Article: Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review

[mitchco]

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[The Computer Audiophile]

Thanks for the excellent review Mitch!

[DuckToller]

Wow!
Thank you, Mitch, for this excellent review.
Well meseaured and perfectly explained !!!
Lot of respects as well to the PuRiFiens for their outstanding work.
Happy XMAS to all of you!!
Tom

[all300b]

Wow - such a great idea to focus on perfecting the 6.5" woofer.  The two-way rises again.  Any thoughts on:

-  What about trying a sealed box configuration?

-  Could this go with a first order crossover to something a little softer - say like an Esotar? The freq response curve for the pure-fi looks remarkably free of of ringing - it might not squeal when asked to play some higher notes.

 

Bryan

 

[Matias]

Their website also sells a passive radiator for this driver which would be very interesting for a DIY project. Specially something bigger like a d'Appolito PR - woofer - tweeter - woofer - PR floorstander.

 

https://purifi-audio.com/vare-kategori/transducers/

[firedog]

Anyone know if they are going to be selling full kits for DIY? In other words everything you need, just put it together?

[blue2]

12 hours ago, Matias said:

Their website also sells a passive radiator for this driver which would be very interesting for a DIY project. Specially something bigger like a d'Appolito PR - woofer - tweeter - woofer - PR floorstander.

 

https://purifi-audio.com/vare-kategori/transducers/

Very interesting article Mitch. Their web site doesn't seem to have much in the way of DIY products just transducers and amp modules. They have the PTT6.5W04-01A (as in your picture) at DKK 2329 (equivalent to $345/£267 + taxes + shipping). Do you have any sales info about the kits you actually tested i.e. price and availability?

d'Appolito DIY kit or just a floorstanding version would be very nice

[ShawnC]

Great review Mitch, I hope Magnepan uses these in there semi secret testing of the prototype Mini 30.7 woofer towers.  Finally giving maggies the punch and dynamics I've always wanted from them.

[Abtr]

Great review. Do you think the SPK4 demo speakers will sound better than KEF-LS50's with a sub and a decent active crossover (e.g. at 100Hz and 24dB/oct) to reduce IMD?

[monteverdi]

Great review. There was very little development in driver design for decades except membrane materials. There have recently a few smaller companies developing iron-less motor systems to reduce loudspeaker distortion (THD & IMD) which is for most loudspeakers magnitude higher than any other component.

Purifi has on their website some very interesting technical comments https://purifi-audio.com/tech/

They also came out with an even small 4" driver but I wonder why not something larger like 8". Larger drivers require less cone travel for the same displacement (their tech notes explain that more mass only decreases sensitivity) so using their technology could also improve drivers designed for lower cross-over points

[mitchco]

On 12/23/2019 at 11:53 AM, all300b said:

Wow - such a great idea to focus on perfecting the 6.5" woofer.  The two-way rises again.  Any thoughts on:

-  What about trying a sealed box configuration?

-  Could this go with a first order crossover to something a little softer - say like an Esotar? The freq response curve for the pure-fi looks remarkably free of of ringing - it might not squeal when asked to play some higher notes.

 

Bryan

 

 

Merry Xmas Bryan. Do you have a box modelling program like Leap or BassBox Pro? Here is a list here if you don't. You would have to enter in the Thiele/Small parameters of the driver into these tools to see if it would work in a sealed box config. Also, you can use Leap to design the crossover to something like an Esotar to see if that would work.

 

Kind regards,

Mitch

[mitchco]

13 hours ago, firedog said:

Anyone know if they are going to be selling full kits for DIY? In other words everything you need, just put it together?

 

Merry Xmas @firedog As far as I know, Purifi's plan is to OEM drivers, electronics, PSU's and DSP. There wasn't any mention of selling full kits. The SPK4 and SPK5 plans do include everything to build, but like you say not a kit delivered as a "flat pack."

[mitchco]

11 hours ago, blue2 said:

Very interesting article Mitch. Their web site doesn't seem to have much in the way of DIY products just transducers and amp modules. They have the PTT6.5W04-01A (as in your picture) at DKK 2329 (equivalent to $345/£267 + taxes + shipping). Do you have any sales info about the kits you actually tested i.e. price and availability?

d'Appolito DIY kit or just a floorstanding version would be very nice

 

Merry Xmas @blue2 What I received is a demo kit for the evaluation of the technology. As mentioned above to firedog, I don't think there is "finished kits" for sale. But I could be wrong and worth a note to Purifi to confirm.

 

Kind regards,

Mitch

[mitchco]

5 hours ago, Abtr said:

Great review. Do you think the SPK4 demo speakers will sound better than KEF-LS50's with a sub and a decent active crossover (e.g. at 100Hz and 24dB/oct) to reduce IMD?

