The No.1 Website for Pro Audio
What's the flattest response mic?
Old 2 weeks ago | Show parent
  #121
Gear Guru
 
1 Review written
🎧 5 years
Quote:
Originally Posted by dasbin ➡️
Air absorption is only really applicable in most indoor venues above 10Khz, so something else is going on here. I suspect that by "speaker systems" you are referring to systems comprised of multiple loudspeakers. This kind of response is typical in, for example, line arrays, where mids and lows from all boxes will sum throughout the venue (because of a lack of directivity in the lows), but highs will not (because at any particular spot, you are mostly hearing the output of a single directive horn).

This is why "systems" (especially systems made of many loudspeakers, like line arrays) always need massive EQ correction once installed in a venue. A PA should never be left in this kind of state. It is typical to have the system processor cut ~20db or more in lows and low-mids on a line array once installed.
not quite...

these measurements (rta as you correctly mentioned) stem from three different locations of which only one uses a line array - also, most subwoofer arrays are designed in a way that they become rather directional at whatever frequency; of course the lower one goes, the more difficult it gets - the idea that one hears just the output of a single directive horn in a specific position when using a line array is flawed.
nothing else going on here either and no way on earth someone is cutting the lows this much: on the contrary, most system these days get aligned with a 6-10dB bass bump (unfortunately)!

please note that as mentioned previously, these screenshots are no measurements of the systems with pink noise on but what the actual response of the music looks like; measurement responses of the systems with pink noise would indeed look way more flat, depending on distance and alignment. nevertheless, roll off starts almost always clearly below 10kHz, certainly for music reproduction: i usually go for a curve that is close to the old b&k curve (or the whatever the headliner's tech wants me to dial in).

for comparison, here's a screenshot from a measurement (fft in this case) of a system which i re-installed last summer, in a venue that mostly houses classical music (and for which the system doesn't get used at all) but also modern music and jazz which was taken into consideration when designing, positioning and aligning the system (which is fairly large/uses a multitude of speakers, both arrays and point source speakers, fills, delay lines, subs etc.)
Attached Thumbnails
What's the flattest response mic?-20210401_191842.jpg  

Last edited by deedeeyeah; 2 weeks ago at 06:56 PM..
Old 2 weeks ago | Show parent
  #122
Gear Guru
 
1 Review written
🎧 5 years
Quote:
Originally Posted by dseetoo ➡️
To really find out the amount of correction that is needed due to long microphone distance you need to sweep the stage to generate some high quality profiles. Sticking up a measurement mic next to your mains won't do it, I am afraid.
lol - thx but i guess you're hitting the wrong person! afaik i'm one of the very few folks around this forum who does actually carry (or rents) a pa even on acoustic gigs (if i haven't been working in the venue before which is highly likely if it's in europe though) exactly for this purpose: to shoot the room (and to sample the room for later use of my sony reverb) - besides, i'm often using a multi-mic rig for measuring...
Old 2 weeks ago | Show parent
  #123
Gear Addict
 
🎧 15 years
Quote:
Originally Posted by deedeeyeah ➡️
not quite...

these measurements (rta as you correctly mentioned) stem from three different locations of which only one uses a line array - also, most subwoofer arrays are designed in a way that they become rather directional at whatever frequency; of course the lower one goes, the more difficult it gets - the idea that one hears just the output of a single directive horn in a specific position when using a line array is flawed.
nothing else going on here either and no way on earth someone is cutting the lows this much: on the contrary, most system these days get aligned with a 6-10dB bass bump (unfortunately)!

please note that as mentioned previously, these screenshots are no measurements of the systems with pink noise on but what the actual response of the music looks like; measurement responses of the systems with pink noise would indeed look way more flat, depending on distance and alignment. nevertheless, roll off starts almost always clearly below 10kHz, certainly for music reproduction: i usually go for a curve that is close to the old b&k curve (or the whatever the headliner's tech wants me to dial in).

for comparison, here's a screenshot from a measurement (fft in this case) of a system which i re-installed last summer, in a venue that mostly houses classical music (and for which the system doesn't get used at all) but also modern music and jazz which was taken into consideration when designing, positioning and aligning the system (which is fairly large/uses a multitude of speakers, both arrays and point source speakers, fills, delay lines, subs etc.)
Did you really leave the system like that? Were they happy with it?

