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Too Little Power


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willdkartunes 
Copper - Posts: 250
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Joined: February 01, 2006
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Posted: March 11, 2006 at 2:37 PM / IP Logged  

I mentioned my "damage" to the speaker in an earlier post on this thread. For the purposes of not having to go back and try to find it I will repeat it.

As I said before, I think this damage will occur regardless if you use a box or free air. I could be wrong, but I don't think the results would differ.

The damage that I noticed had to do with the sound quality of the subwoofer. It still thumped pretty good when it was put back on a higher wattage amplifier, but the lows didn't sound as hard hitting as before, and at certain frequencies, the subwoofer had what sounded like an internal "rattle". Almost as if the subwoofer was in the early stages of getting ready to blow. It still didn't sound terrible though, and to the untrained ear it would have probably gone unnoticed. Steven may be right, and this may be due to the fact that it was free air. There is really no way to be sure unless I was to do the test again....

Of course it will still be flawed using an enclosure due to the fact that the enclosure size must be changed when switching from 500watts to 60watts of power! I also am not going to keep wasting away JL 10w7's just to prove this theory!! Trust me when I say it isn't too great for the sub running at HIGH volume at such low wattage. Of course if you keep the volume low, then the low wattage doesn't matter and you will never have a problem.

Just incase this also becomes a problem with the volume thing... I've ran that 10w7 at 80% volume for over an hour and all it did was piss off the neighbors REAL badly. The subwoofer pounds at 500 watts of power and I'm sure it is capable of doing it all day at 80% volume. (if you can stand hearing the noise for that long! lol!)

Stevdart, Your right in saying that it is just an observation. But isn't that what the majority of us do in car audio though? We observe and test and then observe some more, until we think that we are satisfied with the results. I of course was satisfied, since for one it's probably not possible to blow a subwoofer running too little power. More importantly, who would want to run a 10w7 with a mere 60 watts?!

I guess people would take my word for it if I was say, an experienced scientist, who got really indepth in my responses basically losing everyone's interest and wasting everyone's precious time in reading the over-informative scientifical conclusions of a well calculated test. I'm not going to get that crazy about this information, I assumed that my observation would be enough to give you a little insight as to what happens.... If you don't trust my word, then try it out and see, as I have also stated before. If you don't trust me, then maybe you can trust yourself.

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: March 11, 2006 at 2:57 PM / IP Logged  

It's not about trust, I'm simply trying to get a handle on what you are describing and I suspect you are simply using terms inaccurately.

First off, almost all speakers are tested in "free air" without enclosures, so operating them this way will not by itself harm anything.  Loudspeaker ratings that rely on particular enclosures are highly suspect and tend to indicate a shoddy manufacturer... Overall system power handling capability can be altered by the enclosure, which may be where you are confused.  When you say "Of course it will still be flawed using an enclosure due to the fact that the enclosure size must be changed when switching from 500watts to 60watts of power!" I don't really know what you mean.  There is no reason related to raw speaker power handling capacity that would make your statement true, so I suspect you are referring to system power design?  If you are trying to create the most efficient system or most optimal response for a particular speaker using a 500 watt amplifier VS a 60 watt amplifier, then yes, enclosure size is a major factor.... but as far as the speaker's basic thermal ratings, these are determined with no enclosure at all so size is a moot point.  There is no reason that an enclosure size has to be different just because of amplifier size, as long as the speaker will handle the power.  Please let me know what you are trying to say...?

You keep using the terms "volume" and "power" as if they are separate things.  They are inextricably tied to one another.  In order to increase the "volume" of any system you must increase "power."  So again, perhaps I simply don't understand what you mean by your use of this terminology...?

