# Seized sub, what causes that?



## ZMan2k2 (Mar 11, 2014)

I've been running two Sundown Audio SD-2 10" subs off of an SAZ-1500D amp for about 6 months now. The subs have been performing wonderfully in sealed enclosures. This past weekend, I swapped the subs to my newly built ported enclosure (which didn't fit properly ), and the output sucked. So I swapped back in the sealed enclosure for now, and found out that one of the subs is seized. The cone will not move, no matter how much you push on it. Nothing. What causes that, and can it be fixed? I wired the whole thing into 1 ohm, which I've been running since I got the amp. Hopefully it's a warranty thing, but I'm wondering why it did it now?


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## minbari (Mar 3, 2011)

assuming that the frame isnt bent and pinching on the VC, most of the time when a cone wont move it is because the VC is fried. The windings of the coil unwind and jam up in the mag gap and seize it up.

if they offer a recone of the sub, you can do that. Otherwise see if they will replace it or buy a new one.

you are exceeding RMS by a little bit, how hard do you push them?


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## ZMan2k2 (Mar 11, 2014)

Actually, the SAZ-1500D was recommended to me by Sundown themselves. I push them hard, but nothing crazy, I still have the gain set to about 3/4's on the amp. If the VC fried, they do offer a recone service for warranty people, which I qualify for. So, I guess I'll wait for Sundown to respond, and see what they say.


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## cajunner (Apr 13, 2007)

look closely at the metal plates at the top and the bottom of the magnet "sandwich"

if you see anything that looks out of round, or between slugs, you have a shifted magnet which clamps the coil solidly.

you can check to see if one side of the cone is moving very slightly and the other side is stuck without any movement, this is because the coil is only clamped to one spot in the gap.

if the swapping of the speakers had any jarring at all, it could have caused this, or the glues just let go.


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## Victor_inox (Apr 27, 2012)

cajunner said:


> look closely at the metal plates at the top and the bottom of the magnet "sandwich"
> 
> if you see anything that looks out of round, or between slugs, you have a shifted magnet which clamps the coil solidly.
> 
> ...


 coil should be showing resistance if just magnet shifted. do you have dmm to check it?


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## ZMan2k2 (Mar 11, 2014)

I do, but the batteries are dead. Maybe I'll go buy some, and test this thing out.


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## qwertydude (Dec 22, 2008)

If the output suck, what kind of ported box was this? Did the subs share the same air space or were they separated? If they shared airspace and you wired one of them backwards this unloads the subs and you get pretty much zero output and tons of excursion which could easily bottom out those low Xmax SD-2's. One of them might have bottomed and crushed the voice coil leading to the seizure.

Another possibility is the port was tuned too high or you had a bad leak. If you didn't run a subsonic filter the subwoofers can unload on very low frequencies and also bottom out.

Working subs don't just seize for no reason.


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## Schizm (Jun 12, 2011)

The output probably ducked because the one was seized already and the one sub is less output and may be seeing double the volume it needs is my guess.



Sent from my SCH-I545 using Xparent Green Tapatalk 2


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## ZMan2k2 (Mar 11, 2014)

qwertydude said:


> If the output suck, what kind of ported box was this? Did the subs share the same air space or were they separated? If they shared airspace and you wired one of them backwards this unloads the subs and you get pretty much zero output and tons of excursion which could easily bottom out those low Xmax SD-2's. One of them might have bottomed and crushed the voice coil leading to the seizure.
> 
> Another possibility is the port was tuned too high or you had a bad leak. If you didn't run a subsonic filter the subwoofers can unload on very low frequencies and also bottom out.
> 
> Working subs don't just seize for no reason.


The subs shared the same airspace, and I had the box tuned for 40Hz. This was according to two sites 12volt.com and a box calculator site I don't remember right now. I made sure to follow the wiring instructions I googled, which were to wire each of the positive in series,one positive to the next positive and so on, and each of the negative in series, this would give me a 1ohm load, which was what I was running when each were in their own sealed box. I have a subsonic filter on the amp turned to 10Hz. The only possibility I can think of was a leak in the box, but I sealed it with enough silicone to kill a horse. I thought I had it all taken care of.


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## amalmer71 (Feb 29, 2012)

Being tuned for 40Hz leaves a lot below that frequency for the subs to unload and easily reach the limit of their excursion. Next time set the subsonic filter to slightly under 40Hz. More like 35Hz at the lowest. You won't really hear anything below the Fb of the enclosure anyway so why make the subwoofers try to reproduce it?