I hope I'm not coming across as a jerk, I'm just baffled by seeing that curve. I design and tune installed systems and would never ever leave a system looking/sounding like that. Yes, sometimes clients want 6db of sub tilt below 100hz. But to not correct the rest of the range, especially the low-mid summation build-up and at least some of the air absorption (which is that sharp roll-off at 14k you have)... I can't imagine that system is anywhere near sounding its best.

The correlation trace is abysmal too, which makes me think either the measurement is not being done properly, or is way off-axis of the speakers, or the space is incredibly reverberant, or something in the system is straight-up broken. Given the correlation trace, you can't rely on any part of the measurement being accurate other than the 150hz region. Where is the signal in time, in the impulse measurement up top? It should appear as a single point in time, plus or minus a couple distinct later reflections. Instead there is a cacophony of noise. It looks like SMAART probably couldn't even find the correct delay value.

As for the frequency response, like I said, line arrays or other multi-element systems often start out looking something like this. But they cannot be left in that state. It would sound horribly muddy and exacerbate any room build-up. You said "no way on earth someone is cutting the lows this much" but I promise you it happens every day on professional systems. Such cuts are almost always built in to multi-element presets in system processors. Processors are designed to be used to cut that much of the lows in multi-element installations.

Have a look -- here is the default EQ curve that Meyer uses for a 4-box Mina array at 100ft distance with 100% atmospheric correction (which is the 16Khz bump *only*). This is what they know will bring 4 boxes flat in an anechoic environment - and each individual box starts already flat in the nearfield by itself. The curve needs to get even more extreme if you add above 4 boxes, and also is not accounting for any kind of room response yet. EQ curves bigger than this are being used every day on systems everywhere.
Attached Thumbnails
What's the flattest response mic?-capture.jpg  

Last edited by dasbin; 2 weeks ago at 07:41 PM..
Old 2 weeks ago | Show parent
  #124
Gear Guru
 
1 Review written
🎧 5 years
Quote:
Originally Posted by dasbin ➡️
Did you really leave the system like that? Were they happy with it?

I hope I'm not coming across as a jerk, I'm just baffled by seeing that curve. I design and tune installed systems and would never ever leave a system looking/sounding like that. Yes, sometimes clients want 6db of sub tilt below 100hz. But to not correct the rest of the range, especially the low-mid summation build-up and at least some of the air absorption (which is that sharp roll-off at 14k you have)... I can't imagine that system is anywhere near sounding its best.

The correlation trace is abysmal too, which makes me think either the measurement is not being done properly, or is way off-axis of the speakers, or the space is incredibly reverberant, or something in the system is straight-up broken. Given the correlation trace, you can't rely on any part of the measurement being accurate other than the 150hz region. Where is the signal in time, in the impulse measurement up top? It should appear as a single point in time, plus or minus a couple distinct later reflections. Instead there is a cacophony of noise. It looks like SMAART probably couldn't even find the correct delay value.

As for the frequency response, like I say, line arrays or other multi-element systems often start out looking something like this. But they cannot be left in that state. It would sound horribly muddy and exacerbate any room build-up. You said "no way on earth someone is cutting the lows this much" but I promise you it happens every day on professional systems. Such cuts are almost always built in to multi-element presets in system processors. Processors are designed to be used to cut that much of the lows in multi-element installations.
i don't recall when i took this pic during a two-day period of aligning the system so i have no idea what was going at this very moment, which sub-system was already frequency or time aligned, switched on or not, correctly positioned or not (they are using three different stage sizes for which sidefills need to get re-positioned) etc.

the only reason i posted these pics was to illustrate (to those who probaly never get use a measurement mic but might know that they essentially measure flat, whatever that means...) that there are massive differences what a mic can 'hear' and how the graphs can look depending on the distance of the mic to the source...

...or short: to underline dseetoo's post 108.




p.s. yes, the venue is fairly reverberant - here's a link to another thread which has some pics of the venue (sorry, 'concert hall'...); i'm sure you understand i cannot share detailed information on the alignment though...

reinstall before restart
Old 2 weeks ago | Show parent
  #125
Gear Nut
 
Quote:
Originally Posted by studer58 ➡️
Not to mention low frequencies also, at around 30cm or less....the proximity effect. This applies to directional (eg fig 8, cardioid) mics, not omni.

