Exploring Purifi Woofer Speaker Builds

mainframe99

Member
2019-01-21 12:42 am
Update 17/03/22:

Time for a bit of consolidation due to this thread getting some hits, and purifi has now released quite a few scrunchy woofers

Links to known projects & commercial speakers using the Purifi drivers (please PM me if I need to add any)

Of course - www.purifi-audio.com , and the team behind the drivers here

Full DIY:

@lrisbo Proof of concept Purifi SPK4 (superseded) - Passive stand-mount

IMG_0194-2.jpg


@lrisbo Proof of concept Purifi SPK5 - Passive stand-mount - I believe these were at some point being made and sold commercially but have since been discontinued - there may be some floating around second hand market see here Celuaris SPK5 review ASR

purifi_spk5.jpg


@xrk971 PTT6.5/RS28F Waveguide Harsch XO - Passive stand-mount later evolved into a nice Stand mount and Floor standing Transmission Line

ptt6.5 rs28fwg.jpeg


@Joe Rasmussen Somewhat Legendary 'Elsinore' - I hope I'm not jumping the gun here but Elsinore might be getting a new set of Purifi shoes - starting from post #4271. Floor-stander

(Shown here the original Elsinore)

EL-6_SoundRoom.jpg


Rick Sykora and team's Directiva - Active stand-mount with excellent (objective) reviews, requires external amplification for each driver and an external DSP crossover.

ASR Directiva Review Open Source Purifi Speaker.jpg




@xrk971 's Raal 70-20xr and PTT6.5 - this one the tweeter is not readily available to DIYers but there may be ways to get it if you're crafty.

(sorry X, couldnt find a finished pic, and I'm out of attachments for this post)




.....and many more concepts within this thread, start reading. Most not fully documented or taken to finished stage though I suspect a few people are still perfecting their builds before showing them off. Remember you can drop people a friendly private message asking about how their progress is going.





DIY-Kits/Semi Commercial:



Troels Gravesen Purifi 6661 - Semi-passive/Active plate amplified floor-stander

p-6661-1.jpg


Troels Gravesen Purifi 6R - Passive bookshelf

purifi-1.jpg


hificompass Puri Bliss BeWg - Passive bookshelf - I believe the plans are/were for sale

PuriBliss_BeWg_4.jpg


Joseph Crowe's 1198 - I believe you have to get in touch via the webpage - floor-stand transmission line

110749662_1199955657029489_1368727901282454175_n.jpg







Full Commercial:

March Audio Sointuva - arguably where "the bar has been set" for the Purifi 6.5 in a bookshelf chassis.

Sointuva17.jpg


Jones Scanlon Baby Reds - self powered studio mixing monitors.

Jones-Scanlon-Baby-Reds-studio-monitors-1920w-2.jpg


The Late Rick Craig's Selah Audio Purezza - A nice stand mount ribbon tweeter design, was available commercially but afaik discontinued, check SH market

116706749_971365439969612_5078393334836774399_n.jpg


Jachim Gerhard Surveyor's - stand-mounts , I believe there is/was a floor-stander made too

Rose_03-10-2020_0025-scaled.jpg


Dennis Murphy & Jim Salk's BePure2 - Floor stander - The legends behind the philharmonic BMR and BMR tower

a.jpg


and um, what ever this might be! https://www.audiocircle.com/index.php?topic=175599.0 - probably just a concept, I didn't read the thread. Likely Unobtanium tweeters and probably bottomless pockets required, if it is sold commercially.

Correction - the above was a concept which later evolved to the BePure2 - see this thread at AVSForums Post #10,174
https://www.avsforum.com/threads/th...rs-and-discussion-thread.939744/post-61186397


Links to driver reviews:

https://www.erinsaudiocorner.com/driveunits/purifi_4/
https://www.erinsaudiocorner.com/driveunits/purifi_ptt65w04/

https://audioxpress.com/article/tes...udio-6-5-midbass-transducer-from-purifi-audio

https://hificompass.com/en/reviews/purifi-audio-ptt65w04-01a-midwoofer
https://hificompass.com/en/reviews/purifi-audio-ptt40w04-01a-midwoofer
https://hificompass.com/en/reviews/purifi-ptt65w08-01b-ptt65x08-nfa-01
https://hificompass.com/en/reviews/purifi-ptt65m08-nfa-01a-65-true-midrange

http://www.troelsgravesen.dk/Purifi.htm


Original Post:

With the group buys well underway the idea was bought up that a design thread be started to discuss build options.

