Blown driver?

**cynical2** · **02-20-08, 09:24 AM**

I have a budget (Audiosource SW-12) subwoofer that's several years old. I think the driver may be damaged. Is there an easy way to test this with a multimeter? I expect this will turn into a "quasi-DIY" project, with a replacement of the driver and re-using the enclosure and plate amp.

Jim

**thxgoon** · **02-20-08, 10:31 AM**

What makes you think it's blown? One easy test is to just push on the woofer cone and move it in and out. If you hear scratching or scraping something melted

**ccdoggy** · **02-20-08, 12:44 PM**

you could stick a multimeter to the terminals and see what resistance you get. either could be way too low (shorted) or too high (burned).

**avin_r** · **02-20-08, 02:42 PM**

moo baby moo, I have an old(about 2 years) Infinity Kappa Perfect 10.1 and when I push the cone in I hear subtle scraping sounds. It does not get used much any more but when I use it, it sounds okay.

**ccdoggy** · **02-20-08, 02:53 PM**

subtle scraping could be due to you're uneven pressure on the cone, If it is then you are fine.

**avin_r** · **02-20-08, 06:08 PM**

I mean the thing sounds fine, the enclosure isn't the greatest but I have had it playing frequencies below what it's tuned to, I think that might be the culprit.

**cynical2** · **02-20-08, 07:57 PM**

Well, the subwoofer stopped working. I found that the fuse was blown so I replaced it. The fuse blew again. So, I took the plate amp off and smoke poured out of the enclosure. Once the smoke cleared, neither the driver or amp was giving off smoke...so I'm not sure where it was coming from.

I unhooked the driver and put a fuse in the amp. The fuse still blows. So, I'm assuming that the amp is bad (unless it automatically blows the fuse when unloaded...which I wouldn't think).

For the of it, I checked the driver out, just in case there was also a problem with it too. I pushed on the cone...no rattling or scratching. But, I put a multimeter on it and got a resistance of < 1 ohm (0.8 IIRC). I've never even had one of my speakers apart (and never built one)...but I assumed that I'd get something near the 8-ohm impedence the speaker is rated for.

So, what's the verdict? Are both the amp and driver bad, as I suspect...or is one of them behaving as expected, and I just don't have the knowledge to realize it?

**thxgoon** · **02-20-08, 08:49 PM**

I would think the driver should measure higher than 1 ohm. My guess is something happened in the driver causing it to short and that blew your amp over time. Bummer...

**ISLAND1000** · **02-20-08, 10:09 PM**

I can't think of a driver used in a commercial home theater subwoofer that had a 1ohm voice coil including the Audio Source SW-12. The amp is obviously bad and (blowing fuses) and my guess is the driver is bad also. But the box is still good! Parts Express has a couple of plate amps you could build into your existing box along with choosing a better 12 " driver replacement. You'll have to do some modeling with the drivers, box size, and length of port. That'll be as good as an entire DIY project. We'd all like to see you do it.

**cynical2** · **02-20-08, 11:54 PM**

Quote:

ISLAND1000 wrote:

I can't think of a driver used in a commercial home theater subwoofer that had a 1ohm voice coil including the Audio Source SW-12. The amp is obviously bad and (blowing fuses) and my guess is the driver is bad also. But the box is still good! Parts Express has a couple of plate amps you could build into your existing box along with choosing a better 12 " driver replacement. You'll have to do some modeling with the drivers, box size, and length of port. That'll be as good as an entire DIY project. We'd all like to see you do it.

But...but...I don't know anything about this modeling of which you speak.

In all seriousness...thanks for the help from everyone. Stinks that both components are ruined.

Well, with the driver and amp removed, I calculate the volume of the cube at 2.18 cu ft. That doesn't take away any volume for the two 4" ports that come out of the front of the sub (same side as the driver).

So what is the proper approach for this project, if I want to re-use the enclosure? Is this the "WinISD" modeling? I guess I need to start reading and trying to figure out how to do it, eh...

