Borealis and Rhythm
Full Range Loudspeaker Systems
Historical Page, retired 2009
North Creek Design Goals
Each North Creek Loudspeaker Kit is conceived as a cost-no-object high performance two way loudspeaker system featuring high sensitivity, a detailed but romantic top end, smooth, natural, articulate midrange, exceptional imaging, and an aggressive, dynamic low end.
These sound like the design goals for virtually every midsized loudspeaker system; however, these goals are rarely accomplished. First of all, transparency throughout the midrange - the single most important element in high end reproduction - is difficult to achieve with a woofer larger than six or seven inches; however, bass response into the second octave at realistic listening levels requires significant air to be moved, virtually ruling out small woofers of conventional design.
Secondly, a transparent, floating sound stage with precise image focus is almost impossible to achieve with monopole loudspeaker systems of large dimensions, again ruling out larger drivers.
Thirdly, to avoid upper midrange deterioration due to cone break-up and crossover parasitics while insuring midrange naturalness and image stability, a low crossover frequency - below 2 kHz - and uncomplicated crossover topology is required. This rules out virtually all conventional tweeters due to both power handling and excursion limits.
The systems we present here achieve our design goals by fully exploiting the remarkable capabilities of the superb , custom-made SCAN-SPEAK 18W/8545SC 7" Carbon Fiber woofer combined with several silk dome tweeters made either by Scan Speak or North Creek Music.
Borealis in Zebrawood courtesy Lee Taylor and Co.
The SCAN-SPEAK 18W/8545SC is a woofer of remarkable design. First and foremost, the driver is designed for enormous linear excursion. This is achieved through SCAN-SPEAK's development of the patent-protected SD-1 motor structure, diagramed below right. Close inspection of the conventional motor (above) and SD-1 system (below) reveals the following:
The conventional motor structure voice coil length of 12mm or less is simply too short for reasonable output at low frequencies. Conventional top plate thicknesses of 6mm yields a peak-to-peak linear excursion of only 6mm (voice coil height minus air gap height = peak-to-peak linear excursion).
The conventional motor structure suffers from high second harmonic distortion at low frequencies due to an asymmetric magnetic field about the top plate; that is, there is more flux below the top plate than above.
In a conventional woofer, high amplitude excursion modulates the voice coil inductance:
The SCAN-SPEAK voice coil always surrounds an equal amount of pole, eliminating this source of distortion. The SCAN-SPEAK impedance curve is retraceable independent of drive level.
In a conventional motor structure, current within the voice coil creates dynamic magnetic flux which modulates the motor field by partially demagnetizing and remagnetizing the section of the pole surrounded by the voice coil. This phenomenon creates both third and intermodulation distortion throughout the midrange, and is the other reason why conventional woofer impedance curves are nonlinear.
The concave cone-shaped, vented pole top eliminates reflections between the dust cap and pole while cooling the magnetic structure.
The SCAN-SPEAK 18W/8545 cone is constructed of carbon fiber loaded paper and coated with damping compound. Damped carbon fiber is an exceptional cone material because it combines low mass with incredible strength, therefore it is extremely rigid at low frequencies yet can be easily controlled by the damping compound at mid and high frequencies. The 18W/8545SC exhibits nearly theoretically perfect performance for a 7" driver - including the rising response and gentle turnover before roll off.
One can find far more detailed information about the causes and solutions of motor-induced distortions the AES publications Loudspeakers, Vol. 1 and Vol. 2 (60 E 42nd St, NY, NY 10165). Suffice to say that the engineers at SCAN-SPEAK have used every resource to develop and manufacture a motor structure which minimizes or eliminates the common second, third, and intermodulation distortions found in virtually all conventional loudspeaker drivers, resulting in a 7" woofer with exceptional low end performance even at very high volume levels while providing midrange purity rivaling many smaller drivers. The SCAN-SPEAK motor structure is unique and patent protected.
The North D25-06S and D28-06S silk dome tweeters were designed by George Short exclusively for North Creek Music Systems, with excellent frequency response and impedance characteristics and requiring only a simple crossover.
The SCAN-SPEAK D2905/9900 Revelator represents the latest evolution of the tweeter which has long set the standard for musicality in soft dome tweeter design.
