Chassis Resonance Control

It is estimated that 30–40% of an audio system’s distortions come from unwanted resonances from both within the component, via mechanical feedback and from airborne vibrations. Removing or reducing these unwanted resonances results in a more transparency with more fine detail resolution; high frequencies become more natural, and soundstage and dynamics are increased.

The Nimbus Assemblies consists of two Couplers either side of an high density aluminium Spacer. This we call a ‘footer’. This is placed under the chassis of a piece of audio equipment in intimate contact with the bottom surface, avoiding the existing feet and any bolts. Clearly a minimum of 3 ‘footers’ is needed but more enhances the effect. Four, or even five if you can managed them, gives further improvement to the sound quality.

The Coupler part of the ‘footer’is the heart of the HRS technology. This is a highly researched polymer compound which is broadband resonance absorber. This totally absorbs vibration and noise at the point of contact - hence is more efficient that other metal products that rely on transferring the energy to another part of the footer but do not actually deal with this unwanted resonance.

Most of the chassis resonance is created by the transformers present in all electronic components. These unwanted resonances create noise within the circuit boards and are heard as distortions. Placing the Nimbus assemblies against the chassis completely removes these resonances. The Nimbus Assemblies also completely stops any structure borne vibration coming through the support system via acoustic feedback at that point. Most equipment supports still "leak" bass energy back through the shelves. 

The effect on the sound of the equipment is immediately apparent. As with the Isolation Bases described above, the result is one of a far more transparent sound, less high frequency distortion ("fizz"), and a quieter (blacker) background. Lower noise floor results in a bigger sound stage, a more natural, less "hi–fi" presentation and low level detail much more easily perceived.

Because HRS products work in a different way to other isolation feet such as Stillpoints, Pulsar Points or even Cera-products from Finite Elemente, they produce a much cleaner, more natural sound due to a very obviously lower noise floor. These other mechanical devices rely on transferring unwanted resonances from one side to the other. This resonance has to go somewhere and far too often it remains within the support system, and can come back as reflections. These alternative devices rely on a steel or ceramic ball to transfer energy, and this can, of course, go both ways. Hence the control of structure borne energy - ie feedback from the bass energy generated by loudspeakers, cannot be totally successful. The HRS footer uses two polymer barriers to vibration energy transfer and removes it completely at point of contact. Hence it is more efficient and complete. in terms of removing mechanical noise.

These ‘footers’ work incredibly well under turntables too.

The Damping Plates are designed to be placed on the top plate of a piece of electronic equipment. These damp and absorb unwanted resonances from airborne vibrations generated by playing music that excites the room. Even at modest volume levels, this feedback loop is there. A quick trial with these damping plates produces remarkable audible improvements to the sound. There are 3 sizes, and two thicknesses available which will work with almost any chassis. One Damping Plate will produce a good result but, if the area is big enough, up to three pieces will give further improvements.

The Nimbus Assemblies and the Damping plates are designed as a total system. The best results are obtained if you ‘sandwich’ your equipment with Nimbus Coupler/Spacers and the Damping Plates. There is no benefit from just using one part over the other. Once heard you will not be able to listen to your system without them. Do not forget to treat separate power supplies; this is usually where the transformer and associated circuit boards reside.

One customer who tried the HRS items against his existing Stillpoints reported:

Great and essential stuff. I always believed the flaw in the Stillpoints sound was due to a cabling problem... It's not funny how you can go wrong in audio land and may end up compensating for the wrong kind of tweaks in my system... Also surprised by how effective they (HRS Nimbus) are under the power supply. Bass is not less, perhaps even more but civilised.

Mr H v d L, Holland

We have recently tried the Couplers as cable supports and found they give exemplary results in this application. The Coupler material is a broadband resonance absorbing polymer, the technology being unique to HRS. It is very easy to hear the effects of lowering the noise floor by removing the acoustic feedback loop from speaker energy transferred through the floor. Simple to use and discrete in operation when used under signal cables and power cords that contact the floor. For a speaker cable run of 2.5 m to 3.0 m, approximately 4 or 5 Couplers will be required to support the cable clear of the floor depending on the cable stiffness. At £86 for a pack or two, they also offer exceptional value for money for the level of sonic upgrade achieved.

Paul Rigby, The Audiophile Man, also agreed with our evaluation and has written the following review:

Paul Rigby (The Audiophile Man) Accessory Review


We can send out trial sample packs for home evaluation of the HRS effect. Usually a kit consisting of 4 Nimbus Assemblies and a Damping Plate suitable for the component. We can help recommend the best package for your particular trial. No obligation to purchase. All we ask is that, if no sale results, our delivery costs are covered.

Nimbus - Black only

Couplers £86.00 (pack of two)
Spacer 0.3" (7.6 mm) £50.00
Spacer 0.8" (20.3 mm) £55.00
Spacer 1.3" (33.0 mm) £60.00

These can also be purchased as a bonded assembly, see below, whereby the Couplers are factory glued to the spacer. This makes it easier to place under most pieces of equipment.

