simulating variovent with MJK sheets?

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I am designing a pair of speakers (using the FR125) for my 11 year old daughter. since her wish is that they should not be too large (yes, this sh*t starts already at a young age), I thought of making a aperiodically damped (aka variovent, aka controlled leakage, etc) CB. (I first proposed the miniOnkens, but even these were considered too large)

a thought came in my head to use MJK's mathcad sheets for this, using the BR sheet and then "applying" damping material in the port to simulate the variovent.

anyone has ever done this? @MJK: do you expect this to give good results? and related: in your sheets you give 1 lb/ft³ as max damping material density, why's that?
 
I'm glad it worked out for you.

11 yrs old and already getting a good set of speakers. That's too cool. My little sister is 17 and I don't think she's heard a decent stereo yet (we never lived in the same house, or else she would have.)

I'm toying with the idea of making her a cool little mini system with some cheap fullrangers and a tripath amp. Looks like it could be fun.
 
Henkjan said:

a thought came in my head to use MJK's mathcad sheets for this, using the BR sheet and then "applying" damping material in the port to simulate the variovent.

anyone has ever done this? @MJK: do you expect this to give good results? and related: in your sheets you give 1 lb/ft³ as max damping material density, why's that?

The 'ported box" work sheet allows densities over 1lb/ft3 in the port section. IIRC, Planet10 had mentioned some reservations about using this method for aperiodic simulation, but I think it to be the best solution thus far. I guess the question is: what is the stuffing density of a Variovent?
 
I've pulled together some information on Aperiodic Speaker Enclosures that should serve as a good starting point.

The variovent datasheet does not list a density of the vent.

Typically the goal is to flatten the impedance curve and the best way to do this is trial and error with impedance plots. With a smaller driver, I suspect you will want some low freq help.
 
Richard Small's take on it:

GM
 

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this is with 5 lb/ft³ stuff dens in the port, which means I'll have to cram ~20 grams of BAF into a 1" 9cm long port :rolleyes:

the small ripple just above 700Hz is from a port resonance there, but since I will place the port at the rear I do not worry too much


the effect of the stuffing is best seen in the impedance plots, here the one of the damped port enclosure
 

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