My sub goes "tock" when it should go "thud"

[BoomieMCT]

I've been working on two matched subs with 12" Titanics in 1.6 cubic foot sealed enclosures powered by 500 watt BASH amps. I've just now finished the enclosures and mounted the hardware. One of the subs sounds great. The other sounds grainy - almost like there is something hitting the driver when it is moving. I took it apart and verified no wires or anything were in the way but the sound did not go away. I swapped the amp to the other driver and it sounded fine (so it's not the amp).

Tapping on the cone of the "good" one produced a nice low thud sound (like every sub I've had). The "bad" driver produces a much higher, stiffer "tock" sound. The "bad" sub sounded bad the moment I put it in (this isn't a problem that developed).

Does anyone have any idea what could be wrong? I can see no visible damage to the bad driver.

[Darren]

My last test would be to put the bad driver in the enclosure that the good driver is currently in. If it still sounds bad then I think it is.

[BoomieMCT]

I'm 95% sure it is the driver. I just want to know what happened? My levels were set low and the amp checks out as okay. I guess it could be a manufacturer's fault but I want to make sure.

[thxgoon]

Check to make sure the driver moves freely by hand. If there's any resistance or if it is accompanied by a scratching sound then it is bad.

[BoomieMCT]

thxgoon wrote:

Check to make sure the driver moves freely by hand. If there's any resistance or if it is accompanied by a scratching sound then it is bad.

There is resistance. I'm sure it's bad and the driver needs to be replaced. What I want to know is *what* is wrong? The more I learn now the more I'll know in the future.

[thxgoon]

There is a very tiny gap between the voice coil and the magnet surrounding it. If the voice coil gets deformed in any way (melting, bottoming) it rubs against the magnet. That is the scratching/resistance you feel.

Does the 'normal' woofer also share this resistance or is it unique?

[BoomieMCT]

thxgoon wrote:

There is a very tiny gap between the voice coil and the magnet surrounding it. If the voice coil gets deformed in any way (melting, bottoming) it rubs against the magnet. That is the scratching/resistance you feel.

Does the 'normal' woofer also share this resistance or is it unique?

Nope. The one that is running has a nice deep resonant sound (thud) when tapped and moves smoothly and without resistance. The "bad" one sounds like it is slapping on something and does not move freely - it feels grainy.

I hope the vendor I bought this from can fix or replace this for me. The problem was immediate.

[thxgoon]

Ya I'd get in touch with parts express, I'm sure they'll work something out. Sounds like a bad woofer. Bummer...

[BoomieMCT]

Well, it looks like Titanic #2 is going back to Ohio (looks like PE is going to take care of me). I can't wait to get a replacement!

[BoomieMCT]

Just for completeness - this got replaced quickly with little fuss or muss. The new driver is breaking in nicely. I just watched "Casino Royale" with both 12"ers running last night - it was quite impressive.

If only they would break in fast so I could EQ them now!

[brucek]

If only they would break in fast so I could EQ them now!

Will they really change that much?

brucek

[BoomieMCT]

brucek wrote:

Will they really change that much?

brucek

I'm not really sure. I've gotten in the habit of breaking stuff in before measuring it for so long it just seems natural to me.