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PURIFI finally did a fully purified passive speaker design! The SPK 16 prototype is here - with a PTT tweeter

Interesting it would seem perfect sense to me that a manufacturer who makes both the drivers and electronics should put them together in an active loudspeaker, as mentioned upthread the speakers could be marketed as Lyngdorf or whatever.
Does anyone currently make a Purifi/Purifi speaker, how many Purifi drivers feature in other manufacturer’s loudspeakers?
Keith
Keith, did you mean woofer/tweeter or chassis/amplifier when writing Purifi/Purifi ? (edit: missing letters)
 
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I meant Purifi drivers and Purifi electronics, Hypex / Mola-Mola.
Keith
 
Okay I'm impressed by the drivers and design and all but also a bit skeptical about super low directivity/high dispersion all the way to 20k Hz. Now the in room response will be flat, if not enough absorbing surface is used in the room, instead of downward sloping. According to Harman findings in blind test listeners vote such speakers as too bright and have lower preference vs downward sloping.
Well, aren't all those tests done with tweeters whose dispersion narrows significantly? Therefore to not have excess direct energy too bright, the room response has to slope downward. The result could be different with a tweeter of truly constant dispersion.

(Then again all music is pretty much mixed with narrowing dispersion tweeters so we have a different version of Floyd Toole's "circle of confusion" where if your speaker is much better than some inferior thing the music was mixed on, the music may not sound good. Like Heart from 1985 which sounded great on my best friend's boom box in her flat, but not great on a much better system.)
 
@IamJF @DanielT

Got me thinking about Ole Lund Christensen's cast iron JERN speakers:
Screenshot-2020-01-31-at-12.36.41_result.jpg
rev_2020jun_image-hifi_12ws.jpg


 
But they can build a midrange high frequency coax (300Hz to 20kHz) with a fitting coax waveguide. Such a product might sell very well. I wonder why no driver manufacturer has developed such a package, yet??
Do you mean like the what is it LaVoce or something?

Heck, is there even a non-DIY large waveguide tweeter available? Without 3D printing, without grinding or routering some existing waveguide to fit?

I'm serious-I haven't looked at every product out there but I'd think a 1" dome with waveguide should not be so much more expensive. OK, after a little searching I see various items from even $20 so maybe I should say
- That can go down to like maybe ≤2 kHz crossover to match 10" or 12"
- What I see available the "waveguide" is hardly any bigger diameter than a flat-flange version of the tweeter would be, so I by "large" I mean oh 6-8" (150-200 mm). Like a Buchardt A500 or something. Large for a tweeter, not of course as huge as a mid/treble horn.
- Any waveguides or horns with truly constant dispersion? Yes that would mean a falling high frequency response, to be equalized either in passive or active crossover. It seems most designs are made to be flat on-axis and thus the dispersion narrows.
 
Do you mean like the what is it LaVoce or something?

Heck, is there even a non-DIY large waveguide tweeter available? Without 3D printing, without grinding or routering some existing waveguide to fit?

I'm serious-I haven't looked at every product out there but I'd think a 1" dome with waveguide should not be so much more expensive. OK, after a little searching I see various items from even $20 so maybe I should say
- That can go down to like maybe ≤2 kHz crossover to match 10" or 12"
- What I see available the "waveguide" is hardly any bigger diameter than a flat-flange version of the tweeter would be, so I by "large" I mean oh 6-8" (150-200 mm). Like a Buchardt A500 or something. Large for a tweeter, not of course as huge as a mid/treble horn.
- Any waveguides or horns with truly constant dispersion? Yes that would mean a falling high frequency response, to be equalized either in passive or active crossover. It seems most designs are made to be flat on-axis and thus the dispersion narrows.
A 7" or 8" waveguide for a coax with a 4" midrange and a 1" tweeter would be a very good selling products. The main function of such a waveguide is to assure a fitting di transition from the tweeter to the midrange with low or no unwanted diffraction.

The idea is the same like in the upper line KEF coax or the Genelec one line. A 3" or 4" midrange driver is easy to build and a dome tweeter in a waveguide can provide a very good di. Therefore combining both makes a lot of sense.

The idea to provide a fitting bigger waveguide which also narrows the di of the midrange significantly is also interesting but even if executed well won't sell that much due to its bigger size of 10" and more. You also add the problem of a bigger distance between the coax and bass driver which might become to large to avoid a significant angle dependent phase shift of the midrange and bass...
 

