Distortion?

 Is it safe to have the gain turned all the way up,  with the head unit set at around half to three quarters volume, if there is no distortion?

The gain on an amp is not just a secondary volume knob.  The gain knob is there to maximize your signal-to-noise ratio.  If the knob is too low then your not pulling enough signal from your headunit.  If the gain is too high then you'll end up not with distortion in your speakers, but with extra noise - meaning even if you lower your volume all the way you'll still hear sort of a hiss.  If your preouts are 4 volts then set your gain to 4 volts.  This is where you'll get the most signal with the least amount of noise.

The HU is an Alpine CDA-9827 with the internal amp turned off, the external amp is a fosgate 501x,  the sub amp is a fosgate 550s pushing two kicker comp 12's. The amp enclosure has two fans on opposing sides one pushing, the other pulling, to get cross ventilation. The 501x is powering four Infinity Refrence 5 1/4's.  the front channel also has two 3.5 Legacy tweeters, will add two more to the rear. Front channels are @2ohms and the rear is @4ohms for now. having difficulty finding 3.5 tweets that can handle 65 wrms.

Thanks for all your help!

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Audiobahn (supposedly) make 3.5" speakers that handle 60 watts RMS. I hear they exaggerate their ratings and specs. Check out this site for futher info.

https://cgi.ebay.com/dll? ViewItem&category=14937&item=3093291314

For arguements sake throw wattage out the window, it will not tell you how loud it goes nor how it will sound. Just because the speaker says it is 65 watts and your amp says it is 65 watts does not mean a thing. Your amp will make a varying amount of power for a speaker to handle. You should be looking for a speaker that sounds good, is fairly efficient and then look at the "wattage" rating. You hear in decibels, not watts. I happen to tlike the MB Quart 3.5" speakers. They sound great, a pure titanium tweeter for nice high and smooth top end and they handle power quite well. What will kill a speaker of this size is either clipping of the amp or cd player, or forcing the speaker to play a frequency that is beyond it's appliciation. Point here is that yes it too can play 100hz bass notes, it just cannot do it with the same force as a 10" sub. Thus a crossover set to 200hz or higher is usually a good safety gate for use on a speaker of this size.

The gain control on the amp is a matching device only. It allows the amp to be used with different types of cd players that have different output voltages. It is something totally different that the voltage from a battery or remote on signal, do not confuse these. The amp seems to make more power if the gain is turned up correct, this is because you are feeding more signal into the amp, however think of the gain as a redline for the engine. Go above redline and bad things will happen. The redline for amp, as set by the gain is called the point of clipping. Once this happens the amp has reached full output and is now exceeding its design, when this happens it produces a clipped (distorted) signal for the speaker to reproduce.

If you have a high output voltage, there is a large amount of signal and the gain can be turned down so that the redline is not hit right away. If you have a low output voltage, the gain is usually turned up as there is not much signal to be used so that the redline is also not hit right away. In the case of your Alpine cd player that claims to havea 4 volt preout, it is actually much close to the 1.5 volt area on the sub channel preout, thus the gain is usually kept sky high on the amp so that you can get some kind of respectable output from the subs. The danger here is clipping (redline), when that amp runs out of clean power, it distorts and passes on that signal for the speaker to reproduce. Clipping will affect a smaller speaker much faster than a larger speaker like a sub. An amp produces the same amount of power regardless of where the gain is set at. It can reach full power when the gain is turned all the way down or all the way up, the trick is to set the gain properly and accurately match it to the voltage from the cd player so as to avoid clipping.

An ociliscope will show you when your head unit and amp are clipping.  In fact, that would be the best way to set your gains.

There are two things that destroy speakers; too much power and too much excursion.  The power ratings on speakers is their thermal power handling, and is not always rated accurately.  Many companies fudge their numbers to make their speakers look good.  We rate our drivers per IEC 268-5 which is the home audio standard.  When you clip your amplifier, you are applying a great deal of power.  At full clipping, your amplifier is producing twice the power than Rms.  If the speaker can handle the power at full clipping, then you won't have a problem except for having to listen to the distortion it is producing.  But the same thing applies for clean power.  If you apply too much, it will break the speaker. 

