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Purifi PTT6.5W04-01A 6.5" midwoofer

Audiocrusader

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No offence, but that's a mind-numbingly self-contradicting sentence. A man of science should not accept anything at face value.

I have no idea why you feel the need to make an enemy out of anyone who disagrees with you. It's juvenile and completely counterproductive :rolleyes:

I've tried to poke you gently with a stick of common decency/sense several times in this thread, but every time you just seem to pretend it didn't happen.

Haven't got a single person on my ignore list yet, but you are awfully close at becoming my first... just saying (not that you probably care).


Ahh so I get personally attacked by getting called stupid, and I counter with the scientifically proven fact that hearing degrades with age, and I'm the bad guy. Just another example that BS is far more prized around here than scientific facts.
 

watchnerd

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Ahh so I get personally attacked by getting called stupid, and I counter with the scientifically proven fact that hearing degrades with age, and I'm the bad guy. Just another example that BS is far more prized around here than scientific facts.

Can you point to a study that shows that the ability to detect distortion at 1 kHz degrades with age?

After all, we're not talking about tweeters here.
 

Audiocrusader

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Can you point to a study that shows that the ability to detect distortion at 1 kHz degrades with age?

After all, we're not talking about tweeters here.

Proof that most of you are in the wrong hobby. Do something useful and knit me a blanket.

PresbycusisCurves_gif.gif
 

watchnerd

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Proof that most of you are in the wrong hobby. Do something useful and knit me a blanket.

View attachment 38135

a) That doesn't address distortion

b) In the mid-woofer range, age-loss is significantly less

c) We have gain...you can turn up the volume

d) This probably with test tones, not music

e) Distortion detection is prone to masking with music

f) By your argument, nobody over age 20 should listen to audio, which would be both bad for the industry and sad

In conclusion, that graph is pretty irrelevant to detecting woofer distortion at 1 kHz, especially with music.
 

Audiocrusader

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Another thing is unless you measure the driver yourself, you're taking any data at face value. Because you have no way of know for 100% sure that any independent testing is accurate either. Anyone who would put fraudulent data on their datasheet could also be paying off any independent lab to get positive results as well. Knowing this how could anyone sleep at night.
 

Audiocrusader

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Yes, and samples, vary, too.

What's your point?


No data and nobody can be trusted anyways. So just move on and start a thread on why an objectivist listens to vinyl as a source in 2019. And the scientific reason why. That's an oxymoron if I've ever heard one. It would be like a flat earther hanging out on a NASA forum.
 

Krusty09

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Hey,

Sounds like a great product . Do you know if this guy the guy who is gonna review them help them out in any way to make such a great speaker or is this not the same guy. Just Wondering.

Vance Dickason
Audio Consultation Services And Loudspeaker Design
 

Audiocrusader

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Hey,

Sounds like a great product . Do you know if this guy the guy who is gonna review them help them out in any way to make such a great speaker or is this not the same guy. Just Wondering.

Vance Dickason
Audio Consultation Services And Loudspeaker Design

Vance Dickason is a driver reviewer at voice coil. And one of the most legendary speaker designers out there. He wrote the bible for loudspeaker design back in the 80's.

https://www.parts-express.com/loudspeaker-design-cookbook-7th-edition-book--500-035

I've been a Voice Coil and Audio Xpress subscriber for 25 years now. The best publications in the industry. But no Vance is not part of the Purifi team.
 

Julf

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I've been a Voice Coil and Audio Xpress subscriber for 25 years now. The best publications in the industry. But no Vance is not part of the Purifi team.

It was pretty decent at one point, but really gone downhill lately - way too many infomercials.
 

Julf

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Wombat

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No data and nobody can be trusted anyways. So just move on and start a thread on why an objectivist listens to vinyl as a source in 2019. And the scientific reason why. That's an oxymoron if I've ever heard one. It would be like a flat earther hanging out on a NASA forum.

More thought bubbles.
 

Wombat

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briskly

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Most of what Purifi's white paper describes is the nonlinearity associated with inductance. A more detailed problem statement from an old JBL patent application (US patent 6774510)

Another problem is that the magnet in the transducer creates a static magnetic field, and this static field can be modulated by the changing magnetic field in the coil generated by the current in the voice coil. This phenomenon has been discussed by W. J. Cunningham, an article entitled “Non-Linear Distortion in Dynamic Loudspeakers due to Magnetic Effects,” J. Acoust. Soc. Am., Vol. 21, pp 207-207 (1949 May); and J. R. Gilliom, entitled “Distortion in Dynamic Loudspeakers due to Modulation of the Permanent Field.” presented at the 42nd Convention of the Audio Engineering Society, Los Angeles, Calif., 1972 May 2-5. . . .

