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Leaving the backside open (Read 12159 times)
Hellion
Ex Member



Re: Leaving the backside open
Reply #30 - 01/13/06 at 06:59:24
 
okay so this is simply another try at making boxes smaller with compromises.  I don't really care for any compromises, and I like to try to keep the air volumes and use folding, and other things to make a box fit where I want it to.  (thank god for fiberglass and sand! ((sand is useful sometimes in figguring the true volumes of boxes molded to the inside of trunks, kicks, hatchbacks, and spare tire things.))

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J_Rock
Ex Member



Re: Leaving the backside open
Reply #31 - 01/13/06 at 17:03:18
 
[quote author=DirtDawg  link=1136480094/15#26 date=1137112348]Jet,

You gotta get carpet out of your head! It only helps to create a seal for the internal cabinet pressures, which can be substantial.

The benefit the floor offers is that of a plane, a large flat surface, in contact with the vent, which tends to extend the opening of the cabinet. Grin [/quote]


Using this, there really would be no aperiodic loading, however the carpet is the resistive membrane that restricts air movement.
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Jet-Lee
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Re: Leaving the backside open
Reply #32 - 01/13/06 at 17:34:53
 
Angry Cry

You say that it's not aperiodic loading, but the carpet is the restrictive membrane. Isn't the restrictive membrane and aperiodic membrane making it aperiodic loading??
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« Last Edit: 01/13/06 at 19:04:17 by Jet-Lee »  
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Hellion
Ex Member



Re: Leaving the backside open
Reply #33 - 01/13/06 at 18:13:24
 
see how you guys just go and confuse poor guys like jet and I?  Okay so I'm not really that confused...  This is more along the lines of a surface treatment like lining a box with polyfill to soften up the srufaces right?
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DirtDawg
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Re: Leaving the backside open
Reply #34 - 01/13/06 at 19:40:38
 
This is my last post on this thread, I promise. Grin

This is from Steve:

"It can also be used without the lid by flipping it over on a 1/2 pile carpet with pad.  The floor becomes the lid at that point and seals up the box.  The Q-Loss through the carpeting creates an action similar to a varo-vent allowing the box to breath.  Direct coupling to the floor through carpet raises the efficiency, lowers the cut off frequency, and offers the richest sound."

Notice he says it "creates an action similar to a varo-vent" through reducing the cabinet Q. He does not state that it becomes an aperiodic design, which would require a restrictive vent/membrane to accomplish. He is referring to the fact that the cabinet on the carpet is not a perfect hard seal and there is some loss of containment of the pressures generated and the cool part of it is that those losses stimulate the floor, directly. ...... making it behave like an aperiodic loading? Who knows?

Now .....  don't make me reach back there! Undecided

Smiley
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« Last Edit: 01/13/06 at 19:43:48 by DirtDawg »  
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Jet-Lee
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Re: Leaving the backside open
Reply #35 - 01/13/06 at 19:45:21
 
I think I really do understand, just waiting for J_Rock's response now.
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DirtDawg
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Re: Leaving the backside open
Reply #36 - 01/13/06 at 19:54:24
 
The only reason J_ROCK is still hanging with you here is to demonstrate to 60 that I really should be argued with ..... which is true. Grin

Really ..... that's all I'm going to say.

Smiley
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« Last Edit: 01/13/06 at 19:55:40 by DirtDawg »  
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J_Rock
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Re: Leaving the backside open
Reply #37 - 01/13/06 at 20:21:55
 
LOL

Basically what I thought I said and what I just read aren't the same, so what I meant to said is this:

When you filp the WO32 over onto the carpeted floor, the carpet allows air to move in and out of the enclosure, similar to a varo-vent or aperiodic enclosure.  It does not however make it an aperiodic design.

I was also comenting on DD saying that you'all need to carpet out of your heads because it only seals the box.  Well, if that were true, we would not have an aperiodic, var-vent, or anything, just a normal WO32.  However, the carpet does allow air so it is similar to a varo vent.

All in all, I was trying to state that the carpet doesn't fully seal the enclosure, allowing air movement.  But just because air gets in and out doesn't make it an aperiodic enclosure.

P.S. DOn't leave Dawg, its all cool.

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Jet-Lee
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Re: Leaving the backside open
Reply #38 - 01/13/06 at 21:13:53
 
Ok, now there is one thing I still don't understand.

I understand HOW it works, now.

Why is it not aperiodic?
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DirtDawg
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Re: Leaving the backside open
Reply #39 - 01/13/06 at 21:19:05
 
Isn't it funny that we are both arguing the same thing in different ways to get the same result, more or less.

I had to get you guys to stop thinknig about the sound going thru the carpet and coming out somewhere else. That was really bothering me, like X-Files stuff.

Earlier someone asked what if we make both sides (not seal completely) carpeted (that statement points why we have the 5th amendment ..... you don't have to admit what you were doing at the time.) and my hysteria was focused on getting that notion stopped. The pressure that escaped would be lost and not coupled to the floor or anything else and would decrease overall efficiency.

Paraphrasing 60 here:  Do what Steve says and don't ask why. We probably wouldn't understand the explanation, anyway. Cheesy
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J_Rock
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Re: Leaving the backside open
Reply #40 - 01/13/06 at 21:39:59
 
Aperiodic enclosures are very small boxes that "breathe" through a moving membrane.  Both the membrane and cone can not be in the same exterior space.  Either the membrane part has to be isolated by cutting a hole in the car so that it is outside, or the subwoofer has to be isolated from the rest of the trunk in a similar fashion to free air woofers.  The "box" has to be as small as possible (ideally the membrane should be right up against the sub), since it is used only for coupling the sub and membrane.  Aperiodic membrane configurations are very hard to design and tune, but give good frequency response and respond faster to transients, giving accurate and tight bass as opposed to boomy sound.  They are not ruled by Thiele-Small parameters like other designs, so any woofer would work with the membrane.

Mainly those two things, the carpet will nto move, and the membrane and woofer are not isolated.
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J_Rock
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Re: Leaving the backside open
Reply #41 - 01/14/06 at 01:22:21
 
If you really wanted the aperiodic effect, these are installed very easily and the site's description tells you hwo many you need.

http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=296-546
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Hellion
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Re: Leaving the backside open
Reply #42 - 01/14/06 at 03:56:29
 
okay I get it now, but I can't say "I get it" until I have figgured out every aspect of something... probably something really annoying o you guys, but I don't do it on purpose really.
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J_Rock
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Re: Leaving the backside open
Reply #43 - 01/14/06 at 04:17:02
 
it was not annoying at all, this one thread is prolly responsible for me increasing my knowledge of aperiodic enclosures ten fold.

(what that says abotu how much I knew...)
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Jet-Lee
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Re: Leaving the backside open
Reply #44 - 01/14/06 at 16:09:44
 
I like learning. Cheesy
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