossover for the midrange to the tweeter, one crossover from the tweeter to the supertweeter)

for subwoofers, there's also 1 crossover frequency (usually adjustable with a rotating switch) to which the subwoofer hands over the signal to the woofer on the separate speaker system

for subwoofers - if you 'overlap' the subwoofer crossover frequency too much, then you get 'boomy' bass because same bass frequencies are both being generated by the speaker system AND by the subwoofer. The reverse is also true, if you do not configure your subwoofer to the correct frequency, there is a bass frequency 'gap' because the bass frequency being handled by the subwoofer gets cut off at the wrong frequency (crossover frequency), the smooth transition gets lost , because the bass frequency generated by the woofer on the speaker system is not low enough to compensate.

Thats the reason why subwoofers have selectable or adjustable crossover so you can 'adjust' the crossover so the transition from the subwoofer on a separate enclosure to the woofer on the speaker system becomes 'seamless'

this concludes our digital FAQs.

any questions?

sources for all 4 topics: Wikipedia, Audiophile magazines, Stereophile.com, Microsoft.com, Intel.com, Texas Instruments (ti.com), Cirrus Logic (cirrus.com), howstuffworks.com, wharfedale.co.uk, mission.co.uk, bowers-wilkins.com, What!HiFi magazines and http://whathifi.com

[mikeer2002ph]

Additional information

PC speakers appear in multiple forms

current offerings
2.0 - Stereo Speakers without subwoofer
2.1 - Stereo Speakers with subwoofer
5.1 - 5 channel theatre sound (front L&R, center, rear L&R) with subwoofer
7.1 - 7 channel theatre sound (front L&R, center, rear L&R, surround L&R) with subwoofer
some even have T.H.X. certification from T.H.X. labs (special mention: Logitech Z5500, Z5400)

old (legacy) offerings (appeared during the early 1990s; special mention: Altec Lansing ADA 305 and ADA 310)
3.1 - Dolby Pro Logic sound (Front L&R, Virtual Center and Surround L&R) with subwoofer
4.1 - Dolby Digital sound (Front L&R, Center, Virtual Surround L&R) with subwoofer

[darkangel]

Wow!! very nice explanation you got there bro mikeer2002ph!! I've been looking and reading this topic 3 times, and anticipating the continuation- itching myself to comment.    .

Didn't know that pc speakers are quite inferior to standard audio systems. I thought they're on par, until now. And that's the reason i still love the music and audio on my mini component system though its not even mainstream. (using sony 5.1 component system) Glad that you give your time in explaining this complicated subject in simpler terms that helps us understand. I've always wondered before why a DTS 5.1 DVD sounded very nice compare to ordinary movies and audio cds. now i know that's the sampling rate that made the difference and the surround sound generated by the 6 speakers.

Thank you very much bro! 

[mikeer2002ph]

Thanks Darkangel! 

Well its a start of a 'continuous explanation' actually, that initial post of mine just sets the tone of the discussion afterwards.


Now, since you've posted your reply, let me answer your post point by point.


1. "Didn't know that pc speakers are quite inferior to standard audio systems. I thought they're on par, until now." (Darkangel, 2008)

Well the answer to that is .. it depends on who's standards are you referring to.

If you are referring to sonic standards of audio systems consisting of speaker systems and amps being sold in divisoria / quiapo / raon / or those that cost less a grand in malls, well PC speakers from logitech/altec lansing of a similar rank will sound better (at least di tunog lata)

To be technical about it, PC speakers is no different from speakers used in karaoke machines, they sound nice if used in the right application. (voice, musical effects and the typical MIDI sounds of karaoke)

BUT, if you compare them to budget audiophile 5.1 setups (even the cheapest 5.1 speakers from wharfedale and a low end 5.1 receiver from onkyo) then the argument is moot = the 5.1 speakers from wharfedales and the onkyo receiver win (even if they're the cheapest)

To be fair, there are speakers designed for the PC that are 'almost' audiophile quality, then again at the price you're paying for them, and for the compromise of only being used on the PC, you're better off with a separate audiophile speaker and amp, with much more flexibility.



2. "And that's the reason i still love the music and audio on my mini component system though its not even mainstream. (using sony 5.1 component system)" (Darkangel,2008)

Well speakers from the mini-components, even if the speakers themselves are still considered 'generic' (lets face it, the speakers from sony also came from someone else, since sony doesnt manufacture speakers anymore since the early 1990s) it is sonically capable because it was DESIGNED, MATCHED, AUDITIONED with MUSIC in mind, which is NOT the forte of PC speakers to begin with

PC speakers' forte is voice (for YM/Teleconferencing/VOIP) and game effects (boom-tizz effects of explosions, guns, roaring engines) as explained earlier.

