When a tweeter is described as "vented", can we presume that it does not use ferrofluid?
Specifically, I am referring to KEF's Uni-Q drivers used on LS50 meta.
Specifically, I am referring to KEF's Uni-Q drivers used on LS50 meta.
All I can say is that nowhere in its descriptions of the development of Uni-Q tweeters does KEF mention ferrofluid.
I don’t think one can make that assumption. And bt vented they usually mean that the poor piece has a hole thru into a larger sealed enclosure behind.
Ferrofluid hangs in the gap and should not be directly impacted by the sealed/TL chamber.
But as Galu suggests, if the KEF had ferrofuild the marketing department would be trumpeting it.
dave
Ferrofluid hangs in the gap and should not be directly impacted by the sealed/TL chamber.
But as Galu suggests, if the KEF had ferrofuild the marketing department would be trumpeting it.
dave
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The Kef tweeter isn't vented "per se." The output of the tweeter feeds into a metamaterial chamber:
https://www.google.com/search?q=site:diyaudio.com+metamaterial
https://www.google.com/search?q=site:diyaudio.com+metamaterial
Not necessarily. All the independent measurements I've seen of the recent coax drivers indicate that they do use ferrofluid. They have very well damped impedance peaks and that usually = the use of ferrofluid.
I made a metamaterial chamber for a NEO3PDR.
Although the metamaterial chamber for the SB26ADC was an absolute Home Run, the chamber for the NEO3PDR did literally nothing.
That was when it "clicked" - the benefits of the metamaterial chamber are likely BECAUSE it flattens the impedance curve.
That realization has been a big part of the reason I've been messing around with ribbons and planars over the last year. I believe that there's likely a correlation between the lack of a resonance in a tweeter, and whether it sounds "good."
A metamaterial tweeter barely has an impedance hump, but planars and ribbons largely don't have a hump at all, because the mass of the diaphragm is so light and the BL of the motor is so high.
Although the metamaterial chamber for the SB26ADC was an absolute Home Run, the chamber for the NEO3PDR did literally nothing.
That was when it "clicked" - the benefits of the metamaterial chamber are likely BECAUSE it flattens the impedance curve.
That realization has been a big part of the reason I've been messing around with ribbons and planars over the last year. I believe that there's likely a correlation between the lack of a resonance in a tweeter, and whether it sounds "good."
A metamaterial tweeter barely has an impedance hump, but planars and ribbons largely don't have a hump at all, because the mass of the diaphragm is so light and the BL of the motor is so high.
Maybe so, but a vented polepiece into an acoustically absorbing chamber (whether it has many small chambers as suggested above or is simply filled with fiberglass) would also contribute to that effect.
I guess only Kef themselves or disassembly can solve the riddle. 🙂
I guess only Kef themselves or disassembly can solve the riddle. 🙂
It is maybe just to say that it has a "vent" (that spreads into a back chamber). Surely marketing description.
Or it has really a vent because it is not a sealed load, i.e. it uses a back chamber which Vas is much bigger than the T&S tweeter parameter (be it ended with a labyrinth or not) to load it BR....which is odds.
Or it has really a vent because it is not a sealed load, i.e. it uses a back chamber which Vas is much bigger than the T&S tweeter parameter (be it ended with a labyrinth or not) to load it BR....which is odds.
Interesting, do you have any drawings or pictures available?
Or some curve with/without?
All of the answers are in the link I posted 🙂
I not only built it and measured it, the inventor at KEF chimed in and corrected some assumptions I made!
Metamaterial is a no-brainer I think, and it blows my mind that:
1) Only two of us on the entire forum have done this
2) There's a dude on Facebook who did something similar, and a bunch of people slammed his efforts (Something that I hate about Facebook technical groups in general is that the quality of discourse isn't as good as it is here.)
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I somehow get the feeling that marketing department are avoiding mentioning it.
Spendor for example, all their current models seem to share the same tweeter. Their older tweeters are known to use use ferrofluid. Currently they don't mention ferrofluid anywhere. But one review here mentions ferrofluid.
https://www.hificorner.co.uk/blog/post/spendor-a5r-floorstanding-speaker-review
So either the review is wrong, or Spendor does not like to mention it.
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The impedance plots without substantial impedance peaks were for non meta, none pole vented, KEF tweeters.
Generally, when using ferrofluid in a speaker the recommendation is to use venting. The ferrofluid seals the cavity under the dome and inside the magnet structure, which on one hand reduces streaming noise from the air flowing through, and on the other hand can cause pressure built up if not vented. So using ferrofluid and not venting would be a poor driver design.