4. Assembling Critical Playback Systems

The First question to ask in setting up and maintaining a critical playback system is, what makes it so? As in recording music there are endless possibilities and multiple levels available. Achieving this goal is limited to one’s own ability to assess the limitations that are intrinsic to these systems, and exploring what is possible. 

For the purpose of this class we will be researching primarily live recordings done with minimal microphone techniques (true stereo) and studying their recording and playback natures. These recording typically present wider dynamics, finer harmonic structure and in general the ability to hear further into the music.

How we judge the quality of the playback system is always limited to the source mechanisms, and of course the software (recordings) being played on them. Most recordings are assembled from panned mono sources, equalized, often compressed. These functions are used to create a desired result.

When played on an average or a critical playback system a certain limitation will exist. In other words a recording with certain dynamic limitations will not vary in sound quality to the same degree as a less limited (True Stereo) recording. Therefore playback becomes less critical.

A True Stereo recording will often sound limited on an average system. The wider dynamics and sense of fine harmonic structure are simply not reproduced, at times making it less exciting. Playing these recordings on systems with more capabilities will quickly reveal their inherent advantages. The greater it is able to reproduce the nuances (to get quite) the more we will appreciate more critical playback systems, as well as our skills in assembling such.

As we know in the Sound Hierarchy, we will always start with the source in this case the playback medium. Recordings will vary greatly but in order to assess their content we must retrieve the maximum amount of information from them. Whether it is CD, LP, Tape, etc. the playback medium must be faithful to the source (recordings) material. A competent amplifier and speakers will nearly always be more involving with a better source, than a higher quality amp and speakers with a less quality source.

In my estimation this fact alone is partly responsible for many individuals having difficulty identifying what a truly good playback system is. Often they will pick a component generally the speakers that will limit or filter the sound to the tonality of ones particular taste. If on the other hand we start good quality source and evaluate in a single speaker demonstration space our own ability to reconstruct the sound will generally be less limited. This will allow us to form a more realistic view of the systems playback capabilities.

Once we have established our source we next select a preamp or integrated amp to process it. Again the goal is to transfer this information through this chain to power amp or speakers in the case of the integrated amp.

Using an inadequate preamp will limit the source and using a great power amp without an adequate preamp defeats our objective. The preamp is handling a smaller bit of information than the power amp, and is more susceptible to hum and noise that can effect it’s performance. Keeping stray fields such as power supplies, especially digital sources including internal A to D and D to A converters that will effect the ability to keep this delicate signal intact. The use of integrated amps if often a compromise for these reasons, and the use of surround sound processors with all their digital elements make for a near impossible environment.

After the preamp the selection of the power amp is our next objective, of coarse if we chose an integrated amp we have already selected this. Although integrated amps can be very good it is unlikely to give us the optimum results. The power amp must except the incoming signal from the preamp and also drive our chosen loudspeakers, power output (wattage), handling wide impedance curves (from speakers), low distortion are all important considerations. Although having a higher power rating and low impedance capability will not guaranty great results, specifications are a guide to performance, listening will in the end give us the answers.

The loudspeakers are more subjective and are the most affected by the environment into they will be employed. Placement, room acoustics, dispersion characteristics, bandwidth are some of the criterion we must face when interfacing speakers. That is given the equipment proceeding them are up to the task.

Specifications with speakers are almost meaningless measuring in an anechoic chamber is not the same as playing back in a listening room. A larger more complex Speaker (more drives, crossovers, etc) will often times be less useful than a small monitor, because it is limited by it’s own complexity. You are better off with less bandwidth that is more correct than having bass that is sloppy and out of tune, putting high quality parts in a cheap speaker cabinet never gives good results.

Placing the speakers can also be a challenge especially with full range types. Even if the speaker is doing everything basically right (staying out of the way of the music) the room it is put into can limit or destroy it’s potential to operate correctly. Distance from the room surfaces and standing waves or other rooms modes all add in the equation to obtaining maximum results to a given system.

Assembling a quality playback system is like all other subjective tasks. Having a good reference point of the overall Sound Hierarchy and knowing the source material will increase your ability to assess all situations to a greater benefit.

Ken Christianson, Pro Musica, Chicago

posted on: 2011/09/14
* 12. True Stereo in Perspective
* 11. Room & Boundary Effects for Playback Systems
* 10. Instrument Positioning & Room Manipulations
* 9. Choosing a Space-Acoustical Considerations
* 8. Troubleshooting True Stereo Sound
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