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    Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review

    I enjoy reviewing innovative loudspeakers like the Dutch and Dutch 8c and the Kii THREE. I also spend time on diyAudio’s loudspeaker forums looking at what to build next or modify what I have, essentially looking for the “next big thing.” I noticed Purifi’s woofer getting good reviews on diyAudio and ASR. On Audiophile Style, @DuckToller wrote an article on meeting the folks from Purifi in Munich with @The Computer Audiophile. Reading those really peaked my interest. 

     

    HiFiCompass’ review of the PTT6.5 shows the woofer measuring considerably better than its competitors, especially in reduced distortion, both THD and IMD. This puts Purifi’s PTT6.5 woofer into a class on to itself. Now I really wanted to hear this woofer! Before I could track down a pair, I received a note from DuckToller asking if I would be interested in evaluating the woofers in kit form. A short while later I received a demo kit and a stereo IET400A amplifier.

     

    I must say upfront that this technology represents a major audible improvement in mid/bass clarity and low frequency extension. Meaning, I have not heard a 6.5” woofer go this low or sound this clean, at concert level volumes. To my ears, the Purifi PTT6.5 woofer is the “next big thing” in transducer technology. Coupled with Purifi’s 1ET400A amplifier, this is the lowest distortion sound I have heard from any amp/speaker combo of this size in my listening room.

     

     

     

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    Purifi SPK4 Loudspeaker Demo Kit and 1ET400A stereo amplifier (top view).

     

     

     

     

    Technology Discussion

     

     Much has been written about the technical aspects of Purifi’s PTT6.5 woofer technology including HiFiCompass’s extensive objective measurements linked above and Amir’s objective measurements of the 1ET400A amplifier.

     

    My review will be a combination of a few objective loudspeaker measurements in my room and subjective listening impressions. My review is aimed at the consumer and DIY audio enthusiasts wondering what these technology advancements are and how they translate into a superior listening experience.

     

    A 6.5” woofer is not big and has real world limitations on how low of a frequency the driver can realistically reproduce, yet still sound clear in the bass and midrange as volume increases.

     

    While our ears are relatively insensitive to low frequency harmonic distortion, they are more sensitive to intermodulation distortion (IMD). How can a small driver output significant low frequency energy yet still sound clean in the lower mids and midrange? This is the crux of the technical dilemma that no loudspeaker designer/manufacturer has been able to crack… until now.

     

    I thought I would ask Purifi’s Lars Risbo, one of the brains behind the PTT6.5 woofer, to describe their design approach on how they were able to obtain such low measured intermodulation distortion numbers:

     

     

    Our PTT6.5 woofer is the result of about 4 years of research. It has been a fruitful teamwork between Bruno, Carsten, Morten, and myself. This has resulted in a design that is vastly different from conventional drivers. In short, we have been on a crusade against all sources of intermodulation distortion. Psychoacoustics has correctly shown that our ears are not that sensitive to pure harmonic distortion – especially in the bass. However, our ears are way less forgiving when it comes to IMD when listening to complex music program material. Since it is impossible to only generate harmonic distortion without IMD, it has been necessary to reduce all nonlinear mechanisms in a speaker.

     

    The most known source of IMD is the position dependent force factor Bl(x) which we have made ruler flat over +-6mm excursion (+-10mm at -10% Bl). Less known is the current and frequency dependent modulation of the force factor (aka force factor modulation, flux modulation, reluctance force) which we have reduced by up to 40dB over comparable standard motors. Then we have the position dependent inductance which causes a modulation of the drive current, again reduced by a huge factor. A new (re)discovery is the gain modulation caused by the varying radiating area of conventional surrounds – this can cause an amplitude modulation of the midrange by +-10% easily. This has been reduced by orders of magnitude by our very special surround geometry. 

     

    Finally, an extremely annoying distortion mechanism is the hysteretic memory of the iron in the motor. This distortion leads to a grainy non dynamic sound and lack of ‘black canvas’. We have managed to reduce this distortion by up to 50dB compared to industry benchmark drivers. Interestingly, the exact same hysteretic distortion can be found in class D amplifier output coils. Our 1ET400A amplifier embeds the coil in a control loop with over 70dB loop gain all the way to 20 kHz which effectively removes this distortion. We believe that the class D coil’s hysteretic distortion has been a large part of the bad reputation of early class D designs.

