PURIFI finally did a fully purified passive speaker design! The SPK 16 prototype is here - with a PTT tweeter

[Old_School_Brad]

That’s a cool demo but doesn’t their surround design address a different issue? IMD due to linear movement of a cone is not something you can fix. As far as I understand their surround addresses distortion cause by the cone surface area changing as it moves.

Well, IMD is affected by changes in the surround area due to cone excursion. As the cone moves, particularly during larger excursions, the mechanical behavior of the surround can become non-linear. This can introduce additional distortion products when multiple frequencies are played simultaneously, increasing IMD. A surround that maintains linear behavior during excursion will minimize IMD.

 

[Matt_Holland]

Well, IMD is affected by changes in the surround area due to cone excursion. As the cone moves, particularly during larger excursions, the mechanical behavior of the surround can become non-linear. This can introduce additional distortion products when multiple frequencies are played simultaneously, increasing IMD. A surround that maintains linear behavior during excursion will minimize IMD.

I agree with all of that.
The aforementioned demo would still introduce IMD (Doppler effect), just with lower amounts of other non-linear distortion compared to more typical driver designs.

 

[Penelinfi]

That’s a cool demo but doesn’t their surround design address a different issue? IMD due to linear movement of a cone is not something you can fix. As far as I understand their surround addresses distortion cause by the cone surface area changing as it moves.

At 0.5Hz, it's hardly doppler distortion as the cone is not moving fast. But it does show that the sound doesn't change due to radiation area changes.
Can you hear that on a regular woofer at 0.5Hz? Idk, has anyone tried?

 

[Sokel]

Purifi and marketing bs are not really two terms that make sense together to me.

Hmm...

(link)

 

[Chrise36]

There seems to be some difference regarding IMD but not so significant:

SB Acoustics SB17CAC35-4 6 Inch Ceramic Midwoofer Review

SB Acoustics SB17CAC35-4 6 Inch Ceramic Midwoofer Review

www.erinsaudiocorner.com

Purifi Audio PTT6.5W04-01A 6.5 Inch Woofer Review

Purifi Audio PTT6.5W04-01A 6.5 Inch Woofer Review

www.erinsaudiocorner.com

 

[Penelinfi]

On the SB I do see one graph showing bunching of multitone around the frequency that corresponds to surround-coil distance. But it's still quite low in level
It's interesting how despite some of the asymmetry measured on the SB, there's still great performance in many areas that complete speakers get measured. Just doesn't do the high excursion as well as the Purifi

 

[Matt_Holland]

At 0.5Hz, it's hardly doppler distortion as the cone is not moving fast. But it does show that the sound doesn't change due to radiation area changes.
Can you hear that on a regular woofer at 0.5Hz? Idk, has anyone tried?

Very good point

 

[Matias]

There are cheaper options?!? This is the first really powerful amp I've seen under $1000, pretty amazing. Their other amps though, what is the use case? Like 2x500, 2x250, 2x125? I don't get that, especially as the front LCR should have the same power.

See here.

Buckeye Amps

Buckeye Amps utilizes the most advanced audio amplifier technologies available. Authorized seller for Hypex and Purifi Class D amplifiers. Based in the US. Free shipping and worldwide service!

www.buckeyeamp.com

 

[WTW]

So, anything news about ptt33 ? Now is 2024/12 , but we still can't buy a "ultra low distortion purifi speaker tweeter" .

 

[FERCSA]

So, anything news about ptt33 ? Now is 2024/12 , but we still can't buy a "ultra low distortion purifi speaker tweeter" .

If I remember correctly Lars told us the design is already frozen and they're prepping for production.
(speculation below)
Probably average joe not get it this year only those on the waiting list. I'm sure the first pictures and reviews will come after those people got theirs. There is non atm.
My personal expectations is we'll get something similar to sb26cdc with better specs and directivity.

 

[WTW]

如果我没记错的话，拉尔斯告诉我们设计已经完成，他们正在准备生产。
（以下为推测）
今年可能普通人买不到，只有那些在等待名单上的人才能买到。我相信那些人拿到后，第一批照片和评论就会出现。目前还没有。
我个人的期望是我们将获得类似于 sb26cdc 的产品，但具有更好的规格和方向性。

cool , i hope they can open source the wave guide for ptt 6.5/8.0.

