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Why Does Your Subwoofer Sound Weak?

Whether you like to crank your music up or keep it low as great background music, having a good sounding subwoofer is essential. No matter what kind of music you like, or how softly or loudly you like to listen, a quality subwoofer can really improve your overall listening experience.

If We had to name one of the most common issue with car subwoofers that we hear regularly, then it must be this; “Why does my subwoofer sound weak?”.

If that’s the case with you, there may actually be an underlying problem that you need to diagnose and fix. Most often, this problem is caused by something easy to fix.

So, before you decide to remove and replace a supposedly bad subwoofer, here are some of the most common reasons why a subwoofer sounds weak.

Why Does Your Subwoofer Sound Weak?

1. Is your subwoofer still new?

Do subwoofers require break-in? Great question, for which the answer is an emphatic “Yes”. Basically, like any other piece of equipment or machinery, subwoofers are made from moving parts, and when those parts are brand new, they can take some time to loosen up and become flexible enough to respond fully to the electric current from the amplifier that drives them.

For this reason, your subwoofer may not perform at its peak out of the box. So, if you’ve just bought a new subwoofer and mounted it in a box, give it some time (1 or two weeks of daily use), and you’ll definitely notice a slight change in sound after some period of break in.

2. Is your subwoofer underpowered?

You shouldn’t expect much from a subwoofer that’s underpowered. Under-powering your subwoofer isn’t necessarily a bad thing bad for the sub. Not giving it enough power just means that the music will sound weak and lack detail. So, always make sure your subwoofer isn’t underpowered.

It must be noted, however, that the danger is when that power is coming from an amplifier that’s being overtaxed, exhausted, or overworked and sending out a clipped signal. The latter is telling the voice coil to pop into a position and sizzle. It’s doing it with almost twice the power of the sub’s maximum capacity.

In other words, the clipped signal makes the subwoofer surpass its thermal or mechanical failure rate by doing things it’s not designed to do, which leads to it tearing itself apart, or overheating and eventually blowing out.

3. Are your subs wired out of phase?

If you have multiple subwoofers mounted in the same box, and they sound weak, you need to make sure they aren’t wired out of phase. The most common symptom of a subwoofer that is wired “Out of Phase” is loss of bass.

Essentially, a subwoofer that’s wired out of phase has it its positive (+) terminal connected to the negative terminal of the amplifier, and its negative (-) terminal connected to the positive (+) terminal of the amplifier.

When there are two subwoofers mounted in the same enclosure with both woofers facing the same direction and one of them is wired out of phase, the subwoofer that’s wired out of phase moves the opposite way. Think of it this way: one sub is pushing while the other is pulling.

This might not cause damage if identified soon after installation. However, it can wreak havoc at high power levels because the subwoofers are moving in different directions and the pressure inside the enclosure can allow the subwoofers to move too much and/or too little.

Subwoofers wired in phase

Excessive cone movement can cause the subwoofer to move outside of linearity and too little movement can prevent the coils from cooling off.

It is really simple to rectify this problem by tracing your subwoofer wire back to your amplifier, and make sure the (+) terminal of the subwoofer is connected to the positive (+) terminal of the amplifier, and that the subwoofer negative (-) is connected to the amplifier negative (-). This is also known as “Wiring In Phase” and it’s the more common type of wiring.



4. Is your subwoofer mounted in a bad box?

A bad enclosure can cause all sorts of problems you can think of starting with weak bass output, all the way up to subwoofer damage.

If you already have your subwoofer mounted in an enclosure, make sure you physically take the box out and carefully check all around it. If it’s leaking somewhere, you need to fix that sooner than later.

If you’re building an enclosure for your sub, carefully note the manufacturer’s recommended enclosure size and type.

Another important thing to take into account is to fully seal the enclosure using silicone caulk around the edge, over all of the box’s internal seals, and around the edge of the terminal cup.

It’s also highly recommended to use a mounting gasket between the sub and the box wood. A gasket is quite efficient at preventing air from leaking. Any leak in the box will significantly hurt output and accuracy.

If DIY projects aren’t your thing, buy a professionally pre-made enclosure (of the right size), and save yourself from the hassle of building one.

5. Is your amp any good?

Bass is much harder to amplify than the rest of the spectrum of sound — that’s the reason why you need large and beefy subwoofer amplifier that can work with a wide range of impedances, and have tone controls and filters specifically made to help reproduce bass.

