[Brian Cheney]

For those of you getting CDWG's for your RM 30's, and anyone else interested in brightening up trebles, these are the instructions for Dehorning Your Tweeter:

1. Pull of gray foam masks on either side of tweeter.  You can remove glue residue with WD 40.
2. Unscrew the four Philips woodscrews holding the tweeter to the front baffle.  Lift tweeter out without disturbing the blue and green wires.
3. Using a metric hexwrench (of the kind found in hardware store sets) take off the four hex screws holding the faceplate on.  Be sure to remove any tape cover over the tweeter first (as found on new tweeters) so you don't create a vacuum which will stretch the diaphragm.
4. Use a piece of tape to cover the diaphragm.
5. Using 2" brass brackets attach one end of one bracket to the upper right screw hole where the faceplate had been attached.  Use one of the hex screws to fasten the bracket to the tweeter.  Similarly attach another bracket to the lower left screw hole of the tweeter.  Do not tighten the hex screws yet.
6. Center the magnet structure in the cutout, swing the free end of each bracket until it contacts the edge of the tweeter cutout, and attach it to the front baffle with one of the Philips woodscrews.  Repeat with the free end of the second bracket.
7. Now making sure that the tweeter is centered in its cutout, tighten the two hex screws tolding the brackets to the tweeter body.
8. Cover the tweeter with the supplied Dynamat masks which will make the tweeter airtight again.  Center the rectangular hole in the mask, peel off the backing of the Dynamat, and press tightly against tweeter and baffle cutout.

The above steps will cause tweeter response to rise above around 10kHz at 6 dB/oct.  The CDWG applies a complementary 6 dB/oct roll off, resulting in flat trebles with the CDWG attached.

Now take off the tape covering the tweeter.

A kit containing four brackets and two Dynamat masks for this procedure can be purchased from the factory for $16 ppd.

Even if you don't have the CDWG you may enjoy the brighter trebles that are a consequence of dehorning, particularly on pop/rock material.

[inRMsway]

Hi Brian, I am puzzled that removing the horn loading face of the FST will make it louder above 10khz. I always thought horns acted as an impedance transformation to the air to release a high pressure into a low pressure. Sounds very interesting to try this. My SPL meter has always shown a rolloff past 10khz on up and yet it is supposed to be calibrated to measure fairly flat. I don't hear much past 14khz anymore, but still perceive when highs are missing or hot up high. So more treble sounds like a winner.  JAY

[Brian Cheney]

The very shallow horns on ribbon tweeters are indeed impedance matching devices.  However, they also have the net effect of flattening frequency response.

A very low mass transducer such as the FST will have a naturally rising response up to the frequency where it mass limits (peaks) and rolls off rapidly, or dies.  Dehorning the tweeter reintroduces the natural rise which the CDWG causes to roll off again, resulting in flat response over a wide angle.

[geraldedison]

Brian,

I went to the VMPS website to look for the dehorning kit for my RM40.  I don't see it listed in the product options. 

Is there a link that I can use to purchase this kit; thanks.

Gerald

[inRMsway]

Hi Gerald, I have a de-horning kit I never used that you are welcome to have free. Just send me your mailing address by text or voice to (818) 903-5024 and I'll mail it to you. Otherwise check with John Casler at bioforce.inc@gte.net or (310) 446-0138 for ordering one from Brian.  JAY

[John Casler]

For those of you getting CDWG's for your RM 30's, and anyone else interested in brightening up trebles, these are the instructions for Dehorning Your Tweeter:

1. Pull of gray foam masks on either side of tweeter.  You can remove glue residue with WD 40.
2. Unscrew the four Philips woodscrews holding the tweeter to the front baffle.  Lift tweeter out without disturbing the blue and green wires.
3. Using a metric hexwrench (of the kind found in hardware store sets) take off the four hex screws holding the faceplate on.  Be sure to remove any tape cover over the tweeter first (as found on new tweeters) so you don't create a vacuum which will stretch the diaphragm.
4. Use a piece of tape to cover the diaphragm.
5. Using 2" brass brackets attach one end of one bracket to the upper right screw hole where the faceplate had been attached.  Use one of the hex screws to fasten the bracket to the tweeter.  Similarly attach another bracket to the lower left screw hole of the tweeter.  Do not tighten the hex screws yet.
6. Center the magnet structure in the cutout, swing the free end of each bracket until it contacts the edge of the tweeter cutout, and attach it to the front baffle with one of the Philips woodscrews.  Repeat with the free end of the second bracket.
7. Now making sure that the tweeter is centered in its cutout, tighten the two hex screws tolding the brackets to the tweeter body.
8. Cover the tweeter with the supplied Dynamat masks which will make the tweeter airtight again.  Center the rectangular hole in the mask, peel off the backing of the Dynamat, and press tightly against tweeter and baffle cutout.

The above steps will cause tweeter response to rise above around 10kHz at 6 dB/oct.  The CDWG applies a complementary 6 dB/oct roll off, resulting in flat trebles with the CDWG attached.

Now take off the tape covering the tweeter.

A kit containing four brackets and two Dynamat masks for this procedure can be purchased from the factory for $16 ppd.

Even if you don't have the CDWG you may enjoy the brighter trebles that are a consequence of dehorning, particularly on pop/rock material.