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deathbox 10 insert position (Read 3067 times)
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deathbox 10 insert position
05/01/07 at 02:48:33
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.

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,

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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Re: deathbox 10 insert position
Reply #1 - 05/01/07 at 06:42:06
the general idea with the insert is that the lower you move it, the lower it tunes the box. i would start with it set at the middle and start moving down. if you don't like it, move it up. it's as simple as that Tongue
your goal is to get higher spl ?
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Re: deathbox 10 insert position
Reply #2 - 05/01/07 at 11:20:57
hi there,
thanx for your reply.l by adjusting the insert lower, u mean towards the port?
yes i would like more spl but only to a degree, my soundstaging is near pefect id say..
well.. in the mini pickup i scored 46 out of a possible 50 for imaging.american judge chris orblom(director of iasca international affairs) judged the car.
i'd say in the car (the bmw) its its similar the kef woofers image really well. sounstage around mid to 2/3 windshield height.

only thing now is to get the bass to align correctly and to travel in the vehicle. being a bmw the trunk is well sealed off from the vehicle.
i'd say i should open it up a bit.. on that note.. i better get me old clothes on and get down and dirty.. need to remove rear seat etc etc..
install woofer into deathbox and play!

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