I have the Townshend Super Tweeter, got them last summer from Max here in the UK. They are incredible. Once you have them in your system, you are hooked. They are smaller than a CD in lenght and about 2" wide,x 4" long, come in chrome. Here is the best thing they have a dial control with 8 increments,on the back.((( I think this is a must.))))) I have mine set at 2, could go to 3 or 4 for classical. I find the setting 2 works with all musik. I have mine sitting on top of my Infinity Preludes that is 57" off the floor not a problem. I did set them at 38" off the floor when I got them , but didn't seem to make a big difference.
You will hear music off your cd that will shocked you. All I can say is once you have these little expensive STweeters in your system, just try to turn them off.
I'm not sure who sells this in the US, www.townshenaudio.com
If you get a chance give them a try !
I found the spec sheet , here's what Max says about The Super Tweeter they are designed to extend the responce of conventional HI-FI speakers to 100 KHz, by adding these super Tweeters you will gain the advantage of the extended frequency reponce delivered by the new digital audio formats SACD, ( which I have) DVD-A ,96/24 PCM and DVD-V and to fully utilise the 30KHz plus frequency reponce previously only available from high-quality vinyl reproduction.
The low frequency -3db point of the first order crossover is set at 20KHZ. For speakers with sensitivity of 80db to 110 db. I took this off his info sheet.
Cheers