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The REAL Problem of March Audio's Sointuva WG (Review, Measurements and Reinforcements with Klippel device)

Axo1989

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That depends on the degree of narcissism. What really bugs me is the degree of mistrust sometimes is shown here. Everybody is assumed the worst. Gene is bribed by manufacturers, Erin just wants to divert traffic. That's borderline paranoia and creates a toxic environment.
I perceive a degree of that also. It isn't sufficient to outweigh the value of this forum, but I would (and hopefully do) take more care choosing and posting words to that effect.

I'd also say that accusations are often projection, so they cause me to be more circumspect wrt the veracity of a poorly-worded or overstated accusation/inference. I discount the OP somewhat: there is some interesting data that I appreciate, but analysis and inference shows some carelessness.
 
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fluid

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But the IB test I know is consisted of test baffle, driver mounted to it, and baffle wings. And If baffle-motor is resonating and causing problem why is it not seen on the Purifi datasheet?
Most likely because they isolated the driver from the baffle with damping or mounted it via the magnet, or they measured it at an SPL level where the resonance wasn't excited.
 

SDC

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Most likely because they isolated the driver from the baffle with damping or mounted it via the magnet.
So is it industrial standard to mount it via the magnet? That's what I'm questioning.
 

MAB

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Is the cabinet brace between the left and right walls an oak dowel? Does it ring with a characteristic frequency around where you are seeing the distortion? I was just wondering, since I have always thought these type of braces ring.

I measured some random dowels I had lying around the shop, different lengths and diameters. I suspended each with string, and struck them with a soft mallet to try to get the fundamental excited. These are just the dowel in free air, so no idea how this will change when this element is incorporated into the speaker.
1656375932657.png

Any possibility the brace is a problem? Did the extra stuffing you added and harnessing the wire also damp the brace?
 

fluid

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So is it industrial standard to mount it via the magnet? That's what I'm questioning.
Not usually, but most drivers do not have the motor force, excursion and generally low distortion to make the effect so obvious. I did edit the post above to add another reason but on checking they measured at 2.83V which does produce an SPL of about 86dB.
 
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SDC

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Not usually, but most drivers do not have the motor force, excursion and generally low distortion to make the effect so obvious. I did edit the post above to add another reason but on checking they measured at 2.83V which does produce an SPL of about 86dB.

Thanks for all the informations!
 

DualTriode

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Then it should have been in some kind of app note. Not having it means people don't know to deal with it.

I am not saying that it is but this could be entirely by accident, or a series of events leading to a undesired outcome.

Speakers / drivers are most often installed with some kind of gasket and screw fasteners attaching the the assembly to a not so ridged box. The magnet / motor assembly just kind of dangles on the driver frame. 999 times out a 1000 no harm no foul. Most often a hard connection between driver frame and enclosure goes unnoticed.

In this case the machine screws may not have been fully tightened the gasket may not have been fully compressed. Wham bam we have mechanical vibration and perhaps intermittent leaking with noise that appears as distortion in the measurements and we have unhappy clients with feigner pointing all around with a chorus of "It's not my fault".

In my mechanical engineering world this is where I get a phone call and I get on the airplane with my suitcase in hand to go to your town to sort out noise and vibration in your new hospital or research lab.

If you go to linkwitzlab.com you can find Fritz talking about mounting drivers in his Open Baffle speakers and closed boxes.
The Linkwitz method of reducing vibration transfer from the driver to enclosure is to sandwich the driver between the front of the driver and the enclosure with a thick gasket like damping ring made of closed cell neoprene. Then at the back of the driver motor assemble there is another donut ring of closed cell neoprene all held in place with a piece of plywood bracing attached to the enclosure. There is no hard direct mechanical connection between the driver and the enclosure.

This is vibration isolation 101.

Thanks DT
 

fluid

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Doodski

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So is it industrial standard to mount it via the magnet? That's what I'm questioning.
The KEF reference 104.2 and 105.2 with the 107.2 used a non-ferrous coupling rod with threading on each end that went through the woofers to clamp them via the magnet. It was called, "Coupled cavity."
 

SDC

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The KEF reference 104.2 and 105.2 with the 107.2 used a non-ferrous coupling rod with threading on each end that went through the woofers to clamp them via the magnet. It was called, "Coupled cavity."

Yes I know they did that back then, read a thread about how hard it was during that time, but I was questioning infinite baffle frequency measurement included in the datasheet... Not kef white paper.

edit: BTW I love the idea of CLD bracing by Dr.Geddes and kef.
 
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Nuyes

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Is the cabinet brace between the left and right walls an oak dowel? Does it ring with a characteristic frequency around where you are seeing the distortion? I was just wondering, since I have always thought these type of braces ring.

I measured some random dowels I had lying around the shop, different lengths and diameters. I suspended each with string, and struck them with a soft mallet to try to get the fundamental excited. These are just the dowel in free air, so no idea how this will change when this element is incorporated into the speaker.
View attachment 215217
Any possibility the brace is a problem? Did the extra stuffing you added and harnessing the wire also damp the brace?
Thanks for the good tests and comments.
If bracing was the cause of the problem, both speakers should show the same symptoms.
But I couldn't find it.
 
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Nuyes

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1.jpeg


A guest has arrived.

@SDC , Thank you for all of this support.



He sent me these stuff to test on the purify driver.

I've just received four Purifi 6.5" drivers and IRWIN HD clamps, as well as various damping materials for testing.

And soon, measuring baffles made of aluminum will arrive respectively.

I'm very exited.
 