If the sound frequency can be 'seen' (using an oscilloscope) speakers of PC systems are mostly in the low-middle part, leaving tight bass and sharp treble behind because again voice frequencies and the effects are all in the midrange frequency.

If you reverse the setup (use audiophile speakers and an AV receiver for VOIP and game effects) it would sound really soft and you have to turn up the volume really high just to hear the voice and effects.



3. "Glad that you give your time in explaining this complicated subject in simpler terms that helps us understand."

I've been observing how a lot of people here and in another site giving 'reviews','opinions' and 'suggestions' ASSUMING everyone knows or is on the same page.

ASSUME = makes an ASS out of U and ME

Hence, I'd prefer set the tone by explainging stuff, then answer the questions later so the questions would at least be framed within the thought that the initial post was read thoroughly even before the follow up question gets asked.

Usually, it happens that someone who just got interested in the topic gets 'lost in translation' and asks questions that have already been previously answered in the post or were not framed properly hence the thread gets out of hand



4. "I've always wondered before why a DTS 5.1 DVD sounded very nice compare to ordinary movies and audio cds." (Darkangel, 2008)

DTS is a newer audio standard as compared to Dolby Digital (AC3). Both are still compressed (unline PCM which is raw data) But what differs DTS from Dolby Digital are:

a. DTS has a higher bit rate. More bits = more quality (less interpolation, leading to lesser noise or 'muddled' sound).

Downside to DTS is you need to have a faster decoder / DSP which was EXPENSIVE then, but they're dime a dozen now (applying moore's law in semiconductors and processing power)

b. Moreover, with DTS, the 6 channels of sound have separate channels instead of being multiplexed.

Dolby Digital = 2 channel digital sound, if the sound track requires more than 2 channels, the other extra channels are multiplexed within the 2 channel soundtrack

DTS = each channel of the soundtrack has its own space (channel)

Multiplexing: mixing different signals into one stream or one path

With Dolby Digital, in order to be compatible with stereo only inputs (for legacy equipment), all the 6 channels are crammed in the 2 (left and right) channels.

The firmware/software/DSP decodes which segment of the stream goes to which channel which obviously brings again interpolation errors and with errors, come noise.

There's obviously better clarity/resolution when the signals are separate rather than multiplexed. The downside to it, DTS audio tracks are relatively LARGER than Dolby Digital (AC3) but since the DVD's can handle the extra capacity, this is not an issue (im referring to genuine DVDs, not the pirated ones)



5. "Now i know that's the sampling rate that made the difference and the surround sound generated by the 6 speakers." (Darkangel, 2008)

Well sampling rate is just half the battle, because Dolby Digital aside from 44.1KHz sampling/16 bit rate, it also has 48KHz/16 bit sampling.

What makes DTS unique aside from a higher bit rate 48KHz/24 bits , 96KHz/24 bits , 192KHz/24 bits is the separate channels for each individual sound tracks


sources : http://en.wikipedia.org/wiki/Dolby_Digital, http://en.wikipedia.org/wiki/DTS_(sound_system)

[darkangel]

thanks for the additional & better clarification bro!!

Well, I'm just actually comparing the sound of Edifier X600, a pc speaker which i think is designed for gaming, and with a sony mini component system designed for music and movies. Naturally the sony will have better audio quality because it was "DESIGNED, MATCHED, AUDITIONED with MUSIC in mind" though using generic speakers. thanks for making that clear.

On the 3rd of your post, you mentioned "T.H.X. certification from T.H.X." Could you elaborate on this? and how does this new sound standard compare to others, like DTS and Dolby Digital (AC3)? and how common are hard wares that are capable to take advantage of this sound format?

[mikeer2002ph]

Thanks Dark! here's a reply to your queries


While DTS (Digital Theatre System), Dolby Digital, SDDS (Sony Dynamic Digital System) are recording protocols or standards by which movie soundtracks are encoded on the actual film (used in the cinema projector) or on DVDs/BDs that requires codecs (either in firmware/DSP/software), T.H.X is more of a quality assurance standard.

