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Ascend Sierra Luna Duo Center/Main Speaker Review

Sancus

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Soooo… what are the thoughts now that he sent the same speaker to SEAS and had it measured in their anechoic chamber and their data also matched Daves and not Amir’s.

Not sure where the fire is here. I'm not convinced any of those corrections would have changed the review. Ascend's corrected measurements and the ones from SEAS still look really bad to me, despite being somewhat different from Amir's. Who would look at those and say "oh wow that's actually fine"? Especially compared to their own Luna v2, which is clearly better. Note that off-axis measurements weren't posted, so I assume they're still similar. (I'm not reproducing images since I don't own them and I dunno if they want them reproduced here)

But I feel bad for the guy since he was basically slandered, went out of his way to actually find out if he was wrong and even torched his wallet for nicer measuring equipment than many of the big companies and people were still calling him biased.

I do feel that there's an opportunity here for both sides to learn and I don't know every comment that was made by every person. But fundamentally I don't think saying "I measured and listened to your product and it seems poor" is slander. If anybody insulted Ascend/Dave personally because of how one speaker measured I'd say they were in the wrong regardless of measurements. If there are issues with measurement distances and such, then Amir should consider that and make those corrections going forward. I'm not an expert so I'm not going to say either way, though I'll point out that Amir has mentioned there are a lot of problems with the Nearfield driver measurements such as no level-matching. I've never taken that particular graph very seriously on its own.

The fact that Ascend used this review to go back to the drawing board and build a much better product for their customers seems like a win/win to me and I'm not really seeing how Ascend was harmed. If anything, I think they proved themselves to be a reputable manufacturer that cares about getting things right, and anyone looking at this should be impressed with their conduct and their improved designs.
 

Shazb0t

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Soooo… what are the thoughts now that he sent the same speaker to SEAS and had it measured in their anechoic chamber and their data also matched Daves and not Amir’s. To be honest I’ve been most impressed with Dave’s ability to not get angry. Even now he makes clear Amir had no fault and it’s just hard to measure ribbons and such. And it still allowed him to find more ways to improve things. But I feel bad for the guy since he was basically slandered, went out of his way to actually find out if he was wrong and even torched his wallet for nicer measuring equipment than many of the big companies and people were still calling him biased.

But I don’t think it’s really possible to argue with the measurements from SEAS, given what they do… if they can’t measure a speaker correctly in their own anechoic chamber, then accurate measurements must just be impossible lol.

I’m still glad I waited on getting a duo for my center (sadly horizon is just too big for my current setup), cause better is better, even if I’m totally incapable of hearing the difference.
Did you even read what Dave wrote? He confirmed that Amir's NFS measurements matched his NFS measurements and that both matched SEAS anechoic chamber measurements. He is happy because the higher resolution of the NFS accurately catches port resonances that his MLS near field gated stuff wasn't capable of. He can now definitively put to bed the issue as to why his original measurement system didn't catch the port resonances.

So literally the exact opposite of what you're rambling about. In the end the V2 is a better speaker for going through all of this and now Dave has state of the art measurement capability for future speaker designs. Win win dude.
 
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ctrl

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Sorry, sorry for the outrageously long post, you may slap me on the a...

To be clear, it makes a difference to me whether a DIY proposal of a hobby designer is evaluated, or whether it is a commercial product with which a manufacturer earns money and consumers have to pay money - for the latter, I apply higher standards.


He is happy because the higher resolution of the NFS accurately catches port resonances that his MLS near field gated stuff wasn't capable of. He can now definitively put to bed the issue as to why his original measurement system didn't catch the port resonances.

What I don't like about the manufacturer's post is the presentation as if it was not possible with the "old" technology to determine the serious influence of the BR port on the frequency response of the entire speaker.
You have also completely adopted this view of the facts.

But this is untrue.

For well over ten years there have been precise instructions, available to everyone, on how to create reliable high-resolution frequency responses in the low-mid range using near-field measurements and their combination.

Everyone can read about this in the Arta manual, for example - Section 6.7 S.121ff, specific BR-LS 6.7.2 S.127ff
I have described this here in this thread before.

Correctly measured and performed, i.e. dual channel measurement, sound pressure level equalization of the near-field BR port measurement (green), BR-port delay correction if necessary and the near-field driver measurement, baffle step correction, one obtains for example the following:
1638539564181.png
In red the resulting frequency response of the combined near-field measurements. The influence of the unwanted BR port resonances is limited in this example (the phase shift of BR port and woofer plays a major role). Nevertheless, in this case one would choose a maximum crossover frequency of 700Hz for best results.

