Whether you’re a home audio enthusiast or a car audio hobbyist, subwoofers often evoke strong opinions and endless debates — especially when it comes to concepts like crossover and phase settings. With so much conflicting information floating around online and offline, it’s no wonder that even seasoned audiophiles sometimes misunderstand key principles. Thankfully, separating myth from reality isn’t as complicated as it may seem.
TLDR:
There are many myths surrounding subwoofer crossover and phase settings — but most stem from oversimplified rules or outdated advice. Proper crossover tuning depends on your speaker system, room acoustics, and subjective listening preferences. Phase alignment improves bass clarity, but not always in predictable ways. Debunking these myths helps you get tighter, cleaner low-end performance from your subwoofer setup.
Myth #1: Always set your crossover at 80Hz, no exceptions
Hands down, the most common subwoofer myth is that you should always set the crossover frequency to 80Hz. This figure is quoted so often that many people consider it sacred. But while 80Hz is a common starting point, it’s far from universal.
The 80Hz guideline originates from THX certification recommendations for home theater systems, where it balances directional audio cues and subwoofer placement flexibility. But the ideal crossover depends on:
- Your main speaker size and frequency response
- Your room acoustics and layout
- Whether you’re aiming for accuracy or preference-based tuning
For example, bookshelf speakers that begin to roll off around 100Hz may benefit from a higher crossover — say between 100Hz and 120Hz — so they aren’t left to reproduce bass frequencies they simply can’t handle. Conversely, floor-standing speakers may extend down to 40Hz or lower, in which case a crossover around 60Hz could be optimal.
Ultimately, the crossover point should blend the subwoofer and your main speakers seamlessly, not follow arbitrary numbers. Use room measurements or your own ears to guide you.
Myth #2: The subwoofer crossover knob is always the one you should adjust
If you’re using an AV receiver or home theater processor, chances are it has its own electronic crossover built-in. That means the subwoofer’s onboard crossover dial may actually cause double filtering if not handled correctly — or isn’t needed at all.
This myth persists because many users don’t understand how to integrate the two. In most setups, you should:
- Use the AV receiver’s crossover settings for precision control
- Turn the subwoofer’s crossover dial to its highest setting (e.g., 150–200Hz) or set it to ‘LFE’ mode if available, to effectively bypass its filter
This ensures that only the receiver decides what frequencies the sub sees. Otherwise, overlapping filters can muddy phase response and create uneven bass performance.
Pro Tip: Some gear offers an “LFE” input specifically meant to bypass its low-pass filter completely. Use this connection if you’re relying on an external crossover.
Myth #3: Phase switch? Just leave it at zero
Many subwoofers include a phase switch or dial — often giving users the choice between 0° and 180°, or offering full sweep adjustability between 0° and 180°. However, plenty of users either ignore this setting or leave it set to 0° by default.
Big mistake. Set incorrectly, subwoofer and speaker output can cancel each other out at certain frequencies — a phenomenon known as destructive interference. This causes dips in sound pressure at crossover frequencies, weakening bass instead of reinforcing it.
The goal of matching phase is to synchronize waveforms between your subwoofer and main speakers. When done correctly, you’ll hear tighter, more impactful bass and smoother tonal transitions.
How to check and adjust phase:
- Play a bass-rich track with consistent low-end (like some electronic or hip-hop music)
- Sit in your usual listening position
- Flip the phase switch or slowly adjust the phase dial — you’ll notice the bass become either hollow and weak, or full and tight
- Choose the setting that gives stronger and more coherent bass
When possible, use a microphone and measurement software such as REW (Room EQ Wizard) or app-based analyzers to visually measure in-room bass response and fine-tune phase adjustments.
Myth #4: Phase is only about time delay and nothing else
While phase certainly relates to time alignment between your subwoofer and main speakers, it’s not just about milliseconds. Acoustic environments introduce complex interactions due to room reflections, furniture, and boundaries.
You can align two drivers perfectly in phase in theory, but your room may cause phase shift anyway. That’s why simply calculating the difference in driver distances (and converting it into delay time) doesn’t always result in better bass.
Bottom Line: Use your ears, not your ruler. Even slight tweaks in subwoofer placement or phase angle can make a surprisingly audible difference. If you’re using a digital processor or DSP-equipped subwoofer, time delay and polarity options are worth exploring — but don’t fall into the trap of assuming numbers alone yield perfect results.
Myth #5: You don’t need phase control if you only have one subwoofer
False! Even with a single subwoofer, proper phase alignment improves integration with your other speakers. It’s not about syncing two subs — it’s about matching the sub with everything else.
Furthermore, modern living rooms and listening spaces often place subwoofers in non-ideal locations (like the corner, behind furniture, or off to the side), further complicating timing alignment. These locations may reinforce certain frequencies while canceling others out.
That’s why phase control actually becomes more critical when you can’t place your sub right in front of you or equidistant from your speakers. Try adjusting your sub’s phase manually or using delay settings to “pull” the sound into alignment at your seating position.
Myth #6: Measuring tools are overkill — trust your ears only
While it’s true that your ears should be the ultimate judge, measurement tools can dramatically speed up the process of fine-tuning crossover and phase settings. Subwoofer performance is very sensitive to room modes and boundary effects, which aren’t always obvious to the ear.
Simple tools like a SPL meter or room frequency app on your phone can already show you:
- Where nulls or peaks exist (bass drops or booms)
- How crossover blending behaves across the frequency range
- What impacts your phase adjustment actually has
For power users, software like REW combined with a calibrated microphone opens up advanced analysis — including group delay, phase graphs, and impulse response. These tools do not replace your ears but can verify what you’re hearing and pinpoint problems faster.
Conclusion: Ditch the rules of thumb, embrace the variables
Subwoofers are one of the most misunderstood components in audio setups — in part because they rely so heavily on integration. Crossover and phase myths persist because they provide easy answers to complex problems. But the true key to great bass isn’t choosing between 80Hz and 100Hz, or flipping a phase switch once and forgetting it. It’s about treating your subwoofer as part of a larger acoustic system that changes with every room, speaker, listener, and piece of music.
When you understand the why behind the settings, you gain control over the how. And with that kind of understanding, your bass can move beyond boomy and become beautifully balanced.