The A-PEN 68 Development ChroniclesVol. 4: Field Testing – The Bass Perspective

Around September 2024, we kicked off the field tests for the A-PEN 65. Interestingly, at this stage, the focus wasn't on Bream yet—it was almost entirely on Bass.

To be honest, I still wasn't 100% convinced about the "Chinu Top" (Bream topwater) scene. I had a feeling it might work, but I hadn't found that click yet. I was still in that restless, experimental phase.

By this point, we had finally successfully integrated the One-Knock Sound into the A-PEN 65. Despite the slender body, it produced a sharp, commanding tone while maintaining a respectable casting distance. I remember thinking, "For a lure this size, this is as good as it gets."

Then came early October 2024—a testing session that remains etched in my mind.

I had the opportunity to head out on the Yodo River with Mr. Motoki from Tsunami Lures. We took his Jon boat far upstream and spent the day working our way back down. It was pure, unfiltered fishing.

I brought along a handful of A-PEN 65 prototypes that had just been fitted with the new One-Knock system. I had several variations in my box:

• Silent models (No knock)

• One-Knock models

• Different tonal pitches and weight variations ranging from 5.9g to 6.7g.

I went in with zero expectations. I didn't know what the fish would do or which version would trigger a strike. I was just there to observe the water and see what happened.

We started the morning drifting with the current, searching with various topwater plugs. We threw everything from the Force Mix to the Zacrawl Yajirobee (crawler baits), trying to gauge the mood of the river.

Early on, I switched to the A-PEN 65 prototype, and it didn't take long. A violent surface strike changed everything.

"Wait... is this the pattern for today?"

I decided to commit to the A-PEN 65 to see if it was a fluke. It wasn't. The fish started hitting it with incredible consistency.

I have to be honest here: at that moment, I still didn't fully grasp why the One-Knock sound was so effective on Bass in a small profile. I kept telling myself it was just the timing or the specific conditions of the day.

But as the sun stayed up and the bites kept coming, the reality became impossible to ignore.

The combination of a small, "finesse" body size paired with a loud, aggressive One-Knock sound was the "on-switch" for these fish. The Yodo River had a slight stain to the water that day, and that acoustic presence was calling fish in from a distance.

By the end of the day, I had landed over 15 Bass, including a thick, 48cm (approx. 4.5lb) river beast. I actually stopped counting because the action was so fast.

Even Mr. Motoki was stunned, saying he’d never seen someone pull that many fish on topwater in the Yodo River. It was a legendary day. To top it off, Mr. Motoki landed a 50cm+ trophy on one of his own Tsunami Lures prototypes right at the end. Talk about a dramatic finish.

That day gave me the ultimate conviction: The A-PEN absolutely requires the One-Knock sound.

There is a specific power in the "Small but Loud" dynamic. The A-PEN 65 was compact enough to not intimidate the fish, but the sound gave it a presence that punched way above its weight class.

That gap—that contrast between a small profile and a strong acoustic signature—proved to be a deadly weapon.

Next Time: I’ll be diving deeper into the acoustics. "Vol. 5: The Difference in the A-PEN Sound"—why this specific noise changes the game.

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