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Finally, some action... (Read 18410 times)
Lee in Arkansas
Ex Member



Re: Finally, some action...
Reply #30 - 06/14/06 at 19:15:10
 
It doesn't move the exact same amount of air, it also doesn't move it in the same pattern. That inverted bucket is a good example. The front of the cone makes a pressure wave, while the back is more of a dispersion, by shape. What happens when you put an inverted cone into water, it pushes the water aside. Turn it over and it cups it. I see your point.

It moves almost as much air, slightly less because the front can use the space over the VC, whereas the back can't. Also, can't forget the baskets issues with airflow.

Now think about it like this....
Which puts more equal pressures on the cone, firing the front(has more 'pressure' as we've described) in a perfectly square empty space, or into a perfectly square space with a pice in the middle that covers the cone and half doesn't? I'd that 'obstruction' be on the 'weaker' end of the speaker, so as to raise the power handling of the driver. Don't forget that air flowing over the motor keeping it cooler.
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Lee in Arkansas
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Re: Finally, some action...
Reply #31 - 06/14/06 at 20:25:08
 
Someone correct me if I'm stupid and don't know what I'm talking about (a.k.a. wrong). Grin
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bassboy
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Re: Finally, some action...
Reply #32 - 06/14/06 at 21:44:21
 
If you check the white papers, the whole point of the DB is unconventional but very effective motor cooling, coupled with the unrivalled cone control provided by the sealed chamber.

If the motor is inside the sealed chamber you effectively reduce power handling by a huge amount by completely undermining the design that makes this box special and differentiates it from all the other fourth order bandpasses.  Instead of cooling the driver with airflow from outside, you let the voice coil bake in a sealed oven, heated by itself.  Of course this makes much more difference at higher power levels.
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« Last Edit: 06/14/06 at 21:50:26 by bassboy »  
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60ndown
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Re: Finally, some action...
Reply #33 - 06/15/06 at 01:15:52
 
[quote author=bassboy  link=1147870641/30#32 date=1150317861]
If the motor is inside the sealed chamber you effectively reduce power handling by a huge amount . [/quote]

hhmmm?? im no scientist, but if the driver is rated @ 150 wrms, why would installing it into a sealed box 'reduce' its power handling?
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bassboy
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Re: Finally, some action...
Reply #34 - 06/15/06 at 01:44:57
 
The whole point is that you can feed it significantly more than the rated 150 watts because the voice coil won't melt because it is air cooled if the voice coil is NOT in the sealed chamber.

Put the voice coil in the sealed chamber and get your 150 watts or put the voice coil in the pathway of the outside air and get a lot more power handling and a lot closer to xmax and mechanical failure before the voice coil overheats and starts rubbing in the gap or completely fries and results in an open circuit.

Read the white paper and understand that the initial problem was overheating of the voice coil before the driver could reach it's mechanical limits.  With experimentation, the Decware design eliminated this problem and now the limiting factor in any given DB/driver combination is probably going to be xmax, which is still hard to push past the point of failure because of the resistive pressure of the sealed chamber.

This information is only what I have read, I don't have the plans and I don't have a deathbox.  Personally I have no interest whatsoever in increasing power handling, my audio philosophy makes me much more likely to try to increase sensitivity in a design like the WO or Imperial.
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« Last Edit: 06/15/06 at 01:50:18 by bassboy »  
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Lee in Arkansas
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Re: Finally, some action...
Reply #35 - 06/15/06 at 01:48:22
 
hehe, get me some plexi and i'll video tape it.....I'll pop a 12, for poops and giggles.
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J_Rock
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Re: Finally, some action...
Reply #36 - 06/15/06 at 01:50:00
 
Bassboy is exactly right.  The whole point of the DB is to increase a drivers ability beyond its rating.  By doing this it just happens that the driver sounds better within its normal range.

Also, the air does not need to be moved or "cupped" whatsoever for the sub to work.  The air doesn't actually move.  The molecules in the air vibrate back and forth.

Thats why a flat baffle will work just as well as a cone.  It just happens its alot easier to make a stiff cone than a stiff square.

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« Last Edit: 06/15/06 at 01:53:25 by j_rock777 »  
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bassboy
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Re: Finally, some action...
Reply #37 - 06/15/06 at 02:06:59
 
Lee, I thought you were going to try Bob's idea of splashing water with an old 12.  Maybe you can do that AND fry it in a DB at the same time.  Maybe if you are lucky, the water will short the coil and you can fry the amp too.  Maybe if you get REALLY lucky the whole car will burn.

Now THAT would be a video...diy demolition, lol.
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Lee in Arkansas
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Re: Finally, some action...
Reply #38 - 06/15/06 at 03:09:42
 
lol....I'm not plugging the water-12 into an amp.....it's gettin straight voltage.....it's gonna go BOOM.

I've got some old Road Gear 12's from Wal-Mart that just sit around and sound horrible.
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J_Rock
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Re: Finally, some action...
Reply #39 - 06/15/06 at 03:18:07
 
I have seen a few 4 ohm subs that will handle a wall outlet for awhile.  They get roughly 3600 wrms for a short period of time.
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bassboy
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Re: Finally, some action...
Reply #40 - 06/15/06 at 03:20:21
 
How about using a step up transformer to give it some REAL voltage?  Just make sure the polarity makes it go up, not down.  That would be a huge disappointment.  Cash prize if you can launch the cone free and clear of the basket.
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J_Rock
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Re: Finally, some action...
Reply #41 - 06/15/06 at 03:28:36
 
I have never seen that, I suppose with an older weaker spider I could make it happen.  You would need some serious BL though to get that cone to launch with enough force to break the spider, and surround- after it left the VC gap.
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bassboy
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Re: Finally, some action...
Reply #42 - 06/15/06 at 03:31:38
 
Yeah, I don't think it's possible.  Especially if it's full of water, lol.
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60ndown
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Re: Finally, some action...
Reply #43 - 06/15/06 at 04:50:42
 
i just read the white papers on the db again and it seems to me like testing was done with the magnet in the sealed side of the box, even the pictures confirm it? the db duct design exerts even pressure on the cone, relieveing wobble and wiggle of the cone and therefore allowing greater power handling.
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bassboy
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Re: Finally, some action...
Reply #44 - 06/15/06 at 05:42:21
 
OK, you got me there, I read it again and it appears you are right.  As long as SOMEBODY is paying attention we'll all be alright in the end.  At least I got you to read the white papers.  Me too.  It's been a couple of years since I read it and even then I was only skimming.  I only remembered "hot spots" and "increased power handling".  There are pictures that prove you are right and none that back up my posts, so I guess I got it crossed somewhere.  Maybe it was because in the pictures of the insert insertion the insert looked like it was prepared for a driver to be mounted in the way I have described (routed for flush mounting).  According to the white papers, I got everything wrong, as it was mechanical failure that presented itself as the first problem.  If I were to make one I'd try it both ways just to be sure it's really best that way.
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« Last Edit: 06/15/06 at 05:51:56 by bassboy »  
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