Sound Advice

If you are serious about PC Audio, or are in the process of discovery. This page may offer some useful information.

HiFi and Computers don't mix !?
Influential sectors of the Audio Industry would have you believe this. The most powerful argument against PC Audio to date is ... MP3. Condescending the PC's image as a inferior sound source. MP3 has been used as a sword.

At the same time that MP3 started to gather momentum as a music lovers format. PC manufacturers began production of high quality Sound Cards with a Digital to Analogue Conversion (DAC) quality, outclassing their HiFi predecessors. i.e CD circuitry or stand alone HiFi Dac's. A higher quality PC DAC (Sound Card) could be purchased for considerably less money than a chunky HiFi counterpart.

So..the PC's hardware was certainly optimized for high quality Audio. MP3 was not however.

Today, with the media rich Internet and newer, more intelligent compression methods we can have our cake - and eat it. Below I outline some pointers for high quality Audio reproduction. Some important issues, some trivial. But mostly criteria overlooked by many of us.

Useful Things to know

The most common audio power rating is RMS. Some output equipment misleadingly claim fantastic power handling figures.
Make sure these figures are measured in RMS. The default standard.

One of the quickest ways to improve sound quality is to ditch those 'Multi Media' loudspeakers. Any amplifier with an auxiliary or CD input can be plugged in place of those plastic gadgets. If you are the proud owner of a basic 'SBLive' sound card you will be pleased to know it's Digital to Analogue Conversion quality betters HiFi equivalents priced over 4X higher. Combine the equipment - it's evolution! If you require replay at a better quality than CD, try one of the studio quality soundcards pioneered by Teratec or M-Audio. Costing about the same as an entry level CD player, 24bit soundcards really do deliver studio quality. Good quality Loudspeakers strive to correctly distribute power between cones. The balance of this neutral presentation and competent coverage of the frequency range will be impaired by certain criterior:

• At low volumes our perception of treble and bass is reduced. Due mainly to the non-linear way our ears respond. Middle frequency's i.e speech are not effected in the same way. It is now that EQ may be used as a psychological correction tool, correcting our own failings. However. The same setting will over amplify the level of certain bands when the master volume is increased. Distorting the signal. This places drive unit voice coils (loudspeaker cones) at risk of damage.

• A more common cause of Loudspeaker drive unit failure is amplifier clipping. Look at this wave form. If you were to turn up your amplifier you would expect a perfect signal thus. (I would anyway!...grin). If your amplifier were underpowered in relation to the task you set it - the voltage at output may be incapable of consistent form. A square wave is generated, a signal approaching DC current. -This will switch a 30w amplifier into a 60w amplifier. The conclusion: You have a better chance of damaging your loudspeakers with a lower rated amplifier than a higher rated one. So consider moving away from multimedia loudspeakers, if you have the space.

  

Linear Response is one of the aspirational fundamentals of audio design and setup. The ideal - to accurately reproduce every frequency at the same volume.
Within an ideal audio setup, frequency equalization should not be required. Unfortunately many obstacles present themselves during setup. Frequency equalization should only be used as a final option. If you are not experiencing a near linear response try these steps first:

• Positioning loudspeakers closer to walls reinforces bass response

• Keeping amplifier vents free from obstruction allows components to operate under the correct temperatures. A overall improvement in detail will shine through. Bass will be tighter, but the major improvement will be in mid range detail.

• Differing amplifiers will have contrasting tolerance of input volume. This is controllable by your sound card volume. (a tiny output voltage via your line out to exterior amp.). A over amplified signal for your particular amplifier input will result in a harsh, brash tone. Reducing the sound card volume allows ample headroom for your amplifier to dynamically reproduce peaks. This may also allow your amplifier to use more of its RMS. power without distortion. *(see -electromagnetic loudspeaker damping)

• Isolate your equipment from vibration.
  Components operating under excessive vibration from sound waves are far from optimized. Many products boast fantastic improvement of reproduction. However, for general isolation I recommend Poster Tack. Pliable, reusable and it actually works. Shelf loudspeakers - again, Poster Tack will allow the drive unit to project detail in contrast to distributing information through the cabinet and the surface beneath. For Floor standing loudspeaker's use a spiked wooden tray filled with sand and sit your loudspeaker on top. Isolation will show improvements near the upper midrange to high frequency's.

• Upgrade your loudspeaker cable.
  The simplest and cheapest upgrade to any system is to upgrade the Loudspeaker cable. Poor quality cable resists electron flow removing detail and power. High quality cable transmits audio information with less resistance. Think of the electrons as flat pebbles skimming across a lake. Poor cable is more like skimming into the sea, Some skim but some sink! Detail and power - lost in the cable. 100% Oxygen free (OFC) cable is an affordable option. Manufacture removes oxygen traces from the wire preventing oxidization - increasing electron efficiency over its surface, improving high frequency. Also a larger than normal diameter will actually reduce impedance - improving bass response.

• Electromagnetic loudspeaker damping generally refers to your amplifiers control over the loudspeaker drive units. As a conventional loudspeaker drive unit is essentially a piston, this movement must be controlled. Put simply - a more powerful amplifier will generate tighter electromagnetic damping over cone movement. Thus providing more reactive bass and control of frequency reproduction.

