Speaker Placement

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For serious ham radio ops, taking time to properly position external speakers is DXsential when it comes to getting the best RX sound out of your rig.  Sound, after all, is our core business and we want to be able to enjoy the fascinating soundstage of incoming TX audio at its very best!
An article on correct speaker placement for hams, however, is very difficult to pen as every setting — and every speaker — demands a dissimilar line of attack to optimization.  (Unfortunately, the quality from some our renowned radio company manufacturers isn’t always the best either!)

Fortunately, there are some guidelines we can use, though, to aid us in our pursuit of perfect shack sound…


ham_radio2Operating Environment

The ham operating environment throws up a multitude of problems in choosing a location for external speakers.  Shack layout, furniture, aesthetics, what’s competing for space on the bench top, accessibility by children, pets and the YL are all real issues.

To keep things simple, I’ll assume you have unlimited freedom…


The Room

Essentially, a room (e.g. the Shack) influences the sound of a speaker by the reflections it causes.  Some frequencies will be reinforced, others suppressed, thus altering the character of the sound.

If we’re to listen to our external speakers in the field, during dx adventure for example, then much of the coloration we’ve been used to hearing in the home shack would disappear.

The real world, however, requires that our speakers co-occupy our radio shacks.  For that reason we must deal with the room as a significant contributing factor.

In any listening environment, what we hear is a result of a mix of both the direct and reflected sounds.  Direct sound travels straight to our ears from the speaker diaphragms.  Reflected sounds are numerous, bouncing off most any hard surface and reaching our ears after the direct sound.

Generally, the direct sound from the speakers are primarily responsible for the image, while the reflected sounds add most to the tonality of the speaker.

Any boundary surface such as a back wall, side wall or floor can cause a reflection, and all need to be weighed up during placement.  The trick is to place the speaker in a location that will take advantage of the desirable reflections whilst dwindling the unwanted ones.

On to specifics…


Distance to the listener

For proper imaging to take place, sound from each external speaker (assuming you’re using twin speakers to enjoy your RX audio) must arrive at the listening position in front of the transceiver at precisely the same moment.  This requires that the speakers be exactly the same distance away from the main seating position.

[Note: I’m talking about precision here.  Difference of less than ¼” will be audible in better systems to careful listeners].

Using a tape measure for this procedure can be cumbersome, so I like to use a string.  It’s easy and accurate.

  1. Tape a string to the midpoint of the shack chair, trying for a spot as close to ear level as possible.
  2. Unroll enough string to reach one of the speakers, then pull the string taught to a reference point on the speaker — I like to use the tweeter.
  3. Grasp that point on the string with your thumb and forefinger, then walk to the other speaker to see how it compares. Simply adjust the distance until each speaker is exactly the same distance.

Distance to side wall and back wall

It’s well known that the closer a speaker is to a boundary such as a wall, floor or ceiling the more bass reinforcement.  Changing the location in relation to these surfaces will dramatically affect both the quality and quantity of the bass.

With regards to soundstaging, you’ll find that depth is dramatically influenced by rear wall proximity.  Increasing the distance from the speaker to the wall behind will increase soundstage depth.  However, pulling the speaker too far out may degrade focus.  In most cases, shack layout dictates the maximum distance the speakers will be allowed to intrude into the space, but experiment to as a great degree as possible.

Most external speakers need to be a minimum of 1-2 feet away from the side and back walls to reduce early reflections; and on this note, it’s most important to ensure the distance to the back and side walls is unequal.

Do not place the speaker, say, 20″ from both back and side walls.  That said, be sure both speakers are set the same as symmetry is very important.  By that I mean if the left speaker is 20″ from the back-wall and 30″ from the side-wall, try to place the right speaker in the same way.  This may not be possible in all situations, but do your best to give each speaker a similar acoustic environment.


Distance between speakers

This will be decided by the distance to your radio shack chair, the particular speaker you own and, to a great measure, your own personal preference.

I usually prefer to start with an equilateral triangle, the apex of which is located at the listening position (i.e. in front of the rig) and the 2 speakers forming the base line and experiment to produce the best soundstage.

As discussed previously, the distance to the side walls affects tonal balance.  As we move the speakers closer or further apart, the relationship to the side walls change.  Further, the proximity of 1 speaker to the other will influence tonality as well.


SP-950Tilt

Tilt can be very important in influencing the sound of a speaker.  Although most external speakers today should be level, some designs recommend specific tilt (generally rearward) for proper imaging.  Designs such as the Yaesu SP-2000 or Kenwood SP-850 pictured right are adaptable via the 4 cylindrical feet at the base of the unit.

I recommend starting level, and experimenting rearward from there, if necessary.  It’s very rare that tilting the speaker forward will be of use.  Use a carpenters level for accuracy, and remember to check both front to back and side to side.


Listening Height

Every speaker has been designed with a specific listening height in mind.  Generally speaking, your ears should be on axis with a point midway between the tweeter and woofer (two-way) or tweeter and midrange (3 way).  Again, consult the manual of your speaker for specific recommendations.


Summation

For hams, experimentation is the key to optimum results for the placement of external speakers in the shack.  Trial and error will tell you a great deal about how the speaker reacts in your shack environment and help you to better balance strengths and weaknesses of each position you try.

The goal in determining the position in the shack is to excite as few of the standing waves as possible.  Once you’ve found a rough position, place 2 pieces of masking tape on the approximate surface, one marking distance to back wall, another noting positing from the side wall.  Mark the tape in 2cm increments.  This will allow you to move each speaker exactly the same amount, without having to re-measure each time.

Exact distances are critical!  Always use a tape measure, a cm can make all the difference in the world.

When setting up new external speakers, don’t rush through the process.  Take your time and slowly find the ideal location over a few weeks of listening.  Pressing to find the right position can be very frustrating.  Also note that the sound of the speakers will change during break-in.  Play the speakers for at least 100 hours before fine tuning placement.

If you’ve already placed your external speakers, but didn’t put much thought into the process, spend some time tweaking your speaker set-up.  I think you’ll be enormously satisfied with the results.