NEW PURIFI 8'' MWoofer [PTT8.0X04]

[hardisj]

Nice! Thanks for this. Will you be writing a Thoughts / Conclusion subjective section?

Not a lot to really talk about but it'll be in a video. The data just gives you an idea of where to place crossover points and use EQ/notch filters. This is why driver testing isn't all that interesting to me anymore... what matters is the final implementation. A driver like this helps you get more out of a speaker but someone can easily screw it up with the wrong crossover/baffle.

 

[617]

The bandwidth is not bad for an 8 inch woofer, but I'm not sure what speaker needs this woofer. Small speakers don't have 8 inch woofers, and big speakers don't have just one. The bandwidth on the smaller speakers was truly excellent, by the way, smoother than many dedicated midrange drivers which produce no bass at all.

Might be nice for a stand mount 3 way monitor for professional use, but if performance is your goal, multi subs are going to be the way to go.

The purefi drivers are amazing but it's no mystery why they don't have much competition.

 

[617]

Not a lot to really talk about but it'll be in a video. The data just gives you an idea of where to place crossover points and use EQ/notch filters. This is why driver testing isn't all that interesting to me anymore... what matters is the final implementation. A driver like this helps you get more out of a speaker but someone can easily screw it up with the wrong crossover/baffle.

Erin it's cool to see driver reviews. Fan service for speaker nerds. We are grateful.

 

[changster]

The bandwidth is not bad for an 8 inch woofer, but I'm not sure what speaker needs this woofer. Small speakers don't have 8 inch woofers, and big speakers don't have just one. The bandwidth on the smaller speakers was truly excellent, by the way, smoother than many dedicated midrange drivers which produce no bass at all.

Might be nice for a stand mount 3 way monitor for professional use, but if performance is your goal, multi subs are going to be the way to go.

The purefi drivers are amazing but it's no mystery why they don't have much competition.

Tons of applications I think. 3 way front ends for car audio, 3 way bookshelf’s, 2 way bookshelf’s with a tweeter that plays low (Bliesma T34B-4’s?), etc.

 

[DDF]

Purifi have an app note that shows how to use a passive notch filter to tame the aluminium drivers breakup

https://purifi-audio.com/wp-content/uploads/2022/03/220211_R05-Notchfilter.pdf

View attachment 210905

That was a great read, thanks for sharing it.

Unfortunately the driver peak frequencies vary with angle of observation, so their simple notch filter approach (based on on-axis only) won't work well, it'll mismatch off-axis (see below). IME with a driver like this, it calls for a low Q broad notch. It's common to have the peak vary with angle of observation, so I prefer the peaks as high in frequency as possible so that the broad notch still allows a decently high low pass corner frequency.
This might be usable 2 way, but it would need a bullet proof tweeter and probably lower than 2300Hz cross over claimed, or a zero-based (not all pole) filter where the notch is designed into the high order alignment

 

[hardisj]

Erin it's cool to see driver reviews. Fan service for speaker nerds. We are grateful.

I’ve got one that’s really neat coming soon.

 

[changster]

I’ve got one that’s really neat coming soon.

There are many of us who pray you go back to your car audio roots and help the car audio community as much as you’ve done for the home hifi community!

 

[617]

I’ve got one that’s really neat coming soon.

What is it?? Spill the beans

 

[hardisj]

What is it?? Spill the beans

 

[abdo123]

The bandwidth is not bad for an 8 inch woofer, but I'm not sure what speaker needs this woofer. Small speakers don't have 8 inch woofers, and big speakers don't have just one. The bandwidth on the smaller speakers was truly excellent, by the way, smoother than many dedicated midrange drivers which produce no bass at all.

Might be nice for a stand mount 3 way monitor for professional use, but if performance is your goal, multi subs are going to be the way to go.

The purefi drivers are amazing but it's no mystery why they don't have much competition.

It's a reasonably sized driver that is completely not excursion limited from 100Hz and up with an uncompromising mid range performance.

It can't get better than this in a 2-way setup.

 

[McFly]

my bet is that crazy looking tweeter that looks like rappers grills

And Erin, that IMD data your providing is revolutionary. That, IMO, is the most revealing measurement of the clarity of a speaker driver.

 

[RickS]

That was a great read, thanks for sharing it.

