Free System Design Service

The Confusion of Power

When it comes to discussing the power  output  of a distributed audio  system, it is  important to  understand what is being discussed. Is the question appropriate for answer the enquirer is asking for? For example: The Mini Cooper is  a  popular new  vehicle,   as is  the  new  Ford F-150 pick-up. Have  you ever  heard the topic  of payload mentioned when  discussing the  Mini? Conversely have you ever  heard of the topic  of handling being discussed when   talking  about  the  Ford?   And  it  would  be   very wrong  to  compare them  simple   by  quoting the  power output  of their motors.

When  the  topic  of power  and  distributed audio  comes up we also  need to look at this one  specification and  ask how  relevant it is?  Power  is not  a  good guide because too   many    other    factors   come   into   play.   This   is particularly the case when  comparing A-BUS against centrally  powered systems and  to quote its power  output as a quality  preference can  be  very misleading. So the question must be asked; ‘Should it be quoted at all?’

A-BUS was  developed to eliminate  the signal  losses that are   inherent  in  centrally  powered systems  and   these losses   are   not   just   output    power.    A-BUS  delivers cleaner, un-amplified signal  with no  losses, all the  way into the  individual  room  or zone  and  amplifies  it there. The right question to ask  is, “Which approach delivers a cleaner signal?”

 The Limitations of Speaker Cables

In the seventies when  we started experimenting with speaker cable we found  that  the  cable could  make  big differences in the  sonic  performance of a  Hi-Fi system. But despite what  we  heard with our  ears the  technical elite refused to accept the fact  that  it made a difference because they could  not measure these differences on a piece of paper. Magazines also  refused to review  them and  while a large  industry  grew  up making  speaker and interconnect cables, many,  most  of who were  technical, stuck  their head into the  ground and  ignored what  was obvious to the average listener.  Let’s face  it, our ears are the final judge.

With A-BUS it is no  different;  let your  ear  be  the  judge. While  all  the  skeptics want  to  argue about the  power output  of A-BUS, those using  it in the field are  having  no trouble.  It seems that  history  is repeating itself most  of the critics are  the ones that have  never  heard it for themselves. A-BUS sounds better and  it is not because of power. It’s because of delivery  of better quality signal to the local rooms  or zones.

The Historical View of Power

There  are  two  ways  of looking  at  the  power   question. One   is  from  a  historical  point  of  view.  The  other   is whether it is  appropriate to  use  the  power  output  of a system to judge the quality of a sound system.

In  the   1970’s   and   1980’s   many   speaker  designers traded speaker efficiency  to get  improved sound quality. Loudspeakers  were  being  designed  where   the previously  typical  90dB   efficiency  often  got  down   to 84db. Additionally, crossovers on some speakers that claimed a nominal  impedance of 8 ohms  magnified the problem by  going   down   to  impedances as low  as  2 ohms  at some frequencies. And what  might  seem like a simple solution to increase the power  output  of the amplifier  was  just  not  that  simple.   For  example, if  you have  a  50  watt  amplifier  rated at  8 ohms,  put  a  2-ohm load   on  it and   it will want  to  deliver   upwards of  200 watts.   The  problem is  it can’t  because the  amplifier’s power  supply was  only designed to deliver  50  watts  or there-about. But if the designer increased the size  of the power  supply, which  is quite  costly,  to handle a difficult 2 ohm  load,  it was  not expensive to increase the  power output  at the  same time. It is like a catch 22 puzzle the real reason for the  expansion of power  is rarely understood and  too difficult to explain  to the average consumer. Watts by themselves may not be  an accurate way to measure an amplifier’s quality but weighing it can be  a  good alternative. Good  power  supplies are  rarely light.

