Making the Connection

ACI's Guide for Hookup/Installation and Setup of Stereo and Home-Theater Systems

We'll give it to you straight . . . whatever you're thinking, the reality is it's probably easier and simpler. Hooking up a stereo is not rocket science, but it can be a bit confusing.  Use this guide to have your system up and running in no time:

• Basic Speaker Hookup
• Cables & Connectors
• Adding Subwoofers
• Speaker Placement
• Common Problems & Troubleshooting

Unsure of the meaning of certain terms? Use the ACI Audio Glossary

Basic hookup is very simple. Speakers require a connection to an amplifier. The amplifier might be a separate component, or it might be built into a receiver or integrated amplifier. All amplifiers have output terminals. For each channel there will be a positive (red) and a negative (black) terminal. A stereo amplifier will have a left and right set of outputs. It may also have a second set often labeled "B". The "B" output can be used to drive a second set of speakers, for example, extension speakers in the kitchen.

Amplifier to speaker hookup is accomplished with speaker wire, (see Cables and Connectors).

Basic two channel speaker hookup

click on image to enlarge

Most important: Make sure that you connect amplifier positive to positive at the speaker and amplifier negative to negative at the speaker. If you are wiring a five or seven channel home-theater system, the principles are exactly the same.

Speaker Level Hookup

Speaker level signal has been amplified to provide the voltage and current necessary to power the speaker. In a basic stereo system there will be a left and right channel, each of which will consist of a positive and negative connection. Many receivers add a second set of outputs for extension speaker use. A Dolby Pro-Logic Receiver has five speaker outputs for left, right, center and two rear speakers. Newer multi-channel systems utilize even more channels. 7.1 for example consists of left-center-right, two sides and two rears plus subwoofer (LFE) channel.

Because the speaker cables are carrying an amplified signal, they must be of sufficient thickness to carry the signal without excessive resistance. The longer the cable run, the more resistance. Cable thickness is measured in gauge, with the lower numbers indicating thicker wire. 18gauge cable is the thinnest that is recommended for speaker use. If the wire has too much resistance, the amplifier will not have as tight a control over the speaker, (the electrical damping is reduced).

Minimum Recommended wire gauges are as follows:
Under 15ft - - - 16awg
Under 30ft - - - 14awg
Over 30ft - - - 12awg

It never hurts to use a thicker gauge wire!

	Bi-wire speaker cables: Two speaker cables that share the same terminals at the amplifier end but have separate terminals at the speaker end. The separate terminals are for attachment to separate woofer-tweeter terminals on the loudspeaker.
	Shotgun speaker cables: Two speaker cables that are "doubled up" to provide twice the amount of wire.

Speaker Inputs

Speaker Connectors

Connectors can also contribute resistance and loss. The main types of connections used for speaker hookup are:

Line Level & Digital Connectors

Line level refers to a signal that is essentially unamplified. The line-level signal may be from a Tape Deck, CD Player, DVD Player or Pre-Amplifier. Most stereo systems use RCA jacks for line-level input and output. The interconnect cable used is usually shielded to prevent pickup of hum and noise. A properly shielded RCA interconnect with good connections is usually quite immune from noise pickup. Powered subwoofers often have line-level inputs as well as speaker level inputs..

Some systems use balanced inputs and outputs which are terminated with XLR connectors. Balanced systems are common in pro-sound applications because the XLR connector is much more "secure" than an RCA and balanced runs are almost completely immune to any kind of interference.

Digital connections are often made between a source such as a CD transport and a matching DAC. These connections are usually AES/EBU (XLR) or RCA ended.

Most subwoofers offer the choices of line-level hookup or speaker level hookup. Here we'll deal with the methods to install the ACI Titan and Force subwoofers. Other brands of subwoofers are likely to have similar hookup capabilities, refer to your owner's manual for specifics.

Titan & Force

The Titan and Force utilize the same electronics package. The built in powered amplifier has RCA line-level inputs for left, center and right channels. Any combination of inputs may be used depending on your system. The amplifier does not have speaker level inputs. However, speaker level converters are supplied for the speaker outputs of a receiver or integrated amp. There are a number of ways in which these subs can be installed in any system. No matter which hookup option you choose, it is important to note that no power is drawn from the main system...

View Titan and Force Hookup / Diagrams

Integrating the Sub(s) into your System

Integrating a sub(s) is a process that requires following ordered steps. Some rooms/systems are easy, and some systems are very time consuming. The key is to eliminate each variable one at a time. It really helps to have a test CD with some pure sinewave tones. These can be had for as little as $10 in the stores. Second best is a CD with a very repetitious bass line. (Note: ACI includes a FREE setup CD with the purchase any ACI subwoofer.)

1) Set crossover frequency at 100Hz and adjust level to be easily audible. Using your test CD with a tone at about 100Hz or repetitious bass adjust phase switch for maximum output at the listening position. This is most easily accomplished with an extra person to throw the switch or adjust the knob.

