Barefaced Bass

Firstly we need to consider how much power a cab can really handle.

Although we do not quote a power handling figure the Compact is thermally rated at 450W - that is a continuous figure - the peak thermal rating is closer to 2000W. The more important power handling spec is the mechanical or excursion limited power handling rating - this is based on a combination of the speaker area, sensitivity, frequency response, maximum excursion and the cab alignment (combination of internal volume and tuning).

The Compact is mechanically rated at 400W. A high quality neo 2x10" will typically have a thermal power handling rating of 500W. However its mechanical power handling is likely to be less than 150W because the excursion limits of the speakers are much lower. Secondly the output from a speaker is dependant on sensitivity as well as power - a 98.5dB sensitivity 8 ohm nominal impedance speaker will produce 123.3dB with 300W input, whilst a 97dB sensitivity 4 ohm nominal impedance speaker (this is a fairly accurate sensitivity spec for a high quality neo 2x10" even if many manufacturers are claiming close to 100dB or more) will produce 124dB from a 500W input (because the amp produces more power into a 4 ohm load).

If we combine the sensitivity figures with the mechanical power handling we see that the Compact can still produce 123.3dB with this amp, whilst the neo 2x10" can only produce 118.1dB. So if we go back to our original question, wouldn't I be better off with a 4 ohm cab to get full power from my amp, the short answer is no.

The reason is that although your amp will deliver more power into 4 ohms unless your cab is very large or your amp is very low powered, your cab will not be able to handle the extra power. The Compact can handle more power than most but because its sensitivity is high it rarely needs extra power.

If your cab is very large then it's a bit unfair to compare it against the small and superlight Compact! How would your cab compare to two of Compact 1x15" cabs? A pair of them will give you 101.5dB sensitivity, 900W thermal power handling, 800W mechanical power handling, and a 4 ohm nominal load. Maybe it's time to replace that fridge!

Addendum: Since writing this another issue has come to light, which is that the new breed of superlight amps cannot generally sustain full power output without running into thermal problems. All amps run hotter at lower impedances so you will run into thermal problems sooner with a 4 ohm cab than with an 8 ohm cab. That shouldn't be an issue with speakers this sensitive but it just goes to show why lower impedance isn't an advantage.

Underpowering is one of those myths that will not die. You cannot damage a speaker through putting too little power into it.

To clear up the DC issue, a correctly functioning amp, however badly it is clipping, should never generate DC.

However clipping does have two risks - firstly that a fully clipped amp can produce almost double its rated power. This is only a problem if you keep the amp running fully clipped for a length of time and your speaker's thermal power handling is less than twice the amp's rated power output. Fortunately in the real world this will never happen - we play bass, which by its nature has loud moments and quiet moments, thus power output is never constant. If you use an amp within the recommended power range for our speakers then you will not have a problem unless you are seriously abusive.

The second risk with clipping is that most of the extra power is actually in the higher frequencies. This means that if the cab has a tweeter it is likely to receive more power than it can handle. However if you have a tweeter then you should be able to hear the clipping and react by turning the amp down. The plus side for our designs is that the rising impedance of a woofer with frequency actually protects the woofers from having to handle extra power (amplifiers are voltage amplifiers and the power that comes out is simply the voltage squared divided by the impedance at that frequency).

So to recap, although your amp can produce more power when it is clipping, the majority of that potential extra power won't actually flow through your speaker unless you have a tweeter, in which case it will make a really ugly noise before the tweeter dies (which is why a well designed speaker should incorporate tweeter protection circuitry).

If you use an amp within the recommended range then you are unlikely to have a problem.

However this does not mean that you can do whatever you like with that amp and the speaker will not be damaged - if you turn the amp up so loud that the speaker starts making bad noises (distortion, farting, etc) and you do not react to these warning sounds then the speaker could be damaged. Fortunately these speakers are pretty tough but if you want to you can certainly break them. If you do them I will be happy to sell you replacement parts but they will be expensive.

You can certainly use more power than recommended but be aware than even with the volume controls set at less than halfway your amp can still produce full power given a hot enough input. More power could give you marginally more output but you will have to be more careful to avoid damage. But don't worry too much about a few hundred watts beyond recommended, the risk is more if you're using a multi-thousand watt PA power amp bridged into a single cab.

Bigger speakers sounding slow is another one of those myths.

The speed at which a speaker can move is what limits its high frequency response. There are no speakers that I know of that have such limited high frequency response that they sound slow across their working frequency range. If a speaker can reproduce a given frequency then it will not sound slow at that frequency. If it can't reproduce a frequency then you could claim that it sounds slow at that frequency but because it can't reproduce that frequency then it doesn't sound like anything at that frequency, least of all slow!

Answer: It all comes down to the ability to move air!

The amount of air a speaker can move is equal to its cone area (Sd) multiplied by its maximum excursion (Xmax). This is called volume displacement (Vd). The 10" speaker has Sd=355.4 square centimetres and Xmax=3.2mm therefore Vd=114 cubic centimetres. Our 15" speaker has Sd=881.1 square centimetres and Xmax=9.6mm therefore Vd=846 cubic centimetres. So the single 15" woofer we use can move as much air as seven and a half 10" woofers. Not bad at all!

We should also point out that because The Big One uses a tuned port to supplement the low frequency output that this can almost double the amount of air a cab can move compared to a sealed cab, so The Big One can produce comfortably more low-end than the big classic sealed 8x10" that you see on every stadium and festival stage.

And the most shocking thing that it really isn't very big - it just sounds it!