In the  1990’s  the  tables turned, speaker designers had to respond to the  limitations  of mass market  amplifiers that  could   not  deliver  the  flexibility they  required.  The average efficiency  of speakers has  come back up,  (ie. many  speakers are  now ported again and  floor standing speakers have  largely replaced boxed speakers on stands) and  impedance curves in general are  not so demanding. It’s a good thing,  because the weight  of amplifiers  has  not increased over  the  last  25 years and rather  than  putting  out 2x power  they are now putting  out 5x power.

What are the Parameters for Multi-Room Audio?

With multi-room audio we need to re-examine the parameters we are  working with and  their importance. Is power  really our problem? No, most  in wall speakers are around 90dB  efficient,  their  impedance curves are  not an area of concern and  they are generally 8ohms.

So  what  are   the  different  parameters  we  should  be looking at? Let’s go back to speaker cables a parameter that  many  so  often  ignore  but  one  that  has  a  lot more relevance when  it comes to distributed audio.  We are  no longer  talking about ten foot runs  and  very real problems start to come into play such as capacitance and inductance as we get  into longer  runs  around the home. You are  not  only increasing your  resistance in the  line, the  further  you go,  the  effectiveness of the  insulation  or isolation  between cores also  diminishes. So  the  power you  think you  start  with does not  necessarily go  down the   line   and   probably   more   importantly,   the   sound quality is irreparably diminished. And when  we consider that  most   homes are   being wired  with  no  more   than standard 16/4  we  are  really  consigning our  consumers to mediocrity at  best without a  remedy available. There are  other  parameters such as damping factor  which few people know about or understand, that become much more  relevant with long  cable runs  reducing the  quality of sound. (Damping factor controls the extended movement of the diaphragm to stop  it from acting like flabby spring.)

Once you  install  long  runs  of speaker cable in a  wall there   is  no  panacea, you  cannot correct what  is  lost going  down  the  line.  And  when  you  try to  counter the problem with better speakers then  there  is little that  can be  achieved because the  losses have  already occurred down  the  line. OK you can  install better speaker cables but   it   is   really   like   putting   a   band-aid   on   what   is essentially   a   festering   sore.  All   too   often   in   these situations  people  are  turning  the  volume  up  to compensate for the  lack  of clarity. The result  is irritating music  that no one  listens  to for long period and  after the newness wears off these systems are rarely used.

Why is A-BUS such a Great Solution?

If  you  understand  the  problems  the  speaker  cables present to a sound system whether they be  short  or long the  best  solution  is  to  get   the  amplifier  as close  as possible to the  speaker. Running  long  runs  of line level signal  offer little trouble  in comparison, here  our problem is mainly hum  and  noise. Category 5 cable offers  a real solution  here  as an audio  signal  places little demand on it in compared to the real purpose it was designed  for.

When you have  installed an A-BUS system and  tested it, you quickly  find it does not lack  power  either.  It is not a weakness of the system as there  is plenty  of good clean power   available  for  today’s  efficient  “In  Wall” loudspeakers. Is the  amount of volume  important in the bedroom  bathroom  or   kitchen?   In  most cases   the answer is no! The clarity of sound on the  other  hand is important. Around  the  home  you  are  looking to complement your activities, the  sound needs to be relaxing   and   entertaining  not  invasive   or  irritating.  So perhaps the  real  test  is  not  how  good the  sound is  at high volume it is how good the sound is at low volume.

However,  if you are  looking for high volume  outdoors, for instance, it is never  an  easy problem but  it is an  area where  A-BUS has  a  lot of advantages. With an  A-BUS pre-wire  we  are  sending a  high  quality  signal  to every room,  if  there   is  a  requirement for high  power   (a  kids rumpus room  could be  another example), A-BUS becomes the line level signal  source for a local amplifier. A-BUS power  modules can  also  work with sub-woofers to increase the dynamics of the music. But most importantly   wherever you  are   in  the  house the  signal source with A-BUS is at its best.

So, when  someone questions the power  output  of a distributed audio  system, think carefully  about why the question is  asked before you  respond with an  answer which  is really misleading. It is really better not to quote the output  at all.

Comments are closed.