This article outlines some basic factors which can influence the sound of your system, sometimes quite dramatically, and offers some advice and suggestions for tweaking accordingly. The potential benefits in doing so are not limited to top end equipment and can have an audible
effect on entry and mid level components.
However, it is assumed that you are using reasonable quality interconnects and that your equipment is connected to a common, reasonably good quality power source. This last point is actually quite important and maybe we shall look at this in another article some time.
We are of course referring to AC mains power polarity as connected to individual system components. When there are polarity variances
between components within an overall system, this can have a detrimental quality on the resultant sound. Specifically, in imaging, solidity and
clarity. Let's set up our system properly by working through the following tasks. First of all, disconnect all components from each other and from
the power source.
This is a good opportunity to inspect and clean all the contacts of your power connections and also the component interconnects. Now connect your speakers to the amplifier (assuming an integrated - if not see note at the end of this section) and connect the amplifier to the power source using the conventional polarity settings for live and neutral connections. If your power connector is 2 pole (as opposed to 3), mark one side of the connection accordingly. Place your speakers in a close position equi-distant from your listening position or, if available, connect a good quality pair of headphones.
Now, connect the first source component, such as your CD player for example (assumes integrated transport / DAC). Play a good quality CD with a distinct acoustic. A live choral work, opera or jazz ensemble would be a good choice. Listen attentively both to the individual sounds
and their placement within the overall acoustic space.
Now, reverse the polarity of the mains power connector and listen to the same piece again. There WILL be a difference. One connection will provide an enhanced imaging of individual instruments and voices with a more solid lower register. The other will sound slightly vague with a loss of focus and less weight in the lower frequencies. When you have identified the correct setting, mark the power connector accordingly.
Now connect the next component, your tape deck or tuner perhaps, and go through the process again, identifying and marking the correct polarity for THAT component. Repeat the process for each component in turn until you have completed the settings for your entire system. For two part components, if they each have a dedicated power connection, then treat them as individual components.
By phase, we are not referring to the gross distortions immediately recognisable when one of your loudspeakers is connected out of phase, but to absolute phase. Why is this important? Well, not every hi-fi component maintains phase coherency throughout the entire signal path.
Indeed, some components invert phase from the input to the output. If you want to be pedantic you could analyse each component seperately and if need be carry out internal modifications to ensure phase coherency. However, for a simpler approach, especially if you primarily listen to one source such as CD or disk for example, you might try the following.
Having set up your system to give the best possible sound, including carrying out the polarity tests referred to above, try the following test. Play
a familiar, good quality recording which has a good sense of depth and a defined acoustic. Now swap the positive and negative connections
to BOTH loudspeakers and listen again. Is there a difference? Does one position provide a more distinct acoustic with sharper imaging?
Then this is the correct position. Note! This is a fairly subjective test and not absolutely conclusive as there may still be phase inconsistencies between individual source components. Indeed, there are sometimes phase inconsistencies between drivers in multi driver loudspeakers. It is a broad subject area on which you COULD spend a lot of tweaking time. However, the simple test referred to herein may prove valuable for you.
Now, here is where we may upset the applecart with regard to conventional thinking! There seems to be an assumption, particularly among the mainstream hi-fi press, that everything should be "hard"-coupled to it's surroundings using spikes or similar devices. However, if you stop and think about it, this assumption is quite flawed. I will readily acknowledge that, in some cases, the deployment of spikes may give a subjective improvement, but not necessarily in all cases. This is particularly so with loudspeakers, but may also be the case with some source components, depending on the precise environment.
Let's think about loudspeakers for a moment. Loudspeakers produce energy and vibrations. Some of this energy is converted into sound waves via the piston motion of the individual drivers. This represents the primary sound source of what we actually here (or to be precise, what
we think we hear). However, some of this energy is dispersed through the speaker enclosure in the form of vibrations. When mechanical vibrations travel through and meet other surfaces at contact intersections, there will be certain natural resonant frequencies in the next surface
which may or may not be excited by the vibrations. A tuning fork provides a good example of this principle.
Excite the tuning fork and place it on a resonant surface and see what happens. Get the picture?
By "hard" coupling the source of vibrations to the next surface in the chain, you provide a more efficient path for the vibrations to travel down. When there are several surfaces involved, there may be several natural resonant frequencies which may or may not be excited by the source
vibrations. Consider for example a loudspeaker mounted on a shelf which is itself fixed to a wall via brackets (don't sneer, this is a perfectly valid method of deployment, despite what the purists say, and may be the only option in some situations).
Now we have the energy flowing from the speaker cabinet into the shelf. From the shelf into the brackets, which in turn provide effective coupling to the wall. You may think that the unwanted energy is diminished as it travels this path and, in many cases, this will be the case. But not always. Sometimes the resonant properties of other surfaces may be excited (just like the tuning fork principle) producing an additive effect at certain frequencies.
This in itself represents an unwanted distortion which can be quite audible, although many people would not notice until you take it away.
From the above you will understand that "hard" coupling is not necessarily a good idea. Sometimes we actually need to decouple between surfaces in order to clean up resonances and remove unwanted distortions. In the case of the loudspeaker mounted on a bookshelf, we may
need to go completely against established thinking and decouple the loudspeaker with a soft, compliant layer to absorb the unwanted energy and break the transmission chain.
Having conducted experiments along these lines myself, I can tell you that this approach can sometimes be very effective indeed. But there is another factor to consider here. Sometimes the 'hard' coupling approach can actually cause cancellations at certain frequencies due to the interaction between surfaces. That's right.
You thought you were "tightening up" the sound when in fact you may have been robbing the sound of natural output all along. However, without complex measuring equipment and a good understanding of the physics involved, you will have to let your ears be the judge of the right approach to such things. If you are fortunate enough to have a good quality live recording from a venue with which you are intimately familiar, this may be a good starting point. Similarly, if you REALLY understand what instruments sound like (many hi-fi buffs do not) a recording of a small ensemble playing a familiar piece will be useful as a test piece.
The moral of the story above is do not be afraid to experiment. Forget what the experts and magazines say (if you must listen to someone, listen to a structural engineer). Try a few different coupling techniques with your hi-fi components and use your ears to listen to the result without prejudice as to whether the approach follows fashion. You may be pleasantly surprised.
© 2002 Copyright Julian Ashbourn - http://www.tnt-audio.com