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Spikes?

 

Unregistered guest
Hi all, I just stumbled onto this forum in my search for some more information on what spikes are really used for. I thought they were used to decouple the speakers from the floor, but so far I've learned they're to couple the speakers to the floor.
Anwyays, the reason why I'm wondering about this is because my room resonates on certain bass frequencies, making it tough to hear what note the bassplayer plays sometimes. I'm a musician so it's important for me to be able to hear that correctly for when I need to learn songs from CD.
I thought spikes would be the way to go but now that I've learned that they couple speakers to the floor won't that make the problem worse?

Btw, I live on a 2nd floor. It's an old building, the floor is made of wood, then there's some isolation material and placed on top of that is carpet.

Any help would be greatly appreciated!
thx!
Steven
 

J. Vigne
Unregistered guest


What you are hearing is the resonant room nodes and they are mostly unavoidable. They are based upon the dimensions of the room against the resonant frequencies that are excited by the specific dimensions. You can find out more about room nodes by putting things like "room nodes", "resonant nodes" or "room acoustics" into a search engine. The room will resonate when a sympatheic frequency is hit no matter what you do. There is some advantage to be had with speaker placement as it can affect the amount of bass present in the room. You can also try a diiferent room that would have dimensions other than your present location. If, however, you wish to keep the same speakers in the same room you will have some resonances. How much you hear them is determined by the amount of damping you can do to an existing room. For the most part room resonances are best dealt with on a case by case basis. Find what vibrates and damp it. You can use cork, rubber or PlastiTak to secure items that vibrate. If it is the wall that is set in motion there isn't much to be done with it short of reconstruction. You might invest in a good set of headphones instead.

Here's some information on spikes and there effects:


Question:

"They (the speakers) do wobble around, 'cos they are not the most expensive speakers on the planet. I do think they could be improved upon at relatively little cost.

So, do you think it would be a better idea to make some weights to put on the top? I saw some advertised years ago, but I'm handy enough with wood to make some nice matching boxes that can sit on the top. Fill 'em with sand, or perhaps even cast in some concrete; lead; bricks - god - anything would do as long as they're heavy and stained nicely to match.

Thankyou for warning me about this."

-------

Response:

"Excuse the sound of the response; but, what you do depends upon what you are trying to do. In other words, if you are merely trying to add mass to the speaker, you can easily achieve that goal by placing weight on the top of the speaker cabinet. Two things to consider though are; 1) is the speaker well secured to the surface it sits on and 2) will weight at the top make the speaker unstable?
First, by using spikes you are mass loading the speaker to the surface beneath the cabinet. You have taken whatever weight the speaker has and you have put all of it on the tip of a few spikes. That means the effective mass loading is greater than the weight of the speaker. Kind of like the idea that a runner puts several hundred pounds of pressure on their knees and heels each time they put their foot down. So those spikes are important when they are levelled and placed on a solid surface. The way to tell whether you have achieved the desired results with spikes is to, before the spikes are in place, push on the top of the cabinet in several directions to see how much movement you can elicit with the speaker just sitting on the floor. Most speakers will have some play in this area. When you have the spikes in place and levelled, try pushing again and it should feel, if things were done correctly, as if the speaker is bolted to the floor. This works the same no matter the weight of the speaker itself. If the speaker still wobbles in the slightest amount without you trying to push it over, you need to do more to level the spikes until you get the locked in feel.
The idea of puting the speaker on top of felt pads is counterintuitive to what spikes are trying to achieve. Allowing the speaker to have movement in the cabinet will decrease the focus of the speaker as it will want to wobble when you play music above a whisper. The decoupling is OK if you're in an apartment and not trying to meet your neighbors at 2 A.M. but, otherwise you want the speakers to be secured in their position.
Second, by placing the weight on top of the speaker you are placing mass at the point where it is the most likely to make the speaker unstable. The lower the center of gravity the better, the higher the C.O.G. the less stable the speaker will become. So a weight on top of the speaker may help some but, it has the potential to do damage to what you are trying to achieve with the spikes. Remember that the spikes are securing the speaker to the floor with a downward force that is greater than the weight of the cabinet, so you have "increased" the mass of the speaker in virtual terms with the spikes. How much will additional weight help? Well, only you can tell. I think I would just try some weight on top of the speaker and see what you think you are hearing. If the weight is helping just by being weight then you can think about how to make that weight work without making the cabinet less stable. If, on the other hand, the weight is acting as a damping device and taking down cabinet vibrations, then, no matter how much weight you add, you still have a cabinet that is making noise. This is much more common than a speaker that just needs more mass. I've used bags of lead shot and/or diver's weights to tame the boxes on speakers; but, of course, each case of how to go about this is different depending on the speaker and the "look" that is acceptable. Not everyone is going to enjoy 10 Lb. diver's weights sitting on top of their speakers. Of course, if they were enclosed in a nice box with some sand poured in around the weight to keep it from resonating/vibrating that might work.
The vibrations in cabinets are usually worse on the long panels (normally the sides) and you have to decide how to deal with that on a case by case situation. It works well, with bookshelf speakers, to turn the speaker on its side and use weights on the side panels.

