Audio Tweaks

What can be done in the audio section of our system? Well, the answer is LOTS! Starting with cables to crossovers, adjustments, room placement, etc. I'll just cover what I've done on mine, you can roam the internet for more ideas.


You can click back onto the Speaker Setup Page here for some of the placement guidelines, to get it down more to a science, you need to gather up a laser level. One of the first things I did, was to set the level up on the front left and right speakers, and aim them at my sweet spot (where I sit for normal viewing). You can use some masking tape to mark where the beams hit for now. You should also mark a target area for where you'd like the beams to converge. Adjust each speaker to get the beam where you want it to be, which should be at ear level in your seating position. When the left and right are done, aim the center channel speaker for the same position as well. On my rear speakers, I found that they were not at the same distance from the front of the room. Using the laser level, I was able to correct it. If you feel the front soundstage is not wide and deep enough, experiment with the toe-in on the speakers, widening the gap to get it where it sounds best to you.

Adjust the phase between speakers

This next part is lengthy, and you will need to have the following tools to perform it: The Avia setup DVD, and a sound level meter. These instructions are not mine, they are from Guy Kuo, the man behind the Avia DVD.

Using AVIA Phase Tests to Fine Tune Speaker Distance and Delay

    AVIA's speaker phase testing signals are also useful for very accurate adjustment of speaker delays and distances. You'll need an analog RS SPL meter set to fast response in order to take advantage of this tidbit. This may seem a bizarre way to check delays and speaker distances but it is surprisingly accurate.

    The phasing tests work by playing noise in the two channels being tested in phase and 180 degree out of phase intermittently. If the speaker distances and delays are both set correctly, then the in phase sounds from both speakers reinforce each other at the prime listening positioning. During the out of phase (diffuse) portion of the test, the sounds cancel. An SPL meter set to fast response can readily show the magnitude of the cancellation/reinforcement.

    Start by playing the Phase left front/right front signal. Move your SPL meter slowly left and right at your listening position. If you have set distance and delays correctly the maximal SPL delta will occur in the middle of your sitting position. I get about a 6 dB needle bounce on my system. If it happens right of center, then your right speaker is either too farther away than the left speaker or delayed more than the left speaker. Conversely, if the peak SPL delta occurs left of your prime listening spot, the left speaker is too far or excessively delayed.

    Once you have the front left and right speaker distanced and delayed exactly right, the SPL meter position at peak delta will be in the middle of your prime listening position. Note that position carefully. You'll need to be able to refer to that point within half an inch during the next step.

    Now comes the trickery that gets the center speaker also precisely phased and delayed. The AVIA disc also has a Phase Left Front/Center test. We can take advantage of it to bring all three front speakers into very tight phase alignment. From the previous step we already know where the two front main speakers are in phase. Leave the left and right delays and speaker positions alone now. We'll next adjust the center speaker to be in phase with the left front. This places all three into phase.

    Play the Phase Left Front/Center test and once more move the SPL meter left and right to find the maximal SPL delta point. Compare this new position to the one for the front mains. If all is perfect, they exactly coincide. If the left/center maximal SPL delta point is left of the left/right point, then the center speaker is either too close or insufficiently delayed. If the left/center max delta point is right of the left/right max delta, then the center speaker is too far. Move or adjust CENTER channel delay as needed to get the left/center max SPL delta to occur at the exact same place as for the left/right channels.

    Your left, center, right speakers are now in phase. You'll probably note that a 1 msec adjustment in channel delay makes for a considerable shift in max SPL delta position. After all, that is about a 1 foot speaker distance equivalent. Use very small speaker movements to fine tune the center speaker into phase alignment.

    Put your head at the center of the max SPL delta position and listen to some stereo and 5 channel material. You will be pleased with what has happened to sound imaging in your system.

    Moving your speakers to achieve exact phase match isn't the entire story. One must also position the speakers with relation to room acoustics to smooth frequency response. Sometimes, moving speakers into exact phase also moves one or more of them into positions that yield uneven frequency response. In such cases, some compromise is needed to address both imaging and frequency response concerns. Happily, the home theater sound processor does have delays and these can sometimes help bring speakers into phase, while still keeping them closer to best tonal balance position.


BASS Equalization

No two rooms can sound alike, and subwoofer placement can be critical. For those of us who just don't have the equipment and resources to do some tuning, there are some reasonable ways to tune your subwoofer. I chose one that is a self contained unit, easy to install and calibrate without having to buy any additional hardware or software. It's called the S.O.S. (Subwoofer Optimization System). It looks like this:

Click here to go to the ACEI SOS Page

You can click on the picture above to go directly to the ACEI SOS page.
Setup and operation is straight-forward. The unit comes with a power transformer, calibrated microphone, and a short RCA cable.
Simply plug the unit in between your receiver's Sub-out RCA jack and the subwoofer input jack. Supply power to the unit. Attach the supplied microphone, put the microphone as close to your listening position as possible, then move the appropriate switches to start the tones. This unit is designed to remove the most prominent peak in your sub's system. It will keep it in its memory even in the event of a power failure. Once it is active in the system, you can switch out the EQ anytime you wish with a flick of a switch. Here's the graph of my sub before and after using the SOS unit.

As you can see, there was a broad peak in the response around the 30Hz mark. The SOS flattened it out from around 25Hz to 40Hz. I believe the peaks at 63Hz and 80Hz may be from interaction with my front speakers, since my system crosses over at 80Hz. May have to tweak it some more.

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