How to identify good speakers?

Many a word has been spoken on the topic of speakers. They are probably the most ‘in your face’ aspect of an audiovisual set-up and prices can range from plain cheap to astronomical price tags. Apart from reading reviews and deciphering specs, what actually makes a good speaker? The obvious thing to look at is the loudspeaker driver. We’re talking woofers, tweeters, midranges and the likes.

But let us first define what a loudspeaker driver is and what its primary role is.  A loudspeaker driver is an electromechanical device that converts electrical waves into mechanical vibrations which in turn produces audible sound waves.

While some manufacturers claim they make their own drivers, that is not necessarily a good or a bad thing. While you basically want a good quality component, it can be a very effective way of cost-cutting in the manufacturing process to use an off-the-shelf driver assuming it is a good one. Why reinvent the wheel when you already have a well designed product available? On the other hand, sometimes that good product is not available yet, which completely justifies the company’s need to develop one themselves. So first off, don’t let yourself be fooled by claims that a company has developed their own driver. That actually tells you not much.

A very important part of a driver is the cone (or dome or diaphragm). The cone isthe actual physical surface area of the driver that moves up and down. This produces sound by compressing and thinning air, creating sound waves.

The size of the cone will determine the bandwidth in which the loudspeaker will be most efficient at reproducing sound.  A bass driver is designed to reproduce low frequencies (20-500Hz), a midrange driver covers the midranges (100Hz to 4kHz) and a tweeter is designed to be most efficient at reproducing high frequencies (1kHz to 20kHz).

You will notice that the different drivers have their own ‘specialty frequency range’ but also overlap to a certain extend. This brings us to the topic of crossover network. The loudspeaker crossover can be considered the brain of the loudspeaker; it is the director.  Amongst a few other things, it directs the bandwidth of frequencies each driver is optimized to reproduce. Without the loudspeaker crossover, a loudspeaker driver such as a tweeter can be overdriven which can lead to distortion and eventual failure.  A loudspeaker system without a properly designed crossover can cause too much frequency overlap between drivers which can increase distortion and degrade overall sound quality.

The “how” of speaker crossover gets rather technical (think resistors, inductors, and capacitors and the likes), so we’ll keep it pretty basic.  Separate filters (HPF and LPF filters) limit frequencies below or above where the driver is inefficient at producing those frequencies.

Think of a tweeter trying to produce bass frequencies.  It can’t do so efficiently so we employ a HPF to block those frequencies.  Conversely think of a woofer trying to produce very high frequencies.  Manufacturers employ an LPF to effectively filter the frequencies above which the woofer is capable of producing.

In the real world, the resistors, inductors and capacitors are far from prefect and this whole crossover network designer world is rather complicated. Small differences in design choices or shortcuts have massive impact in quality and performance of the speaker.

It is safe to say that properly designing a loudspeaker crossover requires engineering talent and sufficient budgeting to fit it into the total system cost.

And then there is the driver basket. The driver basket end is the physical structure that holds the entire driver together. Loudspeaker driver baskets are typically constructed either of stamped steel, plastic or cast aluminum.

Plastic baskets are generally used solely for cost savings over cast, or heavy gauge stamped frames.  They are fine for smaller driver applications but are usually not used for larger and heavier bass drivers where greater durability and rigidity is needed.  Though there are exceptions (A plastic basket with glass fiber can provide better acoustics than both stamped and cast aluminium for example).

Aluminum in its nature is entirely non-magnetic, while steel carries magnetic lines of force with ease. This can create a parasitic flow of magnetic lines of force, which good designers know to tackle with a non-magnetic spacer.

Stamped steel baskets are less costly to produce than cast aluminum baskets and definitely have some disadvantages like strength, cooling, etc. That said, respectably good performance can still be achieved with stamped steel frames.

If you are after the very best loudspeaker designs on the market however, look for a design that takes advantage of the properties of aluminum cast baskets and uses them in all of their drivers.

So how do you know whether the speakers you have your eye on tick the box in the driver department? When magazines or audiophile websites write speaker reviews they do a lot of measuring and take the speakers apart to have a look at its bowels.

For obvious reasons that is not something you can do when you consider the purchase of a speaker. Reading and comparing specs is definitely a good thing to do, but it is also good to be aware that companies are not always as honest as you would expect them to be.

The most important thing you can do is to listen to your speaker in peace and quiet, preferably in your own home or a well set-up demo room and using tracks you are familiar with. Take your time to do this properly.

Choose tracks that are representative of the sort of thing you listen to, but at the same time make sure it covers the whole range of frequencies so you can check the crossover is to your liking. It is good to remember that listening to a jazz track is an entirely different experience compared to listening to the explosions in an action movie. You need the best speakers for your personal requirements.

Talk to your dealer, ask questions about the drivers and the crossover. If they know their stuff they should be able to answer them.

And our last bit of advise: crank it up. You want to make sure the speakers are capable of handling the volume you desire.

In the meantime, give us a ring or send us an email if you need help or advice with your audiovisual and home theatre set-up. We love to work with you towards the best possible solution.

The Rapallo Team