Hardware Reviews

Stack Audio Auva 70 is a loudspeaker breakthrough

Stack AUVA speaker isolation feet

Stack Audio Auva 70 loudspeaker isolation feet

Stack Audio Auva is Theo Stack’s latest creation. I have known Theo Stack since I met him at the Bristol Audio Show back in 2016. He lives not far from me in Devon and has been to Kelly Towers on a number of occasions. His eponymous audio company has been going for a few years now, including the Link streamer and Serene upgrades for the Linn Sondek LP12. Like many engineers, Theo is not one to twiddle his thumbs, and is constantly applying his fertile mind to finding new areas in which to improve an audiophile’s enjoyment of their system. Thus it was that last year he told me that he was exploring ways to improve acoustic isolation for components, and was starting with devices to help remove unwanted vibration from loudspeakers.

Isolation feet: secret ingredients

The Auva 70 (there is also an Auva 100 available, which is a larger sibling of the review version) is a slim cylinder, machined from a solid billet of aluminium which is packed with a carefully selected amalgam of particles. A patent is being applied for so Stack Audio are rightly wary of giving away too much intellectual property, but on their website they confirm that one of the ingredients is tungsten powder. In the Auva 70 there are three effective cells packed with the magic powder, whereas the 100 has five cells. I am looking forward to trying the larger version at some point in the future. The Auva 70s are 70mm in diameter and 30mm high, without the top bolt or spikes. Various thread sizes are available, to accommodate a wide range of loudspeakers and stands. They will support any loudspeaker which weighs less than 275kg, so any speaker.

Stack AUVA review

Towards the end of last year Theo arrived with 8 pre-production examples of the devices that he planned to take to market. Regular readers will know that my own loudspeakers are Harbeth’s Compact 7ESXD stand mounts. As luck would have it Theo’s visit occurred during a lull in speakers reviews for me, so the Harbeths were in place. They were sitting atop the Skylan stands whose top-plate is oversized for the C7s, having been bought for use with my previous Harbeths. However they are the right height to put the C7ESXD’s tweeters at ear level for me in my listening chair, so I kept them in the room to try with this speaker.

Stack Audio Auva are a worthwhile investment

Almost from the beginning of my Harbeth ownership experience, which started back in 2014, I have experimented with different materials between the bottom of the speaker cabinet and the stand. I first used Blu Tack and then started to experiment with more audio-centric products, from several different manufacturers, before settling on some very expensive devices made in the USA. What an isolation device should do for me it to tighten up the sound, giving better definition to the lower frequencies while opening up the midband and making the upper frequencies more airy. These are not “it sounded broken before” enhancements, far from it. I chose Harbeths because they sound so unforced and natural, and have a midband (where human voice and many instruments tend to perform) which is astonishingly lifelike. However, the improvements I have gained with isolators has made the investment worthwhile.

The production Stack Audio Auvas that I have here now are black cylinders with a resemblance to an ice hockey puck, with on one side a receiver for a threaded rod that can be screwed into the spike socket on a floorstander and on the other side three holes that accept a set of spikes for use on a carpet. The fit and finish is exemplary. When used under standmount loudspeakers, then obviously the ancillary hardware is not used. I placed isolators under the four corners of my Compact 7s and sat back to listen.

Stack AUVA speaker isolation review

The Stack Audio Auva listening experience

My playlist for this first session was an eclectic mix, curated as a Qobuz playlist and streamed from that service through an Auralic Aries Mini plugged into my Lyngdorf TDAI3400. The first track was Harlan County Line by Dave Alvin from his Eleven Eleven album. This well recorded slice of Americana features Alvin’s gruff baritone over his guitar, drums and bass. What I heard immediately with Auvas in place was better definition between the instruments and slightly more tuneful bass, which benefitted both the voice, bass guitar and the drums.

I subsequently played a selection of tunes by the Beatles, The Rolling Stones, Pink Floyd and other favourites. My reaction to each was the same – the music seemed more focused with the Auvas than it had with the devices I had been using previously. The effect was subtle, but when I swapped out the Auvas for my own isolators the music sounded somehow less vivid, and thus less engaging.

In due course I switched the stands back to my C7-specific Hi-Fi Racks Fortis, an open design with no top-plate. I first listened to the same first track with my own isolators between the top of the legs and the Compact 7s. I placed an Auva at the top of each leg and placed the loudspeaker on top of those. Listening to the same tracks as I had with the Skylans stands, I heard very much what I had heard before, and I really liked it.

Some weeks later I took delivery of a pair of Kudos Titan 606 floor standing loudspeakers, which had arrived for a review (coming soon). These are an Isobaric bass reflex design with a second bass unit in the lower half of the cabinet. Stack Audio Auva are supplied with an excellent set of Target Audio spikes for standing on a carpeted floor.

Stack Audio Auva 70

I shall not pre-empt my review of the 606s, except to say that from the outset, driven from the 8 Ohm taps on my newly reinstalled Primaluna EVO400 integrated amplifier, they sound absolutely terrific. However, as I had the Auvas here it seemed perverse not to try them in the configuration for which they were actually developed, that is underneath a floorstanding loudspeaker. I invited Theo to come over and help install them properly, which he did a few days later. First though, he and I sat and listened to some test tracks with the supplied spikes in place.

Once all four corners on each speaker had been fitted with an Auva, we listened again to the same music. It was very interesting to be able to hear that even on a speaker retailing for five figures in the UK, the Auvas made an audible if subtle improvement. Bass seemed tighter, with no smearing of detail, even when the amplifier’s 8 EL34 main drive valves were being asked to drive the 606s to limits way beyond comfortable domestic levels, when room vibrations can be felt. Ease the volume back to more ear-friendly level and the extra sense of control, space and air was evident. This is in no way a put down of the 606s when dressed with their supplied spikes, but rather reveals even more of this loudspeakers capabilities.

Stack Audio Auva conclusion

Every floorstanding loudspeaker of my acquaintance has been supplied with spikes to allow good connection between the floor and the speaker, as has every stand designed to support smaller loudspeakers. I have never thought that vibration was somehow degrading the sound quality of such loudspeakers. In general, I have concentrated more on vibration control for the electronics in my system, the amplifier, rack-mounted sources like my SACD player and my phono stage, and usually with positive results.

Stack AUVA review

As I said early in this piece, I have experimented with different interfaces between my stand-mount speakers and their stands, and had settled on something with which I have been quite content. The Auvas however have given me serious pause for thought. They have worked very effectively as spike replacements, which is what Theo Stack had envisaged as their primary purpose. However, used without their bolts and spikes I have found them to be an improvement when placed between speaker and stand.

At this point you may be thinking “I paid £x for my loudspeakers, and I love them. Why would I need to spend another significant sum on isolators?” and that is a very fair question. However, given that Stack Audio is offering a 30 day money back guarantee I would answer by suggesting you give them a try. In my16’ x 13.5’ room, which has a concrete floor and is carpeted, the Stack Audio Auva makes an audible improvement on two very different loudspeaker systems. I think that they are most definitely worth investigating and could propel your great sounding system into something even better.


Type: loudspeaker isolation feet
Material: aluminium plus proprietary materials
Thread options: ¼”-20, M6-1.0, M8-1.25, M10-1.5
Speaker weight range: up to 275kg.
Includes: fixing adapters, adapter tool, felt discs, spikes
Dimensions (HxDia): 30mm x 70mm
Weight: 380g each

Price when tested:
£840/set of 8
Manufacturer Details:

Stack Audio
T +44(0)1626 24 9005


loudspeaker isolation feet


Chris Kelly

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