And a 10 - or bigger - even better
Being useable on an OB ... dramatically improving the ~directivity as implemented~ of these SOTA drivers, hence the most effective way of minimising room acoustics
Purifi business case support: customers would almost certainly want two drivers per side .. AND an 8 inch for for the upper bass-lower mids
Imo, would be the marriage of SOTA drivers and SOTA speaker design. I've never read a review which wasn't super impressed eg
"I had heard "not everyone likes the dipole sound ... but ..
I had a chance to visit Linkwitzlab and hear the LX521 and LXMini this weekend. : audiophile
LX521 Linkwitz Lab Open Baffle 4-Way Kit
10-12" Purifi with super low distortion for 20-200Hz region and hopefully >90dB@8ohm would be sweet. Would be nice if they could reverse the trick they did with coil and did it with magnet (kind of like new Dayton Epique) if it's possible.
So how does the 6.5 midrange (PTT6.5M08-NFA-01) achieve 7 - 10 dB lower 2nd and 3rd harmonic compared to PTT6.5X04-NFA-01? from 200 Hz up? Shorter coil means lower eddy currents, lower inductance and inductance variation, but one should think all of these were well taken care of in the X design? Improvement is actually more then what is seen in short stroke versions of more traditional drivers (Seas, Satori, Scan Speak coming to mind).
And is the 3-5 dB distortion improvement of the aluminum cone (NAA) due to less cone flexing or were there tweaks in the motor and suspension that made this possible?
The amount of "abuse" this driver can take is really quite something. I redesigned a crossover for my Bliesma T25B6 and Purifi PTT6.5W04-01 bookshelf (see earlier post). In an attempt to diagnose some clipping issue with the high, I hooked up a 1250w Crown Dci2-1250 class D amp. The absolute amount of power of the amp is not that relevant, but this amp has a crazy ability to control any woofer. The Purifi is able to fill a 400 sq ft room with loud and tight bass no one would even believe it is just 6.5". So much so that my ears were tired after a while.
I am still using the same cabinet with 2x 8x5" SB PR that I built described earlier, but with a new baffle and new crossover.
I am still using the same cabinet with 2x 8x5" SB PR that I built described earlier, but with a new baffle and new crossover.
Yes. It works and sounds good to my ears. There were also measurements posted earlier in this thread, I think back in May 2020, and they look good. I don't know if they work better than the official Purifi ones but they are certainly cheaper!
The cons, they are big, and 2 of them are needed, and using with the Purifi means around 20-22L cabinet volume and there isn't really any space to put them other than on the side panels. That might limit the design choices.
The official ones are small enough that they fit at the back like Normal did.
Hi capslock, I can see that the front page graphs for the M version go to 10dB at the bottom and 0 dB for the X version - this makes it harder to compare (the rationale was to keep the same aspect ratio of the graphs, hence the shift on the Y axis). To me it looks like the distortion is roughly the same. The LF increase begins slightly sooner on the M due to the stiffer suspension (is my guess). Good question about the eddy currents. The hysteresis distortion (as seen in the current distortion) is pretty much the same as on the X version despite the lower inductance of the M (fewer turns on the coil). There are more windings in the gap for the shorter M version (hence the higher Bl and sensitivity) so this brings the eddy currents up again.
I think you are right that the stiffer alu cone with less flexing in the NAA helps reduce disortion. It uses the same motor as the NFA/paper version.
Cheers,
Lars
Hi Piotr, good news is that a paper version of our coming 8" will probably meet your 90dB/W (aka 8 ohms) sensitivity and it has 10mm linear stroke and an Sd of 233cm2 so can move quite some air. I am polishing the design in simulations currently.
Why would you prefer to linearise Bl using the gap/magnet rather than our variable winding pitch method? There is more to it than Bl(x) since we also need to keep inductance independent of position.
Cheers,
Lars
Hi, from my experience and simulations then PTT6.5X and 2xPR works best in a rather small box 10-12L - here a port would be extremely long. If the volume is too big for a PR then the PR mass to go down and the PR free field resonance goes up - this is where the notch in the response is placed and this notch eats away a chunk of the bass extension.
