Genesis Advanced Technologies G928 ServoSub subwoofer
|Genesis Advanced Technologies G928 ServoSub subwoofer
|Force Meets Finesse|
Change is good
In a recent conversation with some of my audio purists’ buddies I was shocked to find out that they all believed in the benefits of adding a subwoofer to their two channel audio systems. In the past we would joke about how it would be considered an act of audio treason to own or even mention the words subwoofer in the same sentence as two channel high-end audio.
I would surmise that the resistant attitude is two fold. First, the majority of the time when the word subwoofer is uttered it is usually preceded by ‘home theater’ and second, my friends and I were all fortunate enough to have systems that reached down deep into the lower 20’s if not all the way down to 20 hertz. However, I’ve always felt that regardless of the reported specifications for a given brand of stereo loudspeakers that a cleverly designed subwoofer implemented correctly into a two channel audio system could produce some positive results.
One of the subwoofers that I know that fits this description is the Genesis Advanced Technologies G928. The G928 is designed with a proprietary servo-controlled bass system that uses a unique tool called an accelerometer. As its name implies, an accelerometer is a sensor that constantly monitors the woofers acceleration and the servo-system compares it with the input signal. When the circuit recognizes any kind of differences between the movement of the cone and the input signal, then corrective action is applied to the woofer cone to reduce excessive movements if required or accelerate the movements of the woofer if a delay is detected. The integration of this circuit into the design of the G928 helps to reduce distortion and improve bass response by starting and stopping the woofer instantaneously.
This ingenious feature is used in quite a number of Genesis products that I’ve heard including the newly released G5.3, and I wondered how a standalone version of the subwoofer would perform. So I placed a call to Mr. Gary Leonard Koh, president of Genesis Advanced Technologies and waited for a brand new, beautifully constructed, high gloss, jet black G928 ServoSub to arrive.
Take a Deep look inside
Surprisingly, the Genesis Advanced Technologies G928 looks essentially the same today as it did when Robert Harley reviewed it in 2000 and raved about its merits as a home theatre subwoofer in The Perfect Vision magazine. The G928 is still a sealed cabinet design with dual side firing woofers and a decorative gold embossed Genesis label on the front. The dimensions have increased slightly to 17 inches wide by 16 ½ inches high by 15 ¾ inches deep and the total weight is 76.4 pounds. The control panel remains on the back and when Mr. Harley reviewed the G928 it was only available in a faux black ash finish and was priced at $1,500.00. Since taking over the helm at Genesis, Mr. Koh has made some significant changes to the G928 but he has elected to keep the model number the same, similar to how Porsche did not want to tamper with a good thing and continues to this day to market and sell the legendary 911.
In 2001 Mr. Koh’s first task was to upgrade the G928’s cosmetics and offer higher grade finishes like the stunning high gloss black, premium rosewood, and gorgeous birds eye maple. There was a modest price increase to $1,850.00 for the black ash and the premium finishes were available for a slightly higher cost of $2,150.00. The cabinet was also constructed of better-quality, high-density 1-inch thick MDF on all sides (including the internal braces), which made it 33% stiffer than the earlier version.
In 2002, with home theater gaining in popularity and sales, an LFE input for home theatre was added. This allowed the G928 to have the flexibility to augment a pair of loudspeakers, and also at the same time serve as a source for LFE. Both bass and LFE inputs are independent of each other and have separate gain controls. Also in the same year, the G928’s amplifier section was upgraded with a 1kVA toroidal transformer. The standard black ash finish was discontinued, and the higher quality options were offered as standard finishes and the price was set at $2,250.00.
For the next couple of years the engineers at Genesis did not make any major changes to the G928. In 2006 the existing woofers in the G928 were replaced with the same state of the art drivers developed for their top of the line, highly acclaimed Genesis 1.1 loudspeaker that retails for no less than $185,000.00! The newly developed 12-inch woofers are now made up of ribbed aluminum with higher excursion motors, bigger magnets, and stiffer cones. This allows the G928 subwoofer to have a greater impact, lower bass (now F-3 at 18Hz instead of 20Hz) and lower distortion. Finally, for 2008 the G928 ServoSub has a brand new amplifier, using some of the technologies developed for the newly released solid state Genesis Reference Amplifier. This amplifier is even better and faster than the old amp.
The current price has been raised to $2,600.00 and the G928 has been re-designed to be just as formidable in a two channel system as it is in a home theatre arena with a better cabinet, better finishes, better amplifiers, better drivers, and a better power supply. With just about everything from the inside to the outside upgraded over the years, it seems like the only thing that isn’t better than the original design is the grill cloth and the dust cover.
The Control Section
The controls are very well labeled and are fairly easy to use. There are rotary knobs for the LFE and Bass gain and the low pass filter. The filter settings are adjustable from 40 Hz to 138 Hz. A toggle switch is used to set the phase at either zero or one hundred and eighty degrees.
