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Re:  Creating a general build tip thread (Read 2954 times)
Gexter
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Re:  Creating a general build tip thread
04/29/07 at 02:39:01
 

So lets say the DB
Then building the DB 10 follow the direction as Steve outlines

when you do get the insert in position for the room or car placement seal it in place.
I suggest putting screws in two side but not in opposing sides. Then seal the insert in place. Do not use something that hardens like liquid nails for this. you want to use silicon or something that can be removed later. the little amount of silicon used should not be a problem for foam surrounds.
What I do is slightly round the square base of the insert that blows into the cavity where the moon is. this allows me to add that little extra silicon for holding power under pressure.

The insert should be as tight as possible as long as you do not break something when you need to retune it. Sometimes depending how well your cuts are you stay with one alignment. ( find the way it slips in the best and leave some marks so you can repeat the same alignment)

When I think I may change location on the DB I just run the wire out the front and to the amp. If it is stationary and standing up I recess a small round speaker connect on the bottom of the sub  and make a groove for the wire.

An additional idea may be to add some short round legs as well. they can go under the sub or cut a mall 90 degree recess in the round leg about two inches down. this will allow you to widen the stance of of the sub because the legs will be at the corners sticking out a bit.

If your sub is going to be in an area where it may get damp use plywood because it will resist swelling and will not crumble when wet. I use an exterior grade plywood. and if I carpet it I paint or seal it well first. that way the moisture will not rot the wood so fast when the carpet holds the moisture against the box.
Carpet will hide moisture and you may found out too late to salvage the box.

What I do is keep the end that would be the bottom if it is standing up removable. the top in this case is glued and well sealed. the bottom would have multiple predrilled holes along the outsides and no gasket. this is the way I do it which I imagine many will.

I  believe Steve said that you do not need to add stuffing or lining but I am not sure anymore, But I do add stuffing . I line dacron in the inside of the sealed chamber and depending on the driver I may staple some batts of dacron to the inside of the lid that would normally be the removable part. Standing up its the part I seal instead.
I also lightly stuff the moveable baffle where it vents into the ported base.



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« Last Edit: 04/29/07 at 05:10:52 by gexter »  
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Adrian
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Re:  Creating a general build tip thread
Reply #1 - 04/29/07 at 09:57:04
 
i only glue the sides and the insert panels. the top and bottom panels are removable
use screws to get wire from one side of a panel to the other.

since i covered mine in leather, i used leather and contact cement to seal the insert in place
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Too much bass never hurts, or does it ?
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not_quite_deaf
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Re:  Creating a general build tip thread
Reply #2 - 04/30/07 at 06:40:48
 
My DB10 isn't yet finished although I started it 2 years ago.  But i used many of these ideas such as rounding over the insert sides to make it slide smoother, using silicone rubber the one time I sealed the insert (it easily peels off my painted box interior when you need to change tuning), and using black spray paint to seal the wood, in my case HD particle board reclaimed from store display cases.  I also used polyfill but not yet sure if it helps, and glued a piece of 1 1/2 inch thick foam rubber to the underside of the lid.  

The silicone rubber now widely available is not the "stinky" kind like the old variety.  I suspect it might be less likely to bother surrounds since it seems to be less solvent related than the old vinegar smelling silicone.  Also, many surrounds are now butyl rubber or similar and those compounds are much more resistant to solvents than polyfoams.  

All the outside edges on mine are rounded with a router, I think about 1/4 inch roundover bit.  Makes it less likely to chip and it looks much better.  