Well, this is more about the final in-room curve, and nothing really stops a constant directivity speaker from achieving the "correct" downward slope, but it's harder than with a speaker that naturally narrows as frequency increases.

I think there's a lot of misinterpretation of that paper. Remember what's being compared there. Not different speakers, but automated EQ on one loudspeaker with notable fidelity issues.

IMO the main actionable knowledge gained from that study for a listener is, neutering room gain is a perceptually bad thing to do. That’s why Audyssey was rated worse than no EQ and and an early version ARC was about the same as no EQ. So don’t neuter your natural room gain!

Also, it’s trivial easy to get a downwards-sloping real room curve with constant directivity - change the direct field! Whether that’s a good approach or not is up for debate. Dr. Geddes endorses an HF rolloff for constant directivity speakers with high DI, if memory serves.
N.B. it would be interesting to see a blind comparison between a good speaker and a bad speaker equalized to the same in-room response as the good speaker. We all think we know the answer, but I don't think the test has actually been done.

Another thing to consider is, due to air absorption and reflections, the predicted in room response may be off in the top octave. For example, here’s the PIR for a JBL 708P, which has basically flat DI to 20kHz.

image.png


And measured average response over a 3-seat sofa from two 708i’s* in a real family room. This room has no dedicated "acoustic treatments." One sidewall is 2/3 glass with thin curtains. The floor is hardwood with an area rug, and the back wall is a built in bookshelf loaded with books and such of varying depth. Room correction (Dirac Live Bass Control) is used up to 500Hz.

708i in room spt avg.png



Harman also displays a bit of inconsistency with how JBl products measure versus Revel products.

Additional blind test results that support my point:


Interestingly (and admittedly not what I expected when I went to look) the DI of M2 and Salon2 are basically identical from 10-20 kHz. I knew both had rising top octave DI (and Salon2 had lower and consistent rather than constant midrange DI generally) but did not realize they were quite so close up top. In that respect, this Purifi tweeter (as well as JBL 705/708 tweeter+horn) are a step ahead IMO.

M2 and Salon2 DI comparo.png


(What a neat tool, @pierre!)

We don't have the tweeter measurements by itself yet, so for now, I would expect most of the effect to be due to that special phase plug/coherer and waveguide. Size and linear excursion are similar to BlieSMa T34A.

My impression was this tweeter was designed as a system with phase plug and waveguide. Which puts Purifi five steps ahead of the rest of the OEM tweeter vendors. Really this type of integration should be the norm, not the exception. The work that people such as Brandon are doing on DIY waveguides for 3D printing is pushing the art forward, but why should that kind of thing have to happen when the vendor themselves are best placed to design and manufacture a appropriate waveguides?
 
A 7" or 8" waveguide for a coax with a 4" midrange and a 1" tweeter would be a very good selling products.
In other words, the midrange cone itself is a kind of shallow, not very constricting waveguide for the 1" tweeter. Which would then mount into waveguide continuing the profile of the midrange cone? Like what Genelec seems to be doing with their coaxials? That is an interesting product idea, since offhand it seems simpler and less expensive than a full-on horn-type coaxial. Maybe we could persuade Parts Express or someone to make such.
 
Which would then mount into waveguide continuing the profile of the midrange cone? Like what Genelec seems to be doing with their coaxials?
Yes the midrange cone and the waveguide both act as a waveguide for the tweeter. Genelec and some other companies built speakers this way.

Maybe we could persuade Parts Express or someone to make such.
It would be nice but I don't have much hope. There aren't even many fitting tweeter waveguide combinations which you can buy and there aren't many good coaxial cone speakers also.

I don't know why there is a lack of waveguide tweeters since a tweeter with a good waveguide like the seas with DXT waveguide is very popular. Some companies might not have a developer who can engineer a good waveguide but the companies which also develop PA horns definitely have such a competence and there are also some guys which can be hired to develop a good waveguide.

A good coaxial speaker is difficult to develop on its own and since there aren't many good ones these mediocre ones also don't sell that well...

If a company manages to develop a coax with waveguide which measures and sound well I guess it would be very popular and used by many smaller speaker companies and diy enthusiasts.
 
The Visaton WG 148 R is a commercial off the shelf wave-guide option for DIYers. It's designed to be used with 25mm tweeters, and a few Visaton models are listed on the company website product page. Other tweeters have been used with it in DIY designs, where mechanical (and acoustic) fit worked out.


