Purifi PTT6.5W04-01A 6.5" midwoofer

[Matias]

Review and measurements here
https://hificompass.com/en/reviews/purifi-audio-ptt65w04-01a-midwoofer

 

[eliash]

I find quite interesting that on a "science" forum the only reactions to a surround shape which is obviously the result of computer assisted design are:



Measurements are also provided, on which nobody gives a f..., for the good or for the bad.

You guys are funny sometimes

Actually I am fascinated by that surround. It could work, know why? When I recently retired my 1982 homemade 3-way speakers with Dynaudio´s 30W-54 woofers (had already the second surround installed), the visible crooks and twists on the surround (break-up vibrations), when sweeping it, looked very similar. Probably they got inspired by such effects and put an opposite twist surround shape to it, to compensate.

 

[Killingbeans]

Restorer-john mentioned it on the first page:

Looks like they are re-resurrecting the wierd roll surrounds everyone was doing in the 80s for more "linear" excursions. (they all fell to pieces eventually)

It's not a new idea, and personally I have no doubt it works. But the concern about the surround material being mechanically stressed in an unfortunate way is also very real.

I think they look cool, and if they really make a significantly positive contribution to the abilities of the driver, then I won't mind having to replace the surround when(/if?) it crumbles at some point... I'll just have to keep my fingers crossed that spares will be available.

 

[Archmage]

I suppose limiting excursion by placing these drivers in a 3-way (maybe start at 200-220hz or so) might extend the life of the surround if that's a concern. I find most 2-way systems anemic regardless.

I kinda wish it were a 5.5" or 6.0" in that case - it'd help with the tweeter transition as well, as it looks like this driver has a minor hiccup around 1.5 to 1.8Khz, and then becomes less usable past 2Khz WRT both dispersion and distortion. It can be difficult to get a tweeter to play that low w/o straining if you're aiming for high SPL capability and at least somewhat matching the Purifi's distortion.

Edit: Although someone mentioned the Bliesma T34B-4 on the 1st page - plays loud, low, and costs just as much

That said, this driver seems to best the distortion measurements of some of the past top drivers.

 

[JustIntonation]

I suppose limiting excursion by placing these drivers in a 3-way (maybe start at 200-220hz or so) might extend the life of the surround if that's a concern. I find most 2-way systems anemic regardless.

I kinda wish it were a 5.5" or 6.0" in that case - it'd help with the tweeter transition as well, as it looks like this driver has a minor hiccup around 1.5 to 1.8Khz, and then becomes less usable past 2Khz WRT both dispersion and distortion. It can be difficult to get a tweeter to play that low w/o straining if you're aiming for high SPL capability and at least somewhat matching the Purifi's distortion.

Edit: Although someone mentioned the Bliesma T34B-4 on the 1st page - plays loud, low, and costs just as much

That said, this driver seems to best the distortion measurements of some of the past top drivers.

Yes, the T34B-4 (or T34A-4) would be a great match.
I almost went this route myself. Though I was a little bit worried about diffraction off the Purifi surround when placing the tweeter close.
Reason I didn't go this route was mainly because a quality 5" driver + 10" woofer combined easily beat the Purifi in bass distortion and closer ctc between mid and tweeter, at a similar total price. Though if one must make a 2-way the Purifi is a no-brainer. Btw the Purifi has a very flat frequency response up to 1kHz, not many drivers do it that well, one will only need to correct there for baffle step.

 

[Killingbeans]

I suppose limiting excursion by placing these drivers in a 3-way

I've been contemplating the same thing... but going that route just sort of makes this driver unnecessary.

I kinda wish it were a 5.5" or 6.0" in that case - it'd help with the tweeter transition as well, as it looks like this driver has a minor hiccup around 1.5 to 1.8Khz, and then becomes less usable past 2Khz WRT both dispersion and distortion. It can be difficult to get a tweeter to play that low w/o straining if you're aiming for high SPL capability and at least somewhat matching the Purifi's distortion.

@617 mentioned the Wavecor TW030WA11/12. It's a large dome tweeter with a small waveguide (more like a tiny horn loading?), but it should fit a crossover somewhere between 1.5 and 2K pretty well?

