I have a head unit that is 4*45 watts connected to 6*9's that are 50 watt continuos 100 watt max. Is it worth installing an amp for an extra 5 watts? How big of an amp? I am a noob to audio equipment so excuse me if this is a stupid question

Yep, you will get value out of an amp. Head unit power ratings are for momentary peak power outputs. Continuous power output of a headunit of that spec is (as teK-- said in another thread recently) closer to 20W RMS.

if u wanted, i have a kenwood KAC-625 2 channel amp which has 2x40w RMS. this is one of the older kenwoods, the higher quality ones ive bin told. this amp powered my kenwood 6x9's (80w RMS each) pretty well. PM me if ur interested

If u connect an amp, basically, the amp will be upping the power to the speakers and not the head unit, and it will be alot more clearer at higher volume as the headunit wont be struggling to up the volume.. Cause the amp has it covered.


As an example, say ur playin ur music on the head units almost full volume capibility, at 45w rms going to the speakers. the sound will be starting to sound very screachy and not too clear, especially bass and higher frequency treble.. If you have an amp hooked up, if you have the HU volume on 3/4 of the way full, the amp will be amplifing the sound and give u the same dB level of loudness as in the first scenario, but without any struggle or, 'distortion' if u like..

Thats what it will do in lamens terms i guess.. its not really about the extra 5w off power, its about clarity.

Gerard is on the right track. As he says; the power you have the control you have and as you turn it up the distortion you'll begin to hear is not the speakers having issues, it's the internal amplifier in your headunit. Seeing as he is taking care of th real world explanation I'll explore the technical side a little further. TRMAGNA, if you're new to this sort of thing you might wish to read this champ just to get a little more info on board. ;) I was asked a similar question in another forum and the answer I gave was this:

Remember your headunit has an internal amplifier as well, just like those massive externals one, just smalled. It is too be treated no different to any other amplifier in the way it works. Now distortion and clipping are to different things. This text is taken from the FAQ section on my website, please read:

What is clipping?

Underpowering the speaker can easily damage it if the person running the stereo doesn't realise the amplifier is beginning to struggle. This resulting damage is usually casued by the amplifier being overworked and 'clipping'.

The more technical minded explanation on clipping is that when a woofer is driven with a high powered amplifier to high levels, there will be a significant amount of current flowing through the voice coil. Since the voice coil has resistance, there is a voltage drop across the speaker's voice coil. This means that there may be a great amount of power being dissipated (in the form of heat) in the voice coil. When a speaker is driven with lots of clean power, the cone moves a great deal (in proportion to the output voltage from the amplifier). For speakers with vented pole pieces (or other types of venting), this movement forces a lot of air to flow in the magnetic gap (area where the voice coil rides). When the woofer moves out of the basket, the chamber that's under the dust cap and around the voice coil expands (increases in volume) which pulls cool air into the magnetic gap. When the woofer moves the other direction, the chamber size is reduced and the hot air is forced out of the vent in the pole piece. This air flow cools the voice coil. If a relatively low powered amplifier is driven into clipping (to a full square wave for a lot of people), a relatively large portion of the time, the voltage delivered to the voice coil no longer resembles a sine wave as it would with an unclipped signal. While the amplifier's output is clipped, the voice coil is not being motivated to move as far as it should for the power that's being delivered to it and therefore is likely not being cooled sufficiently (since the speaker is driven by a linear motor, the voltage applied to the voice coil determines how far the voice coil moves from its point of rest). At points a, b, d, e, f and h the voltage is changing causing the voice coil to move in the gap and therefore pull in fresh cool air. At points c and g, the voice coil may still be moving a little due to momentum but may not be moving enough to cool properly. Remember that during the clipped portion of the waveform current is still flowing through the voice coil. Since the displacement of the voice coil (and therefore the airflow around the voice coil) is no longer proportional to the heat being generated, the voice coil can overheat. This excess heat may cause the voice coil former to be physically distorted and/or melt the insulation off of the voice coil wire and/or cause the adhesives to fail (especially if the speaker is rated to handle no more than the power that the amp can produce cleanly). If your speakers are rated (honestly) to handle the maximum 'clean' power that your amplifier can produce, slight clipping isn't generally a problem. Severe clipping is more likely to cause a problem.

