Purifi SPK5 Speaker Review (Prototype)

[andreasmaaan]

The understanding I had was they pushed up the XO point because they couldn't find a tweeter with distortion levels at the low-end of its passband that matched Purifi's distortion at the high end

Perhaps they could have expanded their “search” beyond $1k+/pair exotic tweeters that apparently can't even manage a 3kHz XO without significant distortion...

 

[Selah Audio]

This is a design made by Purifi to show that their 6.5” woofer can go up to ~3500Hz. It’s optimal crossover is ~1500Hz and lower, which almost no AMT/ribbon and most 1” tweeters can’t handle; @March Audio is using a BleiSMa 1.3” tweeter that can handle a 1500Hz crossover.

Um, I would beg to differ on that crossover point. I was able to cross higher than 1500Hz with very good results.

 

[Selah Audio]

Does anyone know what port configuration Purifi recommended? I don't recall seeing that.

It's best with a passive radiator.

 

[MZKM]

Um, I would beg to differ on that crossover point. I was able to cross higher than 1500Hz with very good results.

I agree, “very good”, just not optimal.

Here is Erin’s normalized horizontal off-axis of your speaker:

There is a slight directivity mismatch from 1kHz-2500Hz.

Here is the normalized off-axis of the woofer itself (HiFiCompass measurement):

Starts to beam around 1500Hz.

 

[hardisj]

Here is the impedance graph:

Our port issue/resonance is clearly apparent. Can't figure out the messiness around 30 to 40 Hz though. Anyone has a guess for that?

Based on the impedance graphic alone, this speaker definitely looks broken.

 

[hardisj]

and FWIW, I've seen the impedance curve do some weird things simply by the amount of force the screws are tightened to hold the speaker drive units in place. I know that sounds weird, but I have seen it happen numerous times. The difference between a speaker tightened all the way down vs a speaker that is loosely held in place by screws is not just measurable but can also be significant in my experience. So, if that can make a difference, anything is up for grabs. Given the impedance of this speaker, I have to think there is something broken here.

 

[MZKM]

and FWIW, I've seen the impedance curve do some weird things simply by the amount of force the screws are tightened to hold the speaker drive units in place. I know that sounds weird, but I have seen it happen numerous times. The difference between a speaker tightened all the way down vs a speaker that is loosely held in place by screws is not just measurable but can also be significant in my experience. So, if that can make a difference, anything is up for grabs. Given the impedance of this speaker, I have to think there is something broken here.

Why are you online and not finishing up that Heresy review you said you’d hope to have up by Sunday

Just kidding, but yeah not hard to imagine something is wrong when it was so damaged in shipping. Purifi is sending in their own model, but I don‘t care that much, as this design is just to show off that the woofer can be crossed high to accommodate the needs of smaller AMT/Ribbon speakers.

 

[Rick Sykora]

Thanks for the review Amir. I like the speakon connector. I like working with plywood. I usually use 3/4 for everything. I have to wonder too if MDF would be a better choice for a high performance speaker though.

I have had similar experiences with shipping from the UK to the US. I think someone has a policy to toss everything down a giant flight of stairs or something. I don't know what the deal is. Romania, Russia, China, Taiwan, Hong Kong, France, Germany... no issues. Last time I got some LPs from the UK I laughed out loud when the package arrived because it was so rough and dirty and boot-marked, and that is what I have come to expect.

If built to the plan, the front baffle calls for MDF and there is a rather major diagonal brace in the center of the (plywood) cabinet. I tend to build with MDF but have had good results with quality plywood. I suspect the problems are more related to the shipping abuse (and maybe not gluing the back panel). Have limited experience with UK shipping, but have seen some pretty beat up packages domestically too!

 

[hardisj]

Why are you online and not finishing up that Heresy review you said you’d hope to have up by Sunday

LOL

I am actually working on it right now from work. I have some downtime between my runs.

OT but I gotta say... I'm getting to the point where I hate typing up my reviews. It takes so much freaking time. I am leaning more and more toward posting the data to my site and let any/all commentary be done in my videos.

 

[Rick Sykora]

Does anyone know what port configuration Purifi recommended? I don't recall seeing that.

The port in the specs is pretty convoluted (trying to fit within the cabinet) and likely to close too the back of the tweeter...

Did the test speaker have something else?

 

[617]

The port in the specs is convoluted and likely to close too the back of the tweeter...

View attachment 95585
Did the test speaker have something else?

