speaker fill

[Jody]

So, I've been filling speakers with hand fluffed fluff - which is extreemly long winded, until one large bass speaker which I lined with roof insulation, and covered with dacron sheet, which sounded great, but no direct comparrisons to be made.
Then, 6 months ago, i changed all the bass cones and filled some with fluff, some with insulation but didn't get the chance to compare properly. Now the speakers are back (from a job) and i've had the chance to compare with proper, well produced, test music (vocals, double bass, jazz etc), and the insulation version is much clearer, and integrates with midrange better. it seems to 'breath' better, less muffled, so i'm about to embark on some experiments to try all sorts of fills/ linings and would much appreciate any experiences / ideas of things to try. Thick carpet is on the list, and some ribbed spongey underlay is another one to try. (yep i raided the carpet fitters skip!)

Instinct tells me that the cone needs lots of air around it to function properly.
Is the function of fill / lining only to stop standing waves & reflected waves?

I'v got some old transmition lines that are filled with horse hair, and they sound great. should i be out in the feilds chasing horses around with a pair of scissors?:uhmmmm:
ta
jody

[Hoerninger]

should i be out in the feilds chasing horses around with a pair of scissors?:uhmmmm:

Come back! ;)
About 35 years back I ordered sheep wool in Great Britain for a short KEF B110 transmission line. The sound in the mids was better than with anything else. Today i can buy sheep wool from VISATON.

Any fibre should have a small diameter as far as I have understood. Horse hair perhaps, but not from the tail. :(

I have tried wadding (real cheap) with improved mids. For bass fiber glass is a good solution.

The appropriate filling does not only reduces standing waves but also helps reducing volume. A very scientific investigation:
http://users.ece.gatech.edu/%7Emleach/papers/Filling.pdf
___________
Peter

[moldyoldy]

And here's an interesting and useful layman's approach;

http://web.archive.org/web/20021007065602/http://integra.cyberglobe.net/caraudio/resources/fiberfill/

[soundboy]

I tried long hair wool years ago....supposed to be great for transmission lines....it doesn't work for mid cabs or vented woofers. Not enough dampening, IME....I still think lining the walls with fibreglass works as good as anything, although I do have acoustistuff in one set of mid chambers, and it seems a little more natural sounding....but I used twice what they recommended, forming a "nest" behind the driver, as well as filling the rest more loosely....otherwise it was too honky, and underdamped. Just my two cents...
The link from moldyoldy is a great one, although I would use acoustistuff over fibrefill....I think it works better....

[Mr. Widget]

The link from moldyoldy is a great one, although I would use acoustistuff over fibrefill....I think it works better....I haven't tried polyester fiberfill in decades... when I did try it I loved the installation due to it not being itchy or harmful to breathe... but I didn't like the performance at all. Luckily it was also a pleasure to remove.:D


Widget

[hjames]

I've seen other members talk about the accoustic properties of cat fur in their boxes, but mine won't stay still long enough for me to put the woofer back into place and close up the box:nutz:

[richluvsound]

i found these guy's really helpful. www.customaudiodesigns.co.uk
Look me up if you come to London.
Rich

[moldyoldy]

I've seen other members talk about the accoustic properties of cat fur in their boxes, but mine won't stay still long enough for me to put the woofer back into place and close up the box

:rotfl: :rotfl: :rotfl:

hmmm....maybe there's a market for cultured hairballs....kaaaak...kaaak...

[Jody]

The appropriate filling does not only reduces standing waves but also helps reducing volume.
Peter

why would you want reduced volume? more int. volume = more low end extension, no?

hang on, i'll read the links.

AH, got you. smaller physical volume, but larger apparent volume

as for the 1st link, great, but :confused: got through about 1 1/2 pages before my brain haemoraged.
I'll try again later when i've recovered.

Thanx for all your help, i'm sure i'll be back with more questions:bouncy:

[Hoerninger]

why would you want reduced volume? more int. volume = more low end extension, no?

hang on, i'll read the links.
Each speaker should have a specific volume relating to the specific design. Often it is optimal flat.
Concidering a modern speaker (QTS < 0.5), there are different choices:
- With too much volume you will have a weak bass although resonance frequency can be sufficient deep.
- With much too little volume the resonance frequency will be too high combined with a (nasty /boomy) peak.
- Only with a specific volume the frequency response is optimal flat.
(Bass resonance enclosures are a bit more complicated.)

