Need help w/ tuning frequency

[jaybird]

I have an EBS Shiva (per Adire Audio's specifications) with a passive radiator. I blew up my driver on one of Master and Commander's canon scenes.
The tuning frequecy of the subwoofer is around 18hz. I was wanting to adjust my tuning frequecy to around 20hz. I have tried to use some programs but can't figure them out. Any help will be greatly apprechiated. Thanks

[psychosteve]

abacus 20 is realy simple to use, you will need box volume and enter freq. reqired, select from a list what diam port you got, click the button and hey presto!!! it tells you what length the port needs to be! easy. see you soon, steve.. ..

[Ron E]

Originally posted by jaybird
I have an EBS Shiva (per Adire Audio's specifications) with a passive radiator. I blew up my driver on one of Master and Commander's canon scenes.
The tuning frequecy of the subwoofer is around 18hz. I was wanting to adjust my tuning frequecy to around 20hz.

I honestly doubt that making a 5% change will be the difference between destroying and not destroying a driver. You need to either be more careful or insert a strong rumble filter to cut frequencies below tuning.

You can figure out PR weights by simulating a port with the same piston diameter as your passive radiator - calculate the difference in volume betwen the two ports and figure out how much that air weighs. Then remove that much weight from your PR and you are in business....

Originally posted by psychosteve
abacus 20 is realy simple to use [...] select from a list what diam port you got, click the button and hey presto!!!

He has a passive radiator

[kelticwizard]

Bullock and Whites Freeware BoxModel models passive radiators.

It's DOS. therefore it is not cool. but it is accurate, and good.

Be sure to press the right arrow key, Þ, key before entering data.

Ignore the Transmission Line section. Even Bullock admitted it was not good. Use the freeware at www.quarter-wave.com for that.

But ported, sealed, passive radiator and bandpass boxes can be simulated with this program very well.

http://www.hal-pc.org/~bwhitejr/

If you want, give me your box volume and the size of your passive radiator or radiators, (specify one or tow), and I will give you the necessary weight for 18 Hz tuning.

I also agree with Ron that I don't think the diference between 18 Hz and 20 Hz tuning is what blew your woofer.

[kelticwizard]

Oops! guess what. BoxModel doesn't tell you how much extra weight you add to the passive radiator to achieve a desired tuning.

Any tuning is easy enought to check-just use an online tone generator, your sound card with speaker outputs, or your sound card to an amp if you don't have them, and a multimeter. You are tuned at the frequency where your impedance is least, (or current is most).

Anyway, Subwoofer Simulater by our own member, F4ier, has the Shiva already loaded into the program , along with the Stock Pasive Radiator of 285 grams.

The EBS Shiva calls for a 142.5 liter box, (why-oh-why did they include a fraction of a liter in a box that big?), and a box tuning of 17.3 Hz.

To get that box tuning, you add 350 grams of weight to the Shiva Passive Radiator. That is in addition to the 285 grams that is already on there.

If you want to make it a straight 18 Hz, you add 302 grams, in addition to the 285 grams that is already on the stock Passive Radiator.

Download Subwoofer Simulator here:
http://www.geocities.com/f4ier/speaker.htm

If this is not the size box you were talking about, just let me know and I will tell you the extra weight you need to tune the Passive Radiator to your desired tuning in the correct box size.

[psychosteve]

DOHHHHHHH shoulda read that more carefully. thats what rushing gets you. steve.. ..