Mine have arrived but I have no build materials and will not be able to get any until we come out of quarantine in (hopefully) three weeks time. I planned to start with a hybrid of purifi's SPK4/5 builds using the same AMT tweeter but maybe using a slot port with the 2.5khz crossover. That and I haven't done any AMT builds so it seemed like a good place to start.

I read of a guy in Aus planning on doing a line of passive and active speakers with the woofer so be interesting if he could chime in here.

So with no materials for the next at least 3 weeks, what better time to discuss build options! Fire away

20200402_103530.jpg
20200402_103700.jpg
20200402_103908.jpg
 

Attachments

  • IMG_0194-2.jpg
    IMG_0194-2.jpg
    98.6 KB · Views: 27
  • purifi_spk5.jpg
    purifi_spk5.jpg
    229.2 KB · Views: 39
  • AirBlade-candy.jpg
    AirBlade-candy.jpg
    49.9 KB · Views: 43
Last edited:
  • Like
Reactions: 1 user
Hey fella. I'm in Kapiti. Whereabouts in NZ are you? I'm annoyed I missed out on a group buy. I would have definitely been keen.

I've not done any ribbon builds, but I don't know if I'd pick the AMT for this woofer.

The AMT has a lot of 3rd order HD:
Mundorf AMT21CM2.1-C | HiFiCompass

And will strain / be audible as the woofer can take it. Compare similar voltage levels and watch the AMT HD climb.

Also beaming of the Purifi at a 3.2KHz XO point of the SPK5 design will give some lumpy off axis behaviour.

The AMTs are very expensive for what they offer. In a 3 way, allowing a higher XO point from a dome mid would be a goer. But I would not combine with the Purifi in a pure 2 way.

Shipping to NZ would be a killer too (unless you already have the AMTs). Instead I'd recommend the following tweeter. You can get these from theloudspeakerkit.com and much cheaper. Check out the distortion profile. Has similar offaxis performance to the AMT too:
SB Acoustics SB26ADC-C000-4 | HiFiCompass

You could cross the above LR4 at 2Khz and address the beaming issue AND get lower distortion than the AMT.

The purifi provides a maximally flat vented alignment in a 15.5L box tuned to 35.1Hz (assuming average losses) with an F3= 38Hz. This is pretty good. If you can go active, this woofer could really shine in a 3 way with a 100Hz XO to a side mounted 12. Candidates that dig deep if you like sealed bass are the 12" SB34NRX75-6 (not the L version) or Dayton 15" RSS390HF. Both give a sealed box Qtc=0.71 in 122 litres with F3 ~ 32-33Hz.

Although an extra 6 Hz F3 over a vented Purifi might not sound like much, you really leverage the Purifi's midrange strengths and offload bass duty.
 
Last edited:

mainframe99

Member
2019-01-21 12:42 am
Hey fella. I'm in Kapiti. Whereabouts in NZ are you? I'm annoyed I missed out on a group buy. I would ... ...and offload bass duty.

Hi Dave, I’m in the big smoke mate. Hope you doing okay down there. We have people punching supermarket managers in the face :eek:

Agree on the 3.2khz crossover being too high. In the other thread I explained the spk5 build seems to be more about showing off the woofers ability vs. smooth off axis response.

For now I already have the AMTs as I haven’t used them or heard them so I am curious. Ive always used domes. I’ve got a mini dsp shd studio which also only allows me to do a 2-way so I will stick with a 2 way for now, probably with the spk4 cabinet or similar and the 2.5 crossover.

I have a pair of wavecor tw030s on the way to get the crossover lower. But I wish I’d seen that tweet you suggested first! Very nice tweet. I already have a big 4 way system with subwoofers that Is my reference and now I’m all about making something small with big output.
 
Hi Dave, I’m in the big smoke mate. Hope you doing okay down there. We have people punching supermarket managers in the face :eek:

Agree on the 3.2khz crossover being too high. In the other thread I explained the spk5 build seems to be more about showing off the woofers ability vs. smooth off axis response.

