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Put my 15 out of its misery?


MrShiffles

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Ok guys, so I've had this NVX VCW 154 for around 2.5 years and was a good sub..I recently put it in its 2nd vehicle (Nissan Altima) where it resides in the trunk(same amp, a JBL GTX500)... noticed a buzzing sound lately that sounded like coil rub..so I go to check it out by pressing on the cone, dead silent (even my DMM reads at 1.9ohms)..but low and behold, there is a partial separation of the surround from the cone! I tried to repair, but to no avail, it's still the same...still hear that noise and frustrated, but still has decent output surprisingly...

 

Questions: Is the basket/motor worth a custom recone? It's a pretty good looker as far as the rear end goes LOL, yes, and I liked how it sounded ported! OR just chuck it, cut my losses and put my money into a better quality(perhaps custom built sub.) I've been looking at Fi, Sundown, DC, Wolfram etc...I like SQ and  it couldn't be more than $300 and I do plan on ditching the amp for something more powerful...

 

in the meantime I go back to my Polks <sigh>

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You need to turn the gain on your amp down. You are clipping (Distortion) the shit out of whatever subwoofer(s) you are putting on that amp. For sure. That subwoofer was seeing a little more than a quarter of its rated rms after impedance rise. You are overextending that subwoofer because the signal of the amp (the gain) is set lower (the more the gain is turned up, the lower voltage the signal is) than the sign the head unit is sending via RCA wire. That surround is not only glued to the cone but it’s also stitched to the cone. Another culprit could be that the enclosure could be way too big causing over excursion rather than clipping. Even if it wasn’t stitched, there is no reason that subwoofer’s surround should have spear red from its cone, except for something puncturing the subwoofer, the enclosure being way too big or what I’m almost positive it is, DISTORTION. Don’t spend money on another subwoofer or a recone kit for that subwoofer. Order a dd-1 to set your amp’s gain correctly and some clamps and some good epoxy and fix that subwoofer correctly. 4” spring loaded clamps and loctite 5 minute instant mix epoxy should do the trick.

 

https://www.wccaraudio.com/smd-distortion-detector-dd-36.html
 

https://www.grizzly.com/products/GRIP-4-Extra-HD-Spring-Clamp/T31539?iparcelcountry=US

 

https://www.walmart.com/ip/Loctite-Epoxy-Instant-Mix-5-Minute-0-47-fl-oz-Syringe/20470699
(the higher the “psi” rating on the epoxy, the stronger)

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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Its possible I over drove it...box is only 2.5 cube tuned around 35Hz...as I dont have a subsonic filter on the 500 watt amp its likely I hit some low low notes and could have caused the separation...or maybe I bought it from a bad batch from whatever build house that was sleeping on the job that day...I didnt see any evidence of where the stitching actually was connecting anything...almost like it was glued on top of the surround for show

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You were clipping. You are clipping. In that enclosure, which is small and that subwoofer would have good control because it’s a small enclosure and wouldn’t overextend. I would understand if it were a super big enclosure that was tuned too high, higher than 35hz, then that could cause a subwoofer to overextend. And on minimal rms, even in a super big enclosure tuned too high, the minimal rms would make it less likely to overextend. I don’t care what frequency is played, if it’s a clean signal it wouldn’t of done that to that subwoofer in that enclosure. Think what you want. If you don’t turn that amps gain down you are gonna have to keep replacing subwoofers or fixing subwoofers. Distortion detectors are VERY IMPORTANT. If you can’t afford to buy a dd-1 at the moment then I’m gonna post a video on how to make one and then post a link where to buy the capacitor you would need to make said distortion detector.

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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A handheld oscope can also be used, even a multimeter. I recently borrowed a DD1 from an awesome member here and compared using a DD1 with using a multimeter to set the amp gain, they were VERY close. But that still wont tell you your max volume on your head unit that plays a clean signal. And if your turn your head unit up past that point there will be distortion.

 

To use a multimeter to set the amp gain just take the wattage of your amp times the impedance the subs are wired to and square it. 

 

So for example 500 watt rms amp at 1 ohm... 500X1 = 500 square that and get 22.36 volts.... Now disconnect your subwoofer, from the amp, and play a 40hz test tone at the max volume that gives you a clean signal, if you dont know that volume level, assume its 75% of max and pretend that is your new max volume.... Then slowly increase the amp gain until you get close to but not over 22.36 volts AC coming out the amps speaker terminals. 

 

 

ALL THAT BEING SAID.... A DD1 is still a good investment if you can afford it. But i understand its hard to drop the money on something you will likely only use once. A multimeter is cheap and everyone should own one anyway. 

Singer 250amp Alt, Singer PCM bypass harness

Titan8 Lithium Underhood safe BCI PWR-S5

Big 3 W/ dual runs of power/ground. All 1/0awg OFC

SounDigital EVO 5K amp, Two 15" Fi SSD subs

Next Level Fabrication @ 7 cubes net, tuned to 32HZ 

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3 minutes ago, Backwoods said:

A handheld oscope can also be used, even a multimeter. I recently borrowed a DD1 from an awesome member here and compared using a DD1 with using a multimeter to set the amp gain, they were VERY close. But that still wont tell you your max volume on your head unit that plays a clean signal. And if your turn your head unit up past that point there will be distortion.

 

To use a multimeter to set the amp gain just take the wattage of your amp times the impedance the subs are wired to and square it. 

 

So for example 500 watt rms amp at 1 ohm... 500X1 = 500 square that and get 22.36 volts.... Now disconnect your subwoofer, from the amp, and play a 40hz test tone at the max volume that gives you a clean signal, if you dont know that volume level, assume its 75% of max and pretend that is your new max volume.... Then slowly increase the amp gain until you get close to but not over 22.36 volts AC coming out the amps speaker terminals. 

 

 

ALL THAT BEING SAID.... A DD1 is still a good investment if you can afford it. But i understand its hard to drop the money on something you will likely only use once. A multimeter is cheap and everyone should own one anyway. 

You were forgetting about impedance rise when it comes to tuning with a multimeter. If you would of figured that then I bet you would of tuned it with that multimeter on point. That’s what’s up somebody let you borrow their dd-1. That was super cool of them. But you are a good dude and have never showed any signs of not being a good dude. So that’s why whoever trusted you. After using that dd-1, did it make you want to buy one? Dd-1’s are the shit. 

:stupid:“How can we help you?”
:guido:
“And don’t forget to tell them that 
the customer isn’t always right.”

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6 minutes ago, 1point21gigawatts said:

You were forgetting about impedance rise when it comes to tuning with a multimeter. If you would of figured that then I bet you would of tuned it with that multimeter on point. That’s what’s up somebody let you borrow their dd-1. That was super cool of them. But you are a good dude and have never showed any signs of not being a good dude. So that’s why whoever trusted you. After using that dd-1, did it make you want to buy one? Dd-1’s are the shit. 

 

Yeah man, i didnt even think of impedance rise when i was doing it, but that makes perfect sense.

 

If i were to change head units i would DEFINITELY want to purchase a DD1.  And it was super cool of them. Its hard enough to trust anyone locally, even harder trusting someone you never met on the internet. Too many snakes in the grass as they say. But there are still some good people out there!!

Singer 250amp Alt, Singer PCM bypass harness

Titan8 Lithium Underhood safe BCI PWR-S5

Big 3 W/ dual runs of power/ground. All 1/0awg OFC

SounDigital EVO 5K amp, Two 15" Fi SSD subs

Next Level Fabrication @ 7 cubes net, tuned to 32HZ 

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