RSdC124 Problems After a Car Accident

[eulogious]

Howdy all,

So I finally got around to installing my stereo into my subaru after totalling my other one a few months back, and when I go to hook up the sub, it's not loud AT ALL. So after doing some leg work, I test the ohms on the sub, and it reads 8 ohms! I wired it up for a 2 ohm load. So just to make sure I pulled the sub out, and sure enough it's wired in parallel for a 2 ohm load. So I test each voicecoil individually, a one of the is at 7.5ohms, and the other is at 8.3ohms

So at this point I am pretty sure I am fucked, but I just want to make sure my assumption is correct so I will ask the obvious... My sub is toast, right? And probably from flipping my car over doing 70mph down the freeway, right? I am pretty sure, but if someone could verify that for me, I would appreciate it.

Meh, at least I have another 12 I can use, but it's a fostgate Stupid car accident.

Thanks all.

[Jacampb2]

Well, something is wrong, but I can't think of one reason why the dc resistance would increase. The resistance is for the most part determined by the material on the conductor making up the coil, the cross sectional area of the conductor, and the length of the conductor. If it were to short between windings, the effective path should be shorter and the resistance lower, if you were to break a winding, it should go open... I guess there might be some possible way it happened, but you wouldn't think that both coils would be so close...

Does the cone still move freely? Did you inspect the tinsel leads closely? I just don't think it is likely that an accident would have damaged the VC itself. If anything, I would have expected a collision to have possibly caused the magnet or pole piece to shift and pinch the VC in the gap. I have actually had that happen in shipping two times now...

Good Luck,
Jason

[eulogious]

The cone moves freely, and it does play, it's just not loud at all. My fostgate puts it to shame, and that is saying something. I also inspected everything that I could see, and it all look intact. The wires hadn't even separated inside the box.

I too am baffled on why the resistance would increase, but it surely did. I measured it multiple time to make sure I wasn't THAT high, But what I do know is that it worked great before the accident, and the first time I play it since the accident it sounds like crap, and the resistance went up on it. Well, I turned it on to see if the amps and everything still played when the car still "ran", but I didn't stress it at all. Just turned it on, saw all the lights turn on, turned it up a little to hear some noise and I did, so I turned it off. So it worked before the accident, just not after. Don't know if that helps at all...

[kg1961]

The cone moves freely, and it does play, it's just not loud at all. My fostgate puts it to shame, and that is saying something. I also inspected everything that I could see, and it all look intact. The wires hadn't even separated inside the box.

I too am baffled on why the resistance would increase, but it surely did. I measured it multiple time to make sure I wasn't THAT high, But what I do know is that it worked great before the accident, and the first time I play it since the accident it sounds like crap, and the resistance went up on it. Well, I turned it on to see if the amps and everything still played when the car still "ran", but I didn't stress it at all. Just turned it on, saw all the lights turn on, turned it up a little to hear some noise and I did, so I turned it off. So it worked before the accident, just not after. Don't know if that helps at all...

can you show pics of the sub? if both vc are in and around 8ohm you can't get a 8ohm load? reverse one of the set of wires from postive and neg to see what happens
I agree a car crash can't make the sub have differnt ohms?

[Rold Gold]

I just can't wrap my head around this.........
Over the years I seen the death of MANY woofers...... Everything from completely siezing to blowing the cone clear off the frame....... But I've never heard of this issue.......

Alright......Someone email Morgan.........

[eulogious]

Ok, sorry for the slow response, had some shit go down, *sigh*

Anyways, some photo's:









As you can see, the sub visually looks fine, nothing wrong with it. At least from what I could tell. I have inspected it a few times hoping to find something obvious, but I am not seeing anything out of place.

I will also add that all the gear was stored in doors in my apartment, in my dinning room, so all the gear was stored fine. I also pulled all the gear the same day that I got the car home, which was a day after the accident, so the gear wasn't exposed to anything weird like that either.

I have no idea why it could be doing this, but as you can see, each vc is about 6.5ohms now, so it's been varying by quite a bit. It's very strange.

