'Oil-Canning' What is it?

[killersoundz]

Reading a little about 'oil canning'. Apparently when a speaker is in too small of an enclosure. What is it, how, and why?

[Wolf]

Re: 'Oil-Canning' What is it?

Reading a little about 'oil canning'. Apparently when a speaker is in too small of an enclosure. What is it, how, and why?

AFAIK, it's only been a problem with the RSS series of sub drivers from Dayton Audio. I've not heard of any other series of drivers doing it. The oil-canning can only be a problem for metal-cones though.

The RSS-HF drivers when used in too small of a sealed box, have too thin of a cone to maintain rigidity under the substantial stresses of internal vacuum and pressure in said sealed box. The RSS-HO drivers have a thicker cone, and can take substantially more stress than the HF drivers can.

The thin aluminum cone and dustcap will either flex, or pop, induced by the internal stresses in a sealed box, and it is extremely audible at moderate-to-higher output levels. I don't know that there has been a measurement or anything done with a computer-based measurement system to try and capture the threshold of the stress the HF drivers have reportedly encountered. If there was a measurement, it would be a definite plus to be seen.

All this said- I experienced it with the RSS265HF in a very small sealed volume, and it was not pretty. The RS315HF has also bee reported to have this dilemma, albeit at higher levels than the RSS265HF.

The remedy is to keep the HF subs operating in a large enough sealed box, or an aperiodic, vented, or PR box.

Later,
Wolf

[Taterworks]

Re: 'Oil-Canning' What is it?

There are other, similar drivers with aluminum cones that will work better in a small sealed box. The one that comes to mind is the AE Speakers AV12, which is all-around a better driver than the RSS 12" platform but is more expensive, and you may be facing a wait period, since the proprietor of AE Speakers builds each driver by hand (though they are very consistent and match the published measurements very well).

[killersoundz]

Re: 'Oil-Canning' What is it?

So is it safe to say that a very small sealed enclosure size causes a distortion even with regular paper cone woofers?

[Wolf]

Re: 'Oil-Canning' What is it?

So is it safe to say that a very small sealed enclosure size causes a distortion even with regular paper cone woofers?

I can't prove or even list criteria or tests that were done to state otherwise, but in theory, this would indeed be possible. The stiffness/thickness of the diaphragm/cone is the thing to examine.

Later,
Wolf

[killersoundz]

Re: 'Oil-Canning' What is it?

I can't prove or even list criteria or tests that were done to state otherwise, but in theory, this would indeed be possible. The stiffness/thickness of the diaphragm/cone is the thing to examine.

Later,
Wolf

I believe so, I happen to have an experience where an unusually small sealed enclosure was used for a guitar speaker and aside from the obvious response curve, the speaker had some unusual distortion, it would even make 'ghost notes' under some circumstances, where the harmonic distortion would be more prominent than the source, I assumed. This is with a woofer that has a very thin paper cone.

[benchtester]

Re: 'Oil-Canning' What is it?

So is it safe to say that a very small sealed enclosure size causes a distortion even with regular paper cone woofers?

I don't know about "oil-canning" and paper. There is a theoretical problem called "air spring distortion": as the cone goes inward, the air is compressed into a smaller volume, but as it goes outward the volume is getting bigger. This is non-linear (see note below for explanation). S. Linkwitz offers a calculation of this in his spreadsheet:

http://www.linkwitzlab.com/closed-box1.xls

Look for under cell U14


Note: Let's grossly exaggerate to make it easy to imagine and say that the cone going inward reduces the volume by half then pressure goes up 2.00 times (29.4 psia) or; if it goes out the same volume pressure drops to 0.66 times (9.8 psia). In practice, it is much less volume change and close to linear. But it can be a problem below 200 hz with small sealed enclosers.

[wlb]

Re: 'Oil-Canning' What is it?

It comes from the sound that the old style oil can sounded like when you pushed in the bottom of the can to pump oil out. Some metal speakers sound like that when the cone warps from over driving. The guys before me told you witch models are prone to it.