[One for Every Home] Highly Recommended Sound-Enhancing Processor: CLASSIC PRO Sonic Enhancer PEH2

The long-awaited new product from CLASSIC PRO, the PA brand produced by Sound House, has arrived: the sonic enhancer PEH2!

CLASSIC PRO / PEH2 Sonic Enhancer

Now, let’s take a closer look at the actual unit!

Its appearance is very simple.
It features a two-channel configuration, with the following controls on each channel:

• LO CONTOUR: Adjusts the amount of phase-corrected low frequencies
• ENHANCE: Adjusts the amount of phase-corrected high frequencies
• Level Meter: Displays the output signal level

The basic operating procedure is as follows:

1. Turn LO CONTOUR and ENHANCE all the way down
2. Set the IN/OUT switch to “IN” to activate the PEH2 effect
3. Gradually raise ENHANCE and listen for greater definition in vocals, snare drums, and other sounds
4. Gradually raise LO CONTOUR to adjust the fullness of the kick drum and bass

Simply put, all you need to do is slowly turn the knobs while listening and find the settings that sound best to your ears.

However, I imagine many of you may be curious about the term ‘phase-corrected’.
How does this differ from a conventional equalizer?

The PEH2’s LO CONTOUR and ENHANCE controls are different from a standard two-band EQ that simply changes the volume of the low and high frequencies.

Rather than just adjusting low- and high-frequency levels, they are designed to work on the phase relationships between frequency bands, helping refine the sound’s definition, clarity, and perceived attack.

What Is ‘Phase’, Anyway?

Phase describes the relative position of a periodic wave, expressed as an angle.

Even waves at the same frequency can have different phase relationships:

• 0°: The peaks of the waves align
• 90°: The waves are offset by one-quarter of a cycle
• 180°: The peaks of one wave align with the troughs of the other

Audio signals contain numerous frequency components, ranging from low to high frequencies. When the phase relationships between these components change, the attack, definition, and overall cohesion of the sound may be perceived differently, even if the volume of each frequency has not changed significantly.

For example, a kick drum sound contains the following components:

• Low frequencies: Body resonance and weight
• Mid frequencies: The core of the beater impact
• High frequencies: The click produced at the moment the beater strikes the drumhead

When these components come together in a balanced way, the kick sounds clear and defined, with a distinct attack. On the other hand, if the high-frequency attack gets buried in the low end, the sound may become rounded and indistinct.

The PEH2 helps refine this definition and cohesion by adjusting the amount of phase-corrected low and high frequencies.

How It Differs from a Conventional Two-Band EQ

The key difference is that a conventional EQ primarily adjusts levels at different frequencies, whereas the PEH2 adjusts the amount of phase-corrected low- and high-frequency components.

How It Sounds Different from a LOW EQ

Increasing a conventional LOW EQ boosts the overall low-frequency content, which can lead to the following issues depending on the settings:

• An excessive buildup in the low mids
• Overlap between the bass and kick drum
• A muddy or muffled sound

LO CONTOUR also increases the low-frequency level, so the same problems can occur if you turn it up too much. However, because the PEH2 also works with phase and timing differences on the low-frequency side, it tends to emphasize definition and punch rather than simply increasing the amount of bass, compared with a conventional LOW EQ.
In terms of what you hear, you may notice changes such as:

• A more clearly defined kick drum attack
• A stronger core to the bass sound
• Greater weight in the low end

How It Sounds Different from a HIGH EQ

Increasing a HIGH EQ generally produces the following changes:

• Increased high-frequency volume
• A brighter overall sound
• Greater audibility of hiss and sibilance
• A harsh or piercing sound if boosted too much

When you raise ENHANCE, the perceived timing relationships of the attack and harmonics also change, in addition to the increase in high-frequency level. This can produce the following effects:

• Clearer vocals
• More pronounced attacks from snare drums and percussion
• Improved perceived separation between instruments
• A sound that feels more forward in the mix
• A greater sense of depth and air

Rather than simply sounding like “there are more highs,” the effect is more likely to be perceived as “the cloudiness has lifted” or “the sound’s definition has become easier to hear.”

Why Does Phase Correction Change the Perception of Sound?

The sound of an instrument consists not only of its fundamental frequency, which determines its primary pitch, but also of multiple harmonics and attack components that shape the onset of the sound.

For example, with a bass sound, the mid-to-high harmonics and the components produced at the moment a string is plucked are just as important as the low fundamental when it comes to recognizing the pitch and definition.

As sound passes through speakers or filters, the phase relationships between these frequency components can change. This can make the sound seem blurred or its attack less distinct, even when the overall frequency balance has not changed significantly.

By adding phase-corrected low- and high-frequency components, the PEH2 helps refine how the fundamental, harmonics, and attack are perceived, bringing out greater clarity and presence.

We’ve covered quite a bit of technical information, but hearing is believing!
With that in mind, I’ve prepared three different demo comparison videos to help you hear the effects of the PEH2.

All three start with LO CONTOUR and ENHANCE turned all the way down. At their minimum settings, I first confirmed that switching between IN and OUT produced almost no change in sound quality or volume. I then gradually raised each control.

To make the differences easier to hear, I switch between IN and OUT partway through each video.
Be sure to listen and compare using headphones or speakers!

■ Rock

■ Acoustic Guitar

■ Beat

Impressions After Testing the Actual Unit

This is purely my personal impression, but I found that the changes became easier to hear with both controls at around the 1 o’clock position.

When the controls are turned all the way up, there are certainly times when the effect feels too strong.
That just goes to show how much adjustment range the unit offers.

However, when you compare IN and OUT after finding settings that sound pleasing to your ears, the difference is unmistakable.

Once you experience this effect for yourself, you might find it hard to go back to the sound with the PEH2 switched OUT—in other words, turned off!

Please note that raising LO CONTOUR and ENHANCE also increases the output signal level. Adjust the input level and the control knobs to prevent the CLIP LED from lighting up.

The PEH2 sonic enhancer makes it easy to take your sound to the next level and achieve a more impressive, exciting tone.

“The sound isn’t bad, but it still feels like something is missing.”

If that sounds familiar, this is a product I’d definitely encourage you to try.

It’s well worth keeping one in your rack, just in case!

Be sure to check it out!