And of course, Augerpro (Brandon) has multiple designs that can be 3D printed - a great resource for DIYers who would like to use waveguides in their builds.
 
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are there any updates on how/if this speaker will be made available for purchase? Will it be in kit/plan form like the previous Purifi speaker designs or perhaps a finished product?
The update is about the color of that PROTOTYPE demonstrator/reference design and the screw sets, which had been a poi for discussion already.
As it is a PROTOTYPE demonstrator/reference design ready for the Munich High End show it doesn't look likely this will become a mass market product by PuRiFi.
The parts, however, may be made availiable to the DIY community.
And then there is Troels Gravensen (http://www.troelsgravesen.dk/), who already did a couple of PuRiFi builds.
Lyngdorf may have an interest in the design, too. But that's all speculation ...
edit: Thanks @boXem
 
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The update is about the color of that PROTOTYPE and the screw sets, which had been a poi for discussion already.
As it is a PROTOTYPE ready for the Munich High End show it doesn't look likely this will become a mass market product by PuRiFi.
The parts, however, may be made availiable to the DIY community.
And then there is Troels Gravensen (http://www.troelsgravesen.dk/), who already did a couple of PuRiFi builds.
Lyngdorf may have an interest in the design, too. But that's all speculation ...
I perfectly get your intention, but I fear that calling this a prototype causes more confusion than clarification: in the industry, prototyping is part of the steps preceding the production. If a company has no intent to produce a thing, they call it a demonstrator or a reference design. Indeed Purifi call the SPK16 a reference design.
 
Not sure about EU or elsewhere, but previous Purifi reference designs were not sold in US.

The SPK5s I have came from UK.
 
If anyone happens to visit the Munich High End Show (Hall 1, A8 - Munich, May 18-21, 2023), I hope they will report back here - Maybe even make a new Munich High End Show Thread :)
 
If anyone happens to visit the Munich High End Show (Hall 1, A8 - Munich, May 18-21, 2023), I hope they will report back here - Maybe even make a new Munich High End Show Thread :)
Already in progress. See Audio Shows forum section.:cool:
 
The Belgian-Danish source of audio greatness in Roskilde / Denmark have achieved to provide something to the community that many DIY speaker enthusiasts were hoping for.:
A PTT tweeter !!!

They've put that little thingy called PTT 33 tweeter - which Lars Risbo describes as:
"33mm alu hard dome with +-1 mm linear stroke, low distortion. Dome optimised for wide dispersion. Non resonant nautilus style rear chamber. demo speaker uses tweeter in 147mm waveguide optimised for constant directivity in the box. a phase plug /coherer near throat of the wave guide widens the dispersion. +-70deg beam width to 20kHz"
- into a reference design stand mount speaker named SPK 16.

The tweeter radiation pattern sows an exeptional horizontal dispersion (inbox, 1m), an achievement the PURIFI engenii seem to be proud of ;-)

View attachment 284370

Lars Risbo wrote me that it is crossing over around 2kz and the full crossover network was developed in-house. The F3 is 32Hz and its response is working flat into 37Hz says the press release, which is attached to the posting.

View attachment 284371

The SPK 16 prototype:

The standmount speaker (I'll bet it will be in PURIFI red at the Munich show!) is a 22 liter reference design, with the new PTT33 (mm) aluminum cone tweeter and the 4-Ohm PTT6.5X04-NAA woofer, feat. 2x 6.5" Passive Radiators - side mounted.

View attachment 284373

He has written a white paper about the prototype which will be published in time for the MHE. As I was enjoying reading it, I ask about pre-releasing the chapter 1 and 2 about the goals to reach and challenges they tried to master, which he gently agreed to.

Here are page 1 and 2 of the WP by Lars Risbo.

View attachment 284375

View attachment 284376

The other four chapters will be released in time for the MHE and as far as I can judge the company, they will be happy to discuss their ideas with you !

Purifi will be a the Munich High End show (Hall 1, A8 - Munich, May 18-21, 2023) and they have an open show room at Saturday afternoon in a more privative environment.
(see attached press release for more info)

The company has announced the following premieres next week.:

View attachment 284379
Final words come from Bruno:
“DON'T MISS THE OPPORTUNITY TO HEAR THE SPK16 DEMO WITH THE NEW AMPLIFIER GENERATION – IT’S QUITE A TREAT!

I was at their Open House in Munich. Words cannot describe how spectacular the sound was.
 

Is phase plug /coherer really necessary? ・・・・
 
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