T.H.X. stands for Tomlinson Holman's eXperiment (Tomlinson Holman is a sound engineer at Lucas Films)

T.H.X. was primarily designed by Lucas Films, so that cinemas or home theatres or speakers that are certified will produce the experience of movie soundtracks (from Lucas Films obviously) as close as possible to the experience and intentions of the sound engineers at the studio, irrelevant of the venue and source of the movie (film for cinemas, DVD/BD for 'Separates' home theatre / PC Home Theatre)

T.H.X. is more of an acoustics / sonics / theatre quality assurance certification. Its a sound standard that encompasses how a speaker system / home theatre / movie house should sound in order to get 'certified'.

Again the whole objective of T.H.X certification is the person watching the movie / film at home or in the cinema should be able to experience the same sound intensity and quality as the engineers who mixed it, and the directors, sound/film critics that listened to it at the studio.

T.H.X. doesnt dictate the type (analog or digital) and protocol (Dolby (SR, Ultra Stereo, Digital), DTS, SDDS) but dictates the overall quality of sound heard from the interaction of the listening room (venue) and the speakers .

It doesnt matter if the source or encoding type is analog (Dolby SR, Ultra Stereo) or Digital (Dolby Digital, DTS, SDDS), but what matters is the quality of the 'output' coming from the speakers, how the speakers interact with the cinema surfaces (walls), how the speakers 'sound' once you hear it while sitting on the couch.

"T.H.X. also provides certified theaters with a special crossover circuit whose use is part of the standard. Certification of an auditorium entails specific acoustic and other technical requirements; architectural requirements include a floating floor, baffled and acoustically treated walls, no parallel walls (to reduce standing waves), a perforated screen (to allow center channel continuity), and NC30 rating for background noise."

Now I have to further classify the venues as far as T.H.X. is concerned

Cinemas
Separates Home Theatre (high end, middle range, budget)
Home Theatre in a Box
PC Home Theatre (HTPC or a gaming rig)

Cinemas (Inclusive of IMAX) - the first place to audition how T.H.X. sounds like. If you are able to watch a T.H.X. certified movie (most likely its a Lucas Film Feature like Star Wars) the experience from one T.H.X certified moviehouse (for example in Greenbelt 3 or Glorietta 4) will sound the same in another T.H.X certified moviehouse (Rockwell, Alabang Town Center, SM MOA and SM IMAX)

Separate Home theatre system - T.H.X. certification in home theatres is a mixed variety, because obviously, you dont just buy the actual hardware (T.H.X. Certified Amps, Receivers, Speakers, DVD/BD players) but also the venue itself is part of the certification (a dedicated 'viewing room' or 'film or movie den') which actually costs more to build and certify (the part of the house where you plan to set up the home theatre) because it has to follow strict design / sonic guidelines of T.H.X. AND you have to pay the representative company (through its sound engineer) to have the room 'certified'. So obviously, certification of a spare room in an old house is much more expensive as compared to designing the home theatre room while its still in the blueprint/design stage because the T.H.X. standard is already part of the house. (old houses are hard and more expensive to certify because one of the requirements of T.H.X. is no parallel walls, so a typical room in an old house will need to be renovated, floorings and cielings need to be taken out which will affect the floor below and above it.


1. T.H.X. applications in a high end setup (T.H.X. Equipment: Speakers and Amp and a T.H.X Certified room)

I've been given the opportunity to hear such a room somewhere inside ayala alabang (The house is newly built, the home theatre room was designed from the ground up to be T.H.X. certified and there's even a certificate of T.H.X seal of approval on the door leading to the film room. The experience is the SAME as being in a cinema (either in alabang town or in rockwell) except that there are fewer seats, you get to sit on the carpet if you want, and you can drink all the alcoholic beverages you want (I just had red wine, dad had johnny blue) which I think you cant do in any cinema anywhere in the Philippines. Of course this is a high end setup in a premiere gated village and a new house (home owners with very deep pockets)


2. T.H.X Applications in a middle range setup (T.H.X. Equipment: Speakers and Amp)

The next best thing is hearing it in a typical middle class environment (usually the living room is the home theater room) wherein you have a typical room (square or rectangle), and you have T.H.X. certified equipment (still quite expensive, but not as expensive as the room plus equipment) it sounds a bit boomy and the treble is quite sharp (because of the room interaction, which can be lessened by carpeting, curtains or wall decor)


3. T.H.X. Applications in a budget separate range setup (T.H.X. Equipment: Amp only or Speakers only)

As the name implies, T.H.X standards here are quite diluted since only the amp or the speakers are certified, you get the experience of T.H.X., but some sonic qualities gets 'lost' because either the speakers dont mesh well with the amp, or vice versa, but this is the typical arrangement in an ordinary home theatre setup


4. T.H.X. Applications in a budget all in one setup (T.H.X. Equipment: HTIB - Home Theatre in a Box)

Then if you're on a budget, and you only have a condo to spare, there are T.H.X. certified HTIBs (Home Theatre In a Box) that comes with satellite speakers (with a big subwoofer), AV receiver, cabling and setup instructions on how to set it up (in one BIG box).
Its tuned for small spaces like condo flats or single bedroom apartments. You might get knocking neighbors/next door flat owners because of the boom or the tizz effects.