 

Merry Xmas @Abtr As an owner of the KEF LS50's and crossed over to dual Rythmik L12 subs with a digital active XO at 100 Hz, they sound really good! Certainly does offload the IMD. As to which one sounds better is a matter of opinion, and how loud one listens, but it is hard ignore the vanishing low distortion of the PTT6.5 woofer...

 

Looking at the measured distortion spec of the LS50 at Soundstage! it comes on pretty quick at 200 Hz. The Rythmik L12's are a good pairing, but maybe dual Rythmik F8's positioned close to the LS50's would offer better even performance as they can be crossed higher e.g. 200 Hz.

 

Kind regards,

Mitch

[blue2]

11 hours ago, mitchco said:

 

Merry Xmas @blue2 What I received is a demo kit for the evaluation of the technology. As mentioned above to firedog, I don't think there is "finished kits" for sale. But I could be wrong and worth a note to Purifi to confirm.

 

Kind regards,

Mitch

Thanks. Merry Christmas!

[bobfa]

Makes me wonder what Bruno and team will do at Kii?  

[firedog]

On 12/24/2019 at 8:26 AM, firedog said:

Anyone know if they are going to be selling full kits for DIY? In other words everything you need, just put it together?

Wrote Purifi and this is the answer I received:

Quote

We don’t have any current plans to market complete kits. We aim to release our own PSU in late 2020, but no point in waiting for that as the schedule is not 100% locked in yet. The OEMs we deal with today is in the process of releasing complete products based on 1ET400A - but I'm not sure if anyone is selling it as "kits" (actually I don’t think so).

 

[Lord Victor]

On 12/24/2019 at 10:12 PM, mitchco said:

 

Merry Xmas @Abtr As an owner of the KEF LS50's and crossed over to dual Rythmik L12 subs with a digital active XO at 100 Hz, they sound really good! Certainly does offload the IMD. As to which one sounds better is a matter of opinion, and how loud one listens, but it is hard ignore the vanishing low distortion of the PTT6.5 woofer...

 

Looking at the measured distortion spec of the LS50 at Soundstage! it comes on pretty quick at 200 Hz. The Rythmik L12's are a good pairing, but maybe dual Rythmik F8's positioned close to the LS50's would offer better even performance as they can be crossed higher e.g. 200 Hz.

 

Kind regards,

Mitch

Very interesting to hear, I personally have a pair of Monitor Audio Platinum 100 and was considering going for a Raidho and Nad M22.2 amp when I saw this, now I’m wondering if this is a better route... for at least the amp or even both...

but if the LS50 can keep up with the Purifi, maybe I should stick with the original plan on the speakers...?

This hobby truly is an enigma, when you can’t ‘try before you buy’!

 

Cheers

[jeffhenning]

Hey, Mitch.

 

This report was especially pertinent to me since:

• I use Rythmik subs (L12's... love them and want to get another pair)

• I own LS50's (love them, too)

• I'm very interested in both of the reviewed products for future upgrades (custom active main speakers and amps)

• I use DSP

 

So, a few questions:

• What are you using for correctional DSP?

• Are you using DSP for the crossover of the subs to the mains?

 

At present, my system has LS50's fronts and center. The fronts are driven by a Parasound a-23 and the center is driven by an inexpensive Emotiva class D amp. I cross them over at 170Hz so they can stay in their happy place. Those little LS50 drivers are not very beefy.

 

The Parasound will be replaced by a Benchmark AHB-2 and the Emotiva by a Nord Purifi mono.

 

I ordered a single KEF LS50 for the center, but was given a pair!? My plans to round out the 7 surround channels with Magnepan  LSR dipoles has been thrown into disarray. Not a bad thing.

 

As it goes now, the surrounds will be LS50's with LSR's as rears. If they send me another pair of LS50's instead of a single one, I'll do LS50's all around.

 

The surrounds and rears will be driven by Emotiva class D's. Given the limited nature of surround channels, I'm not spending a ton on amps for them. 

 

And eventually, I'll do the Atmos thing. That will be easy for me since my listening room has a drop ceiling.

 

My room is a LEDE setup since it's got a weird shape. The sound absorbing blankets & heavy curtains that cover most of the front and side walls offer about 20dB in attenuation above 400Hz. The live, rear half of the has a few closets with double doors that I leave a bit open to randomize reflections. In front of them are 3 Boltz media racks that offer a good bit of diffusion as well.

 

Because of the shape, the thick carpeted/padded concrete floor and the basement drop ceiling with insulation in the rafters, the low end is incredibly even without room correction.

