North Acoustics

Near Wall Specific™ Loudspeaker System


Design Goals:

The North Spirit is intended for small rooms and rooms in which the loudspeaker positions are close to the rear wall. Unlike most loudspeaker systems, which benefit from placement well into the listening room, the Spirit has been designed specifically to perform at its best when placed either on a bookshelf or stand within eight inches of the rear wall. The Spirit is a high performance two-way monitor built around the exceptional North D25 silk dome tweeter and the superb Vifa P13WH-00-08 5" polypropylene cone woofer in an EBS aligned vented cabinet. The loudspeaker is voiced in such a way that the combination of low frequency response and low end gain from the room placement constraints produces a low end that is very dynamic and goes remarkably deep, yet still maintains the speed and finesse of a monitor loudspeaker.

We consider the Spirit the world's first truly high end bookshelf-specific loudspeaker.

Spirit in light Cherry, courtesy of Lee Taylor and Company.



The Tweeter:

The North D25 -06S was designed by George Short exclusively for North Creek Music Systems. It is a 25mm silk dome with an under-hung gap geometry, 1.0mm peak-peak excursion, MAPD rear chamber, well controlled resonance and frequency response characteristics, and very light magnetic fluid cooling. The 25mm dome diameter offers excellent off-axis dispersion. Sonically, it is very similar in character to the Scan-Speak D2905/9500 (liquid and wonderfully detailed) but with a touch more sparkle at the top end. The North D25 is widely considered the most naturally musical, affordably priced tweeter on the market.

The Woofer:

The woofer selected for the Spirit is the P13WH-00-08 5" polypropylene cone from Vifa of Denmark.

The Vifa P13WH-00-08 is a classic example of a small woofer where resonance frequency, motor strength and cone excursion are perfectly balanced to maximize the low frequency extension from a small vented box. A fundamental resonance in the mid-sixties and 8 mm of linear excursion (14 mm peak) allows this woofer to reproduce convincing bass into the upper 50's, yet stay remarkably clean.

The cone is a strait-sided, mica-filled polypropylene, with a nylon dust cap and Dr. Kurt Muller rubber surround. This combination yields one of the flattest frequency response curves we have ever seen, with a smooth high frequency roll off and no indication of cone break up. It is a delicate balance that emphasizes the smoothness of a poly cone, but without the softness and loss of detail common with larger cones.

The frame is cast magnesium, extremely rigid and strong enough to secure the massive 14.6 oz. magnet without vibration.


The Spirit Cabinet:

To perfectly match the Vifa P13WH-00-08 to the listening environment, we selected an EBS (extended bass shelf) vented alignment. The cabinet volume required is 6.44 liters, and port tuning is set at 63 Hz.

The cabinet measures 12 1/2 tall by 7 1/2 wide by 9 5/8 deep, The Fascia is 1 5/8" thick, constructed with and MDF-baltic birch plywood laminate incorporating constrained layer damping. There is a single 3/4" brace. Both the brace partitions and woofer egress are aerodynamically flared to improve system performance at high volume levels.

The port is rear mounted and combines a flared egress and forced laminar flow throughout the body to reproduce bass that is remarkably clean and tight even at very high power levels.

Although this cabinet has about the same profile as an 8 1/2 x 11 sheet of paper, it is incredibly rigid and weighs in at a hefty 17 pounds.

Spirit in Curly Maple by Lee Taylor and Co.


The Crossover:

Crossover design is more art than science, and no loudspeaker has exhibited this more strongly than the Spirit. The placement constraints and room size restrictions made the design process incredibly difficult. The prototype was in the small North Acoustics listening room for over two years, and went through literally thousands of design iterations and months of voicing. Yet finally the perfect balance of low end finesse, midrange clarity and top end speed was achieved.

The Spirit network features a simple second order high pass network on the tweeter and a cascaded third order on the woofer. The woofer network topology was developed specifically for the Vifa P13WH, and like the tweeter network it has only a single reactive component in the signal path. Although proprietary, the crossover topology is incredibly simple and showcases the excellence of crossover component quality.

