Slightly underpowered?
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New member Username: AdgoodmaBoulder, CO United States Post Number: 1 Registered: Feb-06 | i got a pair of focal 570cv1's for the front of my truck. now that i look closely- the nominal power is 60w, max power 120. my kenwood head unit only does 4x 50watts. will this damage the speakers? or will i just not get top quality out of them unless i use a seperate amp? |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 10953 Registered: Dec-03 | your kenwood is actually about 15 watts x 4 RMS. if you want those focals to really sing, put a 50 watt RMS per channel at 4 ohm amplifier on them. what will damage your speakers is clipping from the dinky amp in that head unit if you turn the bass up or turn the volume up too far. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 531 Registered: Mar-04 | I disagree. Even if that HU is 20w and can produce 40w when clipped all to hell there's no reason 40w of power - clipped or unclipped - should damage those speakers. It will just sound awful. Definitely look into getting an amp though. You've got nice spkrs, but you won't get your money's worth unless you get them the power they need. |
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New member Username: AdgoodmaBoulder, CO United States Post Number: 2 Registered: Feb-06 | Thanks for the posts... The head unit says it does 200W max power? that doesn't mean 50x4? I also have a pair of infinity 1101t tweeters up front, i dont know how they are hooked up, opinions? If i was to get an amp i would want to hook it up Tri-Way so i could also power a small sub in the back. Suggestions? |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 799 Registered: Oct-04 | I don't see how you've come to the conclusion, Optidriven, that clipping isn't going to ruin speakers. Adam, for the most part, just ignore "Max" ratings all together. You're looking for RMS or continuous power ratings. Are these Focals component speakers or just coaxials? Either way, you could still run the tweeters up front off the HU if you wanted to, after you hooked up the amp, but I'd imagine you'd get better SQ with just the Focals running up front. Running a 3 channel amp would work, like a 75Wx2, + whatever you need on the 3rd channel for your sub. |
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New member Username: AdgoodmaBoulder, CO United States Post Number: 3 Registered: Feb-06 | so do you guys agree that it would be better to just buy an amp such as 'Rockford Fosgate Punch 4004' instead of the tweeters? The guy at cruchfield said that i only needed 50w rms x4 and 200w rms x2 for a sub i might put in later... -the focals are coaxials- |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 10959 Registered: Dec-03 | yes. get the amp. yes only use RMS power ratings. max power ratings are nonsense, and have no real merit. They're only used to sound impressive to the uninformed buyer. Opti, clipping and distortion cause not only heat build up in the coils, but also non-linearity which causes mechanical damage to the coils by scraping them along the magnet till they unravel or until the wire insulation wears through and causes a dead short, and when the latter happens, you blow the amplifier as well. Disagree if you believe I'm mistaken, but I've had to replace my share of customers' speakers after this has happened, even running on some skimpy head unit for power. Once you open the speaker up and see the voice coil windings pop out of the motor like party streamers when the cone was completely frozen, it's not difficult to see what happened.  |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 10961 Registered: Dec-03 | PS Adam, the guy at crutchfield for once was right.. but remember he's talking RMS power, not peak, max, PMPO, or "music power" RMS is an average or constant power delivery rating, and a more consistant way to discuss power in amplifiers. Groups like CEA have rating guidelines to specifically make RMS power ratings a standard that you can compare between any two amplifiers accurately in fact. This is one reason I prefer new amplifiers that are CEA2006 certified/rated. head units are never 50x4 RMS though.. they're usually between 15 and 25 watts RMS per channel, and they lack the clarity, dynamic range, and overall abilities of a decent 2 or 4 channel amplifier, even at 50 watts RMS per channel from the amp, which keeps it small and easily installable. |
