Hooking Up A Subwoofer To Bose Desktop Speakers

Adding a subwoofer to your desk monitors can drastically improve your listening experience, but it's important to set it up correctly. A subwoofer is a loudspeaker component designed to reproduce very low bass frequencies, typically around 20-120 Hz. By adding a subwoofer, you can extend the range of your system to reveal ultra-low frequencies that most monitors can't reproduce. However, if it's not calibrated correctly, a subwoofer can actually do more harm than good by throwing off the accuracy of your system with too much low-end. In this article, we will discuss the benefits of adding a subwoofer, the potential issues, and the steps you need to take to hook one up to your Bose desk monitors for an optimal listening experience.

Connecting the subwoofer to a power source

Most modern subwoofers are active, meaning they contain an internal amplifier that requires an external power source. Passive subwoofers, on the other hand, are slightly less common and require a good amplifier to power them.

When connecting your subwoofer, always use high-quality shielded cables to avoid noise, interference, and signal degradation. Additionally, use cables that are as short as possible to minimise these issues.

Connecting the subwoofer to the Bose desk monitors

Choosing the Right Subwoofer

Firstly, if the manufacturer of your Bose desk monitors offers a subwoofer designed for that specific line of speakers, that should be your first choice. This ensures the entire system was designed to work together harmoniously. However, if such an option is unavailable or impractical, try to select a subwoofer from the same brand as your monitors. This will still provide a decent level of compatibility and synergy between the two components.

Understanding Active and Passive Subwoofers

It is important to understand the difference between active (powered) and passive (unpowered) subwoofers. Most modern subwoofers are active, meaning they contain a built-in amplifier and require an external power source. Passive subwoofers, on the other hand, are less common in professional audio settings but can perform just as well when paired with a good amplifier.

Connecting the Subwoofer

The specific steps for connecting your subwoofer will depend on the model and the other components in your setup. Start by connecting the subwoofer to a power source if it is an active model. Then, locate the ports for external audio on your TV or monitor. These ports may be labelled as "out", "aux", "RCA", or with a headphone symbol. Use the corresponding cable to connect the subwoofer to these ports. If your TV or monitor lacks these ports, you may need to use a converter.

Optimising Subwoofer Placement

The placement of your subwoofer can significantly impact the sound quality. While lower frequencies are less directional, allowing for more flexibility in placement, it's important to keep the subwoofer away from walls and corners as they can distort the frequency response and increase the volume. Generally, anywhere on the floor near your desk should be suitable.

Setting the Crossover Frequency

Refer to the technical manual for your Bose desk monitors to locate the frequency response graph. This graph will show the range of frequencies in which your monitors are most effective. Set the crossover frequency of your subwoofer just before the response starts to drop off, typically between 20Hz and 100Hz. This ensures a smooth transition between the frequencies handled by the monitors and the subwoofer, creating a cohesive and balanced sound.

Fine-Tuning the Subwoofer Output Level

Use acoustical measurement software, such as Fuzzmeasure or RoomEQWizard, to fine-tune the output level of your subwoofer. This software will allow you to make adjustments and measure the frequency response, helping you achieve a flat response. If you don't have access to such software, you can rely on your ears and adjust the subwoofer's level until the bass sounds full yet realistic, blending seamlessly with the output from your monitors.

Setting the crossover frequency

Most modern AV receivers will automatically assign the proper crossover frequency based on the capabilities of your loudspeakers. It is generally recommended to leave these settings as they are. However, if you're using an AV processor, preamplifier, or a DSP subwoofer to adjust the crossover frequency manually, here are some tips to optimise performance:

• Ensure all your speakers are facing the same direction so that you can judge the quality of the sound.
• If you know your speaker's frequency range, set the crossover point roughly 10 Hz above the lowest frequency your speakers can handle cleanly. For example, if your speaker's lowest frequency is 70 Hz, set the crossover to 80 Hz.
• If you don't know the frequency range of your speaker, use a subwoofer matching tool, such as the SVS Subwoofer Matching Tool.
• Listen for a smooth transition between the subwoofer and the speakers. The blending should be seamless, with the bass and LFEs playing in unison with the speakers.
• If there is a bass bump at the crossover frequency, adjust the volume control to match the output of your main speakers.

The most common crossover frequency recommended (and the THX standard) is 80 Hz. However, this may vary depending on the type and size of your speakers. Here are some general guidelines for speaker/subwoofer crossover frequencies:

• On-wall or compact satellite speakers: 150-200 Hz
• Small centre, surround, or bookshelf speakers: 100-120 Hz
• Mid-size centre, surround, or bookshelf speakers: 80-100 Hz
• Large centre, surround, or bookshelf speakers: 60-80 Hz
• Very large centre, surround, or bookshelf speakers: 40-60 Hz
• Tower speakers with 4"-6" woofers: 60 Hz
• Tower speakers with 8"-10" woofers: 40 Hz or Large/Full-Band

Fine-tuning the subwoofer's output level

Understanding the Science of Sound:

Start by grasping the science behind sound reproduction. Subwoofers are designed to reproduce low-frequency sounds, typically around 20-120 Hz, which includes the deep basslines in songs and the rumbling effects in movies. The challenge with low-frequency sounds lies in their longer wavelengths, which can be as large as the room itself, leading to inconsistent sound quality and dead spots.

