Purifi PTT6.5W04-01A 6.5" midwoofer

[arboleda]

Yeah I’d like a kit. I’m actually curious whether these will end up in a floor stander kit I see chatter that they’re happy in a 2-way bookshelf based on specs. I’m happy with my LS50’s for bookshelf but am eying an eventual floor standing DIY.

 

[arboleda]

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

Do they have specs on the cabinet construction design and crossover? I haven’t seen them. If I could do these as a kit I’d send one to Amir.

edit: oh I see it now. May build one for Amir.

 

[jsy]

Yah the cabinet isn't the simplest. The long port length needs a double bend. To fit the port around the brace, the speakon connector ends up near the top of the box. The spec calls for an external crossover, and I figure the cab volume is small enough that stuffing the crossover inside might might push the port length too far? There doesn't seem to be enough room for a single passive radiator that can keep up with that driver as well as one would like...I suppose at this design size with that performance, all the usual engineering tradeoffs become more acute

 

[arboleda]

Oof yeah I’m intimidated by that piping.

 

[jsy]

from the specs it looks like you might be able to use 2.5" pvc or abs piping to get the job done? if you take one pipe length and mark it correctly, getting the cuts done shouldn't be too bad. the part i'm questioning is the joins. if you take good care of the cut faces, you can make strong butt joints with adhesive, but will they hold up under that kind of pressure? some math required

alternatively you could try to work it out with pvc couplings. saves you from making angled cuts, and takes the sharp corners out of your vent, but if the coupling is a slip type, you'll have sharp, squared-off ends inside the elbows in your flow path...i'm thinking you could get some bad turbulence and wind noise...anybody else have experience making bent speaker ports?

 

[somebodyelse]

https://www.subwoofer-builder.com/port-flares.htm
The lower third of the page covers bends. The research behind the Flare-it software on the same site is worth a look too.

 

[bluefuzz]

Oof yeah I’m intimidated by that piping.

One could hope that Purifi do a demo build using their own passive radiator.

 

[jsy]

One could hope that Purifi do a demo build using their own passive radiator.

I'm guessing that they had to decide whether to show off an "awesome PR build", or a "best bookshelf ever" build, and went with the latter. Maybe more demos are coming with PRs and a new 8" driver

 

[jsy]

https://www.subwoofer-builder.com/port-flares.htm
The lower third of the page covers bends. The research behind the Flare-it software on the same site is worth a look too.

Thanks sir. I couldn't find those flush interior couplings when I looked quickly before, but clearly somebody's selling them - will search more tonight!

 

[bluefuzz]

I'm guessing that they had to decide whether to show off an "awesome PR build", or a "best bookshelf ever" build, and went with the latter. Maybe more demos are coming with PRs and a new 8" driver

I think it may be a while before we see bigger drivers from them - although I think they've said that they will come at some point. They are still ramping up production of the 6.5" and the 4" isn't out the door yet. However, I wouldn't be surprised to see a build from Troels Gravesen in the near future using these drivers.

I live only 20 km from Purifi's office. It's tempting to go pay them a visit ... ;-)

 

[arboleda]

FWIW I did see that the group buy people were getting passive radiators as well so they clearly exist.

 

[jsy]

FWIW I did see that the group buy people were getting passive radiators as well so they clearly exist.

Yeah, I almost went in on the PRs too, but I don't think just one would provide enough displacement for the 6.5 driver. Taking the port out and adding 2 PRs seemed expensive, and would also need a cab redesign (bigger overall enclosure and mount 2 on the back, or mount two in L/R config and change the bracing)

 

[arboleda]

Now might be as good a time as any for me to ask a dumb question. I see people use passive radiators in lieu of ports and I always wondered how the passive radiator doesn't cancel the sound wave from the active driver. If the active driver goes out and the passive reacts by going in doesn't that cancel? I totally trust that it works but I'd like to understand that better.

 

[koro]

Yeah I agree with you. This won't be a cheap driver and it's not going to be better than everything else, but it looks like an interesting and viable driver with a very good panel of measurements. The surround looks odd but it's an obvious place to introduce asymmetry, similar to the surround extensions in the Peerless NE series woofers.

This driver looks like a joy to work with, with no breakup louder than the pass band, low distortion, extended treble, no cone edge resonance.

I also find it comical that people balk at $500 dollar woofer when it's by far the most important part of your audio system. Not to say I was impressed by the Seas graphene range but I would buy an Ellipticor in a heartbeat.

If anyone was wondering, the copper plug on the Seas magnesium drivers is both a phase plug and to provide cooling.

I’m amazed I had to scroll this far to see someone mention anything at all about this driver’s exceptional cone breakup (seemingly lack of) performance.

Mind you, I know very little about speaker design in general, but I remember it being a big deal in the design of crossovers/choice of tweeters, and one of the deal breakers of fullrange speakers etc. when I used to try to learn at diyforum some couple of years ago.

 

[somebodyelse]

Now might be as good a time as any for me to ask a dumb question. I see people use passive radiators in lieu of ports and I always wondered how the passive radiator doesn't cancel the sound wave from the active driver. If the active driver goes out and the passive reacts by going in doesn't that cancel? I totally trust that it works but I'd like to understand that better.

The same way as the sound from the air moving in the port doesn't cancel on a conventional reflex. The physics is pretty much the same.

 

[bluefuzz]

FWIW I did see that the group buy people were getting passive radiators as well so they clearly exist.

Yes, the 6.5" drivers and 6.5" PRs are shipping but the 4" drivers are not available yet.

 

[617]

Now might be as good a time as any for me to ask a dumb question. I see people use passive radiators in lieu of ports and I always wondered how the passive radiator doesn't cancel the sound wave from the active driver. If the active driver goes out and the passive reacts by going in doesn't that cancel? I totally trust that it works but I'd like to understand that better.

The pr doesn't go in when the driver goes out, it's not affected by the suction.. it is a tuned resonator which hums along at certain low frequencies and not others.

Your intuition about the air in the speaker acting as a sort of spring acting on the woofer cone surfaces is not totally incorrect, but nowadays woofer magnets are super powerful. The PR is quite stiff.

 

[HammerSandwich]

Now might be as good a time as any for me to ask a dumb question. I see people use passive radiators in lieu of ports and I always wondered how the passive radiator doesn't cancel the sound wave from the active driver. If the active driver goes out and the passive reacts by going in doesn't that cancel? I totally trust that it works but I'd like to understand that better.

Here is an article that might help. The pendulums provide a nice visual analogy.

 

[mitchco]

Purifi's SPK4 demo kit I reviewed sounded and measured great in the low frequencies. Maybe a simpler cab construction...

 

[arboleda]

The pr doesn't go in when the driver goes out, it's not affected by the suction.. it is a tuned resonator which hums along at certain low frequencies and not others.

Your intuition about the air in the speaker acting as a sort of spring acting on the woofer cone surfaces is not totally incorrect, but nowadays woofer magnets are super powerful. The PR is quite stiff.

that makes sense. I was thinking of it as a closed spring like effect. The resonance makes sense. Thanks!