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New member Username: AdgoodmaBoulder, CO United States Post Number: 4 Registered: Feb-06 | ok i am almost sold.. two more questions. the focals are 60RMS, don;t i need an amp that can do at least 60w rms in 2 of the channels? i dont think i need more than 200 for the kind of sub i am looking for... this one says it does 50w rms and 200w rms http://www.crutchfield.com/S-x94YJvNe9rM/cgi-bin/ProdView.asp?I=575P4004&id=revi ew&search=rockford+4004#Tab secondly, i believe the jury is still out on whether my kenwood HU is wrecking these speakers right now at normal volume. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 534 Registered: Mar-04 | Jake - clipping doesn't damage speakers - power does. A 50w amp clipped to the fullest extent should never damage a 200w speaker, and would theoretically require an extended period of time to damage a 100w speaker. Mechanical damge is typically limited to environmental wear, or physically pressing the cone to the point of damage. Glass I certainly don't have the experience in the industry you do, but I think it would be reasonable to suggest these spkrs you had problems with were poorly designed and didn't allow sufficient clearance of the coil through the mag gap. The physical attachment of the cone to the surround/frame and the coil to the spider should keep the movement of the coil very linear. Originally posted by msmith: The only thing that thermally damages speakers is power... more specifically: average power over time. I'll explain... If you take a given amplifier, let's say 100 watts and operate it just below clipping with music material, the "Crest Factor" of the amplifier's output is equivalent to the "Crest Factor" of the program material. "Crest Factor" is the difference between the average level of the signal and its peak level. For example, a pure sine wave has a "crest factor" of 3dB, meaning that it's peak level is 3dB higher than its average level. We all know that 3dB represents a power factor of 2, so another way to look at it is that the peak power of the signal is twice that of its average level. So, if we play a sine wave on our 100 watt amplifier, just below its clipping level, the average power (over time) the speaker is needing to dissipate is 50 watts. A true square wave, by comparison, has a crest factor of 0db, so it has equal average and peak power. Our 100 watt amplifier, playing a square wave, unclipped, into our speaker requires that the speaker dissipates 100 watts of power (twice the heat as a sine wave). Music has a significantly higher crest factor than sine waves or square waves. A highly dynamic recording (Sheffield Lab, Chesky, etc.) typically has a crest factor of 20dB or more, meaning that its average power is 100 times lower than its peak power. So, if we play our 100 watt amplifier just below clipping with the typical audiophile recording our speaker is only needing to dissipate 1 watt of average power over time. Modern commercial recordings typically exhibit crest factors of around 10dB, meaning that the average power is 10 times lower than the peak power. So, our 100 watt amp just below clipping would deliver an average power over time of 10 watts that the speaker has to dissipate. Okay, so what happens when we clip the amplifier (which we all do at times). When the amplifier enters into clipping, the peak power no longer increases, but here's the KEY... THE AVERAGE POWER CONTINUES TO INCREASE. We can often tolerate a fair amount of clipping... as much as 10 dB or more above clipping with a reasonably dynamic recording... a bit less with a compressed commercial recording. So, if we turn the volume up 10dB higher than the clipping level with our Sheffield Lab recording, we have now reduced the crest factor of the signal reaching the speakers by 10dB... so instead of needing to dissipate 1 watt average, we are asking the speaker to dissipate 10 watts average, and we're probably ok. If we turn up the volume 6dB past clipping on a compressed commercial recording (or bass music recording), we have taken the crest factor of the signal from a starting point of 10dB to only 4dB, asking the speaker to dissipate an average power of 40 watts instead of 10 watts... that's FOUR TIMES the average power, which generates four times the heat. SO, in most cases, the reason clipping can damage a speaker really has nothing to do with anything other than an increase in average power over time. It's really not the shape of the wave or distortion... it's simply more power over time. When someone plays Bass Mekanik clean (unclipped) on a 1000 watt amplifier the average power is 100 watts (10dB crest factor). You can also make 100 watts average with Bass Mekanik by heavily clipping a 200 watt amplifier. If someone is blowing a woofer with 200 watts of power due to a lack of restraint with the volume control... they will blow it even faster with a 1000 watt amplifier because they will probably turn it up even more and now they have more power to play with... this is the recipe for aroma of voice coil. When woofers are rated for power, an unclipped signal is assumed. We use test signal with a crest factor of 6dB for power testing and can run a speaker at its rated power for hours and hours on end without thermal or mechanical failure. For example, a W1v2 can dissipate 150 watts average power for eight hours or more with signal peaks of 600 watts. So, we rate the speaker for 150W continuous power. This way, when a customer needs