North Creek Music Systems

Vision

and

Vision Signature

MAPD Monitor Loudspeakers

High end MAPD monitor loudspeaker system featuring the Scan Speak 15S/8530K-01 mid-woofers and Scan-Speak D2905/9900 Revelator tweeter in a classic MTM configuration.

The Vision Signature was conceived as a cost-no-object high end monitor loudspeaker designed for the most demanding two-channel and home theater environments, easily mated to most subwoofers, and compatible with both transistor and tube amplification.

The most critical aspects of high end home theater are
1) exceptional accuracy throughout the spoken human vocal range, and 2) unrestricted dynamic range. "Voicing" a loudspeaker to reproduce spoken voice is very difficult, not only because the fundamental frequencies are actually in the upper bass (where it is impossible to measure a loudspeaker accurately), but also because the ear is far more sensitive to inaccuracies in voice reproduction than it is to music reproduction. So here the entire loudspeaker had to be optimized by ear for spoken voice beginning with the deep male voice, and working on up in frequency.

The dynamic range of a loudspeaker is usually limited by driver excursion. Most mid-woofers have very limited excursion - usually only 6mm, hence at even moderate volume levels they become non-linear and begin to distort. We designed the Visions to have far more linear excursion than they would need even in the most demanding applications, allowing the system to be driven full range (with limited bass extension) or crossed to a subwoofer as low as 70 Hz.

As this is a no compromise design, we selected the bests tweeter money can buy - the North D28-06S and the Scan-Speak D2905/9900 Revelator. Both tweeters features hand-coated woven silk dome, a full 1mm peak-peak excursion, and enormous motor structures that uses Faraday technology to virtually eliminate harmonic and intermodulation distortion throughout the operating band. The Revelator tweeter has the lowest distortion of any tweeter available.

For the mid-woofers, we selected the Scan-Speak 15S/850K-01's. These are beautifully made units with a 5" paper cone and dust cap that has been radially sliced and rebonded, eliminating standing waves with the cone body. The frame is the new aerodynamic "grasshopper" cast aluminium, coupled to an enormous shielded motor structure also constructed with multiple faraday rings. This type of motor has lower distortion than any other available, and is patent protected.

Cabinet Type

To keep the system well controlled at low frequencies and compatible with both tube and transistor amplification, a new type of bass loading call symmetric MAPD (Multi-Chamber Aperiodic Damping) was invented by North Creek Music Systems. This unique cabinet configuration houses the mid-woofers in a small primary cabinet of volume exactly 1/3 the drivers equivalent suspension volume (Vas), controlling driver excursion linearity through the air spring. A secondary chamber with volume exactly equal to Vas is coupled to the primary chamber via an aperiodic vent, called a Scan Vent (also manufactured by Scan-Speak). The symmetric compliance about the primary chamber allows the low frequency tuning "Q" to be adjusted to optimally match the amplifier, yet still forces linear cone motion at high excursion without sacrificing low frequency extension.

 Frequency Response Family

This curve family was taken at 1 meter 5 degrees on the horizontal axis in an anechoic environment, with the equivalent of a 2.83V input. The microphone is calibrated through the software. Curve resolution is 5dB per major division, twice the resolution of typical frequency response curves.

The slight plateau (-1.5dB) through the crossover region is intentional, as it keeps the system power response flat (so there are no peaks off axis, increasing image width), improves image depth, and makes the speaker an excellent match with SET amplification.

The antiphase curve is also perfectly symmetric about the 1.8kHz crossover frequency, and the antiphase null is 20dB. There are no peaks in the antiphase response, confirming optimum phase lead for the woofer and phase lag for the tweeters in the transition region, and perfect constructive interference throughout the entire spectrum when the drivers are connected in phase.

The 2.0dB peak centered at 17.5kHz is a product of the voicing (the speaker was designed by ear); one can remove a 1.0uF Crescendo capacitor in the crossover to eliminate it.

The Vision's frequency response is nearly "textbook perfect".

This waterfall plot is taken at 1 meter, 5 degrees on the horizontal axis. Note that the scale is 30dB, offering twice the resolution of typical waterfall plots. We can do this because the decay is so fast and so clean there is very little decay information above the -30dB threshold.

The entire tweeter decay takes place in less than 1msec, indicting the tweeter dome is well damped, there are no reflecitons off the baffle, and the high pass crossover is very low Q. This is one benefit of using the concave Revelator face plate to control horizontal dispersion, whilst the large round-over of the baffle edge minimizes the usual 2kHz baffle "bump".

