cut down tweeter highs

I'll be the first to admit I'm not an audio specialist, but I do know a lot about electronics and since you haven't had a reply, I'll put my 2 cents worth in and make a suggestion.  

I would not put a resistor in parallel with the speaker, as that would change it's impedance.  Impedance being overall AC resistance, including reactances, paralleling a resistance will lower the overall impedance, just like putting two resistors in parallel would lower overall resistance. 

In looking at some of the other resources available here, I was wondering if a low-pass filter ( as described in the cross-over section) would be the answer?  You could calculate the audio frequency where you wish to begin attenuating the signal and build the filter to match that.  Or if you're presently using a cross-over, you may be able to change some of the components or add a "high-cut" filter to it, or even use a band-pass filter.  Of course, you could use whatever order of filter design you needed, depending on how quickly you want the signals to drop off.

I am not familiar enough to know what products are readily available on the market to buy to do this, but building one would not be very difficult.  Primarily it would involve finding the right size coil or choke to add into the line if you just wanted to cut the highs.

Maybe this will help a little.

An L-pad will work fine if you just want to cut the overall volume of the tweeter, but I took you to mean that you just wanted to cut the shrill highs, sort of take the edge off it, rather than tone down all treble sounds coming from the tweeter.

On this site, they have calculators that do a nice job of determining the size coil you would need to just take that edge off.  I tried it, using 4 Ohms and 16,000 Hz as the crossover frequency, and it showed me the exact mH coil I would need for such a low-pass filter.  You should be able to find a coil very close to that (they say within +/-5% will work) at most electronic supply houses.  It would still allow the treble frequencies below that point to come through unaltered, but above that point it would begin attenuating them.  They've got good info on doing this.

I'm still kind of new to this site, but I like it more everytime I get a chance to explore it a little more.  Hope this helps a little.

Hey superspeed,

Resistors in series would do the trick,  I've done it more than once.  Keep them large enough to prevent overheating.   Hey now you know why they call them FANATICS!