This gives maximum control over the mechanical motion of each driver and most efficient use of amplifier power. Amplifier power has to be wasted in the process. The power amplifiers of an active loudspeaker system see a benign load resistive, slightly inductive over their assigned frequency range, unless it includes the mechanical resonance of the driver highly capacitive and inductive.
The single and much larger power amplifier that is required for a passive crossover loudspeaker has to drive a complex load, which places more stringent requirements on its dynamic stability and overall performance.
Different amplifiers may sound different. Open baffle loudspeakers Open baffle speakers are inefficient in terms of the mechanical movement that is required to create a given level of sound. This not only applies to speaker cones but also to panel vibrations. Open baffle loudspeakers reproduce bass with less room interaction. It is more articulate than from box speakers. If dipole behavior covers the full frequency range, then the room response becomes perceptually masked by the direct sound.
An open baffle circumvents the box problems of delayed radiation through cone and enclosure panels. They occur typically in the mid-frequency range and are difficult to suppress. Large panel radiators or long line radiators suffer from severe lobing at higher frequencies. It manifests in critical room and listener placement. Amplifier power could be an issue as frequency increases, where it requires higher cone acceleration to reach Xmax.
Thus SPL is limited by driver volume displacement at the very lowest frequencies and becomes amplifier limited as frequency increases. Realistic bass levels can be obtained from dynamic drivers in open baffles, not from panels. For extreme SPL requirements the number of drivers could get very large and, therefore, below 50 Hz they are more economically replaced by sealed box subwoofers.
At frequencies where a 8" driver would become directional it has wider frontal dispersion for an open baffle than if the baffle were closed in the back. Open baffle speakers reach deeper into the room and are less subject to the room response if their polar response is well behaved.
ORION exemplifies open baffle loudspeaker design in terms of polar response control and dynamic range. It circumvents the limitations of large panel radiators and yields a small package. The low masses of the moving parts in an ESL, a planar magnetic, or a ribbon driver are necessary to generate useful sound pressure levels. The force generated by an electrostatic or planar magnetic motor is weak.
Since SPL is proportional to air volume acceleration, and moving parts Acceleration is Force divided by Mass, the mass has to be lower if the force is too weak to generate sufficient acceleration. Furthermore, since excursion is limited with these drivers the radiating area has to be large to move a sufficient air volume.. These relationships seem to be difficult to grasp by audiophiles. It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker.
Box loudspeakers Small boxes have fewer problems with panel resonances, cone re-radiation, and polar response than large boxes. Box panels can radiate more sound at certain frequencies than coming from the cone. The sound behind the driver cone should not come back out through the cone. Typical box speakers have a generic sound due to their polar response, panel resonances, re-radiation through the cone and vented bass.
Bass from box speakers has more "punch" than from open baffle speakers, but is less airy. Vented bass speakers are resonant structures and store energy which is released over time. For accuracy, bass must be reproduced from sealed or open baffle speakers that are non-resonant. Closed box speakers are best listened to from very close distance to minimize masking from an uneven room response. PLUTO is not merely another 2-way box speaker. Secondary radiation from enclosure panels and through the driver membrane from inside of the enclosure were eliminated.
Being an active speaker, two drivers of very different sensitivities could be combined in order to obtain omni-directional radiation. Bass response was extended by equalization and not by a resonant vent.
Listening rooms The room is rarely at fault. If it is comfortable for conversation and living in it, then it is also suited for sound reproduction.
The problem is usually the inadequate polar response of the loudspeakers and their placement in the room. Loudspeakers should be positioned out in the room, at least 3' 1 m away from reflecting surfaces. The further the better. Speaker placement to the inch based on some room acoustic calculation is nonsense.
When you want to listen loud, you can benefit from the driver mount on the board if your room or stage is large enough to accommodate the frequency generation. Although you can find several potential benefits with an open baffle design, the speaker specs set the good choices apart from the bad ones. An open baffle speaker design creates a unique visual for your space. When you need to add this asset to your listening experience, the Klipsch Reference RSW delivers an impressive result.