Cheers,
Lars
Lars,
Interesting! IIRC, most of us who has built PR box have it too large then. 12L will have the issue of trying to place the PR to avoid leakage. Time to do some drawing and make some saw dust this winter break. Appreciate your advise.
hi, can you share some more info regarding this driver? not asking for full T/S parameters set
but maybe approximate (+-1liter) net. volume of sealed enclosure to get Qtc ~0,7 and if you have this data: -3dB freq. for that volume.i know it's pretty early for this kind of question
but it can shed some insight on usability scenarios for this driver.regards,
ML
hi, can you share some more info regarding this driver? not asking for full T/S parameters set
i know it's pretty early for this kind of question
regards,
ML
hi ML,
This is of course extremely preliminary. The prototype has currently fs at 37Hz and Qts of 0.45 so actually more suited for sealed than reflex. Vas is 36L. From a quick back of a napkin then Qb=0.7 is reached at around 25L box volume and this gives fb=F3=58Hz -maybe not as low but quite good for a 25L sealed. We are looking into making the suspension a bit softer which brings fs and Qts down to better work in reflex. For a sealed, this would reduce the box volume even further and F3 will not change (smaller box just needs to make up for the reduced suspension stiffness.
Cheers,
Lars
Hi Paul,
That was in audio science review. Esteemed member dlr initially wanted to go with a sealed cabinet but in the end they went with 1/2 cu foot with the SB 5x8 PR; because they wanted extension down to 40Hz, and knows well Amirm likes big bass.
Putting any woofer into a small box and boosting the sub-bass (via EQ or Linkwitz transform or DSP etc) would quickly run put of amplifier power and/or excursion and potentially into distortion issues
This midwoofer is a very flexible woofer; it’s strength; apart from buttery smooth frequency response and class leading distortion figures; is that it can be placed into smaller cabinets that usual. The tradeoff for that is slightly lower sensitivity; but in the age of Bruno’s UcD, nCore and Eigentakt; we’ve had a decade of light clean high power. Anyway, I digress;
It CAN be used in a variety of alignments.
I wonder if you have simulated it with some modern programs like 1. Vituixcad 2. Unibox 3. or Scan-Speak Toolbox or a convenient phone App like Speaker Box Lite.
If you haven’t had a chance here’s a few alignments that work.
A) PR: 1/2 cu foot with SB 5x8 PR
B) 2 PR:10-12 L with dual SB 5x8 PR or PTT 6.5 PR; smallest box with best extension, but highest cost due to added PRs
C) Sealed: 7L (or less) (F3/F6/F10 of 80/57/40) in 2pi; will run out of excursion if you EQ the low end, but will not if you don’t, even with 100W input.
D) 20L bass reflex tuned to 36Hz using 2.5” port x 8” port; be careful of long port (port chuffing noises, fitting it into cabinet)- use advanced ports like flared ports or Augerports and/or downfiring port to fit it into height of cabinet.
None of these take into account baffle step losses, nor room effects below the Schroeder frequencies, and blending into a subwoofer is challenging without measurement equipment or a great ear. If this is double dutch (gibberish) to you; ignore this paragraph and take from this post what makes sense to you.
Have you already bought this woofer? If so; what have you got to lose?
So simulate (theorise)
Build, test (empirical method)
Play and enjoy (if you don’t enjoy- come back and ask!)
Best regards.
That was in audio science review. Esteemed member dlr initially wanted to go with a sealed cabinet but in the end they went with 1/2 cu foot with the SB 5x8 PR; because they wanted extension down to 40Hz, and knows well Amirm likes big bass.
Putting any woofer into a small box and boosting the sub-bass (via EQ or Linkwitz transform or DSP etc) would quickly run put of amplifier power and/or excursion and potentially into distortion issues
This midwoofer is a very flexible woofer; it’s strength; apart from buttery smooth frequency response and class leading distortion figures; is that it can be placed into smaller cabinets that usual. The tradeoff for that is slightly lower sensitivity; but in the age of Bruno’s UcD, nCore and Eigentakt; we’ve had a decade of light clean high power. Anyway, I digress;
It CAN be used in a variety of alignments.
I wonder if you have simulated it with some modern programs like 1. Vituixcad 2. Unibox 3. or Scan-Speak Toolbox or a convenient phone App like Speaker Box Lite.
