felt

[shep]

I remembered that I treated a pair of speakers with felt surrounds, both around the tweeter and the midrange. So I had some self-stick kind-of-felt and I'm giving it a try on my TL's. It's not very thick and probably not very absorbant but easy to remove. The cabinates are very slim so maybe this is totally unecissary. I only had enough for one speaker but I hear something...bad or good remains to be seem. I will get anoth sheet of the stuff tomorrow. Any body have experience with this tweak?

[richidoo]

When it was a rage on AC I tried it on my Legacy Focus speakers. I taped socks around the tweeter.

I learned that, for my speaker anyway, the reflection off the baffle is an intended part of the voicing of the speaker. Absorbing the reflections attenuated the treble too much. But the treble was a little clearer without the reflection. Since the Focus 2020 was not so focused that focusing the treble would "bring it to another level" it just made the speaker dull.

I think the ideal way to treat this HF reflection problem is to surround the tweeter with spherical enclosure, or narrow baffle, or angled corners, and other various ways to minimize reflection and diffraction with geometry.  But even a big flat baffle speaker like AudioNote or Harbeth has nice treble due to the XO voicing. So I don't know why some report such a big improvement with felt, unless they prefer a little attenuation. In that case, felt might be a little better than a resistor because it controls the reflection while it attenuates. Wilson uses felt around tweeters.

If there is a padding resistor on your tweeter shep you might want to reduce the value of that slightly to bring the treble level back up after the felt is added.

[shep]

Thanks. If the attenuation is too much, I'll just remove the felt. The crossover is too delicate to take out. It's a mass held together with hope and not much else since I had to butcher it to change the caps. Just a little experiment for the hell of it.

[richidoo]

Have fun!

[rollo]

Felt can be very affective in taming a tweeters difussion. I believe Jim Gouldring sells these felt surrounds. I have Forgotten his website. From what I have heard they work very well.


charles

[Face]

This it? http://www.diffractionbegone.com/

$59 for a shipped pair, ouch!

[rollo]

This it? http://www.diffractionbegone.com/

$59 for a shipped pair, ouch!

  Thanks Face.


charles

[richidoo]

Now you know why I used socks! 

[BobM]

I got some cheap felt from a fabric store (aka - my wife's fabric stash) and cut a piece off to try around my tweeters. It did diffuse the highs ... to the point of everything sounding dull and lifeless and extremely rolled off. But it was a good experiment because I figured out the following.

- there is more effect the closer the felt is to the edge of the tweeter dome itself (I have a Scanspeak 9300 soft dome).
- a little dab of felt to the screwheads on the tweeter faceplate made a very big and noticeable difference
- placing the felt just outside from the edge of the tweeter faceplate made a little difference, but screwed up my imaging and soundstaging.

My speakers are MTM's, so in a TM or TMM design you may experience something different from what I found out. In my case the felt didn't work very well and interfeared with what an MTM is supposed to do (i.e. focus all 3 drivers to sound like a point source).

Experiment cheaply before you put down any real cash.

Enjoy,
Bob

[shep]

I can't say it did anything bad so I leave it on for the moment. I may try the idea with the screw heads later.
Thanks for the feedback. If anyone has tried to cut thick felt accurately, it's a bitch, which is why I opted for the thin, self-stick variety, whch isn't real felt anyway but some synthetic stuff, much denser than the real thing.

[richidoo]

Nice tip on the screwheads Bob.  Any small protrusion or hole will screw up the highest frequencies which treat a tiny hole like a cabinet edge.  Thanks for that one!

[tmazz]

Nice tip on the screwheads Bob.   Any small protrusion or hole will screw up the highest frequencies which treat a tiny hole like a cabinet edge.  Thanks for that one!

I knew there was a reason we kept Bob around.  

My only concern is that if you are dealing with a design from a true high end company, many hours were spent voicing and tweaking the design, so any discontinuities in the front surface were in the prototype and their effect we taken into account during the actual listening evaluations and any modifications that came out of those sessions. 

That said, it doesn't mean that the sound can't or won't be improved by the mod, but there is a chance that the effect of the screws was compensated for in some other way and damping out that effect could have a negative impact on the overall sound. I would  (and probably will) try it, but recommend that however you put the felt on, make sure that it can come off easily if you don't like what you hear (no crazy glue.   )

[StereoNut]

I would  (and probably will) try it, but recommend that however you put the felt on, make sure that it can come off easily if you don't like what you hear (no crazy glue.   )

Audiophile Math:

Any glue + Tom (tmazz) = Crazy Glue   

SN

[rajacat]

I made these defraction devices with 3/8" wool felt ordered from http://www.mcmaster.com/#f13-felt/=9g3m02

I used an utility knife with a new blade in place. It wasn't particularly easy to cut the bevel for the "waveguides" . Nevertheless, despite not being exactly perfect, the imperfections are not obviously visible. You can get this felt with a self adhesive which may or may not be hard to remove. A way around this is to use blue tape on the speaker baffle and then cut out a bit of the  self adhesive cover  to stick the felt to the blue tape thereby avoiding a potentially messy cleanup job. I regret that I didn't use this solution instead of ordering the felt W/o the self adhesive and having to hassle with Velcro and other stuff to mixed results.  Since my Omega Hemp Bipoles have a relatively large baffle the felt probably has a more profound impact than with many other speakers.



I did notice an approval in SQ with better imaging being the most obvious benefit.

-Roy

[Response Audio]

In most situations, felt will have a negative impact on a speaker that was not voiced with felt in mind, or a least a noticable change in output which means an improper integration of drivers. Speakers you see with felt applied as a standard are designed this way from the beginning.

In regard to the screws, you can get the same result by simply applying a small piece of tape over the screw heads or any other device hanging out around the tweeter. This is why tweeters and the screws that hold them in place should be counter-sunk. Same applies for midrange drivers depending on where their x-over region is.