The North Acoustics’ Kitty Kat Revelator was conceived of as a near-wall-specific reference-level
full range loudspeaker system capable of high SPL and exceptional dynamics when
being driven by medium powered valve or transistor amplification

Those familiar with high end loudspeaker design will immediately recognize these as a family of competing goals. Never before has a full range monitor loudspeaker been built, neither has a reference level near wall specific™ monitor. Both high efficiency and bass extension have always been the antitheses of a bookshelf-sized loudspeaker.

With the North Acoustics' Kitty Kat, by employing a specially built woofer and a computer-optimized cabinet and port tuning, we were able to overcome the conflicts, achieve our goals, and develop a loudspeaker that is really something special.

The Scan-Speak 15W with our crossover and 14 liter cabinet volume and optimally tuned port delivers rock solid bass to 38 Hz and still has a bit of output in the high 20's.

The tweeter selected for the Kitty Kat Revelator is the North D28 silk dome. The D28 has a low fundamental resonance and more excursion capability than many midrange drivers, making it very well suited to mate with the 5 ½" woofer at the 1651Hz crossover frequency. Also, because it is constructed with a Faraday sleeve that extends above and below the voice coil’s maximum excursion, the D28 has a gently rising response with just a touch of sparkle at the very top end. The North D28 also exhibits intermodulation and harmonic distortion an order of magnitude lower than any conventional tweeter on the market.

The key to designing a great sounding loudspeaker is in its voicing. Simply put, voicing is the process of balancing a loudspeakers’ low end strength, mid-bass richness, midrange liquidity and top end sparkle such that the system sounds both natural and involving. Measurements are useless when it comes to voicing, it can only be done by ear. One can easily hear a small fault in voicing in 30 seconds of casual listening, but it takes months of serious listening and design time to get it right.

Of course, some elements of voicing also depend on personal preference, which is why some loudspeakers are very good at reproducing some types of music and not nearly as good with others. A loudspeaker designed purely for classical music, for example, generally does not sound that good with rock and roll (although the reverse is not necessarily true).

The Kitty Kat, like all North Acoustics’ loudspeakers, are voiced with a bit of slam at the bottom end. There are two reasons for this: 1) the Kitty Kat has very little output below 30 Hz, so voicing the loudspeaker without slam would make it sound lean overall. Therefore due to the absence of output in the lower half of the bottom octave, a little extra presence the octave above it balances the overall presentation, and in fact the Kitty Kat sounds like it goes a lot deeper than it does.; 2) subjectively, on most music, slam factor is way for fun to listen to than the absence of slam factor.

Throughout the midrange, the Kitty Kat measures almost ruler flat and what variations it has from flat are dips. Dips are always better than peaks, as a midrange with dips will err on the side of forgiving, where as those with peaks will err on the side of over-emphasis. Other than a tiny wiggle though the classic BBC "dip" region centered at 3kHz, from 200Hz to 20kHz the Kitty Kat measures an amazing 87dB +1, -1.5dB. This is a window of over six and a half octaves.

Based on independent measurements, the Scan Speak 15W woofer also exhibits the lowest harmonic distortion of any mid-woofer on the market, and it is this absence of distortion which allows the driver to be both revealing and forgiving at the same time.

The North D28 tweeter is responsible for the top end, and here is voiced to be ruler flat 6kHz with just a tiny touch of sparkle in the top octave. A little sparkle here makes the overall sound of the system be more intimate on serious listening and faster when listening casually. Also because the slight rise in frequency response is built into the dome design, the crossover design is simplified which allows a straighter signal path and facilitates getting the most out of the highest quality crossover components.

 Measured Performance

The Kitty Kat’s frequency response is shown below. The low frequency curves are taken with the close-mic technique, with the port output scaled via its area ratio to mate correctly with the woofer output. The midrange on up is measured at two meters under anechoic conditions with the exception of the rear wall, which is 3" behind the rear of the loudspeaker. The measurement is set up this way to properly reflect how the loudspeaker system would test in the actual listening room.

As described above, the Kitty Kat measures 40Hz to beyond 20kHz +-2db, and through the critical midrange is +1, -1.5dB. System sensitivity is 87dB, very high for a true bookshelf monitor.

The antiphase null is an excellent –24dB, indicating nearly perfect driver integration throughout the crossover transition region.

The Kitty Kat’s input impedance is shown above, both with and without the (optional) impedance twister circuit. Without the twister, the system has impedance minimums of about 3.5 Ohms at 300Hz and 5kHz, while the impedance maximums are evident bracketing the 37Hz port tuning frequency and near the crossover frequency. All told, the Kitty Kat without the twister is a very easy load for most modestly powered transistor amplifiers to drive, and 15 Watts minimum is recommended.

With the twister in place, from 300Hz up the impedance measures 5 Ohms +- 1.5 Ohm, which is ultra-stable. This is a better match for valve electronics or transistor amplification that is picky about the loudspeaker load.

