For some readers, it might take a small leap of faith to consider needing speaker filters. This is not the first product that addresses the issue of noise intruding on speaker cables. Companies such as Shunyata Research, MIT, Transparent, Synergistic Research, and Bybee, to name a few, have addressed such noise, but, I believe, LessLoss has developed a novel approach.

On one end of each 11 3/4" (30cm) Firewall is a small, gold-plated, five-way binding post, and on the other end is a short section of LessLoss’s flexible C-MARC speaker wire terminated with either a sturdy silver-plated spade or BFA-style banana plug. Between these connectors is a 3 1/2" (9cm) clear cylinder of hard-cured epoxy resin that encases the actual Firewall conditioner, where the noise-reduction magic happens. That “magic” comes from some high-tech construction techniques coupled with proprietary materials and is based on LessLoss’s skin-effect filtering research. The signal runs through two pairs of aged-copper rods that are very soft and pliable. The copper used has not been through any extrusion processes that would add material stresses and is even more pliable than soft industrially annealed copper. LessLoss has developed a unique process for forming the copper rods that achieves the sonic properties necessary for the Firewall filters.

Surrounding each pair of rods is a grid formed by 3D selective laser metal sintering. The grid, which vaguely resembles the mesh plate in a vacuum tube, is built up in successive layers in an oxygen-free environment. LessLoss says that any oxygen entering the laser compartment will cause the material to explode. The LessLoss website has a number of pictures of technicians in clean-room suits producing the screen section of the Firewall. The copper rods and grid are encased in the clear epoxy body that serves three purposes: adding rigidity to the copper assembly, damping any vibrations near the filter, and protecting the delicate Firewall assembly.

LessLoss says that the Firewall can be seen as “kind of a micro-transformer, kind of a ferrite core, and kind of a directional set of A/C diodes.” They claim that it removes noise more efficiently than competing Zobel-style filters. When I asked LessLoss’s founder, Louis Motek, about the Firewall’s electrical capabilities, he noted that the copper in the Firewall is capable of handling even more current than his C-MARC speaker cables, so high-power amplifiers should pose no problems. Furthermore, there is nothing to wear out or deteriorate, so a Firewall should last a lifetime; I experienced no break-in changes during my listening. The Firewalls are directional, with color-coded markings for positive and negative posts. That is the extent of the directions for setup and use.

he best way for me to describe the Firewall’s main sonic effect is with a non-audiophile analogy. During the pandemic, I have spent a lot of time walking through my small town’s subdivisions and have enjoyed the calm, quiet streets. There is little traffic; just an occasional train whistle disturbs the peace. But on a warm September morning, my wife and I travelled south to the Missouri River and walked along the banks. The quiet was stunning -- no road noise, no trains, no people, just silence. But what I did hear was birds chirping, the rustling of the leaves in the wind, and the giggles of a pair of toddlers playing in the riverside park. My old ears were hearing things anew, in high-res. When I returned home that afternoon, I was shocked to discover just how loud and boisterous my quiet little town was by comparison.

A similar revelation occurred when I added the Firewalls to my system for the first time. By removing a previously unnoticed noise intruding on the music, there was now a quietness, a focus, a relaxation to the sound that was instantly recognizable, even when heard from another room. When I asked exactly what type of noise the Firewalls were reducing or eliminating, Louis Motek responded that the Firewalls “filter radio frequency interference on the speaker wires which causes intermodulation distortions in the audio range.” Consequently, they won’t reduce tube rush, tape hiss, ground loop hum, etc., nor will they remove noise inherent in poor recordings.

With the Firewalls installed, familiar recordings displayed newfound reverberation trails around instruments; treble notes were purer yet still exciting, and percussive attacks were quicker, with increased force. Instruments and voices that I had previously thought of as well reproduced by my system were now more truthful in timbre, their image placement on the soundstage was clearly drawn, and ambience was greatly enhanced. This last benefit was probably the most striking. Before installing the Firewalls, I had assumed that the treble range would be affected the most, but in my system the midrange also benefitted from the Firewall’s noise reduction.

