Speaker fill or wadding?

[rich31td]

I am building a Econowave speaker in a sealed enclosure, I have bitumin sheet to line the inside with but am unsure what stuffing material to use?

Wool or Polyester Wadding
Carded or Scoured Polyester fiber fill
Carded or scoured lambswool

I found a website in the UK that sell all of the above.

Or failing that egg profile foam.

World Of Wool - Fibre Fill and Wadding

[nightanole]

Carded Polyester Fibre Fill

Over here its called polyfill

Acousta-Stuf Polyfill 1 lb. Bag

[rich31td]

Ah good, thanks very much.

How much would I need for two 70L enclosures? 1kg enough?

[Ron E]

Originally Posted by rich31td

Ah good, thanks very much.

How much would I need for two 70L enclosures? 1kg enough?

0.5kg for every ~60 liters is ok, so 1kg is close - keep it away from the back of the drivers.

[DrDyna]

Originally Posted by Ron E

keep it away from the back of the drivers.

This is great advice, I've ran into quite a few speakers that are sticky on the back of the cone, picking little fibers off of them SUCKS.

[pos]

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.

[DrDyna]

Originally Posted by pos

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.

[pos]

I am currently building a bass trap using one of their book case

As for the cushion, it is in fact a pillow: Gosa Slan
GOSA SLÅN Pillow, stomach sleeper - IKEA

it weights ~0.5kg

[Soundminded]

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.

[chops]

I've used both poly-fill and fiberglass with great success. Just my 2 cents.

Also, in all my years of building speakers, I have never had any issues with any damping materials interfering with the drivers in any way. Just another 2 cents...