     

     

     

    When I asked Lars about how loud I can turn up the demo kit, he had this to say:

     

    How loud? We always end up playing insanely loud due to the lack of distortion (my ears become the limit). The woofer handles 350W IEC long term and survives bottoming (which of course sounds bad). Actually, the 100 hour power tested units have never had damages to the soft parts which is quite unusual (our special surround works like a dream to stabilize the motion). You have  +-14mm of mechanical stroke and with the lowered port tuning to 30Hz it takes quite a bit to bottom it. So just fire it up and ease back if you hear bottoming – mostly because it then suddenly sounds bad, it’s not harmful.

     

    Wow. Usually I am careful not to blow up review speakers, but this sounds like a challenge! 

     

    Kidding aside, very interesting as I have found most bookshelf speakers don’t go very loud before hearing the onset of cone breakup. For example, I own a pair of KEF LS50’s which have a nice voicing, but don’t go very loud (or very low in frequency) before audible distortion is heard as compared to PTT 6.5 (i.e. demo kit). The traditional approach to combat this is to pair satellite speakers with sub(s) to reduce the low frequency load (and IMD) on the small driver. Or in the case of the Dutch and Dutch 8c’s, put two 8” long stroke subwoofers in the back of the stand mount speaker enclosure operating at 100 Hz and below.

     

    The PTT6.5 woofer is unique in being able to reproduce a prodigious amount of low frequency energy (i.e. in the 30 Hz range), yet remain absolutely clean sounding throughout the lower mids and midrange. The only comparison I have is using large, stiff cone, short stroke 15” woofers, which is what I use today in my JBL system, in addition to Rythmik dual 18” subs. The (major) disadvantage is that these cabinets tend to be the size of fridges, look fugly and cost more dollars. Further, the 15” drivers can barely make it to an 800 Hz crossover point, whereas the PTT6.5 is crossed over at 2.5 kHz in the demo kit, but can still hit 32 Hz, all delivered with low distortion. The PTT6.5 is a subwoofer, woofer and midrange to 2.5 kHz all in one unit.

     

    Of course, it is all relative to size and SPL’s. There is no “replacement for displacement” and my large JBL’s with dual Rythmik 18” subs can easily outperform the PTT6.5 in sheer SPL’s. But, listening at “reference” level of 83 dB SPL, the PTT6.5 sounds unbelievably clean with good low frequency extension and outstanding clarity in the lower mids and midrange. A wide bandwidth, clean sounding, stand mount audiophile monitor it is.

     

     

     

    Setup and Configuration

     

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    You can see the size of the subs (not used) relative to the Purifi SPK4 demo kit. I pushed my large JBL’s out of the way (see “the fridge” far left) and placed the SPK4 in the same location, which is also the same location where I have reviewed other speakers. I set them up in a 9 ft. equilateral triangle, toed in to point right at my ears on axis. The Monoprice 24” steel stands are filled with sand and the speakers are doubly isolated from the floor using Vibrapods. One set under the stands, another set under the speakers.

     

    I have attached the PDF sheet for the SPK4 Demo Kit, a ported box tuned to 30Hz, which is the same frequency as the woofers Thiel/Small parameters resonance frequency (i.e. Fs). Thus tuned for maximum low frequency extension in a 15 liter bookshelf enclosure. I have also attached the datasheet for the PTT6.5” woofer and 1ET400A amplifier. Just before publication I received an update that there is a SPK5 demo speaker, which I have also attached the data sheet.

     

    image5.jpg The passive crossovers are built using premium parts including Jantzen air core inductors. Due to the extremely low distortion of the PTT6.5 woofer, it is important to choose good crossover filter components. Inductors must by air-core.

     

    These are heavy duty crossovers crossing over to the AMT tweeter at 2.5 kHz. The Mundorf Air Motion Transformer (AMT) tweeter is well-known for its excellent transient response and outstanding low distortion. A good match for the PTT6.5 as a demo platform.

     

    Amir measured the 1ET400A amplifier to output 257 watts @ 4 ohms with THD+N of 0.0002% and 131 watts @ 8 ohms with 0.00019% THD+N. Looking at the impedance graph in the SPK4 app note, we see impedance as low as 5 ohms in the low frequencies and lower mids. Given Lars said that the PTT6.5 can handle 350 watts and with SPK4 system sensitivity of ~ 82 dB SPL @ 2.83Vrms at 1 meter, we should be able to hit concert levels at the listening position (i.e. ~ 95 dB SPL C weighting, slow response) no problem.

