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Our New Benchmark Bookshelf Ribbon Speaker

Important Note: Sierra-2EX center has been replaced by our new Sierra-2EX V2 Center

Featuring our new proprietary 6" SEAS EXCEL Curv™ Woofer.

With the development of this shockingly high-performance new woofer, we have improved upon every aspect of our award winning Sierra-2. Truly stunning bass extension and midbass punch, mids are cleaner - smoother and more detailed, improved dynamics and better composure at higher volume levels.

Over 1.5 years in development and taking full advantage of the best transducer engineers in the business, we are excited to once again set a new performance standard. High-end tower-like speaker performance in a compact beautiful bookshelf-sized speaker.

Follow the development of the Sierra-2EX from beginning to end:
Sierra-2EX Development


100% MONEY




A while back, we were privileged to be introduced to a new super high-end diamond tweeter SEAS developed called the White Diamond. We were extremely impressed and immediately requested that SEAS build us up a matching cost-no-object woofer based on specific parameters to meet our performance goals.

About one year later and after many samples, we had our new woofer and we started building and selling custom Sierra Diamond speakers. These custom Sierra Diamond speakers start at ~$8000/pair, thus greatly limiting their affordability.

The performance of the Sierra Diamond is astonishing, but customers as well as those who auditioned this speaker noted that as impressed as they were with the diamond tweeter, the woofer was equally impressive. We fully agreed. The midbass punch, bass extension, midrange detail, frequency response linearity, and overall dynamics was the best we had ever come across in a woofer this size, and even compared to many larger woofers.

Our own customers started to inquire about using this woofer in many of our designs, including our most successful speaker to date, our award-winning Sierra-2. Problem was, being a true custom build - each of these woofers was being hand made for us by SEAS’s engineering team. These had never been mass produced.

As a company, we have always tried to give our customers and fans what they ask for – this is a major advantage of selling direct – we get to communicate directly with consumers. Upon witnessing the massive amount of interest in a Sierra-2 with this woofer, we became fully committed to make it happen.

SEAS went to work on optimizing manufacturing processes and parts procurement – while we committed to purchasing a large enough supply to make it beneficial for both SEAS and Ascend and get the per unit pricing down to a point to make it affordable, a true win-win.

Our EX woofer is part of SEAS’s Excel line, using an optimized version of the venerable W16 motor system – customized to best match a new specially treated Curv woofer cone. Our EX woofer is a purely custom build compared to the stock W16 and is exclusive to Ascend Acoustics.

The Sierra-2EX improves upon every performance aspect of the Sierra-2. This is a true benchmark product and thanks to the feedback and inquiries from all of you – we fully committed ourselves to making it happen and we could not be any more pleased with the results.

Hand assembled, tested and packaged in the USA, we are so confident of the component and build quality of the Sierra-2EX 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 measurement of each speaker.

We dare say it, but you simply cannot find this type of quality control, care and pride from products that are fully assembled and tested in overseas manufacturing facilities.

We must warn you though, once you have heard what these RAAL true ribbon tweeters are capable of, there simply is no turning back...

We thank you for your interest!



  • All Sierra-2EX are hand assembled, tested and packaged at our factory in Orange County, CA.
  • A serialized production line frequency response measurement is included with each speaker.
  • 7 year manufacturer's warranty + 30-day satisfaction guarantee.


  • Exclusive vertically laminated bamboo cabinet construction dramatically reduces cabinet resonance for a cleaner, more detailed, and transparent performance.
  • Cabinet is a stunningly beautiful natural hardwood finish, there are no veneers and as such, no need to be concerned about peeling veneers or wraps or veneer cracks.
  • Cabinet is fully environmentally friendly as the bamboo we source is a completely renewable resource.


  • Fully custom manufactured by SEAS of Norway to our specifications and exclusive to Ascend Acoustics.
  • Long-throw design for high power handling and extended bass.
  • 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.
  • Radially reinforced surround reduces surround resonances at higher excursions and provides for better overall damping.
  • Exceptionally large magnet system combined with symmetrical driving force.
  • Pure copper upper and lower shorting rings to reduce distortion, linearize magnetic flux, and dramatically reduce inductance.
  • Massive pure copper phase plug improves off-axis dispersion, greatly reduces any beaming, improves power handling and thermal compression by acting as a massive heat sink, and enhances the functions of the upper and lower shorting rings.
  • Vented pole-piece and open spider for enhanced air-flow and cooling, minimizing compression artifacts.
  • Exclsuvie SEAS Curv™ cone technology (woven polypropylene) featuring a newly developed damping treatment for exceptional self-damping, extremely low mass, high stiffness combined with exceptional self-damping providing greater detail while remaining smooth with no harsh cone break-up modes.


  • Fully custom true ribbon tweeter manufactured by RAAL in Serbia to our specifications.
  • True ribbon tweeter has no voice coil, the pure aluminum ribbon is the only electrical conductor and the only moving part.
  • Extremely low moving mass design, typically less than 1/50th the mass of a dome tweeter, enabling near instantaneous acceleration / deceleration, and no stored energy all combined to provide near perfect transient reproduction.
  • Class-leading horizontal dispersion width provides a huge soundstage and precise imaging.
  • High powered neodymium magnets in a unique homogenous design (equal strength magnetic field throughout the entire ribbon area) provides lower distortion and less stress on the ribbon diaphragm.
  • Critically damped rear chamber to absorb the back wave of the ribbon diaphragm, improving frequency response linearity and overall transparency.


