RMS = Root Mean Square.. Mathematics..

But basically it mean the Average Wattage ur amplifier can do in long term/long time...

not the peak wattage or what rubbish PMPO wattage.. an amp can have a peak of 2000W but it will only have RMS 500W or below.. peak wattage mean the peak the amp can do in very short time.. say maybe 1ms...

normally u see those amp say have 2000W.. 3000w max.. all is rubbish rating...


But.. RMS wattage also different when the impedance is different.. say.. an amp have 200W RMS in 4 Ohms.. it may only have 100W in 8 ohms.. but car ICE equipment are normally 4 ohms...

normally now a day HU have 20-25W RMS.. although they state in front of the panel said 45W.. that is the programme W...

of course.. THD for HU.. so many things built into one.. the THD is greater...

@deniel.. as what u state.. ur HU are able to drive the spk.. but it won't drive the full potential of the speaker...

prefer the amp power greater than the spk can take.. u can always control the amp not to over blast the spk.. but when u have not enough power of ur amp.. u will tend to open the amp to higher that it can do.. going up to the higher limit of the amp, this is when THD come into play... u heard rubbish sound ( I hate it.. so I call it subbish sound) from ur amp...


in a better amp design.. say an amp can do 100w @ 10% of THD.. they will limit the amp to do up to say 80w.. to have lower THD.. say it will only have 0.1% THD...

Imagine u have 10% of distortion of a CD u playing.. those are.. unacceptable...

in consumer.. like those Hi-Fi Combo u can buy, always have very high THD.. say like 10%... when u open > 1/2 of it volume.. u don't want to listen to it...

THD = Total Harmonic Distortion..

for short.. it is Distortion..

U don't need to know what exactly is THD.. u just need to know.. it is distortion...

an co-axial speaker basically mean in a spaeker system, 2 driver sharing the same "axial".. that's why it call Co(two)-axial...

sharing the same axial meaning they sharing the same source center point...


beside, is it not recommend u buy a passive crossover seperately... when a multi way speaker is built, the crossover point of this kind speaker is predefine.. say.. in a 2 way.. the mid-bass doing 100Hz to 10kHz.. then the high doing 9khz to 20kHz.. then they have a crossover point around 9.5khz..

the pasive crossover will be create base on this crossover point and dedicated for this speaker system...

so.. when u buying a passive crossover, and if u donno wat is the corssover point of ur speaker.. and also the crossover point for the passive crossover.. that simply spoil ur speaker preformance..

where active one you have the flexibility to set the crossover point.. which Freq to cut as u like before if been amplifier...

u have a component set without crossover? u better double check the set have any crossover or not.. go n source for the crossover that come with the set..