I will take the liberty to answer for Lars: No: because the driver was designed by seasoned designers knowing their stuff, applying COMSOL, and not by the Marketing Dpt.
I wonder if it will need a serie notch for the Al break ups or if it was designed for active DSP in mind ?
My daily Al tweeter is a boston acoustic from the high end Lynnfield serie, made with the dome and voice coil made from one piece with a passive Helmotz resonator made from mini tubes in front of the dome. A sorta of meta material long before Kef but for the front wave. I found it was elegant...
BtwI never understood if Be had more detail than Alu because the breaks ups are higher in the band or if it was because the said internal damping or vibratory behavior of the surface because the stiffier material at iso weigth?
IME, the tweeters have more changes than others drivers according the passive filters elements, so I like tweeters that can be passive filtered with 12 dB filter without too much added correction. But I am aware passive filtering (and the ridiculous price of passive parts noadays) is going to be an history of the past VS DSP.
Anayway, looking forward to read the results. But Hificompass, there is also Dibirama in Italy which I like for the measurements made with Clio...
cheers all.
My daily Al tweeter is a boston acoustic from the high end Lynnfield serie, made with the dome and voice coil made from one piece with a passive Helmotz resonator made from mini tubes in front of the dome. A sorta of meta material long before Kef but for the front wave. I found it was elegant...
BtwI never understood if Be had more detail than Alu because the breaks ups are higher in the band or if it was because the said internal damping or vibratory behavior of the surface because the stiffier material at iso weigth?
IME, the tweeters have more changes than others drivers according the passive filters elements, so I like tweeters that can be passive filtered with 12 dB filter without too much added correction. But I am aware passive filtering (and the ridiculous price of passive parts noadays) is going to be an history of the past VS DSP.
Anayway, looking forward to read the results. But Hificompass, there is also Dibirama in Italy which I like for the measurements made with Clio...
cheers all.
I would not be surprised if the datasheet will show an passive filter example if i anticipate well the customer focus of Purifi-audio.
Also, with active dsp i am using now i am considering adding passive elements to surpress cone breakup.
In other posts on this forum it was made clear that an rlc in series with driver helps and that cannot be replicated in dsp.
also true for alu midrange .
In other posts on this forum it was made clear that an rlc in series with driver helps and that cannot be replicated in dsp.
also true for alu midrange .
Member
Joined 2003
Does anyone have any data showing a series notch on a tweeter breakup making a meaningful difference at audible frequencies? A friend took some measurements of Seas DXT, with series notch, sine sweep HD and multitone IMD results showed no meaningful difference <20kHz. Not that the $5 of components required is a big deal, but part value starts to get very particular at these high frequencies, small difference in tolerance of passive components or driver coil winding can throw off the notch quite a bit. Interested to see some real data supporting this use case for filtering, not subjective opinions.
I am also skeptical. Almost all the hard dome tweeters have their first breakup mode at 20 kHz or higher. I would not bother suppressing that kind of peak.
Now with midrange and woofers, the story is different. There is a lot of value in using an RLC passive filter to suppress for example a 6 kHz peak from a 5" cone.
F.i. a sb26adc has a breakup peak at ~25kHz, so first mode could be at 12.5kHz which can be audible.
That is why i want to test it.
For my ptt4.0m08-nac04 the breakup peak is at 8kHz, i expect that to be more audible. The active filter is at 3.6kHz and 1 octave up down to -200db or so, but still close to 8kHz. Thus expect someting at 4 and 2 kHz. So interesting test ;-)
The question i have is that the peak is the second mode of the breakup, the first mode causes a dip. So what is the best approach, i do not know.
That is why i want to test it.
For my ptt4.0m08-nac04 the breakup peak is at 8kHz, i expect that to be more audible. The active filter is at 3.6kHz and 1 octave up down to -200db or so, but still close to 8kHz. Thus expect someting at 4 and 2 kHz. So interesting test ;-)
The question i have is that the peak is the second mode of the breakup, the first mode causes a dip. So what is the best approach, i do not know.
