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Discussion Starter · #1 ·
My first post on here. Great site.

I'm totally addicted but still learning

Wondering about matching RMS on your amp to subs.

I see a lot of variance with this topic. For example - giving a Focal Utopia 27WX 900W of Audison power when it has an RMS of 250W. I see it a lot where regardless of sub RMS .. Just throw a 1000W at it.

*How do you really know how much juice to feed these higher end subs?* Is there a more technical method?

I am looking to upgrade amps/sub. I am considering Morel Ultimo or Utopia. For amps - Arc or Zapco, Focal FPS

Have a simple set up now:

Nak cd400
AudioControl THREE.2
Focal 165VR3
IDMAX 10D4
Focal solid amps

Thanks fellas
 

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a good rule of thumb is to have 2-3x more power available to a driver than its rated for. the reasoning for this is for musical peaks.
More importantly imo you have almost no chance of clipping an amp before your drivers start giving out.
You'd be surprised how much more power a good driver can handle over what its rated for; especially if you're feeding it clean power!

Substages especially can benefit from way more power. a good demo of this is eagles - hotel california off of hell freezes over. theres a bass drum note in there that a lot of "loud" systems can't recreate worth a damn because they're clipping so badly at their loudest that the sound is lost. Listen to that same song in an SQ car with a lot of amplifier overhead on the substage and you'll be amazed!
 

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I beleive these are the specs for the Focal Utopia 27WX sub:

- 27cm (11") subwoofer for bass reflex enclosure.
- 65mm (2-1/2") v.coil
- multi-magnet 12x60mm (12x2-3/8").
- Max. power handling: 500W.
- Nominal, power handling: 250W.
- Sensitivity (2.8 V/1m): 90dB.
- Frequency response:
- 25Hz*-1.5kHz.

The Audison amp is more than suffice for your needs.
 

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Just because I give it 1k of power doesn't mean it will ever use it, just headroom.

If a sub says 600 RMS, usually means that is what it wants CONTINUOUSLY use without issue. Peaks would hit more around 800. So a good clean 1k amp is perfect for THIS example.

Robert Wrath hit the nail on the head. 250 CONTINUOUSLY. Peaks would hit 500. So a good 700 RMS amp is PERFECT. Just make sure you power the sub CORRECTLY, that means, set the gains right before clipping on the amp and on the speaker!
 

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^^ agree, im giving my g5 around 900w rms and its only rated at 450w rms
 

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Discussion Starter · #7 ·
Good comments. Interesting.

Would this theory bode well for the front stage as well? At this point, I have 75x2 going to the 80W RMS speakers.
 

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If I were you, I would try to get it up to 160 RMS just to be on the safe side but for general use that is perfect.

I just like to have extra power so when the song demands, I have it. Lets not forget, if you MAX the speakers right before clipping, the extra power would be needed, but for normal daily use, it isn't needed, but is nice.
 

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Imo RMS rating are overrated. I ran a 600WRMS sub on a 140wrms amp and it sounded good, reached Xmax anyway. In reality it might not that of huge difference, 150w-->300w-->600w equates to 6dB SPL increase. At normal listening levels you'll probably have enough headroom anyway as long you don't listen to sine waves. It's still better to have more power than less for reasons already stated in the thread, just pointing out that at 900W you'll need like 4kW to have any audiable SPL increase... Run two subs and gain 6dB increase, sub excursion goes down at same levels and therefore distortion, if I were you I'd have bought an additional sub of the same model and perhaps build another enclosure for them if you're unhappy about how they sound.
 

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additional sub *can* add 3, not 6. Some subs can play *fine* on lower power, but won't play optimally because everything needs a certain amount of power to operate at its peak.

We are not discussing increase in sound level, but the amount of power *needed* to to run the subwoofer * optimally*.
 

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That covers most of it, a few people just like to say they have X watts on whatever. The people who overpower do not clip the amp or it would likely trash the speaker. You don't want clipping for SQ it trashes the sound.

For example my pair of cheap pyle 15s IB had 500rms alpine on them. It worked well, if I really stood on them with piles of too much bass they would start to sound stressed and lose some bottom extension. This was at a point way too loud, far louder than the highs will go, it was just seeing what they would do. So I tried a 350rms alpine on them same model line amp. Now they sound the same but at the top of the volume knob they lose punch. The low bass is still there, the punch drops back (the peaks). So obviously I am clipping the amp on peaks. Yeah this is louder than I normally listen to, the SQ is great at any normal level it is just when I top it out. Going to put 500rms back in or similar, just for those days when I need it. Of course the other issue is when does it clip, with a sub it is hard to tell you just lose some clarity. With a larger amp you don't have to worry about it.
 

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speaker wattage is a THERMAL property. it means how much power the speaker can dissapate without melting.

having an amp that can produce more power is so that your amp is not stressed as well. if you had a car that maxed out at 65 mph, rolling on the highway would be hell on its internals running at 95-100% of their rated operating peramaters.

also, there are different dynamic peaks in music. some pars of a song are recorded soft and some parts have loud dynamic points like a guitar solo or drum hits. at these points the amplifier will generate more wattage and if those musical peaks push the amplifier past its operating peramaters its will clip the extremes of the waveform and you lose those dynamics.

so its an equipment longevity and a soud oriented issue. having more power on tap is always a good thing than whats required as long as you do not put too much thermal strain on your speakers or push the amp past its limits. ie = setting gains and knowing the systems limits.
 

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additional sub *can* add 3, not 6. Some subs can play *fine* on lower power, but won't play optimally because everything needs a certain amount of power to operate at its peak.

We are not discussing increase in sound level, but the amount of power *needed* to to run the subwoofer * optimally*.
Yeah, saw that now. Was a little quick to answer, but it is really 6dB you can add if pathlengths/phase are optimized with a second driver with 3dB increase in amp power draw.

Q21 - Why does SPL increase 6 dB for two drivers in parallel, when the electrical power consumed only increases by 3 dB?
Linkwitzlabs FAQ

decible increase by adding another sub - Home Theater Forum and Systems - HomeTheaterShack.com
 

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Discussion Starter · #15 ·
Oh yeah, sorry to all for posting to wrong forum. I've never joined a forum before so I'm figuring out all the rules n such.

Some knowledgable folks on here.
 
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