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  1. #1
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    How to make sand bags to weigh down/dampen speakers?

    I was reading a Stereophile review of the Totem Forest speakers, which I will get. The author placed a 25 pound bag of lead shot on top of each speaker and said the bass became much better. Probably no surprise- it will help dampen vibrations and such. I'd like to do the same with my speakers, but I don't like lead. It's toxic and all that. So maybe I could have some sand bag on top of each speakers. And I've run into a bit of a surprising problem: How can I get my hands on some bags to fill with sand? I'm a guy (power tools and such) so I don't know how to stitch cloth together. Maybe I could learn? Where would you start? But I'd rather not. The plastic bags the sand comes in get holes in them all the time. So I'm figuring a heavy cloth, canvas, etc. might be best. The "tube sand" you buy for weighing down pickup trucks is a sort of nylon (or other plastic) bag, but it's too big for this purpose, not to mention really ugly.

    Anyways, any ideas out there for this? Sometimes the simplest things are the toughest to figure out.

    On a related note: If I can figure this out, I might also fill some cloth tubes with sand and put them up against the bottom of the door on the house, to keep out the drafts, as winter approaches.

  2. #2
    Super Moderator Site Moderator JohnMichael's Avatar
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    Quote Originally Posted by JonW
    I was reading a Stereophile review of the Totem Forest speakers, which I will get. The author placed a 25 pound bag of lead shot on top of each speaker and said the bass became much better. Probably no surprise- it will help dampen vibrations and such. I'd like to do the same with my speakers, but I don't like lead. It's toxic and all that. So maybe I could have some sand bag on top of each speakers. And I've run into a bit of a surprising problem: How can I get my hands on some bags to fill with sand? I'm a guy (power tools and such) so I don't know how to stitch cloth together. Maybe I could learn? Where would you start? But I'd rather not. The plastic bags the sand comes in get holes in them all the time. So I'm figuring a heavy cloth, canvas, etc. might be best. The "tube sand" you buy for weighing down pickup trucks is a sort of nylon (or other plastic) bag, but it's too big for this purpose, not to mention really ugly.

    Anyways, any ideas out there for this? Sometimes the simplest things are the toughest to figure out.

    On a related note: If I can figure this out, I might also fill some cloth tubes with sand and put them up against the bottom of the door on the house, to keep out the drafts, as winter approaches.
    I read John Atkinson's follow-up on the Forest. I liked his idea of filling the lower chamber of the enclosure with a mixture of sand and lead so it would still be heavy but not all lead for the concerns you stated. I would not try the sand idea for the top of those beautiful speakers but I would buy two matching heavy decorative pieces of art or sculpture. Reproductions most likely. Adhere some rubber pads on the bottom of the pieces and place them on the speakers. You would have mass loading but a little nicer presentation. Unless you have a dedicated audio room and you can get away with bags of sand.
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  3. #3
    Suspended topspeed's Avatar
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    If you're actually going to do this, I like JM's idea best. I know of one guy that took an extending curtain rod and placed it between his speakers and the ceiling. A couple of turns and that speaker was rock solid. Did it improve the sound? I have no idea. Did it look ridiculous? Yep. IMO, any speaker that needs to be mass loaded should come with chambers to do exactly that (Von Schweikert does this). Totems are beautiful speakers so it would be a crying shame to ruin them by draping bags of sand over them.

    Just my .02 cents.

  4. #4
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    Thanks guys. You're totally right- they are quite pretty speakers. And it would be a shame to put something ugly on them. Like a shower curtain rod- E gad! :-)

    How about some classic red bricks. Maybe put some cloth over the speaker top. And then maybe 4 bricks or so? But they might fall over and damage the speaker side or floor.

    I am building a sub. So any concerns I have of limited bass should go away with that, I'd think.

  5. #5
    Loving This kexodusc's Avatar
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    Not be a skeptic, but..

