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Leaving the backside open (Read 11993 times)
ecflips
Ex Member



Leaving the backside open
01/05/06 at 15:54:54
 
Hello Everyone, I'm a new post, but I've been reading for a while,  I was wondering if there are any adverse effects of not leaving the backside of the WO32 open.  My problem is that I have hardwood floors in my listening space and if placed on the floor would be extremely leaky vs on carpet. So I was wondering if anyone has:
closed the open side on one, and if so were there any compensations that had to be made.
-or-
should I just get really small carpets to go under the cabinets. and if so does shag or low pile work best.
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Jet-Lee
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Re: Leaving the backside open
Reply #1 - 01/05/06 at 16:40:03
 
I think closed up is the best way to go.

I thought that flipping the box over on carpet just made it easier when needed to work on, just flip it over. I think I remember someone saying something about further filtering properties of carpet though.

Completely sealing the top and bottom of the box, wont hurt anything.
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gexter
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Re: Leaving the backside open
Reply #2 - 01/05/06 at 20:19:57
 
About the Wo32 on carpet
from steve in his write up
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.

It will not work well laying open face down on the wood floor unless  you added a thick gasket to the all the panels so it will seal to the floor effectively coupling it directly and making the floor the lid. But in this case you would not get the varo-vent effect.

INMHO
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« Last Edit: 01/05/06 at 20:21:07 by gexter »  
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Jet-Lee
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Re: Leaving the backside open
Reply #3 - 01/05/06 at 21:23:14
 
Yeah, I'm dumb.

I remember reading that passage somewhere.
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gexter
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Re: Leaving the backside open
Reply #4 - 01/05/06 at 22:43:45
 
Jet

I did not mean for my post to come off that way.

Sorry man.  :(

If it came off like you know nothing and I know it all it was never intended that way.
Besides that you know that would not be true anyway.

Us creative types have to stick together and keep the faith Grin

The gexter
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Jet-Lee
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Re: Leaving the backside open
Reply #5 - 01/10/06 at 22:15:39
 
Oh, no dude. I wasn't offended at all, just admitting defeat, that what I really read (what you posted) was in no way what I was remembering. Just one of those "duh" smack-your-forhead moments.

It's all good man. You'd know 100% if I was offended, as would everyone else on the board, lol.
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« Last Edit: 01/10/06 at 22:16:21 by Jet-Lee »  
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Hellion
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Re: Leaving the backside open
Reply #6 - 01/11/06 at 07:02:53
 
here you go man... just make a top/lid for the box, cover the top/lid with shag carpet, put 3 or four dozen screws in and BAM got yourself the same thing... wonder what would happen if you treated BOTH top and bottom?


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gexter
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Re: Leaving the backside open
Reply #7 - 01/11/06 at 13:03:18
 
Hmmm   how do ya figure that?
IMHO of course.
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« Last Edit: 01/11/06 at 13:03:45 by gexter »  
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60ndown
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Re: Leaving the backside open
Reply #8 - 01/11/06 at 14:39:59
 
[quote author=gexter  link=1136480094/0#7 date=1136984598]Hmmm   how do ya figure that?
IMHO of course. [/quote]
if you got the tension right on the screws it would kinda be like a varo vent? and both sides is interesting?
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gexter
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Re: Leaving the backside open
Reply #9 - 01/11/06 at 17:09:55
 
[quote author=60ndown  link=1136480094/0#8 date=1136990399]
if you got the tension right on the screws it would kinda be like a varo vent? and both sides is interesting?
[/quote]


thats all good and a great idea. its just the coupling with the effectively is what I am wondering about.
When the floor is the lid it is more direct

The varo vent part of it seems like a good idea idea and worth a try. Its a look outside the box thinking which is what I like.
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Jet-Lee
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Re: Leaving the backside open
Reply #10 - 01/11/06 at 21:09:59
 
Well, you floor also has padding underneath the carpet.

What if you:

Use some spray adhesive ($5) and stick some padding to your board, then do the same with the carpet. Now lay your board on the ground carpet side up. Lay your box on the carpet as you would in your home. Use some decorative brackets to now secure the box and carpet-board at the correct "tension", which is actually the weight of the box, as it would be in the actual setting.