This w powered subwoofer is rated as an outdoor speaker, ensuring that you get the quality you need for the open baffle inclusion. It uses a inch, copper spun sub with a front-firing design to ensure the bass frequencies deliver the vibrations you want.
When you install open baffle speakers in your room, the drivers could be at risk for some forms of damage more than a sealed box design would be.
If you have pets or small children living with you, this design could require careful mounting or placement to keep everyone safe. A simple grill can keep away curious fingers or paws that want to touch it. It helps to keep your purchase receipts for about 36 months on high-end equipment to ensure you get as much of the replacement value as possible if something happens. The baffle design is not typically well-suited to the average home.
Your decision starts when you set a budget that you can afford. Are Open Baffle Speakers Bad? Instead of having a smooth response, the charting would look more like a month stock tracker.
Open Baffle Speakers vs. Sealed Closed Box Speakers When you look at the two mounting options that most people use for their drivers today, it is either a sealed box or the open baffle design.
A smaller box has fewer issues with cone re-radiation, polar response, and panel resonances. When the dipole behavior can cover the entire frequency range, the room response becomes perceptually masked due to the direct audio. Box panels will radiate additional audio at specific frequencies than when they come from the cone alone. It prevents the sound that originates from behind the driver from coming back through the cone. Dipole open baffle speakers require a six-decibel boost toward the lower frequencies to drive the maximum excursion and EQ.
Since amplified power could be an issue as the rates come higher, cone acceleration must be a considered feature. Bass frequencies from box speakers tend to have more punch than they do from the open baffle design, but it is also less airy. An open baffle speaker is typically more inefficient than a sealed box when evaluating mechanical movement, including measurements taking at the panel for vibrations.
Any venting from the box can impact the resonant structures employed, creating inaccurate reproductions of the audio waves getting sent through the loudspeaker. The installation and maintenance for the open baffle option are the easiest to manage when installing loudspeakers with your system.
Most listeners find that the best results with this design come from close-distance listening as it minimizes the masking that happens from uneven room responses. What we try to avoid is having the exact same distance to these edges so as to average out these roll off frequencies. The worst offender for having exactly the same distances would of course be a circle. This is the theory and I am sure that their exists mathematical formula that confirms that this is true.
We have not however, received sufficient anecdotal, real world evidence of this to say for certain that it's a real big consideration when using our Silver Iris drivers. Most of our builders myself included center our drivers on the baffle and achieve excellent performance.
On the other hand it would seem unlikely to cause any performance reductions if done so. I would label this as an optional technique that should not cause any degradation of performance. The distance to the top of the baffle and also the shape of the baffle top, does seem to have a greater potential for effecting the final sound. This is a bit more involved with the soundstage illusion and will be covered more in the next section.
For now I would say that it is generally considered prudent for this distance to not be our shortest. If the shortest distance to an edge is this top dimension, some suggest that the sound will interact in this area first and have ill effects on soundstage. We also have seen good results from making these top sections domed or sloped. Conversely we have countless examples that have perfectly flat tops who's builders are very pleased with their end results.
Have fun with this and share you discoveries. Section 3 Advanced Ideas and concepts in Open Baffle speaker construction. Now that we have a working foundation of information on how to build our OB's, we may now explore ways of making them even better.
One popular way of making our baffles perform better is through the further reduction or elimination of distortions or coloration's. Whenever an object is set into motion it is plausible that this moving object can in fact create sound waves and be heard by the listener. This secondary sound is undesirable and advanced speaker builders strive to gain control and hopefully eliminate all traces of it from their playback systems.
Improvements are usually described as our music becoming less congested, cleaner, less colored or having lower overall distortion. This, by the way is one of the primary reasons so many of us prefer our OB's in the first place.
By eliminating our boxes we eliminate the potential for the coloration caused by the stored and released energy from the materials used to construct these boxes. When looking at our OB speakers then, the last remnant of our former boxes is this front baffle. It would seem only natural that we finally focus on this one remaining surface with the same critical eye we did the other surfaces of this former prison. In this section we shall look into vibration management as a design tool for greater clarity.
