This was asked here not that long ago. The link is below:
Re Coins: I found that the sonic benifits of nickles far surpassed pennies. I think it must be the different metals. Quarters, on the other hand tend to smear the top end. I think becuase they are a sandwich of metals. If anyone has tried pre '75 quarters (silver) I'd like to know how they work out.
Try getting some nylon nuts and bolts from your local hardware store. Screw out your spikes and screw in the bolts (cut them to proper length - don;t keep them too long). Us the nuts to secure them once levelled. These will not harm your floor and will actually allow you to slide and move the spekers very easily on the wood, if necessary.
Twoonies! What is a Twoonies you may ask? A Canadian 2$ coin, this a
revolutionary component engineered of dual metal structure. Additionally,
It's increased circumferential a diametrical dimensions provide extension
into the low end frequency range. In general expect greatly improved
sonics across all frequency ranges when compared with the standard US
coin mentioned above.
As with all things in this hobby and as everybody knows, the higher the cost
the better! A set of eight, will set you back USD 15.40 that's 15$ more than
You can also try Euro coins, but these tend to sound bright, especially since
the Greece debacle.