Two pairs of bass inputs are included, high level, (stereo speaker posts) and low level, (stereo RCA) preamp inputs. The LFE has one RCA input and one RCA output. Slightly below that is an ungrounded receptacle for a power cord and a rocker switch to turn on a plate mounted, 500 watt Class D switching amplifier. A class D amplifier is the perfect choice for a subwoofer because a lot of power is generated with out the side effects of high heat and low efficiency.
As with most subwoofers the unit is pretty simple to set-up, but I would strongly recommend that you read the owner’s manual first because not only is it very well written but it also contains some valuable information about the G928. When I hooked up the G928 I only tested it in a stereo format because Stereotimes is a dedicated two channel audio magazine. But before we get into the review there is one more vital piece of information that I think I should share with you about connectivity.
According to Mr. Gary Leonard Koh, “the power amplifier to powered subwoofer interface is extremely interesting. It is a low-impedance to a high-impedance circuit. Interconnects are mainly high impedance voltage drive, and speaker cables and speaker connections are low impedance, current drive”. If the subwoofer (high input impedance) is driven directly from the power amplifiers speaker posts (low output impedance), or connected to the binding posts of the loudspeakers, again low output impedance, an impedance mismatch can occur. If a regular loudspeaker cable is used, the results will be less than stellar. Regular interconnects would be a very good option because of higher impedance characteristics but unfortunately source to source interconnects are terminated with RCA’s or XLR’s. Therefore the most viable solution is a special cable that has higher impedance specifications similar to interconnects terminated with spades or banana plugs. Hence, Genesis adopted this special "jumper" cable that serves as a great conduit for the signal to interface between the loudspeaker output and the Genesis ServoSub for optimum results.
Because the G928 ServoSub operates below 138Hz the Genesis subwoofer when used with the special "jumper" cable will stay coherent at low frequencies even when delivering minuscule amounts of current and should not be affected by phase shifts. This cable also helps to eliminate reflections and can be purchased from Genesis for a nominal fee. However, some manufacturers will try to get around this impedance problem and will recommend that their subwoofers be driven with preamp outputs before the signal is even sent to the power amplifier. This is something that Genesis’ feels is a substandard way to interface the subwoofer with the loudspeakers because it reduces the integrity of the coherence between the two transducers and should be considered as a last resort because of the potential for phase shift and group delay! This problem is exacerbated by tube amps with transformer-coupled outputs. “The input of the power amp and the output of the power amp are almost never in the same phase. A single capacitor in the signal chain will shift phase by 90 degrees” says Mr. Koh.
Another piece of critical information that Mr. Koh revealed is that the G928 is designed to exhibit low phase delay - resulting in subjectively faster bass, greater coherence between loudspeaker and the sub, and it allows the G928 to reveal rhythmic bass lines that should be a staple of any good subwoofers performance.
I tried the Genesis G928 ServoSub with a number of manufactures loudspeakers, including the Genesis 7.1p (review forthcoming) and the results were consistent and superb all across the board! Each time that I installed the G928 into the system whether I used full range or book shelf loudspeakers the integration was flawless. There was synergy, a connection within the entire system that allowed me to hear a beautifully scripted musical picture without any hint of segregation anywhere throughout the musical spectrum.
Every time that I listened to music with the G928 in my system I did not experience an overabundance of bass energy that would dominate the performance. The very easy to use controls on the back panel allowed me to make adjustments so that the lower octaves of the frequency range would not bleed up into the lower midrange and cause a congested performance. Also the use of the servo technology allowed the subwoofers drivers to keep pace with the smaller drivers of the various loudspeakers that I used and I didn’t experience any lag time that would again take away something positive from the performance. Bass notes emanated into the room and were well defined and very musical. Each note was also very well articulated with clarity and transparency.
According to the supplied instruction manual, I placed the G928 on the same plane as the loudspeakers, parallel to both, in between the right and the left speaker, but on the right hand side. This makes a lot of sense because in a jazz trio or quartet the standup bass player is generally to the right and the same can be said for bass instruments in a classical presentation.
I played a number of selections that either had a Hammond B-3 organ, the rolling thunder of the tympani, or explosive canon blasts in the recording and each time the performance was portrayed through the G928 it was spectacular. Whether the concentrated blasts from the cannon during the 1812 Overture, the deep whirling subterranean growl of the organ or the voluminous hard hit whacks on the kettle drum, the presentation was very dynamic with crisp clean notes. If called upon, the G928 can deliver powerful dynamics but one of its most compelling features is the ability to disappear similar to well-placed loudspeakers in a room. Also impressive is the G928’s ability to give the music more presence and body. On a number of recordings the music seemed to be more believable because I could feel the sonic impact from the instruments as though the musicians were playing right in my listening room. A good subwoofer should not only be herd, but also felt. This is not to be confused with loud boomy sounds that can easily be misconstrued as good bass.
