John Jefferis our Founder talks about his life’s journey to achieving the ultimate in bass augmentation and why MJ subwoofers are uniquely able to provide the audiophile integration that eludes our competitors.
Throughout my life, especially as a small boy, I always imagined it is possible to wake up one morning with an idea and for that idea to be original. I remember spending many hours at my boarding school playing snooker listening to an old Fidelity Music Centre record player that sounded thin and sharp. Even turning up the bass control could not make it sound any more improved. This was in the early eighties and the thought of a speaker just to make bass was not even considered in my head so therefore didn’t exist…Ha Ha. Using a 12v car boost amplifier and with passive components to filter out high frequencies I cobbled together a device that managed to enhance the bass for my listening pleasure. I never knew that later in my life this rather Heath Robinson approach would, in reality, mark the beginning of a lifelong obsession with music. My first car had such a device installed in the back using an old Eagle 6×9 bass speaker, passive crossover with attenuation, coupled to the booster-amplifier. More often than not when you think you have an original idea you find out someone else has already made one or is selling it and your original idea was not so original after all. The very basic active subwoofer assembled in my youth at school is such an example for there were Subwoofers available to buy. However none that fulfilled my “ears vision” so to speak.
These days, everybody considers turntables, apart from being old technology, are the same – they only need to go round at the correct speed to make the sound, don’t they? almost True, but that doesn’t stop them sounding different. Then there are those who think all good amplifiers sound the same, until you actually listen carefully. How about the dawning of the digital era with the Compact Disc. After all “perfect sound forever” cannot be improved upon can it? We all know the answer to that. let us not forget speaker stands, interconnects, mains leads etc.,
Everybody “considers” all subwoofers sound dreadful, don’t they? Do they? Well, there is one Company which would disagree vehemently with that. MJ Acoustics has spent over 20 years and much financial investment investigating the technologies that make our subwoofers not only different but uniquely able to match and enhance any HiFi system without upsetting the main system sound quality. To ensure this in a High-End 2 channel system, the solution is to connect the subwoofer input from the power amp. Additionally, the subwoofer needs to be active and to have its own independent and variable crossover filtering totally separate from the main system. By use of this variable crossover, the subwoofer is then brought up sonically beneath the main speakers. This variable crossover filter is unique to MJ. We call it the DAMP 3rd Gen Active Bass Crossover. Its action is limited to the subwoofer alone. As it is an active circuit with its own buffered high impedance input, it can be connected to the amplifier’s speaker outputs without having any effect on the amp whatsoever. The DAMP 3rd Gen Active Bass Crossover output is presented to a power amplifier and bass speaker, all of which is also integrated into the subwoofer enclosure ensuring total system compatibility. This power amp is optimised for the subwoofers bass driver. The DAMP 3rd Gen Active Bass Crossover has fine filter controls allowing critical and calibrated adjustment together with gain controls to match volume with the main speakers. There are other benefits to this line of approach. The main one is detailed below regarding its ability to work in any sized room with virtually any speakers system. Another advantage is imaging of the main system is preserved down to its finite limits. A surprising bonus is that when correctly matched in, imaging and depth appear to improve. Quite why this should be is open to debate. It is most obvious with high quality very revealing systems with good recordings.
Essentially the subwoofer is a true sub-bass speaker integrating fully into the existing system. It is wired in parallel with the main speakers instead of in series – there is no compromising passive crossover muddying up the midrange.
Unless you play your music in a field, everything you hear from your system is modified by your listening room. The system interacts with your room. All sounds are affected. This can be beneficial as the room provides ambience which helps us enjoy the musical experience. Unfortunately, it can also ruin the sound, particularly in the bass. The actual range of frequencies affected is a function of your room’s dimensions. The reason for this is because the wavelengths involved at low frequencies are of the same order as your room’s size. Standing waves are set up which will affect these low frequencies. The larger your room, the lower the frequencies affected and the larger the speaker you can use in your room before “room boom” becomes a problem. Conversely, the smaller your listening room, the higher the frequency range that is affected. This puts a limit on the low frequency extension of your speakers. If you ignore this effect and install a pair of speakers with a prolific and extensive bass output in too small a room, you will end up with “room boom”. Your room is effectively boosting your speakers already strong bass output. The effect can vary from a gentle boom where only marginally larger speakers than optimum are used, to a full-blown, thick and heavy bass boom sound which colours every recording played. This will completely ruin the sound, masking fine detail and generally destroying the musical coherence of the piece being played. Even in moderate quantities, “room boom” can be very fatiguing.