Comparing the North D25, North D28, and Scan Speak Revelator to conventional tweeters, one finds several differences:
Conventional tweeters are constructed with a short-coil, long-gap geometry. This provides high linearity with limited excursion (typically 0.4mm), but dictates very poor performance under high excursion. Conventional tweeters, therefore, must either be crossed over at a high frequency or be used only in low power applications. The North D25 is built with an under-hung geometry, with a short coil, tall top plate and extended pole piece, which extends the linear magnetic field below and above the voice coil. Both the North D28 and SCAN-SPEAK Revelator are constructed with a long-coil, short gap geometry; that is, they are built like a woofer. The North D28 also has an extended pole piece and copper Faraday sleeve, while the Scan-Speak Revelator has a Faraday Cap. The North D28 is diagramed below.
All three tweeters have a full 1.0mm p-p, more than twice that of conventional tweeters.
Conventional tweeters have a limited air volume behind the dome and a flat top plate, which encourages reflection beneath the dome.
Conventional tweeters immerse the voice coil in a thick magnetic fluid to cool the voice coil and damp the tweeter's fundamental resonance. While this is effective, the thick fluid creates frictional drag on the voice coil, slowing down the dome. Both the North D25 and D28 incorporate an extremely low viscosity magnetic oil surrounding the voice coil, to cool the coil while minimizing drag.
Lastly, the North D28 and Scan Speak Revelator employ an extremely thick, machined face plate, and all three tweeters feature countersunk assembly screws and provisions for countersunk mounting screws. This provides a perfectly smooth transition from the tweeter dome to the loudspeaker cabinet front.
The Scan Speak D2905/9900 Revelator has long been used in many European and American high end designs, including several that are considered by audiophiles and reviewers alike as among the best in the world. The North D25 and D28 are very similar in character, offering remarkable performance at reasonable prices.
The Borealis system is designed as a cost-no-object, stand-mounted reference two-way loudspeaker system. Constructed of finest drivers and most musical crossover parts available, the Borealis combines the definitive qualities of a mini-monitor - large sound stage, precise imaging, superb detail - with the dynamic low frequency performance of a much larger system.
The Borealis system has been optimized for the ability to communicate the emotion of the musical event like few other loudspeaker systems. The light, rigid carbon fiber cone reproduces every nuance of a performance without a hint of distortion. The speed and detail in the low and mid-bass is reminiscent of smaller loudspeakers, but with a much tighter bass line. The system also excels in dynamics and dynamic contrasts, as the long linear throw of the woofer can move tremendous amounts of air. Music is reproduced with the impact of a much larger loudspeaker, but with the agility of a monitor.
The Rhythm loudspeaker system is a cost no object, floor standing, full range WTW (woofer-tweeter-woofer) loudspeaker system designed and constructed with the finest drivers and crossover parts available. The Rhythm combines the speed and finesse of a mini-monitor with the raw power of a much larger loudspeaker system, while flawlessly maintaining the correct harmonic balance and timbral accuracy essential to high end reproduction.
History: The MTM (midrange-tweeter-midrange) loudspeaker style was first developed by Teledyne Acoustic Research (AR) in the late 70's as a high sensitivity loudspeaker system of controlled directivity. The style soon spread to other manufacturers, of which the KEF 104 was probably the most commercially successful. At the 74th AES convention in 1983, Dr. Joseph D'Appolito presented the landmark paper "A Geometric Approach to Eliminating Lobing Error in Multiway Loudspeakers". The paper clarified the acoustic qualities of the MTM configuration, and over the next few years it rapidly grew in popularity.
Characteristics: The MTM has several desirable performance characteristics that are difficult to achieve using conventional two-way loudspeaker designs:
Sensitivity and Impedance: First and foremost, the parallel-wired MTM configuration displays a 6dB increase in sensitivity when compared with the standard two-way. The sensitivity increase occurs because the driver effective cone area is doubled while the net impedance is halved (doubling current draw). Most high quality amplifiers have little difficulty driving the lower impedance, therefore the sensitivity increase is almost without negative consequence.
