Originally Posted by Frank007301
Hi Guys. I am a newbie here from South Africa. Just thought i would put my system out there and hear what you guys think.
A friendly suggestion; acoustically, the interaction of your mains and the surfaces immediately surrounding them can really be detrimental to smearing detail, and blurring imaging. I would experiment with some very simple re-positioning, and I'd be relatively confident it would do wonders.
Bring the L&R inward toward the center and away from the sidewalls. This will be a significant improvement, yielding a smoother FR, heightened detail and improved imaging and soundstage. Now, the next re-position is more hit or miss, however it's free and may be quite worthwhile. Experiment with varying distances between the back of the speaker and the front wall. This placement distance is critical for bass/mid-bass impact and smoothness. Proper bass detail and delineation is elusive, and this is impacted by a few factors, ... one of which being the acoustic relationship between the front wall and the speaker distance. Dips and suck-outs of response can result from this interaction, just as a nice smoothing and increase in detail.Here
is a well written representation of what I'm referring to. The effect in acoustic terms is SBIR, or speaker boundary interference response.
The acoustical interference between your speaker's front radiation, and the reflection from the wall behind a speaker. In the bottom octaves, the wavelengths are so big the reflected energy is still essentially in phase with the direct, forward radiation. But the problem arises as the frequency goes up into the mid-bass and the reflection off the front wall begins to be more and more out of phase due to the extra path it has to travel compared to the main forward radiation of your speakers. The frequency dips occur when the reflected energy begins to be in opposite phase relative to the direct energy. Typically, one can see huge swings in response, as much as 10-20dB deep.
So, you either place them right up against the wall (this is why studio monitors are flush mounted), or far enough away to put the dip below the passband of the speaker. Ideally, they tend to image better away from the boundary, so that's typically where I'd start. But perhaps you may find the placement up against the front wall to be best (or necessary aesthetically). When you place the speaker close to the wall, this raises the frequency of the interaction higher, and up into the range whereby the front energy is more directional so the interference is lessened due to less rearward energy to begin with. At lower freqs, the waves are so big that the radiation becomes almost omni-directional, and much of this occurs within the critical range of imaging and detail. this is why loudspeakers need space around them in general, so that output isn't reflected back and smeared, ...even to the sides etc. This is why cabinetry etc, is so, so detrimental.
All this is based on quarter wavelength cancellation. This is when a speaker is a quarter wavelength away from the boundary, the returning wave becomes one half a wavelength out of phase which is total cancellation. So subs can
benefit from being within a quarter wave from their adjacent boundaries, and mains can
benefit from being at least a quarter wavelength away from the boundaries. All this is based off the lowest frequency within their operating range for mains, and the highest freq in the operating range for subs.
Wave Length in Feet = 1130 / Frequency
So, 80hz is the ideal example since it's often essentially
the subs highest freq, and a mains lowest freq.
1130/80 = 14.125, or about 14 feet long (that's the full sine wave)
So, thinking acoustic interference off an adjacent boundary, we consider quarter wavelengths.
A quarter wave for 80hz is approx 3.5 feet. So placing a sub within that distance from the adjacent surfaces will help in not having the cancellations associated with 1/4 wave boundary interference.
Likewise, placing a LCR loudspeaker, at least a 1/4 wave or greater (of the lowest freq within it's passband) away from the adjacent boundaries, or 3.5 feet or more away, places the dip below 80hz, and below the operating range of the speaker.
Below is a graphic representation of this;
Additionally, another tip is to attempt to not place both the sidewall, and the front wall behind the mains, at the same distance from the speakers. If you stagger these distances somewhat, it further smoothes these types of interactions. Also, if you place acoustic absorption directly behind your mains, directly to the side of your mains, this also reduces the amount of out of phase energy that re-enters the picture, ... thus, reducing the dip even further.
Best of luck