     

     

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    I am using a Lynx Hilo DAC which measures around 0.001% THD+N. The Hilo’s ADC measures even better and the main reason I use this converter for my DSP loudspeaker measurements and binaural recordings. Suffice to say, all of these distortion levels are well below our audibility threshold in a typical living room listening environment.

     

    I connected the Hilo to the 1ET400A amp via its XLR balanced input connections:

     

    image7.jpg

     

     

    Putting my ear literally against the AMT tweeter I hear the faintest hiss, dead silence on the woofer. For critical listening, I listen at reference level (i.e. 83 dB SPL C weighting at the listening position). Here is an excellent article on calibrating for reference level and why we listen at this level.

     

    With the higher than normal 6.5” woofer sensitivity of 88 dB @2.83v at 1m and 350 watt power handling rating, this makes for one powerful 6.5” woofer. Note that the PTT6.5 data sheet sensitivity is for infinite baffle (2pi) whereas the usual speaker box sensitivity is stated for free space (4pi) - this tradition is a source of much confusion. This means that one should subtract 6 dB from the data sheet to get the free space sensitivity (i.e. the box baffle step is equalized down to the free field response in the passive xover and the tweeter is attenuated accordingly).

     

    I am still amazed how the PTT6.5 can cleanly belt it out without any strain every time I listen. The only other way to get that kind of kick is using what I have now, which are short stroke, large stiff cone area, 15” woofers. The “quality” of bass coming from the PTT6.5 sounds like it should be coming from my large JBL’s. It is quite the audible illusion. Of course this is only up to a certain SPL, but much louder than I expected and certainly louder and cleaner than other similar sized loudspeakers, by a good margin. 

     

    To switch it around a bit, I ended up listening to the amp/speaker combo for days before I pulled out the measurement gear. In fact, this is the longest I have procrastinated to get the measurement mic out. I just wanted to continue listening. So, let’s begin with the listening impressions first and then look at the measurements to confirm what I am hearing.

     

     

    Subjective Listening

     

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    I have listened to this demo amp/speaker combo for numerous hours over days using a wide variety of source material. Not only my reference recordings that I have linked to in previous articles, but tunes that have a combination of good low bass and midrange elements that would stress the amp/speaker combo to “give it up” in the bottom end and stress the midrange.

     

    Driving loudspeakers towards their limits can result in unexpected failures. I have “popped” woofers right out of their gap and instantly “smoked” tweeters into silence with a clipped amp signal. Sometimes it is good to start with material that is dynamically compromised to test the limits.

     

    image9.jpg Yotto’s Radiate (DR6) is a good thumping mix with significant bass centered at 39 Hz and highly compressed. So does it sound good? The PTT6.5 can certainly reproduce the deep bass. I can feel the couch vibrating from the 6.5” woofers. Ridiculous you say! I could not believe it myself.

     

    Sounds clean with good transient punch on the kick drum and the throbbing bass sounds solid. I cranked it up until 96 dB SPL C weighting at the listening position 9 feet away in 30” x 16.5’ x 8’ room.  At that SPL, I just started to notice bottoming out of the woofers on peaks. That’s +13 dB more SPL than reference level, which to our ears sounds over twice as loud. It’s concert level loud! Very rarely do I listen at this level, but it is fun for short periods 🙂

     

    Up until that point, the amp/demo speaker combo sounds crystal clear without the bass and kick drum losing any articulation and the midrange syths still sounding clear and well defined in the mix. Most speakers will tend to “break up” with distortion before reaching their full limits. Again, the PTT6.5” just kept getting louder, showing no strain, and then the bottoming of the woofer is very brief at the limit. Turn the level down a bit, and back to sounding crystal clear. A unique property that I have not heard from any other small transducer.

     

     

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    Above on the left is a spectral analysis of the first couple of minutes of Radiate along with a waveform view on the right. Can you say clipped! Significant energy focused in the 40 Hz region.

