The Portable Hi-Fi Primer: Deconstructing Sound, Power, and Design

The world of portable high-fidelity audio is crowded and confusing. You’re faced with a wall of technical jargon: “True360 Sound,” “Peak Power,” “Passive Radiators,” and claims of “all-day battery life.” It’s easy to get lost, especially when you’re comparing a $100 utility speaker with a $700 piece of audio engineering.

How do you tell what actually matters?

Welcome to the primer. I’m here to act as your guide. Instead of just “reviewing” a product, we’re going to deconstruct one. We’ll use a fascinating example of high-end design, the Bang & Olufsen Beolit 20, as our “specimen.”

Why this one? Because it embodies the very concepts—and compromises—that define the entire premium portable market. This isn’t a sales pitch; it’s an education. By the end of this, you won’t just wonder if a speaker is “good”—you’ll know why it is, and you’ll be able to spot true quality in any audio device.

Let’s begin.

1. The Enclosure: Why Material is More Than Just Looks

Your first interaction with any speaker is tactile. You pick it up. Does it feel like a hollow plastic toy or a dense, inert object? This isn’t just about “premium feel”; it’s the first and most fundamental principle of acoustic design.

The Mentor’s Lesson: The Enemy is Resonance
The goal of a speaker is to produce sound only from its drivers (the “cones” that move). The cabinet, or enclosure, that holds them should be “acoustically inert”—meaning it shouldn’t vibrate, rattle, or add its own “color” to the sound.

When a manufacturer uses cheap, thin plastic, that plastic vibrates along with the music. This is called parasitic resonance, and it’s the primary culprit behind “muddy,” “boomy,” or “unclear” sound.

Case Study: The Beolit 20
This is where high-end design breaks away. The Beolit 20’s main chassis is built from anodized aluminum. This isn’t just to look good on an executive’s desk. Aluminum has an exceptionally high stiffness-to-weight ratio. It’s rigid. It resists vibration.

[Image of Bang & Olufsen Beolit 20 in Grey Mist]
(The anodized aluminum enclosure of the Beolit 20 provides an acoustically inert foundation, ensuring sound purity.)

This allows the drivers to do their job without the enclosure “singing along,” resulting in a much cleaner, more precise sound. When you see a speaker using metal,
high-grade polymers, or dense wood composites, you’re looking at a deliberate (and expensive) choice to prioritize sonic purity over cost. The contrasting vegetable-tanned leather strap is a nod to portability and tactile luxury, but the aluminum body is pure acoustic science.

2. The “Watt” Fallacy: Decoding Speaker Power

This is the single most confusing specification for consumers. You’ll see one speaker claim “240 Watts” and another, larger speaker claim “70 Watts.” What gives?

You’ve hit on the audio industry’s favorite numbers game. Let’s clear it up.

The Mentor’s Lesson: Peak Power vs. RMS (Continuous) Power
There are two main “wattage” numbers, and most companies only advertise the most impressive one.

1. Peak Power: This is the absolute maximum power the amplifier can output in a tiny, millisecond-long burst before it either distorts horribly or damages itself. It’s a nearly useless marketing figure.
2. RMS (Root Mean Square) / Continuous Power: This is the real number. It’s the measure of continuous, stable power the amplifier can deliver for a sustained period. This is what dictates how consistently loud and clear a speaker can play.

Case Study: The Beolit 20
This speaker is the perfect example. The manufacturer’s text advertises 240 watts of peak power. But if you dig into the provided data, the “Speaker Maximum Output Power” is listed as 70 Watts.

This isn’t a contradiction; it’s the lesson. The 240W number is the flashy “peak” figure. The 70W is the actual combined output of its amplifiers. Specifically, the Beolit 20 uses dual 35-watt Class D amplifiers.

Why Class D? It’s the secret to modern portable audio. * Old Amps (Class A/B): Like incandescent lightbulbs. They produce beautiful sound but waste most of their energy as heat. Terrible for a battery-powered device. * New Amps (Class D): Like LED bulbs. They are incredibly efficient (often 90%+) and run cool. They turn almost all the battery’s energy into sound, not heat. This means you get immense power and longer playtime from a small package.

So, when you’re shopping, ignore “Peak Power.” Look for RMS, Continuous, or (as in this case) the amplifier’s spec, like “2 x 35W Class D.”

3. The Bass-Bending Trick: Big Sound from a Small Box

“How do they get that much bass from that?”

It’s a valid question. Traditionally, to get deep bass (low-frequency sound), you needed a big driver (a woofer) and a big box. Physics demanded it. But in a portable speaker, you have neither.

The Mentor’s Lesson: The Magic of Passive Radiators
The solution is a clever piece of acoustic engineering called a passive bass radiator.