http://www.fastfoursforumscarclub.com/temp/fhrxstudios/images/amp_clipping.jpg

Then there is severe clipping (aka square wave). It always amazes me when I hear some idiot driving down the road and the audio is clearly distorted (you know what I mean). Many people drive their amplifiers into what could be called a square wave output (white line below). When an amplifier is pushed that hard, it is actually possible to drive the speaker with twice as much power as the amplifier can cleanly produce into the speaker. As you can see below, the yellow sine wave is the maximum 'clean' output that the amp can produce. When an amplifier is pushed way too hard, the signal will eventually look like the white line. The effective voltage of the white line is ~1.414 x the yellow line. This means the the total power driven into the speaker by the clipped (square wave) signal is double the power delivered by the 'clean' signal (yellow line). This means that the power is double but the cooling of the voice coil will not increase in proportion with the power increase (since the voice coil isn't moving as much as it needs to be for the given power dissipation). This will lead to the voice coil overheating. If we compared the output of a 100 watt amp (the one that's clipping) to a 200 watt amp, the 200 watt amplifier would be able to push the speaker as much as 40% farther than the 100 watt amp (depending on the frequency of the signal). This extra travel (in each direction from its point of rest) would result in added airflow around the voice coil.

http://www.fastfoursforumscarclub.com/temp/fhrxstudios/images/amp_extreme_clipping.jpg

Note: The RMS voltage of a pure sine wave is equal to the peak voltage multiplied by 0.707. The RMS voltage of a pure square wave it equal to the peak voltage. For 2 waveforms with equal amplitude (as shown above), the RMS voltage of the square wave is 1.414 times the voltage of the sine wave. If we use the example of the 100 watt amp which can produce a sine wave of 20 volts RMS, we can see that the output power at hard clipping is double the power it can produce cleanly.

The next post will be about distortion.

Now we've done clipping, lets look at distortion.

What is distortion?

Well, to get a little more complicated, distortion is any departure from a true and accurate reproduction of the original waveform. It can include Noise, Clipping Distortion, Harmonic, and Intermodulation Distortion. These last two forms are fairly common in loudspeaker reproduction and can be reduced but not entirely eliminated in the existing technology. It would be fair to say that modern amplifier design fairly eliminates nearly all forms of inherent perceived distortion, leaving only that caused by inappropriate user settings and overloading.

Distortion is the name given to anything that alters a pure input signal in any way other than changing its size. The most common forms of distortion are unwanted components or artifacts added to the original signal, including random and hum-related noise. Distortion measures a system's linearity - or nonlinearity. Anything unwanted added to the input signal changes its shape (skews, flattens, spikes, alters symmetry or asymmetry). A spectral analysis of the output shows these unwanted components. If a circuit is perfect, it does not add distortion of any kind. The spectrum of the output shows only the original signal - nothing else - no added components, no added noise - nothing but the original signal.

It's rather amusing to see amplifier manufacturers making great claims about the advantage of the extra .001 % Distortion they've wrung out of their products, while most speakers are considered very good if they can keep such distortions below 5 %. It's true that the reduction of any distortion anywhere is a positive contribution to the goal of high fidelity, but the disparity between the two technologies in this regard points up the largely subjective nature of many such claimed advantages.

Here are some of the definitions:

Noise is perceived sounds not in the original soundtrack. Such things as hiss, crackle, pops, hum, and buzz, are typical of the types of extraneous signals described as noise. Inherent noise in the electronic processing in any sytem is measured in decibels relative to the amplitude of the original signal. Sounds perceived as noise are heard in contrast to the sound that is the object of attention. Thus, a noise signal measured at 15 deciBels below the output of Tchaikovski's 1812 Overture finale would probably not even be heard; while a slight hiss at 55 dB below the level of a soft piano passage would be annoyingly obvious.

