I'm not sure how this results in a cardioid mike with no proximity. How do you check its directivity pattern?
I would certainly appreciate a copy too, can I be the second reader?
I have qualifications in maths, and had enjoyable discussions with Richard Lee on previous technical issues, so this would be a fun way to pick up after a few years too busy at work.
Best wishes
David
Since omni mics don't have the proximity effect.
The proximity effect is a acoustic/mechanical interaction, not a signal effect.
In post we can just apply math to get the right response
Proximity is distance from- and source size dependent (and dependent on capsule size). Plus dependent on angle of incidence. It would be hard to EQ that. Don’t you both agree on the other aspect (that a constructed cardioid from two omnis also will show a proximity effect)?
Again the proximity effect is a acoustic/mechanical issues because how cardioid mics physically work.
A constructed cardioid is just a result of some summing and math.
So how could that ever have proximity effects in it if the source signal doesn't have it in there to begin with?
That entire equation has no idea about distances or proximities?
They could have been at 10 meters away or 10mm.
D
Deleted member 375592
Please correct me if I am wrong but it looks to me that the proximity effect is fully repeatable and can be fully equalized. Yet, a cardio (or super cardio, or figure 8) would provide both far noise suppression (becoming ~f) and reverberation minimization. What about a microphone array? Properly equalized for the specific distance, it could beat some quite expensive competitors (which it did).
I think it's obvious you have never constructed a cardioid from 2 omni capsules and checked its directivity pattern.
However, B&K have done so (and so have I 😊) and IIRC, the results are in the instructions for several implementations of their Sound Intensity wand.
A directional mike constructed out of 2 omnis samples the soundfield at 2 points a specific distance apart. This tells you when the 'directional mike' directivity breaks down too. All in various B&K papers
D
Deleted member 375592
An oversimplification:
Imagine a short tube 1/4" in diameter and a 1/4" diaphragm at one end of it. This is a cardio. The most defining property is the curvilinear distance between front and back centers. The length of the tube affects the proximity effect a lot, which is when the front-to-back ratio of SPL is high.
Imagine a short tube and a diaphragm in the middle. This is a figure-8. Somewhere in between - supercardio.
If you have two omnis, you need a delay equal to the distance/c to form a mini-endfire array. Without delay, 2 omnis are 1 omni with a double surface.
If you have a cardio mic, you can convert it into an omni mic by closing the back holes with "anything".
To me it actually seems that simple.
On the topic of mikes, the proximity effect shouldn’t be mistaken for the sensitivity that open back mikes show for wind noise or ‘plopping’.
On the topic of mikes, the proximity effect shouldn’t be mistaken for the sensitivity that open back mikes show for wind noise or ‘plopping’.
Actually proximity and 'wind & plopping' susceptibility (also handling noise) are intimately related. That's cos a directional mike must sense Particle Velocity (aka Pressure Gradient, Sound Intensity bla bla via various simple and/or complex transforms).
The practical implication is that a directional mike must have SEVERE LF filters.
Da Calrec Mk4 Soundfield and TetraMic (my babies) have the most extended LF of any directional mikes at 27 & 25Hz respectively. They have effectively 30dB/8ve LF filters and you will still ask the hall manager to turn of the aircon. A distant thunderstorm (which might not even register on the Pressure omni W output let alone be heard) can send the XYZ Fig8 Velocity outputs wild. That's a demo of VLF proximity even with my 30dB/8ve filters.
'Proximity' is most easily (??!?) explained by the Wave Eqn. see any elementary Acoustics text. The proof that this happens with 2 spaced omnis, I leave as an exercise to the reader. Da practical minded student may find it faster to just knock up 2 omni electrets ... and I'll accept that as a proof 😊
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And so have I and a LOT of other companies/people !!! 😊😊😊
So, now what? Because your "obvious" thoughts seem to be apparently extremely wrong.
To me there are a lot of VERY obvious things here about people.
But sharing those emotional thoughts isn't very constructive for a technical conversation?
You still seem to refuse to explain in good detail why two omnis mics would sum like if there is a proximity effect.
So we are all waiting....
We are all extremely curious how a summing formula magically knows that two omni mics were in close proximity of the source and not 10 meters away.
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How a cardioid pattern is being made was never point of discussion here.
Point of discussion is the proximity effect.
Those are totally different things.
Why don't you grab the info on the B&K Sound Intensity wand and have a look at what they publish.
Of course, the SI wand is a 'Fig 8' as designed but if you reduce the sensitivity of one of the omnis by 6dB, you sorta get a cardioid including its somewhat lesser proximity. Don't forget the EQ necessary to convert SI (or Pressure Gradient) to a 'flat response' cardioid or Fig 8
But peace b_force. My day job is no longer mike designer but beach bum. It doesn't matter whether you or anyone believes me or not 😊
Yes I see it doesn’t sit well in Multi-way section.
I also felt like it didn’t sit well in Equioment and Tools section.
It is more like more like Process or Method…in the Design and Build sub-forum.
I also felt like it didn’t sit well in Equioment and Tools section.
It is more like more like Process or Method…in the Design and Build sub-forum.
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Don’t get me wrong, but why wouldn’t they?
(Did anyone read the DPA explanation?)
Because that is just a respectful and proper way to have a discussion maybe?
If you look back 10-15 years on this forum, people used to actually explain things and genuinely contribute.
Now, it often feels like discussions are replaced by personal attacks, making it a more hostile environment.
So, if someone is making a claim, it would help to see proper resources, explanations, math, or literature to back it up—instead of calling people out without really understanding the topic.
I’ve shared my part multiple times, but we still don’t have a real answer back.
So, we’ll either keep waiting, or if no answer comes, we’ll need to disregard unsupported responses.
That is just simply how that works.
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This isn’t really about belief.
When someone makes a claim, it’s important they provide some solid evidence to back it up.
Since we’re on the same page about this not being about belief, I’m just looking for that supporting information from you.
So far, I’ve only been asking questions to understand your side.
Until there’s a clear explanation, we’ll have to set aside any claims that aren’t well-supported.
That’s just how objective science and engineering operate
b_force, let's clarify a few things
- Have you actually constructed a Fig8, cardioid or other First order 'directional' mike from 2 omnis, measured it's directivity and checked for proximity? If you have, my (and loadsa other pseudo acoustic gurus) 'belief' in the Wave Eqn will be shattered
It would be the 'necessary & sufficient' proof that Lord Rayleigh & co. were charlatans so please post if you have done this. This is how objective science and engineering operates. - Have you read the B&K stuff on their Sound Intensity wand?
- markbakk suggests there might be a DPA note which might be simpler to grok. Have you read it?
- The clear explanation of this phenomena requires grokking and doing a detailed analysis using the Wave Eqn and fancy maths. While I've done this in the previous Millenium, I no longer have my notes and my single remaining brain cell is unable to replicate such complicated stuff Perhaps some kind soul on this forum, with the necessary facility with the Wave Eqn. could do the honours and 'prove' or 'disprove' my wild assertion but I think most of the forum would prefer the 'necessary & sufficient' evidence you will provide in 1. 😊