Could You care to explain what has led You to apply the same surround on mid and midwoofer (I only noticed higher Cms)? It would be quite logical to think that one can ask for as smooth and non existent surround as possible on transducer that suppose to be used with very little excursion.
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I think that the link refers to some kind of scientific research, or at least, it appears to be the way it is intended to be understood. I have not seen any documentation that shows how they have performed these tests, how they have challenged this conclusion, and how they view research that concludes differently. This should be a mandatory part of anything that is referred to as research. It simply smells a bit too much of confirmation bias to me.
@Snickers-is: are you referring to the findings of Earl Geddes or some other quotation? That is all I am asking. I simply was -and still am- unsure what you were referring to.
Oh, I see, in Mr @digitalthor 's post, just before mine, he links to a thread in his post #975. That thread is what I am referring to.
piotr z et. al. there is a lot of good info on the surround in the Erin's Audio Corner YouTube interview LIVE! with PURIFI Co-Founder Lars Risbo! - YouTube.
At time 44:25 begins discussion of cone, surrounds, and other ‘soft parts’ optimizations. LIVE! with PURIFI Co-Founder Lars Risbo! - YouTube
Then at time 46:27 Erin asks question beginning discussion of Purifi’s very unique surround. Lars begins answer with Christmas disappointment anecdote about how after making major improvements in magnetic circuit and motor hoped for distortion reduction ‘barely moved’. This led to investigations into distortion contribution by the surround flying under the radar. Again this led to rediscovery and use of research industry previously ignored.
LIVE! with PURIFI Co-Founder Lars Risbo! - YouTube
Speaking for myself I find it telling the sometimes visceral reaction to Purifi’s unique surround. Confirms my belief that regardless of what they say many buy HiFi with their eyes not ears. Personally my initial reaction was also 'want??!!' while recalling similar surrounds on niche Fostex drivers and 18Sounds 6ND430. Hasten to add I do not know if those are to address distortion due to dynamic Sd changes. On Purifi’s surround I follow the use of AI in the broader CAD and multiparameter simulation with AI engineering world and when I look at the surround I see a design optimized using FEA and tools like COMSOL Multiphysics CAD. With that perspective 'odd' changed to 'cool and high tech state of the art'.
I'm aware of that what's known about this surround. My question was rather - why surround has same geometry despite different working conditions? Surround in midwoofer has to take around 3x bigger Xmax than that of Mid. Also I'm not so sure how such surround affects diffraction. When it comes to Mid surround I had quite a different idea of how to solve such problems 😉 (quick and dirty paint).
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As Lars pointed out earlier, and as KEF have done with their little KC62, the warped surrounds also add strength to the surround when drivers are used in sealed cabinets and the air pressure inside is trying to blow out through the surround (soft parts). This may be another contributing factor to the midrange consideration.
Remember, the industry masters are so far into driver engineering design that the absolute smallest changes for things that have been ignored (like minimal xmax for mids) are no longer being ignored in the pursuit of perfection.
That, and using the same (ultra low distortion) surround for the midwoofer and midrange drivers probably saves on costs.
Remember, the industry masters are so far into driver engineering design that the absolute smallest changes for things that have been ignored (like minimal xmax for mids) are no longer being ignored in the pursuit of perfection.
That, and using the same (ultra low distortion) surround for the midwoofer and midrange drivers probably saves on costs.
Well, look what I found Purifi-6R
Perfect resource for those who just want to own Purifi sooner rather than later and strawman for the keyboard warriors to take aim at. I'll start the latter by saying I am certain this design would sound better if it was a 4-way using any random 10" or 12" woofer and a 3" dome midrange that only presently exists on Russian hifi forums.
Confirmation bias demands I add this quote from Troels' text:
Playing this rare Musica Nude vinyl recording, which I played hundreds of times, immediately made it clear this mid-woofer is special. Resolution was the first superlative that came to mind. I also know that whenever we introduce a new driver, we'll always hear something we didn't hear before. But having a ruler flat mid- to lower-treble response made it clear it wasn't just a peak or whatever that might have brought some details to life, rather a genuine ability not to smear the signal it is fed.
Clarity and resolution all indicates low distortion. Accuton C173 also came to mind, but without its distinctive character to the sound. Now, the Purifi doesn't work alone, the clarity of the Viawave ribbon defines the timbre of any basic note. Without overtones we don't have the tonal characteristics of any instrument. So, what counts the most? We can't tell, but only conclude these two drivers make a great couple crossing over around 2.2 kHz thanks the wave-guided ribbon.
Perfect resource for those who just want to own Purifi sooner rather than later and strawman for the keyboard warriors to take aim at. I'll start the latter by saying I am certain this design would sound better if it was a 4-way using any random 10" or 12" woofer and a 3" dome midrange that only presently exists on Russian hifi forums.
Confirmation bias demands I add this quote from Troels' text:
Playing this rare Musica Nude vinyl recording, which I played hundreds of times, immediately made it clear this mid-woofer is special. Resolution was the first superlative that came to mind. I also know that whenever we introduce a new driver, we'll always hear something we didn't hear before. But having a ruler flat mid- to lower-treble response made it clear it wasn't just a peak or whatever that might have brought some details to life, rather a genuine ability not to smear the signal it is fed.