For now I already have the AMTs as I haven’t used them or heard them so I am curious. Ive always used domes. I’ve got a mini dsp shd studio which also only allows me to do a 2-way so I will stick with a 2 way for now, probably with the spk4 cabinet or similar and the 2.5 crossover.

I have a pair of wavecor tw030s on the way to get the crossover lower. But I wish I’d seen that tweet you suggested first! Very nice tweet. I already have a big 4 way system with subwoofers that Is my reference and now I’m all about making something small with big output.

Yeah it's crazy times all right. Plenty of muppets out there doing stupid things.

I'm sure those AMTs will sound sweet and if these 2 ways are predominantly for on-axis / sweet spot listening, they will sound wonderful. At least with the wavecors you have options and the miniDSP makes it super easy to switch.

Are you going vented with the Purifi?

Also - what drivers have you got in your 4 way out of interest?
 

mainframe99

Member
2019-01-21 12:42 am
Holy.

Whipped up some quick test cabinets as attached. The bass these things put out is quite simply jaw dropping. Best two way (bookshelf) I have heard. No question. The song backseat freestyle by Kendrick Lamar will bring most bookshelf speakers to their knees. Not here. I know people don’t like the word game changer around here but this is a game changer IMO. It’s early days, and I am using digital crossovers so a lot of tweaking to do, but so far it is really really good. I can’t stop shaking my head in disbelief of how loud, clean and clear these woofers are.

(Yes those ports are green, you use what you can gets in a lockdown and this time it’s communications cable duct from the top of my work Ute)
20200425_114957.jpg 20200425_115206.jpg
 
Last edited:
Holy.

Whipped up some quick test cabinets as attached. The bass these things put out is quite simply jaw dropping. Best two way (bookshelf) I have heard. No question. The song backseat freestyle by Kendrick Lamar will bring most bookshelf speakers to their knees. Not here. I know people don’t like the word game changer around here but this is a game changer IMO. It’s early days, and I am using digital crossovers so a lot of tweaking to do, but so far it is really really good. I can’t stop shaking my head in disbelief of how loud, clean and clear these woofers are.

(Yes those ports are green, you use what you can gets in a lockdown and this time it’s communications cable duct from the top of my work Ute)
View attachment 837877
View attachment 837878

Attachments no workie...
 
I don't think I'd even use this for multiples in a dsp-boosted low-end (as originally designed for) regardless of cost.


I could see multiples working for some applications. Using 4 of these per side has a much higher WAF than a single 15" (especially if 2 are hidden from view on the rear panel) and offers much better midrange performance. Also allows for some smart configurations. Think Kii Three on steroids ;)
 

Zvu

Member
2009-01-15 6:52 pm
Belgrade
You need at least seven 6.5" woofers per cabinet to match cone surface of one 15" woofer.

Advanced version of Kii Three is the only logical implementation of Purifi woofer that i can think of. If you have a room large enough that you need to push Purifi to its limits, then you have enough room to accommodate larger loudspeakers that you don't have to push that hard to get to that same spl. If you have small room but still need that high SPL, you are deaf and you will not hear slightly higher distortion figure from drastically cheaper woofers (say SB17NBAC).

WAF is overrated factor. I don't choose what cell phone or makeup will my wife use, she don't decide what size of speakers i will make. I had 12" woofers + JBL PTWG followed with 15" woofer with 18"wg loudspeakers in my room when she met me so i guess she knew that i'm not into fishing or chess.
 
Last edited:
You need at least seven 6.5" woofers per cabinet to match cone surface of one 15" woofer.


Surface area isn't everything. Remember that the Purifi has a large linear Xmax of +/- 10 mm and an Sd of 133cm2.


The first 15" data I pulled up was for the Faital 15PR400 which has an Sd of 805 cm2 and an Xmax of +/- 5.8mm (FaitalPRO 15PR400 - 15" Subwoofer)


Displacement of that 15" at Xmax is 467cm3 whereas linear displacement of 4 x Purifi is higher at 532cm3.


Working backwards from that, you would need a 15" with about +/-6.7mm linear Xmax to match the linear displacement of 4 Purifis.
 
Last edited: