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

mga2009

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Im not sure you can really make that conclusion from the OPs study. The various variables (stuffing, sealing and driver mounting) were not sufficiently isolated in the testing.
I might have misunderstood something, but I recall reading the OP and saying that those "variables" solved the problem (or at least mitigated it). Please correct me if I am wrong.
 

samysound

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I might have misunderstood something, but I recall reading the OP and saying that those "variables" solved the problem (or at least mitigated it). Please correct me if I am wrong.
Hi, well both speakers were tested in the "as-received" condition (i.e., same amount of stuffing, same leaks). However, only one of the speakers showed the high distortion at 380hz. The speaker that showed the 380hz peak was disassembled, stuffing was added and the drivers were re-installed. Subsequent re-measurement showed the 380hz peak was reduced. It could have just been re-installation of the woofer that improved the 380hz peak issue. Also, other characteristics of the speaker were altered with the additional stuffing, changing the design.
 
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Holmz

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Thanks @Nuyes for this thorough review and saving me from a potential buyer's remorse :p
I've considered the Sointuva and almost pulled the plug before the price bumped, eventually chose the DIY route and plunged head on into the Directiva r1 adventure

The single pair I heard sounded pretty darn good, so i suspect that with improved QC that they should all end up matched.

I was trying to get them with the passive XO outboard/external and using a Neutrik SpeakOn between the XO and box.
Maybe a single 4-pole SpeakOn would mitigate the leaks?
(But silicon would also seal it just fine.)


Hi, can you please post the emails/questions that were actually sent to the manufacturer? That would help with some context and the full picture for the manufacturers email responses you have shared.

The OP did post the main correspondence, and people read them as polite or demeaning depending on how they wanted to read them.
(They looked OK to me.)
 

changer

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However, only one of the speakers showed the high distortion at 380hz. The speaker that showed the 380z peak was disassembled, stuffing was added and the drivers were re-installed. Subsequent re-measurement showed the 380hz peak was reduced. It could have just been re-installation of the woofer that improved the 380hz peak issue.

This is evident. It cannot be the internal height mode, as it must then show in both samples. The height mode can leak through a vent, but usually not through a passive radiator (an alternative to vents to avoid leakage of unwanted frequencies by tuning). There must have been other factors and I agree it could just have been the reassembling that fixed it.

Did I understand you correctly, @Nuyes, that you are considering a room mode as a possible cause atm?
 

samysound

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The single pair I heard sounded pretty darn good, so i suspect that with improved QC that they should all end up matched.

I was trying to get them with the passive XO outboard/external and using a Neutrik SpeakOn between the XO and box.
Maybe a single 4-pole SpeakOn would mitigate the leaks?
(But silicon would also seal it just fine.)




The OP did post the main correspondence, and people read them as polite or demeaning depending on how they wanted to read them.
(They looked OK to me.)
Hi, only the responses from the manufacturer were posted verbatim but not the original inquires sent to instigate those responses. It would be nice to see the inquiries sent from the OP et al. to get context and the full picture since there are some negative connotations in the comments the OP makes about the communications with the manufacturer.
 

Holmz

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Hi, only the responses from the manufacturer were posted verbatim but not the original inquires sent to instigate those responses. It would be nice to see the inquiries sent from the OP et al. to get context and the full picture since there are some negative connotations in the comments the OP makes about the communications with the manufacturer.

Gotcha.

There are also cultural nuances. I am not well versed in Korean, but the Dutch usually come across as abrasive… But it is really a cultural deal where they strive for expedience of dialogue and do not overly super coat the message.

So I am not overly interested in forensic literary or psychological analysis of the correspondence.
It seems like the 1st jump into a kangaroo court preceding where we pick apart every word, phrase and punctuation mark… looking for hidden meaning, tone and intent.

I would just want to know when/if/-&-how March is rolling in the QC .
And I very much admire the work that Nuyes did.

The rest of it is just headed a bit too much towards drama.
 

YSC

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This kind of post is a big problem in this thread. People not reading and comprehending the sequence of events. This is also how the manufacturer has flipped things and claims the poor measurement was a result of speaker tampering/modification.

The OP has made it clear on a number of occassions that measurements were done on speaker as delivered. After not getting anywhere with the manufacturer, he then went about fixing it while carefully documenting the process.
I think I am saying nothing that the op stuffed it before measuring any of the speaker, what I was saying was in the end after all measurement and mod/fixes I remember he did stuff the internal volume so in the end it significantly reduced the internal reflection and that’s it, don’t accuse me of saying the op did the mod before
 
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Nuyes

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Hi, well both speakers were tested in the "as-received" condition (i.e., same amount of stuffing, same leaks). However, only one of the speakers showed the high distortion at 380hz. The speaker that showed the 380z peak was disassembled, stuffing was added and the drivers were re-installed. Subsequent re-measurement showed the 380hz peak was reduced. It could have just been re-installation of the woofer that improved the 380hz peak issue. Also, other characteristics of the speaker were altered with the additional stuffing, changing the design.
This is evident. It cannot be the internal height mode, as it must then show in both samples. The height mode can leak through a vent, but usually not through a passive radiator (an alternative to vents to avoid leakage of unwanted frequencies by tuning). There must have been other factors and I agree it could just have been the reassembling that fixed it.

Did I understand you correctly, @Nuyes, that you are considering a room mode as a possible cause atm?
The peak at 380hz might be a matter of initial assembly.

Because it hasn't been found in all of that testing the amount and sealing of the sealant and sound absorbing material since I started the repair.

Please refer to the following link.





And the 400hz problem, which I suspected to be room mode, showed up in both samples.
And this is completely different from the 3rd harmonic, which is a common problem with Purifi, as Alan argued.
Because all the overtones appear at the same time.


And when room mode occurs, a pressure difference of air occurs depending on the location of the interior.

Therefore,
1. This may have different effects on the diaphragm of the passive radiator.

2. Depending on the location and density of the internal sound absorbing material, the appearance may be different.


This is why I added sound absorbing material to Sample A.

A resonance of 400 Hz was found in both samples A and B, which differed only by that much, which was eventually mitigated by internal sound absorption.
 

fluid

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Thank you for sharing useful information and knowledge.
You are welcome, the information you have shared is great so I'm trying to help you interpret it.
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.
There is for sure more than one issue apparent in your original measurements. The resonance relating directly to the Purifi driver is present in both but is worse in one. The significant contribution to the overall distortion increase does seem to come from one of the passive radiator's and is in the same frequency range making the analysis more complicated.
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.
Cabinet resonances related to internal dimensions will present as peaks or dips in the frequency response and in the impedance response as blips. The impedance response in your original measurements is very clean in this area and upwards which is not suggestive of a cabinet resonance. The felt seen on the internal surfaces is very effective at reducing internal cabinet contributions. Issues that present as an increase in distortion but without a corresponding peak or dip in frequency are usually mechanical, buzzes rattles, leaks etc. The noise from the binding posts in your video would fall into this category.
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.
No it wouldn't, as above that issue is there but it's not the only one.
 

fluid

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A resonance of 400 Hz was found in both samples A and B, which differed only by that much, which was eventually mitigated by internal sound absorption.
It is very easy to make a change, see a different measured result and interpret the cause of the difference incorrectly. It is obvious to me from the impedance response that too much stuffing was put into the cabinet, as it had a negative impact on the bass tuning. Whilst this had a positive effect on the distortion, attributing this to the cabinet modes seems incorrect as there was no evidence in the original impedance response of a cabinet resonance. What the fairly significant amount of stuffing could have done is damped a mechanical resonance and as tightening of the bolts seems to be an issue this cannot be easily ruled out as a contributor either.
 
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Nuyes

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You are welcome, the information you have shared is great so I'm trying to help you interpret it.

There is for sure more than one issue apparent in your original measurements. The resonance relating directly to the Purifi driver is present in both but is worse in one. The significant contribution to the overall distortion increase does seem to come from one of the passive radiator's and is in the same frequency range making the analysis more complicated.

Cabinet resonances related to internal dimensions will present as peaks or dips in the frequency response and in the impedance response as blips. The impedance response in your original measurements is very clean in this area and upwards which is not suggestive of a cabinet resonance. The felt seen on the internal surfaces is very effective at reducing internal cabinet contributions. Issues that present as an increase in distortion but without a corresponding peak or dip in frequency are usually mechanical, buzzes rattles, leaks etc. The noise from the binding posts in your video would fall into this category.

No it wouldn't, as above that issue is there but it's not the only one.
Thanks for your help.

I understand that problems with these speakers can be due to multiple causes.

As a reviewer and not a speaker designer, what I can say for sure is:

The high distortion of 1.380hz was only seen before disassembling the speaker, and it was only seen in sample A.

2. Afterwards, the target of my experiment was changed to 400hz instead of 380hz, and it was improved only to 'sound absorption' out of all the experiments I could do.
(This also includes changing the driver's torque, which has never shown positive results.)

3.Sample A's distortion level was 'eventually' tuned to good, so I had to set Sample B to the same state to return it to its owner.



The speaker is already out of my hands, but I have the RAW data from this process.

So, I would like to discuss and share this issue with the members of ASR.
 

DualTriode

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Hello All,

An additional insight:

Look at the the Purifi data sheet the peak of the H3 curve is near the problem frequency of 380 hZ

The inside dimension of the enclosure is right at 1/2 Wavelength of 380HZ.

Unfortunately both resonant peaks occur at the same problem frequency of 380 hZ and add up to be a much higher H3 peak.

