Lead shot questions

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.

Tom, I certainly dont want that. I dont really have any complaints about the Bass, this just seemed like an interesting experiment. Chances are, unless something dramatic happens when I place some weight on top, that I will NOT be opening up the speakers to place weight inside. Thanks for you thoughts and experience.

Eldartford, ohh rest assured the Beer gets first dibs on that CO2. Bottling and priming is a huge pain in the, well yunno, and besides you have to have some pressure to get the beer out of the kegs. Clearly this is the most crucial use =).

That port tube goes pretty deep. I could loosen a driver, fill via the port, allow the air to escape through the driver hole, tighten the driver, and plug the port. I will certainly forward my observations to you if I perform that experiment.

Thanks for the further explanation of mass loading. It isnt the first time I have misunderstood or misused audio terminology. Now that you mention it, I recall reading something on mass loading passive radiators with specific weight to achieve the desired results.

Its not a cure for the bass or any other frequency..Its a sponge that sucks the life out of the speaker or the stand filled with shot underneath. The lead is not sensitive to any selected bandpass of frequencys..They all become screwed up.Tom

If I hadn't upgraded to Talon Khorus's, I would have upgraded the cheesie binding posts on the Cdm-9nt's to Silver WBT's. Then while inside I would have re-wired them with siltech wire with an iternal jumper. I really don't think 9 pounds of lead atop would aid this speaker.