Speaker Wattage and Ohms

[crumpet19]

I've got a pair of 6x9 cerwin vega speakers that are rated...
minimum power rating: 60 watts @ 4ohms
Maximum power rating: 120 watts @ 4 ohms.

I want to push these speakers as hard as I can without damaging them.
I can't seem to find an amp with a 120 watt @ 4 ohm rating.

I have found a great deal on a pioneer amplifier that provides 150 watts x 2 Channels @ 4 ohms.
Would this kill the speakers if i kept the amp's gain setting turned down?

thanks,
christopher

 

[blahblah99]

Nope, just because an amp's rating is much higher than a the speaker rating doesn't mean you have to run it at that power. In fact, it's better to have an amp stronger than your speaker can handle for that extra headroom.

If this is car audio you are talking about, any amp over 100W @ 4 ohm will do well...

I have the CDT 6.5" eurosport components that are rated at 150W and I push them with only a 75W tube amplifier. It's much lower than the speaker rating, but it's 75W continuous power (and probably around 120-150W peak power, which many amplifier companies spec at).

 

[spidey07]

speaker power ratings have absolutely nothing to do with how much power they can take.

 

[sgtroyer]

What are talking about? That's exactly what the power rating means. What else would it mean?

 

[Fencer128]

Lets not confuse the valid RMS power ratings with the PMPO marketing gimmick.

Cheers,

Andy

 

[Smilin]

Originally posted by: spidey07
speaker power ratings have absolutely nothing to do with how much power they can take.

You're going to need more than just one sentance if dropping a comment like that.

 

[Smilin]

It is better to have a more powerful amp. Those speakers should handle 120watts of "clean" power. Depending on the fine print, that 150 watt amp should put out somewhere between 75-125 of clean power. Anything above that and it will start clipping - and even 500watt speakers wont withstand that.

 

[spidey07]

Originally posted by: Smilin

Originally posted by: spidey07
speaker power ratings have absolutely nothing to do with how much power they can take.

You're going to need more than just one sentance if dropping a comment like that.

Ok - power measured in watts and since this is alternating current that measurement shall be RMS.

So a speaker states a power handling of "150 watts". That is completely meaningless. 150 watts at what frequency?

That being said a speaker is nothing more than a motor and that motor has limits. It can only physically travel so much before reaching a point where more power just becomes heat and not movement of the driver. So most speakers can handle loads of power until they melt.

Now I can blow a "150 watt speaker" with a 10 watt amp. All I have to do is overdrive the 10 watt amp to produce a severely clipped output resembling a sine-wave with the peaks flattened and that will overheat the voicecoil and cause it to melt.

Or I can take a 1000 watt amplifier and drive the speaker to its mechanical limits without blowing it. Perhaps severely over-extending it slapping it into the magnet or breaking the spider...but that is a mechanical failure and not an electrical one.

Either way, it is common knowledge that power ratings on speakers are meaningless. You can really never have too much power, but most of the times folks don't have near enough to achieve the volumes they're looking for.

 

[f95toli]

I do agree with most of what you are saying but it is nor true that the power handling rating is meaningless. 150 W is 150 W at 25 Hz and 20000 Hz, the frequencie does not matter.
Most "normal" stereos would clip before that and the clipping would destroy the speaker but is you have speaker rated at 40W and drive it with a 200 W power-amp you could have a problem.
The maximum power rating basically tells you how much power the speaker can handle before it melts, assuming you have NOT destroyed the woofer beacause of mechanical failure before that the tweeter will overheat.

This rating is usually only interesting for big PA-systems where you use huge power amps.

 

[Brie]

Originally posted by: f95toli
I do agree with most of what you are saying but it is nor true that the power handling rating is meaningless. 150 W is 150 W at 25 Hz and 20000 Hz, the frequencie does not matter.
Most "normal" stereos would clip before that and the clipping would destroy the speaker but is you have speaker rated at 40W and drive it with a 200 W power-amp you could have a problem.
The maximum power rating basically tells you how much power the speaker can handle before it melts, assuming you have NOT destroyed the woofer beacause of mechanical failure before that the tweeter will overheat.

This rating is usually only interesting for big PA-systems where you use huge power amps.

I disagee that wattage does not change with frequency. Speakers had different impedances at different frequencies. If the impedance is changing then the power has to be changing with the frequency. In addition if you are using a 200W amp to drive a 40W speaker. Just dont turn the gain up so you dont blow the speaker. Im sure that if you get anywhere near that 200W output you will hear the effect.

