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Blown sub woofer

  1. Jun 23, 2012 #1
    Hi I've installed my own amp+sub into my car. I thought I was right matching the RMS up, there both 300vRMS (I've read that I should of got a smaller amp). So I had it pretty loud today and it just stopped working. Wired up another speaker and the amp is working fine. checked the internal wiring to it, visually it looks ok.

    I have no tools till I go into work on monday, so I was wondering what could it be thats broken? anything that I can replace?
  2. jcsd
  3. Jun 23, 2012 #2
    I've been reading more up on it, after testing it with a 9v battery, nothing happens.
  4. Jun 23, 2012 #3
    You mean you connect a 9V battery across the sub woofer and no sound? If the wiring into the sub woofer is ok, you are in deep dodo!!!! If it is new, return or exchange. It must be defective. I never have a speaker blown open. I played guitar, I am talking about serious power. Usually the voise coil deformed and stick, never seen one burn wire. I only smoked, blown open a 3" small radio speaker..........Using a 100W Marshall amp!!!!.............I just want to see how a speaker die............after some drinks.........when I was in the 20s!!!!

    If you can see the speaker, look at the two wires going from the solder post to the paper cone. I've seen one that broke.
  5. Jun 23, 2012 #4
    Thanks for your reply, there is no sound and no movement when connecting the 9v battery. I bought it from someone and not from a shop, it was an unwanted gift so I have no receipt for it.

    I have took the sub out the box and the visible wires going into the cone all seem fine.

    Also to rectify my first post the amp was 300vRMS and the sub was 400vRMS so this couldn't of been the problem?
  6. Jun 23, 2012 #5


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    I think you are confusing your numbers. 400 volts RMS into a load of 4 ohms is 40,000 watts. Do you mean 400 watts? BTW, a watt is never defined in RMS. It is a car audio sales gimmick.
  7. Jun 23, 2012 #6
    Then I think it's the end of the road. It doesn't matter what amp rating, the speaker is gone. Sorry.

    Wattage of amp mostly give you the head room or dynamic range. You never really drive 100W or power. An average of 10W power sound really really loud already, all the head room of the amp is just to give you the instantaneous attack.

    Also, you have to be careful about the speaker rating. The enclosure of the speak make a day and night difference in the power handling capability. If the speaker is designed and rated for a closed back and you put it in an open back cabinet, you are going to have problem. I am not an expert in speaker cabinet design by any stretch, but I know enough that the back pressure makes a difference on the power capability.
    Last edited: Jun 23, 2012
  8. Jun 23, 2012 #7
    Please interpret this post as sincere.
    With hundreds of watts of bass in your car you need to be more concerned about damaging your hearing which is not easy to fix or replace.
  9. Jun 23, 2012 #8

    jim hardy

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    SHOULDN't ..........

    is it fused or proteted by one of those thermal snap switches?

    If not it's probably burned open. Any smell?

    RE RMS watts - there is a sneaky advertising trick, to publish the "peak instantaneous power" which somehow works out about 4X continuous RMS rating.
    Here's an entertaining article about power ratings and marketing ethics.
    so your 400 watts might be a lot less honest continuous watts. Check the fine print ?
  10. Jun 23, 2012 #9


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    Consumer/automotive amp/speaker ratings are far less than honest. Also, you can blow a fairly decent speaker just by feeding it a clipped signal. Solid-state amps don't sag when you push them. They clip, sending really square wave-forms to the output stage, and resulting in burned speakers.

    Can any guitarist here imagine having a Fender Twin Reverb in the back seat of your car at full chat? They are about 80 watts through two 12s. I used mine at outdoor parties (usually biker bashes) or in very large indoor venues. 80 watts is overkill for almost any venue. The notion that any automotive amp/speaker combination is going to deliver that kind of power is a bit silly.
    Last edited: Jun 24, 2012
  11. Jun 23, 2012 #10
    I missed my Twin and My Marshall Plexi 100!!! I was so stupid those days selling the Marshall to buy a car!!!! Those were so loud, my ears hurt playing them. Now I have a Marshall JCM900. Not only I have to pull a pair of tubes out, I even replace the other two with the Yellow Jacket socket to adapt to the EL84 to lower down to 15W. Still is too loud for me!!! I finally bought a THD Hotplate, then I can dial in some sweet tone.

    Yes, the clipping wave kill speaker particular the high quality sensitive ones. That's the reason guitar speaker have stiff cone to withstand the transition. But clipping usually cause voice coil deform, seldom open the speaker out right. As I said, the only time I burn a speaker out right is the Marshall driving the 3" radio speaker. I stroke the guitar, I could see the smoke came and then went dead!!! Still took a few strokes!!!!