 

[IPunchCholla]

Axis info? Do you mean off axis? On axis is provided, but the tech here related to the surround is mostly for managing distortion. If you want off axis data head to erins audio corner, he reviewed some of their drivers and dispersion is just fine for them.

Purifi and marketing bs are not really two terms that make sense together to me. They're very transparent about their products and development behind them, they have articles in their blog section that go into detail on various loudspeaker and audio reproduction fundamentals. None of it is marketing BS, it's all well represented and executed science. I beieve

If you want an example of marketing BS Focal has you covered. They constantly come out with new cone materials touting all sorts of things, only to end up delivering pretty sub par performance a lot of the time. I could understand criticism against purifi if they were doing the same, but they're not. Their products are offering very good performance and the data clearly shows their engineering is sound.

Honestly, I was responding to the unlabeled graphs in the link of the post I responded to. There are literally no numbers on them, and the terms are posited as relative with no values given.

 

[iGPU]

Claus told me that the new PTT1.3T04-HAG-01 tweeter will be available in early 2025. He showed me the pre-release datasheet but asked that I not publicly share it. The specs look really good. The datasheet conveniently provides an example crossover for the tweeter.

 

[RickS]

Claus told me that the new PTT1.3T04-HAG-01 tweeter will be available in early 2025. He showed me the pre-release datasheet but asked that I not publicly share it. The specs look really good. The datasheet conveniently provides an example crossover for the tweeter.

Thanks for the update.

Guess Santa is not bringing them for Christmas! Maybe a nice note with a better availability date?

 

[Cbdb2]

At 0.5Hz, it's hardly doppler distortion as the cone is not moving fast. But it does show that the sound doesn't change due to radiation area changes.
Can you hear that on a regular woofer at 0.5Hz? Idk, has anyone tried?

Its still doppler. The difference is in the way we percieve it. This is frequency modulation (FM). At low modulation freqs. we hear it as vibrato, a pitch modulation, at higher modulation freqs we start to hear other freqs as in distortion.

From Wikipedia: :FM synthesis can create both harmonic and inharmonic sounds. To synthesize harmonic sounds, the modulating signal must have a harmonic relationship to the original carrier signal. As the amount of frequency modulation increases, the sound grows progressively complex. Through the use of modulators with frequencies that are non-integer multiples of the carrier signal (i.e. inharmonic), inharmonic bell-like and percussive spectra can be created."

 

[ayane]

Doppler, i.e. FM, is inherent to all drivers simply because of a rather slow speed of sound combined with a comparatively significant (nonzero) driver velocity. For any given frequency, the larger the excursion, the larger the amount of FM that will occur. However, FM is only one mechanism of IMD; there are several other mechanisms, the majority of which arise from complex interactions in the electrodynamics of the driver, which is what Purifi usually refers to when talking about IMD.

One simple example is non-constant Bl(x), which can introduce both harmonic and intermodulation distortion: the cone acceleration (which is what creates the longitudinal pressure wave) is dependent on the motor force. If the flux changes at different points in the excursion, the output of a simple sinusoidal input tone will have harmonic distortion. If, however, the input is more complex, as is always the case in music, then the constituent tones will modulate each other. In a driver with non-constant Bl(x), a high-excustion low-frequency bass tone superimposed with a low-excursion high-frequency tone will result in the higher frequency tone being amplitude modulated depending on the instantaneous cone position, as the sensitivity of the driver is literally changing with position!

This is a difficult problem to solve, but one worth solving, because between FM and AM, AM particularly tends to be the most audible mechanism of IMD.[1] Doppler-style FM and even harmonic distortion (in low frequencies (and very high frequencies)) really aren't a major problem due to their limited audibility and ability to be easily masked by other content.[2] We're far more sensitive in the four octaves between 500 Hz and 8 kHz, especially the middle two octaves, so whatever distortion lands there takes priority during the great comprimises of engineering.

[1] This demo by Purifi comparing AM to FM
[2] Masking in the Human Auditory System