Nick and Vanessa Lachey are taking on a new hosting challenge in upcoming reality show, The Ultimatum."

With a daring social experiment, the reality show veterans are returning with a fresh type of dating show. Nick says that there's a "massive difference" between their new project and "Love is Blind."

"It's gonna sound weird, but the stakes almost feel a little higher in 'Ultimatum' because these are people who have been together for a period of time."

"The Ultimatum" follows six couples, only they're not meeting for the first time. Couples entering the show have been together already, and are on the brink of marriage. Well, at least they would be--if both of them were ready.

The series will feature couples where one party is ready to get married, and the other is not. Participants are given the eight week "ultimatum": either get married, or call it quits. As Nick describes it,

"The emotional anxiety in the room was like palpable, like you could feel it, it was an emotional roller coaster, and we were on it."

In an exciting twist, contestants will also get to pick another potential partner from the other couples, as a glimpse into another possible future.

Nick reveals that there was high tension between couples, and a lot of apprehension going forward.

"They're confronting whether or not to end that relationship or to take it to the next level. I think the emotions were a lot higher. Everyone on 'Love Is Blind' is so excited. They're all there for the same reason: They want to find love. So it was a different dynamic."

But Vanessa says the contestants aren't the only couples getting serious via the show. She confesses that she and Nick have been a lot "more vulnerable" as a couple while consulting the participants.

"We were more open with them. There were multiple dinners where we sat down and had a glass of wine with them and were just talking about the process and what we've experienced in our lives."

"The Ultimatum" premieres April 6 on Netflix.