Help, Shiva sounds terrible

[weddie]

Help, I have a Shiva Mark IV, with a Rythmic 350 amp with the shiva in parrall so its 4ohms. I also have the setup in a 142 liter box. Heres my problem - After turning the amp up to 50%, with the crossover at 40hz and the phase at 0, i was watching the Italin Job. During the vault explotion and the truck drop explotion, the Shiva made huge popping sounds. Note that my reciver was not turned up very high, at most -30Db. I then experimented, aka tested other movies and songs, with the Shiva only to find that it sounded terrible. I took it out and check it, and i found that the spider had come loose. I was wondering if my voice coils are burnt and if so what should i do. Buy another shiva or send it in for repairs. Thanks.

[paulspencer]

Assuming you haven't subjected it to extreme abuse or mishandling, then it should be covered in warranty. This is a matter to discuss with the supplier.

[bhg41088]

yeah, if the pider came loose id say its covered under warrenty.

[BillFitzmaurice]

Generally drivers are not covered under warranty for excess power. In your case ths spider tore from overexcursion, which may be from excess power or may be caused by an incorrect box design. Is your box vented? That's the usual cause for excess excursion. Even if you luck out and the driver is warranteed you need to correct the source of the problem or it wil reoccur.

[f4ier]

Both voice-coils should be alright. I had an accident once, my amp blew up and shorted its positive supply rails to 1 of 2 coils. Imagine the horror seing the cone pushing all the way out The Shiva was fine, coils and suspension survived

But I'd still have it checked out just in case.

Cheers!

[weddie]

Ok to answer some questions, My shiva is in a 142 Liter box which is vented, 12 inch flared at both ends.

I've done some more testing and when i hold down the spider, the shiva makes a rattling noise, plus it doesn't seem to have the same amount of power, its very weak. Is this burnt voice coils?

[BillFitzmaurice]

Ok to answer some questions, My shiva is in a 142 Liter box which is vented, 12 inch flared at both ends.

I assume that means a 12 inch long duct, not diameter, but in either event your box size is far too large for a vented alignment with this driver and that's why it was damaged; there isn't enough compression to prevent overexcursion. The noise you hear is the voice coil rubbing against the pole piece since the spider is no longer holding everything in alignment. The driver is irretrievably blown and will have to be reconed, which hopefully the manufacturer will do at no charge. Do not mount the repaired driver in that box unless you remove the duct and seal it tight.

[weddie]

The alignment was afford through adire, there are directions on their website for the box. But anyways, could I just stuff the box to compensate, or should i just build a new box. If I can stuff the box, should 20% full of polyfill work?

[paulspencer]

Originally posted by BillFitzmaurice
your box size is far too large for a vented alignment with this driver and that's why it was damaged; there isn't enough compression to prevent overexcursion.

This is one of the recommended sizes included in the Adire vented alignements. This is an EBS and should be fine if tuned at the correct point. Now if you model this however, a box of this size doesn't seem to perform as an EBS, and this has puzzled me for some time.

Now having a look at this in Subwoofer Simulator I can see how you could push this driver too far with that amp very easily. I've shown 25V which into 4 ohms is ~150 watts. As you can see it is pushed to xmax at about 27 Hz. It is more of a concern here than with the LFE use. (assuming rumble filter)

Here is a chart (output is into half space.) Excursion is also shown in red.

[tiroth]

Actually Bill this sounds like the Adire-recommended 142L EBS alignment. The port is 12" nominal but that doesn't include the flares; if memory serves it is supposed to equivilent to a 17 inch straight port (or in that arena)