If you haven’t had a chance here’s a few alignments that work.
A) PR: 1/2 cu foot with SB 5x8 PR
B) 2 PR:10-12 L with dual SB 5x8 PR or PTT 6.5 PR; smallest box with best extension, but highest cost due to added PRs
C) Sealed: 7L (or less) (F3/F6/F10 of 80/57/40) in 2pi; will run out of excursion if you EQ the low end, but will not if you don’t, even with 100W input.
D) 20L bass reflex tuned to 36Hz using 2.5” port x 8” port; be careful of long port (port chuffing noises, fitting it into cabinet)- use advanced ports like flared ports or Augerports and/or downfiring port to fit it into height of cabinet.
None of these take into account baffle step losses, nor room effects below the Schroeder frequencies, and blending into a subwoofer is challenging without measurement equipment or a great ear. If this is double dutch (gibberish) to you; ignore this paragraph and take from this post what makes sense to you.
Have you already bought this woofer? If so; what have you got to lose?
So simulate (theorise)
Build, test (empirical method)
Play and enjoy (if you don’t enjoy- come back and ask!)
Best regards.
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A vent lowers driver excursion near the vent tuning, of course. Do you mean a woofer in very small sealed box?
That may have to do with the nonlinear relationship of pressure and volume. DDF mentioned that on a different forum, but I have the impression they analyzed that problem from the wrong end. The usual assumption of adiabatic compression in acoustics ties Pressure*Volume^1.4 to a constant. Box stuffing will lower the exponent slightly, but I haven't enough data to estimate that.
The pressure imbalance over the cone surface presents a nonlinear restoring force. There are several articles from Purifi that assign nonlinear Kms a lower priority, with a simple demo modelling it. If you have to pick a nonlinearity, nonlinear Kms at LF is relatively mild. In any case, you can make the box a little bigger and generously fill the box to reduce that nonlinearity.
That may have to do with the nonlinear relationship of pressure and volume. DDF mentioned that on a different forum, but I have the impression they analyzed that problem from the wrong end. The usual assumption of adiabatic compression in acoustics ties Pressure*Volume^1.4 to a constant. Box stuffing will lower the exponent slightly, but I haven't enough data to estimate that.
The pressure imbalance over the cone surface presents a nonlinear restoring force. There are several articles from Purifi that assign nonlinear Kms a lower priority, with a simple demo modelling it. If you have to pick a nonlinearity, nonlinear Kms at LF is relatively mild. In any case, you can make the box a little bigger and generously fill the box to reduce that nonlinearity.
Thanks for the responses. When I saw the audio science review, I understood it to be saying there was some intrinsic problem using the PTT6.5 sealed (regardless of added EQ). It sounds like I misunderstood.
I use Unibox for simulation and ARTA for measuring. My plan was to use alignment C with no EQ, powered via my 80W amp. I plan to use CSS SDX12 subs powered by ICEPower modules and DSP of some sort, crossing them to match the PTT6.5 sealed roll-off.
I use Unibox for simulation and ARTA for measuring. My plan was to use alignment C with no EQ, powered via my 80W amp. I plan to use CSS SDX12 subs powered by ICEPower modules and DSP of some sort, crossing them to match the PTT6.5 sealed roll-off.
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From an alignment point of view, you're good to go then.
The only reason why most people aren't going with sealed is that, well frankly, you don't need a mid-woofer like the PTT6.5X with 10mm excursion.
Jeff Bagby's Woofer Box and Circuit Designer is excellent.
Model 80W into with your small 7L box, insert a a HP filter 60-120Hz LR2 and see what happens- I don't think you'll get close to 10mm excursion.
Something like the regular W model will suffice (and you get slightly higher sensitivity to boot)
But it's your design. Have fun!
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I think the original PTT6.5X is subject to "compression distortion" in a sealed alignment, as is any high power driver with high x-max in a small sealed box. This is not distortion caused by the driver but from the internal pressure inside the box forcing back against the drivers own motor and suspension. I don't know much about the issue, and do not know of its audibility. I would assume its only relevant to the lower octaves (and subsequent IMD), and if you high passed the driver, you could probably forget about it.