The most striking aspect of the Kitty Kat’s sound quality is how riveting it can be. In fact, even when outside the listening room, the Kitty Kat’s have such a robust bass presentation and rich, wealthy midrange that it actually draws one in just to get a closer listen.

This loudspeaker even succeeds at this with older recording; Led Zeppelin’s "Kashmir" (from Physical Graffiti, Swan Song SS200-2) not only revealed layers of material but also communicated that the Led Zep boys were getting along very well at the time and had a great time recording the album. Similarly, the Beatles remastered recording of Rubber Soul draws one in for a listen because it sounds so naturally rhythmic and involving.

Sitting down with the Kitty Kats, listening seriously, one is immediately taken by its absence of distortion throughout the midrange and top end. It is a unique quality that the midrange can be fantastically detailed and revealing without being even remotely analytical. This contributes to the loudspeakers’ ability to be involving while it is still relaxing.

Janis Ian "Where the Silence Falls" (Putumayo 128-2) for example, the bass drums have extremely dynamic slams, yet the singer’s voice stays liquid, focussed dead center and well above and behind the loudspeaker positions. Way back at the far left edge of the soundstage, one can hear a rhythm guitar play about three measures and then vanish.

Lower down in frequency, Don Williams "I'm Just a Country Boy", the Kitty Kat also shines. Vocal inflections are carried with remarkable clarity and immediacy and a complete absence of coloration, and with just the right amount of robustness.

Voicing is definitely full range in nature, and even though the Kitty Kats 3dB down point is only 41Hz, their 10dB down point measures a very low 28 Hz and they sound like they are a much much larger loudspeaker. These Kitty’s can rock and roll. Beck's "Scarecrow" (Guerro Interscape B0003481), for example, the driving bass guitar effortlessly fills the room while Beck’s vocals are clear as day.

For those looking for a reference quality near-wall monitor that is capable of recording studio resolution while still being forgiving, the North Kitty Kat is their best choice.

It was a long process, as after trying several different woofers from Scan Speak, SEAS and Peerless, and not being able to get the low end extension I wanted, I finally ended up modifying a Scan Speak 15W by adding a huge bucking magnet (to increase its motor strength) and adding a special coating to the cone (to smooth out its frequency response).

The crossover design was a bit of work. The modified woofer has a very powerful bottom end, and to keep it from overpowering the rest of the spectrum an absolute minimum of reactance was required until just below the crossover frequency. The best way I can describe the finished low pass network is that it uses a very gentle application of response shaping circuitry to get the required slopes.

Because the North D28 tweeter was designed with a very slight rise at the top end, the high pass network is a straight forward second order with only a single reactive element in the signal path. For this we use a full cascade-bypassed Crescendo film-foil capacitor bank.

All of this said, the most striking aspect of the Kitty Kat is its voicing. The bass goes so deep and it is so dynamic that it is hard to believe it is coming out of this little box. It just effortlessly energizes the room.

The midrange is perfectly balanced and the transition to the tweeter is seamless. Vocal clarity is simply stunning. All told, the Kitty Kat's have a sense of continuity about their sound that I have rarely heard in loudspeakers at any price, and never when stuffed practically against the wall.

Since the NY show, we have played the Kitty Kats to several individuals whom visited the North Creek Showroom, and opinion is unanimous that it is the best near-wall loudspeaker any of us has ever heard.

I just want to say that I am really enjoying the total Kitty Kat package. The quality and build of the cabinets were top notch. Especially since my wife liked the veneer.... Lee you were right on the grills, you are simple are not going to get any reflections from the grills. I am glad that I paid a little extra from them.

Over the weekend, I did some A/B music testing with the Kitty Kats and my main towers. As far as quality, the Kitty Kats came out on top. It was kind of weird, the Kitty Kats had a wide sound stage but the sound was very neutral. I can not think of any other words to describe it. Compared to my tower speakers, the towers also have a wide soundstage but the sound seemed to have some sort of surround effect. This surround effect made the music reproduction sound slightly colored. I did not notice this with the Kitty Kats. I guess this would make the towers better for HT rather than 2 channel music listening.

The the next major difference I notice was the bass response. With the powered woofers on in the towers, the bass coming from the Kitty Kats were not as loud but it was very close. This is pretty impressive for one 5.5" driver. The tower speakers I own can also be purchased without the powered woofer. So I shut off the woofers and compared the bass response again. This is were the Kitty Kats really shined. There was no comparison, my towers without the powered woofers could not compete. Even my wife noticed this.

I am so excited about the potential of these Kitty Kats. So much so that I am know looking to piece together a 2 channel music system. This is something I was not really considering on doing in the past.

Thank you George and Lee for all the help.

Regards,

Akono G

I hope you continue to sell some very high end speakers as I am definitely a convert and NCMS evangelist.

Troy, Al.

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