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Multi-Way Conventional loudspeakers with crossovers

Purifi Audio by Bruno Putzeys and friends.
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Old 21st September 2019, 05:50 PM   #101
hidjedewitje is offline hidjedewitje  Netherlands
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Originally Posted by Zvu View Post
It is worth that kind of money only if you need that performance in a certain format. If not, using multiple drivers will leave Purify behind for less money. I never understood the ridiculous prices in hi-end audio.
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.
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Old 21st September 2019, 06:38 PM   #102
Zvu is offline Zvu  Serbia
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Quote:
Originally Posted by hidjedewitje View Post
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!.

To quote myself from other forum regarding Purifi:

Quote:
I'm quite reserved about Purifi woofers for now. Few awkward things about those measurements. One of them being at the bottom of the page (figure 6) where 3rd harmonic at 250Hz drops while woofer playing louder. I've seen so far that going from 80dB to 90dB distortion stands still or moves very little but going down in percentage when driver playing louder ? I'll just have to wait some independent measurements because it basicaly means that while 3rd harmonic may rise with level, it doesn't rise for the same amount of dB as amplitude, but less. I also want to see higher resolution for their impedance measurements. At least 0-10 ohms - i see some irregularity at impedance phase but because they wanted us to see the peak of impedance at resonance frequency (who gives a damn) we can't see anything else (possible surround induced and other resonances).
And:

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It models reasonably well in volume of 15 liters and tuned to 35Hz.

Click the image to open in full size.
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.

Click the image to open in full size.
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.

Click the image to open in full size.
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/...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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Last edited by Zvu; 21st September 2019 at 06:55 PM.
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