May

May 1

GET DOWN, BABY!

The arrival of the first of the Bassmaxx ZR-18s happened today. Let me first state that everything that was claimed about them is not the least bit exaggerated.

The first units shipped from Texas and arrived here surprisingly quick (good going DHL ground service) in three business days. I uncrated them from their unusually large containers. My first impression was that you could drop these off a building and probably not do much, if any, damage to the speakers. These are the Caterpiller D9 bulldozers of subwoofers.

My first test was an open-air test, the preconditioning test that I give all my speakers before installation. Only this test was quite a surreal experience. Due to the Beehive pot core design, the back of the neodymium magnet is a cooling port for the voice coil. I could easily monitor the temperature of the voice coil. So I began feeding a 20Hz sine wave into the driver. As I ramped up, all I heard was a fundamental 20Hz, no overtones or harmonics--it sounded almost as if it were mounted in a baffle. As the excursion ramped up, I carefully monitored the air temperature of the vented air--it was cold. I'm very cautious with this test, because I burned up an Electro-Voice 18BX a couple of years ago with this test/conditioning procedure. But there was no danger here. 50 watts, and a nice excursion over well over an inch. I ramped it up to the Carver M-500's maximum output--a little over 220 watts per channel and watched the cones move at a distance and velocity that is beyond comprehension. In fact, everything was a blur--I could not see the cone, just a transparent blur, like a shadow, watching from the side of the basket assembly. Bizarre indeed. It becomes apparent that this not something I would call a speaker, but more like some sort of a piston device for industrial use.

So how does the Bassmaxx ZR-18 cool itself? Three ways were explained to me: black body radiation, extreme forced air cooling, and the fact that the coil is always in the field, thereby converting most energy into electromotive force, rather than heat. Notice the smaller set of vents just below the magnet assembly? Air moves through those, and is forced out the center port in the back of the magnet pot. The amount of cooling possible with supersonic air velocities jetting by such a tight gap is not to be underestimated. I am told that these woofers are used at rave concerts in the middle of the desert and raves run for 12 hours non-stop. The speakers are driven with 4,000 watts per driver and, under those conditions, the magnets get so hot that you can't rest your hand on them--yet the coils remain adequately cooled. Now Bass Pig doesn't run his speakers at full power, or anything close to that, for 12 hours, so it's unlikely that these will ever get luke warm. Which brings me to another thing: Power Compression. The conversion efficiency of a woofer drops off as the coil heats up (resistance rises with temperature), so conventional woofers will not scale up in SPL from their 1W/1M rating. Most woofers have about 4-5dB power compression when driven past half their rated power. That means that the maximum SPL is much lower than, say 30dB above the 1W SPL. With the CGN, the coils stay so cool that their resistance remains constant--in fact, the Thiele-Small parameters are the same, whether the power input is 3W or 3,000W. In practice, this results in the performance gap between this speaker and other speakers, widening as we get up in the the very high power levels. That goes without saying that most commercial woofers are pretty much toast after 500W of power, to say nothing of the distortion they produce at half that power. The CGN will start to pull ahead in SPLs as the power goes up, in a comparison with mass-produced commercial woofers. It's really a cool thing to find that these woofers keep getting louder as the power goes up, while the rest of the conventional woofers reach a limit and just won't produce any more SPL. Sensitivity ratings don't tell the whole story. It's not hard to achieve high sensitivity at 1 watt. But at 1,000 watts, all bets are off and the performance tanks. And that's what separates the CGNs from the mass-produced woofers.

Let me back up a bit... the cones--if you could call them cones--are 1/4" thick, two-layer fiberglass piston with honeycomb reinforcing pattern between layers. The darned thing is like a fender on a Corvette. Solid. The frame is a heavy die-cast affair with a shiny metallic paint coating. The magnet assembly is a brass-colored steel pot, lined with neodymium magnets--right inside, facing the coil. Unlike conventional drivers, where the magnet is a weak ceramic thing, remotely attached to a pole piece to carry greatly-reduced flux to the coil, this thing has the magnets right at the coil for the full flux to envelop the coil. The pot was designed with finite element analysis to provide a uniform field intensity over the length of the gap. That explains why I heard no other sounds other than 20Hz during my open air testing.

