BIB with cheap fr drivers, help needed

[fcj]

Hi all,
I want to make some BIB enclosures for this 8inch fr drivers (nipponamerica nwx-833) around 8usd each and some cheap tweeters (maybe at the back)
They have no t/s specs , but I´m building a jig to test them with the speaker workshop,
At the moment they are playing in some cardboard boxes and they actually sound very good with a must equalization to bring down the mid-upper mid and high frecuencies (equalizer pict uploaded)

Any recomendations on the size of the BIB to start tweaking?

and, Is there a way to make a proto board to play with differents notch filters or something to bring down thoose nasty upper peaks
thank´s alot
Felipe

 

[fcj]

more images

musicmatch equalization

 

[fcj]

more pictures

in boxes

 

[Scottmoose]

Difficult to say. I'll see if I can seek out some T/S parameters in the morning (Fs and Vas are the critical parts, we can work around the others) and get back to you, unless someone beats me to it of course.

 

[fcj]

Ok, thank´s scottmouse,
I think I will start making it the size of a fostex207 BIB, so I can replace it later, :

Fostex FE206E & FE207E
L = (Line length) 174"
Zdriver = Driver 35" down from sealed end of cabinet
Sm = 133.875"^2

How can I calculate the dimension´s? (heigh,width,deep)
(sorry the silly question)

Does any one knows a good tutorial or info on how to design a notch filter?
thank´s
Felipe

 

[Klimon]

Looks like you could use a Zobel filter, here's a nice calculator: http://www.mhsoft.nl/spk_calc.asp In my experience component values / quality aren't very critical with a zobel.

The parallel noth filter calculator on that website is also a nice starting point but you'll need to finetune by measurement or ear. Use the inductor value indicated by the calculator, then try various combinations of resistance & capacitance untill you've found the peak and the width of attenuation you think is best.
For best sound use only good quality components here, caps are most important (I like motor-run caps), low dcr chokes & good quality power resistor.

Simon

 

[Scottmoose]

Ok, thank´s scottmouse,
I think I will start making it the size of a fostex207 BIB, so I can replace it later, :

Fostex FE206E & FE207E
L = (Line length) 174"
Zdriver = Driver 35" down from sealed end of cabinet
Sm = 133.875"^2

How can I calculate the dimension´s? (heigh,width,deep)
(sorry the silly question)

Does any one knows a good tutorial or info on how to design a notch filter?
thank´s
Felipe

Length is easy enough: 174 / 2 = 87in tall (big, aren't they). Strictly, it should be a bit taller due to the curve around the internal baffle, but this is close enough.

Zdriver is the distance from the sealed point to the centre of the driver. 35in down, means it'll be a fair old way up: 52in from the floor. That's a lot, but as it puts you naturally off-axis, probably no zobel needed to kill the inductive rise.

Sm (or Sl) = 133.875in^2. I'd make it 9.75in wide (internal) and 13.75in deep (internal) giving external box dimensions of 11.25in wide x 16in deep. Terminate the sloping internal baffle 6.875in from the floor and front and rear internal walls. The diagram on the Zilla pages should help with this.