Upscale Audio Gets Up and Outta Their Seats

How REL, Prima Luna and Klipsch Made Magic Happen on a Fall Afternoon


Kat from Upscale Audio jumps out of her seat

The following article is from Upscale Audio’s recent newsletter and blog to their customers. Upscale Audio does an excellent job of sharing their experiences with their customers. The short video captures Upscale Audio’s Kat Ourlian’s real-time reaction to hearing REL’s HT/1510 stereo pair subwoofers with Prima Luna EVO III and Klipsch Cornwall IVs.

About Prima Luna’s subwoofer out (and preamp outputs):  These represent something unique in our experience and are ideal for use with super high-efficiency speakers and RELs. Why? Because, in the case of 96-105 dB efficiency speakers, our High-Level Input will often see less than 1 watt of input.  This is insufficient to properly drive the REL High-Level Input to full output. While it works incredibly for normal speakers, including lesser Klipsch models, for those super high-efficiency models, it’s best to run through the Low-Level Inputs.

Oldtimers will point out that the following was sometimes done in designs from the 50s and 60s, but we haven’t seen this done in the modern tube era that began in the 80s. Prima Luna provides a low-level RCA-RCA output on their EVO III Integrated Amp and possibly their tube amps as well. Their circuit flows all the way through their amplifier, including their output stage, which includes the output transformers on tube designs. This means that when using their subwoofer outputs you can truly hear the full sonic signature of the entire system being fed forward into our REL. This helps create the synergy referred to in the article. Thanks, Prima Luna, for an awesome technique in achieving high-quality subwoofer outputs!

– John Hunter

One recent week, we were excited to welcome back into the store John Hunter (owner and lead designer) and Paul Magee (western regional sales manager) from REL Acoustics. They were there to conduct product training on the new HT/1510 Predator, but—and here’s the interesting part—specifically in a stereo-paired, hi-fi music setting.

What We Heard

John and Paul worked quickly in Demo Room #2 to set up a system with a PrimaLuna EVO 300 Integrated driving the Klipsch Cornwall IV, and a pair of REL HT/1510 Predators connected via the sub outs on the EVO.

These are beautiful subwoofers, looking machined rather than built. And once John hit ‘play’, those 15″ CarbonGlas drivers and 1,000 W amp joined the fray, inspiring all the breathless-reviewer cliches. We’ll spare you all but one: it was a profound display of—apologies for using this word—synergy. We came away with a new respect for the Cornwall IV, because the REL, like all great supporting acts, made us appreciate the Klipsch’s many skills without drawing attention to itself.

This lightning-quick speaker-sub combo was able to throw out a tremendous uncompressed wave of dynamic sound that conveyed all the brutality of the Nine Inch Nails track ‘Into the Void’ as if you were cowering inside the studio.

When things got quieter, those sensitive Cornwall horns conveyed all of the delicacy and nuance of another sensitive horn, the trombone of J.J. Johnson. The live jazz track presented so much depth that more than one of us thought the clatter of trays and glasses in the background was from our office break room down the corridor.

Paul ran the now familiar exercise of playing a track first with subs, then without, and then with again. With the subs, cymbals took on body and weight, images became even more stable and three-dimensional, and depth and height increased… we’re almost tempted to say “visibly increased” because it was all so immersive that the music actually left visual memories.

These improvements were heightened by just how well the three products worked together, pulling us so much into the deep tracks on an assorted test CD, that one of our passing colleagues walked in saying, “This is the first time I’ve willingly entered a room that’s playing Nickelback, it sounds that good.”

So why did this holy and unholy trinity work so well?

First, The Most Important Question

Why use a subwoofer designed for home theater (it’s even got HT in the name) in a music-only high-end system?

While REL has imbued the HT series with extra power and gain to give movie watchers the slam they need, these subs are still RELs. This means that the HT/1003, 1205, 1508 Predator, and 1510 Predator are designed as coherent, detailed, emotional, active loudspeakers that happen to cover only low frequencies. These are no bass bins; they work extremely well in music-first systems.

During the development of the HT/1510, REL realized that its characteristic high-gain and high-dynamic ability even at low volumes brought a tremendous benefit to users of high-sensitivity speakers such as the Klipsch Cornwall IV.

When an amp is driving a speaker with sensitivity in the high 90s and above, its output circuits are barely ticking over. The Klipsch Cornwall IV, for example, is rated (perhaps a smidge optimistically) at 102 dB sensitivity. Even our room-shaking Nine Inch Nails escapades would have run off barely three watts of power.

In these situations, a high-level sub output taken from the speaker taps of the amp will be a very small signal, one that requires a lot of subwoofer gain.

What John Hunter and the team found is that with the right low-level output on an amp, the HT/1510 is able to produce a lot of deep-bass support without needing to crank the subwoofer gain knob anywhere beyond 12 o’clock. This allows the sub to enjoy huge amounts of headroom even as it keeps up with sensitive horn-loaded speakers.

PrimaLuna Completes This Trinity, But Why?

We’ve mentioned that the type of low-level output from the amp is an important part of this Klipsch/REL pairing. The PrimaLuna EVO 300 and 400 Integrateds offer the ideal output because it is (1) full-range and (2) tapped from the output transformer. Think of it as a “high-level” or low-level signal.

1) Why Full-Range Sub Outs Are Good: The sub outs on some amps have a simple (cheap) low-pass filter, unceremoniously chopping off all content above, say 100 Hz, and sending this truncated signal to the subwoofer.

But, REL subwoofers come with extremely high-quality and carefully designed crossovers designed to critically filter a full-range signal, and pass through a bass signal for the sub amp without losing detail, speed, dynamics, and so on. You want this expensive crossover on the subwoofer to do all of the work.

2) Why The Origin of the Sub Out Matters: A low-level output can be tapped from many parts of an integrated amp, and often comes from the preamp circuit. PrimaLuna, however, sends both the headphone output jack and the subwoofer output RCAs a stepped-down signal from its output transformers. This means you are listening to the entire amp at both outputs. You have all of the magic of the small-signal tubes and the power tubes, giving the low-level subwoofer signal the same personality, and yes, the same quirks, as the high-level loudspeaker signal. This is how the HT/1510 was able to work utterly seamlessly in the room with the Cornwall IV.

Do you love the idea of a system that can be dreamy and ethereal but also leap across the room and grab you by the throat? Call your nearest REL and Klipsch dealer to set up a demo!

February 22, 2023 - Posted in: Deep Dive Setup