 

[f95toli]

I agree with you about the impedance, but in "normal" music the frequencis change all the time so the "average" impedance is usually fairly close to 4 or 8 ohms.

 

[kpb]

Originally posted by: spidey07
Now I can blow a "150 watt speaker" with a 10 watt amp. All I have to do is overdrive the 10 watt amp to produce a severely clipped output resembling a sine-wave with the peaks flattened and that will overheat the voicecoil and cause it to melt.

Common misconseption but not true.

There are really only a couple ways you can blow a speaker.

You can drive it beyond it's physical limits which certainly isn't possible with an amp rated so far under the capabilities of the speaker. A 10 watt amp simply could not drive a 150 watt speaker to physicially damage it.

The next way to do it would be by melting the voice coil which is what most people claim will happen with a clipped signal. This is indeed not true. The amount of power included in a wave form is equal to the area under that wave form on a graph. If you take and compair a sine wave to a square wave which is your theoretical max clipping the area under the curve is less than double it. So a fully clipped 10 watt amp is going to be putting out less power than a 20 watt non clipped amp. There is no way that this will overheart the voice coil of a properly designed speaker. The one unusual case where you could overheat a voice coil is in ported sub boxes. If you hit the right frequency you end up with the sub speaker not moving at all and noticebly decreasing the cooling for the voice coil since it isn't moving at all.

As far as clipping goes it's actually really pretty common in car audio for a variety of reason. Often times people tune there system at lower volumes so at higher or max volumes they are clipping. Also some people intentionally clip there systems. A certain amount of clipping is not recognizable by people and by clipping the signal some you get more power out of your amps.

For the original poster the pioneer amp would probably be just fine with the speakers you've mentioned. Just curious but what does your system currently look like and where are the 6x9 cerwin's going to be mounted?

 

[crumpet19]

My current system consists of:

Aiawa CDC-MP3 head unit.
2 X 5.6" Cerwin-Vega 2 way speakers mounted in the front dash -powered off of head.
2 X 6.5" Cerwin-Vega 2 way speakers mounted on the rear deck -powered off of head.
2 X 6X9" Cerwin-Vega 3 way speakers mounted in boxes in trunk - I need a bloody amp.

I know 6x9s aren't best suited for mounting in boxes... but, the car is an '89 chevy corsica so there aren't a lot of options. This being said.. my car is actually a hatch back.. so sticking them in the trunk and focusing them to reflect off of the back glass actually sounds quite nice.

 

[kpb]

I'd really recommend against that setup. 3 way 6x9's aren't going to be designed for the type of thing your using them for. Even a single 8' in a proper box would get your better sounding results. Also you probably want to make sure you have some sort of cross over in there at some point. Alot of amps have them built in today but thats probably something you want to consider when your looking at amps. Things work alot better when your only amplifying and sending the frequencies the speaker is designed to handle. Do you already have the 6x9's or where you still in the planning phase? Happen to have a link to the amp your looking into?

 

[spidey07]

kpb,

I understand your reasoning and explination but I have blown over two dozen speakers in my time and most all were from clipping. There were a few woofers that literally blew the voice coil out of the speaker but that was from overdriving. If you like do the experiment yourself with a underpowered amp and serverely clip it...

 

[crumpet19]

Don't get me wrong.. I'm not using the 6x9s for bass... I'm using them for all around tone.
I'd like to get an amp that has low/full/high frequency settings. My Rockford Fosgate amp that I had featured such settings and the speakers worked really well on the "full" setting. I don't want my car to bump or rumble or any of that sh^t. So, they are perfect for how I intend to use them aside from the fact that they are mounted in boxes. Regardless of what you may think, they sound awesome. I have run this exact setup for almost 5 years now and have been told by many people that I have a very balanced, very crisp sounding stereo in my car.

The only reason for my posting this thread is because I need to purchase a new amp.
My Rockford no longer powers up. I've tested power from the battery and remote wire. I've rechecked all of the cableing and reseated all of the connections. I've had this amp RMAd twice and it has been very problematic.

 

[LED]

The Amp should be fine and most Speakers are usually blown by distortion and clipping even @ minimum watts (yes even 1/10th their rate), not power as most quality 1's (Cerwin Included) can handle more then their rated value which are usually measured in Continuous or RMS Power.