Harmonic Distortion is a type of Distortion in which resonance or sympathetic ringing vibrations are added to the original sound to produce second and third harmonics of a fundamental tone in a way that was not present in the original signal. Choosing good Drivers and a well-made enclosure design is essential in overcoming this tendency in speakers.

Last but not least (well maybe) is Intermodulation Distortion. This is the Distortion that results when one set of frequencies is superimposed on, or is modified by, another to produce a third frequency not present in the original signal. Quantifies the distortion products of nonlinearities in the unit under test that causes complex waves to produce beat frequencies, i.e., sum and difference products not harmonically related to the fundamentals.

Now the important bit (sorry I know it's been a lot of reading but it is important)...

Why did my speaker distort / blow?

In most systems when you hears the speakers 'distorting' it's not the speaker that is struggling, it' the amp. Speakers are quite simple devices, all they do is reproduce the sound given to them regardless of what that sound may be.

When you ask an amp to do it's job, it takes a relatively small sound wave and amplifies it before sending that bigger signal to the speakers. If you ask it to do more than it's capable of (by turning the volume up full blast), it still tries to do what you have asked, but the new amplified sound wave becomes rough and sketchy due to the amp having to clip the top and bottom of the musical wave in order to produce the amplitude you have asked it for.

Imagine for a second a weight lifter. He is on the bench doing bench presses. With 100 pounds his movement will be nice and smooth and he'll be almost faultless in his technique. Now you throw on another 300 pounds. He may still just be able to do it, but his arms and legs shake, his breathing becomes irregular and it looks woeful to watch.

You amp does the same, it still attempts to do what you have asked of it, but it sounds dreadful and you get that 'distortion' everyone talks about. And here lies the biggest problem - most people assume the speakers are dying, so they go and get a SMALLER amp and as you can imagine from reading above, the problem is just amplified (sorry, couldn't resist throwing that pun in! :p ). Anyway, it gets worse. The resulting nasty wave is then transferred straight to the speaker which tends to knock the speaker itself around a fair bit. It also causes the speaker voice coil to heat up significantly as the stays are full power for longer periods during the sound wave during clipping.

Now don't get me wrong, you can fry your speakers with too much power, but there are only two main ways to destroy a speaker. One is thermal (where the voice coil and/or the former melts because of too much current flowing through it) and overdriving (where the voice coil and former hit the bump plate on the bottom or tear the surround and/or spider(s) and pop the cone out the top).

Usually the volume is somewhat louder than one would be comfortable with before failure occurs.

Like I said, sorry about the long rant but it is important to get these things out for better understanding all round. :)

man... this dude knows his stuff.... 10/10 for that answer Fhrx

Sorry about the rant, I just thought it might be a good idea to explain it all rather than leave it go... :)

Thanks heaps for that mate, before that i knew absolutely nothing. Now I no that it is worth geting an amp how many watt amp should i get and how many channels. I may want to run a sub in the future so i was thinking 4 channel 200w. this may be completly wrong but from what ive herd it would be alrite

Okay, one more lecture just to help you on your audio way. This is also taken from my website and will assist you when you're looking for a new amplifier.:p

What amplifier specs should I look out for?

Choosing an amplifier is about more than just watts. When speaking to anyone about achieving quality music in car audio most people simply focus on the speakers rather than the amplifier. They often speak about speaker build quality and power handling, enclosures, porting, fibrefill, loading and speaker cable. You don't really need to worry about the amplifier so long as it's powerful enough right? Just like when you're considering the purchase of a new car; the only thing you need to look at is the power output of the car alone right? Wrong.

When choosing an amplifier to power your speakers there are more stats than just power output you need to think about before you splash a couple of grand on an amp that will sound like rubbish. For those among you dreading an upcoming lecture on amplifier classes, resistors, capacitors, transistors, transformers and power supplies relax, I'll keep this to plain English for the explanation of which stats to look out for. High power output is important but quality amplifiers are not just about sheer power. Mining dump trucks have over 6000 horsepower but that doesn't make them spectacular performers. Besides power there are certain other important figures that must be taken into consideration when choosing a suitable amplifier. We'll go through a few of the more commonly found stats.