If you feed a loudspeaker a distorted and/or clipped signal, it will sound bad, yes.  If you hear a rattling or other mechanical sound inside a speaker, it is likely damaged, possibly due to a part of the voice coil separated from the former.  This is most commonly caused by excessive heat.  A JL Audio 10W7 has a thermal power rating of 500 watts.  If you damaged the voice coil, this value may have been exceeded by your test setup or the speaker may have been defective.  Is it possible for an amplifier rated at "60 watts" to generate 500 watts of thermal energy in a loudspeaker?  Yes, depending on the amplifier.  "Power" that is being used in a loudspeaker and the "ratings" listed for an amplifier can be two entirely different things.

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: March 11, 2006 at 2:58 PM / IP Logged  

gbear14275 wrote:
I wasn't trying to be argumentative because I agree with the too much power thing.  But...if we are talking about the myth (too little power can destroy subs) their terms(as in the meaning of the word power when people use this statement) are that power is defined according to rated specs. 

Thanks.  Yep, the ratings on an amplifier and the power being delivered can be two entirely different things.

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gbear14275 
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Joined: May 09, 2005
Posted: March 11, 2006 at 3:39 PM / IP Logged  
Totally! 
stevdart 
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Location: Pennsylvania, United States
Posted: March 11, 2006 at 4:32 PM / IP Logged  

wildkartunes wrote:
But isn't that what the majority of us do in car audio though? We observe and test and then observe some more, until we think that we are satisfied with the results.

That's the truth.  I know that is all I can do! 

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
willdkartunes 
Copper - Posts: 250
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Joined: February 01, 2006
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Posted: March 12, 2006 at 5:32 PM / IP Logged  

DYohn,

I figured that since loudspeakers were tested under free air testing that I should use this method instead of using an enclosure. I was told by Steven Kephart that the reasons for my "speaker damage" were due to the fact that I tested the speaker in a free air environment and didn't use an enclosure... That would be the only reason why I started mentioning anything about an enclosure...

Sorry about the "volume" thing. I guess I should have stated that part a little clearer. I meant the volume control of the HU or any other type of source that could be used in place of the HU. In any case, you are correct, since turning up the volume of an HU is the same as an increase in "power". Sorry if I made it seem like they were seperate things. They really aren't.

For the question about switching the enclosure size going from 500 watts to 60 watts, yes, I was referring to the overall system power design. I was only stating that IF I was to use an enclosure, that it might probably be best to use efficiency to my advantage.

Your right about the difference in thermal energy running to the loudspeaker. That could be what hindered the experiment.  I would say that if anything did go "wrong" with the experiment, then this would be the culprit. This could be the cause, but I doubt it.

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: March 12, 2006 at 6:28 PM / IP Logged  

No need to apologize abut anything, man, I was only asking my question to clarify things so I could understand what you were trying to say.  Too Little Power - Page 4 -- posted image.

A couple of points:  Operating a loudspeaker at high power levels in free air with tones or music signals can be very dangerous for the speaker if you don't know exactly what the speaker is capable of and how to measure it, as you can easily exceed the mechanical limits of the driver and force it to Xmech or beyond (bottom it out.)  This is why enclosures are important, and may be what was being discussed before.

Turning up the volume control on a pre-amp (head unit) can introduce clipping in the output signal going to the amp.  This causes massive amounts of high frequency (and other types) distortion and can blow voice coils easily.  This is one common cause for blown speakers, especially mains, by people trying to get more out of a system than it is capable of.  They may set their amplifier gains very carefully and never clip the amp, but if they crank the HU too much and clip the output stage of the HU, they can still blow their speakers.  I've seen it many times when idiots "crank" their volume knobs too far too often, especially with cheap-ass head units.  Volume controls often cannot be turned up past about 70%, and I've seen some crap head units that clip at about 25%.  It's important to know your gear and know what its limitations are before using it, especially for loudspeaker testing.  :)

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willdkartunes 
Copper - Posts: 250
Copper spacespace
Joined: February 01, 2006
Location: United States
Posted: March 13, 2006 at 1:21 AM / IP Logged  