At this point it looks like correctly torqueing the screws is critical. Plus adding some mass to the motor to shift the resonance frequency or adding some damping and bracing to the motor will flatten the H3 at the problem frequency of 380 hZ.

Thanks DT
 

DualTriode

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.....

Cabinet resonances related to internal dimensions will present as peaks or dips in the frequency response and in the impedance response as blips. The impedance response in your original measurements is very clean in this area and upwards which is not suggestive of a cabinet resonance. The felt seen on the internal surfaces is very effective at reducing internal cabinet contributions. Issues that present as an increase in distortion but without a corresponding peak or dip in frequency are usually mechanical, buzzes rattles, leaks etc. The noise from the binding posts in your video would fall into this category.

.....

Hello,

You might think so.

I do not think the disturbance at 380 hZ is so much distortion as enclosure resonance summing with the driver resonance.

What ever causes the disturbance in the scheme of thing the disturbance looks to be below the fundamental frequency by 40dB or so, overall in the big picture not really bad and not large enough to add much of a blip. However for this low harmonic distortion Purifi woofer the disturbance at 380 hZ looks huge on the otherwise clean looking plot.
 

fluid

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You might think so.
I don't see what I said and you said as contradictory. A mode that is damped enough not to present as response issue in of itself does not suggest, that cannot couple into another mechanism and present as a different problem, which in this case is quite likely.
 

fluid

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3.Sample A's distortion level was 'eventually' tuned to good, so I had to set Sample B to the same state to return it to its owner.
My concern with this for the eventual owner would be that the reduction of low order distortion could be perceptually irrelevant and the changing of the bass response and passive radiator response more relevant.
The speaker is already out of my hands, but I have the RAW data from this process.
Understandable but a shame as a few different tests might have helped draw a more definitive conclusion.
 
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Nuyes

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My concern with this for the eventual owner would be that the reduction of low order distortion could be perceptually irrelevant and the changing of the bass response and passive radiator response more relevant.

Understandable but a shame as a few different tests might have helped draw a more definitive conclusion.
I got all the permission from the owner before I started disassembling.

The entire process was shared with the owner, and the rest could be returned to the previous state at any time except for the sealing of the insert nuts.

Because I recorded the whole process with pictures.

The current repair status is the final result selected by the owner.



I think your opinion is also correct.

Low-frequency responses have obviously decreased, and most people will be more sensitive to this than harmonic distortion.

But in the world, there are some people who are more important to have less variation in distortion.

Sample A's distortion clearly exceeded the manufacturer's guaranteed threshold, and the customer asked the manufacturer for clarification on this, but...
Alan blamed the reviewer for the responsibility for the issue.

So the owner wanted to solve this the most.
 

Chrispy

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So still no particular info on the tightening sequence/torque spec for the driver mounting? So many areas where the thread needs some cleanup/focusing overall, tho.
 

Laserjock

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I’m wondering if this particular pair of speakers would have measured as designed without the flaws would we know who Nuyes is?

Has there been anyone else with these who have heard any flaws or been disappointed with the performance of their purchase of these?
 

restorer-john

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I’m wondering if this particular pair of speakers would have measured as designed without the flaws would we know who Nuyes is?

Has there been anyone else with these who have heard any flaws or been disappointed with the performance of their purchase of these?

With respect, that is no different to the classic response from service agents "Oh this is the first problem we've ever had with X product. (yes, it's a standard BS line)"

The absolute vast majority of people who buy HiFi don't have the means, the knowledge, or the interest in measuring their gear. And neither should they. They base their decisions and place their trust in the manufacturer's statements and specifications.

Where products do not live up to their hype/specs and people have paid a ton of money for them, the situation deserves to be called out. Amir is way to kind IMO with a lot of gear where it clearly doesn't measure up, but he's likely got bigger/more fish to fry.

This Sointuva is not a disaster, but there are clearly facets of the product which don't live up to what was promised. I can see why the binding post issue occurred. Alan would have standard test bananas and would test every speaker. His plugs happened to be solid- he likely never used a hollow 4mm plug or a spade, so the problem with air pouring out was never discovered.

Danny at GR Research would have approved, because they are actually:
1656471935838.png


The rest of it, leaky tweeter-waveguide and resonance issues are probably only obvious due to the very low THD of the entire speaker. In a normal speaker, they would be swamped with other non-linearities. He made a speaker so clean, it highlighted stuff you'd never know about.

But, as usual, it was the dismissive, ducking and weaving and accusations of reviewer incompetence by March, that only served to make it worse. The doubling down, instead of stepping back and acknowledging someone's valid observations and points.
 

Chrispy

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Woah, so we've got Danny boy's famous tube connectors in these speakers? The excitement builds. Along with the nonsense.
 
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