Help in measuring response of 4th order BP box

[venki]

hi Ron thanx for the reply. Frankly speaking this is first "serious" box i am designing (actually finished ) (other boxes i made was without much knowledge of the design that goes behind it). thanx for the info (about not using damping material in BP box). I have some basic question regarding the port placement.

1. if it is placed face down, wont the reflection from the ground cause distortion?. Will the efficency be reduced.
2. If the vent is in the rear wont it increase the time delay and phase?

These are some of the doubt that came to my mind while going thru your reply. I am asking these questions out of curiosity .

thanx in advance,
Venki.

[simon5]

1. Efficiency will not be reduced, you'll not get much distortion.

2. You could get significant time delay if you plan to use a crossover at 500 Hz or so... if you stay under 100 Hz, you'll not have a problem with this.

[venki]

Hi again,

Thanx to all,

I did try out the rear firing and the down firing modes. I found out the keeping the port firing down decreased the booming sound and also the noise (thanx to all) (actually the box is constructed such that when the port is firing down/up the speaker inside the box is vertical so i think this can also contribute the problem i faced).

I would also like to know the height(min/max) of the port's mouth from the ground (currently i hav placed the box on a small chair (about 20cm high) i need to replace this with a permenant stand).

I am yet to measure the response fully (I did measure the impedance i found it to be closer to what i designed (Fl between 30 and 35hz Fh between 70 and 80 hz)

Thanx in advance.
Venki.

[Ron E]

2 port diameters should be sufficient. Much less and the air under the box will act as an extension of the port and lower the tuning frequency. You can measure whether or not this shift occurs in your situation, and account for it by shortening the duct somewhat.