Yep thats why i threw mine in the scrap pan
Location: Yorkshire
Posts: 4,243
I'm Andr'e.
Yep thats why i threw mine in the scrap pan
That's is so incorrect - not even close to what happens! A decently designed dome tweeter actually emits an even hemispherical wave when fed a pulse but actually that's not unrepresentative of what happens with a music signal. Tweeter output does become more directional as the frequency rises, though.
NPL have posted a short video showing part of the research findings, but the technique goes much further than this in terms of resolution:
Last edited by Ammonite Audio; 26-10-2014 at 15:04. Reason: Clarification and added comments re directivity
So more like a lawn sprinkler then?
Current Lash Up:
TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.
Around 7mm thick is ideal, I reckon. I have some old Russ Andrews Focus Rings ( see http://www.russandrews.com/product.a...ULFJOFCYNGOWZN ) that work very well and which are quite fairly priced. The ring should not be tight to the dome - do that and you end up absorbing too much of the peripheral tweeter output. And, yes you do need to treat the tweeter and supertweeter separately.
Location: gone
Posts: 11,519
I'm gone.
Careful with the materials you use - some (softer) felt can affect the perceived frequency response quite drastically, rolling it off - ime, coarse fibre felt is the best.
There was a US guy on here - diffraction begone - or similar who ran a company that had it sussed very nicely. .... Jim Goulding, that was it! http://www.stereomojo.com/Diffractio...GONEREVIEW.htm
.
Location: gone
Posts: 11,519
I'm gone.
Horses for courses, I suppose. I have a set currently doing transformative work on some old Videoton Minimax 2 speakers which have the same sort of recessed front baffle as the IMFs.
Location: gone
Posts: 11,519
I'm gone.
Interesting. Are they tonally neutral on the Minimax or smoothing a bright treble?
.
The fact that the ring should not be tight to the dome means that I couldn't treat the supertweeter as the inner edge of the wooden grill frame is only about 10mm from the top edge of the supertweeter. I suspect that at my age I cannot hear the supertweeter anyway so I will try a pair of the Russ Andrew's Focus Rings around the tweeter only.
Might it be worthwhile idea to get some thin 1 or 2mm felt and line the inner top edge of the grill frame above the supertweeter?
Maybe worth a try anyway. At £12 it's a cheap experiment. I found this info tucked away on the Focus Ring page on the Russ Andrew's site which tries to alleviate your concerns:
"With speakers placed close to hard reflective surfaces you may hear a reduction in high frequency energy, due to a reduction in early sidewall reflection. At first you may feel that the sound has become 'dulled'. Don't panic! Once you become accustomed to the change, you will hear a noticeable improvement in clarity, depth of image and soundstage focus. The degree of improvement will vary depending on the design and quality of the tweeter."
Looks interesting but diffractionbegone.com is down or no longer exists. Also whilst looking into this I read somewhere that his product was designed specifically for flat baffle speakers.
Location: gone
Posts: 11,519
I'm gone.