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4) A simple three-step speaker installation technique for satisfying results
This three-step technique will get you to a satisfying sound faster than any other system I've seen.
The three steps must be followed in this order.
3. Frequency response/tonal balance
OK, what do we do at each step?
First, you've got to get the bass generally pretty good. This means that if you have a full-range speaker, it should reproduce the deepest bass with the greatest smoothness.
Why does the bass come first?
Until you know how far away you'll be sitting (speaker position and listening position), how can you proceed to step 2, getting the best stereo image? And we've seen that we can make some adjustments in the overall frequency balance with subtle changes in position (separation and toe-in). But first weve got to at least establish the distance to the speakers from the listening seat before we can begin to decide how far apart we want our speakers.
(1) The best bassa throwback to early TVs.
Here's how long I've been teaching this technique for getting the best bass
I started out using a TV analogy that asked the installer to compare this step to the tuning methods from TVs of the '60s and early '70s! Those TVs had a fine tuning knob and channel selector switch. Here's the analogy: Finding the best placement for the speaker in the room is a bit like fine tuning for best reception. But finding the best place to locate the listening seat is a bit like using the channel selector!
In other words, the most important consideration (whenever possible) is to discover where in the room you should sit to take advantage of the least negative room interactions (obvious peaks and dips in the bass), and the most positive room interactions (the most extension and attack without annoying overhang).
This is because your room will have obvious standing waves developing in the bass region (well call this region 25 Hz to 250 Hz). These standing waves are very measurable and they are quite audible as resonances or 'suck-outs.' They exist due to your room's particular geometry.
Moving a speaker forward and back in the room can make a noticeable difference in the bass. But moving the seat forward and back the same distance in an average room will result in much more dramatic differences in bass performance.
Although these resonant room frequencies can be considered axially, tangentially, and obliquely, our primary concern here is with axial. These consist of destructive (to varying degrees) waves and constructive (to varying degrees) waves. A destructive standing wave is produced when two or more wavelengths meet at a point in a room, anddue to the time arrival of these wavessome will arrive slightly (or even directly) out of phase with others.
The varying time arrival is based primarily on room geometry (for examplelength of the room vs. height). This results in a cancellation of frequencies at that particular point in the room. Destructive standing waves produce dips in frequency response. Conversely, constructive standing waves can produce peaks in response.
The following system assumes you've placed the speakers in a generally acceptable position in the room:
A simple way to prove this theory is to put on a CD recording with a repetitive bass line (preferably the upright acoustic bassmaybe Ray Brown). You'll need to move your listening seat out of the way, perhaps to the side of the room.
A note on the recording select a piece that plays bass notes up and down the scale. While it's playing on repeat (that's why I chose CD as the source), walk back and forth slowly through the larger proposed listening area. You'll notice dramatic differences in bass quality and quantity in a space of +/ 2-3 feet. Listen closer and you'll find the smaller 'window' of acceptability for that particular bass line.
Once you've found the best spot to locate the seat (again, only for that particular series of bass notes), you'll notice that moving the speaker forward and back an equivalent difference makes much less of a difference. This is all to say that your room resonances are going to be pretty much the same for most likely speaker placements, so find out where in the listening end of the room these resonances are least objectionable, and that's where you'll sit.
A quick note on finding the overall best bass listening position in a roomthe quickest way to do it is with a real-time analyzer, preferably 1/3 octave. You'll need to use pink noise as your source, set on the slowest filter, using flat or C-weighting. You'll need to run its SPL level at least 20dB over the room noise floor, so as to avoid any unrecognized interference with your measurements.
You're only looking at the region from around 25 Hz up to about 250 Hz. You'll notice i[ img ]mmediately that fairly small movements forward and back in the room are very obvious on the display as the various peaks and dips become quite easy to see.