 

In this set up, I find a flat in-room response to be perfect. It's the best sounding room I've ever heard.

 

All the best in the new year.

[mitchco]

On 12/29/2019 at 3:08 PM, Lord Victor said:

Very interesting to hear, I personally have a pair of Monitor Audio Platinum 100 and was considering going for a Raidho and Nad M22.2 amp when I saw this, now I’m wondering if this is a better route... for at least the amp or even both...

but if the LS50 can keep up with the Purifi, maybe I should stick with the original plan on the speakers...?

This hobby truly is an enigma, when you can’t ‘try before you buy’!

 

Cheers

 

Agreed. When it comes to speakers, there are two main factors based on the current research out there, mainly by Floyd Toole/Sean Olive and team. One is that the speaker should have smooth on and off axis response (which the LS50's have) and the other his how low you want to go. Of course there are other attributes, but these are the main two that make the difference in most systems. According to Toole's research, bass accounts for about 30% of the factor weighting in subjective evaluations of sound quality. Personally, if I have enough room, I can't live without subs 🙂

 

If you can wait, I would be inclined to see where those Purifi 6.5" woofers end up in a kit and/or commercial product as their woofer is next gen from anything else I have heard. And if it that does not go low/loud enough for you after listening, then maybe subs are in order...

 

Good luck!

[mitchco]

5 hours ago, jeffhenning said:

So, a few questions:

• What are you using for correctional DSP?

• Are you using DSP for the crossover of the subs to the mains?

 

Hi Jeff, I use both Acourate and Audiolense DSP. In my current setup, I am using Audiolense to crossover to my dual subs. Audiolense uses linear phase digital crossovers so that they sum perfectly in both the frequency and time domains. Here is a walkthrough of how I did it: https://audiophilestyle.com/ca/ca-academy/ integrating-subwoofers-with-stereo-mains-using-audiolense-r712/  Audiolense also time aligns the subs to mains.

 

Both Acourate and Audiolense are capable for multichannel setups as well. I would have to find it, but I remember one person who triamped their mains, had multiple subs and multichannel setup using Audiolense. Used something like 16 channels...

 

 

I have worked in LEDE studio control rooms before and am I fan 🙂

 

Happy New Year to you as well!

[jeffhenning]

Hi, Mitch.

 

Unfortunately, neither of those DSP solutions will work for me since I use a Mac. Also, at present, integrating a system like yours into a home theater seems to be a lot of work and offers a lot of redundancy.

 

I really wish that someone would come up with an audio protocol for sending digital audio out of a theater pre to a speaker processor for high end DSP and crossover functions. I realize that on good stuff the D/A/D conversion is inaudible, but it's just unnecessary.

 

Given the rising popularity of wireless DSP speakers, that can't happen fast enough. Since I see a TV in your listening room, should I assume that you aren't using surrounds?

 

The design I have in my head to supplant the LS50's is a 2 way design with Raven Design Studio LineSource ribbons (which go down to 800Hz) and then mids to go down to the existing Rythmik subs.

 

While I was seriously considering BG Neo-10 planar magnetics, Parts Express just doubled their price (ugh!). Had Purifi not com out with this driver, there was no option, but to take it. The Neo-10 is a great driver, but it runs out of steam at 150Hz and it's not happy being pushed hard there. The only option is to load a bunch of them onto the front baffle so that mid-bass output is unrestricted (8 or 9 depending on the preferred dispersion pattern). That is not cheap and the front baffle will be huge.

 

The Purifi 6.5" and its soon to be released 4" brother seem to be great replacements for this design. It would also allow me to have a much slimmer front baffle. Think D' Appolito line source (mid-bass line source with a line source ribbon in the middle). It seems both drivers can very comfortably make it to 80Hz as a dipole.

 

Then do that Dutch&Dutch trick where the mid-basses are dipoles, but have a small, treated cab behind the baffle to catch some of the rear wave. 

 

My only reservation with Purifi's drivers is their moving mass. It's double that of comparable drivers. I'll have to ask them about that.

 

Take care.

[mitchco]

Hi Jeff,

 

As a side note, Acourate and Audiolense can run on a Mac by using Bootcamp/Windows or by using Parallels+Asio4All (Parallels does not support Asio drivers directly). Some folks borrow a PC laptop to take the measurements, design and generate the FIR correction filters, but then host them on a Mac with a convolution engine.

Yes, I am an old school stereo kind of guy, so no surround, except on headphones.