Note that the decay is an almost perfectly straight angle across the noise floor. What this means is that the phase is carried smoothly from the woofer to the tweeter (a second benefit of the 1/2" thick machined Revelator face plate and our crossover topology), that the mid-woofer's cone resonances are well controlled, and there are no reflections off the front baffle.

This measurement was also taken with the equivalent of a 2.83V input, so the low frequency characteristics are properly documented.

The MAPD loading is evident, here tuned to a Qtc of about 0.9 at 77Hz. We found this to be the optimum tuning when driving the system full range with SET amplification, with the -3dB amplifier cut-off set to 50Hz via adjusting the amplifier's internal coupling caps. The MAPD loading is easily adjusted to a higher Q when using the Visions full range with transistor amplification, or a lower Q when using the system with a subwoofer.

The 23 Ohm impedance peak at the crossover frequency is evidence of the low-Q nature of our crossover network. This peak usually does not affect transistor amplifier performance. With tube amplification, the interaction of the impedance peak and the amplifier output transformer impedance results in a slight "filling" of the frequency response through the transition region, and a richer upper midrange character. The loudspeaker was actually designed to take advantage of this effect. For amplifiers that are uncomfortable driving the higher midrange impedance, an additional compensation circuit can be ordered separately that adjusts the system to a nearly flat 4.0 Ohm load from 150 Hz to 20kHz.

That of course is the only thing that matters.

From 70 Hz on up, driven by a good transistor amplifier, the Vision Signature is simply the sweetest, most liquid, most musical loudspeaker this company has ever produced. Not only does it perfectly capture both the male and female voice with unbelievable realism, but it also reproduces every instrument with a subtlety of microdynamics and wealth of detail that is just wonderful to listen to and sometimes flat out amazing.

The Fairfield Four "Standing in the Safety Zone" (Warner Bros. 9 26945-2) is a great collection of male vocals. Our reference track is "Roll Jordan Roll". This is a difficult test for a loudspeaker as all of the vocal fundamentals and most of the harmonics are reproduced by the mid-woofers, but the majority of the tenors' harmonics are in the transition region and reproduced by both the mid-woofers and the tweeter. Here again the crossover is so perfectly executed that there is no hint of the transition, the vocals absolutely convincing, and the scale of the piece is captured perfectly, with the performers behind and well outside of the speaker positions, one even beyond the side walls.

Another of our reference track is from Genesis "Selling England by the Pound" (Atlantic 19277-2, a 1983 CD of the 1973 recording), the song "Cinema Show". This is a very good recording from that era, and the performance has layers and layers of detail. There is a point where Phil Collins and Peter Gabriel are harmonizing, their voices are so similar that for years I had thought this was Peter Gabriel's voice overdubbed. Through the Vision Signatures, one can distinctly hear which is Phil Collins and which is Peter Gabriel, with their very slight differences in accent clearly discernable.

Adding a single 0.1uF Crescendo cap per channel between the pre-amp and monitor power amp and using the low-Q Scan-Vent, the Vision's low frequency roll off was adjusted to be a perfect third order high pass at 85 Hz. The Vision-C, which uses a conventional aperiodic alignment, has a natural third order high pass roll off characteristic. The Thunder' low pass crossover is third order, and by placing the subs almost directly behind the Visions, all five speakers are wired with positive phase. Subwoofer integration is seamless, adding a solid foundation to the system without compromising its performance higher in frequency.

The system is just as good with movies and spoken voice as it is with music. The presence of the subwoofers makes the presentation overwhelmingly powerful, and the system overall is naturally musical and incredibly dynamic.

We are releasing the Vision in both Unlimited and Signature versions:

Internal wiring is 10 AWG OFHC copper to each woofer and 14 AWG Tef-Flex AG silver-clad OFHC copper to the tweeter. Binding posts are North Creek Big as Texas Posts. All connections are gold plated. Calibrated Scan Speak Scan Vents, Big Toes and Very Big Toes with inserts and lock nuts, mounting screws, gaskets, etc. are also included, and no soldering is required. In short, everything except the wood.

Vision Unlimited MAPD Monitor Loudspeaker Kit ….$ retired

Vision-C Unlimited Monitor Center Channel Loudspeaker Kit …$ retired.

The crossover network is fully assembled (hard wired) from our finest, hand-matched components. All inductors are 8 AWG North Creek Music Coil inductors; all resistors are NORTH non-inductive wire wound. The tweeter network features fully cascade-bypassed Crescendo capacitors also bypassed with a special 0.1uF, 1kV military film-foil cap of which we have a very limited supply. The woofer section uses Zen capacitors cascade-bypassed with Crescendo capacitors. All told, the crossover network uses ten 1.0uF Crescendo capacitors and ten 0.1uF bypass caps, and weighs in at about 30 pounds.

