I have been running my Tempest for about 2 years now. I am finishing my basement and would like to move to stereo subs in the new bigger space. If I buy another new Tempest now, will it be a good match for the other? I guess this raises the question both of aging of a driver and of the manufacturer's quality control/batching.
You're opening a can of worms.
Setting aside the question of burn-in and changes in the first 50-100 hours of use, there are changes in drivers. The single worst example the is foam surround, which rots after 5 to 10 years. People think,"Oh, well, then I'm okay for another X years." Not so. The surround doesn't behave like the proverbial one horse shay and come apart all in one 24 hour period--it's a slow, continual deterioration that begins the day it's manufactured. In fact--and this is something a lot of people don't realize--the surround will rot even if the driver is just sitting on a shelf. Ever wonder why you don't see any NOS Advent woofers? Trust me, you won't. They're all gone. I don't care how great a driver is--if it has a foam surround it's a non-starter in my book.
Another problem that's more subtle is heat damage in drivers that are run hard. It's not that difficult to imagine the coil melting, but a more insidious evil rears its ugly head when the magnet loses strength as a result of being exposed to heat.
Moisture can effect paper cones.
The softer glues can harden.
Etc. Etc. Etc.
Grey
Setting aside the question of burn-in and changes in the first 50-100 hours of use, there are changes in drivers. The single worst example the is foam surround, which rots after 5 to 10 years. People think,"Oh, well, then I'm okay for another X years." Not so. The surround doesn't behave like the proverbial one horse shay and come apart all in one 24 hour period--it's a slow, continual deterioration that begins the day it's manufactured. In fact--and this is something a lot of people don't realize--the surround will rot even if the driver is just sitting on a shelf. Ever wonder why you don't see any NOS Advent woofers? Trust me, you won't. They're all gone. I don't care how great a driver is--if it has a foam surround it's a non-starter in my book.
Another problem that's more subtle is heat damage in drivers that are run hard. It's not that difficult to imagine the coil melting, but a more insidious evil rears its ugly head when the magnet loses strength as a result of being exposed to heat.
Moisture can effect paper cones.
The softer glues can harden.
Etc. Etc. Etc.
Grey
keyser said:
djQUAN said:
It's not just economics. Proper surround design doesn't just involve attaching the driver to the frame with something flexible. The mass and stiffness and damping of the material (most significantly for mid and fullrange drivers) are used to terminate the resonances of the cone in order to minimize them. A low mass material is useful for this at high frequencies, and even at low frequencies foam is very easily adjusted in properties.
Rubber can rot and harden and change parameters, so it is not immune to degradation, either.
I wouldn`t rely on consistent manufacturing quality of drivers.
Sometimes it appears that even manufacturers of quality drivers change something in the fabrication process or they use different raw materials.
This means that a driver bought a few years ago do not necessarily have the same (initial) parameters or properties as the same type of driver bought today.
Not rarely these differencies can be quite substantial, sometimes so that it literally could be called another type of driver and also not rarely the "old" specsheet for that driver wasn`t changed according the new parameters or properties.
For customers this is bad thing as they never can be quite sure what they really get.
There is only one way out of this - never rely on manufacturers specs - measure everything by Yourself.
Not that I`m aware of. I wouldn`t recommend to treat foam surroundings with anything. The best way to prevent or to delay detoriation of foam surroundings is to avoid exposure to direct sunlight.
Also I partially agree it`s not always that simple.
Or why do You think that manufacturers as Scan-Speak sometimes also use foam surroundings?
I don`t think it is always a cost decision but one based on technical issues as Ron E already pointed out.
And BTW: foam is not foam. I still have Scan-Speak drivers that are 20 years old and the foam surround is in still very good condition. I have seen drivers with completely rotten foam surround after less than 10 years while just sitting around on the shelf most of their lifetime.
I was unde the impression that the foam used these days does not rot as much as it used to. Adire uses foam surrounds on even their most expensive woofers, like the Tumult. This is from the Tempest whitepaper:
The Shiva has been around for a pretty long time now, and I have not heard any reports of surround degradation. Not saying it doenst happen, just that if it was a big issue I can't see well regarded companies like Adire not using rubber for a $500 driver like the Tumult.
The Shiva has been around for a pretty long time now, and I have not heard any reports of surround degradation. Not saying it doenst happen, just that if it was a big issue I can't see well regarded companies like Adire not using rubber for a $500 driver like the Tumult.
Leadbelly:
How's this for a thought? Measure the Thiele-Small specs of your Tempest now. See how close they come to the published specs.
If they come reasonably close, then there has not been much significant change from when it was new.
If you really want to cut corners, calculate the internal volume of your present sub box-plug any vents. Measure the Fc of the box-easy to do with a free online tone generator. Calculate the Fc using WinISD or any other program for your box according to published specs. If the two are close, I would just order one new Tempest.
Here is a free online tone generator:
www.satsignal.net => Audio Tools
Just download and run from your soundcard to your sub via inexpensive cables available at Radio Shack or any store that sells audio cables.
If you need instruction s on how to find Fc in the closed box, will be glad to provide, (though judging by your posts I am pretty sure you know).
http://sound.westhost.com/tsp.htm
How's this for a thought? Measure the Thiele-Small specs of your Tempest now. See how close they come to the published specs.
If they come reasonably close, then there has not been much significant change from when it was new.
If you really want to cut corners, calculate the internal volume of your present sub box-plug any vents. Measure the Fc of the box-easy to do with a free online tone generator. Calculate the Fc using WinISD or any other program for your box according to published specs. If the two are close, I would just order one new Tempest.
Here is a free online tone generator:
www.satsignal.net => Audio Tools
Just download and run from your soundcard to your sub via inexpensive cables available at Radio Shack or any store that sells audio cables.
If you need instruction s on how to find Fc in the closed box, will be glad to provide, (though judging by your posts I am pretty sure you know).
http://sound.westhost.com/tsp.htm
I remember a thread here a couple of years ago wherein a member went on a rant because I'd said impolite things about foam surrounds. Somehow he seemed to be of the impression that it was--or should be--acceptable that a part would self destruct after five or ten years. My point of view is that I'll put up with that sort of thing out of tubes, but only because they offer sound qualities that solid state simply cannot provide. I've never heard a credible argument that foam has any realistic advantage as far as sound quality, and it certainly doesn't as far as reliability. Arguments that it might provide for more Xmax are unconvincing, given that there are numerous examples of rubber surround drivers that have high Xmax.
Incidentally, companies will sometimes change the parameters of drivers without warning. It would help if they would give the newer driver a different designation, but that doesn't always happen. KEF pulled this stunt with the B-139 back in the '70s.
Grey
Incidentally, companies will sometimes change the parameters of drivers without warning. It would help if they would give the newer driver a different designation, but that doesn't always happen. KEF pulled this stunt with the B-139 back in the '70s.
Grey
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