BassBox Pro, prototype ?

[REALFLEO]

It's bad to learn that after I builded the prototype ;-)

Vifa's:
Vas: 25lts
Fs:38Hz

Vb I used is definitely not < 0.5Vas !

Thanks,

REALFLEO

 

[richie00boy]

Ql cannot be negative, something has gone wrong somewhere.

 

[REALFLEO]

I know but I can't find where.

 

[v-bro]

http://www.partsexpress.com/projectshowcase/nebula/nebula.html

 

[v-bro]

http://www.partsexpress.com/projectshowcase/nebula/nebula.html

 

[sreten]

Hi,

ok - 0.34, 38Hz, 25L :

some alignments - i don't like the classic green one, prefer the red.

/sreten.

 

[sreten]

Hi, varying Ql, /sreten.

 

[AndrewT]

Hi Sreten,

some alignments - i don't like the classic green one, prefer the red

is this to do with room effects?
Could you explain?

 

[sreten]

Hi Sreten, is this to do with room effects?
Could you explain?

Hi,

Yes, better match with room gain, less group delay, i,e better transient
response, lower effective cut-off point, better low bass power handling
(at the expense of upper bass) so less bass overload etc.....

In practise the red does kick drum in a fashion, the green doesn't IMO.

/sreten.

 

[AndrewT]

Hi Sreten,
if one were to choose the small sealed box and EQ it to produce the low bass, would you equalise to the red roll-off characteristic or to the "classic" green Q shape?

Is the "classic" = Butterworth?

 

[sreten]

Hi, your box - note Ql = 5, /sreten.

 

[richie00boy]

I know but I can't find where.

Maybe you did the calculations wrongly. There is a full T/S procedure and Ql calculation spreadsheet on my website www.readresearch.co.uk just try your data in the Ql calc spreadsheet first.

 

[REALFLEO]

Hi, your box - note Ql = 5, /sreten.

The thing is I'm not using a tuning freq. of 28Hz but 40.6Hz. Could it be the reason why my Ql is so weird=-0.12 ?

Wich program are you using ?

Do you use special ratio when designing your box ?

Thanks for your help.

REALFLEO

 

[REALFLEO]

also

according to your experience, do you think locate drivers so they aren't equidistant from baffle edges could really minimized diffraction ?

and should I place the vent in front or behind ?

Thanks,

REALFLEO

 

[v-bro]

do you think locate drivers so they aren't equidistant from baffle edges could really minimized diffraction ?
REALFLEO

Any dimensions made non-symmetric will be of benefit to the sound...

and should I place the vent in front or behind ?

A vent in the front gives more placement flexibility, but possibly more port hiss. The vent in the back will make you able to tune more with placement to change te bass response, and reduce the effects of port hiss, but might make placement unhandy in some situations...

I like a vent in the front, nice rounded edges will help reduce port hiss...

 

[v-bro]

Do you use special ratio when designing your box ?

It's possible this ratio won't be your ratio of preference, also possible this ratio won't work nicely in your room...

Originally posted by v-bro

Any dimensions made non-symmetric will be of benefit to the sound...

Think of the nice aesthetics going with this concept...

 

[REALFLEO]

ok I'm not really sure of the ratio I'll use because of baffle constraint (if I place the port in front...).

Also, when a software tell me to use a 15lts box, does that include vent volume ?

Thanks,

REALFLEO

 

[richie00boy]

No the volume eaten up by the driver and vent must be added to the target volume.

 

[REALFLEO]

Ok thanks a lot guys.

I'll build my prototype as soon as I have time for it and I'll give you news.

REALFLEO

 

[sreten]

Hi Sreten,
if one were to choose the small sealed box and EQ it to produce the low bass,
would you equalise to the red roll-off characteristic or to the "classic" green Q shape?

Is the "classic" = Butterworth?

Hi AT,

Yes the classic alignment is the maximally flat Butterworth, though when this
was popular, the Chebyshev equi-ripple was actually more commercially prevalent.

Nowadays - B&W go for a 4th order Bessel for their top models.

For a small sealed box with EQ - if EQ fixed - certainly not flat.

But similar to 6th order reflex alignments, there is no
reason not to make the 4th order sealed Q variable.

/sreten.

(note previous graphs produced using free WinISDbeta)