Speaker has a damn tapeworm. PR should really be mandatory; no way to build a compact speaker with a big port. You need a big port for a driver with this kind of xmax.

Incidentally, I believe the anarchy woofers have similar xmax, although their distortion may be marginally greater and top end not as smooth.

The best off the shelf tweeter for a demo would probably be the new SB Beryllium with the built in waveguide. I'm not really sure what the purpose of this design exercise is, really, or this woofer for that matter.

 

[Biblob]

The best off the shelf tweeter for a demo would probably be the new SB Beryllium with the built in waveguide.

That one does look good!

 

[GimeDsp]

The speaker is a reference design from the designers of the bass driver - which comes from the same crowd as the Purifi amplifiers - so some pedigree, especially in DIY circles. As a reference design it isn't really supposed to be a commercial product. It is supposed to be built by potential clients so they can evaluate the driver. Nothing special about an external crossover etc, it does however allow for easy modification. Much like many reference designs in electronics. Otherwise it is supposed to be an easy build, with no special woodworking or effort needed. There is no expectation that anyone would be wandering into their local audio dealer and purchasing this exact design.
But the DIY community being what it is, a heap of them will be made. Many DIYers don't design, they wait for designs by others. So this fills that need. (IMHO badly.)

OK, now it all makes sense. I've heard a lot about the Purifi stuff but haven't taken the time to dive deep into it yet.
NOW it makes sense why Amir was shocked at the blacked out crossover board, haha. If this is for design and reiteration then a blacked out crossover board is pretty crazy....but also pretty?

 

[kipman725]

The whole two drivers on a flat baffle type speaker seems dated, no hope of decent vertical polars. Why are DIY efforts so superior to all but Genlec?
https://www.diyaudio.com/forums/multi-way/285030-bookshelf-multi-source-horn.html

 

[Adam_M]

That one does look good!

...Yep! I've been modeling that one using manufacturer specs for a couple months. That's going to be my next speaker build (with all appropriate measurements...)!

 

[Ilkless]

Speaker has a damn tapeworm. PR should really be mandatory; no way to build a compact speaker with a big port. You need a big port for a driver with this kind of xmax.

Incidentally, I believe the anarchy woofers have similar xmax, although their distortion may be marginally greater and top end not as smooth.

The best off the shelf tweeter for a demo would probably be the new SB Beryllium with the built in waveguide. I'm not really sure what the purpose of this design exercise is, really, or this woofer for that matter.

Yeah, there is really only one justification for this driver: when you absolutely can't go larger in size, nor use subs for whatever reason, and are willing to pay for it. A single Purifi with the dual PRs it ideally needs is a $700 proposition. To put into perspective, that's a single Ellipticor, dual Scanspeak Illuminators or 3(!) Scanspeak Revelators/SB Satoris. Drivers all still within a shout of SOTA. Even if they don't individually reach the levels of Purifi at its peak potential, I'm sure as hell the performance gap for all these is small enough that doubling or tripling them pulls ahead (while still having great small signal performance).

Hell, I could even sidestep all this crazy mandatory PR stuff by speccing custom Skaanings for sealed use and still come out ahead with BOM left over for a good midrange driver.

 

[GimeDsp]

Correct me if I am wrong, but building a speaker with a smaller box and asking it to go low requires more power and greatly lowers sensitivity.
It seems to me that if shipping and manufacturing costs aren't issues then why would performance oriented designer/builders choose to build a small box/low sensitivity speaker?

Does purifi state needed power for these?

 

[Ilkless]

Correct me if I am wrong, but building a speaker with a smaller box and asking it to go low requires more power and greatly lowers sensitivity.
It seems to me that is shipping and manufactur cost aren't issues then why would performance oriented builders choose to build a small box, low sensitivity speaker?

Does purifi state needed power for these?

Because some people for whatever reason want to push the limits of SPL, extension and accuracy within a small box, and are willing to pay disproportionately more for that. (I know the prototype design doesn't show it, but this is a highly-competent raw driver that rewrote the SOTA for its size, but is almost impossible to design an effective port for within the small 2-way standmount form factor it makes the most sense in).

 

[617]

You know what tweeter would mate really well with it? A small midrange and a 40 dollar dome. I really do think the small form factor 3 way is an interesting and viable approach.

 

[sarumbear]

I wonder why they haven't used their (matching?) passive radiator? That would have avoided the high frequency port resonances.

https://purifi-audio.com/transducers/ptt6-5pr-01/