I think with multiple drivers they still have a great product. If you look at the SEAS Excel Line, the Scanspeak illuminator or SB Satori, they all have distortion levels of around -40 to -45 dB. Which is already incredible. The purifi driver goes towards distortion levels of -60dB!
Doubling the amount of drivers would only decrease distortion by 6dB. You would need 4+ drivers for the same result, which is obviously much more expensive. And more drivers give more problems than you might think in the first place. They also create off axis problems and size problems.
Sure there is better drivers for bass, but that is not what the driver is aimed at. The driver is meant as a midwoofer with some bass extension. It would be an ideal candidate for a high end two-way system.
To quote myself from other forum regarding Purifi:
And:
It models reasonably well in volume of 15 liters and tuned to 35Hz.
https://i.postimg.cc/KzWH0hMs/image.gif
Port resonance problem can be seen and while it looks severe, it can be absorbed or mitigated to some extent by placing the vent on the back side. Other problem is port noise and at 18W when port diameter is 50mm and length is 26.7cm with two flares it looks like this.
https://i.postimg.cc/k4wSxW2n/image.gif
For loudspeakers that i want clean bass from i keep port air speed bellow 14ms. Lets say that at 17m/s it becomes audible, and that you really don't want to go above 26m/s then maximum power you can let through these woofers is 39Watts. All this happens at 60% of Xmax, over that and chuffing becomes serious distortion source so the point of low distortion woofer with 10mm Xmax is lost.
If we make the port larger, let's say 68mm, to minimize port air speed, port resonance goes down to around 320Hz and good luck mitigating that.
https://i.postimg.cc/8zRLp7hm/68.gif
Again, the port induced distortion is too large to be neglected in my opinion.
I'd say that passive radiators should be used with these woofers or closed cabinets with appropriate low frequency boost. Then there are some advantages of low distortion that can be put to good use. But it would have to be quite a boost to get these results in closed cabinets (6-8dB boost at 40Hz actually). Distortion levels rise as well.
Thing that really puts me off for two way is 30 grams Mms, more than double from Wavecor, Revelator, Satori, Seas Nextel, Excel and Prestige woofers. Although Cms is 1.3 i am doubtful how would it sound. I guess that we'll just have to wait and see.
These are distortion figures of one 8 ohm Satori that is doing 88dB at 2.83V/1m.
https://hificompass.com/en/speakers/measurements/satori/satori-mw16p-8.
Two Satori MW16P-8 in parallel will achieve 94dB at 2.83V/1m. The level Purifi is measured at.
They start to look cheap at 130 euros/piece.
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Here is a review with measurements.
Purifi Audio PTT6.5W04-01A midwoofer | HiFiCompass
There is pricing at the bottom of the page. Looks like they will be going for $390.00 a piece. So not cheap but according to hificompass they are the cats meow. They will be setting up a web store some time this month if they haven't already.
They look like a good match to the peerless DA25TX00-08 in a two way setup, possibly with a passive radiator.
Purifi Audio PTT6.5W04-01A midwoofer | HiFiCompass
There is pricing at the bottom of the page. Looks like they will be going for $390.00 a piece. So not cheap but according to hificompass they are the cats meow. They will be setting up a web store some time this month if they haven't already.
They look like a good match to the peerless DA25TX00-08 in a two way setup, possibly with a passive radiator.
Fusion amplifiers are easily available and make DSP solutions very approachable for many people.
Sure you won't have full control over the digital signal path (for things like directivity control, limiters for increased bass extention), but it'd still be a DSP solution.
I'm currently working on a DSP solution with this driver starting off with a fusion amp, but will later move towards my own DSP + DAC solutions.
Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review by mitchco
Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review - Reviews - Audiophile Style
Purifi PTT6.5 Woofer and 1ET400A Amplifier Technology Review - Reviews - Audiophile Style
Here is a quick comparo of frequency response measured in the same location and 30cm away. I have offset the measurement pairs so it is easier to compare. Purifi SPK4 Demo Kit on top, KEF LS50 on bottom:
Let’s look at the demo speakers step (timing) response. What we are looking for is the “right triangle” shape which denotes an ideal speaker’s minimum phase response:
New driver, awesome Xmax for a 4 inch: PTT4.0W04-01A
TS parameters are not complete, sadly.
A missing parameter is QMS. I put 6.0 as imaginary QMS and get a BL factor of ~3.24. Which is much lower than that of PTT6.5W04-01A. Considering a similar size magnet and xmax, I assume this driver uses a 2 layer voice coil?
TS parameters are not complete, sadly.
A missing parameter is QMS. I put 6.0 as imaginary QMS and get a BL factor of ~3.24. Which is much lower than that of PTT6.5W04-01A. Considering a similar size magnet and xmax, I assume this driver uses a 2 layer voice coil?
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Thanks Maty amazing review lowest distortion sound concert volume he has heard for size ! How loud? We always end up playing insanely loud due to the lack of distortion (my ears become the limit). The woofer handles 350W IEC long term and survives bottoming (which of course sounds bad). Actually, the 100 hour power tested units have never had damages to the soft parts which is quite unusual (our special surround works like a dream to stabilize the motion). You have +-14mm of mechanical stroke and with the lowered port tuning to 30Hz it takes quite a bit to bottom it. So just fire it up and ease back if you hear bottoming – mostly because it then suddenly sounds bad, it’s not harmful.”
Wow
New driver, awesome Xmax for a 4 inch: PTT4.0W04-01A
TS parameters are not complete, sadly.
A missing parameter is QMS. I put 6.0 as imaginary QMS and get a BL factor of ~3.24. Which is much lower than that of PTT6.5W04-01A. Considering a similar size magnet and xmax, I assume this driver uses a 2 layer voice coil?
IIRC 4 layer
My interpretation:
- It is symmetric (they are not the first to do that) so at least the distorsion pattern is symmetric on the to half waves.
- Part of this is due to the variation in total surface being better controlled. For instance, if a surround is rounded mostly towards the outside, its surface area expands quite a bit while the cone is moving out, but it does less so while the cone is moving in, causing also a difference in total pressure.
- They have more material in the folds, so there is more material that can be "unfolded" before it starts to stretch, significantly reducing distorsions due to elasticity of the surround material "pulling" the cone back towards the midle position
Such a 2 way, with a "visaton petit orgue"-like active subwoofer would definitely kick a**.
i just read the article by mitchco.
Speaker details here https://purifi-audio.com/wp-content/uploads/2019/12/SPK5-App-Note.pdf
The speaker is pretty basic BR 2-way with LR4@3,2kHz xo. BR tuning is low around 30Hz. Tweeter is Mundorf AMT that costs 240€.
Mitch didn't show distortion or directivity curves but it really must be good for a single 6,5" 2-way Anyway it needs a subwoofer for full range sound. The woofer has moderate cone resonance around 3,5kHz and typcal directivity characteristics.
Purify amp is first class no doubt!
Speaker details here https://purifi-audio.com/wp-content/uploads/2019/12/SPK5-App-Note.pdf
The speaker is pretty basic BR 2-way with LR4@3,2kHz xo. BR tuning is low around 30Hz. Tweeter is Mundorf AMT that costs 240€.
Mitch didn't show distortion or directivity curves but it really must be good for a single 6,5" 2-way Anyway it needs a subwoofer for full range sound. The woofer has moderate cone resonance around 3,5kHz and typcal directivity characteristics.
Purify amp is first class no doubt!
It's exactly my plan. I'm currently using a Scan Speak D3004/6640 in a waveguide (very similar to the SEAS DXT tweeters waveguide).
Maybe I'll make a motional feedback sub for the frequencies below 100Hz, but that's a project for in the far future (my wallet still hurts from these and the scanspeak tweeters).
Hopefully I can get acces to the CNC of my university soon
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