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DB Ideas and Thoughts Ways to Improve/Modify (Read 2701 times)
haydenlake
Ex Member



DB Ideas and Thoughts Ways to Improve/Modify
10/04/06 at 20:44:21
 
So I built my first DB this weekend and I am plesantly supprised. Here are a few things I am thinking about in terms of improving the design to fit a certian speaker or get more of what I want out of the already great desing.

Note: that I don't really know much about bp boxes and I'll make some generalities.

1. If the moon shape really does have the impact of loading the cone symetrically then if you want a lower tuning (and you can't make the sealed portion larger) make the moon smaller. Many might say just slide the insert down and that'll do it but then you don't have a moon now do you.

2. If you can make the sealed section larger it should help out the low end and I don't see why you would want to cover the moon at all, I'd think puting the insert right at the moon would let the air flow best.

3. If I am correct in that the ported section in this type of bp is the high end cut off, then the low end is controlled by the airspace in the sealed chamber.

4. If the sealed section was the same volume in each situation then sliding the insert down father lowers the tuning (makes the port seem longer) only because of the pressure increase by decreasing the area of the moon. When you slide the insert down the box plays a bit lower but the port in actuality should be tuned higher. If this is true then if you have the option just increase the sealed section to lower tuning or get more low end.

PS can anyone give me any help on making a nice clean moon shape, I just roughed it with a pencil and it doesn't look that good. I don't know how to make one properly without guessing.
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60ndown
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #1 - 10/04/06 at 21:53:50
 
reduceing the size of the half moon mght leave u with port noise, but if it didnt then i think your thinking is correct.

i just play with a pencil when drawing the half moon, when i think its right i get my jigsaw out, when done with the jig saw i use very coarse and down to medium grit sandpaper to round edges.its not brain surgery, im sure a mm here or there wont effect perfomance that much.
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Adrian D.
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #2 - 10/05/06 at 12:36:36
 
i will give you all the number i've use to draw the halfmoon. as always, send some proof you have the plans. dolha_adi at yahoo dot com.
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thedude
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #3 - 10/05/06 at 16:43:55
 
it tells you how to make the port in the plans, at least I thought it was straightfoward.  

The shape of the port doesn't really load the cone symetrically, its intended purpose is to broaden the response of the duct through verovent action.  The use of a duct instead of a conventional port tube loads the cone more evenly.  Designing the port where it stops at half the driver diameter makes it load more symetrically also; so does the angled cut on the end of the duct.  

Increasing the volume of the sealed chamber will increase low end response but also decrease power handling.

When the insert is moved down it lowers the tuning of the duct, decreases the size of the front chamber and increases the size of the back chamber.  I wouldn't decrease the size of the port at all because its already about as small as it can be while still avoiding chuffing.

-Matt
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Adrian D.
Ex Member



Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #4 - 10/05/06 at 18:31:03
 
i get chuffing in the db-10 loaded with an infinity ref1040w. the rl-i can turn the db in a very serious ventilator  :-/
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thedude
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #5 - 10/05/06 at 20:45:43
 
The edges are rounded? ???

Mine chuffed with Steve's woofer on a 500 watt Peavey amp.  In the car with the 70 watt MTX amp I used it didn't.  I never did round the edges, but I will when I finally use it again.

-MP
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haydenlake
Ex Member



Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #6 - 10/05/06 at 23:32:48
 
No worries about the half moon in terms of dimensions I'm just not sure how to make a perfect arc for my moon. Perhaps just try a few circular cut outs from mounting baffles and see which diameter makes the numbers work. (dinner plates come to mind as well).

I would think that the last thing to load a cone evenly would be when a woofer fires into a pannel that only takes up about half of the cone area. Since steve is smarter than me I don't doubt it but I am still baffled on how it loads the cone evenly. Wouldn't the best thing to do would be replace the F pannel with a full piece of wood with a hole cut in the center with the same area as the void left from pannel F?

I haven't glued my insert yet so I might make another one with this idea and see if it works. To this same extent couldn't you make any symetrical configuration of holes for pannel F if they have the same area for the blow thru? Perhaps if you tried this you would be shortening the apparent lenght of the ported section since the void in F is as far as possible from the moon.

Just thinkin'

b
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thedude
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #7 - 10/06/06 at 03:55:11
 
"To this same extent couldn't you make any symetrical configuration of holes for pannel F if they have the same area for the blow thru? Perhaps if you tried this you would be shortening the apparent lenght of the ported section since the void in F is as far as possible from the moon."

Yea, thats right.  The hole or holes wouldn't tune the air space below them as low as the solid panel F.  

-Matt
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Adrian D.
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Re: DB Ideas and Thoughts Ways to Improve/Modify
Reply #8 - 10/06/06 at 11:02:54
 
b, did you draw up the half-moon ?
hit me up with an email, 'cause i still have the exact dimensions i used.
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« Last Edit: 10/06/06 at 11:03:30 by adi_ro »  
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