 

[Matias]

Woofer and passive radiator are for sale!
https://purifi-audio.com/vare-kategori/transducers/

Also new 4" mid/woofer announced
https://purifi-audio.com/transducers/ptt4-0w04/

 

[pos]

I suppose limiting excursion by placing these drivers in a 3-way (maybe start at 200-220hz or so) might extend the life of the surround if that's a concern. I find most 2-way systems anemic regardless.

Rubber surrounds do not suffer the same rotting issues as the old foam ones (EDIT: not to the same degree at least). These will probably last longer than the spider.

Regarding using this woofer in a 3 way, I think this is somewhat contradictory with the very aim of the design here. There are better solutions for the lower range (bigger woofers, or less expensive ones), and also better solutions for the upper range (smaller, lower excursion, less expensive ones...).
The interest here is to have a single woofer covering the entire range.

 

[pos]

Woofer and passive radiator are for sale!
https://purifi-audio.com/vare-kategori/transducers/

That is clever!

 

[SIY]

Rubber surrounds do not suffer the same rotting issues as the old foam ones.

I wish that were true. I had to toss four 30W54s and two 21W54s when their surrounds rotted out.

 

[Thomas savage]

I wish that were true. I had to toss four 30W54s and two 21W54s when their surrounds rotted out.

Iv had rotted rubber surrounds on my old vivid b1's.

 

[pos]

I wish that were true. I had to toss four 30W54s and two 21W54s when their surrounds rotted out.

I could be mistaken, but these definitely look like foam surrounds to me, not rubber:
https://medias.audiofanzine.com/images/normal/dynaudio-30w54-2717669.jpg
On the plus side, foam surrounds are easy to replace:
https://www.speakerrepairshop.nl/en...und-for-dynaudio-30w54-woofer/a-1437-10000020

 

[SIY]

I could be mistaken, but these definitely look like foam surrounds to me, not rubber:
https://medias.audiofanzine.com/images/normal/dynaudio-30w54-2717669.jpg
On the plus side, foam surrounds are easy to replace:
https://www.speakerrepairshop.nl/en...und-for-dynaudio-30w54-woofer/a-1437-10000020

The ones on mine were definitely butyl rubber.

 

[eliash]

The ones on mine were definitely butyl rubber.

Didn´t follow the whole discussion here, but since I have speakers based on 30W-54´s, I can assure you that originally they are equipped with foam surrounds since 1982, which lasted in my case about 12-15y. The first decomposed set repair was a complete woofer exchange through Dynaudio. Since they seem to have stopped offering that exchange service, I had s.o. in Germany exchange them for me (apparently well done) the second time. This guy offered also rubber surrounds as alternative, but hinted that the mechanical characteristics of the driver are significantly changed by that.
Finally I retired them some 3y ago (even though the foam surrounds are still OK), since break-up modes occured on the membranes (losing stiffness as well?) and surrounds...

P.S. Around 82 Dynaudio changed from paper cones to propylene ones, mines are propylene already...


Late remark: It´s polypropylene (PP), propylene is a gas...

 

[pos]

Rubber surround are not eternal either, but so is the spider (sagging), especially with high compliance woofers.

 

[eliash]

Rubber surround are not eternal either, but so is the spider (sagging), especially with high compliance woofers.

Spiders still looked Ok in my case, but it could be that minimal imhomogeneities also amplify the membrane wobbling...

 

[pos]

The ones on mine were definitely butyl rubber.

Let's hope purifi uses better quality rubber then.
Recent foam surrounds replacements are already often much more durable than the old ones, so there is hope

 

[eliash]

BTW., regarding that hot discussion about Doppler-distortion and IMD some pages before,
did you notice Purifi has new articles posted on these subjects:

Purifi / tech articles

 

[DDF]

BTW., regarding that hot discussion about Doppler-distortion and IMD some pages before,
did you notice Purifi has new articles posted on these subjects:

Purifi / tech articles

Yup, its the signal envelope that matters, and long term averaged harmonic measurements won't capture that.

 

[eliash]

Yup, its the signal envelope that matters, and long term averaged harmonic measurements won't capture that.

Yeah, it´s amazing how much more AM is audible, compared to FM/PM...considering same spectra