Don't have a RTA sitting around? Try to borrow or rent one for a few hours. By the way, I do NOT recommend using a Radio Shack SPL meter and test tones for this procedure. Actually, if the tones were 1/3 octave pink noise bands, it could perhaps work, but unfortunately the Radio Shack meter simply isn't very accurate in its frequency response. And the RS mic suffers from proximity effect, unlike an omni (which is the preferred pick up pattern for a microphone in this application).
You could use the test disc and your ears, though! Can't find a RTA, or youre uncomfortable technically with the idea of looking at how your room behaves in the bass resonance region?
Then find several recordings of music representative of the stuff you like to hear, and adjust for the best bass by listening while moving back and forth in the general listening position. What you're listening for is the majority of the bass reproduced with the notes neither emphasized nor diminished. You're also listening for the deepest bass. But sometimes the price for getting the deepest bass in an average room is an uneven bass response in the region where most bass notes occur. This is where youll have to pick the best compromise to your ears.
At this point, you'll find that a difference of six inches or less forward or back will usually present you with a choice of the bass compromise you prefer. Once you've discovered this listening position that is least affected by room resonances, mark this spot (or at least measure how far it is to the wall behind you and write it down).
Now you can play with fine-tuning where the speakers go to make the bass better. Once you have that position to the point that is best to your ears, you'll need to recheck the listening position a bit to make sure that a slight distance forward or back isn't necessary now.
(2) Imaging and the X-files
Finally you've establishedpretty closelywhere you'll be, and approximately how far away the speakers will be. Once you know 'X,' you can start to work on 'Y.' X is the distance from your ear to the plane of the tweeter (should be equidistant from the listening seat to each speaker). Lets say X is 10 feet. A general guideline is to start Y at about 80% of X. Y is the distance from the center of the left tweeter to the center of the right. We use the tweeter because its the primary source for directional cues (imaging).
A note on separationthis is to your taste. I personally like Y to be about 83% of X for most speakers. For planar speakers, Y may be smaller, maybe as small as 70-75% of X. Some companies want you to use an equilateral triangle (X and Y are equal in distance), or greater. I suggest playing a mono source like female vocals and keep pulling the speakers apart until the voice becomes a fairly precise point between the speakers. Pulling it apart any further results in a too small voice or one that now begins to come from each speaker. Bring them back to the point where it worked, switch from mono to stereo and check out the image. This technique assumes you've established a grid on the floor so that movements are the same for both channels.
The other test is simply to notice when the female voice starts to sound unacceptably thin. Then voice the separation by tonal balance, as well as image precision. Once again, it's a compromise. You have to decide what means the most to you.
(3) Frequency response/tonal balance
Remember how we said that changing the separation could yield a cooler or warmer sound? And how toe-in can also dramatically affect balance (particularly high frequency balance)? Well, now you're at that point (this assumes that your speakers are either nonadjustable, i.e. tweeter lever control, bass level control, etc., or that you've selected the nominal 'flat' position as a starting point).
Here's an exampleand listen, it's just an exampleyou might feel quite differently. I find that if I set up most direct radiating speakers on an equilateral triangle, the sound (for my taste) is usually too lean. I can hear all the tiny sounds in the soundstage, but it's become a precise, almost mechanical sound. It's not 'relaxed' for want of a better word. It makes great Audiophile stuff, but the sound just doesn't have the body and warmth that I hear with live music.
And yet, I know highly respected reviewers and manufacturers who prefer to listen with Y being greater than X. Thats why its your tasteremember, it's not about some notion of 'accuracy,' it's about the music and you.
Step 3 is the final fine-tuning that will make the difference for you. One final notesome Audiophiles adjust toe-in to make the speaker seem to 'disappear.' This is usually not on axis, but aimed to crossfire somewhere behind your head, or even aimed straight ahead. This is your call as well. I recommend going for the musical balance before going for an audiophile sound effect, but sometimes you can get both, so go for it if you like
This should get you pretty close to a satisfactory set-up.
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