    This is what age do to you.....I mean me!!!!
    Last edited: Jun 23, 2012
  12. Jun 24, 2012 #11
    hi I'm not at home now but I've accepted its broken and unfixable due to my negligence, I'm guessing the gain was set incorrectly.

    However the values I remember reading for the sub were 1200w Peak and 400w RMS. I might of got mixed up in my other posts, but I don't under stand why it really isn't that when it says minimum 300w input?
  13. Jun 24, 2012 #12


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    These are not reasonable (honest) values, by any means. There is no way that you could have such audio power in a vehicle. Did you read my post about the Fender Twin Reverb? I have never driven a Twin flat-out, even in an outdoor concert or in a large indoor venue. Those monsters are ~80+ watts and would deafen you at close range. If you could jam one into a car and run it at close to max, nobody could stand to be in there. Those are "stadium" amps, used by lots of professional musicians in huge venues, and they are "only" about 80 watts or so.

    Ratings for consumer/automotive audio components are just "bragging rights" numbers slapped on to boost sales. They are not real. Don't trust them. And again, if you're pushing a SS amp, it will clip, sending square wave-forms to the output, which will turn speakers into toast.

    There is a kid down the road who has a crap car, and who has a stereo installed that probably cost him more than the car. I can hear him coming before he even gets within sight (at least 1/10th of a mile in either direction), and all I can hear is "thump, thump, thump". He is ruining his hearing.

    This would be a wonderful time to install a decent stereo and enjoy the music as you are driving. If you are dialing up the "thump, thump, thump" and can't hear whatever else is around you, I hope you are not driving on the same roads as me. Not safe.
    Last edited: Jun 24, 2012
  14. Jun 24, 2012 #13
    If these values cannot be trusted what should I be looking for? Or is it not published.

    You can imagine me as that kid on your street as just turning 20. Just that my stereo certainly didn't cost more than my car haha.

    If I was to buy a more expensive audio system what is it that I should be looking for, the one a broke was only about £100
  15. Jun 24, 2012 #14


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    Please look at an audio system that is mainstream. Something that is meant to deliver accurate renditions of CDs and radio without slamming you with the "Thump, thump, thump". That stuff will ruin your hearing, and you might like to be able to hear later on in life. If you have a decent sound-system installed, and you can listen to the Beatles, Frank Sinatra, Patsy Cline, etc at comfortable volumes (I used these performers as examples because I am older than dirt), then you might have an OK set-up. I grew up with tube-driven radios in cars (Delco), and they were pretty darned good, even with the cheesy oval speakers in the dash.

    I hope you can get out of that bass self-abuse situation and start enjoying mainstream music at reasonable volumes. Just put on some road-tunes and enjoy your drive. I always have to have music on when I am driving. I'm only 60 years old, and maybe I might lose the need for music further down the road, but I don't think so.
  16. Jun 24, 2012 #15

    jim hardy

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    Before risking another expensive speaker I'd do some looking.

    Some amplifiers when severely overdriven are capable of something called "Latchup".
    An internal stage starts working backwards and the amp puts out however much DC it is capable of making, several amps, and melts the speaker winding.

    I'd connect a DC meter across my speaker and drive it really hard. 400 watts into 4 ohms would be 40 volts AC so a 20 or 50 volt DC meter would be okay. It should read zero so long as it sees AC. If latchup happens meter will read high DC and speaker will go to one end of its travel, and start smoking soon.

    Some woofers are only two ohms and not all amplifiers are " 2 ohm stable" check your setup
    and speakers made for vented enclosures have a stiffer surround than for sealed enclosures, that too could affect the load speaker presents to amp.

    I hope you are interested enough to get into speakerbuilding. I hate those boomer amps where all you hear is the resonant frequency of the car's sheet metal . Isobarics are popular now and do a much better job.

    If your ears ring you are damaging them. One day the ringing won't subdside but remains faint in the background, and it gets more intense as the years pass. It's called "Tinnitis". I worked around big machinery for decades and mine started in my 30's. It's cumulative. So be aware.
    Last edited: Jun 24, 2012
  17. Jun 24, 2012 #16


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    If you take the back off you can trace the wiring through and check for continuity inside the box. It would be a shame just to chuck the thing out without a bit of investigation.

    I agree about the ridiculous level of listening to music in cars, though. The whole neighbourhood is subjected to the din whilst you steadily knacker your hearing. Does that make sense (to someone who has the sense to post on PF)?
  18. Jun 24, 2012 #17

    jim hardy

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    I'm kinda with turbo and Sophie.
    But I understand the need of youth to put on a show, it's in our genes i think and i remember my own younger days. Push pull 6v6's of the time just couldn't make today's decibels.