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## ZMan2k2 (Mar 11, 2014)

amalmer71 said:


> Being tuned for 40Hz leaves a lot below that frequency for the subs to unload and easily reach the limit of their excursion. Next time set the subsonic filter to slightly under 40Hz. More like 35Hz at the lowest. You won't really hear anything below the Fb of the enclosure anyway so why make the subwoofers try to reproduce it?


Gotcha. Well, that's why I'm here. To learn more than the basic knowledge that I have. There's no where else to go anymore, to get more than the basics, and my basics go back to '93  when I put some 6x9's in a box for my dads' Suzuki Samurai. He always joked he had the loudest AM radio on the block. I looked at the magnet, and it seems to be level with the basket all the way around, so I don't think the glue let go. I can't find my DMM to test VC resistance, so I don't know if the VC's are fried or not. The one thing I do notice, is that it's stuck in it's "resting" position. The cone is not moved in or out. I don't know if that's any indication of what might have happened?


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## qwertydude (Dec 22, 2008)

There it is 10 hz subsonic + 40 hz box tune = blown sub.

Any frequencies below 40 hz and when the subs unload and the subs will go overexcursion badly and you probably wouldn't even hear it because output would drop a lot too. That's when the subs will bottom out and seize. If you didn't smell and see a bunch of smoke before they seized most likely it was the mechanical damage of overexcursion rather than simply overpowering them.

Cone position being at resting is just coincidence. I've seen them stuck in, out and anywhere in between after mechanical damage.


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## ZMan2k2 (Mar 11, 2014)

qwertydude said:


> There it is 10 hz subsonic + 40 hz box tune = blown sub.
> 
> Any frequencies below 40 hz and when the subs unload and the subs will go overexcursion badly and you probably wouldn't even hear it because output would drop a lot too. That's when the subs will bottom out and seize. If you didn't smell and see a bunch of smoke before they seized most likely it was the mechanical damage of overexcursion rather than simply overpowering them.
> 
> Cone position being at resting is just coincidence. I've seen them stuck in, out and anywhere in between after mechanical damage.


Okay, that answers it. I screwed up. It was my first shot at a ported enclosure, and I messed up. Thanks for all the answers. This is why this place is quickly becoming my favorite site. I learned something new about my car audio selections and choices. I may stick to sealed boxes from now on, just to be safe.


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## Chaos (Oct 27, 2005)

ZMan2k2 said:


> Okay, that answers it. I screwed up. It was my first shot at a ported enclosure, and I messed up. Thanks for all the answers. This is why this place is quickly becoming my favorite site. I learned something new about my car audio selections and choices. I may stick to sealed boxes from now on, just to be safe.


It happens. A good installer is compelled to acknowledge his mistakes, so that he can apply what he has learned. 

Don't let that stop you from doing more research the next time you want to build a ported box.


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## minbari (Mar 3, 2011)

ZMan2k2 said:


> Okay, that answers it. I screwed up. It was my first shot at a ported enclosure, and I messed up. Thanks for all the answers. This is why this place is quickly becoming my favorite site. I learned something new about my car audio selections and choices. I may stick to sealed boxes from now on, just to be safe.


I wouldnt let that shy you away from ported. Ported are more efficient and can sound better than sealed. They do take up more space and you have to be more careful with the design and implementation of it, but you have more information now. try again


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## ZMan2k2 (Mar 11, 2014)

You're right. I should look at all my options, and consider ported again. Back to the drawing board.


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## humandrummachine (May 17, 2010)

Just set the subsonic filter to your port tune and you're good to go with ported boxes


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## mikey7182 (Jan 16, 2008)

I agree- don't let that scare you away from ported. Get that thing reconed and stick it back in the same enclosure. A rule of thumb with ported enclosures, or how they work, is that you typically have the least amount of excursion at the tuning frequency. Below that frequency, your excursion increases, which decreases the amount of power the speaker needs before it reaches maximum excursion, and therefore limits its power handling. This is what SSFs are for. So if I tune an enclosure to 30hz, I will usually set the SSF around 25hz with a pretty steep slope (if your slope is selectable). And you'll also want to factor in how hard you're pushing them. If they're 500wrms subs and you're already pushing them to their limits, you won't want much 'space' between your tuning frequency and your SSF. If you're feeding them half power or something, you may have a little more leeway.


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