In the October 2015 issue of audioXpress, I reviewed the IsoAcoustics Aperta Speaker Stands, which I found to be highly effective at preventing vibration transmission from the loudspeaker to the surface below. The IsoAcoustics Aperta stands actually enable the speaker and the top portion of the stand to move, while the bottom portion of the stand remains stationary. In IsoAcoustics’ own words, “Decoupling the audio speakers or studio monitors from the supporting surface reduces the energy from exciting other objects, and allows the speaker and enclosure to float independently.”
In designing the Recoil Stabilizers (see Photo 1), Primacoustic has taken the more conventional view that the loudspeaker should never move. Primacoustic has chosen to prevent recoil, noting that “By reducing the backward ‘recoil’ as the speaker coil pushes energy forward, the initial transient no longer suffers lag and the sharpness of the resulting impulse is more defined.”
The Recoil Stabilizer incorporates four key components to achieve the desired combination of isolation and stability (see Photo 2). Isolation is provided by a high-density, open-cell urethane foam base measuring 2 1/4-inches (57 mm) thick. The foam prevents resonant frequencies from traveling from the loudspeaker to the supporting shelf. This open-cell foam is dense enough to support the weight of the speaker, and soft and thick enough to provide isolation from the surface below. Foam can deteriorate over time, due to oxidation and the effects of ultra-violet radiation. Primacoustic embeds the foam with carbon to lessen these effects, extending the life of the foam.
The foam is glued to a 0.25” thick (6.4 mm) lasercut steel plate, which places a heavy mass on top of the foam and acts as a platform for the speaker, and as a stabilizing counterforce to the movement of the low-frequency driver. The steel base is shaped into a curved “L” in front to minimize standing waves; the extra steel also adds mass to the base. The top of the steel plate is covered with a 0.125” thick (3.2 mm), non-skid neoprene pad, which ensures that the speaker remains securely in place, and does not move as a result of the cone motion of the low-frequency driver. Without any speaker mounted on the stabilizer, the steel plate rings when you strike it. But, the stabilizer is designed so that the speaker’s weight dampens the vibration of the steel, resulting in an inert thud when struck.
Radial manufactures the Recoil Stabilizer in 12 different models (see Photo 3), which range in size from 7.5” × 9.5” (241 mm × 190.5 mm) up to 20” × 22” (508 mm × 559 mm). The two smaller models — the RX5 and the RX7 — are available either flat, angled down 5°, or angled up 10°. The mid-sized RX9 and RX12 are available flat or angled down 5°. The RX17 and the RX20, which are the two largest, are only available flat, since they’re intended for loudspeakers too large for desktop or shelf-mounted applications.
At my request, Radial Engineering supplied the RX7-HF for review, since it’s just the right size for the Monitor Audio Bronze BX2 loudspeakers that I use on my editing and audio restoration computer at The Crane School of Music. This model measures 10.375” × 13” (263 mm × 330 mm) and weighs a hefty 10.8 lbs. (4.9 kg).
I found the Recoil Stabilizer to be a highly-effective product. Clarity and definition improved across the spectrum, but especially in the bass region. The stereo image is rendered with greater precision, and there is a noticeable reduction in transient smearing. Primacoustic doesn’t publish any isolation specifications for the Recoil Stabilizer, but I conducted a simple, admittedly subjective test of its isolation effectiveness. On an orchestral recording with loud bass drum material, I could feel a pronounced vibration on the sides of my Monitor Audio loudspeaker enclosures. On the shelf below the Recoil Stabilizer, the vibration was all but eliminated.
Primacoustic has testimonials from several dozen audio and recording industry professionals, as well as musicians, on its website. If your speakers need stability and isolation — which they probably do — the Recoil Stabilizers deserve serious consideration. ax
Primacoustic Recoil Stabilizer
Primacoustic, A Division of Radial Engineering
1588 Kebet Way, Port Coquitlam
BC Canada V3C 5M5
RX7-HF: $99.99 (other sizes vary)
Primacoustic Recoil Stabilizer
Deck: 0.25” steel, black powder coated with 0.125” neoprene pad
Base: High-density polyurethane foam
Number per box: 1
RX5 - 5.75 lbs. (2.6 kg)
RX7 - 10.8 lbs. (4.9 kg)
RX9 - 12.5 lbs. (5.7 kg)
RX12 - 22 lbs. (10 kg)
RX17 - 22 lbs. (10 kg)
RX20 - 36 lbs. (16.3 kg)