Another thing that was explained to me about this kind of magnetic motor system is that a common problem with conventional woofers, "magnetic flux rectification" is eliminated. Conventional woofers, when driven hard with very low frequencies, will begin to 'float' with the voice coil outside the gap. Once this happens, the woofer is no longer following the input signal. The design of the CGN woofer eliminates this problem because the coil is always in the magnetic field and the field is consistent across the entire excursion range.

The pot is mounted to the basket with 6 1/4-20 stainless allen screws. I was able to disassemble one unit and inspect the voice coil and see what was in the gap. Just try that with a commercially-mass-produced woofer! The elegance and simplicity of the design is amazing. The voice coil itself seems to be a laminate of aluminum, possibly Kapton and fiberglass and is about 8" long to reach down into the gap. The coil itself is a black anodized thing. There is a double spider, but what's interesting about it is that the coil lead in wires are woven into the spider and there are not one--but two--lead wires per side! I was a little confused at first, but the way you connect this is one wire on the left set of dual terminals and one on the right set of dual terminals. I know the heavy wires can handle 30 amperes, so I wonder why this speaker has over 60 amp capacity on the voice coil wires. This could be a clue as to the class of power this beast is built to operate at.

I spent the next few hours unmounting the E-V 180Bs from the right subwoofer cabinet, after doing a baseline sensitivity test and plotting the figures. Installing the CGN drivers was somewhat of a pain in the ass. There is a thick rubber boot that encircles the edge of the 18.5" frame, which serves as a universal gasket, allowing front or rear mounting to a baffle. Aside from that, there is the butyl rubber surround, whose mounting flange is 1/4" thick rubber, glued to the frame. Well, a lot of the work was in cutting holes for the screws to pass through this thick rubber. Kind of like cutting a car bumper rubber, very tough. After some work, I got both drivers mounted.

Testing revealed that I'm going to have to find a way to anchor the cabinet down somehow--it started traveling as I ramped up a 20Hz tone to the kilowatt level. This 200lb cabinet danced around like a spastic epilepsy patient! The drivers demonstrated that they made effective propulsion devices, as well as producing insane quantities of bass.

The sensitivity test was encouraging. The highly efficient 180B, at low power, about 1 watt, had about the same sensitivity as the CGN driver, despite the incredibly massive cone assembly of the CGN. Without Neodymium magnets, this driver would not be practical. The high flux density enabled this massive piston to produce the same SPL sensitivity as a leading high efficiency driver. So at least I don't need gargantuous amplifier power just to get some output from it.

What I did notice right away was that the output was cleaner than anything I had heard before. Where the previous drivers seemed to hit a ceiling and start producing harmonics with no further fundamental output, the CGNs just kept cranking up and up. As the excursion approached about 3", I noticed that shreds of fiberglass acoustic insulation were being jettisoned from the vent, ending up 20' across the studio floor. I also broke the sound barrier--the vent velocity exceeded 1150 feet per second. There goes any plans to put grill cloth in front of these speakers.

The listening experience was visceral. Instead of shying away from music with the "20Hz thump", these woofers thrive on that kind of material and seem to goad me to turn it up even more. The problem now is that the ceiling, walls, and everything in the room make dreadful noises from all the violent shaking! It rains down dust from the ceiling tiles, too. While I've eliminated speaker distortion, I've greatly exacerbated building structural distortion--the building itself makes its own noises in response to the vibration, and it's distracting and quite nasty.

Overall, a worthwhile upgrade with untapped potential. And quite a show piece. Just watching it make a 3" excursion is a freaky experience. And it does it without making any ugly noises.

In a couple of days, the rest of the drivers will arrive and I will installed numbers 3 and 4 on the left side. At last, I can turn off the limiters on the crossover network. Even with just the two now, I can really feel the difference--especially upstairs, where the lower organ pedal tones really move the floor. I dread what it would be like without all the shock absorbing insulating layers I had built into the ceiling below! This would have destroyed an ordinary wood-frame house. Oh, the power!

May 17

I FEEL THE EARTH, MOVE, UNDER MY FEET

Something interesting happened today while I was listening to some Korean pop music. Mind you, I only managed to get the right subwoofer setup installed with CGN woofers. The remaining drivers on en route from California, after some delay, and should be here by the weekend. Anyway, getting back to the Korean pop, I was listening to an album by a band called Kiss and there was some subsonic 'noise' that comes and goes throughout parts of the recording. I became aware of this not because I could hear it--I could not hear it over the rest of the music--however, I feel the 8" thick concrete slab beneath my feet quiver from time to time. I can also feel it in the air, directly, but the slab shaking at that low a frequency was something new.