Radiation Pattern: When the MTM was first used in the Acoustic Research Magic Speaker, it was done so because destructive interference interactions in its radiation pattern created nulls in the same frequency region where the "floor bounce" usually occurs. It was later shown by Dr. D'Appolito that a positive interference lobe within a 15° window centered on the tweeter axis creates a large vertical listening position with nearly identical frequency response. Both of the above conditions are virtually impossible to achieve with conventional driver configurations.
Rhythm in Sapele Veneer for NY Stereophile Show, courtesy Lee Taylor and Co.
The 18W/8545SC is constructed with an enormous magnet structure and a very compliant suspension. Our average of forty samples over the last several years of production yields the Theile-Small parameters Qts=0.32, Fs=31.9Hz, Vas=31.5 liters. Small's EBP is 99.7, indicating a vented box. Over the years, we have found the QB3 alignment to offer the best compromise between bass extension and subjective bass quality. Therefore, our required cabinet volume is approximately 17.5 liters per woofer, yielding a tuning frequency of 39.6Hz and an F3 of 46.2Hz. The alternative construction, for the SBB4 alignment, requires a box volume of 18.1 liters, with a tuning frequency of 32Hz and an F3 of 54 Hz.
For vented box cabinet construction, we have found it best to target a QB3 cabinet and oversize the theoretically optimum volume by 15 to 20%. This extra volume provides the ability to fine-tune the system to correct for small aberrations created by inductor and speaker cable DCR, non-zero amplifier output impedance, and small variations in driver parameters. The loudspeaker cabinet volume can easily be decreased at a later date with the addition of fillers.
Driver position is with the woofer centered and tweeter offset on the fascia. The drivers are flush mounted and the fascia edges are radiused to minimize diffraction.
Access into the cabinet is provided via an access panel in the cabinet rear. Cabinet ballast, the woofer crossover network, North Creek Glop and acoustic stuffing are installed through this panel, and additionally the low frequency tuning can be adjusted and optimized by accessing the port tube through this panel.
Crossover design is the single most important aspect of loudspeaker system design, and also by far the most difficult. For most high performance systems, engineering time from concept to sign-off is 1% driver selection, 4% cabinet design, and 95% crossover.
All North Creek crossovers are developed based on the following principles:
Smooth, relatively flat frequency response on axis.
The 6dB Response Step:
The "6dB Response Step", also called the "Baffle Diffraction Step," is the most significant acoustic phenomenon one must deal with in crossover design, and also the phenomenon most often overlooked by amateur designers. Simply put, at the wavelength of sound roughly equal to twice the baffle width, the loudspeaker's radiation pattern changes from full-space (equal energy in front of and behind the loudspeaker) to half-space (all the energy in front of the loudspeaker). What this means to the designer is that the driver which measured reasonably flat in an infinite baffle anechoic chamber (the way most drivers are designed and measured) will actually have 6dB less bass and mid-bass when located out into the room. Hence, a loudspeaker design based on flat half-space anechoic frequency response and not corrected for the 6 dB response step may sound fine when flush against the front wall, but will be thin when placed out into the room where the sound stage is best. For our 9½" wide baffle, the step gradually manifests throughout the octaves bordering 712.8 Hz.
Note that in the WTW configuration (such as the Rhythm system), the 6 dB bass and midrange loss created by the 4pi acoustic environment is compensated for by the increased system sensitivity. The resulting system exhibits a 4pi in-room sensitivity throughout the lower midrange equal to the original 2pi anechoic sensitivity of a woofer alone.
Other Frequency Response Considerations
Because we require a monotomically decreasing voltage plot across the woofer terminals and a simple crossover topology, a driver with flat half-space frequency response is not suitable (otherwise, the crossover would have to attenuate throughout the 6 dB response step region, go flat through the region above the step, and then begin attenuating again to mate the woofer with the tweeter - see Dickason Loudspeaker Recipes Figure 4.44 for example.) The engineers at SCAN-SPEAK are well aware of this, and design their woofers with a rising frequency response above 1kHz and a smooth high frequency roll off. The combination of the 6dB response step and rising driver frequency response above the step creates a monotomically rising in-room woofer response, which can be easily corrected to flat response by a simple, monotomically falling low pass electrical crossover slope.