I also was thinking that thin flexible foam sheet packing material such as what electronic components often come wrapped in would make an excellent seal for the lid if you cut it into narrow strips.  It's only about 1/16 inch think and very resilient.  Probably better than regular foam weatherstripping.  But only if you have a real good fitting lid.
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anton-sa
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Re:  Creating a general build tip thread
Reply #3 - 05/01/07 at 02:53:33
 
Hi there, i know the box's claim to fame is that it can be tuned... but since ive actually made the box, currently busy body filling where the screws are (body filler commonly known as bondo in usa) instead of vinyl or leather im spraypainting the box. i used drywall screws to screw panels in place, i then remove the screws, apply glue.. screw panel back, my insert now moves freely inside the box. what im thinking is that the insert cannot possible be too close to the vent..
the woofer probably should be to close to the other side either.. this narrows the positions down. shall i start off in the centre?

i.e the sealed chamber roughtly the same as the ported chamber?

what are the know effects of moving the insert up(towards the lid) or down(towards the port) ???

one way obviously tunes the woofer at a higher frequency than the other?

i realise its probably not as cut and dried as this.. but some pointers will help.

A bit about my application, for a few years ive competed in iasca sound quality competitions. have done reasonably well. placed 3rd overall at the 2005 national finals here in south africa. this was with my mazda 323 based mini pickup(1/2ton pickup). this is a VERY difficult vehicle to get right but im glad to say i managed to pull it off.

The vehicle im currently busy with is my car, its a 1989 bmw e30. the more people in the industry tell me its a diffucult vehicle to build(like they did with the mini pickup) the more it eggs me on to overcome various design obstacles.

I've cut out a square out of the rear parcel shelf, around 14" squared. im currently running a decware 10" woofer in a sealed enclousure which is mounted bolted below the shelf, the woofer fires through the square hole i cut. problem is the design is flawed interms of cabinet size, its 1.45cu ft sealed. and the low frequency extension is brillient. but im lacking horribly in power. and there is plenty harmonic distortion, its asif the sound distorts, i presume this is when the woofer "looses compression/back" pressure inside the cabinet at certain frequencies it makes a distortion like sound.almost like bottoming out.. although inherantly flawed, my idea with the deathbox 10 which im busy with is as follows:

mount it below the parcel shelf, with the half moon port firing through the hole i cut. remove the 18mm mdf parcel shelf board i made and cut the wood away, so all im left with it a frame basically, this gets covered with carpet... so i can "hear" the cabinet better..

alternatively i could mount the cabinet in the boot somewhere and simply rely on the sound to travel through..not idea for a serious sound quality setup.
imho.

was thinking that by bolting the cabinet/mounting it below the parcel shelf.. i would be firing the port through the hole i cut, then i'll rely on reflection of the rear windscreen.. someone in the industry (must mention this guys name, martyn byrne) as he was responsible for building a vehicle that hit 184db 3 times at a iasca show. problem was that the meter kept coming off the windscreen. so it didnt count. even glued to the shield with superglue didnt work.

he time and again reaches 178 179db. this is with official iasca audiocontrol meters and mics. anyway, he mentioned that in my particular vehicle the resonant frequency is around 55hz...

any ideas on positioning of the insert ??
(sorry for my long-winded-ness, i just felt the background info to be of relevance)

which way tunes the frequency up??? and which way down?

any thoughts on some of my issues above?

i suppose all will be revealed once i actually take my current enclousre out.. take out the woofer, put it into the deathbox and connect it up.

any responses would be greatly appreciated,

Regards
anton
cape town, south africa.

ps: my other equipment im running is:
jl audio 300/4 amp
nakamichi cd700 source
midwoofers - stolen from well known kef coda 7 home hifi bookshelfs and built into 3litre sealer kickpanels
tweeters- dls reference series t25
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PC
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Re:  Creating a general build tip thread
Reply #4 - 11/07/07 at 06:35:05
 
In my recent exeprience, I built a DB and using a tone generator, moving the insert up (ie making the sealed chamber smaller) moved the response higher in freq. Moving the insert down (towards the vent) lowered the top end freq and reassured the low freqs.

Moving insert up and down also adjusted the resonant freq of the box (typically around 125Hz I am told by more experienced forum members) such that when there was a 1/2" gap at the mouth, I was getting a bx resonance around 110Hz, and fully open, got a resonance around 145 Hz.  Hope this is helpful? Cool
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