Many enthusiasts effectively solve the problem by using a smaller speaker which does not provoke any boom. An example being Bower & Wilkins 805 stand mount speakers. The consequence of this is no deep bass. Hardly a satisfactory answer, but the only one available in the absence of an audiophile designed subwoofer.
The DAMP 3rd Gen Active Bass Crossover.
Essentially, by using the simple to adjust but highly accurate filter controls on the crossover, the subwoofer is brought up sonically beneath your main speakers to the point where their acoustic output is falling away. This will vary from speaker to speaker and room to room. Even the same speakers, when used in different rooms, will have differences in their bass extension. The only condition that must be observed for the system to function correctly, is that your existing speakers do not themselves cause “room boom”, i.e. they are not too big for your listening room. Neither must they be too “thin” sounding, or you may end up with a “hole” in the response.
The DAMP 3rd Gen Active Bass Crossover has a gain control which adjusts to compensate for the lack of boost given to these very low frequencies by your room. This ensures a smooth blending of sound from the two sources. With this system, you will be able to hear (and feel) very deep bass.
Until more recently most subwoofer manufacturers have assumed that there must be a crossover in the circuit somewhere, either between the power amp and speakers or between the preamp and power amp. Typically this crossover will be at a frequency somewhere between 80 and 150 Hertz. It will transfer the bass signals from your existing main speakers to the subwoofer. Quite apart from the questionable practice of inserting extra components in the signal path with all the inherent disadvantages this brings, there is the even more important question of room and system matching. It is very risky to assume a flat frequency response from main speakers to the subwoofer will suit every room. The chances are very high that it will not match. If your existing speakers were chosen for their pleasant bass in your room, you would be most unwise to then throw that away for a mono bass from another source which might very well boom and ruin your carefully chosen system sound. MJ recognizes the importance of room matching. We go to extraordinary lengths to ensure optimum room/system matching between your existing system and our subwoofers. They are there to supplement your main system, not to overwhelm it. We build our bass engines to function down to well below audibility. We deliberately engineer them for maximum extension and transient response. With increasing price, you get improved power handling, resolution, transient performance and extension.
Most audiophiles perception of a subwoofer is a cheap and cheerful “boom box”. For this reason, many audiophiles either bite the bullet and install a pair of very large floor standing speakers or put up with reduced low-frequency extension. Unless the room is very large there is likely to be a problem with large speakers somewhere in the bass region; another reason for many audiophiles preference for smaller speakers. They would quite rightly prefer quality before quantity. Fortunately, there is a much more domestically acceptable alternative. This is to pass only the very low bass to a separate speaker, the subwoofer and to leave the existing speakers entirely alone. The big advantage is only a single unit is needed for these exceptionally low frequencies meaning a big cost saving, or put the other way round, a far superior bass performance for the same outlay. Provided this subwoofer has a dedicated internal crossover that allows it to match into the system together with its own bass power amp, excellent results can be obtained. Far and away better than using a fixed crossover filter with all its associated problems. When setting up correctly, excellent integration with the main system is assured. Because the subwoofer is only coming in beneath your main system speakers it will have no effect on the main speakers at all. So far as MJ is concerned we are the only manufacturer to integrate a quality subwoofer truly successfully into quality systems. In fact, many customers comment after living with the system for a while, that they wonder how they had put up with their system’s earlier lacklustre performance.
True subwoofers for the audiophile, When it’s right it just sounds real!.
MJ subwoofers are designed to be connected to the existing power amp’s speaker terminals. They are in effect bi-wired with the main speaker cabling. Thus there is no interference or possible corruption of the main stereo signal going to the speakers.
This is quite deliberate. The speaker signal from the power amp is the most robust signal in the reproduction chain between source and speakers. To prove this consider: the power amp is designed to supply power to the speakers. These may be of quite low impedance, just a few Ohms. The subwoofer draws virtually zero current from the power amp because it is a very high impedance load (technically we say it is voltage potential monitoring). Now contrast this with the signal at the source, for example, a low output moving coil cartridge. Its output is literally a few millionths of a volt! This signal is notoriously difficult to amplify without distorting it, however subtly. A whole market in high-end preamps has developed to satisfy the extremes required by these cartridges. Any corruption (distortion) is irrevocable, it cannot be removed. It will simply be amplified by the subsequent stages. Likewise the signal between the preamp and the power amp. At MJ we believe any parallel connection to the precious signal cable can only harm the signal. This is pretty extreme but is a pre-requisite for decent audiophile standards. With a separate outlet on the preamp, provided it is separately buffered (only offered on top end equipment) then the results can be considered the same. This brings us back full circle to why we recommend the only correct way to add a subwoofer is by bi-wiring from the main power amp. Any other method is a compromise. Compromises do not come easily to an audiophile.
