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The rule is: There are no rules
Hi Guys

Stereo playback systems are only really defined or limited to the fact that there are two audio channels. Apart from that, however you wish to approach things is up to you.

There are some guide lines that are helpful.

The room should be one where a Human conversation sounds natural. Not too reflective or echoey. Not too dead. Just right. Something Goldilocks would approve of were she interested in audio matters.

The two acoustic sources should be full range, covering the range of Human hearing from 20Hz up to 20kHz. If you are interested in pipe organ music, you might want to add a subwoofer to each side to extend the range below 16Hz - the lowest note Bach demanded.

However the speakers are arranged on each side with respect to whether it is one box or several with narrow ranges, they should be clustered to appear as much like a point source as possible. There are many speaker types that arrange the woofer lowest, then the midrange above, and tweeters above that. There may be intermediate ranges of drivers, or multiple drivers per range. In the case of planar (flat) speakers, sections of the panel may be limited in range and the horizontal plane of the audio image will tilt with frequency and with seating height of the listener.

One aspect of the speaker selection is with regard to the width of the "sweet spot" for the listener. This is the optimal seating position to experience the best audio image.  Wider speaker separation can widen the sweet spot, as will a more diffuse presentation of the sound. Bose made their name using acoustic diffusion, essentially bouncing the sound off the walls so the image is "wider than the room". There is a natural effect in the result, but new distortions are added by the room itself. Other decisions made by the designer further impair the accuracy of the sound. For example, in the 901 model there are eight drivers facing the rear and one facing the front (towards the listener). All the drivers are identical with just under 1-ohm voice coils, then all wired in series to present 8-ohms to the amplifier. Every driver is undamped with respect to its reverse current generation, which distorts the sound as the amplifier has no control over the driver cone position. This was a super high-profit model for Bose and they sold a lot of units. Obviously a lot of people found the sound to be acceptable.

The choice of amplifying equipment and signal sources is up to each individual. What do you like? Do you want integrated equipment, or separates? do you listen to vinyl LPs? 78s? Edison rolls? to tape? to CDs? to the radio? or do you just need TV sound? Do you prefer all solid-state? or tubes? or hybrid? Do you need this to tie in with home automation systems? Should the stereo be small? the size of a bread box? the size of a refrigerator? maybe the latter are your speakers?

There is usually a distinction between "accuracy" and "fulfilling". For some people, these are the same, but for everyone there is a nostalgic goal of finding what first excited us about listening to music that we want to recapture. Once you are there, the system should disappear and you are inside the music.

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