Are all plate amps the same footprint with the same screw hole locations, etc?

Is a plate amp a better value or an external amp (like one of the Behringer models)?

**ISLAND1000** · **02-21-08, 10:36 AM**

Quote:

cynical2 wrote:

But...but...I don't know anything about this modeling of which you speak.

So what is the proper approach for this project, if I want to re-use the enclosure? Is this the "WinISD" modeling? I guess I need to start reading and trying to figure out how to do it, eh...

Are all plate amps the same footprint with the same screw hole locations, etc?

Is a plate amp a better value or an external amp (like one of the Behringer models)?

LOL, don't be so . . . . cynical. You can do this.
Yes, the modeling is done with the WinISD program. It is a free download. It is a complex program and it's design results are pretty much accurate. It's easy to use and it becomes second nature once you read the "help files". If I can do it for sure so can you.
"A better value" . . . . hmmmm obviously you've been reading some of these threads. I guess you should start by asking yourself how important is it to have the subwoofer with it's own attached amp? I've always used power amps and passive subs but that's just me. The Behringer amps are excellent for subs and will look good in amongst your other equipment. It'll kinda make you look like an . . . . . "electronic practitioner" of some sort.

**TheEAR** · **02-21-08, 06:04 PM**

For those who want the most simple and crude woofer tester....

...the 9V battery.

If it arcs the VC is(minuts as these cells are low current and cannot deliver much...unlike the sub-C cells used in high amp draw apps )...shorted...

You hear a pop and the driver makes a sound...the VC is not toasted. So the amp failure is not driver related.

**cynical2** · **02-22-08, 08:58 AM**

Quote:

TheEAR wrote:

For those who want the most simple and crude woofer tester....

...the 9V battery.

If it arcs the VC is(minuts as these cells are low current and cannot deliver much...unlike the sub-C cells used in high amp draw apps )...shorted...

You hear a pop and the driver makes a sound...the VC is not toasted. So the amp failure is not driver related.

Sorry, I'm not following. Can you explain exactly how I would do this (pretend you're talking to a child over the phone

).

**TheEAR** · **02-22-08, 10:40 AM**

Quote:

cynical2 wrote:

Sorry, I'm not following. Can you explain exactly how I would do this (pretend you're talking to a child over the phone

).

The 9V battery has a PLUS and MINUS. You touch the battery + with the speakers's +...follow me...and the battery's - with the speakers -.

You can reverse,cannot damage anything,the cone/VC will move backwards. On speakers with stiff suspension and presenting a heavy load to the amp...you may not even see the cone move. Just a POP.

Like I said this is a caveman quick N easy method.To test if the VC is shorted,as the juice (voltage and amperage the 9V cell delivers are low).

**thxgoon** · **02-22-08, 11:05 AM**

The fact that he got a non-zero reading with his multimeter suggests that there is not a complete short circuit so it could go 'thump' and still have something wrong. A reading this low does suggest something is wrong so I'd go with the meter reading.

**TheEAR** · **02-22-08, 11:52 AM**

Of course,the 9V battery check is like I have stated..numerous times a CAVEMAN QUICK TEST.

**cynical2** · **02-22-08, 11:34 PM**

thanks for the clarification, Mr Ear! And, thanks for taking me literally when I said to pretend you were talking to a child!

Even I was able to follow the 9V caveman test!

Well, off to grab my wife by the hair and drag her around the house before I try this...gotta get in the mood!

Even though it sounds like the result won't be definitive, I just can't resist a least trying it.

BTW, what would happen if I unhooked the speaker wire from one of my mains and attached it directly to the sub driver terminals? Isn't that doing the same thing as just using the speaker-level inputs on the sub? I assume that when the speaker-level inputs on the amp are used, then the amp is simply passing through (other than the crossover). Would that not tell me if it works? Or is my ignorance showing through, as it does on occasion?