2) Turn frequency and output controls all the way down. As you play music with a repetitious line, adjust the bass level upward until just consistently audible.

3) Turn frequency control up gradually until the bass seems full, then back it off just a bit.

4) Sit back and listen with a variety of music, play with only the level until it seems just right, you're just try to fill in the bottom so most likely the level control will be just barely on.

5) IF the music seems to lack warmth, try adjusting the frequency control up just a bit at a time. Too much, and the sub becomes easily audible by itself.

Additional considerations:

You'll never get it perfect for all music because the music isn't recorded consistently! If you try to use the sub to adjust for recordings that lack bass you'll go nuts, adjust to well recorded music and leave it alone.

• IF your main speakers have ports (vents) try stuffing them, this often improves the transition drastically.

• IF you have a separate amplifier, use the passive plug-in high-pass filters, they make major improvements.

The proper placement of speakers in your room has a major impact on sound quality. Because all of our rooms and tastes are different, it is impossible to specify a "correct" placement. Instead, let us present you with some acoustical facts, then you can optimize placement in your room.

It helps to visualize sound waves as behaving very much like water waves. The sound we hear is made up of two types of waves. Direct sound waves come directly from the speaker to our ears.  Reflected waves come to us after bouncing (diffracting) off the speaker enclosure itself, or walls, ceiling, floor or furniture. If you want to see how much these reflected waves affect the sound, move your speakers outside and hear the difference!

Sound waves come in different lengths; the lower the note, the longer the wave. Extreme low frequencies such as the lowest organ pedal notes are over 60 feet long!  The biggest problem with bass notes is the phenomenon we call standing waves. In effect the waves "pile up".  This creates big peaks and dips in the bass response. If you put a low frequency test tone through the speakers, you can walk around the room and find places where it is very loud, and places where you perceive virtually nothing.

Just as the room affects the bass response, so it affects the mid-treble sound of the system. In the mid-treble range, the sound waves are shorter and have peaks and dips, most of the affects (peaks and dips) occur from enclosure edges, furniture, walls, or the floor.   The shorter wavelengths of the mids and highs are more easily absorbed than the longer wavelengths of low frequencies. This is why a bare room sounds so harsh compared to a room with a lot of stuffed furniture, carpets, drapes, etc.

An ideal setup for sound would be achieved if you could:

• Choose a room with width, height and length dimensions that are not multiples of each other. (A cube is the worst!) Good numbers might be something like, height = 8 feet, width = 15 feet, and length = 26 feet.

• Choose a room that has an irregular shape, non-parallel walls cut down on standing waves.

• Place the speakers so that the woofer cones are at irregular distances to the floor, walls and ceiling. This can be difficult. Use a tape to measure the distance from the center of the woofer to the room boundaries. Move the woofers around till you have cut down on the number mathematic multiples. (You don’t want distances like 12 and 24", but more like 12 and 22").

• Use the distance from the woofer to the boundaries to increase or decrease bass output. Sticking the speaker in the corner or close to walls will give more bass output than putting the speaker out into the room. You can use this to get the best balance between bass output and upper range output. One of the advantages of using separate subwoofers is that you can place them in corners for best bass response, while keeping the main speakers out into the room for best mid-treble response and imaging. 

• Use absorbent materials to help smooth upper-range response and improve transient response and clarity. Why? Let’s take the sound of a bell for example. First you will hear the direct sound from the speaker. But some of that sound bounces from wall-to-wall, ceiling-to-floor, off furniture, etc. before it reaches your ears milliseconds later. Because the time difference is short, you don’t hear an echo, but the sound of the bell is stretched out from something like a "ding" to a "ddiiinngg".  

• Place speakers as far as possible from other furniture and room boundaries. Keeping the mids and tweeters away from the floor is particularly important.  Many speakers sound best when placed on sturdy stands to get the right listening height. 

• Use padded furniture and drapery when possible to cut down on reflections. Furniture has the added bonus of helping to break up standing wave patterns in the bass.

• Use a symmetrical placement of the speakers in the room. Of course the distance between the speakers is also important. In general, the further back your listening position, the farther apart should be your speakers. Think in terms of approximating an equilateral triangle.

• In most rooms you will want the main speakers placed between five and eight feet apart. Experiment! Too much distance will smear the image and it will seem like there is a hole in the middle. Too small a distance will compress the image. Experiment with facing the speakers straight into the room or toed in slightly toward the listener. For video applications the left and right speakers should be close to the edges of the screen.

Common causes of noise and intermittent problems:

• Dirty connections
• Poorly made terminals, inexpensive RCA jacks often fit poorly enough to cause a buzz or hum.
• Poorly terminated connections. Cold solder joints, loose fitting terminals
• Poorly shielded cables picking up noise from RF or house main electrical
• Cables picking up noise from AC extension cords. Move cables or cross at right angles

ACI, Sound that Satisfies...Since 1977