Purifi PTT5.25X08-NFA-01 Woofer-Mid "Running Wild," Tweeter Level at +0dB/FLAT

I previously posted about my prototype with the Eton 5-312 running wild, no crossover on the woofer (there is a network on the tweeter, obviously):

I was so tickled to learn that the Purifi PTT5.25X08-NFA-01 Woofer-Mid was a near-perfect "Drop-In Replacement" that I bought one!

First of all, that driver is heavy like a hand grenade. Lars Risbo was kind enough to fill me in that the 5.25 uses the same motor as the 6.5.

Yikes! So, the same motor, but the cone is circa 34% smaller in terms of pistonic area. I know that it is bordering on mental cruelty to post YouTubes of loudspeaker design progress... but, it's the best I can do.

As before, the demo track is Kate St. John's re-setting of the Tennyson poem "The Lotos-Eaters," which is based on a story from The Odyssey, and which also was set by Elgar.

I am hugely impressed.

My next move will be to put a woofer roll-off from 3kHz up back in, and try that out.

Thanks to all who have given advice and encouragement. Oh, the other speakers are the assembled Sasandu Txes.

The pronounced sssss's in either speaker would drive me bonkers. I'm guessing both mid-woofers would really benefit being filtered above 3khz, the Purifi expecially. Just my :2c:

Looking at the fr response, they both have a nice big peak around 5khz.

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I think that half of what you are hearing is the mic system of my iPhone, which is optimized for Speech Intelligibility rather than Musical Accuracy.

PTT5.25X08-NFA-01 FR.png

The Purifi, to my eyes at least, has a shallow dip from 700Hz to 4kHz, and then a slight rise from 4k to 5kHz

My way of working is to examine a lot of drivers holistically, trying to zero in on what they do "naturally," rather than saying to myself "I am such a genius that I can deal with all this ugly stuff by using my wonderful crossover design skills."

I grew up in audio in the 1960s and 1970s, and I have lots of respect for designs such as the Dynaco A25 that hardly had any crossover components at all. I even still have a pair of A/D/S Braun L300 Cs.

So, I first focus in the midrange (my friend Winslow Burhoe recently referred to me as "The King of the Midrange," and that was not, in context, entirely a compliment!) and seek a natural bass to midrange balance, and then later, once I am really happy with the driver selection, attend to the fine details, and bring in the specialists.

I'd actually rather go with two woofers to get around the Baffle Step problem; but that's a lot of money, and a cabinet that's almost 50% larger.

I'll report back after I put the crossover on the Purifi woofer.

My prime purpose in making this post was to let people know that the Purifi 5.25 has the same motor as the 6.5. The 5.25 is a driver to reckon with.

Thanks for your comments,

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You must you having fun. And enjoying the experiences(s). No doubt, because the brain enjoys novelty. This is evidence based.

Now I want to move onto more serious matters. Those measurements that Purifi posted are on an infinite baffle. That means on a baffle virtually approaching infinitely large, with none of the sound-waves being affected by the baffle edges or coming off the back of the test chamber towards the microphone.

Second, it is on-axis only. That is, directly in front of the driver.

What one usually hears is instead a mixture of on axis, and off axis sound, of the driver, in the particular cabinet, in your particular room, with/out the filter.

All these things affect what you are hearing.

Both the direct sound (measurable) and indirect sound (reflected sound, more difficult to measure)

Please consider investigating the use of measurements as you proceed.

To correlate what your good ears are hearing with what you are seeing.

Otherwise one is prone to misleading oneself. Now

I'm not saying measurements mean everything, but they will help with the correlation/association.

How big is your loudspeaker cabinet?

Here are some measurements of the PTT5.0X04NFA drive in a 12" H x 8" W x
8" D cabinet, with a 12"x8" rectangular baffle (no roundovers). If you cabinet is similar, your measurements will be similar.


As you can see, there is no droop after 700Hz; the baffle causes a peak. So between 500Hz and 2KHz it it pretty flat (+/- 1dB). There is indeed a peak at 5KHz. Furthermore, there is a loss below 500Hz due to baffle step. Adding another woofer, alone, won't help with the baffle step losses. You need baffle step loss compensation (2-way), or to low pass off one woofer above 500Hz (2.5 way)
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You must you having fun. And enjoying the experiences(s). No doubt, because the brain enjoys novelty. This is evidence based.

Now I want to move onto more serious matters. Those measurements that Purifi posted are on an infinite baffle. That means on a baffle virtually approaching infinitely large, with none of the sound-waves being affected by the baffle edges or coming off the back of the test chamber towards the microphone.

Second, it is on-axis only. That is, directly in front of the driver.

# # #

Thanks for your thoughtful reply!