Both anechoic and 4-pi frequency response and impedance measurements were made using our Liberty Audiosuite measurement system (in MLS mode) and calibrated microphone. All measurements were taken at a high enough volume level to accurately represent the drivers' dynamic charicteristics, not their small signal behavior. The measurements were then entered into our Calsod CAD system for preliminary crossover network simulation.
Long familiarity with the SCAN-SPEAK D2905/9900 Revelator tweeter has shown that its natural low end roll off, in conjunction with a simple second-order topology high pass filter, yields an overall acoustic high pass characteristic of precisely third order. The simplicity of the lower order topologies - with only one reactive component in the signal path - will always outperform higher order topologies throughout the pass band, and the second-order topology with the trap provides both significant low frequency attenuation (imperative at high listening levels) and the ability to adjust the turnover Q.
To match the woofer to the tweeter, a third order acoustic slope is required. Electrically, the slope must begin at 200 Hz or so at about be 2dB per octave (to correct for the 6 dB response step), gradually maturing to the higher order.
Initially, we begin with an impedance-compensated, overdamped forth order topology, including damping resistors in series with all shunt capacitors and the first inductor being about twice that expected from formulae. While this is extremely complex, it provides a suitable starting point. With five optimizable reactive components plus what amounts to three optimizable damping resistors in the woofer circuit, and six optimizable components in the tweeter circuit, a filter with the correct electrical characteristics may be quickly obtained.
Analysis of the sum, power, and anti-phase curves of early simulations with a 3kHz target crossover frequency, revealed that even with reasonably flat frequency response, both the power and antiphase curves were asymmetric. We then began to massage the acoustic crossover frequency while adjusting for relative driver offset, and eventually developed several physically realizable possibilities of varying complexity that were worth popping together in the listening lab.
Rhythm Unlimited Revelator crossover and drivers (at right).
Subjective Evaluation and Final Crossover Design
It is at this point of the design process that one appreciates having a dedicated listening lab, measurement equipment, a couple of fast computers, and a few thousand crossover parts - plus an automated coil winder - at their disposal. Prototypes were constructed and listening sessions began, entailing several hours per day over several months. High end crossover design is 95% listening, 5% measurements; most professional designers can come up with half a dozen combinations that all measure fine in an afternoon. A completed system must not only measure reasonably good, but also sound harmonically correct and intrinsically musical over an enormous range of material.
Crossover design was eventually completed for both systems, and the final topology is shown below. This represents the best sounding combination, and the measurements verify that our objective goals were achieved. The tweeter section is a simple attenuated second order network with impedance compensation, while the woofer section is very low Q third order network with a damping resistor in the T leg but without impedance compensation. In both cases, the drivers' acoustic roll off is third order.
Note that the networks are completely point-to-point hard wired. The Rhythm Unlimited uses 10 AWG inductors, whilst the Rhythm Signature uses 8 AWG inductors.
The combined response is shown below, including the woofer and port close mic curves, and almost precisely matches a theoretical third order combination centered at 1.8 kHz, with the low- and high-pass frequencies staggered by a factor of 1.20, drivers in phase.
For both the Borealis and Rhythm systems, the frequency response is 45 Hz - 22kHz ±2dB. The zero level is at 60dB, and system sensitivities are 85.5dB and 90.5dB respectively.
Note that the antiphase curve (shown above for the Rhythm system) is symmetric about the 1.8kHz crossover frequency, the antiphase null is quite deep, and there is absolutely no region of destructive interference.
Rhythm system input impedance, normal and with impedance "Twister" correction circuit
The tweeter -3dB point is 2100Hz acoustically and 2400Hz electrically, well within acceptable limits. At its 500 Hz resonance, the tweeter level is down 36dB acoustically and a full 32 dB electrically (see the voltage plot above). Also note that the tweeter filter transfer function is monotonic. Lastly, note that the tweeter response is realized with only a single reactive crossover component in the signal path. Naturally, this implies the tweeter series capacitor is the single most significant circuit element and must be of the highest quality
The woofer network topology is greatly simplified because the SCAN-SPEAK 18W/8545SC woofer exhibits perfect L+R impedance at high frequencies. Unlike conventional woofers, this impedance characteristic allowed us to consider the voice coil inductance as a series circuit element instead of forcing additional conjugate circuits to compensate for it. The topology then became simple damped third order that is correctly terminated, therefore we have precisely third order acoustic output. Also note that the woofer voltage transfer function is monotonically decreasing above 150 Hz. The other advantage to such a low crossover frequency is that the woofer is crossed out while still in piston, so any high frequency non-minimum-phase behavior and driver variation is inconsequential.