Wow! A head unit clip at 25%!? That IS really crappy. Your totally right about that head unit thing too. This is why we tried it with the amlifier gain at full and halfway, just to make sure. With the volume at 80%, it could have still sent a clipped signal and caused the speaker to become damaged, that is true. I don't think I did because of the fact that when I had the JBL 500 watt amplifier hooked up to the subwoofer with the amplifier gain half-way (this was before I hooked it to the smaller amplifier), I put the volume at 80% and the subwoofer pounded! I kept the volume setting there and ran it through an entire CD of hip-hop. (which had quite an assortment of bass frequencies) That subwoofer beat for over an hour until the neighbors were threatening to call the cops if we didn't finally shut that thing off! lol. So I knew the subwoofer could take the volume setting on the HU without question.

When I did the same thing with the 60 watt amplifier hooked to it, the time it took to start popping and sounding terrible was almost immediately. (maybe 5 minutes) No other changes made, just the amplifier.

The head unit we were using was certainly not crappy neither. It was a Nakamichi CD-500.

It might of had something to do with the linear Xmax....

Anyway, I know for sure that the subwoofer definitely had damaged caused to it after we hooked up the smaller wattage amplifier to it. It sounds like your suggesting it was another reason for the speaker damage other than too little power....

Like I said before, this is a very tricky question to answer. Some people are 100% sold on the fact that a speaker can only be blown with too much power, but I'm not so sure. I'd say I'm more like 70/30 on this subject. (70% towards not being able to blow a speaker on too little power, 30% towards yes it could be possible) More extensive testing is needed to be done if I am to become a believer that a speaker absolutely cannot be blown off too little power.

Here is how I look at it:

I see "power" as the wattage coming from the amplifier and the "volume control" coming from the pre-amp or HU. If the "power" is too low, but the "volume control" is too high, the speaker COULD blow. If the power is too high (wattage), then it really doesn't matter too much on the volume control, because there is a pretty good chance that the speaker could blow anyway. Finally, if the power is very low AND the volume control is low, then I would definitely say that it is impossible to blow a speaker EVER.

That's my take on the subject at hand. I hope you didn't get confused by the terminology. We all see things a little different at times so if I lost you on anything, then I completely understand and that's cool. Just ask what you didn't follow like DYohn did, and I will be more than happy to try my best to clarify your confusion.

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DYohn 
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Joined: April 22, 2003
Location: Arizona, United States
Posted: March 13, 2006 at 1:52 AM / IP Logged  

OK, now I think I understand you.  This statement is correct:

willdkartunes wrote:
If the power is too high (wattage), then it really doesn't matter too much on the volume control, because there is a pretty good chance that the speaker could blow anyway. Finally, if the power is very low AND the volume control is low, then I would definitely say that it is impossible to blow a speaker EVER.

The rest of your post tells me you are still suffering from several misconceptions and non-standard usage of terminology.  This statement tells me you have a lot left to learn:

willdkartunes wrote:
Like I said before, this is a very tricky question to answer. Some people are 100% sold on the fact that a speaker can only be blown with too much power, but I'm not so sure. I'd say I'm more like 70/30 on this subject. (70% towards not being able to blow a speaker on too little power, 30% towards yes it could be possible) More extensive testing is needed to be done if I am to become a believer that a speaker absolutely cannot be blown off too little power.  

It is not a tricky question to answer at all, and I have answered it over and over in this thread and elsewhere.  It's not about belief of any sort, it's not something that you need to be "sold" on.  It's science.  It's physics.  It's the way loudspeakers work.  Sorry, but you need to study this a bit more.  :)

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Steven Kephart 
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Posted: March 13, 2006 at 2:07 AM / IP Logged  
DYohn wrote:

This is why enclosures are important, and may be what was being discussed before.

I was just pointing out to him that mechanical power handling is a function of the enclosure.  That is why he got so much excursion out of his W7 with so little power in his experiment.

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