to choose an amp for it, they will hopefully choose one that can make about 150 W clean power... Even if they clip the bejeezus out of that amplifier, it is unlikely that the speaker will fail thermally. This is a conservative method, but it needs to account for the high cabin temperatures in a car (think Arizona in the summer) which significantly impacts heat dissipation in the speaker. A top plate that starts at 150 degrees F is not as effective at removing heat as one that starts at 72 degrees F in the lab... and this affects the ramp up of heat in the coil. DISCLAIMER: The frequency components of clipping can affect tweeters due to their low inductance and lack of low-pass filtering. Clipping essentially raises the average power of high frequencies to a point that can damage tweeters... Woofers and midranges couldn't care less about these high frequency components because their filtering and/or inherent inductance knocks that stuff out of the picture. Best regards, Manville Smith JL Audio, Inc. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 535 Registered: Mar-04 | The 4004 should work perfectly for you Adam. A good speaker doesn't require you to have exactly rated power to get excellent results. 60w is just the point where performance of the spkr vs. its ability to dissipate power (heat) are optimal. At any power beyond that the resulting heat outweighs the benifit in sound. As you've noticed - they'll run just fine with only HU power - they just won't play very loud. You could use 30w with better results and still not stress the speaker. 40w better yet, 50 better yet 60, 70, even 80 would be fine. You just have to realize once you exceed the rms rating your chances of causing thermal damage to the speakers increase. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 10978 Registered: Dec-03 | as noted above, power ratings on speakers are thermal limits, not an indication of the power required for the speaker to operate optimally. 50 watts per channel cof most components is plenty of good clean power. |
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Silver Member Username: Robert_dMIA, FL USA Post Number: 469 Registered: Sep-05 | wow glass what happened to you havnt seen you in a while |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 804 Registered: Oct-04 | So clipping just adds more heat to the VCs? I was under the impression that clipping sends DC instead of AC power to your subs and that's what destroyed coils. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 544 Registered: Mar-04 | on a scope a badly clipped wave starts to resemble DC - actually it starts to look like a square wave, but it's not the waveform that damages speakers. It's the power. this one goes way off track, but there's one very informative post - |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 545 Registered: Mar-04 | you'll have to copy/paste |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 10990 Registered: Dec-03 | Jake, clipping is sending DC voltage across the coils. that DC voltage prevents the speaker from moving back and forth, so instead of the heat dissipating, it builds up on the stationary coils at their peaks. That heat build-up as DC voltage is equal to much higher voltages from an AC source, in regrds to heat.. that's why 10 watts DC is like 100 watts AC to a speaker, thus the damage from heat. it burns up the coil, turning it into a heating element basically. I'm still around, just been busy. I don't always have time to keep up with this place, it's so busy here. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 547 Registered: Mar-04 | GW - a clipped sine wave isn't dc voltage, and it's not a matter of the movement of the coil, it's the power from the clipped wave. [QUOTE]Originally posted by Rob M: [QB]As far as damaging speakers, it's just the extra power with the amp putting out more voltage longer when clipping rather than "DC." A speaker doesn't care about clipping; it's still moving and getting cooled with even a clipped wave. And since the speaker is a low-pass filter, it can't respond immediately to the sharp corner in the clipped output of the amplifier so it just keeps moving and doesn't "hang up." [/QB][/QUOTE] |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 805 Registered: Oct-04 | So by those posts, it's perfectly OK to put a 100W amp at full clipping (should be 400W according to that post) on a 400W sub. There'll be a lot of distortion but there'll be no damage to the sub. Is that correct? |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 806 Registered: Oct-04 | That's to anyone with an opinion on it. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 555 Registered: Mar-04 | A 100w rms amp would theoretically be capable of 200w fully clipped - where did you get 400? Assuming you have a good quality 200w speaker, then no, a 100w amp clipped to the fullest shouldn't damage it. Besides, you'd either have to be completely deaf, or a completely retarded to run an amp fully clipped. 