The end result is a very simple crossover network with only three reactive components in the entire signal path.
Low Frequency Performance
Inspection of the close mic frequency response curve reveals that the port output is centered 38 Hz, very close to the vent tuning of 36 Hz. This actually represents the best sounding combination (the theoretical QB3 specification called for a 45 Hz tuning). The port is adjustable via the rear access panel, so one may taylor the tuning by as much as a half octave to best suite the associated electronics and room acoustics. The low frequency roll off is forth order below the tuning frequency, therefore the system is capable of considerable output into the high thirties.
This is of course the only important measure of a loudspeaker design's success. The criteria we evaluate are the system's overall harmonic integrity, its ability to create a convincing illusion of a live performance in the listening environment, and its listenability (a combination of the "goose bump", "foot-tapping", and "stay up late" tests). We don't consider a design completed until it excels in these three categories.
Harmonic Integrity: One would think that with modern test equipment this condition would be a given, but in reality it requires a very delicate balance between the low end tuning and midrange and top end voicing. Very small changes - on the order of 0.5 dB - over broad regions will completely upset this balance, and to further complicate the issue is the influence of the electronics and room. Our favorite test discs are Ry Cooder & V. M. Bhatt A Meeting by the River (Water Lily Acoustics 60997-0029-2) and Harry Connick, Jr. When Harry Met Sally... Soundtrack (CBS Records 7464-45319-2). The systems presented - with a very gentle rise of 1dB between 300Hz and 20 kHz on axis and a gently falling third-octave averaged room response - sound dead on.
The Illusion: In a few words: Sound stage, Focus, Presence. One must to use natural recordings of voice and acoustic music. The variations between venues is enormous, yet the system must recreate the dimensionality of each venue with equal ease. Focus and Presence are defined in lateral, horizontal, and vertical position. To this end, tight driver tolerances and 1% crossover component matching is essential. Our favorite test is track 6 of the Fairfield Four Standing in the Safety Zone (Warner Bros. 7599-26945-2), "Roll Jordan Roll". The Rhythm can focus so realistically down the middle and through the extremes that it is almost frightening. No kidding.
Image height requires an element of magic, and this loudspeaker has it spades. Our favorite studio test is the title track of P.J. Harvey's Rid of Me (Island 314-514696-2). Polly Jean's voice emanates from a precise point about four feet above and six feet behind the loudspeaker plane, literally top dead center.
Listenability: This quality has no correlational measurement. Once a system is listenable, it becomes almost impossible to subjectively evaluate because one enjoys listening to the music too much, and realizes only after the goose bumps have subsided that the goose bump test was passed. Our loudspeakers can do justice to everything from Bach to Zandig.
The 18W/8546 can be used in either the Borealis or Rhythm loudspeaker systems with only minor changes to the crossover network and cabinet.
The 8546 offers superior resolution in the upper midrange over the 8545, but is also less romantic. We generally recommend the 8546 for those using tube electronics throughout, and the 8545 for solid state and solid state/tube systems.
One can also use the standard 18W/8545 and 18W/8545-K with the Borealis or Rhythm with minor changes to the crossover.
Merging a subwoofer with the Borealis and Rhythm systems is relatively uncomplicated, although we strongly suggest an electronic crossover and separate amplifiers be employed for each system. Sealing the vent (by removing the access panel and replacing the port tube with a cover) is absolutely necessary, as is true of all vented satellites, because it forces the satellite low frequency performance to be second order high pass at the system resonance. A small series capacitor between the pre-amp and satellite power amp serves as a perfect first order high pass filter, resulting in a third order high pass characteristic overall. The subwoofer may be driven by a third order active low pass filter set at 80Hz. The subwoofer should be placed as close as possible to the room corners. We suggest dual for medium-to-large listening rooms.
