Was this supposed to happen...I doubt it

[alliclaytor]

So I have been following the Bass Tracks thread on this sub-forum...and really liked the high quailty tracks that the mentioned website had. I played the train on my RB-75's and it sounded good. Then I thought, "I bet the reason why they have these tracks on a subwoofer site is because of the bass." So i put the tracks on a disk and took them to my living room where a franken-sonosub (15" TC-2000) lay on its side. I played the track and slowly increased the volume to what I would consider "real life" levels. Lots of bass, lots of excursion, lots of rumble...sounded good. I walked away from the sub so I could listen to it from a distance and all of the sudden I heard a high-er pitched POP POP POP and I immediatly ran over and turned the volume off. I felt the sub's metal "cone" and it had a raised concentric circle in the aluminum maybe a 3/16" high. The sub still plays fine...but did I just overdo the sub with the excursion, or did the force of the driver pushing and pulling deform the cone? Also...is this a problem going forward with the reproduction of the sound with the raised section? Thoughs are welcome!

[michael hurd]

You bottomed the TC 2000 out, and when it hard bottomed it bent the cone. You will need a new top assembly, this is why you should have a high pass filter. ( subsonic filter )

[WMcD]

I'm pretty sure that you have mechanically damaged the woofer by overdriving it. There is a cylindrical voice coil "former" which is glued to the diaphragm to make it move. The former and the electical winding wound upon it moves in the magnetic gap of the magnet. The ring shaped dimple is probably the former mushing (that is a technical term, smile) the diaphragm.

I've recounted this before, I lost a bass horn driver with a Telarc disk, the one with warnings. But I've also flirted with the dragon of distruction by driving the same unit with a signal generator at the resonant frequency of the system. When driven to mechanical limits, the woofer makes a knocking or klanging sound (could be the basket) when the diaphragm hits the magnet. I was very surprised at the sound because it is not something expected from a woofer.

That may have been what you hear, even if the dimple was caused in part by the raw acceleration - force.

I suspect that when people hear crackle or static on a bass enhanced recording it is such a bottoming out, or the amp has clipped at frequencies we can not hear.

The problem with mega bass recordings is that they will cause very great excusions of the woofer system at sub sonics. You don't hear the signal but it is pounding the mechancial system to an inch of its life, and beyond. I expect that sophishicated subs have monitoring systems to prevent this. A related issue is that at deep bass, the compression spring of the box itself is a heck of a mechanical load.

Gil

[TheEAR]

Dont you watch the cone excursion and test before trying to play back very low frequency material ?!?! One thing is 100% sure,you ahve no subsonic filter or it is not set correctly(slope and frequency).

To bend the cone on these drivers means bottoming VERY hard. Going way beyond Xmech...since it canno9t go beyond...CLAK..! The weakest point gives.

Plain and simple,DIY subs have to be used with care as they are often lacking limiters(amp output level and FILTERS).I NEVER ever bottomed a driver,as I know what each driver can and cannot do very well.

The deformation makes the come weaker,so be careful with high OUTPUT from now on. The cone is a dish,you deform the dish and yes it will work...do not try to bottom again.

[michael hurd]

While it MIGHT still work... the electromagnetic center is now offset by the distance it has bent. You need a new top assembly. TC is in the midst of a transitional stage, FI car audio might be able to build you a new top assembly for your motor.