What is a Speaker?

Learn what components go into a loudspeaker and the difference between 2 and 3 way designs

Hi there, John Hunter with REL here, we’re answering really basic questions that come up fairly frequently when we have new customers reaching out to us through email. The first one is very simple, what constitutes a loudspeaker? And it seems so obvious to people who’ve been doing this for years and years, but it’s worth explaining to people and particularly why the different parts of a loudspeaker look so different.


I’ve got one right here. This is a really wonderful little inexpensive speaker from our friends at project over in Austria. I think literally they are $300 to $400 a pair. They’re a huge bargain and the first thing that will strike you is this is a two way named after the two different drivers. The upper one is called a tweeter, and that thing is responsible for reproducing the high frequencies.  This is really sort of a general do all.


More advanced speakers might have three speakers, a much larger woofer to handle the bass. This is more of a conventional mid-range size driver, but as you’ll hear if you ever get a chance to listen to these it goes down pretty good into the bass. Well, to give you a range of the wavelengths that are involved with that. The size of the wave, a high frequency of 20,000 cycles is only about three quarters of an inch long. If you’re on the metric system, that’s 17 millimeters. Whereas the lowest bass note that we traditionally shoot for is 20 Hertz.


And at 20 Hertz, you’re talking about a wavelength that’s something on the order of 58, 60 feet long. So three quarters of an inch to about 60 feet, 17 millimeters to 17 meters. So in order to handle all of that huge change in length of frequency you need different kinds of drivers that are optimized for it. So again, tweeter, high frequencies, and generally speaking, the larger the driver, the deeper it will go.


A good way to think of a mid range is our voices are mid range. Human beings are incredibly attuned to mid range frequencies. It has everything to do with communication. It has to do with survival instincts. Can you hear somebody say something that makes you go left or right, and avoid a train for example? So we’re really highly attuned to this and a simple way that a mentor taught me a long time ago, was it should be a little larger than your mouth at full extension.


And it gives you an idea of why that would be. So, the final element in there, speaker is something that’s not seen. It’s inside the cabinet. Typically it’s incredibly important. It’s called a crossover and the crossover is really responsible for things that make intuitive sense the moment you think about it.

If you were to try and take a tweeter or a high frequency driver that only can go down to on a very good day, maybe 700 Hertz you need something to eliminate the bass in mid range frequencies from coming through and destroying the tweeter.


So, we use a very simple component called a capacitor. Now capacitor quality vary enormously. You can buy perfectly credible capacitors in large quantities as a manufacturer for something on the order of 30 or 40 cents apiece. You can also get hand-built ones made in Germany that will cost you 700, $800 at retail. So it gets a little bit mysterious, but fundamentally what a capacitor’s function is to prevent low-frequency from getting into a speaker driver that can only make a certain limited range of higher frequencies.


Conversely, you need a coil and it’s literally what it sounds like. It’s a wire that is spun around a core choke and the wire has to be coated with something called Litz coating in order to prevent it from bleeding through, so it actually turns it into a coil. And what that does is it suppresses the higher frequencies from getting down into like a woofer.


So, coil limits the highs while the capacitor limits the lows and when you have a mid range driver, you sort of need both, right? You need something to roll off the high frequencies, that’s the coil, and you need something to block the lowest frequencies from getting through because that mid-range driver can only move so far and that’s what expresses bass. So, you have to have two circuits in there, and then there are a whole different range of variations. Once you start throwing resistors into that and tuning things around this and that. And you have coils and caps and certain applications to highlight certain things.


But, but the bottom line is you need a network to separate those things out so each driver runs in its sweet spot.

June 29, 2021 - Posted in: Q & A With John Hunter