Steven Kephart

Adire Audio

 I turned down the gain on my amps to around 3/4, sounds a little better(definatly lower volume). will keep you all posted...thanks for everything.

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Ravendarat wrote:

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Steven you arent quite right but very close. If your amp is rated for 200 watts and your sub is rated for 400 so you decide to just crank your gains up then your amp could be clipping and if it is its gonna cause a great deal of distortion and create enough heat to blow the sub. So to little power combined with stupidity will also do it.

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I can assure you that too little power will not blow your subs.  If that were true then your speakers would blow every time you turned down the volume, or the music got quieter. 

I used to run a Soundstream Reference 500 on my sub.  My sub was in a .36 cubic foot sealed enclosure, and is rated at 1600 watts rms, 4800 peak.  Each voice coil was hooked up to a channel of the amp.  I still to this day don't know how it happened, but I noticed that one of the channel's gains was up all the way, while the other was set correctly.  Now there definitely was distortion (that's why I checked) but my sub didn't blow.  Distortion doesn't blow subs, too much power does.  If the power level is lower than the sub can handle, then it won't blow.  And that is true no matter how much distortion is being played.

I understand what you are trying to say, but I think your wording is a little off.  Sure the amplifier is rated lower than the sub, but it still blows it.  But that is because the clipped signal generates more power than the sub can handle.  So it isn't too little power, but too much power.  Your comment must be based on the  outcome, not the rating. 

Steven Kephart

Adire Audio

forbidden wrote:

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I'd be careful dude, Steven is very very well versed in alot of aspects of car audio, he knows his stuff. He does not post here often but when he does you should definitely read what he writes. I have learned a couple things from him and I would think that he has from me as well. You have to read between the lines in his post but I tend to agree with him, you can clip a signal and feed it to a speaker, if the speaker is designed to dissipate the excess heat buildup it could in fact hang in there all day long being fed a fully clipped signal. Not straight dc of course. Now most speakers are not built to handle this kind of torture. Heat is the number one killer of speakers, it is a natural byproduct of producing power. Clipping  = more power = more heat. Constant use = more heat. With the scenario you posted above I will agree with you if it assumed that a basic sub is used. If it is something that Steven hinted at, well that's a whole different ball game.

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Wow, thanks for the compliment Forbidden.  I really appreciate it.  And yes, I have learned a lot from you as well.  Your extensive experience and knowledge from installing for so long is a very valuable asset to this forum.  You have been missed at Car Audio Talk.

I do want to add that my comments are for basic subs too, and any speaker for that matter.  If you have a blown speaker, then you applied too much power.  It is as simple as that.

OK fair enough. Mabye my wording wasnt very clear. I may have missed what you were saying as well. All I was saying is that an amplifier that is rated much lower than the sub and placed in the wrong hands could blow a speaker just as easy as a amp with too much power. All I was trying to say is that if someone is trying to use a small amp and compensate by cranking the gain to the point of clipping it will blow the sub. If you back track that problem it comes down the the amp not being big enough and a customer who isnt properly informed.

PS. I wasnt trying to imply that you didnt know what you were talking about or disrespect you in any way. I just thought it was a point that was missed. Sorry for the confusion

No problem at all.  I actually hear your argument quite a bit.  Basically you were looking at it from a different perspective.  You are correct that a lower rated amp could in fact destroy a subwoofer with a higher power rating.  But putting it as "too little power can hurt a driver" is misleading to others that don't understand.  They see that and start posting it everywhere.  What they don't understand is that in the scenario, it wasn't too little power that did the damage.  It was a misused amp.  Because of that confusion, I like to set things strait when I hear that phrase.  Too much power killed the sub.  The ratings have nothing to do with it, so they shouldn't be commented on.

Maybe that would be a good argument for max ratings on amplifiers.  If people matched that to their drivers, then we would probably see fewer blown subs. 

Steven Kephart

Adire Audio

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talking about Willis? Turn what up, the volume or the gain? If you want to turn the volume up then you had better be bang oon with that gain setting or your trusty old Livin' Loud is going to be Livin'SixTeetUnder.