i may be wrong but if you put lead shot inside speakers that were not designed for it you are taking away from the internal volumn of the speaker as it was designed.
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Very good points and ones that I had not thought of at all.
I saw an add here a few days ago for very small stainless steel discs. I suppose the steel wouldn't create dust like lead. At the very least, it wouldn't be as toxic.
If I remember correctly steel weighs approximately 4oz per cubic inch. Discs would be less, since there is some air space, say 20% less. Hmmm, 100 cubic inches for 20Lbs as a guesstimate. That's a fair amount of volume, 4 to 5 percent of my speakers internal volume, certainly enough to have some acoustic effect.
Nonetheless my curiosity is still piqued.
UNless I miss my guess, mass loading usually involves the stands, or placing bags of the shot or whatever on top of the device, not inside. As for steel, its magnetic and so I don't think it should go inside a speaker with a magnet. As for lead, it highly toxic and I sure wouldn't want it loose anywhere in my home. Bagged only, I say. YMMV.
Elizabeth is right dust would be dangerous to young childrens nervous systems. It may also make you snap for a moment in a rage of anger, & who knows?
First pick up a pair of Sound Anchor Cradle style bases for your Cdm-9nt's, then going from a Bryston 4b-st, to 7b-st mono's will really open up the 9's BIG TIME!!!
The Cdm-9's are fine as is no need to mod them, they just need a major amount of juice to really open them up. I used to own a pair w/ a 4b-st, & 2 Rel Strata III's. Once the 7b-st's where in the system I never felt the need to re-connected the Rel's.
Audiobugged, LOL. You know me well. I certainly dont need anymore rages. The Sound Anchors is a great idea, I am going to look into it immediately. I should have a 4B-SST next week so the amp is going to improve some, hopefully.
Swampwalker, I didnt even think about the steel and the magnets, a potentially sticky situation! I am a diver, and as an experiment I could place my soft bagged lead weights on top. I only have a pair of 5s and 4s (salt/fresh). So each speaker would have 9Lbs on top. Not a lot, but maybe enought to see if this warrants further consideration.
Thanks so much. More thoughts are certainly welcome.
don't worry about lead dust unless you are going to have it in your mouth or i don't think your speakers are powerfull enough to make the shot move around so much as to create dust. there are tons of people who use lead shot in their speakers and have you heard of one problem? plus compare price of lead shot to sound anchors.
Putting metal weights inside a speaker enclosure is obviously a misunderstanding of the concept of weighting down the enclosure by external loading.
But, it brings to mind an idea that I have been kicking around for a while, but never got to try. Carbon dioxide, CO2, is an easily obtained and non-toxic gas that is heavier than air. One could drill two small holes in a speaker, top and bottom, and fill the enclosure with CO2 (slowly from the bottom). After filling plug the holes, perhaps with a cork. The extra weight would not be enough to affect the enclosure structure, but it would change the enclosure loading of the driver, perhaps in a desirable way. If the effect is in the "wrong" direction, one could try Helium, but that gas would tend to leak out (whereas CO2 would not). Has anyone tried something like this?
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.
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.
I used steel coated lead shot in the desgnated base compartments of my VR2s to improve the bass response. It appears to have worked well. The steel coating and isolated chamber should keep contamination at bay. I didn't listen to the speakers at length before adding the shot, because it was recommended by VSA as part of setting them up. I can say that they stage very nicely, therefore, I think the deadening effect, if any, is minimal. I just heard a system that was heavily braced both with lead on top and around the bottom with a total of 4 X 25lb bags per speaker which the owner is certain improved the bass response. I can't be sure if the staging was makedly affected because I never heard the system without the loading.
Audiobugged, I agree, 9Lbs will just be an experiment, I dont expect much. Rewiring and upgrading the binding post sounds like a great "tweaker" project. Thanks for the great ideas.
Maril, I am not sure but you could try a local sporting goods store. They may have coated shot for reloading shotgun ammo. You can also buy small bags of loose lead shot in heavy duty bags at a dive shop, though expect to pay more for it. I also saw some stainless steel here on A'gon a few weeks ago, try a search if you're interested.