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OUberLord 16th August 2004 07:32 PM

Speaker unexpectedly popping
Hi all,

I was hoping you could help me with a problem I am having. In my car I have a JVC CD player (4x50) and recently replaced blown factory 3" front speakers and 6"x9" 120w Audiovox rear speakers with 3" Rock-Fos 30w for the front and 6"x9" Rock-Fos 180w for the rear. With my old speakers I could have the bass at full (A bad thing, I know, but I didnt care for the old speakers) and volume at 24 (A relative number as far as I know) and get "decent" sound quality at that volume and no popping or similiar distortion. However, with the new speakers I get popping in the rear right speaker at 20 volume with the bass set to about 3/4ths.

I know popping can be due to overpowering a speaker but I cant see how that is possible. I do have the balance set to mostly rear, but that should only push the watts to about 80ish per speaker. When the popping occured I did have the fade set to slightly favor the right, but have not tested the issue with the fade set to neutral.

Can anyone offer any insight into this problem? The speakers are new, so while they haven't been abused I suppose the rear right one could be defective. In my forum search I did find someone who had a similiar problem at this link but I don't have an amp, and thus cant set anything in that regard.

SupraGuy 16th August 2004 09:34 PM

First off, wattage ratings for deck power are at best wishful thinking and at worst outright lies. If your 50X4 JVC deck is pushing more power than my Alpine MRV-F300 (30WX4) I'll eat the heatsink.

Power does not kill speakers. Distortion kills speakers.

Watage ratings for speakers seems to be mostly a marketing number, and has little if anything to do with a speaker's actual power handling capability. I used to have a PPI 75X2 amplifier, which I had at one point connected to a set of 8W (Yes 8) speakers, which sounded beautiful. And just to prove a point I connected the amp put to a pair of "300W" 6X9 speakers that a friend bought at a liquidation outlet and left a smoking hole in the speaker cone where the voice coil used to be. (He thought that was so cool that he didn't even take me up on his offer to reimburse him the $15. :D )

Back to the topic... I've seen more speakers killed on deck power than I have on any separately amplified system. The power supplies in the decks just aren't up to creating that much power, so they clip. The clipping does nasty things and starts heating up the voice coil, which sooner or later ends up as a blown speaker.

You are NOT overpowering the speakers, but you are most likely clipping the internal amplifiers, which has about the same audible effect. You WILL damage your new speakers by continuing to do this. I will say that if you are not getting 80ish watts from that deck, not even in total.

Turn it down, so that the amplifier does not clip. If you MUST have more volume, start looking for a good amplifier.

maylar 16th August 2004 09:55 PM

I agree with supraguy that the 50x4 power rating on your deck is a peak number, typically relating to about 20 watts rms before clipping.

However, I think your speakers are simply hitting their maximum travel. That hapens on bass notes, and makes the characteristic "popping" noise you mentioned. You need better speakers...

OUberLord 16th August 2004 11:55 PM

Thanks for the quick response guys, but if you could I do have a couple more questions.

The speakers in question are the Rockford Fosgate Punch FRC4369, which got pretty good reviews as far as speakers go so I think they are at least decent (Though tell me if they are otherwise, I dont want to waste efforts on a speaker setup that is sub-par).

Tempting fate and with warranty in hand (which covers abuse), I evened out the balance between left and right and tested it again. This time at 20 at 3/4ths bass it was fine, even fine with full bass (Though I only tried that for a second or so, and was too much bass for my liking anyway). Other than being really loud, there was no popping or distortion.

Im thinking maybe theres something screwy with the way my deck distributes the sound between left and right when the balance isnt neutral, but more likely that like you said the deck is puching them too hard.

My second question is, wouldnt an amplifier compound the problem by adding more power? Im new to that aspect of car audio, so any enlightenment would be greatly appreciated.

Either way, thanks for your help and quick responses.

OUberLord 17th August 2004 01:06 AM

Sorry for the double post, but since I am a new user I'm under the moderation filter and couldnt find an "edit" button for my post that is waiting to be queued. Im sorry if this aggrivates anyone, but I felt it was prudent as I learned a few things between the time of submitting that message and now.

So clipping occurs when the deck is telling the speakers to do something but the deck isnt providing enough power to do so, effectively screwing up the waveform and causing the noise I heard. The reason my old speakers didnt is because I had the balance set to all rear so all available power was devoted to the speakers, thus giving them enough to do what the deck was telling them. The reason the rear right speaker popped could have been because since I had the settings set to about 3/4ths rear and slightly right, a good chunk of the deck was telling that speaker to do something it simply wasnt getting enough power to do. Does all of this sound correct?

Which brings me to my "new" next question, being as I now know that if the above is true an amp would help alleviate the problem, does anyone have any suggestions / pointers in the amp department? Im assuming that a 2 channel amp rated for 400w is 200w per channel, which considering what it actually puts out would be a pretty good fit for my 180w speakers (I dont plan on maxing them out, or would a 200w or 300w suffice?

