Subwoofer passive won't move

[vladmat]

Hello. I have recently tried creating a small speaker from a Logitech Z313 system. I have decided to go with a passive radiator design. The box has 1 liter and the passive radiator is tuned to about the original frequency (8.1 cm and 52 grams tune the passive to 42 Hz). Everything seem to work, as it responds to the desired frequency however, the speakers move very little. Everything is maxed out, but the excursion is only 1-2 mm at low frequencies (it should have been around 8 from min to max). The box is not leaky or anything, and I currently have no way of comparing it with the original box to know whether there is a difference in volume (there surely is). What is your opinion, is the passive too heavy or is there anything I could do to make it perform better?

 

[lovinthehd]

So the speaker sounds and measures within expectations but you don't think it (the passive radiator?) visibly moves as much as you expected?

 

[vladmat]

So the speaker sounds and measures within expectations but you don't think it (the passive radiator?) visibly moves as much as you expected?

Neither the active speaker nor the passive radiator move as much as expected. They hit around 42 Hz though, but the volume seems to be lower compared to the original. The original pumped a lot of air through the port, this is why I expected the passive radiator to move a lot.

 

[lovinthehd]

How did you determine your expectations? How did you design the new sub box? What passive radiator did you use? BTW this is more belongs in the DIY subforum....

 

[TheWarrior]

I built subs with SEAS woofers that have something like 2 inches of excursion. The only time I ever saw them 'move' was in using the opening scene to 'Live.Die.Repeat' when I had levels too high and the motor structure started clanking.

One important thing to remember, a woofer is not 'moving air'. It is vibrating air molecules. So don't concern yourself with extreme linear travel, that's only needed with extremely high SPL which won't do much good in homes where the rooms boundaries are smaller than the wavelengths.

 

[vladmat]

I'm sorry for my assumptions. I did test it with frequencies below 40 Hz and it seems to be ok. However, I think I miscalculated the weight. I get a lot of response between 40-48 Hz but almost nothing at 50-60 Hz.

How did you determine your expectations? How did you design the new sub box? What passive radiator did you use? BTW this is more belongs in the DIY subforum....

 

[lovinthehd]

I'm sorry for my assumptions. I did test it with frequencies below 40 Hz and it seems to be ok. However, I think I miscalculated the weight. I get a lot of response between 40-48 Hz but almost nothing at 50-60 Hz.

No worries on assumptions, we often start there

Are you still talking about visible movement when you speak of "a lot of response"? Or are you actually measuring response (i.e. with a measurement mic/software)? Did you design the box and passive radiator using appropriate software like winisd?