North Creek Loudspeaker Kits are available packaged in component form. The package includes "soft matched" drivers (tested and hand matched to ± 1.5dB), fully assembled and tested crossovers, binding posts, grille fasteners, screws, nuts, bolts, port tubes, NCMS Soft Glue, other adhesives, and the information packet; in short, everything except the wood. The crossovers are fully assembled of ±1% hand matched components, and tested to be within ± 1% of the original designer's specifications. Color coded internal wiring is hard wired to the networks, as are the correct connectors. The first time builder can complete the project in two evenings.
Tower cabinets are available for the Borealis and Rhythm Revelator from Lee Taylor and Co.
Borealis North D25 "Aurora" Project Consists of "soft matched" 18W/8545SC woofers, Perfect Pair North D25-06S tweeters, all 14 AWG air core inductors, Zen high frequency film capacitors bypassed with Harmony capacitors, North power resistors, all crossover components hand matched to ±1%, TefFlex AG and Lex OFHC internal wiring, binding posts, etc; everything required to build the loudspeaker system except the wood. The crossover network is fully assembled and tested.
Borealis- North D25 "Aurora" Project ...$ (Retired 2009)
Borealis - North D28 Project Consists of "soft matched" Scan-Speak 18W/8545SC and North D28-06S drivers, all 14 AWG air core inductors, Zen high frequency film capacitors bypassed with Harmony capacitors, North power resistors, all crossover components hand matched to ±1%, TefFlex AG and Lex OFHC internal wiring, binding posts, etc; everything required to build the loudspeaker system except the wood. The crossover network is fully assembled and tested. Component list $1024.00.
Borealis D28 Unlimited Project (North Passion) Consists of "soft matched" 18W/8545SC and North D28-06S drivers, all 10 AWG air core inductors, Zen high frequency film capacitors bypassed with Harmony and Crescendo capacitors for the woofer section, all Crescendo high frequency film-and-foil capacitors in the tweeter series section, North power resistors, all crossover components hand matched to ±1%, TefFlex AGå an Lex OFHC internal wiring, binding posts, etc as above; everything required to build the loudspeaker system except the wood. The crossover network is fully assembled and tested. Component list $1,294.00.
Photo at right is the Borealis - D28 in the Parts Express cabinet.
Rhythm - North D25 Project:
Consists of "soft matched" 18W/8545 and North D25-06S drivers, all 14 AWG air core inductors, Zen high frequency film capacitors bypassed with Harmony capacitors, North power resistors, all crossover components hand matched to ±1%, TefFlex AG and Lex OFHC internal wiring, Texas binding posts, Big Toe spikes, etc.; everything required to build the loudspeaker system except the wood. Bi-Wired. The crossover network is fully assembled and tested. Component list $1,109.00.
Rhythm - North D28 Unlimited Project:
The woofers can be ordered as broken in "perfect quads" for an additional $70 per set.
Identical to the Unlimited project above but optimized for and supplied with the SCAN-SPEAK D2905/9900 Revelator tweeter. Slightly faster than the Unlimited and offers even greater resolution. The crossover network is fully assembled and tested. Component list price $2,062.85.
The drivers can be ordered as "perfect" (broken in and matched to ± 0.25dB) for an additional $100 per set. The '8545's are a "perfect quad".
Rhythm/Revelator Signature Project:
Absolutely the best of the best. The Rhythm Revelator Signature Project, which is the North Tempest in finished form, features 8-gauge inductors, fully cascade-bypassed Crescendo and NOS Military capacitors in both the woofer and tweeter sections, crossover components hand selected and matched to ±0.25%, drivers broken in "perfect pairs" (hand matched to ±0.25dB), fully shielded 18W8545SC woofers, supplied for bi-wiring. The crossover network is fully assembled and tested. This is simply the finest, no-compromise full range loudspeaker system we know how to build.
Rhythm/Revelator Signature Project ...$Retired per pair.
Rhythm/Revelator Signature Center Channel $Retired each
North Tempest Loudspeaker system msrp $8,800/pair, retired
Borealis Owner's Comments
Played one album then another and another until around 2am, just couldn't get enough.
They are ABSOLUTELY FANTASTIC. Bass tight and controlled, vocals and mid range sweet enough to bring you to tears and clean top with no hint of brightness. I have heard and felt things I never new were there.
The wee Plinius just eats the speakers, drives them very easily, no need to go over half volume any more.