We will revisit our drivers themselves and look at damping the frames and basket assemblies. Once we have a good understanding of this mechanical tool called a speaker, we can also look at this tools presence within our rooms and soundstage. In this section we will look at the reflective or refractive properties of our baffles and discuss the improvement potential of surface treatments.
Not too unlike the sound boards and resonate chambers found in many acoustic instruments, our baffles have the same potential to be excited by the piston action of our dynamic drivers.
How much sound our baffles can create varies with their construction and material selections as well as how much energy the drivers themselves are being asked to displace. Along with how loud we are asking them to play is also the consideration for how low in frequency we are trying to recreate. We will see that vibration management becomes much more of a consideration as we increase volume or when we include into our designs, bass augmentation.
The first tool in the tweakers tool box that is useful for vibration management is decoupling. Not unlike the motor mounts in our vehicles we can decouple our drivers from our baffles and thus limit the transfer of energy from the drivers to the baffles.
When building our production finished speakers we mount our drivers first to a plywood mounting plate. This plate is This seems to do a great job of arresting any ringing of the outer driver flange and stiffens everything up nicely. Very Rigid once mounted to these mounting plates.
We then insert a thick, foam rubber gasket between these mounting plates and the back side of the baffle proper. We then bolt these plates to the baffle with this gasket serving to decouple the two pieces of wood. This does a good job of limiting the direct transfer of vibrations from the driver to the baffle. Another approach to this which is rapidly gaining in popularity is to create a constrained layer baffle using visco-elastics damping products such as 'Green Glue'.
By utilizing multiple layered baffles with this Green Glue in between these layers, significant reduction in vibration is possible. Perhaps the most interesting approach to this challenge of limiting transfer of energy from the driver to the baffles is to simply not use the baffle to mount the driver to, thus eliminating any direct contact.
This is accomplished by mounting the driver by some part other than the outer rim. One common method is mounting the driver by it's motor assemble or what has been called "Magnet mounting". By using some other part of the driver to mount to, we are now free to use a much wider variety of baffle construction materials.
We can make the opening of the baffle such that the driver simply fires through this hole but makes no physical contact with any part of this baffle. When constructed such as was just described we could call this new baffle a "Facade" to differentiate it's function from that of a structural baffle. This facade may now be made from very light weight material and no longer needs high mass to help damp vibrations.
This facade idea is slowly growing and we will soon see many study builds with this as a main feature. The ability to easily and very quickly change facades is seen as a major advantage over a structural baffle.
Trial and study can happen very quickly as could also simply changing facades at will for visual interest or possibly for fine tuning for a performance change. One obvious swap would be when shifting from 2 channel music to multi channel Home theater use. We could instantly alter our tonal balance and soundstaging signature with a simple swap of a couple alternate facades.
Vibration management extends to the driver assembly as well as the baffle. In fact everything that comprises our speakers should be viewed with a critical eye towards controlling the byproducts vibrations from the creation of our music. This would include any base or plinth we may want to use. It could also be a consideration when we look towards mounting the filter network 's or any on board electronics. The stamped frame of the Performance Grade 15 "Silver Iris Coaxial is made from heavy gauge metal and is shaped such that it is quite rigid and stiff.
This alone however does not guaranty that it will not ring, sympathetically vibrate or reflect energy. Many advanced builders are looking at these surfaces and asking the logical question. The basic idea here is to add "soft mass" Soft Mass is something that lowers the resonant frequency through mass loading and yet stays soft and flexible. Modeling clays, duct seals, rope caulk and automotive damping sheet goods head up this list of products that damp well, and are readily available, inexpensive and removable.
Many builders are also covering surfaces such as these with felt in an attempt at eliminating reflective surfaces. We like to cover the back side of our baffles with felt to help eliminate the possibility of these surfaces being the sources for these secondary reflections.
Some of you may now be asking the logical question, "Does all of this truly matter? I also think that if viewed collectively, that when all of these measures have been incorporated that yes, they do offer real gains in performance. One way to permanently reduce basket vibration issues is to upgrade to a cast frame design and this is exactly what we have done on our augmentation bass driver and the New Sterling Grade series of drivers. These heavy cast frames are the definition of rigid and are quite massive.