I am just sad that my nice sub doesn't work anymore That and my wife is sad because I am using her sub now (it wasn't installed so I didn't steal it from a working install, I am not THAT big of a dick ). I just wish I understood why this happened… This is seriously becoming the install from hell, I tell you what

[Kurt Wild]

Let me venture a guess or two. First thing, your ohm meter might be giving a false reading. Check with another sub.

Second, now this is a long shot.. I think I read or was taught somewhere that a heavy blow on a permanent magnet can actually knock the magnetization out
So if the magnetic field in the sub motor has decreased, this would explain why its not loud anymore.

[Jacampb2]

I have a bunch of HF meters like the one you show, I bough them to make panel meters and for other projects. Try this, short the meter leads together and read the resistance, then subtract that from the numbers you just showed us. My HF meters all have more than a few ohms in the leads themselves, they are cheap- the meters themselves are not bad, but even expensive meters don't do well with low resistances. There is always lead resistance, and it is rare to have a meter that allows you to zero it.

Also, if the batteries are not brand new in the HF meters, the resistance is going to be off. I think their reference supply design for those meters is lacking a little bit-- but what do you expect for $2.99 I'm not knocking your choice in meters, remember, I like to use, build, and rig shit from whatever I can find, and that means I do quite a lot of shopping at harbor freight. Just keep in mind that there will be limitations, and try to determine what they are and adjust for them.

What Kurt says is true, a permanent magnet can be de-magnetized by a sharp blow, but AFAIK, it has to be pretty much directly to the magnet. I have never heard of it happening to a magnet that large, but I suppose anything is possible.

I honestly doubt the sub has an electrical problem. Is it 4 ohm dvc or 2 ohm? DC resistance is *almost* always higher than the impedance of a driver, you cannot measure the actual impedance with a multimeter.

Good Luck,
Jason

[kg1961]

top pics show dvc 4 ohm

[stipud]

Hrmmm definitely a weird issue. I am not really surprised the RSDC doesn't sound as loud as a Rockford sub (they are biased for higher output on higher bass, but lose the low end battle pretty severely). Have you tried using your multimeter on the rockford sub to see if the meter is reliable? With those cheap meters, they tend to go quite badly out of calibration within a year or so, even with fresh batteries.

[eulogious]

Alrighty,

Thanks all for the suggestions so far. I did test the fosgate sub with the HF meter, and it read 2.3, so it was in "spec". Also, the HF meter wasn't the first meter I used to test the sub, it was just the one I had handy when I took the pics.

The first time I took a reading from the sub, it was in the double digits so even if the HF meter is off, it's not off by that much.

So fast forward to now... The sub works just fine now. I wired it back up like I had it and it read 2 ohms, just like I wanted. I can assure you this was not the case right after I installed everything and tried it out.

Here's the other part of the story that has come to light after I posted this... It seems that there is something wrong with my zx500. If I test the voltage output of the amp on the terminal with no load, it reads and puts out the proper voltage. But as soon as I put a load on it like the sub, the voltage goes all wonky. So could this mess with the sub?? I found this out while testing different things to figure out what is going on.

So right now I have my 400.2 powering my rsdc, and it sounds a lot better now. Still this is very strange since it took a few days for the sub to get back into normal tolerances.

I hope this all makes sense, I am really tired and can't compose my thoughts, so hopefully the above rambling made some sense

[stipud]

Define wonky? It is not unusual for voltage to sag when a load is attached.

[ttocs]

technical terms confuse him.

[eulogious]

Ya, I was just confused and totally out of it yesterday.

Ok, now that I am more with it, here it goes...

With my zx500, when I play a 50hz test tone with no sub connected to it, it will put out about 31.5v when bridged, and about 15.5v on each channel, which is what I want to test it, about 500 watts. When I connect my sub up and then play the test tone again, the voltage drops down to about 6v when bridged, and jumps around from 6v to 12v or so randomly. My 400.2 does not do this. So thats what I mean by wonky. I am going to hook up the zx500 again here soon and see what happens and I will take notes about this as well.

It been working great for the last few days now that the 400.2 is hooked up...