Let me add this postscript, if you want to add something to the bottom of the speaker you can use what is called BluTak or PlastiTak, etc., and this will create a bond that is very strong, does not allow lateral movement, but, will allow you to lift the speaker off the base easily. You can find this material at hardware stores or from several of the after market audio stores like Audio Advisor.


*********


Hope that helps.






 

Steavis
Unregistered guest
J, thanks a lot, that helped me a lot. I have the feeling that most of the resonances are coming from the wooden floor and/or ceiling and doing a complete reconstruction is simply impossible so I'll have to live with it I guess. The other rooms in my house are even worse sonically, so that's no option either.

I did install some spikes on the speakers today just because I got curious, it did seem to help a little. The bassfrequencies seem to be more even and I got more high end but the problem of the room resonances are not gone of course.

Because of the carpet and the soft underlaying isolation material the speakers still wobble, even with the spikes installed. Would using a tile of marble or something like that help and give me a better sound? I thought using a tile of marble was always used as some sort of 'last resort' for when nothing else works.. :-/

I'll do some searches for resonant nodes and room acoustics! Thanks...I find this stuff interesting! :-)

Steven
 

J. Vigne
Unregistered guest


The way spikes work is to have them reach the floor. If you place them on a piece of marble that is sitting on the carpet you have merely created a platform that is going to wobble. If you have spikes in place and the speaker still wobbles you have two possible reasons. Either the spikes are not long enough to go through the carpet and pad or you have not levelled the speaker with the spikes. In the first case a spike should pierce the material of the carpet and pad since the point of the spike is small enough to go through without damaging the material. In the second case I am assuming you have adjustable spikes. If they are not adjustable you will have to use something to build up the end of the spike that is too short where it goes in the speaker. If the speaker still wobbles with the spikes attached you are not getting the full benefit of the spikes.



 

Bronze Member
Username: Stuermer

Post Number: 13
Registered: Oct-04
steavis:

sounds like you need to experiment with placement of your speakers to reduce the sympathetic resonances.

give this a try
http://www.goodsound.com/howto/2002_08_15.htm
 

Steavis
Unregistered guest
>The way spikes work is to have them reach the floor. If you place them on a piece of marble that is sitting on the carpet you have merely created a platform that is going to wobble.

Of course...!!

I adjusted the spikes and the speakers wobble a lot less now, they have more of a 'locked in' feel. The bad part though is that the isolation material used underneath the carpet is so thick that the spikes will never ever cut through it. I guess I have to live with it the way it is now. It *does* sound a lot better already with the spikes the way it is now.

Tom, thanks for that link, I'll read that page tomorrow (I live in Holland and it's 1:44 AM right now and I need some sleep... :-))

Steve
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