They could still benefit from covering in some non reflective material. Adding mass does not really remove vibrations but shifts the vibration to a lower resonant frequency. The basic idea here being that a heavy object needs greater external force to cause it to move. If insufficient external force is provided the material in question will not move significantly enough to possibly produce any secondary sound. This holds up well until we come along and supply it with enough external force to actually excite it into motion.
This can happen from the creation of low bass information at higher volumes. One way of adding mass that also does essentially eliminate vibration is the use of sand or metal shot. While strictly speaking sand cannot eliminate the energy content of vibration it can convert this to another form of energy called heat.
That's right. Some savvy builders are using sand to damp their baffles and especially the base or plinth that the speakers rest on. Draw backs to any of these mass loading ideas is the additional weight and additional effort required to reposition your speakers. For many the end result is worth the added inconvenience when it come time to move them.
One last topic we should mention here is the mounting of the passive filter networks. The Silver Iris Coaxial units passive filter networks are mounted to a block of solid Mahogany. Between the components and this wooden block is percent Silicon adhesive which both holds them securely and also is intended to act as a decoupling medium.
Locating them as far from vibration sources as practical is always prudent. Some builders go an additional measure and further shock mount their crossovers. Double sided foam tape under them may prove sufficient. Building an isolation platform using sand and or air bladders has also been suggested. Bass extension, bass weight, bass authority bass slam, boom, crunch and bass articulation. Seems we are not at a loss for terms when it comes to our beloved low frequencies.
To many people, bass energy is the heart of any music system. That driving beat that everything rides on. Open Baffle speakers have been notoriously bass shy and until recently never thought of as being very desirable if powerful low end response was on ones wish list. Fortunately this is no longer the case. In fact powerful OB bass can be easily achieved and when done well is truly spectacular. Lack of enclosures and this dipole radiation pattern results in a very natural sound. Acoustic bass instruments radiate energy in a very similar pattern to that of our OB speakers.
OB speakers fill our listening environments with direct and reflected sounds that have scale and ambiance clues that helps us imagine what size venue the original acoustic event originated from.
Controlling all this energy potential should be high on the wish list of the advanced speaker builder. Everything that was mentioned in the previous section with regard vibration management need be ramped up and looked at with even greater attention to details. What could have passed unnoticed before will be glaringly obvious once we introduce these powerful low frequencies.
Rattles that were never previously activated, now demand our full attention. Good mechanical practices here such as securely bolting everything down will go a long way towards ensuring success. Physical isolation of the Augmentation drivers may prove wise and mounting then to a separate baffle near ideal.
In our Duet style speakers that contain our full range coaxial and our Augmentation driver Augie , we like to use two separate mounting plates, spaced well apart and decoupled from the main baffle and each other. This is done in hopes of reducing or eliminating any "cross contamination" that may come from mounting an Augie to the same speaker system that contains our full range coaxial.
This Duet mounting style is very desirable for several good reasons but does expose the builder to the possible problems that come along with this pairing. We have many Duets, made by many different builders, all reporting very high performance.
This should go a long ways towards instilling confidence that you too will succeed. Soundstage And Soundscape When someone mentions these words in the context of home audio they are generally talking about an illusion that is presented before us if certain conditions are sufficiently met.
Soundstage, then is simply the illusion of a stage with performer 's occupying space within or on this imaginary setting. It may be a real stage inside a studio, club, theater, performance hall, etc. When seated in front of this illusion we can often perceive imagine Height, width, depth and distance to surrounding walls ambiance clues.
We may possibly even imagine the exact location of each performer relative each other and this illusion can be very convincing under the right conditions.
This is what is being sought so intently by so many music lovers. We want to feel like we are sharing a space with the performers. Some audiophiles focus their system on creating the illusion that while listening they are magically transported to the exact location that the original performance was originated from. This is the landscape of our rooms both in front, to the sides and also to the rear of the listener.
While it is perhaps easier to "surround" ourselves with sounds and paint a 3D soundscape with multiple speakers, it is also possible to experience a full soundscape using just the two front speakers.
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