Monday night was another long play session. I still need to get serious with the placement, but that will have to wait until I have all eight of my Big Toe Spikes.
To really describe these speakers is hard to put into words. Probably the greatest impression is how quiet they are, by that I mean when the music stops or goes quiet there is no singing cabinet or woofer, the music just stops. On some pieces its almost eerie.
Thank you for a great sounding and good looking piece of furniture, they are everything you said they would be.
I tell everyone about you and your product.
P.S. I just finished building a Borealis 9500 kit and I'm really happy with it, thanks for making these great DIY kits available and supporting the speaker builder community. --V.W., Paris, IL
So let me give you a personal review, mainly to say "thank you" .
I just wanted to drop you a note on the outcome of my project.. First off, I am in AWE of the size of the 8 gauge inductor coils. It is truly hard to believe their size and installing them in Lee's cabinet got a bit interesting. They're in and they seem to be the anchor of the system.
Just a quick note to say that I got my Borealis D28 project set up and running with about 40 hours on them now. All I can say is Sweet, very, very Sweet!
Thanks, Tyler R.
BTW - These are the strangest speakers I've ever owned. I do a lot of amplifier mods and like to listen to the results, but the Borealis defy analysis! I can no longer listen to my equipment - I can only listen to the beautiful music coming out of the speakers (wherever they are - when I close my eyes I can't find them). Still trying to get used to this - thanks :)
I'm writing to let you know that I am very pleased with the Borealis. I have finally broken them in- a friend brought over a rave album (Fluke) which at first I was worried because of the amount and frequency of the driver excursion but went ahead at full throttle for 8 hours (I left the house) and when I returned they definitely sounded better. I forgot how much pleasure there is in listening to music (not rave) through quality speakers. I am now considering the Vision for my future project. Thanks again.
p.s. - Lee Taylor's cabinets are perfect.
> Hi George,
Lee, the speaker cabinets arrived today. First, they are heavy! Then I
The Borealis is getting better all
Hello George Yes its John B. from Sydney Australia.I have implemented all
Rhythm Owners Comments
Update up completed North Creek Rhythms. They sound very cool. A guitar player was over last night. As he was sitting in the sweet spot he suddenly exclaimed, "I can hear the picks!" He had been drawn in completely by an Eva Cassidy Cd then he suddenly realized he wasn't listening to live music.
I was a bit nervous spending so much on speakers I had never heard before but as it turns out these are the best sounding speakers I have ever owned or listened too. Ive only logged about 60hrs on them so far but hey just keep sounding better and better. One of the first things I noticed about them is that no matter what volume they are played they sound great and have low end detail at the lowest volumes. Keep up the great work. I'll be purchasing more North Creek speakers in the future and I WILL tell anyone and everyone about the these great speakers.
Thanks you for the speedy reply and clarification; I hope CES went very well for you. I have had the speakers up and running for a little over a week now and I believe that I may have finally gotten them "locked in". Almost each day I was testing them at various distances from the wall and different tilt angles. My roommates didn’t want the speakers out very far into the room but I’ve managed to consistently move them out to a point we all can live with, close to 2 feet from the back wall. Unfortunately the layout of our room restricts us to ~6 feet of listening distance but the frequency range seems more balanced in this configuration. One interesting note: I was adjusting the tilt the night before last in an effort to get the image up a little higher. I sat down to have a listen and noticed immediately that the speakers were at quite different angles of tilt, and yet the sound (it was a Radiohead album) had a floating characteristic across the soundstage that wasn’t there before. Needless to say they are still like that and I can’t bring myself to adjust it anymore, lest I lose that quality. At this point I am very happy with the sound; the level of detail within and the distinction between different instruments is very impressive. My only quibble is that I would prefer a tad more fullness in vocals and guitar strings, but it may be caused by my room and/or the other major point I want to bring up, my processor. Right now I am using a decidedly midfi Onkyo receiver (an abomination, no doubt) and I get the feeling that it is holding me back. Eventually I will finish a diy amp I am working on that should be able to do them justice, but I will probably be stuck with this processor for another year or two. In any case, I look forward to eventually hearing what they can do with good electronics backing them up. One last note, last night I put on the Jurassic Park III dvd to see how they could do for home theater. Man alive!! The low bass these speakers put out is just amazing for their size. My roommates had to reign me in several times on the volume control but I have never heard dinosaurs like that before; it wasn’t only the bass, but there was so much detail in the various grunts and roars that made their size very palpable. Thank you George for providing such an excellent product at a very respectable price. Rest assured I will return to you when it comes time to add on surround and center channels, and I have appreciated your quick replies to my questions.