    With today's electronic gizmos you guys could at least give us old folks in traffic a laugh.
    Surely some MP3 files could go on one of those USB memory sticks and plug into the stereo?

    Mozart: "Marriage of Figaro" overture for passing a wedding procession
    Johnny Bond: "Hot Rod Lincoln" when adjacent a Navigator
    Jerry Reed: "Lord Mr Ford" at the auto parts store
    Mussorgsky: "Night on Bald Mountain" for that frenetic rush-hour Freeway dash
    Strauss: "Thus Spake Zarathustra" while waiting out a long traffic light
    Roy Orbison: intro to "Pretty Woman" self evident​

  19. Jun 24, 2012 #18
    Just want to say just because I listen to music loud once in a while doesn't mean I have it as loud as possible everytime I go out in my car. I come here for my advice on trying to fix it myself since I am an apprentice in electrical maintenance and I like learning. Stereotyping is wrong and I guess you think I listen to rap music, far from it :) anyway going to bed I look forward to your input.
  20. Jun 24, 2012 #19


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    I can understand that you may not like to be criticised in connection with your choice of in-car entertainment but, if you don't want to listen to anti-social levels of music in your car, why do you need a gzillion Watt system? (People outside get nearly as much as you get when you're inside, you know)
    Also, when you want free advice, you sometimes have to take a bit of stick in return :biggrin:. Look upon it as payment for some valuable help.
    Did you consider opening the box and seeing exactly what it looks like inside? If there are 'brown smells' in there then it may have a burned out bit. If not, then look for a broken connection and get soldering. I have known of speech coils coming disconnected from the braided connecting wire. It is not too difficult (with some care and a small soldering iron) to repair that sort of fault and - what the hell - the device is shot anyway so you have nothing to lose.
  21. Jun 24, 2012 #20

    jim hardy

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    okay i'll bite.. what does youth listen to these days? perhaps a link..?

    Myself I mostly do a mix of old R&R and light stuff played by a symphony a couple of favorites:

    Last edited by a moderator: Sep 25, 2014
  22. Jun 24, 2012 #21
    Haha, I don't even listen to music, I listen to news and news talk. I don't care much about music or the musicians. I've been there, live their live style for years. The best thing was......I got out of it.....I grew up. I don't believe what they believe, I don't agree with anything the typical artist believe. I only involve in music now because of the electronics.

    I only play the guitar to test the electronics now. I was actually quite good in my time, I won 4 biggest talent contest in Hong Kong between 70 to 72 and nobody did that before. Been on TV and all. I started my career in electronics because of the the desire to get the best amplifier in the late 70s. I got so into electronics that I quit music in 1979. That's the best decision I made in my life and that was the turning point in my life. After all these years, I can truly say, electronics IS the love of my life, still excited about it. I spent the last 10 years studying and still studying even I don't work anymore......And still hang around here!!!!:rofl:
  23. Jun 25, 2012 #22
    I'm sure when I get on my computer you would love all the YouTube links I give you.

    I have already taken it apart and there is no smells off burning but the cone makes a grinding noise when lightly pushed, I've read that means its gone.

    I'm also picking up a new one today which is less powerful but better quality than the one I broke, you may be pleased to hear :)
  24. Jun 25, 2012 #23
    The scratching noise is very typical with a speaker that has been over driven. It's gone one way or the other. Don't crank it all the way with the new speaker, it'll die again.

    I am into audiophile, loud bass don't equate good sounding. Listen to some high end system, they are very balance, have clarity, transparent and good separation. One big different between a good system and a want to be is, the good one sound good at low volume, the so so ones sound lousy when low, you have to crank it up to sound better.

    I don't know how people do it in the car. But at home, I put the sub woofer in the place I sit, then I walk around and find the spot that sounds the loudest and best. Then I put the sub woofer there. With that, you don't have to crank up the base to hear it.
    Last edited: Jun 25, 2012
  25. Jun 25, 2012 #24

    jim hardy

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    yes something is deformed. The voice coil runs in a narrow cylindrical space around magnet and something in there is rubbing. Could be coil deformed by heat or end of coil form hammered against mechanical stop by overtravel. Latter can happen with a too compliant speaker (soft foam surround) in a vented enclosure.

    Here's a link to another blogsite where a newbie guy learned about speaker enclosures


    you might enjoy it - his enthusiasm was infectious.
    It has links to speaker design software.

    old jim
  26. Jun 26, 2012 #25
    Hi im at work now so I will look at that when I'm home.

    You will be glad to know I've got the new sub in. Turned down app the dials on the amp and set it up correctly. The sub now compliments the other speakers nicely without a loud over powering thump.
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