Flip and repeat, lol.
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DirtDawg
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Re: Leaving the backside open
Reply #11 - 01/11/06 at 22:36:13
 
Are you guys on kRaK? Smiley
Building a WO32 and making the top and bottom flex in response to internal pressures will create a higher order cabinet with 2 large out of tune passive radiators equalizing most of the pressure the drivers can create.
The response would not follow the original signal's waveform very closely. (Enormous group delay)
The main reason to use the floor instead of ONE side is to better load the floor. Coupling the cabinet to the floor is a tricky process and may not be desirable in all cases.
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« Last Edit: 01/11/06 at 22:42:03 by DirtDawg »  
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60ndown
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Re: Leaving the backside open
Reply #12 - 01/12/06 at 01:14:06
 
[quote author=DirtDawg  link=1136480094/0#11 date=1137018973]Are you guys on kRaK? Smiley
Building a WO32 and making the top and bottom flex in response to internal pressures will create a higher order cabinet with 2 large out of tune passive radiators equalizing most of the pressure the drivers can create.
The response would not follow the original signal's waveform very closely. (Enormous group delay)
The main reason to use the floor instead of ONE side is to better load the floor. Coupling the cabinet to the floor is a tricky process and may not be desirable in all cases. [/quote]

there is 2 people im not ever gonna argue with, 1 is steve d  the other is you dirt Grin
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Hellion
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Re: Leaving the backside open
Reply #13 - 01/12/06 at 02:32:18
 
okay so it's not a good idea to treat both sides of the box.  And I never meant for the carpeted sides to flex like a passive radiator, I meant to screw the thing on as tight as a normal makita drill would get it.  I was thinking that perhaps the varovent theory was good, and hey, it something makes an improvement, why not DOUBLE the effort?  But really, the whole post wasn't that serious at all, and I didn't think anyone would take it seriously.


And NO, I won't argue with anyone on this forum, that's not what I'm here for.
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J_Rock
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Re: Leaving the backside open
Reply #14 - 01/12/06 at 04:35:24
 
Settle down Dirt. Just kidding Dawg, they prolly are on crack.

These guys are talking about making "floors" and attaching them to both top and bottom of the WO.  The simple answer is that the WO works well on plain carpet floor because the floor extends the horn's effective mouth increaseing efficency.  Hence the "coupling effect."

Then the carpet allows some air, very restricted air, to go in and out of the box making it easier for the woofer to move the air masses, yet keeping the movement under control.

If you simply attach "floors" (wood, padding, then carpet) to the WO32, you get no coupling effect and alot more air moving in and out, decrease the woofers ability to pressurize anything and hold its course(play music). In essence moving the woofer from a sealed, controlled enviroment to a unrestricted Free Air enviroment.  

SO no benefit that I can think of, although one side with a floor and perhaps a floor with a 3/4 in deep cutout would allow the wo to "couple" with the floor and maintain a similar "varo vent."

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gexter
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Re: Leaving the backside open
Reply #15 - 01/12/06 at 05:59:15
 
I thought that the one side vented idea was kinda cool. But I think that if it is not flat on the carpet on the floor whats the use. But its still a idea. I would not try it that way so maybe I should have said that in the beginning.

My orignal post says it all  (Hmmm   how do ya figure that?
IMHO of course.) then I thought I was being an a55  shooting the idea down.  

I was running my 5 1/4 flat on the floor on some thin carpet with a 20 lb plate on it. thats the way it work best. it's in a holiday trailer and gives a good illusion of bass for the kids. ( rattles the hell out of everything)
They use it and like it because I don't and I don't want to play with it anymore.

That would not work at all in my house!. My toy WO32 is set up just like 60 mentioned a couple times. mouth firing into the floor 4" up and thats how it works the best for the room. I would have not even thought of that unless 60 would have mentioned it. I screwed with that design and I like it. its my favorite build and most fun.

I admit that I don't play around and experiment anymore. I read though all these formulas and ready made plans.
I am reading another book right now and I got so bored I checked in here to be accused of using crack. ( thats more fun than the book)

Now its not nearly as much fun as " what happens it I do this...... oh that sucks what about this... mmm better...why?" Trying it in differant ways is always fun and then sooner or later you hit the wall of physics.

I would not argue with the Dawg either and a whole host of others. Well ok ya I would argue but thats for entertainment value not because I think I am right.  ;)


Smiley





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DirtDawg
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Re: Leaving the backside open
Reply #16 - 01/12/06 at 06:48:47
 
Fellas, groovy fellas,

The kRaK remark was a meager attempt at humor and once again it fell thru the cracks and became total goofyness. I was only crackin' on ya, without realizing there was some sensitivity to the subject. If I ever come up with a way to crack you guys up I'll be happy, but I hope no one has a burr in their crack tomorrow. Gotta get crackin' here. Those kids get up at the crack of dawn.
Cheesy Cheesy Cheesy
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« Last Edit: 01/12/06 at 06:49:32 by DirtDawg »  
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Jet-Lee
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Re: Leaving the backside open
Reply #17 - 01/12/06 at 14:54:57
 
LOL, that crack comment was kinda funny to me. I thought DD wanted some.