Regards, -George W.
I have made the Rythym Revelator Signatures about 2 years ago and find them to be quite excellent in comparison to commercially available brands here in St. Louis that were 2 to 4 times the price..... Thanks for any suggestion and many nights of enjoyable listening.
Hi, just wanted to drop you a note, and tell you that I completed my rhythm revelators. I could not be happier with my purchase! I have been in this hobby for a long time, and this was my first time building speakers, although I have always wanted to. I did alot of research before I bought my kit, and your companies designs, and innovations are the ones that caught my attention. They took alot of time to build, but I took my time ,and did a really good job on the cabinets. They sound incredible!! as good as I had hoped, and they are not even broken in yet. They rival many speakers at four times the price!! Anyway, just wanted to thank you again for making me believe that a set of speakers this good, could be made by someone with common sense, and who is good with there hands!! I am very interested in the thunder subs, and would like to integrate them into my rhythm system. Can you tell me if this sounds like a good Idea, and what is the best way to do this? I was hoping to do one per side,, I really like alot of bass is certain tracks, and have a very big room.
Best regards,,jon a.
My Rhythms are well broken in now and sounding great! I was able to take them to a large DIY audio meet this past weekend and everyone seemed quite impressed, even though there was neither time nor space to really set them up properly. One thing I particularly enjoy with these speakers is the bass. They seem to have the perfect balance for both HT and music and it suits my tastes perfectly. I have been considering adding in a subwoofer, since I watch a lot of movies and would like greater extension and greater spl capabilities on tap. I’ve taken a good look at your subwoofer offerings, but you don’t seem to carry exactly what I’m looking for so I was considering coming up with a separate design. I was wondering what the Qtc of the Rhythm cabinet was, so I could try and match the sound as closely as possible.
Thanks again and do let me know if you currently have any more sub designs in the works, particularly with a Vab < 120L and ~112dB at 20hz capability in a large room.
Kind regards, -George W.
I am glad you are enjoying them so much!
Which DIY event, may I ask?
The way to build your sub is to use a pair of Thunder's. This is 110dB without clipping and will reach 112dB no problem.
For a very large room, I suggest you consider stacking the Thunder's (2 woofers + 2 PR's per side). This was their original intent, and in this configuration 116dB clean is possible.
Thank you! --George
Two years ago I purchased a Poseidon subwoofer from you. With the purchase of
While talking to my 15 year old son about what he would like for Christmas this year, he stated that he would like to build his own set of North Creek speakers with me!!! I couldn't be happier.
Dear North Creek;
First I must tell you that I have completed the Rhythms with the Kevlar Scan speak drivers, and I have 150% satisfaction! Broken in, every thing as promised in performance. I have a cabinet maker that made a very unusual alteration cosmetic to the cabs you suggest: Stunning in appearance and performance. I will be sending in a hand letter to George, and will toast him and his Rhythm Achievement. Yes- Pictures WILL follow as they are stunning. Yes, I will be building more as soon as my old gear moves on E-Bay. LOL. -Alan Z.
Hi George, I don't know if you recall but I had purchased two systems from you a while back. The Borealis unlimited for myself and the Rhythm / Thunders for a friend. They are both up and running and sounding great. Many stay up late nights just like you said on your web page, listening to lots of different music, that just sounds amazing now. Both of us are very satisfied with the products you designed and now have the itch to start building more. But as our luck would have it you are now discontinuing your DIY outfit. I do have one regret and that is that I didn't order a pair of Thunders for myself. They are the best sounding subs I ever heard. Well thanks again for designing such great products and taking the time to answer all of our emails. If you ever decide to have some more DIY projects, come across a pair of thunders, or have a sale on some products please let me know, like I said we have the itch. I have included some photos of the 3 Borealis but don't have any of the Rhythms / Thunders as of yet.
Thanks Michael D. A.