Volume Level, Crossover, Fine Tuning | Hsu Research STF manual

Setting the Phase

Turning the subwoofer ON for the first time

On the subwoofer, check that the phase switch is at 0 degrees, the volume level knob is at the minimum, and the crossover is at 90 Hz if using the subwoofer’s crossover. Run the power cord from the wall to the subwoofer and flip the power switch to the AUTO-ON or ON position.

Step 4: Volume Level

Many people use ordinary music recordings or soundtracks for setting the subwoofer’s volume level. If you are using this method, try adjusting the subwoofer’s volume level so it matches the main speakers at the listening position. Since most people do not listen to material at very loud reference levels and the ears

are less sensitive to bass at lower levels, some listeners prefer to set the bass level a little higher than the main

speakers. A good approach is to set the subwoofer level to the highest level where it sounds nice and where

bass and kick drums still sound tight and non-boomy. For home theater applications, most prefer to set the subwoofer level higher than the other speakers. We suggest setting it about 3 dB higher. Some proces- sors/receivers allow you to set different bass levels for different sources.

Optional: subwoofer integration will be more accurate when using test tones and a SPL meter. See Step 6 (Fine Tuning).

Step 5: Crossover

If you are using the SUBWOOFER or LFE output on your controller, you may optionally set the CROSSOVER switch to OUT. This lets the controller handle the crossover between the subwoofer and other speakers. However, if the bass sounds boomy, it may sound better with the crossover switched IN and the CROSSOVER FREQUENCY set to 90 Hz. You may skip the rest of this step.

If you are using the HIGH LEVEL speaker connections, you will be using the subwoofer’s crossover. Look up the lowest frequency your left and right speakers will output (the frequency they are“-3 dB” at) and set the crossover approximately to this point. Play program materials with steady, consistent bass around this frequency such as filtered pink noise or music containing bass drums, double basses, bass guitar, etc. Turn the crossover to the left until you hear the subwoofer and L/R speakers as separate sources. Slowly turn the control back to the right until the sound of all three speakers is well integrated. When using tiny front speakers that don’t have much bass, the 90 Hz setting on the control will probably yield the best results.

Your subwoofer has a sharp 24 dB/octave crossover to remove the midbass and midrange in the subwoofer. This makes your subwoofer non-directional. Unlike many other subwoofers on the market, the 24 dB/octave slope stays steep at all available frequencies, not just the high ones.

Step 6: Fine Tuning

Now that the basic setup is complete, it’s time for optimization. Mark down the current volume and crossover settings with a soft pencil so you can go back to where you started.

Depending on the absolute phase of your main speakers and amplifier, and the distances of the subwoofer and the main speakers from the listening position, the bass in the crossover region may be smoother if you reverse the phase of the subwoofer. Switch the phase switch to 180 degrees to see if the bass sounds louder in the seating position. Play program materials with steady, consistent bass in the crossover region (30 – 90 Hz). Filtered pink noise is best, but you may use music containing bass drums, double basses, bass guitar, etc.. The more bass-heavy setting is where the output of the subwoofer and the main speakers are most in phase. If the 180 degree position is louder, you will need to go back and adjust the volume level (Step 4). Otherwise, just switch the phase switch back to the original position.

Volume fine tuning

For the most precise integration with your main speakers, go through test tones with a SPL meter. Setting the level using test tones by ear may result in misconfiguration, so please use a meter.An analogue Radio Shack SPL meter is inexpensive and works better for this application than the digital Radio Shack SPL meter. It is available at RadioShack.com. Use the "C" weighting and “SLOW” settings.

Using a test disk with one-third octave filtered pink noise or warble tones, measure from the listening position with the volume at 75 dB with a 50 Hz tone. Test tones are available on the Stereophile Test CD 1, available at Stereophile.com. Do not play the test tones extremely loud as this might damage your speakers. Take measurements of four different tones above the crossover point and four different tones below the crossover point. Note that the Radio Shack meter is down about 12 dB at 16 Hz, 7 dB at 20 Hz, and 3 dB at 30 Hz, 2 dB at 40 Hz, and 1 db at 50 Hz. Add these numbers to the readout to compensate. Average together each set of four measurements and adjust the subwoofer’s volume level to compensate. Repeat the measurements until the subwoofer matches the other speakers.

A less accurate method uses the receiver’s test tones, which are usually not in one-third octave increments. Measure from the listening position and set the subwoofer volume level to match the other speakers.

Removing buzzes and rattles from the room:

Annoying sounds can be fixed by using adhesives, tape, or felt pads in the area where objects are vibrating against each other.

Equalizing the subwoofer

If you have an equalizer, avoid raising dips in the frequency response. Instead, use the equalizer to remove peaks. This will prevent potential speaker damage.