50% would be severe, and sound awful. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11003 Registered: Dec-03 | opti, a clipped signal is a square wave at the peak and trough, which translates to DC voltage. that voltage equates to heat. the speaker may continue to move due to momentum, but it still reacts to the clipped signal. I don't give a f**k what anybody else says, clipping will still kill your speakers. if you want to go clip the sh*t out of your amplifiers, go right ahead. I'm done with this thread. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 557 Registered: Mar-04 | So what you're saying is...if I get myself a $50 100x2 Pyramid amp - bridge it, connect it to, let's say a CVR 12" dvc2 at 4 ohms, and crank the gain and clip that amp for everything it's worth...that sub's gonna blow? You KNOW that's BS. A speaker doesn't care whether it's playing music, sine waves, triangular waves or square waves - they feel POWER, and too much is bad. Do this experiment - I'm sure you have the means. Go find a run-of-the-mill sub - 300w or so. Hook it up to a hu or a budget cheap-o amp in such a way that the amp is clipping all to hell and watch that sub run for days. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11017 Registered: Dec-03 | I don't need to. I've spent fifteen years replacing subs for customers who burned up their coils on underpowered amplifiers due to having the gain set to full, trying to compensate for a cheap, weak amplifier because they were too cheap to buy an amp big enough for their needs. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11019 Registered: Dec-03 | http://www.bcae1.com/2ltlpwr.htm for reference to clipped signals and driver damage. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 562 Registered: Mar-04 | And I'm baffled that you don't see Perry's, or my point. It's the POWER FROM the clipping that is the issue, not the clipping itself. Clip a low power amp on a high power speaker and it will play for weeks - months. If it fails, it was a poorly designed speaker. Clip a high power amp on an equal power speaker - of course that's going to be trouble. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11039 Registered: Dec-03 | I never disputed that. the clipped power would still have to excede the thermal ratings of the coils, excluding mechanical damage, but over time, the mechanical damage will take it's toll, and in most cases, people are sending enough power with a clipped signal to do damage. I'm still not really sure what we're arguing about here. |
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Gold Member Username: Kd7nfrMontpelier, ID United States Post Number: 1456 Registered: Apr-05 | You're retarded if you're arguing ith GlassWolf. Especially over something that almost everyone knows is true. If you're gains aren't set right, and you're clipping the amp, you're going to ruin you're speaker/sub... |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11046 Registered: Dec-03 | I think we both pretty much agree.. I think we just got off track with miscommunication. clipping still requires enough power to cause damage. if the clipped power doubles and still only makes 5 watts clipped on a 500 watt speaker, you're not going to do any damage.. but the fact is amplifiers produce enough power even without clippng, that when they do clip, you're usually looking at damage.. and I see a lot of people use head units with 15 watts on door speakers, with volume at full and bas cranked up, sending a nearly pure square wave to the speakerss.. so with that much clipping, on smaller speakers only deisgned to handly say 30-60 warrs, you can again do damage.. anyway I think this was just miscommunication. no harm, no foul. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 563 Registered: Mar-04 | Jake, it's comments like that got this whole discussion started. It's like saying gravity kills. The fact is - Falling out of a plane kills. Falling out of your chair - not so much. GW --  |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11059 Registered: Dec-03 | it's not the fall that kills ya.. it's that sudden stop at the end :D |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 807 Registered: Oct-04 | Ok, so DC voltage creates more heat then AC. That combined with the cone not moving correctly creates a huge heat build-up. How is the speaker mechanically damaged from the clipping? |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11077 Registered: Dec-03 | the voice coil is a ceramic tube wound with wire around the outside. the wire is insulated so it doesn't touch itself electrically. the coil sits inside the motor assembly which is a bit magnet with a plate on the end. the coil moves back and forth inside the magnet as the direction of current flow changes back and forth. when the amp clips and the peak of the (square) wave (DC portion) traverses the coils, the speaker extends to it's peak travel and stays there instead of snapping right back