• Acoustic loudspeaker damping and loading.
  Conventional drive units produce sound waves from both sides of the cone. We normally 'load' the drive unit into a cabinet to suppress or utilize this second form of energy.

Infinite Baffle loading requires a cabinet that is completely air tight. The trapped air acting as a spring when the cone is moving. Compressing and expanding - allowing more amplifier power to be applied. Any air leaks will kill bass response with this type of loading - the drive unit not operating under optimum control. (flapping).
To cure this problem CAREFULLY remove the driver and apply silicone sealant to all internal joints. Allow time to set as certain solvents react with cone materials.

Reflex loading usually relies on the provision of a carefully tuned port to aid cone damping. The misconception that this port is there to 'blast bass' is not entirely true. The port acts as an air piston, resisting air release with certain signals but allowing the drive unit to reach deeper oscillations when required. Sometimes midrange can be soft and bass (although often deeper with comparatively priced systems) can seem out of control.
If your system suffers with this problem simply place a sock in the port. This will tighten up bass and offer greater damping of the cone for midrange control, also allowing slightly higher RMS. signals and subsequent Electromagnetic damping.

Cabinet resonance is completely unacceptable but a difficult area for audio designers. Manufacturers know that the solution is to construct bombproof cabinets - however, size constraints and shipping costs at multination level dictate workaround meatheads. Internal cross bracing of panels is often used to tighten the construction. With this problem the only solution is to either stiffen the cabinet yourself or remake a cabinet and export the electric's. Care must be taken to accurately match the internal cabinet volume/dimensions specific to unit properties. Because of the Electrical Crossover time alignment design relating to the position of drive units on the front baffle. e.g.. 3 way loudspeakers may fire drive units with millisecond delays according to driver parameters when loaded (in specific cabinet dimension's) and relative position to each other. - Drive unit position must stay the same. The design will then be optimized providing overall improvements. Thick medium destiny fiberboard offers the easiest solution.

Additional damping can also be found within systems. The dispersion or conversion of sound wave from the rear of the cone into non kinetic forms - with the addition of acoustic suppressing materials. (like deflex panels) will help to stop internal waves bouncing off the rear wall-coloring or effecting the pure signal output at the front. (standing waves). This is acoustic tuning of a cabinet relative to all its design property's. Deflecting the air vortex into strategic acoustic traps is one option. Care must be taken not to introduce flammable or conductive material near electrical circuitry. If you try any of the suggestions above be sure to follow the correct safety guidelines for your country.

Room acoustics. Contribute to audio performance considerably. The final 'room response' providing your ultimate measurement of system ability. One of the most important considerations within professional installations and public address, room acoustics are often ignored within our homes. System electroacoustic design is often custom tuned to room acoustics within professional circles, and for good reason. If you have ever moved house and switched on that 'old transistor radio' for company as you decorate, you may have been impressed at how 'listenable to' the music was. As your room takes shape and more furniture/wall coverings are added, your '3 mouse' power radio seems to loose its grunt. Soft furnishings and wall coverings absorb sound waves, Hard surfaces will reflect. Floor coverings and types differ. A room with raised floorboards will add to bass response, hard floors may require a bass heavy audio setup to present impact. Certain frequency's require a certain length of room in order to be perceived. Particular Bass oscillations can get trapped within a rooms acoustics if the wave is not allowed to reach its full length, making its reproduction at the drive cone pointless. Building styles and decoration differ throughout the world so I would advise experimentation. In certain circumstances sound waves are bounced- as loudspeakers are positioned towards a blank wall !

If after tweaking your setup you still find a non liner response - equalization or analogue/digital exciters can help to adjust your equipment's output, to reproduce music faithful to the engineer's intentions. The tweaking of equalization disregarding your audio setup may only serve to amplify or subdue the common fundamental fault of non linear response.

Transparency is the ability of your system to generate depth of sound. The feeling of being able to walk through the music. internal standing waves are a contributing factor to lack of transparency. The addition of acoustic damping materials to cabinets may help.

Soundstage is your systems ability to spread sound wide of loudspeaker enclosures. If your loudspeakers seem to be, -two sonically independent boxes and you can almost 'see' the sound emanating from them - You have bad soundstage. This problem is consistently relative but not exclusive to loudspeaker design, some of the suggestions on this page may help.

Transients are sounds that appear randomly within a recording. Output equipment is quite happy to blast any modern rhythms as the nature of electronics relies on electrical pulses, ideally suited to rhythm driven music. Where sounds appears at random within a rhythm, poor output equipment will choke to reproduce it. The best example to test competent transient handling is Jazz..

Imaging is the combination of Transparency,Soundstage and Transient handling. A 3D stereo image of a musical performance the goal.

Vocal projection and clarity is one of the more noticeable faults of any system. vocals can seem closed in or trapped within the loudspeaker enclosure. This is made worse by one of the most common equalization settings, (the smiley face):) - raising the bass and treble in order to achieve greater contrast between the frequency extremities. Infinite baffle enclosures can offer greater control, but this is a generalization.

