Usage: Alto TX12S and TX18S Subwoofer User Guide

Content

Overview

The TX12S and TX18S Subwoofer are powered low-frequency speakers designed to add deeper bass to live sound, rehearsal spaces, and small-to-medium performance systems. The TX12S and TX18S Subwoofer is a good fit for users who want simple controls, flexible signal routing, and easy integration with full-range loudspeakers.

The TX12S uses a 12-inch woofer, while the TX18S uses an 18-inch woofer for greater low-end output and deeper extension. Both models share the same 900-watt peak Class D amplifier platform, rear-panel EQ controls, and a 36 mm pole socket for mounting a loudspeaker above the sub.

Specifications

Model options: TX12S and TX18S
Amplifier power: 900 watts peak, Class D
Max SPL: 126 dB
Low-pass filter settings: 80 Hz, 100 Hz, 120 Hz
Polarity control: 180° phase inversion
Inputs: XLR/TRS combo inputs, with line input via TRS
Thru outputs: XLR
Mounting: 36 mm pole socket
Power: standard IEC cable, 100–120 VAC or 220–240 VAC, 50/60 Hz
Consumption: 500 W
TX12S frequency response: 46 Hz to 115 Hz (-3 dB)
TX12S driver: 12-inch woofer with 2-inch voice coil
TX12S size: 20.0 x 15.9 x 15.9 in. / 510 x 405 x 405 mm
TX12S weight: 49.3 lb / 22.4 kg
TX18S frequency response: 36 Hz to 115 Hz (-3 dB)
TX18S driver: 18-inch woofer with 3-inch voice coil
TX18S size: 23.0 x 23.0 x 23.0 in. / 585 x 585 x 585 mm
TX18S weight: 87.7 lb / 39.8 kg

Detailed Description

The TX12S and TX18S Subwoofer uses a simple rear-panel layout that makes setup straightforward. The input section accepts left and right signals, and the matching thru outputs let you pass audio on to full-range speakers without needing extra routing gear.

The Volume knob controls the subwoofer output level, while the Signal/Limit indicator gives quick feedback on system activity. Green indicates signal presence, flashing at lower levels and remaining solid at higher levels. Red indicates limiter or protection activity, which is a sign to lower the source level.

The LPF button lets you choose the crossover point that best fits your main speakers. The voicing control switches between Music and Live settings, letting you shape the low-end character for different performance needs. The Polarity Reverse button helps correct bass cancellation when the sub and main speakers interact poorly in a room.

The cabinet is internally braced and finished with a metal grille, giving the sub a durable build for regular transport and live use. Both models also support pole mounting, which is useful when creating a compact, vertical speaker stack.

Safety

Follow proper mounting practices when using the TX12S and TX18S Subwoofer with a pole-mounted loudspeaker. The pole must be rated to support the weight of the speaker on top, and the subwoofer should always sit on a flat, stable surface that can handle the full load.

Do not mount multiple loudspeakers on the same pole, and inspect the subwoofer, pole, and hardware before every use. In outdoor or windy conditions, avoid attaching banners or similar items that could catch wind and destabilize the system.

Keep cables clear of walkways so performers and crew do not trip and pull the speaker system over. If you are not confident handling the weight of the subwoofer or mounted loudspeaker, get help during setup.

Never connect the subwoofer to power while the grille is removed. For the TX18S, optional caster installation is the user’s responsibility, and only properly rated 3-inch casters with the correct M6 x 1.0 mm insert fit should be used.

High sound pressure levels can damage hearing. When the system is operating loudly, hearing protection is recommended to reduce the risk of permanent hearing loss.

Setup and Operation

Before powering the system, lower the output levels on your audio source and processor. Set the TX SUB volume to minimum, power on your loudspeakers, then bring up the mixer levels and raise the subwoofer volume to the desired listening level.

When shutting down, reduce the TX SUB volume first, switch off the subwoofer, and then power down the source devices and processors. This sequence helps avoid pops, thumps, and other unwanted noises.

For a basic system with one subwoofer and two loudspeakers, send the left and right mixer outputs to the subwoofer inputs, then route the subwoofer thru outputs to the loudspeakers. For a system with two subwoofers and two loudspeakers, each speaker can receive a mixer output, with each speaker’s mix output feeding a subwoofer input.

On the rear panel, the power input accepts the included IEC cable, the power switch turns the unit on and off, and the fuse compartment provides access for replacement with the same fuse rating printed under the switch.

The LPF control offers 120 Hz, 100 Hz, and 80 Hz settings, making it easier to match the subwoofer to different top speakers. The voicing modes are Music for a stronger low-end lift and Live for a tighter response with extra emphasis around the kick and bass range. The polarity switch can be tested by listening to bass-heavy material and selecting the setting that sounds fuller and louder in the room.

