Inside the Model Four: A Conversation with KLH's Engineering Team

We spoke with KLH Audio chief engineer Kerry Geist and chief product officer Jordan Rapp to unpack the recently introduced Model Four's driver design, crossover philosophy and why acoustic suspension is still the secret weapon almost no one else is using.

Before we get into the conversation, it's worth revisiting the Model Four, which we introduced at High End Vienna in June 2026. A full-range, three-way floorstanding speaker built around an 8" pulp-paper bass driver, 4" pulp-paper midrange, and 1" aluminum dome tweeter at just 13 inches wide and 8.25 inches deep. That's roughly the footprint of your average printer.

But don't let the size fool you. Model Four has big speaker energy: commanding, controlled bass and a dedicated midrange driver that delivers crucial mid frequencies with a level of detail that a standard woofer-tweeter combo simply can't match. At $2,000 per pair, it's designed to bring genuinely refined audio into living rooms, lofts, and bedrooms alike—exactly the kind of listener-first thinking that has defined KLH since the beginning.

We wanted to know how it actually came together. So, we went to the people who built it. 

Model Four has a famous name to live up to. How much did the original factor into your thinking?

Kerry Geist: Honestly, the vintage Model Four doesn't have a lot in common with the new one. The new Model Four is really the kid brother of the modern Model Five. They share the same midrange and tweeter, and they're working from essentially the same crossover network. Even the front baffle dimensions are very similar. So how the sound develops and opens up in a room (what we call the "sound divergence") is going to feel very familiar if you've heard Model Five.

So, Model Four had a very specific trajectory in terms of how it sounds?

Kerry: Yes. The target from the beginning was the voicing of the Model Five. The physical reality of using a smaller woofer means there are going to be differences, there's no getting around that, but the tuning philosophy and the character of the speaker, that's consistent across the family.

Walk us through the crossover, we know the enthusiasts will be curious.

Kerry: We started with the Model Five crossover and adapted it. Each filter section uses two reactive components (inductors and capacitors) along with resistors to calibrate the individual drivers relative to each other. The tricky part is that those reactive components are very sensitive. Small variations in driver performance can throw the whole thing off.

With the Model Four, the woofer and midrange were no problem. The tweeter was another story. It took real work to integrate it properly with the midrange, and we had to make specific changes to that circuit to get it right. That's not a corner you can cut; it either sounds right or it doesn't.

Tell us about the woofer. Why this driver?

Kerry: The Model Four uses the same woofer as the Model Three. It's designed specifically for an acoustic suspension system, which matters more than people realize. It has a large suspension and a long voice coil to give it the displacement it needs at low frequencies. It also uses a flat-wire, large-diameter voice coil for power handling. This isn't a driver you drop into any enclosure and call it a day because it was designed to do this specific job within an acoustically sealed environment.

What does your listening and tuning process actually look like?

Kerry: I don't believe in drive-by listening tests. You need to spend real time with a speaker; different music, different listening levels, ideally more than one room. That's the only way to get a complete picture of how a loudspeaker is going to perform across different conditions. I'll usually evaluate several different network solutions, pick the most promising one and then refine it as I accumulate listening time. It's a slower process than people might expect.

What amplifier are you recommending for the Model Four?

Kerry: My standard answer for most speakers is 80 to 120 watts per channel into 8 ohms. At that range, with a quality amplifier, you're getting 80 to 90 percent of what the speaker can do. You can go higher, but you hit diminishing returns quickly. You can also go lower, and here's where Model Four surprised me. I was running it with a tube amp rated at 18 watts per channel during the voicing process and it was still engaging, still musical. That's a really good sign about the efficiency and the overall design.

Last question: what's the one thing about Model Four that you think is going to genuinely catch people off guard?

Kerry: The obvious choice here is acoustic suspension. Nobody else at this price is doing it. It's not a gimmick or simply a nod to our heritage for heritage’s sake, it's a technical choice that has immediately noticeable audible consequences. It still has a great reputation among people who know what they're listening for, and I think a new generation of listeners is going to understand why we still employ it when they try KLH Audio out for themselves. It’s what makes the placement flexibility of the entire Model Series as flexible as it is.