19Cutlass94 Posted June 19, 2011 Report Share Posted June 19, 2011 I ohm tested my DVC subs today, and three were 3.8ohms, and one was 4.3ohms. I know its not good, but how bad is it? When it was wired up, it measured 1.0ohms... Quote Link to comment Share on other sites More sharing options...
92EuroScott Posted June 19, 2011 Report Share Posted June 19, 2011 (edited) I've heard of some DVC subs being a little bit off, from what they are rated at, with that little of a difference I don't think it would be a problem. Edit: I think if they were blown they would read lower than 1 ohm. Edited June 19, 2011 by 92EuroScott Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 19, 2011 Report Share Posted June 19, 2011 I've heard of some DVC subs being a little bit off, from what they are rated at, with that little of a difference I don't think it would be a problem. Edit: I think if they were blown they would read lower than 1 ohm. I've never seen anyone "blow" a voice coil. A basic understanding of how subs would prove that its not exactly possible. The coil wire gauge is thick enough to where you'd have other problems. Individual voice coil readings are unimportant unless they're really far off as mentioned above, and they will vary. What is more important is the final impedance as both coils are used for that. Your readings are normal. High quality subs usually have a higher tolerance spec, but what you have isn't terrible. So long as you don't hear any rubbing or scratching, you should be fine. Sent from my HTC Awesome using Tapatalk Quote Link to comment Share on other sites More sharing options...
BXX Posted June 20, 2011 Report Share Posted June 20, 2011 You've never seen anyone blow a coil? you need to get out more. The term blow does a good job of referring to a coil that has melted down and/or burnt the VC wire apart, ending up with an open coil. hell, ive done it. Then again 1000wrms through a little Kicker C12 will do that. I was bored with a free sub that I didnt want one night:lol: Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted June 20, 2011 Author Report Share Posted June 20, 2011 I always thought there was a difference between blowing one and melting one Ive got about 1300wrms going to two 12"s and I thought I might have messed something up at the last SPL comp I was at. Quote Link to comment Share on other sites More sharing options...
BXX Posted June 20, 2011 Report Share Posted June 20, 2011 To me, its just a generic term to use when its not proper to say I completey fucked up my sub:lol: Oh I wish I had some junk in mah trunk, but im loosing my nice headunit soon, going in my fiance's Kia. Plus im too cheap for car audio these days. Quote Link to comment Share on other sites More sharing options...
virtuetovice Posted June 20, 2011 Report Share Posted June 20, 2011 I'd say it's just fine unless you're really noticing poor performance. For the record though, it is absolutely possible to blow a coil. Like BXX, I have been bored with free speakers and WAY too many watts. Anyone ever seen a coil shoot straight out of a 6x9??? Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 20, 2011 Report Share Posted June 20, 2011 (edited) You've never seen anyone blow a coil? you need to get out more. The term blow does a good job of referring to a coil that has melted down and/or burnt the VC wire apart, ending up with an open coil. hell, ive done it. Then again 1000wrms through a little Kicker C12 will do that. I was bored with a free sub that I didnt want one night:lol: I'd say it's just fine unless you're really noticing poor performance. For the record though, it is absolutely possible to blow a coil. Like BXX, I have been bored with free speakers and WAY too many watts. Anyone ever seen a coil shoot straight out of a 6x9??? Ok, I'd like to at least *attempt* to stay relevant to the thread. A coil that measures a similar impedance and doesn't make an abnormal noise is not blown. No, I've never seen a melted coil because I've never destroyed one. I have seen a coil separate and make a big mess of things, but people who realize that you need more subs and more cone area and a better designed box to get more output don't exactly try to get that output by giving a sub too much power. As a rule of thumb you gain 3db every time you double power to a sub. If your sub can take 500W and you give it 800W and break something, I don't feel sorry for you by risking damaging your sub for that nearly inaudible 2db increase. I currently have two 250W RMS SQ subs running off of a 1000W amp and I know exactly where my gains need to be so I don't break something. I also use subs with very well vented motor structures that prevent that overheating. Edited June 20, 2011 by xtremerevolution Quote Link to comment Share on other sites More sharing options...
Addicted2bass Posted June 20, 2011 Report Share Posted June 20, 2011 Your subs are fine. The Ohms you listed are well within where they are supposed to be. Rarely are any speakers exactly 4 ohm. If you had a bad voice coil it would read 0 ohm or some crazy number not even close to 4 ohm. I see smoked down voice coils at my work all the time. The best is when it is in a sealed box and the smoke all comes out when you remove the sub:lol: Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 21, 2011 Report Share Posted June 21, 2011 Your subs are fine. The Ohms you listed are well within where they are supposed to be. Rarely are any speakers exactly 4 ohm. If you had a bad voice coil it would read 0 ohm or some crazy number not even close to 4 ohm. I see smoked down voice coils at my work all the time. The best is when it is in a sealed box and the smoke all comes out when you remove the sub:lol: Ah, yeah its a little more likely to burn a coil in a sealed box. Not only does the box not vent heat, but it also controls excursion so you can give a sub a whole lot more power before it bottoms out, heating up the coil like crazy in the process. Quote Link to comment Share on other sites More sharing options...
Addicted2bass Posted June 21, 2011 Report Share Posted June 21, 2011 Almost every sub that comes in with fried voice coil(s) is due to the amp gain, bass boost, etc. being cranked way up. Everytime we do a install i tell the customer not to touch any settings on the amp, but sometimes they don't listen. Quote Link to comment Share on other sites More sharing options...
19Cutlass94 Posted June 22, 2011 Author Report Share Posted June 22, 2011 I know in the last SPL comp, I turned the gain out probably a touch more than I should have, but was not even close to all the way up. I never use bass boost, and its in a vented boxed. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 22, 2011 Report Share Posted June 22, 2011 I know in the last SPL comp, I turned the gain out probably a touch more than I should have, but was not even close to all the way up. I never use bass boost, and its in a vented boxed. The following would explain why this is happening: 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. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 22, 2011 Report Share Posted June 22, 2011 I know in the last SPL comp, I turned the gain out probably a touch more than I should have, but was not even close to all the way up. I never use bass boost, and its in a vented boxed. The following would explain why this is happening: 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. Quote Link to comment Share on other sites More sharing options...
RobertISaar Posted June 22, 2011 Report Share Posted June 22, 2011 peaks and averages, gotta love audio tech. Quote Link to comment Share on other sites More sharing options...
Garrett Powered Posted June 22, 2011 Report Share Posted June 22, 2011 I reverse mounted my sub so it can radiate any heat off the motor structure easily. Quote Link to comment Share on other sites More sharing options...
xtremerevolution Posted June 23, 2011 Report Share Posted June 23, 2011 I reverse mounted my sub so it can radiate any heat off the motor structure easily. If you can afford the extra space, this is actually a very good idea. Sent from my HTC Awesome using Tapatalk Quote Link to comment Share on other sites More sharing options...
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