All modern speakers have been designed with the assumption that they are full range speakers. Of course, there will be a roll-off in the lower bass, depending on the model and the room it is being used in. But none require any help in handling the full range signal sent to it by the power amp. Any attempt to tamper with this signal by means of passive or active crossovers runs the severe risk of harming this signal, however cleverly the circuit is designed.
Obviously, the input circuit to the MJ subwoofer is specifically designed to handle very powerful signals. No harm can come to the subwoofer whatever the power of the main amp, even a kilowatt can be accommodated with ease!
Of course, having taken all this trouble to ensure isolation from the main signal after connecting a subwoofer, it would be absurd not to take the same care over the design of the subwoofer itself. We have. Every MJ subwoofer from our least expensive to our dearest has had the same lavish care taken over its sound quality. No booming bass. Just accuracy, extension and musical involvement.
Most people will concede that a wide system bandwidth is not just beneficial, but essential to anyone aspiring to true high-quality musical reproduction in the home. With a conventional big box speaker not only is room matching a hit and miss affair, but your amplifier will become a limiting factor. The more critical the speakers, the more need for a very high-end amp. Remember the speaker is the slave of the amplifier. It can do no more than its told to do and frequently will try and do much less. With the MJ subwoofer, there is no need to worry about upgrading your amp. The MJ has its own built-in power amp which has been optimised for bass. It is DC coupled, meaning there are no harmful capacitors in the signal path causing phase problems and limiting its ultimate low frequency performance. Because of this built-in amp, there is no power drain on your main stereo amp. It goes on happily driving your main speakers exactly as before. The MJ takes care of the bass and ensures by means of its clever internal Active Bass Crossover that it fits perfectly beneath your main speakers. It can be “tuned” to your system and room, whatever your system’s capabilities and listening room size. This is of enormous benefit, particularly if like many others, your listening room is not perfect. The MJ will pressure drive your listening room below its lowest eigentone …….
“Meaning of Eigentone”
“In rectangular rooms, the frequency amplified is that with a wavelength twice that of the distance between the parallel surfaces and is called the room’s Eigentone.
When a frequency matching this Eigentone is sounded in the room a standing wave occurs where the sound wave and its reflection are in phase with each other and reinforce each other.”
…….and ensure that those previously missing or masked frequencies are heard cleanly and clearly, no false emphasis or boom – you control its sound in your system.
Another benefit is realized more long term. If you decide to upgrade any item in your system, the MJ will simply blossom more and more. In other words, it will grow with your system, never becoming dated. This, of course, can be said about some upmarket speakers, but unlike those very revealing ones that simply show up your systems faults, the MJ is fully adjustable, thus it will never be obtrusive.
A further benefit is more domestic. It can be positioned where you want and not restricted to a single “hot spot” as would be the case with a pair of very large speakers. Because of its harmonious styling, particularly true of Reference and Master-Class, it can be of practical use as a sleek coffee table, lamp or ornament stand.
Perhaps its biggest benefit is it allows you to keep what is best about your existing system. It is very likely that you spent a lot of thought, time and trouble choosing your main speakers, so why risk spoiling the sound they produce by compromising with a conventional subwoofer? With an MJ there is NO compromise. The MJ will only add to your already high-quality sound. It will never overwhelm but confidently underpin your main system. It is very likely the most cost-effective upgrade you will ever make. This has been repeated back by countless customers testimonials over the years, time and time again.
Every single subwoofer we make has been individually and very carefully tested, checked and tested over and over at each stage of its production. Not a cheap way to build, but the only way to ensure consistently high quality.
Believe me when I say that purchasing an MJ Acoustics Subwoofer is the single most important addition to any audio system. You have my word on that.
Organise an audition with your dealer to hear the missing link in your system.
Founder, Designer & CEO
100% British Audio at it best