     

    image11.jpgMadonna’s Power of Goodbye (DR8) has an excellent low frequency bass line with long sustained notes. Literally feels like rolling waves as you can feel each wave that has significant energy down to 3 Hz. With my dual Rythmik F18’s I can make the house, couch, and my body vibrate and pressurize the room with this tune turned up. Makes me smile.

     

    The PTT6.5 could indeed pressurize my room and make the couch and room vibrate with some body sensation. Really impressive coming from a 6.5” (sub)woofer! At that level Madonna’s lower mids and midrange from her voice and syths still sound clear as a bell while the woofer is able to shake the room a bit on the low notes. This is unheard of from a 6.5” woofer. Mind blown.

     

     

     

     

     

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    We can see in the frequency spectrum above, the wave like pulse below 10 Hz. On the right is the waveform which is compressed, but not horrendously clipped like Radiate.

     

    image13.jpgPatricia Barber’s, Regular Pleasures (DR15) is a torture test for amps/loudspeakers with its concussive bass drum and sliding bass line. With the punch of DR15, it is downright dangerous for popping woofer cones. It is another recording with significant low frequency energy focused at 40 Hz and good content down below 10 Hz. On my dual F18’s subs the drop note bass drum shakes the house on its foundations after the initial concussive hit. 

     

    Obviously not on a 6.5” woofer but within its operational limits, sounds very deep, solid and in balance with the rest of the mix. I can still feel the bass and drums sitting on the couch. I am amazed at how low, loud, and clean these woofers can go. They have the same transient impact like my 15” JBL’s have (up to a certain SPL, but way louder than I expected) and the lower midrange is crystal clear. I mean the cleanest I have ever heard.

     

    Patricia’s voice is mixed up in level in the overall mix with the drums and bass. The lower midrange and mids from her voice sounds clear with no modulation that I could hear even when cranked right up. I can hear/feel the resonance of the lower mids of her voice unlike I have heard from many a different speaker. On most speakers I have listened to, Patricia’s voice sounds good, but a bit thin and missing the power of her lower midrange register, which I only hear on the large JBL’s… and now the PTT6.5.

     

     

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    I could go on, but the above three examples are representative of the continued enjoyment I get listening to this amp/speaker combo. Even blasting for a period of time only barely warmed up the 1ET400A chassis and case. Not once did I hear any strain from the amplification in any way. The top end sounded transparent with excellent transient response.

     

    Well, now I am curious how they measure, up close, and from the listening position. Given what I have heard, I expect good low frequency extension with a smooth lower mid and midrange frequency response.

     

     

    Objective Measurements

     

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    Here is a video of an REW measurement of the right speaker. Turn your sound down to a safe level if your web browser is hooked up to your sound system. If you look closely at the beginning, you can see how much cone excursion is going on starting from 10 Hz on up. Perfectly linear and clean sounding.

     

    The first set of measures are 30cm away from the speaker on-axis with the mic positioned between the two drivers. While the room will have its way below Schroeder, (i.e. the room’s transition frequency), I still want to see some representation of bass output. So I don’t gate my measurements and for sure the room is in the picture, but still a very smooth and extended response at both frequency extremes:

     

    image16.jpeg

     

    My room comes into play from about 300 Hz on down, with some excess room energy at 250 Hz and typical room modes down lower. The -3 dB point measured was about 32 Hz. Wow, this is a small two way with a 32 Hz to 20 kHz full range response. The SPK4 demo speaker has a similar midrange voicing as the KEF LS50 in frequency response, but the LS50 rolls off quickly after 100 Hz.

     

    Here is a quick comparo of frequency response measured in the same location and 30cm away. I have offset the measurement pairs so it is easier to compare. Purifi SPK4 Demo Kit on top, KEF LS50 on bottom:

     

    image17.jpeg

     

     

    As you can see, the response on the LS50 drops quickly after 100 Hz and is -10 dB down at 40 Hz. So this confirms for me what I heard during subjective listening as the Purifi PTT6.5 in the demo kit can put out significant output to 32 Hz, again with the lower mids and midrange sounding crystal clear.

     

    Let’s look at the demo speakers step (timing) response. What we are looking for is the “right triangle” shape which denotes an ideal speaker’s minimum phase response:

     

    image18.jpeg

     

     

    The doublet spike in front is the AMT tweeter which the passive crossover blends perfectly into the Purifi PTT6.5 woofer and has near perfect right triangle step response. Look how smooth the right triangle is with hardly any “bumps” at all which translates into how smooth the woofers frequency response is.