5. T.H.X Applications for PCs (T.H.X. Equipment: T.H.X. certified PC Multimedia speakers (basically considered an all in one) and/or T.H.X. certified sound card)

lets face it, its the 21st century. Huge LCD TVs are still expensive, yet same or even larger LCD panels for PC desktops have arrived and the laptops that are coming out have also huge LCD screens to boot. People on the go or have limited budget have used their PCs/Laptops as the new venue in watching movies (including me)

Then when all else fails or the above T.H.X. setups are still expensive, then your next option is to get T.H.X. certified sound card and a T.H.X. certified multimedia speakers (only for gaming, still leaves a bit of wanting for audio/music) which is either the Logitech Z5500 or the Z5400

The last line of T.H.X. experience (through the headphones) is by getting a Sound Blaster XFi (sound card for desktops or PCMCIA card laptops) and just use competent audiophile headphones (Sennheiser HD280 or HD 215 or AKG 271 / AKG 55 ; Sennheiser HD650 is the best sounding headphones for T.H.X. but at its price (24K as of the last time i've checked) instead of buying this high-end headphone, you're better off with the Logitech Z-5500 (15K) and have money to spare for the XFi sound card

Again, best instrument here is to use your ears and balance it to your wallet.

Sources: wikipedia.org t.hx.com (just remove the period after the t in the t.h.x. website .. i hate the auto filter)

[mikeer2002ph]

<update>

I've setup a simple but audiophile quality 2.0 stereo sound here at home (separates components)

for those who wants to listen or wants to appreciate how stereo is supposed to sound like, give me a PM or YM so i can accomodate you.

pics of my stereo setup

Digital Sound FAQ

Left Speaker

Digital Sound FAQ

Right Speaker

Digital Sound FAQ

DVD Player , CD Player, Stereo Receiver

Digital Sound FAQ

Technical Specifications:

Amp/Receiver: Harman/Kardon HK3470 Stereo Receiver with VMAX
CD Player/MP3 Player : Harman/Kardon DVD21 with Wolfson DACs
DVD Player / Karaoke : Pioneer DV-595K with Burr-Brown DACs
Speaker Pair : Acoustic-Energy Aegis Evo 1 (British - Studio Monitor - Bookshelf)

[raw_knee]

Great topic! 

Can we discuss the difference between the PMPO (peak music power output) and RMS (root mean square) ratings of the speaker systems?

I think there was a time when you can see home stereo systems boasting of "10000W PMPO" -- the higher the number the louder they are (as the advertising during the day says).

Lately there was a shift to using the RMS rating which, according to some, is a better indicator of how powerful a speaker system is.

[mikeer2002ph]

Great topic! 

Can we discuss the difference between the PMPO (peak music power output) and RMS (root mean square) ratings of the speaker systems?

I think there was a time when you can see home stereo systems boasting of "10000W PMPO" -- the higher the number the louder they are (as the advertising during the day says).

Lately there was a shift to using the RMS rating which, according to some, is a better indicator of how powerful a speaker system is.

PMPO or peak music power output is just that - peak music power

PMPO as far as engineering is concerned, is just the maximum power the amp is capable of, in very short (or to be technical about it, in 2-3ms) time, without affecting the amp and the speakers

PMPO is not the continuous or constant power that an amp or speaker is capable of delivering indefinitely

RMS IS the measure of continuous or constant power that and amp or speaker is capable of performing

Obviously, PMPO has a larger number , therefore as far as marketing is concerned, its the 'eye candy' that unsuspecting customers see and obviously a lot of customers get hooked on.

PMPO usually is measured at a single frequency (usually at 1KHz) at very bad distortion levels (10-20% THD) for 1-10 ms (obviously the longer the time the amp stays in that peak music power, the more likely it gets destroyed in the process) hence the usual measurement is 2-3ms

What does this mean?

Nothing! - because obviously you wont be able to hear even a tone of music from 2-3 ms time.