Member
Joined 2003
First mode at 12.5kHz...how so? First node will be 2nd order excited by 12.5kHz, occuring at 25kHz. 3rd mode excited by 8.3kHz will also occur at 25kHz. It all occurs outside of the audible band. If anything, intermodulation may show something, but test on Seas DXT came up empty, with last time of multitone sequence near the breakup peak.
I've gone through the notch evaluation in detail, and adjusted filters of most any speaker in my house to include it, benefits are clear and audible for drivers where breakup occurs at audible frequencies, midrange/midwoofers...
I've gone through the notch evaluation in detail, and adjusted filters of most any speaker in my house to include it, benefits are clear and audible for drivers where breakup occurs at audible frequencies, midrange/midwoofers...
Attached. This was part of the old Tafal project with (IIRC) a modified H0883.
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Would you mind please to link to that specific post making this clear - I have been curious about this...
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https://purifi-audio.com/blog/app-notes-2/low-distortion-filter-for-ptt6-5x04-naa-11
You basically need a high impedance 'blocker' for the VC current at the main cone mode / resonance to prevent the distortion amplification lower down the range. A few of us have been doing this for a while, but it's only been since Purifi started discussing it a few years back (doing everybody a big favour in the process) that it's had much wider attention.
You basically need a high impedance 'blocker' for the VC current at the main cone mode / resonance to prevent the distortion amplification lower down the range. A few of us have been doing this for a while, but it's only been since Purifi started discussing it a few years back (doing everybody a big favour in the process) that it's had much wider attention.
@tmuikku @lrisbo @markbakk
Here some preliminary results from a friend you might find very interesting! 🙂
He's currently working on a loudspeaker with a Seas DXT tweeter.
So we took the opportunity to see if the passive notches would also work for tweeters.
The Seas DXT specifically has a pretty nasty peak around 26kHz.
First just the DXT tweeters as is:
Only the distortion is show in the graphs btw, don't look at the distortion numbers in the legend.
Yes, that's an awful lot of higher harmonics still around 3-4kHz, ewww 🙁
(although levels are pretty...
Here some preliminary results from a friend you might find very interesting! 🙂
He's currently working on a loudspeaker with a Seas DXT tweeter.
So we took the opportunity to see if the passive notches would also work for tweeters.
The Seas DXT specifically has a pretty nasty peak around 26kHz.
First just the DXT tweeters as is:
Only the distortion is show in the graphs btw, don't look at the distortion numbers in the legend.
Yes, that's an awful lot of higher harmonics still around 3-4kHz, ewww 🙁
(although levels are pretty...
Member
Joined 2003
You guys seem to be missing the point of my inquiry. I'm asking specifically, why should I care about reduction of harmonic content at 25khz through use of a notch filter? Image above of DXT might look "bad", but all the "Bad" stuff is at 25kHz range, show me something that occurs at <20kHz please.
My evaluation, for reference:
https://www.htguide.com/forum/forum...asonic-tweeter-filters-for-peace-of-mind-only
My evaluation, for reference:
https://www.htguide.com/forum/forum...asonic-tweeter-filters-for-peace-of-mind-only
Member
Joined 2003
See my post above, and the links: the point of notching the HF resonance has nothing to do with lowering HD at that frequency. It's done to lower the resonant amplified distortion lower down in the audio band. So in the case of, say, an unfiltered 25KHz resonance, you will likely encounter a spike in HD3 at 8.33KHz, F5 at 5KHz & so on, which will be reduced if you add a high impedance notch on the HF mode -you can see that clearly in the animated gif I provided above. The old H0883 had its main dome resonance at just over 26KHz: you can see the spike in HD3 at about 8.7KHz resulting from this, and how it in particular (but overall HD3 too) is significantly attenuated when the HF mode is notched out. And so on & so forth. It's exactly the same method more commonly [these things being relative 😉 ] used on midbass drivers for the same purpose. It just happens to be higher in frequency.
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