    Quote Originally Posted by JonW
    Thanks guys. You're totally right- they are quite pretty speakers. And it would be a shame to put something ugly on them. Like a shower curtain rod- E gad! :-)

    How about some classic red bricks. Maybe put some cloth over the speaker top. And then maybe 4 bricks or so? But they might fall over and damage the speaker side or floor.

    I am building a sub. So any concerns I have of limited bass should go away with that, I'd think.
    I really don't buy that the Forests benefited from adding mass. They use excellent cabinet building techniques,and are solid as a tank. Those speakers aren't big enough, and don't produce enough force IMO to justify adding mass. Not only that, look at all the screws holding that woofer in.

    Damping a speaker is a delicate balance. Overdamping is as bad as underdamping. I advise trying them as designed first.

  6. #6
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    Quote Originally Posted by kexodusc
    I really don't buy that the Forests benefited from adding mass. They use excellent cabinet building techniques,and are solid as a tank. Those speakers aren't big enough, and don't produce enough force IMO to justify adding mass. Not only that, look at all the screws holding that woofer in.

    Damping a speaker is a delicate balance. Overdamping is as bad as underdamping. I advise trying them as designed first.
    Right. The speakers have not arrived yet, so I have not tried anything yet. Maybe they'll be OK as is and with my sub. They do have a place in the back for filling in sand. I'm just thinking about this because of the Stereophile review that said they sounded better with some damping.

    So overdamping can be bad as well? Can you explain how that works? Thanks.

  7. #7
    Loving This kexodusc's Avatar
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    Quote Originally Posted by JonW
    Right. The speakers have not arrived yet, so I have not tried anything yet. Maybe they'll be OK as is and with my sub. They do have a place in the back for filling in sand. I'm just thinking about this because of the Stereophile review that said they sounded better with some damping.

    So overdamping can be bad as well? Can you explain how that works? Thanks.
    Damping absorbs unwanted cabinet vibrations, no doubt about it. But if the cabinet is well constructed, dense, and sturdy enough, vibrations can be at a minimum pretty quick. I've built cabinets Too much damping can also absorb acoustic energy. This can manifest itself in a few ways. I think the easiest way to explain the negatives is to think of a single note on a piano being struck. The speaker plays it back. If the cabinet is absorbing too much of the acoustic energy, it's holding on to this note in some form, and eventually releases this energy in some way, harmonics or original frequency at a lower amplitude. I think it's better to have a quick store-and-release, provided you have no resonances, than to hang on to it and release it later, where it could interfere with the sound. Damping can suck out efficiency and dynamics (albeit just a small bit), but it can impact the sound quality in areas of attack and decay as well. Is always noticeable? No.

    I think for the most part, it just adds mass for the sake of adding mass. A lot of studies have been done on cabinet materials and thickness. From what I've seen there's rarely enough reason to go above .75" MDF or a similar density plywood. 1" MDF is probably the most you should ever use. Above that and you're doing more harm than good. Just increasing costs and smothering the speaker. Larger woofers (12", 15", and 18") can bet the exception. There's a ton of energy working itself through the cabinet walls compared to a 6" woofer. Nothing wrong with going as low as 1/2" MDF either, in the right application.

    I built one design using 1/2" MDF to save some money because I ran out of .75" MDF. They were a lot lighter, but I always use mortis and tennon or rabbet joints to connect my cabinets, 3 to 4 times stronger than butt joints. Good bracing and well placed damping material. I couldn't hear a difference just becuase of mass or cabinet thickness.

    Too much damping material inside a speaker can stiffle the lower midrange and bass too. Damping material can have the effect of making the cabinet volume "appear" larger to the woofer.

    There's usually a lot of trial and error that goes into damping a speaker. I trust that most competent speaker designers (like Vince Bruzzese) carefully choose how much to damp their designs long before it ever arrives in the store. Best to stick with that IMO.

  8. #8
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    kex-

    Nice explanation. Thanks for the thoughts!