That is, as current is passed through the dual coils, the dual coils move within the static magnetic field. At the same time, the current passing through the dual coils also creates a magnetic field around the wire, as a result, the magnetic field around the wire moves within the static magnetic field of the magnet, thus modulating it. The amount of modulation is substantially related to the number of turns in the coil and current being applied, or the total Amp-tuns. Modulation of the static field can also be viewed as a “global” modulation effect that is asymmetrical and in turn generates second harmonic distortion. Depending on the saturation level of the steel surrounding the magnetic gap, the moving field of the voice coil also creates a “local” modulation effect of the magnetic field within the steel surrounding the magnetic gaps so that symmetrical or third harmonic distortion is created in the output signal.

As the coil moves, the quantity of iron near the coil will change. Thus, the effective inductance is excursion dependent. An additional factor is that the penetration of the induced currents into the various metals is limited at higher frequencies, a skin effect. The effective inductance is also frequency-dependent. Inductance related distortion is neither newly discovered nor obscure. The techniques used to reduce these distortions are commonly used in upscale drivers. For instance, there is a copper ring visible behind the Purifi VC. Selective saturation of iron components may also be used to minimize the modulation of iron permeability by electric current.

I have not observed surround distortions beyond the usual concerns of cone edge-surround interaction, as well as its nonlinear stiffness with displacement. But I believe they are referring to Sd modulation since they refer to low-frequency issues. Traditionally, this was not deemed a key concern for loudspeakers. I don't know on what scale this would occur that it is usually disregarded.

Another thing: the Kms curve is parabolic, which suggests a linear roll spider. The woofer "soft clips" low-frequency content at moderate and high excursions by a steady increase in the suspension stiffness. Contrast the usual characteristic of a progressive roll spider, which maintains little change of stiffness over moderate excursions and rapidly stiffens beyond some specified displacement. This is the preferred trait of long-throw woofers, so I wonder why not here?
 

jhaider

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Ok so the end results of the design are meaningless, and the only thing that matters is if the parts used pass the criteria of your "audiophile buzzlist"?

Neo is lighter, more energy dense, more compact (i.e. fewer reflections from the motor structure back onto the cone), and self-shielding. Those are real advantages, not part of any "audiophile buzzlist."

While at $150 each neo may be too much to ask in a 6.5" woofer (though SB Acoustics, B&C and others manage), $400 each is a different stratosphere. ScanSpeak 6.5" woofers are clay ring magnets up to about $200 and neo structures from $300+. Revel uses clay disk magnets through Performa3 Be and neo magnets in Ultima.

I know of no performance drawbacks from using a lighter smaller magnet of a given strength. The practical caveat to neo is potential exposure to commodity price shocks. About a decade ago the Chinese artificially cut off supply, and neo costs temporarily skyrocketed. KEF for instance used to use a lot of neo. Even the midwoofers of their HTIB eggs had compact neo motors.Their current lineup, except Reference, uses all clay ring magnets for midrange and woofer (neo for tweeter).
 

617

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Neo is lighter, more energy dense, more compact (i.e. fewer reflections from the motor structure back onto the cone), and self-shielding. Those are real advantages, not part of any "audiophile buzzlist."

While at $150 each neo may be too much to ask in a 6.5" woofer (though SB Acoustics, B&C and others manage), $400 each is a different stratosphere. ScanSpeak 6.5" woofers are clay ring magnets up to about $200 and neo structures from $300+. Revel uses clay disk magnets through Performa3 Be and neo magnets in Ultima.

I know of no performance drawbacks from using a lighter smaller magnet of a given strength. The practical caveat to neo is potential exposure to commodity price shocks. About a decade ago the Chinese artificially cut off supply, and neo costs temporarily skyrocketed. KEF for instance used to use a lot of neo. Even the midwoofers of their HTIB eggs had compact neo motors.Their current lineup, except Reference, uses all clay ring magnets for midrange and woofer (neo for tweeter).

Yes, and Vifa's 'ne' line was meant to be an affordable next generation driver line, but price increases have made it a lot less affordable. Great drivers for the money, still.

We are seeing more and more Neo tweeters, the demand from car audio probably drives that.
 
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