Again sorry for the double post and thanks for your guys help.

maylar 17th August 2004 06:34 PM

"Clipping" distortion happens when you push an amp beyond it's limits. The amp runs out of power and can't follow the waveform at the peaks. That's bad for speakers. Typically this starts to happen at about 3/4 volume for most HU's (45 out of 60 on my Pioneer). Clipping usually sounds scratchy or harsh.

Popping noises are different, and usually come from pushing the speaker cone to its limit of travel. That can only happpen with too much power, and always shows up on bass notes because the lower frequencies make the speaker move further. That's what I thought you were describing.

I read some reviews and specs on those 6x9's and they look very nice. I don't believe you could push them to overexcursion with HU power. So I'm not really sure what you're hearing.

HU's run out of poop at about 20 watts rms. Those speakers can handle twice that easily. And if you limit the bass (using the hipass filter feature of an amp) you'll be able to get them up even higher. That's why amping speakers makes them sound so much better. You can make them loud without having the amp clip.

I would get an amp 50-60 watts rms per channel for them.

SupraGuy 17th August 2004 10:52 PM

While I've seen some head units that are actually capable of 20W, they're few and far betwen, and have distortion numbers at those power levels that just make me wince.

Look at the little red (typically 16 AWG) power wire to your head unit, then look at the 15A "radio" fuse on your fuse box that's providing power to it, take into account that's for 4 channels...

Anyway, more power from an amplifier also means more cone control. Think of it as the deck power is kind of throwing the speaker cone around but not really making it do what it's supposed to. Just "close enough" so that it sounds more or less like it's supposed to.

Add more power. The speaker is now doing exactly what the amp is telling it to, and that also means stopping at the excursion limits like it's supposed to. It's going to be easier on the speaker overall.

Another thing to be aware of is that many speakers depend on an enclosure to provide some cone control as well. Even those cheap 6X9 boxes will help improve the speaker's ability to handle power greatly.

Personally, I've never liked the sound of Fosgate speakers, but that's completely a personal preference.

Spiro007 26th August 2004 05:40 PM

Hey is the poping sound like the noise of the speaker voice coil bottoming out on the speaker magnet back plate,, if so thats nasty.. You may be running the speaker bellow its resonant frequency without sufficient damping. ie you need a box. post you speaker specs for qts vas and Fo.

Also if they are bottoming out maybe the speaker wire on one speaker is out of phase, ie neg connected to positive and vise versa, this can also cause bottoming out of the speaker as the

If it is poping but not bottoming out then it may be the case that you are draining too much current from the head unit and it is going into current limiting. How many ohms load are you putting on the speaker wires?
is there any short circuits on the speaker wire?
are the speakers second hand? some high quality speakers have tight voice coil gap and when they overheat and burn the enamel on the winding they still work but the swelling of the voice coil can cause rubbing in the magnet air gap causing scraping sounds at first the open or short curcuits.

OUberLord 31st August 2004 10:39 PM

Hi all,

I figured Id pop back in to give an update in accordance with the help Ive recieved and ask a few (hopefully) final questions.

So, in the last week or so I pretty much narrowed the problem down to the rear right speaker. I almost tried to get the rear left to reproduce the popping noise, to luckily no avail. I spoke with a Rockford Fosgate rep. who told me that the speaker was likely defective given that im not trying to turn it up too loud or with too much bass, and given that the other speaker is performing fine. Upon speaker removal I found small burnt patches on the inner cone of the rear right speaker (not sure what the actual term is, but the smaller cone that resides on a raised post in the middle). Im thinking that either A) The burnt patches were there when I bought it since I didnt really look, and are causing the popping noise or B) Something wrong inside of the speaker is causing the popping noise, with the burnt patches as a side effect. So, today I have exchanged the speakers for a new set but am hesitant to put them in.

Even though im pretty much sure that the problem was a defective speaker given the circumstances and troubleshooting, I have a couple questions for you guys if you could. Given that it is the same wiring and deck that the old speakers were utilized with, if the speaker wasn't in fact defective then the problem would lie somewhere in the enviroment in which it is mounted. Both speakers are mounted hanging down from the roof of my inner trunk, with nothing beneath it other than the holding bracket. Above the speakers there is a little less than a half inch gap, then a grid of some sort of flexible material, then the cloth that makes up the interior. The grid holes are easily large enough to push a pencil through, and the "rows" that make up the grid are about 3mm in width. Would that allow for enough airflow to release any air pressure generated by the speakers, or is modification in order? Even though only the right speaker had the problem and they were mounted in the exact same fashion, I want to cover my bases and dont want to mount them up only to find a new problem to tackle.

Again, thank you for your previous and continued help, hopefully the problem really was the speaker itself and not something else.

imix500 31st August 2004 11:52 PM

Just a thought, could the "popping" be the cone and inner surround slapping this bottom of your rear deck? If the cones have decent excursion and there's not enough room they could certainly smack it on a heavy note, especially with no loading on the back of the driver besides the air in the trunk. Since the right speaker was up a little bit more than the left it would have smacked it first.

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