I am very aware of the differences between the "ideal" of data sheet graphs and the "reality" of real-world implementations. I started mucking around with loudspeakers in the mid 1960s, and in the mid 1970s and on I enjoyed close friendships with Irving M. "Bud" Fried and with Dick Shahinian, and I had some meaningful conversations with John Dunlavy. (Some of the readers of this are now face-palming and muttering, "The three worst possible old-school, subjectivist, First-Order Crossovers/'Overlap Those Drivers' Mentors or Gurus one could ever have!")

I did a quick Pink Noise recording 1m on axis and then I put the crossover on the woofer, and just as I expected, the overlap of the drivers had made a big peak centered around 4k. I somehow managed not to jump off the Newport Bridge. A very experienced conductor who has conducted all over Europe (and in New York and New England) once said to me, somewhat in exasperation, "You hear like a violinist. Violinists are always searching for the perfect note." As in, he did not think I am a big-picture guy when it comes to sound.

Wild vs XOver @3k.png

Oh, for comparison, here is a spectrum of the digital data for the StereophileTest CD2 Pink Noise, which is the best I have found.

JA Pink Noise Spectrum.png

With the crossover on the woofer, the loudspeaker sounded more like "Good Hi-Fi" and it had less of the "electrostatic" immediacy of the Running Wild version, and I am talking about frequencies all the way down to below middle C (Baroque bass lute).

The baffle is 8.5 inches which means that the distance from the center of the woofer to the (rounded over) edge is about the wavelength of 3.2kHz. So I have always known that there would be a baffle step issue. There's no question that Running Wild exacerbates female vocal sibilance.

In answer to another chap's question why I posted on YT iPhone videos, it's because I could not find anyone reporting on DIYA about progress on a PTT5.25 implementation, and I was very impressed with the driver, and I wanted to share my enthusiasm.

Responding to another, I don't play music back loudly enough to excite the piano strings, and the dampers are down anyway. It's nice to have a keyboard (of any kind) to help calibrate one's thinking. A number that looks significant in a vacuum looks different when you remind yourself that it is only the difference between a C# and an F#. As in, going from one black key to the next black key on a piano.

I think I have gotten as far as I can with the NeoCD3.0, so I will next investigate a RAAL ribbon tweeter. I think the Purifi deserves it!

When I get to a point where my Golden Ear Friends and I are happy, I will ship the work-in-progress off to Jim Tuomy. Jim has six patents in electroacoustics; he was awarded the Bose Corporation's "President's Medal," and he has $20,000 worth of Audio Precision test equipment. And he has his own network of colleagues to consult with. Also, Dennis Murphy of Philharmonic Audio said he would be willing to work with me on crossover design. So, this project does not lack for Adult Supervision, to balance out my Boyish Enthusiasm.

There are designers out there who spend a lot of effort trying to extract "sunbeams" from the "cucumbers" of a $28 woofer and a $14 tweeter, and they end up with a small fortune in crossover parts. Or at least, lotsa cheap crossover parts. Which, as far as I am concerned, is just rubbing Vaseline on the camera lens to make Norma Desmond look younger.

I hope everybody has seen Danny Ritchie's wonderful critique of the P3ESR:

I'd rather start with drivers of the highest possible quality, and minimize the electrical interventions.

Just to prove that it did not work for me, I built a semi-BBC-Legacy sealed shoebox with a symmetrical L-R 4th order crossover, and: It did not work for me! 21st Century Audiophile Sterility.


Thanks for all for reading and commenting.

Thanks for following up. Things have been moving, but slowly.

1) Jim Tuomy measured the Purifi/Fountek prototype:

John Speaker copy.png

2) Jim let me know that he thought that the Fountek tweeter was not up to the quality of the Purifi woofer, so, we bit the bullet and switched the tweeter to the Beyma TPL-75 AMT, which is an amazing driver. The cost differential being $200/each, one would hope that it is amazing. Please note, the crossover at that time had three different sets of tweeter level-setting resistors.

Also please note, I of course know that the photo below is of the Beyma AMT with the since displaced Eton 5-312 woofer. The Eton woofer is there only for size. The cabinet maker lives some distance away and it was easier for him to use the Eton as a reference than for me to box and mail the Purifi woofer to him.

1 Beyma front panel for MDF Mule.jpg

3) We then decided to switch from a port-with-cocktail-straws design to Purifi's recommended 2 X Passive Radiators. Which require a slightly larger cabinet. Jim Tuomy asked that we not offset the tweeter, so we changed that too. Also, this is the first cabinet where the shell and rear panel are solid Richlite, earlier prototypes had MDF shells. So this is a Richlite Stratum Bamboo composite front panel and a solid Richlite shell:

12 14 progress picture.jpg

As soon as the cabinet maker finishes the rear panel mounting arrangements, we will acoustically treat the inside of the box and wire up the drivers and send the cabinet to Dennis Murphy of Philharmonic Audio for the crossover design.

We are hopeful that we can lower the crossover point from 2500Hz to 1800Hz.

The next phase will take a few weeks.

Thanks again,

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