 

Wrt Purifi's drivers and moving mass. You may want to check out Purifi's tech page: https://purifi-audio.com/tech/ and the Dec 10th post on, "A fast driver needs a light cone. Or does it?" Also, Lars had this to say when asked about this, "Essentially, mass mostly affects sensitivity and has nothing to do with speed - a tough myth to bust. The combination of very long stroke and a 4 layer coil adds 10-12g of mass compared to a shorter stroke 2 layer coil. The long stroke surround adds approx 1g more than a conventional shorter stroke half roll and the strengthening of the cone adds perhaps a gram as well. The 4 layer coil increases the motor strength making the driver suitable to work even in small sealed boxes in combination with the strong cone and robust surround (to handle the high back pressure). All of this has not compromised the excellent midrange performance. Or in other words, all of these design choices have resulted in this combination of sub, woofer and mid with ultra low distortion."

 

Hope that helps.

[jeffhenning]

Thanks, Mitch. That does help a lot.

 

I figured that wasn't going to be an issue with their optimized magnet structure and assumed that the mass was mostly voice coil, but I don't complete speaker designs based on assumptions. My only thought is that, with less than ideal designs, mass will not only effect the sensitivity, but does cause a lag in the driver's settling time. That's why I always like to see a waterfall display as well (if possible).

 

That this driver can cleanly integrate with a Mundorf ATM (and they make the best) says a lot.

 

Also, I do know about Bootcamp, Parallels and VMware. My problem is with the inelegance of jamming a computer into the middle of my audio system. Before you go any further, yes, everything today is a computer (even egg trays!?).

 

Unless you want to pay dearly for the best of Trinnov or Datasat, an all-in-one or fully integrated multi-box solution doesn't exist.

 

The cheapest, great sounding option at present that doesn't have a computer wasted as a DSP processor is using a loudspeaker processor like Xilica's XD-4080. Legacy Audio still uses that processor's brother, the XP-4080 (has no digital i/o or FIR filters), for some of their better speakers. The XD-4080 allows you to upgrade to even better A/D and D/A processors via AES/EBU if you want to.

 

Again, this winds up being expensive and inelegant (too many boxes).

 

The best I can hope for is that Emotiva follows Datasat's lead and offers that one box solution with DSP (Dirac) and great crossovers for multi-amping in it's next flagship pre-pro. And of course, have it cost about $5 or 6K. That would leave me with nothing to complain about.

 

Take care.

[Normal Man]

Mitch Barnett’s review here on Audiophile Style along with the technical measurements confirmed by HiFiCompass has led me to become an early adopter of the Purifi PTT6.5W04-01A woofer. If you are also interested in being among the first to own this breakthrough speaker technology join us for a North American group buy I am organizing on diyaudio.com for Purifi’s PTT6.5W04-01A woofer, and optionally the matching PTT6.5PR-01A Passive Radiator. Owing to Purifi’s policy requiring orders go to a single address this gets complex, thus the long post with details and minutia here:

 

https://www.diyaudio.com/forums/group-buys/348234-purifi-ptt6-5w04-01a-woofer-buy.html

 

There I also post links and description of Purifi and their PTT6.5W04-01A woofer. Rather than repeat that allow me to describe why I have shoe horned in with my other projects to explore the PTT6.5W04-01A (for discussion let’s shorten that to PTT6.5W).

 

First is the distinguished individuals who have formed Purifi with deep chops on both the science + technology and business side of Hi-Fi. Second a believable explanation of how going back to first principles the team reduced distortion by tens of dBs and allowed low distortion operation at extreme excursions. Third independent measurement and listening tests report Pirifi has achieved the stated goals. Fourth it uses a paper + fibers cone, I like paper cones and the simple crossovers they often allow. Fifth is a thermal and mechanical design that reliably withstands exploring the limits of the driver. Purifi publicly states one can keep pouring on the power until the driver bangs against its stops (at somewhere beyond +-14 mm excursions!) and the driver is fine, just turn it down a bit. In my view this capability is especially valuable given the T/S parameters are set for vented enclosures so below ~30Hz the driver will be unloaded from the enclosure’s air mass. Of course all vented designs share that trait, it’s just that low distortion and air moving promises of the PTT6.5W will invite operation at high levels.

 

A new paragraph for my sixth reason as I feel most strongly about it. I have a passion for enabling those of us in the middle class to own Hi-Fi approaching the performance of statement level rigs. Carefully selected solutions along with some sweat equity and for a few thousands we have sound approaching the hundred thousand dollar rigs. The PTT6.5W has that potential all over it so I am in. Given it is designed for use in ½ cubic foot (15 liter) enclosures one can get it up and running with a simple flat pack box from Parts Express and the Purifi application note. From there you are only limited by your imagination. I intend to share as an open source project PTT6.5W designs using different tweeters and enclosure options.

 

If I have peaked your curiosity to hear these as an early adopter click the link and check it out.