Damping Factor
Damping factor describes an amplifiers ability to control a woofer cone. It's the ratio of rated load impedance to the internal impedance of an amplifier. The higher the damping factor the more efficiently an amplifier can control unwanted movement of the speaker coil. High damping factor is crucial for subwoofers and the higher the damping factor the better. It is debatable if anything over 50 is audible. Damping factor is calculated by dividing the speaker impedance by the output impedance of the amplifier. In other words the damping factor will decrease as the speakers impedance decreases. This means an amp optimised at 4 ohms will provide tighter bass than when they're running at 2 ohms. A lower damping factor will leave bass notes sounding soft and undefined, regardless of the amplifiers power output. You can see by this that a smaller 100 watt amplifier with a high damping factor can often sound better than one twice it's size with a low damping factor.

Slew Rate
Sometimes referred to as damping factor for tweeters, the slew rate describes the amplifiers ability to accurately control fast direction changes of a speaker cone or dome. Have you even turned your stereo up to discover that your cymbals sound like someone throwing a brick through a glass window? That's because the amplifier simply wasn't fast enough to accurately reproduce the high frequency ring of the symbols. Measured in volts per microsecond, a low slew rate softens the definition of a sound signal which blurs transients and causes the sound to appear muddy. A high slew rate means the amp responses faster which ultimately results in crystal clear highs.

Total harmonic distortion
THD is the measurement of the how much the amplifier can distort the sound signal through the introduction of added harmonics or overtones. THD figures are usually given as percentages and a THD figure below 1% are generally inaudible to most people. However, distortion is a cumulative phenomenon so if your head unit, eq, crossover and amplifier are all rated at less than 1%THD each, together they could produce 5%THD which may well be noticeable to most of you.

Signal to noise ratio
Noise leaking into the sound signal is an ever present problem in car audio. The Signal to noise ratio is a measurement of noise level in the amplifier compared to the level of the signal. A higher S/N ratio signifies a greater difference which is better. Technically speaking, it's the ratio expressed in dB of signal power at a reference point in a circuit to the noise information that would exist if the signal were removed (the noise floor). The maximum signal to noise ratio of the amp can be seen as a measure of realistic fidelity. This ratio is how much absolute noise it produces compared to the highest signal voltage it can pass without distortion. Many companies combat noise by utilising balanced line systems.

Stereo separation.
Separation is not spoken about much but this refers to the amplifiers ability to maintain the separation between the right and left channels. This is essentially what allows an amplifier to reproduce an accurate sound stage. Each individual instrument is after all, are recorded in it's own location in the sound stage and you should be able to hear this in the same way when it's played in your car.

Just a final few points to remember while you're looking at specs. You'll find many are followed by the term 'A weighted'. Put very simply, 'A weighting' is a way of colouring the figures a little to make them appear more attractive. Loading is another issue to consider. Watch the impedance of speakers when choosing them because while most amps are stable at low impedance levels, they're not overly efficient nor performing 100% when loaded down. Your cars engine is 8000rpm stable but it's unwise to try and keep it there for long. By the same token many amps are 2 and 1 ohm stable but this is for intermittent spikes (as music is dynamic it causes the speakers resistance to continuously change during playback), not continous everyday running. These are some of the more important figures to observe when buying amplifiers. It's not simply just a matter of buying which ever amp outputs the most power. It's a matter of taking all the figures into consideration and choosing which amplifier best suits your needs.

Dude have you got a site or somethin? If not u should make one with info like this :)

Dude have you got a site or somethin? If not u should make one with info like this :)


This is also taken from my website and will assist you when you're looking for a new amplifier.:p
Yeah he does, just click on the link in his sig:) He sure knows his stuff!

Oh my bad, didnt see that.. must be late lol

I moved here from Canada, and they think im slow.. Aye..

Hehe. Yeah champ , have been doing car audio for the better part of twenty years now and operate a high end audio store down in Sydneys south.

Fhrx Studios (http://www.fhrxstudios.com).

Don't worry about that much though, because I'm still learning every day just like everyone else does. :)