Acoustical Measurement Software:

Utilize acoustical measurement software, such as Fuzzmeasure or RoomEQWizard, to fine-tune the subwoofer's output. These tools allow you to measure and adjust the subwoofer's settings empirically, ensuring a flat response. By playing test tones and making adjustments, you can achieve a balanced sound across all frequencies.

Reference Tracks and Adjustments:

If you don't have access to acoustical measurement software, a more manual approach involves listening to a variety of reference tracks and making adjustments accordingly. Play a range of songs with different bass levels and adjust the subwoofer's output until each song sounds full yet realistic, without excessive bass. This process ensures that your audio system delivers an accurate and natural listening experience.

Phase Cancellation Considerations:

Be mindful of phase cancellation issues, which can cause certain low-frequency sound waves to cancel each other out. If you notice a reduction in bass or other anomalies, your subwoofer may be experiencing phase cancellation due to its placement. Many subwoofers have a phase inversion button, or you can use a specially wired cable, to counteract this effect.

Crossover Frequency Settings:

Ensure that you've set the crossover frequency correctly. The crossover frequency determines where the subwoofer's output ends and the speakers' output begins. Refer to the technical manual for your monitors and look for the frequency response graph. Set the crossover frequency just before the response starts to drop off, typically between 20Hz and 100Hz. This prevents a muddy or distorted sound caused by overlap with the speakers.

Room Acoustics and Treatment:

Consider the acoustics of your room and apply appropriate acoustic treatment. The placement of your subwoofer in relation to walls and corners can affect its frequency response. Additionally, invest in acoustic panels and diffusors to effectively absorb and diffuse bass frequencies. The SOS Guide to Control Room Design is a valuable resource for understanding acoustic treatment options.

Polarity and Smoothness:

Experiment with the polarity switch positions on your subwoofer to determine which setting provides the strongest bass and the smoothest transition at the crossover region. This adjustment can help optimize the overall sound quality and ensure a seamless blend between the subwoofer and speakers.

By following these steps and making adjustments based on your specific setup and room acoustics, you can fine-tune your subwoofer's output level to achieve a clear, powerful, and immersive sound experience. Remember that every room is unique, so take the time to experiment and find the optimal settings for your audio system.

Desk and main speaker monitor placement

The placement of your desk and main speaker monitors is crucial to achieving optimal sound quality. Here are some guidelines to help you get the best listening experience:

Speaker Placement

• Distance from the Computer Monitor: Place the left and right speakers an equal distance from the centre of your computer monitor or screen. They should typically be between 18 and 32 inches apart.
• Avoid Obstructions: Ensure that there are no objects directly in front of the lower part of the speaker grilles, as this is where the speaker driver is located.
• Position Relative to the Screen: Avoid placing the speakers too far behind your computer monitor or screen to prevent blocking the sound. The front of the speakers should be even with, or slightly forward of, the front of the screen.
• Control Pod Accessibility: Place the control pod within easy reach for convenient adjustments.

Desk Setup

• Magnetic Interference: The bottom of the speakers may emit a magnetic pattern. Avoid placing them directly on top of hard drives, storage discs, magnetic tape, or other media to prevent potential damage.
• Speaker Stands: If your desk space is limited, consider using speaker stands to position the speakers optimally. This also helps to fine-tune the speaker placement.

Monitor Placement

• Formation of Equilateral Triangle: Ideally, your listening position and the two monitors should form an equilateral triangle. This means that the distance between the left and right speakers and the distance from each speaker to the back of your head should be equal.
• Height of Tweeters: Adjust the height of the tweeters to be at the same level as your ears when seated, typically about 47-55 inches (120-140 cm) from the floor. If needed, tilt the speakers slightly downwards while ensuring they don't topple over.
• Speaker Direction: Point the monitors directly at your head, or slightly behind it, to achieve the best sound quality.
• High-Frequency Content: High-frequency sounds are more directional, so ensure the tweeters are pointed directly at your ears for accurate imaging.
• Speaker Isolation: Use speaker isolation pads to decouple the speakers from the desk surface. This helps to mitigate vibrations and resonances by absorbing them before they transfer to the furniture.

Subwoofer Placement

• Flexibility in Placement: Subwoofers are non-directional, so their placement is less critical. However, it is important to find a good location for optimal sound.
• Listening Position Technique: A technique to find the ideal location is to temporarily place the subwoofer in your listening position and then crawl around the room to identify where the bass sounds the best. Mark that spot and place the subwoofer there.
• Cutoff or Crossover Frequency Control: Adjust the subwoofer's cutoff or crossover frequency control to match the bass roll-off of your main monitors, referring to the user guides for optimal settings.
• Consider Multiple Subwoofers: If you experience localisation of a single subwoofer, consider using two subwoofers placed below the main speakers to create a multi-way speaker system.

Frequently asked questions