Cleaning and Maintenance

Keep the cabinet, grille, and rear panel free of dust and debris, and inspect the unit regularly for wear or damage before each use. If the fuse fails, disconnect the unit from power before replacing it with the correct type and rating.

Troubleshooting

If the Signal/Limit light stays red, the input level is too high and the source should be reduced. If audio is missing from the thru outputs, confirm that the correct left and right input channels are connected and that the mixer routing matches the intended speaker layout.

If the system sounds thin or the low end seems to cancel out, try switching the polarity setting to the other position. If unwanted thumps or clicks occur at power up or shut down, repeat the recommended power sequence for the source devices, loudspeakers, and subwoofer.

If the unit does not power on, check the power cable, power switch, and fuse. A blown fuse should only be replaced with one of the same rating.

Warranty

The included safety and warranty documentation applies to the TX12S and TX18S Subwoofer. Refer to that documentation for the coverage terms provided with the product.

Pros & Cons

Pros: Flexible crossover settings make it easy to match with different main speakers.
Pros: The voicing modes help tailor bass for music or live performance use.
Pros: XLR thru outputs simplify daisy-chaining to loudspeakers.
Pros: The TX18S adds deeper extension and a larger driver for bigger low-end output.
Cons: The TX18S is significantly heavier and less portable than the TX12S.
Cons: Caster mounting for the TX18S requires separate hardware and careful screw selection.
Cons: High-output operation requires attention to gain staging and hearing safety.

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Faqs

What is the correct power-up sequence for the TX12S and TX18S subwoofer system?

Use the proper power sequencing to avoid pops, clicks, and other unwanted noises. First, turn down the output controls on your mixer or source devices, then set the TX subwoofer volume to minimum. Power on the loudspeakers next, start playback, and slowly raise the subwoofer volume to a comfortable level. When shutting down, reverse the process by lowering the subwoofer volume, switching the subwoofer off, and then turning off the source devices and processors.

How do I connect the TX12S or TX18S to a mixer and loudspeakers?

The subwoofer provides left and right channel inputs on combo jacks that accept XLR, TS, or TRS connections, depending on the signal type. You can feed the mixer outputs into the subwoofer first, then send the Thru Outputs to your main speakers. In a two-subwoofer setup, each sub can receive its own mixer feed, with the Mix Output routing onward. This layout helps simplify cabling and keeps low frequencies controlled.

Which rear panel controls should I adjust first when dialing in TX subwoofer sound?

Start with the Volume knob at minimum and confirm the Signal/Limit light is behaving normally. Then choose the Low-Pass Filter setting that best matches your speakers and room: 80 Hz, 100 Hz, or 120 Hz. After that, pick a voicing mode between Music and Live, depending on whether you want a fuller low-end or a tighter kick-and-bass emphasis. If bass sounds thin, also test the polarity reverse button.

What does the Signal/Limit LED mean on the TX12S and TX18S?

The Signal/Limit LED gives quick feedback about input and output status. Green means the subwoofer is receiving signal; it may flash at lower levels or stay solid when the level is stronger. Red indicates output limiting or protection has engaged. If the red light stays on continuously, reduce the level from your audio source or mixer. That usually restores cleaner output and helps prevent distortion or stress on the system.

How do I know whether to use Music or Live voicing on the TX subwoofer?

Music mode is the better choice when you want a more pronounced low-frequency character for general playback or DJ use. Live mode is designed to be a little less extreme in the deepest lows while giving extra emphasis in the 60 Hz to 80 Hz range, which can help kick drum and bass guitar stand out. The best setting depends on the room, the main speakers, and the type of material you are reinforcing.

When should I use the polarity reverse button on the TX12S or TX18S?

Use polarity reverse when the subwoofer seems to cancel low-end output instead of reinforcing it with your main speakers. Play program material with steady bass, listen with polarity in one position, then switch it and compare the result. Choose the setting that sounds fuller and slightly louder in your room. This adjustment can make a big difference when the sub and tops are placed in a way that causes phase interaction.

What safety precautions matter most when mounting a loudspeaker on the TX12S or TX18S pole cup?

Make sure the subwoofer sits on a flat, level, stable surface before mounting anything above it. Use only a pole that is rated to support the loudspeaker’s weight, and do not mount multiple speakers on the same pole. Inspect the cabinet, pole, and hardware before each use, and keep cables clear of walkways. In outdoor or windy conditions, avoid attachments that could catch wind and tip the system.

How are casters attached to the TX18S, and what should I watch out for?

The TX18S includes rear inserts for optional caster installation, which can make transport easier. Use casters with the specified mounting pattern and weight rating, and follow the caster maker’s instructions closely. Do not reuse the screws supplied with the subwoofer for caster mounting; use hardware that is appropriate for the M6 inserts. Because caster installation affects stability, make sure the cabinet remains secure before moving or using it.