Internal wiring is 10 AWG OFHC copper to each woofer and 14 AWG Tef-Flex AG silver-clad OFHC copper to the tweeter. Binding posts are North Creek Big Posts. All connections are gold plated. Calibrated Scan Speak Scan Vents, Big Toes and Very Big Toes with inserts and lock nuts, mounting screws, gaskets, etc. are also included, and no soldering is required. In short, everything except the wood.

These two loudspeakers are very similar both visually and technologically, hence it seems appropriate to compare their relative merits.

The Rhythm Signature is a full range loudspeaker system, with bass extension to 32 Hz that is aggressively tuned, very fast and extremely dynamic. The midrange is also superb, demonstrating exceptional resolving power without ever being forward or hard. The top end is sweet, detailed, liquid and natural, but never overly bright.

The Visions are monitor loudspeakers, with a low end that is light, quick, and detailed. Bass extension is limited to about 60 Hz, however, and even though the low end's character can be adjusted considerably to match the amplifier and application, the Visions can not compete with the Rhythms in the extreme low end.

The Vision's upper midrange and top end are identical in character to the Rhythm's. This is because both loudspeakers share the same tweeter, same quality level of crossover components, identical crossover frequencies, and identical midrange and top end voicing.

The major differences between the Rhythm Signature and Vision Signature are in the bass and their ability to soundstage:

The Rhythm's low end goes a full octave deeper than the Vision's and goes there with authority. It has plenty of slam and impact because it was designed as a full range, stand alone loudspeaker system that is capable of reproducing rock, jazz and classical at convincing volume levels without difficulty. The Rhythms can fill a large room with music and plenty of bass at very high volume levels without fatigue, and it is only in the largest of rooms that they need to be augmented with a subwoofer.

The Visions can be tuned pretty punchy, but they do not go deep.

In terms of soundstage, the Visions are slightly better than the Rhythms. Both the Rhythms and Visions are significantly better than most loudspeakers in this regard, but the Visions benefit from the smaller mid-woofers and narrower fascia, which leads to superior horizontal dispersion.

The Visions are also very slightly more articulate through the mid-bass and midrange. Again, both of these loudspeakers are very good in this region, but for the Rhythms we are actually stretching the 7" woofer to the top of its range. The smaller mid-woofer in the Vision is in relative terms being pushed by a much larger magnet, and because it operates in piston to a higher frequency easily crosses to the tweeter while still in the heart of its range.

Lastly, the Visions are easier to cross to a subwoofer, and offer much more versatility. The Visions' unique MAPD bass loading allows micro-adjusting the mid-bass tuning to precisely match the amplifier driving them, the low pass network/amplifier driving the subs, and the room placement. For systems using tube or SET amplification to drive the monitors and solid state to drive the subs, this level of fine-tuning is invaluable.

Both loudspeakers fully embody their design goals: The Rhythms were designed to be the best full range loudspeakers we could make, able to stand alone in all but the largest listening rooms, capable of exceptional two channel performance with the most modest of amplifiers, and easily modified to work in most home theater systems. The Visions were designed to be the best monitor loudspeakers we could make, easily mated to and achieving their best performance with good subwoofers, optimized for home theater applications, yet fully compatible of performing wonderfully in most two-channel applications.

Like the Vision Signatures, the Vision-C is an MTM loudspeaker and shares the identical crossover design and crossover component quality. The differences are that the Vision-C was designed to be placed on its side either above or below the video screen, and because it will definitely be used with a subwoofer, the -C's low frequency alignment is a conventional aperiodic design. This configuration allowed us to reduce the overall cabinet volume by 50%, the rear half of the cabinet housing the crossover network. For the -C we supply only a low-Q Scan-Vent, and again the tuning can easily be fine-adjusted.

Like the Vision Signatures, the Vision-C is fully shielded. The Scan-Speak 15S-8530K-01's are shielded at the factory, and we add shielding the Scan Speak Revelator tweeters at the North Creek facility.

The Vision-C does require a minimum of 1/2" of space below the cabinet to allow the Scan-Vent to breath, so the side panels are extended below the cabinet and small spikes are provided.

............Jim K.

I would like to thank you for doing such a fine job designing these speaker systems.Your choice of speakers, the crossover networks and the cabinets. I am very happy with everything!

Bud M.,Denver