How to check / Test stuffing level in speaker box

[sudhirbhosale]

Hi friends
I built two way floorstanding speakers using peerless drivers. now I am planning to put filling material in the box. Since those are transmission line speakers, wool filling may not be advisable as inner air channel should be kept free. I have following questions:
1. What effect is on the sound quality after filling
2. How to test filling is less or more. As I read overfilling also has some issues
3. Corrugated surface of cartoon board - would it be good surface to absorb sound. As it has three functions : Dispersion due to corrugated surface, direct absorption on semi soft material surface, adding holes in board may help to trap sound.
4. Any other ideal materials

Thanks

 

[Hari Iyer]

The easy and convinent way to stuff is by using Recron ( polyester cotton), depending upon TL type ( classic, ML TL, TQWT), the amount of stuffing would vary. You can stuff correctly by this below method,
1. Download measuring software like REW.
2. Make an impedance jig for measuring speaker impedance.
3. Measure the free air impedance and note the impedance @ resonance.
4. Build your TL box, stuff them and measure the Speaker impedance and again review the impedance @ resonance.
5. A properly stuffed TL box will have the impedance @ resonance around 60% less than the free air impedance. Also the impedance peak will be around 10% more Hz than the free air impedance.

Also the amount of stuffing and where you need to stuff in your box can be simulated using Martin kings Mathcad or not so accurate LA software.

 

[all4music]

Have you lined the inner walls with dampening material? For my bookshelf speakers i first lined the inner walls with 18mm thick recron material and later stuffed the same material after teasing it based on trial and error method.. i do not have any measuring equipment so I'm dependent how the music sounds after each change.. after few tries I'm now satisfied with the response.

 

[sudhirbhosale]

How about Rockwool. Is it better than Recron?
Some claim that rockwool is also good for stuffing

 

[keith_correa]

How about Rockwool. Is it better than Recron?

For lining the cabinet inner walls, yes!

Some claim that rockwool is also good for stuffing

In my opinion, no!

 

[sudhirbhosale]

There are some Floor standing speakers models with 100% transparent boxes. I am sure those are glass looking acrylic . So how the function of stuffing is taken care there? I mean those dont have stuffing, so what things are substituted / compromised ?