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Sierra-2 Reference Ribbon Monitor

Audiophile

Battlestations

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Sierra-2 Reference Ribbon Monitor

PiePieNinja

Dec 13, 2015

With the success and overwhelmingly positive customer feedback of our Sierra Ribbon Towers, we set our sights on bringing that type of performance to a more mainstream audience by offering it in a bookshelf speaker and bringing the cost down to a point that we felt most could afford. Of course, this was no simple task and in typical Ascend fashion, simply using existing components would just not cut it.
Over the past 3 years, having become RAAL's highest volume customer, through thorough evaluation and experience - we became experts in what makes these tweeters so special. We came to the conclusion that in many ways, the ribbon tweeter we use in the Sierra Tower is a bit overkill for a bookshelf speaker. We felt we could capture the same extraordinary performance in a new custom designed, lower cost unit fully optimized for our application. Together with RAAL’s owner, we set out on a challenging journey.
2 years and dozens of prototypes later, our goal was met and we had our new RAAL ribbon tweeter. Our new tweeter has a total moving mass of less than 1/100th of a gram, significantly less moving mass than nearly all other tweeters. Relieving the radiating diaphragm of excess weight allows for near perfect transient reproduction combined with the lowest levels of stored energy for extremely detailed, airy highs with no edginess or fatigue.
During the tweeter design process we were able to design a specific set of parameters and performance characteristics for our new woofer, with the primary goal being to achieve an ideal synergy with the ribbon tweeter. This was quite the challenge as we were presented with several difficult hurdles.
Our new ribbon would require a higher crossover point than we typically used for our woofers. To maintain good high frequency performance, the woofer cone must be quite stiff. The problem with stiff cones is that they tend to suffer from harsher cone breakup modes that need to be compensated for in the crossover. This goes against our original Sierra philosophy of “less is more” so thus began a search for a cone material that was exceptionally stiff but also extremely well damped. The polypropylene we use in the Sierra-1 woofer, while it has good self-damping, is just not stiff enough to provide the upper midrange response required for a proper crossover to our new ribbon tweeter.
Taking full advantage of our nearly 15 year relationship with SEAS of Norway, we confronted their director with the challenge. After much discussion he recommended we try something new; something he said might be the future of cone woofer materials. Curv™ is a woven polypropylene that takes all the great qualities of pp, but makes significant improvements. Stiffness to mass can be precisely controlled and the material is very lightweight yet extremely stiff, but its best quality is that internal damping is simply stunning. In fact, we did not measure any cone breakup or resonance modes within our needed bandwidth which meant we could cross this woofer at higher frequencies without trapping out breakup modes in the crossover.
The other significant problem we faced was how to at least come close to producing the phenomenal bass response of the Sierra-1 while using a woofer cone that has significantly lower mass, while also maintaining reasonable sensitivity. We simply can’t defy the laws of physics, meaning it would not be possible for the same size cone area.
The solution to this problem presented itself in an interesting manner – a bit of luck combined with some clever tooling. It turns out that this new Curv cone is equivalent to a 6” woofer and provides just a bit over 29% more radiating surface area than the 5 ¼” woofer we use in the Sierra-1. Because of this, we are able to maintain efficiency and bass response, while also using a lower mass cone which reduces inertia and better matches the amazing transient accuracy of the RAAL ribbon. We managed to fit a custom 6” woofer into the 5 ¼” woofer cutout of the Sierra-1 cabinet, with the cone having considerably less mass yet maintaining excellent bass with significant improvements to transient reproduction and midrange performance.
The Sierra-2 woofer features: long-throw design for high power handling and extended bass radially reinforced surround reduces surround resonances at higher excursions and provides for better overall damping SEAS’s exclusive SpiderRing® technology improves suspension alignment for higher long term reliability, improved power handling and improved mechanical linearity custom cast magnesium frame for a stiffer and lighter basket frame allowing for less material behind the woofer cone reducing back-wave reflections for enhanced detail, better airflow and less cavity resonance vented pole-piece and open spider for enhanced air-flow and cooling, minimizing compression artifacts We then optimized and tooled all of these new components so that they would drop right into our renowned Sierra-1 layered bamboo cabinets for the ultimate in resonance control and stiffness. This also allows all Sierra-1 speakers to be user upgradeable to Sierra-2.
The result of this true engineering feat? A bookshelf speaker that simply might be the very best at any price point, offering performance that is truly shocking.
Hand assembled, tested and packaged in the USA, we are so confident of the component and build quality of the Sierra-2 that we are backing it by a comprehensive 7 year parts & labor warranty. Left / right pairs are matched by hand to within ± 1dB and we are including a printout of the actual production line response measurements of each speaker. We dare say it, but you simply can not find this type of quality control, care and pride from products that are fully assembled and tested in overseas manufacturing facilities.