What size amp?

No one want to help a young lad :(
Im just a little confused whether the amp has to be 1000 watt or 250?
 
An AMP also has peak and RMS values, so you would try and match the RMS values of the sub and amp as closely as you could afaik.
 
Jjustme said:
An AMP also has peak and RMS values, so you would try and match the RMS values of the sub and amp as closely as you could afaik.
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So you mean i match a amp that equals the RMS value of the sub?
Bit of a "noob" when it comes to this :/ sorry
 
^^ I think he means match the amps RMS with the subs RMS, and the amps peak with the subs peak?
 
You want the RMS to be similar, it doesn't have to be dead on, but too high or too low can damage the speakers/not work very well. Peak doesn't really mean a lot.
 
If you're buying from there, you're probably better off looking at the sub and amp packages rather than picking them out separately, you'll likely end up with a model up for similar money.
 
You need the speaker to be able to cope with more than the amp can send, else you risk blowing it, at least that's how I do it with guitar speakers and amps. It says 250W RMS, so get an amp that's less than that, and less than 1000W peak.
 
death_looms said:
You need the speaker to be able to cope with more than the amp can send, else you risk blowing it, at least that's how I do it with guitar speakers and amps. It says 250W RMS, so get an amp that's less than that, and less than 1000W peak.
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Incorrect. Your amp will start cutting as it can't pump enough power that the sub is drawing. Your amp should be around 2x the power of what ever is plugged into it and turn the gains down to suit.

It's like PC PSUs, you wouldn't stick a 200W PSU in a 500W draw...
 
Liquidfox said:
It's like PC PSUs, you wouldn't stick a 200W PSU in a 500W draw...
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Have to disagree, a speaker doesn't draw power from an amp, an amp pushes power to a speaker. The speaker has very little impact on how much power comes to it, save for it's impedance (which you should match to the amp). In a PC, you start playing a game, the GFX starts pulling more power from the psu, in this case the control comes from the gfx. For audio, you turn the AMP up, and increase the power sent to the speaker, with the amp as the control. Too much, and you blow the speaker. I have done this before (expensive mistake!).
 
You can toast a speaker/sub by both too MUCH power and too LITTLE power. Too little causes clipping and distortion which can blow a speaker, too much will overheat the voicecoil(s) and melt them. pretty similar end results by slightly different means.

some subs will be able to cope with 2 x their quoted RMS value, others will have very little tolerance over the quoted. I go with an amp with a similar RMS output and it should be fine. As long as you don't drive the amp to clipping levels then all should be fine.
 
death_looms said:
Too much, and you blow the speaker. I have done this before (expensive mistake!).
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wrong. ive been a car hifi geek for years. ive been there, got ten t shirts, ive done it.

a 250rms sub, if you run it with 200rms you are far more likely to run the pair to the limit of the amp, which leads to clipping, where signals going to the coil end up flat lining... you get a cone thats stationary with current flowing, it needs to be moving to cool. it "blows"

with a 300rms sub you can run the comfortably to its limit without the amp clipping, and i know, id bet money, those JBLs in the right box, will take miles more than 300rms

tbh you could blow any equipment in any setup if you set it up badly
 
Matt82 said:
a 250rms sub, if you run it with 200rms you are far more likely to run the pair to the limit of the amp, which leads to clipping, where signals going to the coil end up flat lining... you get a cone thats stationary with current flowing, it needs to be moving to cool. it "blows"
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I don't think you understand clipping. When you get to the limit of the amp, it can't accuratly reproduce the input signal, so instead of setting louder, the top of the signal will be 'clipped', i.e. the top will be cut off. Look at the spectrogram here : http://en.wikipedia.org/wiki/Clipping_(audio)

The signal is still reversing, so the speaker is still moving, but is is only moving between two extremes (it still cools!). The effect of clipping is to introduce additional frequencies in the signal (you can get them by doing a Fourier transform of the clipped signal), which is perceived as distortion.

If you turn your amp up and nothing moves, there's either some 'safety feature' somewhere dumping the signal, or something's not working right. Clipping is used in ALL audio distortion effects, rock and roll will disagree with you if you think it stops all sound!
 
He's still right to say that underpowering a speaker is more likely to destroy it than overpowering it (within reason).

Too much power is far better than too little.
 
You're right that it can, but only if the amp is pushed to cause distortion (It's not the lack of power that hurts it, it's the additional high frequencies that are introduced via clipping, speaker can respond to that, think that's what Matt82 meant, sorry for missing it!).

Ideally you want to get an amp with a power level you're happy with (that will give you the max volume you want WITHOUT pushing it into distortion), then get a speaker that can handle a bit more than that.

Guess really if you impedances match, just don;t let it distort for whatever reason and you won't break anything :)
 
death_looms said:
The signal is still reversing, so the speaker is still moving, but is is only moving between two extremes (it still cools!). The effect of clipping is to introduce additional frequencies in the signal (you can get them by doing a Fourier transform of the clipped signal), which is perceived as distortion.
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but the amplitude of the additional noise is far smaller than the amplitude of the original signal, so i simplified that down as zero, so it will still be cooling, but nowhere near enough, hence it blows.

all in all, get a bigger amp and set up the gains properly. if you cant, get someone else to do it who can.

in fact, if you play a full range sound (ie music) through a sub (for example) there are freqs that it cannot audiably produce at all

oh, and MP3s, love the distortion on those
 
The additional noise is a of a higher frequency. Regardless of amplitude, the sub cannot respond to it because it's too heavy. Same effect though.

All you're doing by setting gains on a bigger amp is making sure you can push enough power to the sub to keep you happy without pushing the amp into distortion. I'd still want a speaker that can handle the max power.

I never worry about mp3's in the car, it's a crap place for listening to music. In the house though, that's where I spend my money :)

Think I'm gonna agree with you about getting a bigger amp for the car now, just don't let it distort (from any source)!I'll keep mega speakers in my valve amps though :)
 
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