With filling the volume seems to be enlarged.
Look at the layman's approach (Post #3).
With filling your enclosure can be a bit smaller (and lighter).

For an exact design you will need the TSP (Thiele-Small-Parameter)
http://audioheritage.org/vbulletin/showthread.php?t=13171
and
http://audioheritage.org/vbulletin/showthread.php?t=14472
____________
Peter

[Don C]

I read this someplace years ago, and I'm not certain that it's technically correct. But supposedly, the fiberglass slows the pressure waves in the cabinet as they pass through the fill. Creating a similar effect to moving the walls further away. Like a virtual larger cabinet.

[jim campbell]

Instinct tells me that the cone needs lots of air around it to function properly.
Is the function of fill / lining only to stop standing waves & reflected waves?


ive had really good luck with the foam that looks lik egg carton.it aint cheap but it works.the particles from fiberglass is an irritant to me and working with the foam was clean and easy.there are cheaper foams of a non accoustic nature that i have used too and had good luck.they were in my 10 cuft l136 a cabs

[JBL 4645]

I find this interesting I know some use fibreglass or other type of absorbent material that as certain properties. But why not something like an "anechoic chamber" lined throughout the inside of the enclosure?

What would that do? Well this make it worse better or perhaps something new might evolve from it?

[Hoerninger]

But why not something like an "anechoic chamber" lined throughout the inside of the enclosure?

Moin,

an anechoic chamber has dampening at the walls with a thickness of about 1 meter. And these rooms are preferably large. There is a lower cut off frequency where the absorption will not function any more.

In practice you can mount the speaker into a door, the closed room behind will not affect the resonance frequency. But you have room resonances which must be dampened. And that is what you have wanted to be avoided.

Anyway you do it, it should be engineered in a thorough way - consider the WAF too.
___________
Peter

[A perfect solution is a open baffle design for the summer garden - really advantage.]

[Jody]

Waf?
open baffle design?

to what extent is fill or lining for stopping standing waves?
if a box was big enough anyway, would a box with no parallel sides still need lining/fill to lessen reverberations?

I'll post some answers soon - just waiting for 4 speakers to come back from a job, and i'll have 8 in a row, each with different stuff in.

still a few ideas short for 8 x different things.
duck feathers?
polystyrene packing 'wotsits' (girlfriends idea, to clean up environment)?


thanks.

[Zilch]

Fiberglass vs. High Density fiberglass.

It's classic, actually....

[Gary L]

WOW, After all of that and the resulting brain cramp I decided to toss my slide rule and scientific calculator.
Since I find the old fiberglass filling that was typically used rather offensive and I still don't have answers if any of these designer fillings/foams and other materials are any better, I decided to go to my local Upholstery shop and use this Dacron/polyester fill with a fabric sandwitched between to keep it all in place and allow for the use of my trusty staple gun.

I will be interested to hear if any real results come from testing but for now this is what seems to work for me.

http://img.photobucket.com/albums/v722/Gamalot/Dayton%20Build/DSCN1662.jpg

Gary

[duaneage]

Fiberglass turns mechanical energy into heat energy. It also damps the impedance peak(s) of the driver quite well. 2 inches minimum and 4 inches max give the best results.

FG also sheds unless treated. The fibers can get into the voice coil, the air, L-pads, and even your lungs. I would spray the fiberglass with something to keep the fibers in place.

I use polyester pillow stuffing. It requires more material for the same effect but easier to work with and safer. I tried the acoustic foam and found it does not provide much impedance damping but does absorb midrange well.

YMMV

[Zilch]

http://www.bobgolds.com/AbsorptionCoefficients.htm

[Gary L]

Certainly there is nothing set in stone regarding the material to use or how much.
I am sure many have been faced with this exact same question and there may or may not be a perfect material or formula to achieve the exacting results we would all like.
It appears I could make this a life long pursuit to find what is best or just sit back and listen without disecting the issue much further.

I really do wonder just how much science, research and development manufacturers like Altec & JBL actually put into this subject.

I do get the feeling I am at this point:banghead: .

Gary