The double woofer balanced design helps to maintain tight control of the diaphragm for a tuneful bass presentation. Sealed designs typically produce very tight bass because there is no port to deal with and chaffing is non-existent. Also I find that forward firing woofers offers greater control because unlike downward firing woofers the drivers do not have to directly interface with the foundation. Having excited the senses with all the throws of strong, low pitched notes, it was time for me to excite my soul so I reached back into the archives and looked for a Gospel selection. This time I went as far back as 1983 and I selected one of The Original Dreamgirls, ‘Jennifer Holliday’. Ms. Holliday originated and starred in the role of Effie in the New York Broadway production of Dreamgirls. Decades later another Jennifer, this time Jennifer Hudson reprised the role of Effie in the Hollywood blockbuster movie, Dreamgirls. To fend off a potential controversy, (especially since I’m from Chicago and so is Jennifer Hudson), I’d like to emphatically state that I do not have a favorite Jennifer, but if I did I wouldn’t tell anyway.
However, I do feel that each Jennifer is immensely talented and one of my favorite Jennifer Holliday songs can be found on the CD Feel My Soul on Geffen Records [4014-2]. This is not a Gospel album but the very last song, “This Day” is a spiritual number that reinforces the fact that the Lord is on our side. With Ms. Holliday singing about love and joy it is easy to get caught up in the romance of the moment even if it is very short. During her performance she helps to create an atmosphere of hope and spiritual prosperity. But towards the end there is an organ growl (from a synthesizer) that I can feel all the way down to my ankles. It is a moving touch that motivated me just as much as the sweet sounds of Jennifer Holliday’s voice. Listening to this delightfully refreshing song with the addition of the Genesis G928 ServoSub helped to breathe new life into the music.
At the Deep End
For a number of years Arnie Nudell had been the face of ‘Genesis’, using the foundation that he developed during his impressive career at Infinity and then later when he was at Genesis. In 2000, the old Genesis Technologies closed down, and in 2001, Genesis Advanced Technologies was founded by Mr. Koh. Mr Nudell was employed to pass along some of his innovative ideas and shared his technical expertise with company engineers until his departure in 2006. Although his legacy has been firmly implanted and recognized, there is new leadership at the company.
The new face at Genesis Advanced Technologies, Mr. Gary Leonard Koh, founder, president, and chief designer has taken the company to higher heights with new product developments. He continues to utilize proven research, including detailed measurements, feedback from extensive listening sessions and the administration of his exceptional technical and analytical skills that he acquired during his tenure within the computer industry. A testament to the success of the new brain trust behind Genesis Advanced Technologies is that the G928 subwoofer is a remarkable piece of engineering that sounds just as superb in a two channel environment as it does in a home theatre setup. When the G928 ServoSub is used in a two channel audio system the presentation is seamless from top to bottom and the integration is smooth without any noticeable aberrations. The new and improved G928 will work well with the companies own brand of loudspeakers and should also elevate the musical experience of other manufactures loudspeakers to loftier levels. It is also a piece of beauty and is so wonderfully finished that even the most hard to please craftsman should appreciate the workmanship.
With the installation of the Genesis Advanced Technologies G928 ServoSub within my system I experienced a re-emergence of enthusiastic emotions for the lowest levels of bass information that had lain dormant but has now resurfaced. The addition of the G928 ServoSub also helped with the bare essentials of the music by providing a solid foundation that resulted in a positive impact on other areas of the musical presentation including the midrange and high frequency areas. I also found my conversation with Mr. Koh about impedance mismatches and his opinion on the best way to implement the G928 ServoSub subwoofer into a two channel audio system more than just small talk. So I guess the next time that I’m engaged in a lively conversation about subwoofers with my audio purist buddies, I’m certain that I’ll have quite a few things to talk about.
Dimensions: W 17" x H 16.5" x D 15.75"
(430mm x 419mm x 400mm) (WxHxD)
Frequency Response: 20Hz to 120Hz +/- 1db
16Hz to 180Hz – 3db, +2dB
Inputs: High-level left and right;
Low-level left and right;
LFE low-level mono
Outputs: LFE low-level mono buffered
Controls: Variable low-pass filter
Variable bass gain control
Variable LFE gain control
Phase switch 0 to 180 degrees
Finish: Premium Crown Rosewood, High Gloss Piano Black,
Birds Eye Maple
Weight: 76.4 pounds
Shipping weight: 90 pounds
654 South Lucile St.
Seattle, WA. 98108
Tel: (206) 762-8383
Fax: (206) 762-8389
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