How to Connect a Subwoofer to an Old Amplifier? — Guaranteed Methods to Try

Old electronics should not be automatically thrown away. In fact, you can use your old amplifiers for your modern system. However, if done the wrong way, it won’t work or might damage your new units in the process. Don’t worry, because our audio engineers will tell you how to connect a subwoofer to an old amplifier to prevent these issues using this guide. 

How Does a Subwoofer Work?

Before we dive into the connection, you must first get an idea of how a subwoofer works. Like regular speakers, subwoofers are split into two types. These types will be discussed further as we go along. 

First, let’s look at how a subwoofer works within your stereo systems. Subwoofers work well with the amplifier. It takes the low-level input signal and boosts it through the voice coil to the speaker cone. The cone delivers excellent sound quality output. A subwoofer is inside an enclosure working to support the driver and the components while reducing resonance.

A powered subwoofer or active subwoofer does all the things we mentioned inside its cabinet. One thing powered subs have that is not often seen in passive options is a low-pass crossover. The crossover will be set at a frequency. The subwoofer’s crossover frequency represents the limit at which the subs will kick in and take over the bass production. 

KLIPSCH 10inch Front-Firing 250w Peak Power Subwoofer

The low-pass crossover blocks higher frequencies from getting to your subs so that they can produce a more accurate bass sound. 

Don’t expect your subwoofer output to be as comprehensive in range as main speakers because a subwoofer speaker is meant to handle the low-frequency tones. To get ready for connection, you need some essential accessories for your speaker systems, such as RCA cables, speaker wires, and speaker level cables.  

You will notice speaker-level connections on your devices. On the back, you can see speaker outputs,  speaker level outputs, an RCA input or two for your RCA cable, and preamp output.

Types of Subwoofers

Most subwoofers are either passive or active, also referred to as powered subwoofers. Powered subwoofers have a built-in speaker amplifier and usually connect with RCA jacks. The passive subwoofers, on the other hand, are subwoofer speaker inside an enclosure that lack amp. Passive subwoofers require an external amplifier, as well. 

Monoprice Powered Subwoofer

Active subwoofers are common on the subwoofer market, and they are larger, heavier but create a very dedicated bass sound. A passive subwoofer for your audio system is usually smaller and lightweight because it lacks an internal amplifier.

Our audio team recommends active subs for those who want no fuss and passive subs for users who want customizability. Keep in mind that going for an active sub will limit your options if you want to build upon your system in the future, and passive subs will take more time to integrate.

You then have the front-firing and downward-firing subwoofers. The audio quality won’t be very noticeable unless you are an avid audiophile [1], but it can impact the placement flexibility. To go with your stereo system at the front of the room, a front-firing sub would work better. They will project the sound directly to you but need to be closer to home theater receivers (if there is one) and the rest of the setup.

There is one more category for various types of subwoofers, and it has to do with the bass enclosure. It doesn’t matter if you have a powered subwoofer or a passive one; the cabinet will affect your bass notes. The main types are either sealed or ported, sometimes referred to as vented.

Planet Audio AC10D car subwoofer

As the names suggest, a sealed subwoofer is airtight and ported, while vented ones have openings. The difference between the two types is sealed enclosures allow tighter and cleaner bass production with more detail, but it sacrifices the volume. On the other hand, vented subwoofers are louder but not as precise. 

(Want to know more about your sound device? Then, you should know the different parts of subwoofer here, as well)

Passive Subwoofer Inputs

Passive subwoofer inputs will depend on the one you have, but you can expect to find an RCA-type input jack and speaker terminals with this type. 

Differences Between Old and New Receivers

Our audio team finds that a receiver and amplifier work the same way. However, a receiver includes a radio section.

An amplifier is an amplifier, and regardless of its age, it should do the same job. To some extent, this is true. One huge difference that’s quite obvious when we compare an old amplifier to a new one is that modern home theater system receivers have output jacks. Vintage receivers and vintage amplifiers do not have a subwoofer output, prompting some users to get creative. 

A vintage amplifier is missing a subwoofer out, but what does it include? An older amp will have phono, aux, and tape deck inputs, with the second two as line-level inputs. A phono preamp output is only seen on some models, and only DJs would appreciate it since it is for turntables. 

black subwoofer speaker

What about the difference in construction? When it comes to a vintage receiver vs. a newer model, the quality is a standout feature. A vintage amp is usually of better quality as they were built to last. Unfortunately, newer amplifiers and receivers cost a pretty penny if you are to look for ones of comparable quality. 

Modern-day manufacturers create speakers and other products that are meant to be replaced within a few years. Because brands constantly come out with better integrations and technology, home stereo systems go through constant upgrades. 

Our team suggests pulling the trigger and going for high-end models since repair expenses could end up costing you more down the line. This includes purchasing speaker wires that are long-lasting as well.

Connecting an Old Amplifier to a Passive Subwoofer

What happens if you have a passive subwoofer? Our experts caution that the answer for how to connect a subwoofer to an old amplifier is more complex if you’re looking at a passive sub. As our team mentioned, a passive sub will have a low-pass crossover, which is needed to buffer the subwoofer outputs on your stereo or computer system and home theater receiver. The speaker outputs are located on the back of receivers.

Connecting an Old Amplifier to a Passive Subwoofer

If you don’t already have a low-bass crossover or are looking to upgrade to boost the sound quality, our audio team has some tips for you. You have to make sure the crossover matches the subwoofer to function correctly. What factor needs to match? The impedance rating.

If your subwoofer has a 2-ohm impedance, you will need to find a crossover with the same rating to work well with the other speakers. Once you have it, the connection with your receiver is simple. 