     

    I did not take any distortion measurements as I am not setup to perform those. No anechoic or semi-anechoic chamber, unknown distortion contributed by the measurement mic and mic preamp. Plus it’s (really!) hard to do correctly ☺ I would rely on HiFiCompass’s excellent IMD measurements to be representative of the PTT6.5 unit.

     

    Here is the frequency response as measured at the listening position:

     

    image19.jpeg

     

     

    Of course, there is more room in the picture as we know below Schroeder the room is in control of the low frequency response. I have dips at 80Hz and 90Hz and peaks in the low end – classic room modes. Nothing some DSP can’t fix, but my point here is again to show the wide bandwidth coverage of this small two way system with in-room response down to 32 Hz whether near field or far field in my room. Impressive!

     

    If you drew a straight horizontal line in-between the peaks and dips and average them across the frequency band, it would be exceptionally flat response with the normal high frequency roll-off.

     

    For fun, I hooked up my dual Rythmik F18” subs with a 90 Hz crossover point as you can see in the above chart where I have some major room issues and dialed in some DSP and this is what I got at the listening position:

     

    image20.jpeg

     

     

    One of the reasons I did this is because I am used to a particular sonic signature that I could only get with subs and large JBL 15” woofers. So I was curious if I could replicate that with the PTT6.5 and maybe lose “the fridges.” I still can’t believe how clean it sounds. Cleaner than my JBL’s… Hmmmm.

     

    Do you remember the THX intro? Sony’s intro to Spider-Man into the Spider-verse is the new THX intro. While I linked to the YouTube recordings, hearing it on Blu-ray is mind blowing. With a -3 dB point of 6 Hz in my room with the dual Rythmik F18 subs dialed in, it’s mind blowing. As the intro builds with the volume turned way up, both my daughter wife tried to hide behind the couch because it sounded like the room was going to implode at the climax. The SPK4 handled it with aplomb. Love it!!!

     

     

    Conclusion

     

    I must say, I have heard a lot of amp/speaker combos over 50 years in audio, 10 of which being a pro recording/mixing engineer, and have never heard anything like this. Or should I say the lack of distortion and outstanding low frequency extension from a 6.5” woofer. The clarity is stunning. Congrats, truly in a class upon itself.

     

    Is the PTT6.5 a subwoofer? A woofer? A midrange driver? Yes, it is all three with a measured nearfield and far field response from 32 Hz to 2.5 kHz in the SPK4 demo package. This really got me to thinking of applications for the driver. Literally makes for a perfect driver for a small format, full range 2 way accurate sound reproduction system. This made me wonder about Purifi’s business strategy.

     

    I asked Lar’s about Purifi’s technology roadmap, “Our plan is to become an OEM supplier but also serving the DIY’ers. For larger volumes, we also license our tech like we have done with NAD.  The roadmap also calls for DSP and algorithms as well as PSU’s. Our overarching strategy is to go in and overhaul the weakest links in the audio chain and break into new performance territory. Speakers and amplifiers were the natural first points of attack. Exciting to see where all this leads us to.”

     

    Makes perfect sense to me and I wish Purifi all the best. They are certainly off to an auspicious start!

     

    Purifi web shop.

     

     

    image21.jpegMitch “Mitchco” Barnett.

     

    I love music and audio. I grew up with music around me, as my mom was a piano player (swing) and my dad was an audiophile (jazz). My hobby is building speakers, amps, preamps, etc., and I still DIY today.

     

    I mixed live sound for a variety of bands, which led to working full-time in multiple 24-track recording studios. Over 10 years, I recorded, mixed, and sometimes produced over 30 albums. I am into Digital Signal Processing (DSP) and run an Accurate Sound Calibration service.

     

     

     

    Edited by mitchco



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    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

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    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

     

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    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 :)

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    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.

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    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?

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    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

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    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."

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    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

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    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

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    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!

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    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).

     

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    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

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    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.

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    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!

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    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!

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    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.

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    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.

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    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.

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    Mitch,

     

    Thank you for a comprehensive review.

    I wanted to know how it sounds at low volumes. Does it produce bass/low bass at medium to low volumes?

     

    Thanks,
    Satish

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