underpowered speakers

alvaro3jr · 05-30-2005, 04:54 PM

I know you are supposed to match the rms ratings on speakers with your amp. Now what I want to know is if you have an X brand speaker with an RMS rating of 50 watts and the same brand speaker with 90 watts rms and you use an amp that offers 40 watts rms. Will the speakers sound different. I know you need the full rms ratings to achieve the full potential of the speakers, but will they sound any different with the same amount of watts?

Just for info I am looking at buying some Infinity Kappa's. The amp I am looking at is a Kicker 5-channel that puts out 40 watts rms X 4 and 140 rms x 1. The Kappa's rms ratings are 100 watts for the 6x9 and 90 for the components. Not sure on what sub I am going to use.

Sammy Sandbag · 05-30-2005, 05:49 PM

I wouldn't run the Kappa's with anything less than the recommended RMS power, I've used them in the past with lower power and they didn't sound very good. I'm running 4 Kappa 6.5" in the Titan right now with around 100w RMS to each. I'd lose the 6x9 and go with a 6.5 or 6.75 also.

badlooser · 05-30-2005, 06:55 PM

I agree you should always try to match the RMS rating of the speaker to the amp but you can always overpower them and turn the gain down to match the speakers and now your amp will be producing cleaner power and better sound with less distorsion.

titanse05 · 05-30-2005, 07:25 PM

Match the power ratings....more power the better.

I agree with Sammy that underpowering a component set is a waste. Do it right the first time and follow your own advice. Whatever you decide, keep us updated.

rdfeatherstone · 05-31-2005, 02:07 AM

One issue you didn't mention is efficiency of the speakers. Some are very efficient and can run low power effectively. Others require high power, as Sammi mentioned.

Stick to manufacturer ratings for both the low end and high end power ratings.

alvaro3jr · 05-31-2005, 07:44 AM

I think the efficiency of both is 90dba. I saw a pheonix gold amp w/100 watts rms per channel for about the same money as the kicker. I have never run a phoenix gold amp, but I have heard good things about them. Any input?

I am not set on either the speakers, or the amp. I am not looking for competition sound, just something cleaner, and of course just a little louder.

eakes · 05-31-2005, 11:03 AM

Do not confuse maximum speaker power ratings with recommended power ratings. The numbers I seen on most speakers are max. power ratings, that is, not to be exceeded. The max rating is there to specify how much power can be supplied to a speaker before it will go 'poof'. The power a speaker requires depends more on how it is mounted. A speaker mounted in an air-tight box requires more power than the same speaker mounted in a ported box. And both require more power than a speaker mounted in an 'infinite baffle' configuration, ie, really big box or free to air.
Obviously, trying to drive a 10 inch speaker mounted in an air-tight box with a 5 watt amplifier is folly. But just because the max rating on the speaker is 200 watts does not mean a 200 watt amp is required to drive the speaker properly. Quite likely anything between 75 watts and 150 watts would be more than adequate - unless one is striving for a competition level system.

Justintoxicated · 05-31-2005, 11:17 AM

Id get components over 6x9's for SQ, if you just want loud then 6x9's are fine but won't be able to produce the clean sounds components can.

Power rating vary by manufacturer. Some are over rated (Audiobahn) and others are underrated. You want them to be close though. I prefer to have a little extra power myself.

JLTD · 05-31-2005, 01:30 PM

The idea that the speaker somehow detects what size of amp it's connected to and then alters the way it operates based upon this is silly.
It's not possible to "under power" speaker and cause any ill effects. It's actually #1 on the top ten myths in car audio.
If this were true our speakers would sound like crap and/or break unless we listen at full volume all the time. As we turn the volume down the speakers become more stressed and sound poorly.
#2 myth is "Clipping by producing harmonic distortion and/or DC blows speakers". This is another story, but it always comes up when I talk about #1.