Bass Agility refers to bass speed and depth. Many systems will try to force lower bass response providing perceived slam.
Music is composed of sound waves and thus loudspeakers move air with a piston action. The oscillation of air moved dictates the frequency. When a bass frequency is generated the loudspeaker cone moves a lot slower than at higher frequency's. The lower you go, more and more air has to be displaced. Small drive units simply have little impact. In order to move bass or sub frequency air, large diameter drive units are the preferred meathod. Small enclosed sub boxes will 'blow low' but the problem of speed is the next criterior.
Additional to efficient drive units, more powerful amplification will push and pull the cone oscillation with greater precision and agility. true depth and air slam generated.
For example. Night clubs with poor, slow bass may still have loud bass, but the effect may be more of a (whoop whoop) in contrast to King Kong playing the Bongo's ... quickly !!. Slow bass will also affect the detail of all frequency's. Smothering clarity as the bass response recedes in time as higher frequency's arrive at your ears promptly. This is why some loudspeaker systems employ fire time alignment within frequency dividing networks. Designed to work across dedicated drive units, bass units providing release fractionally sooner than the midrange and high frequency units. Your ears receiving all frequencies at the correct moment.

Headphones are a great alternative, often with better price/performance ratio. If you are prepared to stay close to your amplifier, headphones can be highly immersive. Essential for many professional situations of course. When trusting you ears to headphones, keep a sharp eye on the volume knob and buy from a respected name like Sennheiser.

Your ears are very important. As we get older we loose the ability to decipher high frequency's first. Upper Midrange quality becoming more important. Our new treble if you like! In time we may complain of a lack of melody in our music (I sound like your mum, don't I:) The sweet relation between treble and bass, so important to today's music could disappear for many of us as we get older. So here is a list explaining db(a) and when to leave the room.

Surround sound, formats and standards

Does 'surround sound' mean higher quality ?
No.
It is a case of Quality Vs Channels unfortunately (and always will be).
Surround sound systems offer more sound channels than stereo but no extra quality. Extra quality is often implied. Viewing a movie with surround sound can often be more of an experience than stereo but music brings its own rules. When setting a budget for audio reproduction go stereo! :) At ALL price levels you can achieve a more impressive performance by purchasing a better stereo setup compared to a comparative priced multichannel system. Ask any PA / DJ system installer if they insist on surround sound... Its a firm no.

Is Dolby 'Hi Fi' ?
No.
Dolby had great success in the 70's and 80's with a noise reduction system which they licensed to appear on compact cassette players. It is a misconception to believe that Dolby made recordings sound higher in fidelity as it worked by removing more data. The idea was that it removed the hiss from the low fidelity compact cassette tapes however it also tended to remove some of the recordings dynamic print. Dolby noise reduction systems spread quickly to most 'hifi' cassette players mainly aided by reasonable licensing costs.

Did Dolby invent 'multi channel' ?
No.
With the arrival of digital recordings Dolby moved closer to the cinema developing multichannel recording formats. Although multichannel was a very old idea, Dolby succeeded again by resurrecting multichannel using its by now strong brand name to promote the licensing of its logo and technology. Again it is a misconception to assume that a Dolby licensed product would provide better performance. As the variety of Dolby surround systems available simply provide a way to pack more data at reduced quality within the same space. Dolby surround systems are to be seen as a way of packaging audio data, not to be confused as a way of improving quality. DTS is a competing surround system that offers a slightly higher surround sound quality to Dolby.

Is THX better than Dolby ?
No. It is completely different.
THX has nothing to do with hiss removal or sound packaging.
THX is a standard that equipment and cinemas are required meet to gain the approval of THX.

DTS, Dolby Digital, SDDS, and hiss-reduction systems, such as Dolby A and Dolby SR form the first cinematic stage. Trying to improve the audio source. THX was developed in the early 80's to improve the second stage, the output equipment. The standard is mainly centred around build and especially good quality loudspeaker components. Tomlinson Holman and his team created the standard putting his name to the loudspeaker crossover ie. 'THX' So, THX is nothing more than a set of standards and a loudspeaker crossover??? ....erm.. yes. In recent years the THX badge has been branded/licensed within the consumer market... Unlike Dolby however THX should equate to higher quality replay.

Would Dolby,DTS or THX improve my MP3 playback ?
Dolby: no
DTS: no
THX: yes, maybe. THX certified PC's are available to buy but your own PC build standard or amplifier/loudspeaker quality may out class equipment that has pursued and gained a THX licence. It may be possible for example for an individual to apply for a THX badge if he thought his equipment surpassed the requirements set for THX. As with all standards a limit has to be set. I would argue that any individual could easily surpass what I see as moderate levels of High Fidelity.

Sound Links

If any of the above information has been of help to any one person, then writing this page has been worth the effort. I wish everyone involved with PC Audio the utmost musical enjoyment with the exciting advances upon us.

John Kirk is a design consultant to the traditional audio industry and advocate of PC Audio, Most recently developing a highly acclaimed 'Environmental Audio Extensions' studio mastering loudspeaker system.