(For better connectivity, you can check our list of the best subwoofer cable here

Connecting an Old Amplifier to an Active Subwoofer

Depending on the type of subwoofer and amplifier you have, the process of how to connect a subwoofer to an old amplifier will be different. You can do this with an RCA low-level input or speaker-level inputs.

If you have an RCA low level on the unit in your home theater systems, look at how many there are on the back of your powered subwoofer. How to connect your subwoofer and old amplifier is simply plugging in the right ends into the corresponding RCA input ports. 

For those wondering what to do if you have a single RCA cable but two ports or vice versa, just look for a Y adapter. While you’re at it, you can also look into a line-level converter for good sound and tonal balance.

Onkyo HT-S3900 subwoofer

What is a line-level converter? It’s a small device that will connect to your speaker outputs from a vintage amplifier for connection with double or single RCA connectors, and it optimizes the signal voltage. 

The next option if you run into any issues with RCA connectors is to use your speaker-level inputs. Use the speaker wire to connect the matching speaker output ports on your vintage amp to the subwoofer. Look at the back of your subwoofer. If you can locate the speaker-level inputs, then great! The inner workings of your subwoofer will take care of everything else, such as speaker signal adjustment from the speaker outputs.  

Once you have your vintage amplifier connected to your powered sub, then you can sit back and enjoy great sound. 

Integrating Your Sub to a Stereo System

You can upgrade the audio of your stereo sound system if you pick the right ones. The bass sound provided by your subwoofer output will give the main speakers a boost they need for you to feel the difference in a surround sound movie. 

To work with your stereo speakers, you have to use the subwoofer’s high-level inputs. Connect your two devices via the output jacks to get the full force of the highs, lows, and mids from your speakers.  

(If you want to experience a powerful and strong sound, you can check our guide about how to get more bass out of yuor sub here

Setup and Placement

How to connect a subwoofer to an old amplifier isn’t just about the connection with the speaker wire and speaker cables; it’s about the setup and placement as well. Our expert engineers always suggest location options based on the type of main speakers or subwoofers you have. 

mixer and amplifier

You may need to play around with the setup by moving the various speakers and subs around, but make sure you are close to a power supply source. If your subwoofer is magnetically shielded, then you have more flexibility on where to put it. It can be close to the TV and primary speakers without interference. As our team said before, front-firing subs are best placed close to the central part of your sound system. 

Look at your entire setup. Where is your listening spot? Where is the TV? What type of bass do you want to hear? Downward-firing subs run the sounds along the floor, which would create deeper rumbles. Theoretically, if you were to place down-firing subs behind your seat, you will feel more vibration.

There is no surefire answer for ideal placement because it all depends on your speakers and sound systems. There are so many top-grade subs out there that are equipped with advanced audio technologies that can take the pressure off you. Room calibration technology, for example, will allow the sub to fine-tune itself. With the help of your external amplifiers for passive models, the subwoofer will detect its surroundings and optimize its settings. 

Subs can also work with proprietary audio-optimizing functions on your speakers and soundbars, such as different sound modes. Sound modes can be adjusted to accommodate the type of content and the environment. Standard audio modes subwoofers can work with: night, movie, news, music, and game modes. 

Samsung HW-KM36 subwoofer

You can count on your subwoofer to dial back the bass during night mode but boost it up in movie and music mode to help you experience the full potential of your content. 

A subwoofer can work well with large or small speakers and pair well with a vintage or modern receiver connected with RCA jack outputs. You will witness overall sound improvement to your speakers regardless of the size. This is a helpful note our team felt necessary to point out because the better sound isn’t limited to the speaker or subwoofer size.

Those with smaller living spaces can still enjoy enhanced audio through speaker outputs, RCA cables, and even LFE input where applicable.  

Surround Sound Setup

If you want a full surround sound setup, our team of professionals has some invaluable advice. Stereo receivers may not be the best to use with surround sound setups because they only allow the low frequencies to pass from the primary source. They have a rudimentary design, which doesn’t let these vintage receiver models separate what’s coming from the movie or music source. 

TCL Alto 7 subwoofer

This means using a subwoofer with a vintage receiver won’t give you accurate bass you can separate. Knowing this, our experts advise hooking up your passive or powered subwoofer to a new amp if you want surround sound.

Stereo Setup

If you just want a stereo setup, it’s more suitable to choose an old amp or a new model with a stereo mode. The sub’s placement will take some time to figure out in a stereo setup because the speakers only produce sound from the left and proper channels. Some stereo setups have a dedicated center channel for dialogue and speech enhancement.

Don’t worry if your home system is essentially stereo because audio equipment nowadays can come outfitted with compensations such as virtual surround sound. If you have such bonus functions in your home setup, then it increases the placement options for your sub and receiver. 

A complete surround sound system has at least five channels and one subwoofer. The key is to project sound in every way to create an encompassing experience. Since a stereo system lacks these advancements, you will need to be strategic with the placement. Doing so will help you get the most out of the speaker and bass signal.

(For an improve bass, you should also have more idea about setting up a subwoofer phase here

Conclusion

While you might have previously thought connecting a subwoofer to an old amp was impossible, you now know how to do it in a few easy steps. Using the LFE subwoofer output, RCA cable, the RCA input, and speaker level input and speaker output will give you the successful connections that function properly. You can now make use of your old equipment! 

Writer

Willie Greer
Willie Greer
Willie Greer is the founder of The Product Analyst. A cinephile, he has made it a personal quest to achieve the awesomest home theater possible. He now shares what he has learned through the years on the site, and has enlisted the help of tech-savvy colleagues in providing more insight about today’s most sought-after gadgets.