**ISLAND1000** · **02-23-08, 12:17 AM**

I can see you have lingering doubts as to whether or not the amp is dead. The problem with your pass through hookup idea is it might blow that speaker too. At this point you don't know where in the amp the smoking and burning took place. It might be where the terminals are located and an electrical short might have joined together some pieces and or wiring that were not meant to be joined including the speaker terminals.
Instead, take the amp out and take a good look at all the various resisters, capacitors, potentiometers, transformers, etc. Look for burned parts or changes in color. Be a techno-detective and THEN throw the **** thing in the garbage and get on with the REBUILD!!!

**thxgoon** · **02-23-08, 12:45 AM**

Quote:

cynical2 wrote:

BTW, what would happen if I unhooked the speaker wire from one of my mains and attached it directly to the sub driver terminals? Isn't that doing the same thing as just using the speaker-level inputs on the sub?

Yes, but be very careful.. if there is something wrong with your driver you run the risk of damaging your main amplifier.

**cynical2** · **02-23-08, 10:33 AM**

I did the 9V battery deal Mr EAR recommended...and as soon as I touch it to the contacts on the driver (and every time I do so), I hear a clicking sound. It happens immediately...no movement of the cone that I could see. The sound is similar to a solenoid firing.

After doing it several times, the 9V starts to get warm (my assumption is that that's normal and due simply to the load being placed on it??).

Does that behavior mean anything?

Phil, I'm assuming at this point that the amp is dead since it continues to blow fuses, even when in the "Off" position, with the driver unhooked. My question at this point is if the driver is good...or not. I have the sub apart...maybe I'll do as you recommend and take the amp apart to see if I can tell what failed. Maybe that will give someone more brilliant than me some insight into what happened.

I don't know that I want to risk tearing up an amp in my main receiver by hooking up the mains' speaker wire to the driver...so thanks for the warning thxgoon! In hindsight, it makes perfect sense.

**thxgoon** · **02-23-08, 11:22 AM**

Quote:

cynical2 wrote:

I did the 9V battery deal Mr EAR recommended...and as soon as I touch it to the contacts on the driver (and every time I do so), I hear a clicking sound. It happens immediately...no movement of the cone that I could see. The sound is similar to a solenoid firing.

After doing it several times, the 9V starts to get warm (my assumption is that that's normal and due simply to the load being placed on it??).

Those results seem to confirm your meter readings. If you were reading a very low resistance <1ohm the woofer is going to require a very high current even at 9 volts which is why the battery got warm. The same thing would happen if you shorted the battery by connecting the contacts with a wire. Also, given that the cone didn't move the current is not doing any usefull work, indicating both a problem with the woofer and a near short circuit senario. IMO the woofer is bad. I've been trying to think of a test bed senario where you could test this without harming another amplifier... but haven't been able to think of one.

**cynical2** · **02-23-08, 01:24 PM**

Quote:

thxgoon wrote:

Those results seem to confirm your meter readings. If you were reading a very low resistance <1ohm the woofer is going to require a very high current even at 9 volts which is why the battery got warm. The same thing would happen if you shorted the battery by connecting the contacts with a wire. Also, given that the cone didn't move the current is not doing any usefull work, indicating both a problem with the woofer and a near short circuit senario. IMO the woofer is bad. I've been trying to think of a test bed senario where you could test this without harming another amplifier... but haven't been able to think of one.

Thanks for the insight...

Yeah, I wish I had an old receiver or amp that I could use (that I didn't care about), so I could test it...

**cynical2** · **02-25-08, 06:48 PM**

Took the amp apart...everything looked OK to me. Still, I assume it's bad since it's blowing fuses with no driver hooked to it.

As far as the driver...the resistance of < 1 ohm seems awfully low. So, I assume it's also damaged.

Looks like I'll either be buying a sub that's ready-to-go (used or new), rebuilding this one, on starting a new build. I haven't decided which way to go at this point...

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