Mic's don't actually 'pick up more HF' with proximity....there's simply less of the loss of HF that occurs with increased distance, so the perception is that there's more of it.
My consideration is probably dumb, but I would think that approaching to the source with an omni may, in addition to a less HF loss, produce a different behavior also depending on the proximity to a certain part of the instrument.
Is it wrong to say that, if I have a flat omni mic and want to record a dark sounding piano I can achieve some "brilliance" placing the mic closer to the high notes more than the bass?
Old 2 weeks ago | Show parent
  #126
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by jnorman ➡️
Back to the OP’s original question, find out what DPA mics NASA sent to Mars on the Perseverance rover and you will have your answer.
Those designs will be compromised for weight. I worked on a NASA Launch tower, we had to fight over weight vs requirements. They backed on the requirements to satisfy weight of the launch tower. I can just imagine the weight limitation for stuff on mars.
Old 2 weeks ago
  #127
Lives for gear
 
jnorman's Avatar
 
3 Reviews written
🎧 15 years
Elegent - the DPA site says:
a 4006 Omni Mic, MMA-A Digital Audio Interface and MMP-G Modular Active Cable,
Old 2 weeks ago | Show parent
  #128
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by jnorman ➡️
Elegent - the DPA site says:
a 4006 Omni Mic, MMA-A Digital Audio Interface and MMP-G Modular Active Cable,
Looks pretty lightweight...as far as interfaces go !

https://youtu.be/6WuHIaWIDCw
Old 2 weeks ago | Show parent
  #129
Lives for gear
 
🎧 10 years
Quote:
Originally Posted by carpa ➡️
My consideration is probably dumb, but I would think that approaching to the source with an omni may, in addition to a less HF loss, produce a different behavior also depending on the proximity to a certain part of the instrument.
Is it wrong to say that, if I have a flat omni mic and want to record a dark sounding piano I can achieve some "brilliance" placing the mic closer to the high notes more than the bass?
Yes, you're right in that you'd be effectively 'mixing via placement'...so discriminating via mic location towards those sounds you want to emphasize vs those you want to mask,,,perhaps ?

In your piano example, it's possible for example that the bass content remains relatively constant (let's say under the lid) but that you'd increase brightness by bringing it closer to treble strings, thus altering the ratio of darker to lighter tones ? The darker tones might remain constant, but you'd be 'swamping/saturating' them with the 'brilliant' tones ?

In my example, I was thinking more of a whole orchestra as the sound source...in that case, there are limits on how close you can get while still retaining balance...and "balance" in this context is more about instrument-group representation, rather than high vs low frequencies per se ?
Old 2 weeks ago | Show parent
  #130
Gear Nut
 
Quote:
Originally Posted by studer58 ➡️

In my example, I was thinking more of a whole orchestra as the sound source...in that case, there are limits on how close you can get while still retaining balance...and "balance" in this context is more about instrument-group representation, rather than high vs low frequencies per se ?
This is exactly what I meant. One thing is the source "as a whole", in which probably the distance affects HF response by moving back and forth. I was asking about a more "spot" use of omnis which may also help to "tune" the recorded sound not only in terms of louder or softer ( which gain level can adjust) but also as brighter or darker. Still a possible use of flat mics...
📝 Reply

Similar Threads

Thread / Thread Starter Replies / Views Last Post
replies: 16 views: 10430
Avatar for Mend
Mend 26th May 2020
replies: 51 views: 14486
Avatar for Hogwash
Hogwash 31st March 2014
replies: 4 views: 525
Avatar for nat8808
nat8808 29th December 2020
replies: 131 views: 5014
Avatar for RayS
RayS 2 weeks ago
Post Reply

Welcome to the Gearspace Pro Audio Community!

Registration benefits include:
  • The ability to reply to and create new discussions
  • Access to members-only giveaways & competitions
  • Interact with VIP industry experts in our guest Q&As
  • Access to members-only sub forum discussions
  • Access to members-only Chat Room
  • Get INSTANT ACCESS to the world's best private pro audio Classifieds for only USD $20/year
  • Promote your eBay auctions and Reverb.com listings for free
  • Remove this message!
You need an account to post a reply. Create a username and password below and an account will be created and your post entered.


 
 
Slide to join now Processing…

Forum Jump
Forum Jump