and going the other direction. When that happens, the coil can "cant" or tint a bit, and lose linearity.. and as the moving mass does return in the other direction, in a non linear manner, the coil winding is scraped along the inside of the magnet structure, and the insulation on the wire is frayed or worn away until you get a dead short or a broken wire.. which fries the sub. that's about the best I can explain it without drawings. |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 808 Registered: Oct-04 | Ah ok I understand. So basically the coil moves back and forth but is suspended from touching anything. But when clipping occurs, its movement is no longer straight and it goes up/down and side to side. Does the clipping make the movement non linear because of vibration? Also, I really appreciate you taking your time to explain this to me and the rest of the forum! |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11091 Registered: Dec-03 | well, remember that tube the wire is wound around (the voice coil) is attached to the speaker's cone under the dest cap in the center. I forgot to mention that. When the speaker is at the peak of the clipped wave, it's held in an extended position momentarily, and it's hard to keep something like that perfectly straight when it's being forced to stay extended that way instead of acting like a spring and just moving back and forth freely. The tilting of the coil is pretty much caused by the fact that nothing is really "perfect" so it'll never be perfectly linear or balanced all the way around.. and the speaker will lean to whichever side it has the least resistance to do so. it's like trying to push the cone in on a sub with your fingers.. no matter how careful you age, most times you'll hear or feel the coils scrape just the slightest bit, because it's very difficult to push the cone with perfectly equal pressue on all sides, with your fingers. remember tolerances in a speaker are relatively small, so it doesn't take much of a non linear angle or non perpendicular angle for the coil to rub along the motor. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11092 Registered: Dec-03 | this link has some pictures that may help visualize things: http://www.team-bio.com/RE_rebuild.htm |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 809 Registered: Oct-04 | So the voice coil slides on the metal thing in the middle there (motor?). The actual wiring is on the outside of the VC, not the inside of the tube, so what does the wire rub on, the outside part of the motor? http://www.team-bio.com/images/RE_Rebuild/6-coilcentered.jpg |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 810 Registered: Oct-04 | Oh, the voice coil sits in the little opening of the motor, I get it. http://www.team-bio.com/images/RE_Rebuild/3-attachbasket-2.jpg |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11109 Registered: Dec-03 | coil wire is wound around the voice coil "form" that's attached to the backside of the speaker cone. the coil and form sit inside the opening in the center of the magnet structure. when the coil moves, it can rub on the edge of that opening in the magnet in which it resides. you can't see any of it on an assembled speaker because the top side of teh coil is protected by the spider and dust cap, and the back side by the pole plate. |
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Silver Member Username: SolacedagonyNew Jersey US Post Number: 813 Registered: Oct-04 | Yea ok, so when people say "voice coil former", they're referring to the tube that the coil is wrapped around? Thanks, this has been very educational for me. |
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Silver Member Username: N2audioLawrence, Ks USA Post Number: 581 Registered: Mar-04 | http://www.bcae1.com/speaker.htm |
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Bronze Member Username: LewassBloomfield Hills, MI USA Post Number: 61 Registered: Jan-06 | Hey guys I think I just learned more from this thread than from all the others I've read put together. Thanks Opti for challenging GW because it got him to take the time to explain all this in great detail And thanks Glasswolf, for sharing your knowledge with all of us. Sometimes forums can be such a waste of time. Thanks for proving that one good thread makes up for all the time wasted reading all those volumes of uneducational bullsh*t. |
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Platinum Member Username: GlasswolfWisteria, Lane USA Post Number: 11143 Registered: Dec-03 | and every once in a while there's a thread I like responding to :P |
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Bronze Member Username: AdgoodmaBoulder, CO United States Post Number: 20 Registered: Feb-06 | well, you guys shouldbe happy to know that my original question wasn't really answered until i went out an bought an amp for the focals.... so they are 'slightly underpowered' no more |
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