10" MOMO Blown??
broguearcher
Posts: 28
I have a Polk 10" MOMO sub that I've put into a sealed box designed with .6 cubic feet of air space. Also added enough filler material in the box to occupy about 1/4-1/3 of the space.....
Have a bridged amp running about 150 RMS to it. I get what I consider to be a very impressive amount of bass from it and generally it seems real tight. Running it on the low pass crossover setting of the amp.
When I open the trunk of my car and watch/listen to the speaker play I notice that it seems to be making some additional noise that I believe could be an indication of damage. The bass is still relatively clean when listened to close up but there is an accompanying vibration that is coming out -- it has a hollow sound to it compared to the "normal" bass noise the speaker makes. Is it blown or somehow damaged? Anything that I should check out?
It makes the vibrating noise on both the low and full crossover settings and it becomes much more noticeable as the volume to the speaker is increased. Inside the cabin of the car the sound is really not prominent and is nearly drowned out by the pounding bass the speaker generates.
Thanks for the help!
to further clarify: it sounds a bit like a vibration (just checked again yesterday) that would result from a hole in the speaker or the rubber surround. When hearing it I could imagine that I would find a rip or tear at some point. No such thing to be found though. I'm wondering if the issue could be due to improper seal around the sub itself..... when I push the woofer in lightly I hear what appears to be escaping air but I can find no actual indication of air coming out where the sound comes from. When I let go of the woofer after pushing on it (I know, I'm not supposed to do this but at the time I didn't know that!!) it releases slowly and comes back to original position after a full second or two.
Thanks again. Sam.
Well if a woofer is blown it will show 0 ohms on a multimeter, but since it is still playing this won't help you. The only way I have found to check and see if a voice coil has some minor damage is to press evenly on the woofer cone when the music is turned off and see if there is any scratching noises. You MUST press evenly centered on the woofer to do this test, because if you put more pressure on one side of the cone then the voice coil may rub even on a perfectly good woofer.
With all that said, sometimes when you open a trunk the woofer looses the pressure that it normally sees on the front surface of the cone which can cause it to slightly over-excurt and produce the sounds you are talking about.
I have a sealed 10" in .65 cf box in the back of my Tahoe, and when I open the rear hatch and listen to the woofer playing it sounds like crap even though the woofer is fine.
Basically, if it sounds good during normal listening with the trunk closed, I wouldn't worry about it.
Mike
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Sheng Ya CD-S10 tube CD player
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Old Yesterday, 02:21 PM #3
neomagus00
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you'll want to re-post this in the 'subwoofer talk' section of the forum - that's where us car guys hang out.
but for a quick rundown of possibilities - i don't recall if that model has woven tinsel leads, but does the noise have a 'buzzing' quality of any kind? if so, it's probably tinsel slap, which is annoying but normal. check all the seams of your box, including where the sub is mounted, to make sure it's totally airtight. you could be getting 'ringing', which again is annoying but not harmful.
basically, if it sounds normal from the front, and the noise doesn't make you cringe in fear when you listen to it up close, you're probably fine. a scraping or gritty noise is bad, a buzzing could be bad, a popping could be bad, but a 'hoom' (like the ents in lotr) is probably fine.
oh, and i would NOT press down on the cone like bsu reccommended - it's too easy to get the angle wrong and damage something, and it's more a confirmation that the woofer is bad than a check.
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Old Today, 08:31 AM #4
broguearcher
Polkie
Join Date: Apr 2006
Posts: 2
Have a bridged amp running about 150 RMS to it. I get what I consider to be a very impressive amount of bass from it and generally it seems real tight. Running it on the low pass crossover setting of the amp.
When I open the trunk of my car and watch/listen to the speaker play I notice that it seems to be making some additional noise that I believe could be an indication of damage. The bass is still relatively clean when listened to close up but there is an accompanying vibration that is coming out -- it has a hollow sound to it compared to the "normal" bass noise the speaker makes. Is it blown or somehow damaged? Anything that I should check out?
It makes the vibrating noise on both the low and full crossover settings and it becomes much more noticeable as the volume to the speaker is increased. Inside the cabin of the car the sound is really not prominent and is nearly drowned out by the pounding bass the speaker generates.
Thanks for the help!
to further clarify: it sounds a bit like a vibration (just checked again yesterday) that would result from a hole in the speaker or the rubber surround. When hearing it I could imagine that I would find a rip or tear at some point. No such thing to be found though. I'm wondering if the issue could be due to improper seal around the sub itself..... when I push the woofer in lightly I hear what appears to be escaping air but I can find no actual indication of air coming out where the sound comes from. When I let go of the woofer after pushing on it (I know, I'm not supposed to do this but at the time I didn't know that!!) it releases slowly and comes back to original position after a full second or two.
Thanks again. Sam.
Well if a woofer is blown it will show 0 ohms on a multimeter, but since it is still playing this won't help you. The only way I have found to check and see if a voice coil has some minor damage is to press evenly on the woofer cone when the music is turned off and see if there is any scratching noises. You MUST press evenly centered on the woofer to do this test, because if you put more pressure on one side of the cone then the voice coil may rub even on a perfectly good woofer.
With all that said, sometimes when you open a trunk the woofer looses the pressure that it normally sees on the front surface of the cone which can cause it to slightly over-excurt and produce the sounds you are talking about.
I have a sealed 10" in .65 cf box in the back of my Tahoe, and when I open the rear hatch and listen to the woofer playing it sounds like crap even though the woofer is fine.
Basically, if it sounds good during normal listening with the trunk closed, I wouldn't worry about it.
Mike
__________________
Polk SDA-CRS+ (RDO tweeters)
Aragon 4004 MKII amplifier
Acurus RL-11 preamp
Sheng Ya CD-S10 tube CD player
Transparent cables
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Old Yesterday, 02:21 PM #3
neomagus00
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Join Date: Nov 2003
Location: Dayton, OH
Posts: 3,702
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you'll want to re-post this in the 'subwoofer talk' section of the forum - that's where us car guys hang out.
but for a quick rundown of possibilities - i don't recall if that model has woven tinsel leads, but does the noise have a 'buzzing' quality of any kind? if so, it's probably tinsel slap, which is annoying but normal. check all the seams of your box, including where the sub is mounted, to make sure it's totally airtight. you could be getting 'ringing', which again is annoying but not harmful.
basically, if it sounds normal from the front, and the noise doesn't make you cringe in fear when you listen to it up close, you're probably fine. a scraping or gritty noise is bad, a buzzing could be bad, a popping could be bad, but a 'hoom' (like the ents in lotr) is probably fine.
oh, and i would NOT press down on the cone like bsu reccommended - it's too easy to get the angle wrong and damage something, and it's more a confirmation that the woofer is bad than a check.
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It's not good, very fundamentally simply not good. - geolemon
No single raindrop believes it is to blame for the flood. - despair.com
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Old Today, 08:31 AM #4
broguearcher
Polkie
Join Date: Apr 2006
Posts: 2