MK Sound S-150THX C, S-250 Satellite/Subwoofer Phasing Test, Speaker Damage & How To Avoid It

MAIN SATELLITE SPEAKER

8.SATELLITE/SUBWOOFER PHASING TEST

In any system using a subwoofer separate from Satellite speakers, a phasing test must be performed to insure good bass blending. This test insures optimum sound in the critical bass frequencies where your Subwoofer and Satellite speakers overlap.

HOME THX AUDIO SYSTEM

For a Home THX Audio system, follow the system instructions provided with the THX controller, as you will need to have correct phase among all the speakers in the system. These instructions will take you through the front channels, surround channels, and subwoofer.

SATELLITE/SUBWOOFER SYSTEM

If you own an M&K Powered Subwoofer, see its owner's manual for the correct procedure for matching phase between the Satellites and Subwoofer. Its "SUBWOOFER PHASE" switch makes this important test very easy. If your subwoofer does not have a "SUBWOOFER PHASE" switch, follow this procedure:

Play a familiar CD, LP, or tape with steady, consistent bass content through your system. Listen carefully to the "mid- bass" region of 75 - 125 Hz. This is the part of the spectrum where electric or string basses and drums predominate. Then, reverse the Positive and Negative speaker inputs on the back of BOTH Satellite speakers.

You can do this at the back of both Satellite speakers, or at the Subwoofer's "TO SPEAKERS" terminals (certain models only), but never at both locations. The lead that was on the Positive (+) terminal should be switched to the Negative (—) terminal, and vice versa.

Now listen to the same musical passage as you did earlier, concentrating on the mid-bass region. If you hear less bass, the original connections were correct. If you hear more bass, the new connections are correct.

You need to perform this test because when Satellite speakers are located separate from a Subwoofer, each speak- er is at a different distance from your ear. In some cases, the difference will be just enough so that the output from the Subwoofer arrives out of phase with the output of the Satellites. When this happens, that critical mid-bass is actually can- celled. You should re-do this test any time you move your speakers.

If you want to experiment further, you can move the Satellite speakers either towards or away from your listening posi- tion, making changes in small increments. This will "focus" the system's sound to its optimum. When you hear the best balance between stereo image localization and maximum impact and output in the mid-bass, you have the ideal location.

9.SPEAKER DAMAGE & HOW TO AVOID IT

An important factor to consider with any loudspeaker system is the potential for speaker damage. Even though your speakers have extremely high power handling ability, they still can be damaged by relatively low powered amplifiers.

While very few M&K Satellites are actually returned for service, the vast majority of those returned are not for man- ufacturing defects. Instead, they are returned because they have been overdriven, almost always because the amplifier or receiver used was driven into clipping distortion. This damage is considered abuse, and is not necessarily covered under warranty.

This clipping distortion occurs when the demands of the music are greater than the amplifier's available power. It can occur at 20 watts with a small amplifier, or at 400 watts with a large amplifier. Regardless, when this happens, the amplifier's output waveform (which usually looks like a smooth arc) is "clipped" off, exhibiting a flat top instead of the arc.

This flat top contains multiples of the original amplified frequencies, sometimes at higher levels than the original sig- nal itself. For tweeters, this can be very damaging, as this distortion is well above the audible range, where you will be unable to hear it, and where the tweeter is more vulnerable to damage.

When an amplifier clips, its sound becomes harsh and grating, and a break-up is often audible in the bass frequen- cies. It will become uncomfortable to listen to, compared to a slightly lower volume level. When you are listening at high volume levels, be aware of the onset of clipping distortion, and turn the volume down slightly if the sound takes on the character described above.

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