Speaker fill or wadding?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
A good tip I read from Markus over here: buy the cheapest cushions from IKEA and put them directly in your box, as is. These are basically polyfill wrapped in a very thin and acoustically transparent fabric, so your drivers are protected from fibers and contacts on the cone.
 
Last edited:
A good tip I read from Markus over here: buy the cheapest cushions from IKEA and put them directly in your box, as is. These are basically polyfill wrapped in a very thin and acoustically transparent fabric, so your drivers are protected from fibers and contacts on the cone.

IKEA. What can't they do. Waveguides and now stuffing. Outstanding!

I need to plan a trip up there.
 
A good barrier to keep the fibers away from the cone is aluminum or plastic mesh screening. glue it to the back of the basket. This is usually easy if it is stamped or not too irregular. Any very thin mesh that lets air pass through easily is good. Before wire mesh, AR used something that looks like a nylon stocking.

If this is an acoustic suspension design the amount of stuffing can't be easily calcultated, it must be determined by trial and error. The variables are the air volume enclosed, the moving mass, compliance of the driver, and the geometry and packing of the fibers. The combination forms a tuned system according to Newton's second law of motion as applied to forced oscillation. The approximate solution to this can be found in any first year college physics or mechanics book. The more stuffing the greater the aerodynamic drag and the higer the damping factor B. But the more stuffing the more air is displaced and the higher the spring constant K. The object is usually to get Q to 0.707 which is called critical damping. This is the lowest bass extension without an FR peak. Less stuffing usually results in a higher Q and a bass peak. Some people like this and some manufacturers did this deliberately aiming for a Q=1. More stuffing gives a lower Q and sacrifices bass unnecessarily. Some people refer to this as "tight" bass.

If you don't have an anechoic chamber, you can do what Edgar Villchur first did when he was inventing the AR1. He placed the speaker face up in a hole in the ground and suspended a measuring microphone one meter above the woofer (or was it a foot???) This avoids reflections that could affect the measurement, it's the poor man's anechoic chamber. The optimal enclosure size and stuffing for a given design is usually determined by trial and error.
 
0.5kg for every ~60 liters is ok, so 1kg is close - keep it away from the back of the drivers.

FWIW, in bigger boxes I buy the polyfill pillows at wallmart. That makes it easy to keep them off the drivers because they stuff nicely around the bracing.

Smaller boxes I use bondlogic ultra-touch cotton strips that I glue to the walls keeping it away from the drivers.

Many options out there, I have seen people staple speaker fabric or some sort of mesh netting to separate the drivers from the fill too.


I also always experiment with how much fill I like. Your numbers are correct for strictly adhering to fundamental rules but its cool to hear differences. For some reason I like the sound of over stuffed sealed boxes a little more.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.