This is especially true when you have multiple subwoofers wired in such a way that their overall impedance load is beyond the capabilities of the amplifier (also known as impedance mismatch).

A subwoofer amplifier that’s being overworked will introduce distortion in the form of clipping. Eventually, it’ll overheat and go into protect mode.

Clipping occurs when more power is required from an amplifier than it is able to deliver. Once the amplifier is pushed way too hard beyond its maximum limit, it becomes impossible to amplify the incoming signal without compromising its form. At this point, the signal is amplified but in a very distorted form. In technical terms, the sine output signal loses its rounded peaks and troughs because the highest and lowest points of the sound wave are cut — or clipped — off.

When the audio signal becomes distorted in this manner, not only does the sound suffer, your subwoofer can be damaged by clipping.

6. Did you use a good wiring kit & proper grounding?

To get the most out of your subwoofer(s), you need a good amplifier and a good wiring kit that meets the power and wiring needs of the amplifier. The wiring kit you use to install your amplifier are just as, if not more important than the amplifier itself.

To operate efficiently, an amplifier needs its power and ground wiring to be large enough to accommodate its demand for electrical current.

It goes without saying that an amplifier that’s isn’t getting the power it needs won’t turn on or won’t be able to make the output you want. It’s as simple as that.

Additionally, it must be noted that improper ground wiring is one of the biggest cause of amplifier problems. So, if your amplifier ground connection is loose, your amp may not function properly. You do not also want the ground wire touching paint or any preexisting nut or bolt.

To properly ground your amplifier, make sure the ground wire is attached to to a bare metal area of the car body, within eighteen inches of the amp’s location. The most common amplifier grounding locations in a vehicle are anywhere that has a bolt directly connected to the metal chassis.

Symptoms of a bad ground connection include but not limited to:

7. Did you check your RCA cables?

If, for some reason, your RCA cables become loose or have a lot of wiggle room at the amp, your speaker(s) and subwoofer(s) will sound weak, or cut in and out intermittently. This also holds true when the RCAs are dirty or have corrosion on them.

You might also want to open up the amplifier if possible (note it may void warranty) and check if the RCA solder joints are cracked or not, or if there are any leaks or burns on the circuit board. This is because sometimes the RCAs seem to fit snug but the problem is inside the case.

P.S: It is not uncommon for an RCA input jack solder connection to crack loose from the PCB.


8. Did you check the settings (crossovers, EQ, Bass boost ..etc)?

Have you checked the setting on your headunit. If everything seems to be good, revisit the menu settings on your receiver — you never know if someone might have accidentally changed it all. Make sure that the subwoofer’s output hasn’t also been adjusted down.

It goes without saying that you need to check your crossover – whether it’s built into the receiver or into the amp. A bad crossover setting could definitely make your subwoofer sound weak.

Furthermore, you want to check your equalizer settings. This may be elementary, but that doesn’t mean it’s not worth checking. Sometimes, elementary” problems such as checking the settings (eq, xovers, bass boost…etc) on the receiver are more crippling than any other kind. It never hurts to be thorough.

If Nothing Works, Consider Replacing Your Subwoofer

If you’ve tried all the solutions above and your subwoofer still sounds weak, or it powers on but won’t play a thing, then there’s a good chance that it is defective and needs to be replaced.

Before getting rid of it, it’s wise to hook up a second subwoofer (if you have any) to the amp to test if the latter is not the culprit. If the second subwoofer works and sound good, then it’s very likely the original is indeed bad.

Final Thoughts

If everything checks out right, including the subwoofer, I’m afraid you’re turning into a basshead without you even realizing it, or you’re going deaf. That’s the only things we can reasonably think of.

We can all agree that if you’re a basshead who is used to insane bass levels delivered by multiple power-hungry subs, a decent audio setup with a single sub won’t do justice to your ears. You’d feel like the subwoofer sounds weak, whereas it’s sounds great to non-bassheads.

Another explanation to this, is you’ve become complacent with your sound. At first it sounds loud, but after time your ears get used to it and at some point down the line you just notice it doesn’t seem to sound like it once did.

Alex Brown

Hey There, my name is Alex Brown, I'm an LA-based sound engineer with over 10 years experience installing, troubleshooting, and repairing commercial, automotive, and household sound equipment. I've installed highly competitive car audio systems, and everything from navigation systems to full car stereo systems, remote starters, alarms and beyond. I enjoy creating solutions and simplifying everyday needs. I also love helping people get great sounding gear, thereby, saving the world from bad sound one customer at a time.

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