Speakers part 2: let's get technical

Speakers part 2: let's get technical

By Angus .

Speakers part 2: let's get technical

 Welcome to part 2 of our extensive blog on speakers. We covered off some pre-purchase considerations and laid the groundwork for great listening at home in part 1. 

Now we're going to bury our grey matter a little deeper into the nitty gritty of speaker technology and how they actually work, as well as a few more tips on how to tweak your sound a little further.

 

Two way v three way

There’s a generally accepted piece of conventional wisdom in speaker design; three-way is better than two-way.

Whilst this is true to a point, it’s not universally correct. Let’s take a look at how the designs differ, and some potential advantages and drawbacks.

The difference between the two designs has nothing to do with the number of drivers in a cabinet, but rather how many different driver types it has. In a two-way design, there’s two drivers to cover the entire frequency range, with a crossover point set by the manufacturer.

This is the frequency at which the tweeter (smaller driver, usually at the top of the assembly) takes over reproducing sounds from the mid/bass driver (the big one).

In a three-way design, the frequencies are split between three different driver types, with one each handling low, mid and higher frequencies. The obvious advantage of a three-way design is that you’ll hear a clearer, more open midrange because those frequencies have a dedicated driver.

Three-way on the left, two-way on the right. Note that whilst the two-way speakers have three drivers, there’s only two different sizes; a tweeter and a mid/bass driver.

Despite the obvious advantage of a three-way configuration, there’s an angle to this that bears scrutiny. If you’re on a restricted budget then it may be that two-way is your best bet.

Speaker crossovers are relatively complicated pieces of hardware, and a poorly-designed crossover can make for a lousy listening experience.

If you’re looking at a three-way speaker under say, $1,000, there’s a decent chance that it’s going to produce a lacklustre performance because the cost of designing an excellent three-way crossover just can’t be achieved in more affordable designs. As always, be mindful.

 

Impedance matching

If you’ve received an old pair of hand me down speakers from a relative, or purchased an older pair on Gumtree and you’re unsure of what you’ll need to power them, another need for reflection arises. Impedance matching. 

Stay with us here, it sounds like we’re heading into engineering undergraduate territory but it can be simplified.

Impedance is measured in ohms, in a speaker manual or on the speakers themselves you should see this represented by the Greek symbol for Omega - Ω. Ohms are a measure of electrical resistance, so the lower the impedance rating of your speakers (less resistance to current), the more work your amplifier has to do to power those speakers. 

Most speakers are rated at 4, 6, for 8 ohms. Remember what we said? Lower number means less resistance the current will face when moving from amplifier to speaker.

Why are we telling you this? An amplifier can power a speaker of ANY impedance, but if you’re driving a 4Ω speaker with an amplifier that isn’t designed to deliver a heap of power, the speaker will try and draw more current than the amplifier’s power supply is designed to output, and you’re going to find yourself with an amplifier that’s operating at a suitable temperature to fry an egg on. 

A bit of info to take on, but if you’re considering a new amp for a 2nd hand pair of speakers, the headache of figuring this stuff out now is going to pale next to the metaphorical migraine of torpedoing your brand new amplifier.

Make sure you check the impedance range your amplifier is designed to drive before you leap, it could save you serious frustration and a hole in your wallet down the line.

 

Sensitivity

This is less precarious territory when compared to impedances, but is still something worth taking stock of. All good speakers will provide you with a measure of sensitivity on their spec sheet.

It’ll generally look something like: sensitivity (1W@1M) - 89dB. If that induces a high school algebra flashback you have our apologies; in truth it’s quite simple. 

The manufacturer has placed a microphone one metre away from the speakers and run a single watt of power through it, producing a test tone that measured at 89 decibels.

Like so.

How does this help you? It gives you an indication of how much power these speakers will require to get decent volume levels and their best sound. 

A speaker with a sensitivity of 89dB or more would be considered to be fairly ‘efficient’ and wouldn’t need huge power to get the best possible sound, whereas a model rated at 88dB or less might need a bit more current to really get it purring.

These figures only work as a loose framework, but it’s safe to say that if you’re thirsting after a pair of 82dB speakers, you’re going to need some serious power to drive them.

 

Bi-wiring and bi-amping

Bear in mind that this isn’t an option for all speakers, but where your speaker of choice allows it, you may be able to tease a better sound out of your purchase without having to buy anything more than a second set of speaker cables. If your speaker terminals look like the picture below, then bi-wiring and/or bi-amping is something you can try.

 

These terminals that that are split between high and low frequencies make bi-wiring and bi-amping possible. If you’re just using one set of cable to your speakers, you’d leave those gold bridging plates in place. If you’re bi-wiring/amping, you’d remove them.

Every speaker has what’s called a crossover inside its cabinet. The crossover is a small board that takes the audio signal from your amplifier and splits it off into different frequencies so that the tweeter and mid/bass driver know which parts of the signal to push out.

On a speaker with multiple terminals at the back, you can run two sets of speaker wire from the rear terminals on your amplifier and into the two sets on the back of your speaker.

The easiest way do this? We’d suggest trying one set of speaker cables with banana plugs, and one set without. That way you can plug into the terminals on the back of your amp with the plugs for the high frequency posts on your speaker, and thread the exposed (non-banana) cable through the posts on your amp and run that cable to your low frequency plugs. Confusing? These might help.

The diagram on the left is self-explanatory. On the right, you can see the rear of an amplifier where bi-wiring’s being utilised.

In the case of bi-amping, you’re using two lots of speaker terminals on your amplifier instead of running two lots of cable from the one set of terminals. By now your brain might’ve started to ooze out of your left ear, so here’s another diagram.

This diagram shows how you’d bi-amp with an amplifier with two lots of speaker terminals. If you own an amplifier with only one set, then you’ll have to stick with bi-wiring.

From a physics perspective, this might not actually affect the signal path, what it does do is improve isolation because there’s more wire feeding each driver, so you may notice a small improvement to your sound for a relatively small expense. We think it’s worth experimenting with, just don’t expect a night and day improvement.

 

You should now feel empowered to make your speaker purchase, confident in the knowledge that you can avoid any possible pitfalls, feeling assured that you're setting up in your listening space with your speakers sounding their best. Good listening, friend.