Is this correct way to build DIY PR

[arjunm009]

Hi
I took a local 4" driver and removed the magnet. Can this substitute as a DIY passive radiator?


Here are some images

Other images for more clarity - Imgur: The magic of the Internet


I just want to know if I am on the right track just on the build aspect. Its a local driver I purchased from local speaker repair shop, there were no spec sheet available.



More info -



My goal is to use two of these with the ND91-8 driver along with it.

 

[wonderfulaudio]

Make an arrangement to add weight for tuning and you are good to go

 

[PRR]

Not necessary to remove magnet. If there is no electric circuit attached to the voice coil, the magnet does nothing.

 

[JMFahey]

IF it roughly matches the main woofer in size and specilly resonance, it will do.

 

[eds65gto]

DIY PR

Removing the magnet of course will make a passive radiator , but so will shorting the voice coil leads. This creates a "back emf" that opposes cone movement similar to putting weight on to the cone. This will provide some damping of cone movement but the effect depends on many factors , which may help or hurt response.
" Try it , you'll like it "
Just another idea.
Ed

 

[Galu]

Technically, the total volume of air displaced (Vd) by the two PRs should be at least twice that of the single ND91-8 driver.

Roughly speaking, your 4" 'local' drivers should each be capable of a maximum cone excursion (Xmax) similar to that of the 3.5" ND91-8 driver itself.

Tuning by adding mass to the PR cones will be necessary.

https://www.parts-express.com/pedoc...ne-full-range-driver-8-ohm-specifications.pdf