I am currently using six M200s in an active tri-amp stereo application. Since I enjoy experimentation, I purchased some LCY ribbon tweeters to replace the Scan Speak D2905/990000 tweeters in my satellites.

Here's the problem. The ribbons are transformer-coupled and a fraction of the DIY community with whom I've corresponded suggest that I must use a capacitor to AC couple these tweeters. They argue that I could damage the amps or the tweeters if I neglect the cap. Others claim that the cap is optional, but may actually be desireable, since it will insure that the transformer is never driven into saturation. A final contingent thinks that the cap is a bad idea, since it is a superfluous passive component directly in the loudspeaker (tweeter) reproductive chain.

The dealer from whom I purchased the tweeters claims that he has actively driven these tweeters without a cap in several designs, and that even a small amount of DC offset on the amplifiers would probably be a negligable effect.

Of course, if the M200s are already AC coupled, this is a non-issue. Are they?

Please comment on the notion of DC-coupling these tweeters to the M200s in my system.

BTW, I am DC coupling the Scan Speak tweeters now with no problems.

Thanks,
Jim

I don't know if the amp is a direct-coupled design but I suspect not. But that doesn't mean you might not still have some DC offset at the output. You can measure the offset by shorting the amplifier input and probing the output terminals (no speaker connected) with a voltmeter. Normally +/- 5 to 10mVdc max would be considered acceptable but you might feel more comfortable on the lower end of that range if there is concern with saturating the transformer core. If the amp truly is DC coupled then you also need to be concerned about amplifying and passing any DC from upstream components.

I would surmise that the concern about potential damage might be related to any pulses or surges with turn-on or turn-off. If you don't hear any pops with the Scan Speaks you're probably OK here.

I guess if it was me I'd perform a few measurements for piece of mind and then hook it up without the capacitor. After all, isn't that one of the reasons for active bi/tri-amping in the first place (eliminating passive crossover components)? But then if you toast one of those pricey ribbons it's your money not mine. What does LCY have to say on the subject? Proceed with caution I guess.

Good Luck and keep us posted on the results!

In addition to tekdredger's excellent thoughts, I'd also suggest tossing your question directly to Outlaw .

After a tricky bit of hand-router work (for the cabinets) and some SoundEasy measurements, the satellites are now up-and-running using the new LCY 130 ribbon tweeters. No additional blocking capacitor is used and they sound great - even more detailed than my old ScanSpeaks and a wider, more diffuse stereo image - more to my liking.

Thanks for all your comments.

Great! Good to hear you found success. How well do the ribbons hold up sound wise when driven hard, just curious?