Unfortunately the driver peak frequencies vary with angle of observation, so their simple notch filter approach (based on on-axis only) won't work well, it'll mismatch off-axis (see below). IME with a driver like this, it calls for a low Q broad notch. It's common to have the peak vary with angle of observation, so I prefer the peaks as high in frequency as possible so that the broad notch still allows a decently high low pass corner frequency.
This might be usable 2 way, but it would need a bullet proof tweeter and probably lower than 2300Hz cross over claimed, or a zero-based (not all pole) filter where the notch is designed into the high order alignment

View attachment 211366

While true about the 8 inch driver, the Purifi app note is for the 6.5 inch driver. The 6.5 inch driver has better alignment of its off-axis resonances and so high Q notch filters should be much better. Would help if they showed off-axis results too.

 

[sarumbear]

And Erin, that IMD data your providing is revolutionary. That, IMO, is the most revealing measurement of the clarity of a speaker driver.

May I ask what is the basis of your opinion? It is exceedingly rare to find IM measurement of drivers. Do you mind sharing the data of other drivers where you have noticed that clarity effect?

 

[HammerSandwich]

Purifi Audio PTT8.0X04-NAB-02 8 Inch Woofer Review

Purifi Audio PTT8.0X04-NAB-02 8 Inch Woofer Review

www.erinsaudiocorner.com

@hardisj, I see this in the Purifi reviews:

The test baffle has a sealed volume of approximately 2ft³, though, this speaker is sealed and my baffle wall enclosure has no further effect on the low-frequency response already imparted by the speaker’s internal enclosure.

Is that just a copy/paste from the in-wall reviews or something? If not, what do you mean that the speaker is sealed?

 

[hardisj]

@hardisj, I see this in the Purifi reviews:

Is that just a copy/paste from the in-wall reviews or something? If not, what do you mean that the speaker is sealed?

copy/paste. I'll fix that. Thanks for the heads up.

 

[Savi]

my bet is that crazy looking tweeter that looks like rappers grills

And Erin, that IMD data your providing is revolutionary. That, IMO, is the most revealing measurement of the clarity of a speaker driver.

I agree, it's a great data. Only regret is that the bass ton frequency is not modified given driver use. For instance, for the purifi midrange I will have chosen 150hz and/or 350hz. This driver will probably be used in the 200hz-2300hz range.

 

[beren777]

Would this driver be good for a 3-way large bookshelf or small/medium tower intended for 50/50 music/HT use with a subwoofer? Or would the money be better spent on a less expensive 12" woofer, crossed to the Purifi 6.5M as the mid driver? (I was pondering a SB34NRX75-6 12" woofer / PTT6.5M04-NFA-01 / Some Tweeter crossed at 150Hz and 2100Hz, with the Purifi handling the middle range.)

 

[briskly]

Would this driver be good for a 3-way large bookshelf or small/medium tower intended for 50/50 music/HT use with a subwoofer? Or would the money be better spent on a less expensive 12" woofer, crossed to the Purifi 6.5M as the mid driver? (I was pondering a SB34NRX75-6 12" woofer / PTT6.5M04-NFA-01 / Some Tweeter crossed at 150Hz and 2100Hz, with the Purifi handling the middle range.)

The primary positive characteristics of this driver compared to similarly-sized units are
-Extended and even axial response
-Above-average linear excursion performance compared to most 8" woofers/higher efficiency above Fs than most 8" subwoofers
-Stable inductance wrt current over the audio bandwidth (good midrange linearity)

The subwoofer cuts into the LF requirement, and a large midrange unit strips out the use for upper-frequency response. Unless you want to go high-power and chase a low sub transition, it does not seem like a good idea. Even then, the 8" paper version would be a better choice.

I doubt this driver is suitable for a 3-way speaker like the 8c. Its strong suit is playing both mid and bass with low distortion. So this driver should be better of with a 2/2.5-way speaker.

or maybe I'm wrong

An 8C-type speaker is not a popular niche, but it represents one of the best possible uses for this driver, specifically as a midrange unit. The leaky midrange chamber drives up displacement requirements. It would clean up some graphs, if not necessarily the subjective experience.
Needs more volume displacement to benefit the LF section.

 

[617]

I’ve got one that’s really neat coming soon.

I checked and you measured a vifa d25 or something...

 

[Ra1zel]

Idea for a true high end DIY speaker system:
▪︎Some top range tweeter in custom revel-style waveguide
▪︎5" midrange (purifi?)
▪︎Two of those 8" relegated to 1khz-100hz
▪︎PC based active XO/filters --> Okto DAC8 Pro --> Purifi amps or equivalent (benchmark/neurochrome/new hypex)
▪︎Tune not full range, pair it with at least 2 subs

A lot of effort and money but tremendous potential to optimize for ultra low thd/imd and possibility to surpass most commercial solutions available now.

Wonder what people think about that.