Incidentally, this album borders on the genre known as 'Hip-Hop'. I'm not a fan of the genre, as heard in America, but this Korean album has a flair and a style to it that is really cool. I like it.

So why am I listening to Korean music now? Well, last month, my wife bought a Korean drama series on DVD by the title Save the Last Dance for Me. She was watching it while I was eating dinner in the living room. I got involved about halfway through the 22-episode series. All I can say is that it's a masterpiece of perfect timing, intense drama, acting that is indistinguishable from real life, and a complicated and twisted plot that is full of unexpected surprises.

In brief, it's about the son of the chairman of a powerful corporation, who has an accident, loses his memory, and is discovered by a the family of a young lady who runs an inn in beautiful Gang won-do province. For a year, the guy is living with them and the innkeeper's daughter falls in love with him. But events conspire to separate them, his memory returns after he is effectively kidnapped by the company's former lawyer-turned-president, and he returns to his corporate life as the GM of his father's company, his fiancée and his responsibilities. He does not remember the girl from the inn, but she comes to Seoul to pursue this guy and try to find him. I will leave the strife, pain and suffering that the three main characters go through as this love triangle goes ballistic in the coming episodes. There are many characters that are just loveable and funny, and the company seems like a big, happy family. Needless to say, this is where the Korean writers and actors weave a powerfully-emotional work of drama, unmatched by anything I have seen stateside.

Also notable was the music soundtrack. It had many nice songs on there and some of them have some sweet sounding bass guitar work. I secretly ordered the soundtrack CD, so I can give it a good listen.

Well, I wait patiently for the remaining drivers to arrive so I can install them. With two sets of CGN subs running, the difference will become very obvious. The next step is to secure a good deal on some 6,000W QSC amps to drive them. These woofers have so much headroom that if they had sufficient amplifier power to drive them to their full potential, they'd blow the rest of the system away. Stay tuned for this earth-shaking drama! :-)

May 21

THE SWEETEST BASS GUITAR

Today's mail brought the CD I had ordered from Korea, the soundtrack to Save Your Last Dance for Me. The music sounds even better than on the DVD. 18 tracks of sheer heaven. Many melancholy ballads, done with a sensitivity and musicianship that is second to none. I was blown away!

Of particular interest was a Korean-titled track, the 7th on the album. It's kind of a sad piece, maybe because it is played during some sad reminiscence scenes in the series, but the bass guitar part is out of this world. And there's a really tight kick drum during the latter part of the intro that makes me afraid to turn it up too much because it seems that the roof might fall in. The bass player hits all the low notes, sort of like he's playing the part of a sub-harmonic synthesizer, but he's actually playing down that low. Normally, pop music usually stayed in the octave above. This stuff drills to the center of the earth. That my kind of bass! It has to be a six string bass. There are notes that fall below 30Hz. And oh, so sweet. The kind of bass that would make any bass freak have wet dreams and be left wanting to know what make and model guitar and processing made these beautiful sounds.

Oh heck, instead of me talking about it, have a listen to a sample of the intro HERE.

PCSD 00135

This album is colorful and widely-varied in styles. I like nearly every track on this jam-packed album. While Japan, my former champion of music has been passing it's peak of greatness, it seems that Korea is now at the top of its game in the movie drama and music arena.

My wife requested another Korean drama title, and I ordered it for her last week. I wonder if the next one will be as good as Save Your Last Dance for Me was.

May 27

ADDENDUM CGN IS/IS NOT BASSMAXX

I got an e-mail from the supplier of my specially-manufactured subwoofers and a lot of confusion was cleared up about the genesis of this driver and its current designation. Earlier, I had been referring to them as CGN-1808s, however, I have learned that CGN Audio Labs does not make this particular woofer. They supplied the engineering for the B-hive motor (the neodymium magnetic linear motor system used in the Bassmaxx ZR-18s. The rest of the design, the fiberglass cones, the suspension components, etc, are exclusive to Bassmaxx. So I've updated references to the name of the drivers to clear up this confusion. Folks have been e-mailing me asking about these drivers and where to get them. I myself wanted to know more about what I have here. So this e-mail I received was very illuminating.

Meanwhile, I am negotiating a satisfactory price on some QSC Powerlight 6.0 PFC amplifiers to run the new ZR-18 subs. The largest sound company on the west coast has about a hundred of them available for me to purchase. I just need a couple. We'll see how this turns out.