I see day in day out, people that don’t understand power ratings. Most people don’t have the knowledge of power ratings in regards to car audio therefore they come to the ICE section and ask for advice. Now there’s a lot of people on here that are willing to give advice but most unfortunatly they themselves only know the basics.
I’ve written this so that people have the chance to gain a little knowledge on how to match an amp to a speaker and for those that like to give advice to be able to give the best/accurate advice they can.
THE BASICS
When buying an amp, whether it is to power a set of components or a sub always look at the RMS rating, ingnore the peak (max) power figure. Any brand that states these figures with no RMS figure should be avoided.
THE GAIN SETTING ON AN AMP...
...is not a volume control! It’s a signal matcher. (This is the biggest thing I must stress to everyone as setting this up wrong is the main cause for damage to a speaker). If you’ve got a 5v head unit the gain should be set to 5v, if you’ve got a 4v head unit set it to 4v etc. This is what you will produce max volume at anything over this figure and you will be sending a clipped signal from your amp to your speakers and this is what does damage.
The best way to have this done is to scope it or get someone at an audio meet to scope it for you, but if you can’t do this then the next best way is to set the volume to roughly 75% on your head unit and gradually increase the gain until you hear any sort of distortion, when you reach this point turn the gain back a touch and you should be fine.
For some people this could result in the gain being set at almost max and some around half way, it all depends on the head unit but the overall volume will be the same on both set-ups, don’t think “my mates got his set at 80% and mines at 50% his is going to be louder” it doesn’t work that way, some head units are better at delivering max volume at lower gain levels than others.
How many times have you heard someone say:
Quote:
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"You think this is loud, you should hear it when the amps turned all the way up it's only at half way at the moment"
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This clearly shows they have no knowledge of car audio and I guarantee that the speakers won't have a long life span.
SPEAKER (RMS) RATINGS
RMS values are what the speaker can handle without causing damage to a speaker, that is pretty self explanitory, that’s why people are scared to power a driver with more power than it is rated at but there’s no need to worry about power ratings.
I’ll explain why, an amp will only deliver it’s RMS rating when playing at both max volume and on sine wave (0db) tunes, music isn’t recorded at 0db therefore the speaker will never see the full amount of power when playing music, other factors such as amp efficiency play a part. Amps will only produce a certain % of the total power, class D (most mono) amps have the highest efficiency, class AB (most multi-channel amps) unfortunatly don't have such as a high efficiency rating.
If an amp is set up correctly (the gain setting) a speaker should be able to handle atleast 50% more power. So for example if you have a speaker that is rated at 100w RMS, then powering it with an amp that produces 150w RMS will be handled fine.
There’s alot of myths in car audio, some say underpowering does damage, some say overpowering does damage. Now underpowering doesn’t do any damage despite what you hear, so long as you have set the amp up correctly no damage will be done.
Overpowering on the other hand can actually be easier on your gear if set up properly. This is because If your amp and sub are both rated at (say) 500W RMS, you'll never get the most from the sub, because the amp will start to clip long before it gets near it’s rated power. However if you power a sub rated at 500w with between 750-1000w RMS then the amp gain can be turned down a touch which will allow the amp to achieve peak performance out of the sub without pushing itself too hard to achieve it.
Conclusion
When matching an amp to a speaker don't be afraid to buy an amp that produces more power than the speaker is rated at, somewhere around 50% extra will be fine so long as you take the time to set the gain up correctly. Having said this don't go crazy on the power, powering a 150w sub with 2000w RMS will kill it no matter how careful you are I just wanted to stress this before someone comes back and says they've done this because I said it would be ok to overpower the speaker
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OHM VALUES
A lot of people can’t get their head around ohm values, these are very simple once you realise how they work. Any driver (speaker) has a specific configuration, the most common are:
Single Voice Coil (SVC) or Dual Voice Coil (DVC)
Whether it is a single or dual it can be told by the amount of connectors the sub has, if it has 1 pair it’s a single VC, if it’s got 2 pairs it’s a dual VC.
The ohm value of the speaker can come in many different configurations, again the most common are:
Single 8 ohm
Single 4 ohm
Dual 4 ohm
Dual 2 ohm
These values can most likely be found either in the manual or on the bottom of the driver. The ohm configuration that the amp can run on depends on the speakers configuration, so if the speaker is a single 4 ohm driver then the amp will see a 4 ohm load, same with the 8 ohm etc.
Now if the driver is a dual configurated speaker then it can be run at a choice of 2 impedances (this depends on how a speaker is wired to an amp). The 2 choices will be either half or 2 times the speakers impedance. So if the driver is a dual 2, then the amp can be run at either 1 ohm or 4 ohm i'm sure you can work out the dual 4 ohm for yourself.
Have a play around on this website to learn how to wire a DVC speaker to amp to show a certain impedance,
Woofer Wizard.
If there's anything anyone wants to know that I haven't mentioned please feel free to PM me, you'll have to excuse me (for the next week) though if I don't get right back to you i'm currently in Brazil so I could be on the beach or something
or I could just be in bed due to the time difference.
Advice On Power Ratings (Amplifiers & Speakers)
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