Justintoxicated · 05-31-2005, 02:19 PM

Quote:

Originally Posted by JLTD

The idea that the speaker somehow detects what size of amp it's connected to and then alters the way it operates based upon this is silly.
It's not possible to "under power" speaker and cause any ill effects. It's actually #1 on the top ten myths in car audio.
If this were true our speakers would sound like crap and/or break unless we listen at full volume all the time. As we turn the volume down the speakers become more stressed and sound poorly.
#2 myth is "Clipping by producing harmonic distortion and/or DC blows speakers". This is another story, but it always comes up when I talk about #1.

my my experience this is not 100% correct, some speakers do not have linear efficiency, so they won't sound as good unless they have more power going to them, 50 watt RMS going to a W7, or worse a very in efficient sub, isn't going to make hardly any noise. And yea they sound less good when you turn down the volume. So like you said, people turn up settings that create clipping which blows the speakers or amp. So if your underpowering a speaker by less than 1/2 it's power it might not be as audiable, thus you change settings to compensate for the low level of output which causes the amp to clip, so you get a crappy signal to the sub and can damage it.

I don't think he was asking if he would blow his speakers with an underpowered amp, but asking if it would work correctly.

For example you have a sub that recomends 100 wats RMS and you provide 50 watts RMS and the sub is not Linearly efficient, it might need 70-100 RMS to hit really hard. Because you know the sub is underpowered you turn up the Bass which causes the output signal to be boosted and makes the speaker louder, however, it does not have enough power to move the speaker properly and causes the amp to clip and you damage your sub or overheat your amp... Now if you had not changed the Bass it would probably not be very loud and you would probably avoid clipping, so it would not damage the sub or the amp.

JLTD · 06-01-2005, 01:57 PM

You go find a 50 Watt RMS amp and connect it to a W7 and see what happens. That is if you can find one that can handle 3 ohms and the W7 motor (no chip amps).
Clipping is another issue and has nothing to do with the topic. The topic was #1 and Clipping was #2. I tried to nip it in the bud, but I guess the Myths are too deeply imbedded. So I guess I will go through it.

#2 "Clipping by producing harmonic distortion and/or DC blows speakers"

What is harmonic distortion?
Harmonic distortion is high frequency noise which is a by-product of clipping.

So high frequency noise blows a speaker? How?
The inductance of the voice coils and/or x-overs absorb high frequencies so no problem there.

Does DC blow speakers?
Sure it can. Hook up a speaker directly to a car battery and watch it cook.

But how much DC is coming out of an amp?
Some people seem to think that you can connect a DMM to the outputs of an amp to read DC. The reality is the actual DC content is very small even when driven into clipping. Any reading you would get with a DMM only prove that signal and output devices are not always in sync. The reading is the difference in potential.

So what does kill speakers?
Excessive average power over time.
Clipping dramatically increases average power over time. Amplifiers that are driven into severe clipping will produce average energy like an amp twice it's size. By the way, everyone drives their sytems into clipping....levels of 10dB are not uncommon.

Here is an example of a clipped signal and one that is not:

If the line on the top and bottom of the graph equals the maximum output of an amp, notice how little time the unclipped signal spends at max power. Now look at the clipped signal and notice how much more time we are spending at max power.
Keeping this in mind, lets go to your 50 Watt amp example. I have one connected to my 13W7 which is rated for 1000 Watts. If you're right, this subwoofer will fail because it's connected to too little power.
How?
Even if I railed the hell out of the amp, it would produce lots of harmonic distortion... the voice coil would laugh. It's unlikely that the suspension would be very stressed.
What about heat?
Well, if I did drive the amp into severe clipping and it produced 100 Watts worth of heat energy, the voice coil is rated for 1000 Watts. No problem there either.
Clipping is clipping. Everyone does it and they are not going to stop just because they get bigger amps. What does change is the amount of damage that can be caused (by getting bigger amps).
The only difference in performance between a 13W7-250/1 system and a 13W7-1000/1 system is 6 dB of potential. Both systems can (and will) be driven into clipping by the typical user.

The universe if ruled by the laws of physics not by the laws of man. It is my policy not to argue on the internet so there is a good chance this will be my last post on this topic.

Justintoxicated · 06-01-2005, 02:32 PM

lol only 6DB, thats 4 times as loud! big difference... W7 power wise sounds like it has very linear based response as in if you double the power you get twice the ouput...This is not the case with all speakers...I never said you were wrong btw, I agreed with you.

What the hell is the point in getting a W7 and running it at 1/4th power?

The W7 sounds pretty efficient if that is the case with 250 watts versus 1000 watts being 1/4th the volume, but some subs are not.

Also some subs require 2x as many watts as another that produces the same amount of volume with 1/2 the power.

so you could underdrive your stuff, but it's better to get the proper amplifier so you can turn it up louder without messing with the signal to compensate for being less powered which can drive it into clipping more often.