I need your help -- planning a infrasound capable subwoofer

[Yevesy]

Thanks this is all really good to know. It looks like to keep the air velocity below 15 m/s at 18hz I'm going to need two ports, either that or a ridiculously small box.

Where it says 'vent length' - is this figure for the total of both or what they should be each?

For example I'm currently looking at vent diameter of 11cm, 98.32 length, in 165 litre box. Would this mean two 49.16cm vents?

 

[bjorno]

.. it seems you answered it for me already.../QUOTE]

Yes I have..

..could you please post/send some more detailed drawings or ones that I might be able to build from easier? ..

Would be spoonfeeding..have no time to do make drawings.

Submittin a few pictures: First a few blown up Plots for my suggested DBR previously Posted and your latest own design attempt + the dismissed Alpine 15 in a DBR.

b

 

[weltersys]

For example I'm currently looking at vent diameter of 11cm, 98.32 length, in 165 litre box. Would this mean two 49.16cm vents?

No, 98.32 length means 98.32 length.
Shorter ports tune higher.

 

[Yevesy]

Ok got it, two 98 cm vents.

I'd like to put a

 

[Yevesy]

*90 degree bend in the ports so theyre facing forwards, will this complicate things too much? I've read if I measure down the centre of the bend I can roughly consider this measurement part of the overall length and account for it

 

[vacuphile]

As a rule of thumb, you have to detract 1 radius from the calculated length of the pipe. Always measure before making things definitive.

 

[bjorno]

Hi,

FYI,Pixel Dodleing:

b

 

[Soldermizer]

I'm a bit late here. Did OP ever build his 19 Hz sub? I see his main requirement was to make a 19 Hz standing wave. Might the easiest way to do this be just make a quarter wave transmission line like the common Sonotube with a driver at one end? I am advocating my only subwoofer "build" so far, exactly that. It works ok. While not musical, I recall you get maximum peak at one frequency if you put the driver in the center. Your tube (half-wave) would be nearly 30 feet long..ten meters or so...Sonotubes are available in such lengths but would they fit?

 

[00goobs]

I guess it may be a bit late, but wouldn't swinging a door back and forth 18 times a second a few inches before and after the threshold accomplish this task, with more displacement than the same square area of the door in speakers? Like a door from a restaurant kitchen?

A door sized PG cyclone...