Ana Caram’s Rio After Dark [Chesky JD28] is an audiophile and reviewer favorite, particularly the cut “Viola Fora De Moda,” for its numerous percussive notes spread across the width and depth of the soundstage. The entertaining sonic tinkles and jingles aside, Caram’s voice always seems a bit amorphous, with no real focus or image definition. With the Firewalls in place, her voice now occupied a distinct spot with believable size and shape, and was placed just a bit to the right of center. In addition, her delivery was more delicate, more vulnerable, with better recognition of lyrics. Paquito D’Rivera’s saxophone tone was also improved, with less metallic bite but with his characteristic brightness of tone. I could now easily follow his clarinet, which mirrors Caram’s vocals on “O Que Vier Eu Traco” and have a newfound admiration for his performance. Finally, David Chesky’s piano now sounded a bit more boxy and distant. It was also interesting to compare the room reverb of his piano performance with D’Rivera’s saxophone sound. The Firewalls revealed the saxophone’s reverbs as brighter and more prominent when compared to the mellower reverb tone following the piano.

When a product makes such an immediate and obvious difference in my system, I’m curious to hear if that is due simply to synergy with my gear or if the results can be duplicated in other systems. So I arranged to listen to the Firewalls in two friends' systems. The first was in the context of an all-vinyl listening session, which used a Koetsu Rosewood Signature Platinum cartridge on a SOTA Nova turntable. The Firewalls were connected to Cardas Golden Cross speaker cables and then to Verity Audio Parsifal Encore speakers, which were driven by Quicksilver V4 monoblocks. A bespoke David Berning preamp completed the system. To keep things simple, we played two cuts without the Firewalls, then the same two cuts with them installed.

The first tune was Eric Clapton’s “Before You Accuse Me (Take a Look at Yourself)” from Eric Clapton Unplugged [Reprise 468412]. Without the Firewalls, the Koetsu was certainly doing its thing, with big U-shaped soundstage, good pace, and the image of Clapton firmly planted between the speakers. After the Firewalls were installed, the applause at the beginning of the track had more definition, with individual claps apparent instead of a wash of sounds. The biggest difference was in Clapton’s voice. Without the Firewalls, he sounded like he was singing into a Shure SM58 mic (or any of the Shure’s competitors) that has a treble shelf from 2kHz through 10kHz to aid in intelligibility and vocal clarity. What sounded wrong to me was a bit of extra zip in the treble from this system that reminded me of the sound I associate with many house PA systems. The Firewalls eliminated the added harshness from his voice, but kept the treble true to the microphone’s sonic signature. The resulting sound was much closer to what I imagine is the recording’s true sound, more like listening to the feed from the mixing board and less like hearing it through the PA. This was a great improvement to an already fine system.

Paul Simon’s “Diamonds On the Soles of Her Shoes,” from Graceland [Legacy 88691914712], was the next track, and the Firewalls did a fine job of cleaning up the treble and improving the separation and clarity of Ladysmith Black Mambazo’s various vocalizations and harmonies. The most striking effect was on the unidentified percussion instrument, reportedly used to depict the sound of the “diamonds on the soles of her shoes.” Without the Firewalls, at the 2:10 mark in the cut, the scraping sound appeared in the left speaker but was lost in the densely scored background. After connecting the Firewalls, not only was the sound more clearly heard, but the improved clarity revealed that it also panned from left to right in a straight line. The system’s owner, Stu, got up and painted circles in the air describing the way the Firewalls separated singers and instruments. I agreed with that assessment and found that the Firewalls improved the focus and clarity for a clearer picture of the performers.

Two points came up in our discussion of the Firewalls. First, the reduction in grit in the treble might sound as though the treble had less presence or was less exciting, particularly over the long term. I certainly have known a few audiophiles who prefer a great amount of treble energy, but my personal preference is for smooth, fatigue-free treble. The Firewalls delivered full frequency response without dulling or blunting the leading edge of treble attacks, and that held true with every speaker I heard.