Nimbus Assembly - Black only

NA–100 1.0" (25.4 mm) £135                              
NA–150 1.5" (38.1 mm) £145                              
NA–200 2.0" (50.8 mm) £150

Damping Plates DP II Series – Black or Silver

Small DPII-05545  (4.5" x 5.5"; 114 x 140 mm) £170                                                                                       
Medium DPII-09545 (4.5" x 9.5"; 114 x 241 mm) £235 
Large DPII-14545 (4.5" x 14.5"; 114 x 368 mm) £295

Discounts available for mail order purchases of more than £600 in one order. Please phone for details.

For information on the ADL or the new ADH Record Weight, please look under the Vinyl Replay section of our website. Prices: ADL £265, ADH £495

Nimbus Assembly
Nimbus Assembly
Master Reference HD03
DP II Series Damping Plates

DPX Damping Plates

HRS have developed a thicker DPX Damping Plate which has more than twice the thickness of aircraft grade aluminium.The damping polymer remains the same as in the DPII range. This is more than twice the mass and many more times the stiffness of the standard DPII plates. Mainly for use with thicker plate chassis but can be very beneficial with almost any electronic component. The difference in sound by using the DPX version is much more than would be suggested with the price difference. An extremely audible upgrade and good value for the price point

Damping Plates – DPX Series – Black or Silver

DPX-05545 Small (4.5" x 5.5"; 114 x 140 mm) £225                              
DPX-09545 Medium (4.5" x 9.5"; 114 x 241 mm) £315                              
DPX-14545 Large (4.5" x 14.5"; 114 x 368 mm) £380

DPX Damping Plates
DPX Series Damping Plates


This is a new chassis noise reduction product designed to work with the thicker and stiffer chassis that some larger and heavier electronics are constructed from. They are similar to the Nimbus Assemblies but are constructed from a stainless steel outer with the HRS proprietary damping medium incorporated within the Vortex, and a Nimbus coupler at the top that is designed to contact with the bottom plate of a chassis, not the steel outer. 

With direct metal contact ( such as Stillpoints, Cerabase, and Pulsar points) the main result is a brighter, more forward sound. The custom material interface used within the Vortex steel outer case was optimized to push the limits of resolution and dynamics without brightness, fatigue, or high frequency noise. HRS developed the new material specifically for the Vortex primary interface to get the best of all musical qualities combined. With final 2 versions of prototype Vortex, HRS listened to many different types of recordings, and on many systems. Neither of them ever allowed the system to become bright, or have high frequency noise artefacts. They specifically listened for that negative effect during testing to ensure real lifelike speed and dynamics, but also no noise artefacts that just do not exist in a live performance.

The Vortex “footers” come in two versions. The V-150 is a fixed height design which has a shallow, but not sharp, point at the underside. This will not mark delicate surfaces such as metal or granite. The V-150A has an adjustable height device underneath, and a tool is supplied to do this height adjustment when this Vortex is placed underneath the chassis. When 4 or more Vortex units are used, and to allow for the fact that most chassis are not always flat, this adjustable module ensures intimate contact of all Vortex modules used with the underside of the chassis being treated.

The first evaluation tests with the new Vortex assemblies were immediate and obvious. Just placing 3 Vortex modules under a chassis constructed with 13 mm thick aluminium plate, and another 3 under the separate power supply similarly constructed, produced an astonishing and exceptional improvement to the sound. Just a few seconds into the piece of music being played the sound improvements were evident, and were not subtle. This is compared to the same piece of electronics already sitting on 3 NA-150 Nimbus Assemblies and on top of a M3X-1921 base, but the move up in sound quality using the Vortex took me by surprise. Better transparency, wider and deeper soundstage (it was not bad before!), better separation of instruments and voices, better transient attack and dynamics. A complex early music vocal piece with 6 singers was much easier to follow as the reduced noise floor resulted in improved articulation. Focus of images was better, more air around the singers within the tangible space that the recording was made in. There was no increase in brightness and the presentation was not more forward, as there can be with other steel/ceramic balls designs such as Stillpoints, Cerabases or Pulsar Points. The lack of forwardness is an absolute plus point, in fact the sound stage is deeper and wider. Removal of high end “fizz”, as I like to call it, is what Nimbus products do anyway. The Vortex assemblies take this to a whole new level.

The next unexpected result was when the 4th adjustable Vortex assembly was placed under the chassis. A further step change occurred but this time the main benefit was to the tonal balance. There was more authority to the bass end of the frequency range which gave a more realistic balance to the timbre of instruments and voices, with added texture to strings being bowed or plucked. The complex resonances of a piano were more evident and the decays of sustained notes just went on and on.

We have demonstration samples for home evaluation. For owners of electronics constructed from thick plate or billet, such as Edge, Boulder, Constellation, Ayre, or Solution, we highly recommend an audition of this product to allow you to hear the true potential of these designs. Please note that with normal, thinner metal sheet chassis the standard Nimbus Assemblies will still be the first choice.

V-150 (fixed height assembly) £350.00
V-150A (adjustable height assembly) £395.00
V-150 Set (3 x V-150 plus 1 x V-150A) £1295.00

Harmonic Resolution Systems website

Vortex V-150 plus adjustable V-150A
Vortex V-150 plus adjustable V-150A
Vortex V-150 plus adjustable V-150A
Vortex V-150 plus adjustable V-150A
Vortex V-150 plus adjustable V-150A
Vortex V-150 plus adjustable V-150A