Muffled sound is a function of inadequate high-mid and high-frequency sound output (3kHz and above). The speakers sound as if they are in a closed box.
This can be due to one of several reasons;
- Obstructed sound waves
- Improper audio or EQ settings limiting high-frequency extension
- Low treble gain
- Mismatched speaker polarity
- A blown tweeter/high-frequency driver
- A bad capacitor in the high pass filter crossover
If the muffling is due to a software issue, apply the correct setting to fix the problem. Conversely, a blown high-frequency driver or bad cap needs replacing by you or anyone technically gifted.
Regardless, here is how to pinpoint why your speaker is muffled.
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1. Obstructed soundwaves
High-frequency sounds have short wavelengths that are easily absorbed or attenuated (lose energy) due to obstruction and distance making the response muffled.
This can be due to;
- Improper speaker placement
- Blockage of the speaker grill by debris, gunk, hairs, and so on.
For optimal performance, high-mid and high-frequency drivers are placed at about ear level with a direct line of sight between the listener and the speaker. This could be a soundbar, surround speakers in an Atmos setup, or any other speaker.
Don’t place the speaker in an enclosed space. As such, to place speakers behind a projector screen, ensure it’s acoustically transparent.
If your AirPods, headphones, smartphone, tablet, laptop, or TV speakers sound muffled, check for dirt and debris blocking the sound waves. Clear any blockage using a toothbrush and isopropyl alcohol if you are comfortable doing it yourself or get professional help.
2. Improper Audio & EQ settings
With improper audio settings on your source such as AV receiver, tablet, PC, and so on, the output may sound muffled.
Check the playback setting to ensure the treble gain is not set too low which can muffle the acoustic response. For an audio sink with a gain knob, turn it up by a few clicks to around 0 o’clock (midpoint) or higher.
Additionally, use a higher-quality audio format/codec or turn off EQ to see if the problem goes away. You might also need to recalibrate your receiver to level-match your speakers.
3. Mismatched polarity
Mismatched polarity reverses the phase of a speaker to the rest and cancels out certain harmonics. Some output is lost making the sound dull.
Ensure the +tive and -tive terminals at the output and speaker inputs are well connected.
4. Faulty hardware
If the high-frequency driver is blown, your speakers will sound muffled. Damage to the driver may be due to mechanical or thermal stress (heat) tearing the cone suspension or damaging the voice coil.
On a multi-way speaker, ensure all drivers are working as intended by closely listening to each or waving your hand in front of each to listen for variation in the output levels.
If a driver is blown get it replaced by a professional. DIY if you are good with solder and can get your hands on a replacement driver.
If the high-frequency driver has output but is low, a bad capacitor on the tweeter’s high pass filter (crossover circuit) may be degrading the signals before playback.
Some signs of a bad capacitor are;
- Leaking electrolyte,
- Browning and corrosion.
The capacitor should be tested for damage and replaced with a capacitor of a similar microfarad value (µF) but can have a higher voltage value.
To Wrap up
Assuming this problem is not limited to a single soundtrack/source, the above steps should get to the root of the problem for fixing.
This may be as simple as cleaning gunk and debris off the device or replacing damaged hardware, usually the driver or a crossover’s capacitor.
We hope this was helpful!