I still, though, don't understand why my idea wouldn't work only doing it to one side.

A floor is concrete/wood, padding, carpet. Why can't you make a floor, with padding and carpet, and just attach it to the box. You would just flip the box over on top of your "floor" so that your not compressing everything too much to cancel the varo-vent, but not too little to make it too much, but it's set just the same as if it was in your living room. The you secure the "floor" to the box with brackets to keep it at it's pressure and still be mobile.

You could then stand it on end with the mouth facing down about 4" and have the varo-vent effect along with the great sounding down-firing of the horn.
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Hellion
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Re: Leaving the backside open
Reply #18 - 01/12/06 at 16:59:22
 
Yeah what's wrong with securing the "floor" to the box?
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J_Rock
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Re: Leaving the backside open
Reply #19 - 01/12/06 at 20:40:27
 
I can understand if you didn't read my post, but when you ask what people think and I already stated I think it would work similarly if done only on one side...
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Jet-Lee
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Re: Leaving the backside open
Reply #20 - 01/12/06 at 20:55:33
 
I just realized, while reading, all your doing by laying the open WO or WO32 on the carpet, is making it a variation of an aperiodic box.

An aperiodic membrane is aka a variovent.

Now, why is it that you absolutely have to vent an aperiodic enclosure into a seperate sealed volume, and not just out into thin air? I don't understand that part, since it works just fine with a WO/WO32.

J_Rock, don't mean to argue, but I was rather confused by both yours and DD's posts. You both say that it wont work, but it could.....confusing to me.
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« Last Edit: 01/12/06 at 20:58:13 by Jet-Lee »  
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DirtDawg
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Re: Leaving the backside open
Reply #21 - 01/12/06 at 21:34:54
 
I'm not saying that covering the top and bottom sides of a WO32 with carpet or some other acoustically absorbent material will not work. As long as the seal is good and the panel is rigid, it works. If you feel the need to absorb certain frequencies that might hit the top or bottom, there are better things than carpet to use for that.

Treating the inside of a cabinet with absorbent materials will not create an aperiodic enclosure or a vario-vent. The whole reason to leave the bottom off and couple your cabinet directly to the carpeted floor is to extend one side of the port/vent/horn to almost infinity (almost!).

The other (top) side will still be operating at the same specification, but the side that is down will appear longer to the pressure exiting the cab and continue to load or resist that pressure wave as it enters the room. That will give you a better coupling into the air in the room. The added benefit is that the internal pressure will also enhance the coupling to the floor, since the floor is subjected to all the pressures inside the cabinet.

It's not complicated, it's just difficult to explain.

If you want an aperiodic cabinet, the main thing to remember is that it is merely a tuned vent cabinet which has a resistive port. You do not need 2 chambers to achieve this. I think that idea came from looking at pictures on that car audio site where the trunk seems to be drawn as if it was more important than it really is. The resistive port will help to smooth out the impedance peak at Fs in a much smaller box at a loss of total output. OK so, just add more power to the smaller cabinet!

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Jet-Lee
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Re: Leaving the backside open
Reply #22 - 01/12/06 at 21:47:23
 
Everything I've read has stated that with an aperiodic box, the volume that the aperiodic membrane vents to needs to be completely sealed from the volume that the cone of the speaker plays to. I still do not understand why, and no one explains it.

I guess I'll never understand the vario-vent aspect of the WO/WO32.

I'm not sure you understand 100% what I mean with the carpet idea, I'm not "treating" the inside of the box. It's really just creating a false (portable) carpeted floor, and securing the WO/WO32 to it. It would be the same as taking your WO/WO32, securing it to your existing floor with angle brackets, then cutting out that square of floor. SO you have a portable vario-vented WO/WO32.
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« Last Edit: 01/12/06 at 21:51:06 by Jet-Lee »  
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DirtDawg
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Re: Leaving the backside open
Reply #23 - 01/12/06 at 23:11:51
 
[quote author=Jet-Lee  link=1136480094/15#22 date=1137102443]Everything I've read has stated that with an aperiodic box, the volume that the aperiodic membrane vents to needs to be completely sealed from the volume that the cone of the speaker plays to. I still do not understand why, and no one explains it. [/quote]
The actual resistance to the flow of air through the membrane is what damps the resonance of the driver. Generally, the common practice is to use a vent that is equal to the driver's area and a much too small cabinet volume and bring the tuning of the vent down to the desired range with layers of resistant material. You can also get there by using membrane material behind or in front of the driver, but it is a more difficult approach for the DIYer. The reason it is more desirable to use the membrane suspended in the cabinet or attached to the driver is that it's a more efficient way to damp the resonance.