Clarity and resolution all indicates low distortion. Accuton C173 also came to mind, but without its distinctive character to the sound. Now, the Purifi doesn't work alone, the clarity of the Viawave ribbon defines the timbre of any basic note. Without overtones we don't have the tonal characteristics of any instrument. So, what counts the most? We can't tell, but only conclude these two drivers make a great couple crossing over around 2.2 kHz thanks the wave-guided ribbon.
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What I don't like about that design is the bypassing of the highpass capacitor in the network with a resistor. This leads to hot resistors being across the amplifier directly and makes the amp run hotter. It also leaves nothing but resistance ahead of the tweeter, and makes the tweeter play lower with possibly higher HD than necessary.
I've heard other builds that do this, and the tweeter is unfavorably unappreciative of the added stress. The protective rolloff has reduced efficiency, and therefore lets more through.
My 2c,
Wolf
Addendum for clarity: Having a parallel CR is not always detrimental as long as there is an additional highpass capacitor either upwind or downwind from the CR filter. This prevents the direct resistance across the amplifier in the lowest FR range and keeps the resistors and the tweeters happy.
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@wolf_teeth Yes, that was really surprising to see. And as we know, the tweeter is transformer coupled, so it has close to 0 ohms at DC, meaning any DC from the amp will load the series resistors only. The same thing will happen with any low frequency content in the signal. In order to have any kind of function the resistors has to be relatively low resistance as well. This is a very unusual design choice.
hi Piotr z,
Thank you your excellent question. I am currently working on dedicated mids with a narrower surround. The advantage of a narrower surround is that Mms goes down and Sd up which improves sensitivity. It can on the other hand be more challenging to handle the cone breakup. I am running massive computer optimisations in Comsol/Matlab and there is still some work before we can get it tooled and prototyped. The 6.5X took many years to develop and despite we have refined our toolbox then great things take time (have to remind my self of that occasionally)
Meanwhile, we released the current M versions of the 6.5 by reusing the geometry but modifying the motor (shorter coil, reoptimised shorting rings). The rubber composition has been changed to optimise the frequency response. This offers pristine midrange with improved sensitivity.
Diffraction: the surround is so small that it only affects the shorter wavelengths. The biggest issue with a mid is that the cone it self adds quite a bit of diffraction to the lower octaves of the tweeter sitting on top. This is an issue for all mids.
cheers,
Lars
Thank you your excellent question. I am currently working on dedicated mids with a narrower surround. The advantage of a narrower surround is that Mms goes down and Sd up which improves sensitivity. It can on the other hand be more challenging to handle the cone breakup. I am running massive computer optimisations in Comsol/Matlab and there is still some work before we can get it tooled and prototyped. The 6.5X took many years to develop and despite we have refined our toolbox then great things take time (have to remind my self of that occasionally)
Meanwhile, we released the current M versions of the 6.5 by reusing the geometry but modifying the motor (shorter coil, reoptimised shorting rings). The rubber composition has been changed to optimise the frequency response. This offers pristine midrange with improved sensitivity.
Diffraction: the surround is so small that it only affects the shorter wavelengths. The biggest issue with a mid is that the cone it self adds quite a bit of diffraction to the lower octaves of the tweeter sitting on top. This is an issue for all mids.
cheers,
Lars
Thanks for your answer. I know very little about design processes so have no clue how long does it take, but I was kind of guessing that You just went short route and made softer surround with same pattern for mid without doing much more. Keep up the good work You're doing 🙂
My understanding is, that he tries to say that by using a driver way below its limits, you avoid many of the problems, that easily occur when pushing smaller drivers too hard - which often happens in many bookshelf speakers. So he looked at all the smaller drivers and saw that they very quickly run out of juice - distortion rises. Then he picked a big driver that could easily cruise through most SPL levels that we would like for normal music at home, and concluded that by doing so, most known distortion concerns almost went away and became a none issue(this is my interpretation - so please correct me if I missed something).
As an example - I looked at all the data I could find to try and understand the difference between the Dayton Audio HF and HO series for subwoofer duty. What I mostly found, was that the HO has a 4 layer coil and the HF only 2. The point Dayton made, was that the 4 layer coil, was to push the driver into smaller boxes(that's what people want), with the compromise of having higher inductance and therefore more back EMF.
People then say that you simply EQ the bastard and force your wishes through..... but forget how that has limitations too.
What I can walk away with from this - is that we still can't cheat the laws of nature, put surely dance a bit around them.
Maybe what most people are searching for, is how much we can push the limits without breaking them and ending up with something worse.
I also just try to search for answers - maybe clues, by presenting different types of data to different people, to see what might come to the table. I believe that there are many different ways to make good sounding speakers - people just mostly look towards the price, the size and the looks 😀
I have seen a 3" Bliesma dome mentioned here a few times, but I did not remember such a thing existing. is this the driver only available in Russia people are referring to? only in prototype stage or only available to OEMS?
@InspectorGadget The Bliesma 3” domes now have their own thread, plus they are starting to appear on dealer websites, I believe they will start shipping early next year.
Bliesma M74 series 3” dome midrange lineup
Bliesma M74 series 3” dome midrange lineup