  • Large open topology with proper inductor spacing and orientation to reduce mutual inductance and saturation.
  • Heavy gauge pure copper traces to reduce resistance and provide higher power handling.
  • Featuring metallized polypropylene capacitors.
  • Air-core inductors in the direct signal path.



Typical In-Room Frequency Response 33Hz - 27kHz
Typical In-Room Sensitivity 88dB @ 2.83v / 1 meter
Nominal Impedance 8 ohms
Max Continuous Power* 150 watts
Max Short Term Peak Power* 300 watts
Cabinet Detail Exclusive V-LAM™ construction featuring 20mm thick vertically laminated bamboo, internally braced. Bass reflex via flared rear port tube
Tweeter Custom made RAAL true ribbon tweeter featuring a 10mm wide pure aluminum ribbon with a total moving mass of less than 1/100th of a gram
Woofer Proprietary 6” long-throw low mass treated Curv™ cone Excel woofer, non-resonant cast magnesium frame, radially reinforced surround, SEAS SpiderRing® technology, solid copper phase plug, upper and lower copper shorting rings, vented pole-piece and vented spider. Custom made for us by SEAS of Norway and exclusive to Ascend Acoustics
Connections (2) gold plated all metal 5 way binding posts
Inserts 1/4-20 threaded insert for securing to our TP-24 stands
Anechoic Frequency Response 38Hz - 27kHz +/- 3dB
Anechoic Sensitivity 85dB @ 2.83v / 1 meter
Dimensions H x W x D** 7.5" x 14.25" x 10.5" positioned horizontally
Speaker Weight (each) 20 pounds
Shipping Weight (each) 21 pounds
Minimum Recommended Power At Listening Position for Specific Speaker Distances
3 Feet or Less 3 watts minimum
9 Feet or Less 26 watts minimum
15 Feet or Less 60 watts minimum
21 Feet or More 120 watts minimum
     *Unclipped peaks      **Grille On



*All measurements taken using DRA Lab’s MLSSA system with RCAI, calibrated ACO Pacific 7012 ½” free field measurement microphone with associated pre-amp and power supply and an automated Outline turntable.

Full-range quasi-anechoic on-axis frequency response @ 1 meter unsmoothed speaker positioned vertically:

Horizontal and vertical off-axis graphs plus listening window:

Note: Listening window is the averaged response of 5 separate measurements, on-axis, +/- 15 degrees horizontal and +/- 15 degrees vertical. Due to the measurement technique, the response below 250Hz is invalid, as represented by the above and below horizontal green bars.

Polar Response:

Note: 5 degree increments from 0 degs to a full 90 degs off-axis. Note how the critical midrange response remains linear and consistent with uniformly decreasing spl as frequency increases. This represents an exceptionally wide off-axis response.

Impedance and electrical phase:

Note the extremely clean impedance response (free from wrinkles which would represent various forms of resonances) and linear phase with minimal phase angles. The mild phase angles ensure that this speaker is an easy load for even basic receivers.

Energy Time Curve:

This measurement is a good indication of overall transient accuracy and stored energy. The graph displays the decay time of a full range impulse. The impulse occurs at 3ms and decreases uniformly to the noise floor (-45db) by 4ms. This represents a decay time of 1ms, which is superb. Large diameter woofer cones, woofers and tweeters with poorly designed motor systems and/or heavy mass and poorly constructed cabinets will often contribute to far greater decay times which damage transient accuracy, coherency and overall resolution.

Cumulative Spectral Decay:

This measurement is similar to the energy time curve but displays a 3 dimensional view such that we can examine the decay time with reference to frequency. It is an exceptional tool to reveal transient accuracy and indicate various problem areas with respect to resonance and stored energy. The CSD of the Sierra-2EX is exceptionally clean with good uniformity.

Spinorama Measurements:

This is a complex suite of measurements developed by Dr. Floyd Toole during his time at Harman and is now defined by ANSI/CTA-2034A. As clearly indicated, the Sierra-2EX displays superb spin measurements.



The Sierra-2EX improves upon every performance aspect of the Sierra-2 and the measurements are outstanding!

Mids are cleaner - smoother sounding with more weight to them (they sound warmer, fuller with more detail). Because of the upper end improvements, we were able to use a steeper high pass filter slope on the tweeter, easing the workload on the ribbon tweeter which in turn increases power handling, lowers distortion and provides for an even better overall blend between the woofer and tweeter.

The Sierra-2EX sounds like our Sierra-2, but is warmer/fuller, cleaner (especially at louder volume levels), more musical and with rather shocking dynamics. And, if run full range - the bass response seems to defy the laws of physics -- it is tower-like. In direct A/B comparisons with speakers using very high quality larger woofers, the EX woofer hit harder and deeper.

This is a true benchmark product and thanks to the feedback and inquiries from all of you – we fully committed ourselves to making it happen and we could not be any more pleased with the results.


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