Imagine a drum. It has a drumhead you hit (the “active” part) and another one on the bottom that you don’t hit (the “passive” part). That bottom head vibrates in sympathy, using the air pressure inside the drum to create a deeper, richer tone.

A passive radiator is the same thing. It’s an unpowered speaker cone, or “diaphragm.” The “active” drivers (the ones powered by the amp) move back and forth, creating air pressure inside the speaker’s sealed enclosure. This trapped air pressure then pushes on the passive radiator, causing it to vibrate.

This “sympathetic resonance” allows a small, sealed speaker to reproduce low-frequency sounds that would normally be impossible. It effectively “tricks” the speaker into sounding much larger than it is.

Case Study: The Beolit 20
The Beolit 20 claims a stunning frequency response down to 37 Hz—that’s deep, rumbling bass territory. It achieves this by pairing its four active drivers with two passive bass radiators. This combination, driven by those 70W Class D amps, is what creates its famously powerful and room-filling sound.

[Image of Bang & Olufsen Beolit 20 from above, showing speaker grille]
(Beneath this grille, a combination of four active drivers and two passive radiators work to produce deep bass and 360-degree sound.)

This is also the source of the “True360 Sound” claim. By arranging the active drivers (specifically, a 5.5” long-stroke woofer, three 1.5” full-range drivers) to fire in multiple directions, the speaker creates an omnidirectional sound field, eliminating the narrow “sweet spot” of traditional speakers.

4. The Battery Life Paradox: The 8-Hour “Myth”

Here is the most common disappointment in portable audio: “The box promised 8 hours, but it died in 3!”

This isn’t (always) a lie. It’s a compromise rooted in physics.

The Mentor’s Lesson: Volume is the Enemy of Battery Life
A speaker’s battery claim (e.g., “Up to 8 hours”) is always tested at a “typical” or “moderate” listening volume—think 40-50% max.

This relationship is not linear. It’s logarithmic. * To make a sound perceivably “twice as loud,” you need roughly ten times the amplifier power. * Playing a speaker at 75% volume isn’t 25% harder on the battery than 50%—it’s exponentially harder.

Case Study: The Beolit 20
The spec sheet promises “8 hours of play… at typical listening volume.” However, customer data (from the provided [资料]) highlights a key review: “if you play this at 75% volume, which isn’t that loud, the battery life is below three hours.”

This user is not wrong. And the B&O spec is also not wrong. This is the portable audio paradox. You can have:
1. High volume
2. Long battery life

…but you can only pick one at a time. A powerful amplifier (like the 70W one here) that is being pushed hard will drain a battery with astonishing speed. This is true for all high-performance speakers. So, when you see a long battery claim, be skeptical. The real question is: “At what volume?”

5. The Modern Extras: Gimmick or Genius?

Finally, manufacturers pack in features to justify the price. Are they useful?

The Mentor’s Lesson: Separate Convenience from Quality
Let’s analyze three features from our case study.

1. Qi Wireless Charging: The top of the Beolit 20 is a wireless charger for your phone. Is this genius? It’s a convenience. But remember the battery paradox. You are using your speaker’s limited battery to charge another device. It’s a feature to be used sparingly, probably when the speaker itself is plugged in.
2. App-Based EQ (Beosonic): This is not a gimmick. This is a critical feature. Some users (as noted in the [资料]) find the default sound “too boomy.” The Bang & Olufsen app allows you to use a digital equalizer (EQ) to sculpt the sound. You can reduce the bass, boost the mids for podcasts, or brighten the treble. An EQ gives you control, letting you tune the speaker to your room and your taste.
3. Stereo Paring: This is the real path to Hi-Fi. You can wirelessly connect two Beolit 20s to create a true Left/Right stereo pair. No single “360-degree” speaker, no matter how expensive, can replicate the vast, immersive soundstage of a proper stereo pair.

[Image of Bang & Olufsen Beolit 20 in a lifestyle setting]
(Features like Qi charging and App-based EQ (Beosonic) bridge the gap between a high-performance speaker and a smart-home companion.)

The Takeaway: You’re Now an Informed Listener

You are no longer a “no-threshold” user. We’ve deconstructed the Beolit 20, not to sell it, but to learn from it.

You now know that: * Material matters: Anodized aluminum isn’t just for looks; it’s for acoustic rigidity. * Power is tricky: Ignore “Peak Watts” and look for RMS or the real amplifier configuration (e.g., 2x35W Class D). * Bass is engineered: Small speakers create big bass using “passive radiators.” * Battery life is a trade-off: All-day battery or high volume. Never both.

Whether you’re looking at a Bang & Olufsen or any other brand, you now have the tools to look past the marketing and understand the science. You can identify the intelligent design choices that separate a true Hi-Fi instrument from a simple noise-maker.