    I'm pretty new to the whole speaker design game. I'm starting out by purchasing my mains- the Totems. And building a subwoofer. But I'm starting with a pretty easy design- sonotube and a huge (18") driver. We'll put this thing together and see how it goes. But, like you say, regular speaker design is much, much more complicated. I may look around to see if there are any books I can find on speaker design. Could be interesting reading.

    -Jon

  9. #9
    Loving This kexodusc's Avatar
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    Quote Originally Posted by JonW
    kex-

    Nice explanation. Thanks for the thoughts!

    I'm pretty new to the whole speaker design game. I'm starting out by purchasing my mains- the Totems. And building a subwoofer. But I'm starting with a pretty easy design- sonotube and a huge (18") driver. We'll put this thing together and see how it goes. But, like you say, regular speaker design is much, much more complicated. I may look around to see if there are any books I can find on speaker design. Could be interesting reading.

    -Jon
    I recommend a few books:
    Great Sound Stereo Speaker Manual - David Weems
    Loudspeaker Design Cookbook - Vance Dickason
    Designing, Building, and Testing Your Own Speaker System - David Weems
    Speaker Building 201 - Ray Alden

    That'll keep you busy for 6 months at least...they're all available at Parts Express.
    Your speakers are very nice, Totem has always impressed me with their ability to offer excellent sound AND looks for a good price.

    An 18" sonotube is a huge sub...your room must be large....better let the neighbors know...

  10. #10
    BooBs are elitist jerks shokhead's Avatar
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    Quote Originally Posted by JonW
    I was reading a Stereophile review of the Totem Forest speakers, which I will get. The author placed a 25 pound bag of lead shot on top of each speaker and said the bass became much better. Probably no surprise- it will help dampen vibrations and such. I'd like to do the same with my speakers, but I don't like lead. It's toxic and all that. So maybe I could have some sand bag on top of each speakers. And I've run into a bit of a surprising problem: How can I get my hands on some bags to fill with sand? I'm a guy (power tools and such) so I don't know how to stitch cloth together. Maybe I could learn? Where would you start? But I'd rather not. The plastic bags the sand comes in get holes in them all the time. So I'm figuring a heavy cloth, canvas, etc. might be best. The "tube sand" you buy for weighing down pickup trucks is a sort of nylon (or other plastic) bag, but it's too big for this purpose, not to mention really ugly.

    Anyways, any ideas out there for this? Sometimes the simplest things are the toughest to figure out.

    On a related note: If I can figure this out, I might also fill some cloth tubes with sand and put them up against the bottom of the door on the house, to keep out the drafts, as winter approaches.

    Good sub or a 25 lb of lead shot? Let me think.
    Look & Listen

  11. #11
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    Quote Originally Posted by kexodusc
    I recommend a few books:
    Great Sound Stereo Speaker Manual - David Weems
    Loudspeaker Design Cookbook - Vance Dickason
    Designing, Building, and Testing Your Own Speaker System - David Weems
    Speaker Building 201 - Ray Alden

    That'll keep you busy for 6 months at least...they're all available at Parts Express.
    Your speakers are very nice, Totem has always impressed me with their ability to offer excellent sound AND looks for a good price.

    An 18" sonotube is a huge sub...your room must be large....better let the neighbors know...
    Thanks again! I'll have a peek at those books. Not sure I want to try my hand at building main speakers. But it could be fun. I'll see how this sub goes first.

    For the sub, my room is not particularly large or anything. I just figured that if I'm going to try building a sub, it should be a no compromise, over engineered design. It's hardly any more effort or cost to do it right.

    It's not 18" tube- it's an 18" Ascendand Audio Avalanche driver. The tube is 28".

  12. #12
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    Quote Originally Posted by shokhead
    Good sub or a 25 lb of lead shot? Let me think.
    It will take me a while to get the sub built, a few months probably. So I was thinking until then... And if the shot actually helped the sound of the mains, I could always keep it there. But I'll just build the sub.

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