The overall acoustic network is a symmetric third order at 1.8kHz, the antiphase null is 26dB, and system frequency response is a very smooth 59 Hz to 20kHz 2dB. Reference sensitivity is 84.5dB for 2.83V, 1 meter input. Input impedance is 8 Ohm nominal, 6 ohm minimum. As this speaker was designed specifically for near wall placement in small listening rooms, minimum amplifier power only 30 watts.


The Sound:

Of course, this is all that really matters.

The Spirit is just extraordinary. The system takes the low end finesse and midrange clarity of the small, light 5" woofer cone driven by a massive magnet and combines it with the remarkable speed and resolution of our silk dome tweeters.

The bass is very fast and articulate, yet packs a punch that belies the Spirit's small size. The tempo is also very good, with a lower midrange that is robust but never chesty.

The upper midrange is very clean, and the 1.8kHz crossover frequency brings the tweeter in as early as possible. Female vocal harmonics are thus carried by the tweeter; incredibly lifelike and very accurate.

The top end is typical of silk domes; smooth, sweet, detailed; never bright or hard. The North D2506-S is very musical here.

Overall, the Spirit is one of the most accurate, yet listenable, small loudspeakers ever produced.

Spirit in Birds Eye Maple by Lee Taylor and Co.


North Spirit

Expertly assembled loudspeaker system built from perfect pair, shielded Vifa P13's, perfect pair shielded North D25-06S, crossover networks consisting of 12 AWG inductors throughout, North power resistors, Cascade-Bypassed Crescendo polypropylene film-and-foil capacitors, and electrolytic capacitors bypassed by Zen capacitors in the woofer section. All crossover components are hand matched to 1%. Single wired.

North Spirit $ 1299.00 per pair (beech, black ash)

North Spirit - Lee Taylor assembled in a Lee Taylor cabinet with any available veneer and the finest traditional finishes, also available veneered all six sides.....$1599 - $1999 per pair

 North Spirit in Cherry by Lee Taylor and Company.


Other than through the showroom, one may order North Acoustics loudspeakers via our voice/fax number (315-369-2500), via email, or via mail to North Acoustics, PO Box 1120, Old Forge NY 13420-1120.


Comments on The Absolute Sound review of the North Spirit Loudspeaker:

We would like to take this opportunity to thank TAS and Sue Kraft for putting the time and effort into reviewing the North Acoustics' Spirit loudspeaker, and for providing this opportunity to comment.

There are a plethora of excellent small loudspeakers available today incorrectly labeled "bookshelf monitors" simply because of their small size, when in fact most were optimized for free-field placement on stands well into the room and with plenty of volume behind them to breathe. When moved close to a wall, a loudspeaker designed in the free-field will tend to suffer mid-bass bloat, a loss of image stability and sound stage collapse.

Not so the North Spirit. This loudspeaker embraces bookshelf placement, and in fact its low end fills in and sound stage "fleshes out" nicely when tucked into a corner, set a ledge, or tossed up top a mantle piece.

It is incredibly difficult to design a high end loudspeaker for bookshelf placement.. which is why there are so few. The voicing is so delicate; drawing the best bass one can get from a small woofer in a small cabinet, a midrange and top end that can never get hard or forward regardless of
whether the listener is sitting or standing, yet maintaining harmonic integrity. Finding the perfect balance in a loudspeaker that assumes so little yet performs so well requires a little bit of magic.

The North Spirit prototype was designed over a period of two years, entirely by ear. When it comes to scaling a sound stage and recreating image depth, measurements are meaningless and only months of listening and fine tuning suffice. The fact that the Spirit measures +-2dB from 57Hz to 20kHz - far better than most loudspeakers five times its price - is rather amazing, and in fact I was quite surprised myself the first time I measured them.

Thanks again TAS and Ms. Kraft for your fine work and this excellent

George Short, President
North Creek Music Systems
North Acoustics

North Spirit and Sapele by Lee Taylor and Co. front and back, photos courtesy of
Lee Taylor and company.


This publication is copyright © 2006 by North Acoustics. All rights reserved.