Those are the most difficult to tune, because the air space between the driver and the resistive membrane is so small. A much easier plan for the dIYer without test equipment, is to use a resistive port design.

I'll try to find a site that explains it for you, written by someone who can actually write well.
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« Last Edit: 01/12/06 at 23:16:27 by DirtDawg »  
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DirtDawg
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Re: Leaving the backside open
Reply #24 - 01/12/06 at 23:14:10
 
[quote author=Jet-Lee  link=1136480094/15#22 date=1137102443]I guess I'll never understand the vario-vent aspect of the WO/WO32.

I'm not sure you understand 100% what I mean with the carpet idea, I'm not "treating" the inside of the box. It's really just creating a false (portable) carpeted floor, and securing the WO/WO32 to it. It would be the same as taking your WO/WO32, securing it to your existing floor with angle brackets, then cutting out that square of floor. SO you have a portable vario-vented WO/WO32. [/quote]

I think I do get it now, but the property of the floor that makes it magic is that it extends far past the sides of the box, extending the loading of the vent and that property is not easily made portable.   Smiley

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Jet-Lee
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Re: Leaving the backside open
Reply #25 - 01/13/06 at 00:21:06
 
So then the sound comes up through the carpet further away from the box? I think I understand that now.

A link about aperiodic would be greatly appreciated, thanks!
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DirtDawg
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Re: Leaving the backside open
Reply #26 - 01/13/06 at 00:32:28
 
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
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Hellion
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Re: Leaving the backside open
Reply #27 - 01/13/06 at 00:34:21
 
so the entire floor becomes loaded and is a part of the whole equation?  Okay so the venting isn't what makes the box have a lowered LF?  I'm confused...  What makes the whole upside down on the carpet arangement so appealing?

What about using an AP vent in the side of a wo32? would that cause the magic to happen too?  or what?  I suppose that what I really would like you to do is explain how the floor does it's magic.  Then once I have that in my wee little brain I will understand why this can't be mode portable.  I'm sorry, but I do not understand the whole thing and need a foundation of basics to build an understanding on.


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DirtDawg
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Re: Leaving the backside open
Reply #28 - 01/13/06 at 00:43:41
 
"Aperiodic box

   Essentially a poorly sealed box, an aperiodic box vents the inside of the box to the outside air via an "acoustic resistor". All other comments about sealed boxes generally apply. The purpose of an aperiodic design is to allow a smaller enclosure than would normally be possible. If you put a driver into a sealed box that's too small, it will exhibit high Q, causing a peak in its lower response and a high impedance peak. By letting the box leak air, both the response and impedance peaks are tamed. Aperiodic boxes should not be confused with ported boxes (discussed below). The essential difference is that a that the port in a ported box acts as a Helmholz resonator tuned to a specific frequency in order to enhance and extend the low frequency response. Aperiodic vent designs exhibit no such characteristic resonance and functions solely as an acoustic resistance. As with any other low frequency system, the smaller size is achieved at the cost of a somewhat higher F3 and a steeper 18 dB/octave roll off than a sealed system.
Aperiodic vents are sold primarily by Dynaudio (which calls them "Variovents") and Scan-Speak (which merely calls them a "flow resistor")."



Another definition.


More still


DIY Audio Forum. Read the last post. This guy has the same type EBS cab as I built 15 years ago and I now use in my HT system. He points out a critical concern about ABs in general.
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« Last Edit: 01/13/06 at 02:03:39 by DirtDawg »  
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Jet-Lee
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Re: Leaving the backside open
Reply #29 - 01/13/06 at 01:58:56
 
[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]
I got it now. Thanks!
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« Last Edit: 01/13/06 at 01:59:06 by Jet-Lee »  
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Hellion
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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
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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
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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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ManaFox
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Re: Leaving the backside open
Reply #45 - 04/18/06 at 19:37:03
 
Maybe I can help. Or make things even more confusing, I don't know.

Leaving one side of the WO32 open allows it to breathe a little better, yes, but when you place the open side down onto the ground, you're almost using your own floor as a sounding board for the subwoofers. And with the carpet thing, that's rather complicated, and somewhat useless, IMHO.
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Adrian D.
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Re: Leaving the backside open
Reply #46 - 04/20/06 at 12:49:07
 
i don't think the wo32 will work if the open side is left 'exposed' (not flipped on the floor).
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