Purifi PTT6.5W04-01A 6.5" midwoofer

[SIY]

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...

Mine were the paper ones. I did not like the polypropylene ones nearly as well. FWIW, the surrounds on my 17W75 and 17W75EXT are also butyl.

 

[Matias]

Another review
https://audiophilestyle.com/ca/revi...and-1et400a-amplifier-technology-review-r866/

 

[briskly]

Noticed this little addition to Purifi's site, with very minimal specifications for now. 10mm linear stroke with a 4" nominal driver would be outstanding. It could yield a portable speaker that outputs something resembling bass. Qts is high, but the trend for compact speakers is digital control and correction. Still, I think a stronger motor would be easier to work with.

https://purifi-audio.com/transducers/ptt4-0w04/

 

[KSTR]

The motor is already very strong for the driver size and VC diameter, but obviously most of the coil is out of the gap, given the huge excursion. This reduces Qes via (BL)²/Re as Re is dominantly parasitic.

 

[q3cpma]

Would be nice to have a 8", or whatever diameter they need to achieve 25~30 Hz with low distortion at moderate SPL.

 

[JskG]

Any thoughts on using this for a modified LXmini?

 

[Pultzar]

Any thoughts on using this for a modified LXmini?

I am thinking this exact thing! I actually have an LXmini kit that is yet to be built. Was thinking of building the stock version, measuring, then swapping in the purify driver and adjusting the processor to yield the same frequency response (as much as possible).

 

[Deleted member 2944]

This driver's quite a bit bigger (and way more expensive) than the LXmini driver.
You could alter the response so it measures about the same at a single point, but the polar response of the system will be considerably different. Whether that's a large problem, I dunno.

Dave.

 

[Pultzar]

This driver's quite a bit bigger (and way more expensive) than the LXmini driver.
You could alter the response so it measures about the same at a single point, but the polar response of the system will be considerably different. Whether that's a large problem, I dunno.

Dave.

Yes it would be a different animal for sure!

 

[Juhazi]

I can't see any problems with using 6½" instead of 6" in LXmini. Directivity difference is minimal, hardly measurable at all in this application because xo is at 855Hz acoustically - and can be easily shifted/eq'd with the dsp unit.

https://www.linkwitzlab.com/LXmini/Design.htm
https://www.madisoundspeakerstore.com/2-way-speaker-kits/lxmini-linkwitz-lab-speaker-kit-pair/

Here is directivity of L16 and Purifi 6,5

 

[Deleted member 2944]

The LXmini points the woofer upward, so any directivity difference is more pronounced. You never listen "on axis" to the driver as in generalized driver measuring conditions.

SL, if he had his druthers, would have preferred a smaller driver for the LXmini, not a bigger one. A larger driver moves the trade-offs in the wrong direction, in his way of thinking.

Dave.

 

[JskG]

The off axis charts look similar - but they dont measure 90* off axis.

For the coupling, you need a slightly larger one. Maybe this model: 1051-54

 

[Pultzar]

The LXmini points the woofer upward, so any directivity difference is more pronounced. You never listen "on axis" to the driver as in generalized driver measuring conditions.

SL, if he had his druthers, would have preferred a smaller driver for the LXmini, not a bigger one. A larger driver moves the trade-offs in the wrong direction, in his way of thinking.

Dave.

They do have a 4" coming out

 

[Deleted member 2944]

They do have a 4" coming out

Yes, I saw that. Now that would catch Siegfried's eye.
He's just chuckling at all of us now anyways.

Dave.

 

[JskG]

Is anyone interested in a group buy? Id like to get a pair to try out. Sorry if this was covered earlier in the thread; I tried to search for that.

 

[arboleda]

Just noticed this group buy. There’s also a bit of discussion around diy speaker designs to put them:
https://www.diyaudio.com/forums/group-buys/348234-purifi-ptt6-5w04-01a-woofer-buy.html

 

[Ilkless]

Just noticed this group buy. There’s also a bit of discussion around diy speaker designs to put them:
https://www.diyaudio.com/forums/group-buys/348234-purifi-ptt6-5w04-01a-woofer-buy.html

Group buy pricing is great. That's right in between Revelator and Illuminator retail and much lesser than Skaaning iirc even in mass quantities.

 

[McFly]

Would be nice to have a 8", or whatever diameter they need to achieve 25~30 Hz with low distortion at moderate SPL.

I second this, a 8" for a two way with high-SPL, near full range, low distortion capability
The 6.5" might come close, I'm almost tempted to grab a pair

 

[arboleda]

I’d really like to see a DIY speaker design for them to emerge.

 

[jsy]

I’d really like to see a DIY speaker design for them to emerge.

There's the SPK5 evaluation build document that Purifi released, does that fit the bill? Or were you thinking a kit of some kind?