Aperiodic Enclosure Design

[FE3T]

Since you ran some box simulation, I assume that you have the driver's T/S parameters; what is their Qts? System Q (Qtc) will never go lower than this figure.

az

Their Qts are 1.0

I have tried them in sealed cabinets as small as 9L and strangely enough, they doesnt really sound like they have the gigantic peak Winisd predict in simulations (more than 8db at 100hz) they do have what Morel refers to as a "Car filter" a foam plug acting as a flow resistor in the magnet systems rear vent, but what this car filter really does for the drivers behaviour in small volumes are unknown to me.

 

[audiozaz]

I'm guessing it's a standard vented pole-piece with a filter to physically impede crap from getting in there?

Qtc = 1.0 is generally deemed to still be listenable, although at the top of what's often recommended. What WinISD shows is but a transfer function and not the actual response; maybe this helped balance the speaker versus baffle step even. Of course getting Qtc down this close to Qts will require a large enclosure, even with aperiodic vents IMO. I guess that your ~30L boxes might get down to approximately Qtc=1.1 with reasonable aperiodic vents.

az

 

[FE3T]

I'm guessing it's a standard vented pole-piece with a filter to physically impede crap from getting in there?

I have seen other Morel made woofers with a thin (about 5mm) layer of coarse foam covering the magnet vent, that would be your crap stopper.

The Car filter are close to an inch thick foam plug consisting of 3 layers foam where 2 looks identical and the middle one seems a bit denser.

Macrom described the car filter with these words:

"CAR FILTER
THESE VARIOUS LITTLE PIECES OF FOAM ARE THE MOST IMPORTANT THING FOR
CAR AUDIO APPLICATIONS. WHEN THE SPEAKER IS PLAYING AT LOW VOLUMES, THE
FILTER REMAINS INACTIVE, THE CONE IS FREE, MICRO INFORMATION AND DETAILS
ARE THERE. WHEN THE SPEAKER MOVES MORE THIS FILTER BEGINS TO BLOCK THE AIR UNDER THE DOME
CREATING INTERNAL PRESSURE WHICH HAS THE EFFECT OF CONTROLLING THE SPEAKER LIKE AN ENCLOSURE.
THIS TECHNOLOGY HAS A GREAT IMPORTANCE FOR CAR AUDIO SYSTEMS WHERE IT IS ALMOST IMPOSSIBLE
TO MAKE A GOOD ENCLOSURE IN THE DOORS"

Sorry for the caps (copied and pasted from a PDF)

 

[Exflyboy1954]

Hi Folks,

Can anyone direct me to some design methods and procedures for aperiodic enclosures?

Thanks,

Skalfell

 

[HTWillie]

I -think- Vance Dickason's Loudspeaker Design Cookbook had a short section covering aperiodic vents.