The art of compromising
A product is always a compromise as long as we have to consider the price. In the pursuit of the optimum compromise itīs easy to disregard some aspects, such as underdimension at a point where it would be a bad idea to save cost. To cut cost, It is equally important to save where it can be done without affecting the end result. This is a constant act of balance, where we benefit from the long experience.
A few examples:
In the pursuit of the optimum construction we often have to settle for a compromise.
Optimizing cost
If we build a extremely good cabinet with excellent drivers, but not the proper crossover filters, the end result will still be poor. In the pursuit of the perfect compromise itīs very easy to disregard an important parameter and save cost at a point where it may affect the end result negatively. Also, to save money itīs equally important to cut cost where it doesnīt reduce the overall quality.
Choice of filters
The choice of crossover filters is very important - even if we use the best drivers in the world we will not obtain the best sound unless we also use a properly tuned crossover filter. When constructing a filter, we quickly realize that itīs an art of compromising. The challenge is to achieve optimum results for all important parameters at the same time:
To make it easier to understand we can use these two extremes as an example:
1. A first order filter provides the best impuls response and minor phase problems, but the frequency response may be very hard to linearize. An advantage is the small number of components involved.
2. For a long time the fourt order Linkwitz-Reilly filter has been considered the best alternative. The advantage is the good frequency response and good phase performance, but the impuls response is not optimal. Another drawback is the higher cost due to more components involved.
An example of a goo
d compromise to tackle this problem would be a hybrid, where we use an active filter for the bass driver and itīs amplifier, and a passive filter for the midrange and tweeter.
An active amp offer a higher precision filtering with a steeper slope, itīs adjustable and cheap. Further, the amplifier can be connecte directly to the driver as the filtering takes place before the amp. The active filter offers adjustment options not possible with a passive filter, for instance phase, crossover frequency and level. Another advantage using an active subwoofer amp is that the main amplifier will only have to drive the midrange and tweeters, resulting in less distorsion.
This hybrid construction is used for the 99 2.2 system.
How should sound be directed?
Should the sound from a speaker be spread in all direction or strongly directed? Different "schools" have different views about this, and there are two ways of creating the "right" sound:
A. We let the speaker radiate the sound in all directions, and count on the rooms acoustic properties help even out the energy to obtain good sound everywhere in the room.
B. We direct the sound as much as possible to avoid the room affecting it too much.
The advantage of A is the wide "sweet spot", but the drawback is that every room sounds its own way and the end result becomes randomly good or bad. Sound bouncing between walls, ceiling and floor also cause lots of phase issues.
For this reason we have chosen to direct the sound from our speakers. The big advantage is that the room influence can be reduced, enabling the speakers to perform better in different rooms.
Should a center not have two midrange drivers?
Isnīt a center speaker supposed to have two midrange drivers?
We have several models using a single tweeter and midrange/bass driver instead of the more common approach with a tweeter placed between two midrange drivers. This is a compromise where both concepts have their advantages/disadvantages. Many people think that a center speaker is a special speaker with special featurs, but this is not true. Any decent regular speaker can be used as a center. The only thing that generally separates a dedicated center speaker from any other speaker is the magnetic shielding, to eliminate the risk of the speaker affecting a picture tube tv set. But as CRT sets are quickly becoming obsolete, and the new plasma / LCD displays are not sensitive to magnetic fields, there is nothing stopping you from using a regular speaker as a center.
A center speaker is usually placed lying down to better fit underneath a plasma screen for example, but from a sonic point of view a standing speaker is better. A very good solution is placing the tweeter and midrange vertically, and the woofer horisontally, but the are required becomes much larger. When the speaker is lying down with the drivers placed horisontally phase errors occur as soon as the listener is off-axis.
Using a single midrange/tweeter is the best compromise to obtain a good radiation pattern and minimum phase errors. Besides, the speaker becomes smaller. Using two bass/midrange drivers on each side of a tweeter will inevitable lead to severe phase errors for any listener not sitting straight ahead of the speaker, or off axis. Also, the cabinet volume has to be twice the size to obtain the same lower end crossover point.
This is a well known problem, and the main reason for most speakers to have the tweeter and midrange mounted vertically.
The common setup for monitor speakers is using a single midrange/tweeter. In order to tonally match this, a center speaker with two midrange drivers twice the cabinet volume will be needed. Some manufacturers compromise and make the cabinet smaller, but this results in a center speaker that doensīt cover the lowest frequencies - and they are not fully matched.
Efficiency - quality
How is the speakers efficiency related to the quality?
The efficiency equals the produced sound pressure in relation to the power. It depends on the driver efficiency, but also the crossover filter and cabinet design.
Efficiency is a very good example of the art of compromising, it cannot be too low as the speakers would need very powerful amplifiers. It itīs too high we generally experience performance problems.
Looking at the individual driver, the challenge is to maximize the efficiency without reducing other parameters such as distorsion. So, finding the best compromise between three parameters is essential: efficiency, sonic performance and cost. An example:
We can improve the efficiency by making the membrane lighter. But doing this with the wrong material would lead to a less rigid membrane - and this in turn would not sound as good due to increased distorsion. Then, we can treat the membrane to be more robust - but with increased weight as the drawback. Efficiency will decrease, and the cost will increase. There are more examples of this in every day life:
The suspension of a car is also a compromise. A soft suspension offers great ride comfort at lower speeds, but will not work perfectly at higher speeds. A harder suspension is good for higher speeds, but the ride becomes "crashy" at lower speeds.
Generally, we can come to this conclusion:
- Extremely good drivers always have limited sensitivity
- Drivers with extremely high efficiency always offer limited sonic performance