OP
Nuyes

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You are welcome :)

Just to round it out here is a distortion graph from Hificompass at two different SPL's you can see that at the lower one there is a peak of 3rd Harmonic at 380Hz and then at 100dB there is a slight peak of 5th Harmonic at about 420Hz.

https://hificompass.com/en/reviews/purifi-ptt65w08-01b-ptt65x08-nfa-01

View attachment 215218
Thank you for sharing useful information and knowledge.

Here is some material I'd like to add for clarification.


01.png



1. THD, which does not increase proportionally, is rather modest at about 2.82V.









2.You may remember I tested the Sointuva WG with a hermetic one.
It is CNC machined to the same size as Purifi's Passive Radiator with great precision.






02.png






And as a result I can find similar resonances as well.

The problem with the Purifi driver you mentioned is related to the peak of the 3rd harmonic at 380hz.

However, I found that both the second harmonic and the higher harmonic had peaks at a constant ratio.

This is similar to the room mode that occurs in the listening space.


Through simple calculations, we can see that the length of the space that generates the first resonance of about 400 Hz is about 43 cm (16.9 inches).

And, coincidentally, the height of the Sointuva WG is 45cm (17.7inch) according to the manufacturer's specifications.

Considering the thickness of the speaker enclosure, I thought that this could be the room mode resonance due to the internal floor height.

And if this is the resonance caused by the room mode, this resonance also cannot increase linearly with respect to the output.
This is because the internal structure of this speaker itself is not a perfectly rigid wall.

I thought this was a sufficiently possible scenario.

And, this is why I added sound absorbing material inside this speaker.





And below is the measurement data of sample B.
Similarly, it can be found that everything from the second harmonic to the higher order harmonic soars in a similar frequency band.


03.png








If the cause of the THD pointed out in the original article is the 380hz/3rd harmonic inherent to the Purifi driver, it cannot explain this symptom.






------------------------------


@amirm , I'm sorry for tagging you carelessly.

I leave this question because I haven't gotten used to the way this website works yet.

Starting this thread was a huge process for me, and so was the outcome.

So there are some missing steps. Just like in this post.


Is there any way for me to add this to the body of the thread?
I am afraid that all this will evaporate through my hasty action.
 
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amirm

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Is there any way for me to add this to the body of the thread?
Do you mean add it to the original post for the thread? If so, sure, you can just hit edit on that post and cut and paste it. Alternatively just put a link in the original article to this new post. If you have trouble let me know.
 
OP
Nuyes

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Do you mean add it to the original post for the thread? If so, sure, you can just hit edit on that post and cut and paste it. Alternatively just put a link in the original article to this new post. If you have trouble let me know.
Thanks for kind support.
 

DualTriode

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Thank you for sharing useful information and knowledge.

Here is some material I'd like to add for clarification.


View attachment 215257


1. THD, which does not increase proportionally, is rather modest at about 2.82V.









2.You may remember I tested the Sointuva WG with a hermetic one.
It is CNC machined to the same size as Purifi's Passive Radiator with great precision.






View attachment 215259





And as a result I can find similar resonances as well.

The problem with the Purifi driver you mentioned is related to the peak of the 3rd harmonic at 380hz.

However, I found that both the second harmonic and the higher harmonic had peaks at a constant ratio.

This is similar to the room mode that occurs in the listening space.


Through simple calculations, we can see that the length of the space that generates the first resonance of about 400 Hz is about 43 cm (16.9 inches).

And, coincidentally, the height of the Sointuva WG is 45cm (17.7inch) according to the manufacturer's specifications.

Considering the thickness of the speaker enclosure, I thought that this could be the room mode resonance due to the internal floor height.

And if this is the resonance caused by the room mode, this resonance also cannot increase linearly with respect to the output.
This is because the internal structure of this speaker itself is not a perfectly rigid wall.

I thought this was a sufficiently possible scenario.

And, this is why I added sound absorbing material inside this speaker.





And below is the measurement data of sample B.
Similarly, it can be found that everything from the second harmonic to the higher order harmonic soars in a similar frequency band.


View attachment 215258







If the cause of the THD pointed out in the original article is the 380hz/3rd harmonic inherent to the Purifi driver, it cannot explain this symptom.






------------------------------


@amirm , I'm sorry for tagging you carelessly.

I leave this question because I haven't gotten used to the way this website works yet.

Starting this thread was a huge process for me, and so was the outcome.

So there are some missing steps. Just like in this post.


Is there any way for me to add this to the body of the thread?
I am afraid that all this will evaporate through my hasty action.

My interest in this is peaked because I have a pair of Purifi 6.5 inch drivers being delivered in a few days. The plan is a pair of mini sealed 2-way speakers for my test bench.

The place I plan to start is a little break-in / warm up then TS/P testing with a couple of different methods; moving mass and added weight. I will also plot electrical impedance and phase. Mechanical resonance typically shows up in the impedance plots. I will see if I can find a sealed enclosure to also test for box/driver resonance and or reflections.

Edit: I will also test the 6.5 Inch Purifi driver on an open baffle attached with machine screws (nothing fancy) to look for resonance and harmonic distortions.

I will use the tools on my bench APx 555, APx1701, GRAS microphone plus APx500 software with the acoustic test options.

Thanks DT
 
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diddley

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With great interest i've readed the whole thread and one question pops up in my head:
Is Alan manufacturing the speakers himself, or did he outsourced it to another country? you all know what i mean.
 

SDC

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With great interest i've readed the whole thread and one question pops up in my head:
Is Alan manufacturing the speakers himself, or did he outsourced it to another country? you all know what i mean.

He coops with woodmakers near him in Australia.
 
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