Power Matching
Wondering if its ok to run your 600watt sub off your 200watt amp? Or what will happen if you put 2000watts into your 150watt 12″ sub? Very few people have or want matched power ratings. We give you the advantages/disadvantages and hazards of these situations.
Real power ratings
First of all it’s important to realize the true power ratings/handling of your systems components before reading the rest of this article.
A list of related articles can be found below.
Under powering speakers
If they were each to receive 200watts RMS from an amplifier, a 200watt RMS speaker would play both louder and clearer then a 400watt RMS speaker of the same quality and size
This is because the power is better matched to the suspension abilities (mechanical resistance to cone movement) of the 200watt speaker. It would have both a higher degree of cone movement and increased cone accuracy and control. This results in improved sound quality and volume.
On the other hand, the 400watt speaker’s cone would be far from its maximum extension. The stiffer suspension, required to handle 400watts, will decrease the speaker’s responsiveness and accuracy when receiving only 200watts.
A user frustrated with a lower volume than expected from a 400watt speaker, powered by a 200watt amp, may be tempted to turn the volume up a little higher on the source unit. Or maybe increase amplifier power output by playing with its gain settings. Eventually this will lead to distortion, which is very bad for your speakers.
There is no benefit from under powering speakers. In fact it is the most common cause of speaker damage. However, it can be safely done providing that the speakers receive a distortion free signal from the amplifier (either head unit amp or external amp)
Heat Vs Speakers
Heat produced in the voice coil is the enemy of your speakers. A speaker cools its voice coil when the cone is moving. As the voice coil moves out of the magnet cool air is drawn in behind it. When the coil retracts back into the magnet, hot air is pumped back out.
When a speaker is underpowered this cooling process is already operating at less then its full potential. The cone is moving at less then its maximum extension and speed. Add to this the fact that the cone is not constantly moving as a result of distortion (receiving bursts of DC), it can quickly lead to damage requiring repair or replacement to your speakers.
When a speaker is overpowered more power travels through the voice coil then it was designed for. This extra power causes extra heat, which the cooling process may be unable to cater for.
At some stage an overheated voice coil will melt or burnout. If a voice coil fuses together this can dramatically change a speakers electrical resistance and possibly damage the amplifier that powers it. Most good quality amplifiers have built in protection against this scenario.
Over powering speakers
RMS and nominal power ratings are almost always conservative. Therefore it is safe for quality speakers to be pushed past their rated power to some extent. Many manufactures actually recommend overpowering speakers to achieve the best results, commonly by as much as 20%. In general a speaker will play louder and clearer when pushed past its rated limit. However, this is risky territory because at some peak or after some length of time, either the speaker’s suspension will be pushed past its mechanical limit or the voice coil will burn out. In either situation the speaker will fail.
Running lower power speakers off higher powered amplifiers is often called giving them “headroom”. Many songs have peaks where for a short time the music is considerably louder then the rest of the track. An amplifier whose power is matched to a speaker may be generating its maximum power during a normal part of the song. When the song reaches a peak instead of increasing its power output the amplifier clips or distorts. A system with amplifiers that have more power then is normally required, will therefore have a better sound quality as its amplifiers have power reserves or “head room”.
Take the previous example of the two speakers. If both are now given 400watts RMS, the speaker rated at 200watts will once again play louder then the 400watt speaker. However, the 400watt speaker will last continually for at least 24 hours at this pace without damage. The 200watt speaker would last for maybe half an hour (depending on its build quality).
Although quieter the 400watt speaker would likely have better sound quality reproduction. The 200watt speaker may show a more controlled movement but its cone would probably be pushing past the suspension travel limits that it was intended for and could be “bottoming out”.
SPL (Sound Pressure Level) competition
During sound off competition it is very common for subs to receive power well in excess of their ratings. An example of this was the recent Auckland Auto salon sound off, where one competitor pushed 10,000 watts RMS into each of his 1500watt subs. While this resulted in the early destruction of some extremely expensive gear, if the subs had of survived a very high result would have been achieved.
SQ (Sound Quality) competition
While speakers are also overpowered in sq competition it is to a much lesser extent then in SPL. A balance must be reached between maximizing the responsiveness and accuracy of a speaker and reaching its mechanical limits.
It is important in SQ competition to give your speakers sufficent Head room
Defeating power differences
With subwoofers a smaller sub box can be used to help reduce cone movement when they are overpowered. This will increase the effectiveness of the speaker’s suspension by providing a more restrictive air cushion below the cone.
Similarly when underpowered a larger box can be used to decrease the effectiveness of the suspension and increase cone movement. This will increase volume but will not help overheating caused by distortion.
Related Articles
Understanding Power Ratings
Speaker Configuration / Ohms
The advice given within this article is to be taken at your own risk. nzicemag will not be held responsible for any damage resulting from the use of information contained here in.