RMS on the otherhand is more demanding to an amp or speakers BECAUSE of its nature that the amp / speaker is supposed to endure such power indefinitely.

PMPO is usually marketed for budget electronics (usually midi/mini/micro) systems while RMS is more used in audiophile quality (usually better build) amps and speaker systems

For example:

a typical karaoke machine with a 5000W PMPO amp / speaker when disassembled is merely a 20-30w RMS amp with a 50W speaker system but with the use of a tone generator (set at 1KHz), at 10-20% THD, and at just less than 10milliseconds, one can drive the system to such high numbers (and you dont hear anything at all because the speakers takes approximately 20-30 milliseconds to react)

whereas a typical 40w RMS audiophile amp sounds louder because obviously it has more power over the 20-30w RMS karaoke machine even if coupled to the same 50 speaker system.

PMPO is fair game to all electronics manufacturers whereas RMS is standardized by EIAJ/JEITA, FTC, DIN

so how do you know what is the RMS power of your amp? .. its usually on the manual under technical specifications

take note also of these facts

linear/analog electronics (to where amplifiers belong) usually have an efficiency rating of 50-60% ... therefore you have a rough estimate of how much your amp works by the way it consumes power from the wall outlet

obviously, you cannot expect 5000W of power to be produced by the amp or by the speaker if its only consuming 100-150W of power from the outlet. (you are also violating the laws of physics - conservation of matter and energy)

case point: I have a stereo amp that consumes roughly 500W which is fair enough because it delivers 130W+130W (260W total) RMS (FTC) of power to the speakers. to translate it, 50% of the power consumption is fed to the amp and produces sound given to the speakers)

therefore RMS power is the better indicator of how an amp performs at a certain impedance (resistance) at a certain frequency range and at a certain distortion level (THD)

another tip on how to check for how your amp is built = how heavy it is ..

an amp's weight is mostly on the power transformer and on the heatsink (for the power transistors or power pack ICs)

of course, higher power ratings means larger heatsinks, larger transformers and larger components therefore heavier or bulkier builds

Its common for stereo midi/mini/micro component sound system to have PMPO of 5000-10000W but in reality have 20-30W RMS or the higher end sound systems have 45-50W RMS and if one notices, its weight is really light (even with the speakers included), whereas audiophile amps with 50-70 RMS are heavy, with some amps requiring 2 people to carry it because of the weight (usually amps at the 100-150 RMS per channel rating)

[bOgszY]

TFS!

[mikeer2002ph]

TFS!

you're most welcome bogszy! mwah mwah!

[dhiching03]

kelangan ba sa ganito maganda rin ang speaker? or puwede na kahit yung kasama sa package kapag bumili ng dvd player or yung basta may kasamang speaker.

[mikeer2002ph]

kelangan ba sa ganito maganda rin ang speaker? or puwede na kahit yung kasama sa package kapag bumili ng dvd player or yung basta may kasamang speaker.

Thanks dhiching03,

Well, to answer the question - it really depends on your audio taste and/or budget.

I have to admit, I started off with DIY (do it yourself) speakers and speaker cabinets (bought in raon in quiapo) and it grew from there.

I also started off with listening to LPs (long playing) records when i was a kid, played on turntables on really big wooden furniture that is supposed to be the amp and speaker (tube type) and also listening to piano / organ recitals and live opera when i was a kid (my mom's mom was an opera singer although she only sung in a private audience)

Fast forward to the 21st century.

There are DVD players nowadays with speakers systems or HTIB (home theatre in a box) which have speakers already included.

Again ... your ears and wallet are the judge.

If your ears are revolting on what you hear and your wallet approves of a little spending, then get better speakers / better amps

If you dont have the budget or you're fine with what you hear, then why reinvent the wheel or fix something that isnt broken to begin with?

The tip here is listening and hearing a lot of content from a lot of places (concerts , musicals , recitals, conciertos, opera, movie watching in different cinemas, listening to music at different places so you get familiar to how music / movies / conciertos are supposed to sound like.

THEN thats the time you can compare it to what you hear at home.


For me, there's another approach:

Listening to stereo music (when you close your eyes) you are supposed to 'see' and 'hear' the singer in front of you or singing in front of you.

The speakers 'disappear' and the instruments sound alive and seem to have its place in space while you're eyes are closed.. If you dont hear the speakers disappear or the singer is all around the place, then there is something wrong with the speaker or with the amp or both

[dhiching03]

haha..noob question..ang purpose lang ba ng amplifier ay pampalakas ng sound?.