Lead shot questions

Mboldda1, you are right, I have never heard of a problem, though I do find Elizabeth's logic quite sound (no pun). Keeping it bagged would require woofer removal but still no big deal.

Eldartford, can you elaborate on the misunderstanding? Does the weight get stacked on top of the enclosure? I have read a lot lately about mass loading the Von Schweikert VR-4jrs, is that not internal?

The CO2 is interesting and doable. I have a 20LB CO2 cylinder I use to force carbonate Beer kegs. Though, like most B & Ws, the CDM9s are a ported design. I do have the bung plugs. They are made from foam rubber and with the port low mounted, I feel that over time the gas would leak out. Drilling would NOT be acceptable. I could lay the speaker on its back, fill it via the port, then plug it. Blasting the CO2 in for a while would stir the air and facilitate a high CO2 saturation but it would not completely displace the nitrogen and oxygen.

Lead shot will kill the stage. Tom

you noticed that too, huh?

Working with one manufacture to tame a resonance in the bass range..They used mass loading in the cabinet to squelch the peak before the newly redesigned woofer arrrived for replacement. They asked me what I thought .."Speaker sounds coherent but slow and shut down..You need to take the lead out"..After the lead was removed the stage opened up and back came the speed. That was the first step..The second step is another story..Tom

Distortion...Suggestion. Turn the speakers upsidedown to fill them. CO2 "pours" like a liquid, and if you go slow you will get a good fill. If the port plugs are tight and not permiable the CO2 will hardly leak ar all. (It will stay in an open dish or other depression, and sometimes is a suffocation hazard to workers for this reason).

It would be interesting to hear your observations regarding the speaker performance using air vs CO2, with the plugs in in both cases.

But don't use up all the CO2 so that you can't service the beer kegs!

With regard to "Mass Loading" this term has been used to describe addition of weight to a woofer cone so as to lower its free air resonant frequency. In the old days we used to modify drivers in many ways, but that is not done much today because there are so many drivers available, of every possible characteristic.

Fifty years ago Warfedale (and others) used enclosures with double walls, which you filled with sand after the speakers were set in position. I guess this would be Mass Loading. Other speaker makers may use laminated material to make enclosure walls heavy (I have used wood/sheetrock/wood). However the wall thickness must be taken into account when the enclosure is designed.

In general, if an enclosure is designed with mechanical bracing, excessive wall thickness or weight is not necessary. Weight alone does not do the job. I once made small bookshelf speakers using concrete Chimney blocks for the enclosure walls except for the front and back. Turns out that masonary "rings" and does not work very well. But I have often thought about the subwoofer that you could build using a 1500 gal septic tank.