Every amateur speaker designer (with some experience) performs these measurements.

Unfortunately, I cannot make "correct" near-field measurements of the Sierra Luna, so I can only show the result of combining the near-field measurements from Amir's sound pressure measurements and derivate minimum phase (which is not correct).
For safety reasons, Amir measures at a greater distance from the drivers (perhaps around 10cm), thus there are room resonances in the near field measurements that further distort the result.

In cyan the combined near-field measurements (as said these are not done correctly this way) of the woofer and BR port and the measurement of Sierra Luna by Seas in anechoic chamber.
1638540822063.png
In the range above 500Hz the problems are clearly visible. If the near-field measurements are performed correctly, the result could be even clearer.




This argument in the "Luna follow up" thread shows the whole problem with the development of the speaker.
So, where am I going with this?
Here is the measurement of the same Luna taken with the NFS at the industry standard of 1 meter. Again, this is a single sweep, non-processed measurement that is not mathematically derived from nearfield measurements...
The peaks and dips are now larger because there is more room influence due to having a further mic distance.
Let's gate this measurement and remove the room:

Where is that horrible port resonance?
Let's add a bit of smoothing:

Now, if you examine the above measurement and compare to our published measurement of our reference Luna, they do track very closely.
At the moment when room resonances are suppressed by a gate, the resulting frequency response (below a certain threshold) is strongly smoothed, depending on the length of the gate.
In standard room measurements, everything below 1kHz experiences a strong smoothing when a gate is used (which is always necessary).

The manufacturer is not yet satisfied with this already heavily smoothed frequency response and smoothes it once more.

And now look everyone, the BR port resonances are no longer visible, so there is actually no problem... and our old measurements are correct.
If such an argumentation makes a beginner, no problem, but an experienced LS designer would never argue so.

With appropriate smoothing, the influence of resonance also disappears in the Luna Seas measurement:
1638542039979.png
This is exactly why LS designers who do not have an anechoic chamber or an NFS available have been evaluating near-field measurements during development for many years.



And finally, the comparison of @amirm's NFS measurement and the manufacturer's NFS measurement with the measurements Seas made in their anechoic chamber of the Sierra Luna.
Since it has been hinted at time and again that Amir's NFS measurements are perhaps not quite correct.
Manufacturer first, then Amir (the sound pressure levels were adjusted as best as possible)
1638543628939.png 1638543679645.png
 
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mboilers

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Did you even read what Dave wrote? He confirmed that Amir's NFS measurements matched his NFS measurements and that both matched SEAS anechoic chamber measurements. He is happy because the higher resolution of the NFS accurately catches port resonances that his MLS near field gated stuff wasn't capable of. He can now definitively put to bed the issue as to why his original measurement system didn't catch the port resonances.

So literally the exact opposite of what you're rambling about. In the end the V2 is a better speaker for going through all of this and now Dave has state of the art measurement capability for future speaker designs. Win win dude.

I can't say I agree with this. He actually spends some time in his very first post talking about the differences between Amir's and his NFS measurements and why he thinks they differ. How does one take that as confirmation that they match?
 

Shazb0t

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What I don't like about the manufacturer's post is the presentation as if it was not possible with the "old" technology to determine the serious influence of the BR port on the frequency response of the entire speaker.
You have also completely adopted this view of the facts.
You're coming at me pretty hard in your response, but I was only responding to @amnesia0287 who believed the reply by Ascend was some sort of vindication for them regarding the existence of the port resonance. As far as I can tell we're both of the same opinion that it's not.

I agree with everything you've said regarding near field measurements and being able to catch the port resonances, but I was simply stating my interpretation of what Ascend's post was as a counter to the other narrative. Anyway I love the content you provide on this site, keep up the good work!

I can't say I agree with this. He actually spends some time in his very first post talking about the differences between Amir's and his NFS measurements and why he thinks they differ. How does one take that as confirmation that they match?
Yea, his language comes off that way, but if you look at the actual measurements it's pretty clear that they're very similar. @ctrl just made the same comparison above. At the end of the day, at least to me, it looks like both Amir and Ascend's NFS measurements are very close to each other and they both are also very close to the measurements made in the SEAS anechoic chamber. Especially in regards to the port resonance issue which was the basis for the whole back and forth. This is a good thing IMO.
 
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