Second, the Firewalls do such a good job of separating instruments and voices in recordings that some listeners may actually prefer a more homogenous, blended soundstage. When we listened to “Diamonds on the Soles of Her Shoes,” the cut sounded a lot like a live performance before the addition of the Firewalls. But with the Firewalls, this track now sounded like a well-engineered studio recording with lots of layering and spotlighting of solo instruments. While I agreed with the sentiment of the other listeners in the room, I ultimately felt the Firewalls produced a more accurate representation of the recording, even if it changed the perspective.

The next stop on the LessLoss tour was a system using Merlin VSM-MM speakers connected with Acoustic Zen Hologram II speaker cables to Musical Design’s T-100 hybrid amp and Chameleon preamp. The source was a PC music server feeding an iFi micro iDSD Black DAC. On Lucinda Williams’s song “Protection” from the album Down Where the Spirit Meets the Bone [Highway 20 Records H2001], the owner, Chris, commented that the sound had improved from MP3 to high-res. That’s certainly an overstatement, but I knew what he meant, as the treble was considerably cleaner. He was particularly relieved to discover that a worrisome distortion in the guitar part was now shown to be emanating from the guitar amp used in the recording, not from some component in his system.

The other track used was from The Bahamas’ Earthtones [Brushfire/Island/Republic 5793564]. With the Firewalls installed, backup singers Robin Dann and Felicity Williams retained their great balance and blend on “Opening Act (The Shooby Dooby Song)," but there was greater differentiation between each singer, as a unique voice in the recording’s mix. While this album is not strictly an audiophile release, it is surprisingly good-sounding, and I’ve found that those background vocals sound remarkably realistic over the best systems. The LessLoss conditioners took this system up quite a few notches in that respect. Later that night, Chris texted that with the Firewalls removed, the tracks we had listened to had lost their "reference quality."

Over the next month, I tried the Firewalls with a wide variety of other speakers and speaker cables. Speakers tested were my Innersound Eros, a Lowther PM6A on an open baffle, Altec Valencia, and Magnepan LRS. In each case, the Firewalls improved resolution in the upper midrange and lower treble. I was able to follow complex musical lines more easily and have discovered new low-level information in material I thought knew very well. In that respect, I’m reminded of my first use of a jitter-reducing component between my CD player and DAC and discovering how much more information was heard from my CD collection.

The speaker cables I tried varied in construction from parallel multi-strand 16-gauge, to coax made specifically to work best with electrostatic speakers, a set of braided Litz cables, and even a vintage pair of MIT 750 Music Hose that have small spade terminals to fit the barrier-strip connections of older amps. While each cable has its flavor or signature, the Firewalls tended to make them sound more similar than different, an effect I find intriguing. Depending on my mood, I mostly favored the Litz wire and the MIT cables for their transparency and slightly richer tone, aided by the Firewalls’ improved treble and midrange.

LessLoss advises owners of biwired speakers to use two pairs of Firewalls, one for bass and one for treble. I briefly tried this arrangement on the Innersound speakers and felt it improved the bass attack, but this was not on the same level of the improvement gained by using the Firewalls on the panels alone. One other suggestion from LessLoss was that the Firewalls can be daisy-chained in series for even better performance, and that proved to be true. The soundstage grew deeper and wider, with the treble becoming even smoother and sweeter. Purchasing two sets of Firewalls might be an expensive proposition, but it produces an addictive result.

t might be tempting to call the LessLoss Firewall an accessory or tweak, but I think that term sells it short. It needs to be viewed as an important addition to an audio system, and it improved the sound of every speaker I used during the review period. Depending on the speaker-and-speaker-cable combination, the results varied from subtle to dramatic, but always musically significant, accompanied by greater resolution that extended well into the midrange. The LessLoss Firewalls ensured that I heard all the music my system was capable of. Even though I am generally happy with the sound I have, the inclusion of the Firewalls proved that some of my music was obscured by noise --obscured, that is, until the Firewalls were in use.