After almost two years of experimenting with various ways to tame the tweeter sibilance of the M60’s, I’ve had the best results by simply replacing the factory tweeters.

A little history:

I started with trying different resistors (values ranging from 0.5 Ohm, to 2.7 Ohm). Although they -seem- to tame the highs, they just lower the Axiom tweeter’s output level above the 2 KHz crossover frequency, but the sibilance is still there although at reduced level.

I also tried using wool felt, both outside the tweeter (to prevent a wide dispersion), and inside the metal dome (to try and damp the metallic shrill). I did this by removing the four inner screws that attach the metal dome front plate/voice coil to the magnet, and placing one or two round cut-outs of wool felt inside the dome. The results were of limited success.

The best results I had settled with was using 1.8 Ohm resistors, AND 1 sheet of wool felt (about 1” diameter) inside the metal dome of the tweeters.

I still wasn’t completely happy with the sound since the speakers did seem harsh at times and gave me listener fatigue. I decided to try something more drastic and simply replace the tweeters. I wanted to try a silk dome tweeter since I find the metal ones to be usually rather harsh and unrefined, unless they’re the ones you find on really expensive high-end speakers. After some reading around, I decided to try the Usher 9950-20 1” textile dome tweeter from partsexpress.com. I have no affiliation with either company. They are $90, with $10 shipping. I decided on them due to excellent reviews, the compatible frequency range with the M60’s 2 KHz crossover, and the fact that they are not very picky in terms of crossover design. Yes, yes…I know that each tweeter has different impedance characteristics and efficiency and needs to have the crossover designed accordingly for proper integration with the speaker, but I just wanted to try it for fun and return them if I wasn’t happy. Well, to my ears, they simply outclassed the factory metal domes in every regard. Gone was the harshness but with no loss of detail. The imaging is also impressive. I played around a bit with my Radio Shack SPL meter and didn’t notice any ugly patterns in the frequency response but I didn’t bother making any precise measurements since I found myself simply enjoying the music. No more listener fatigue and not at the expense of resolution or imaging…I wanted to play track after track and I found myself even listening at higher volumes than before. I always listen with the grills off since I find them to give a ‘curtain’ effect to the sound. What was noticeable was that now the high frequency information was better resolved than with the factory tweeters, especially on complex passages. What a treat! The Ushers are here to stay…gone are the resistors and felt.

In terms of mounting, the Usher’s four mounting holes are compatible with the Axiom tweeter so it was easy to install using the same screws and cabinet holes. The Usher’s front plate is a few millimeters wider than the Axiom’s so it doesn’t sit inside the cabinet cut-out, but I didn’t find that to be a problem in any way. The Usher tweeter magnets are a bit wider, but they still fit in the cabinet opening. The Usher’s two electrical tabs are wider than the tabs on the Axiom tweeters, so to mate them I made two pairs of 2” long 20-gauge wire with the appropriate sliding contacts on each end to mate the speaker cables to the tweeters. The polarity is such that the blue wire from the Axiom (the one with the wider sliding contact) should go to the connector on the Usher that has the red dot next to it. You can confirm that this is the correct polarity by playing a 2 kHz tone (the crossover frequency of the M60’s), and move your head about 1’ from the front of the speaker up and down between the mid-woofer and the tweeter. Half-way between the two, if the polarity is correct, you’ll notice the sound being louder (if you reverse the polarity, there would be a dip in the loudness in the half-way point due to destructive interference of the sound waves). Be careful when you handle the Ushers to no touch the soft dome…Do not poke it!

The other tweak I did was to raise the front of the speakers by almost 1” using a bunch of metal shims I bought for $2 at a hardware store. I placed them between the front two rubber feet and the speaker cabinet. The axiom supplied screws are long enough to accommodate the extra length. This makes the soundstage a bit better since you’re not ‘looking down’ as much on the performance.

Since this direct tweeter swap is (to my ears) a clear improvement, I can only imagine how it would be if Axiom had actually designed the crossover around better quality tweeters like the Ushers. I think most people would be willing to pay a $100 premium given the gains in sound quality. I know I would.

Last, take what a said with a grain of salt before you go spend $100 and accuse me of wasting your money. I don’t encourage anyone to try this. However if you do decide to give this a shot, note that the Axiom screws can scrape the paint of the Usher front plates in the area under the screw when they are tightened down. So if you want to be able to return them in mint condition, use a washer or be gentle with the screwing down force in order to preserve the black paint in the area inside the mounting holes.

The setup is purely for stereo. Amp: Musical Fidelity A308 Integrated. CDP: Three Sony CDP-CX455 400 Disc Changers. Rack: Salamander Synergy.

Merry Christmas!