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Sennheiser MKH questions
Old 12th January 2019
  #121
Quote:
Originally Posted by dseetoo View Post
If you are advantrous enough, you might be able to possiblly use a LP and play it back on all sorts of different TT/Cartridge/preamp combo and make your own impulse response from each combination. You can then load those impluse response through a convolution plugin.
Impulse responses aren't going to capture what people probably like most about vinyl, which is its distortion. To do that, you need something like Acustica's Nebula platform, which is based on Volterra series expansions.

David L. Rick
Seventh String Recording
Old 12th January 2019
  #122
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On a 2nd thought, you are probably right.

It is the Die Hard LP Audiophiles' problem. Let them solve it themsolves.
Old 12th January 2019
  #123
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Quote:
Originally Posted by David Rick View Post
Impulse responses aren't going to capture what people probably like most about vinyl, which is its distortion. To do that, you need something like Acustica's Nebula platform, which is based on Volterra series expansions.

David L. Rick
Seventh String Recording
Is that a new business plan? Let's give the listeners what they want!
Old 12th January 2019
  #124
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Quote:
Originally Posted by dseetoo View Post
Using the frequency range we can hear (20-20000Hz) as the only requirement for the recording chain has a major flaw; poor phase response.
Where is this manifested? You mean in the microphone?

Quote:
When was the last time you looked at a square wave of any frequency going through an audio chain that can only go down to that particular frequency?
Never, its not a musical or real signal. It's a hi-fi mag test signal.

Quote:
For a given frequency of square wave to resemble as such, your low-end bandwidth needs to be one tenth of that, thus 2Hz.
Well in theory this is incorrect, there are no components of a square wave below the fundamental.

But I am not quite sure of your point here Da-Hong. Are you encouraging us all to get our mics high pass filter cutoff lowered so that we can record a 20Hz square wave properly?
Old 12th January 2019
  #125
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Quote:
Originally Posted by David Spearritt View Post
Where is this manifested? You mean in the microphone?


Never, its not a musical or real signal. It's a hi-fi mag test signal.


Well in theory this is incorrect, there are no components of a square wave below the fundamental.

But I am not quite sure of your point here Da-Hong. Are you encouraging us all to get our mics high pass filter cutoff lowered so that we can record a 20Hz square wave properly?


David,

You need to look at a square wave going through a system that has a HP filter set to the frequency of the square wave. It does not have to be a 20Hz square wave, use a higher one so it is more audible when you try to listen to it with or without the HP filter. Get a scope and do some poking around since you have never down it. Actually, you don't even need a scope, you can do this on your DAW with a digitally generated square wave and put it through some bandwidth limiting filters and see/hear what happens to the signals.


Any bandwidth limitations, electrical or mechanical also affects the phase response. The further away the limitations are from the music signal you try to record the better off you are. The most legit reason going to higher sampling rate is the bandwidth and phase response issue. In this case, it is for the high end. For LE, we can extend it with any sampling rate.


Da-Hong
Old 13th January 2019
  #126
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Da-Hong, thanks for the explanation.

There is no doubt filters are a necessary evil in band-limiting the audio being recorded. But without them things can get ugly pretty quickly. I chose all my Schoeps preamps to be CMC5 for a gentler HP filter at 30Hz. But if that is lowered so that I can filter in the DAW later, the protection against LF overload of the mic circuit is less, and so I would rather suffer a little phase shift in the bottom octave than destroy the whole signal pickup.

I haven't noticed any LF phase artifacts in the few organ recordings I have done or in orchestral examples, and I always master with a very aggressive LF filter in place below 20Hz, since my dipole speakers have huge EQ at LF, and I don't want the woofers bouncing around the room.
Old 14th January 2019
  #127
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Quote:
Originally Posted by David Spearritt View Post
Da-Hong, thanks for the explanation.

There is no doubt filters are a necessary evil in band-limiting the audio being recorded. But without them things can get ugly pretty quickly. I chose all my Schoeps preamps to be CMC5 for a gentler HP filter at 30Hz. But if that is lowered so that I can filter in the DAW later, the protection against LF overload of the mic circuit is less, and so I would rather suffer a little phase shift in the bottom octave than destroy the whole signal pickup.

I haven't noticed any LF phase artifacts in the few organ recordings I have done or in orchestral examples, and I always master with a very aggressive LF filter in place below 20Hz, since my dipole speakers have huge EQ at LF, and I don't want the woofers bouncing around the room.


Hi David,

Let me get two facts straight first for everybody interested.

One; There are two versions of Schoeps CMC5 body. One with an additional small input filter cap and the one without. Most of CMC5s I have encountered are without the additional input cap. The rest of circuitry and parts are exactly the same amount both versions. The version with the additional input cap has HP turnover a bit higher.

Two; the HP turnover frequency in CMC5 bodies is actually set to more like 20Hz, not 30Hz. The filter cap is 0.1uF and the impedance is 75Kohms. It is a simple first order filter. You can do the meth yourself.

In regard to your statement of “I haven't noticed any LF phase artifacts in the few organ recordings I have done”, my question is how would you know that if you don’t have the means to compare it to the same microphone without the HP filter? Hearing is believing, right?

My Schoeps microphones have no HP filter in them. I recorded some very loud drums and percussive instruments at fairly close range with them and so far I have not been able to overload them. I did record starter guns on stage once or twice which might have overloaded the microphone/preamp. The person pulled trigger had to wear hearing protective muffs. But, that is for effects so it didn’t really matter. It is such an ugly sound anyways. I could have recorded some fire works outside and dubbed it in instead.

Da-Hong
Old 14th January 2019
  #128
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whippoorwill's Avatar
Quote:
Originally Posted by dseetoo View Post
Two; the HP turnover frequency in CMC5 bodies is actually set to more like 20Hz, not 30Hz. The filter cap is 0.1uF and the impedance is 75Kohms. It is a simple first order filter. You can do the meth yourself.
doing meth would probably impair your ability to calculate these things Da-Hong.
Old 14th January 2019
  #129
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Quote:
Originally Posted by whippoorwill View Post
doing meth would probably impair your ability to calculate these things Da-Hong.

Now you know what I was on when I wrote all my crap.
Old 14th January 2019
  #130
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Quote:
Originally Posted by dseetoo View Post
Hi David,

Let me get two facts straight first for everybody interested.

One; There are two versions of Schoeps CMC5 body. One with an additional small input filter cap and the one without. Most of CMC5s I have encountered are without the additional input cap. The rest of circuitry and parts are exactly the same amount both versions. The version with the additional input cap has HP turnover a bit higher.

Two; the HP turnover frequency in CMC5 bodies is actually set to more like 20Hz, not 30Hz. The filter cap is 0.1uF and the impedance is 75Kohms. It is a simple first order filter. You can do the meth yourself.

In regard to your statement of “I haven't noticed any LF phase artifacts in the few organ recordings I have done”, my question is how would you know that if you don’t have the means to compare it to the same microphone without the HP filter? Hearing is believing, right?

My Schoeps microphones have no HP filter in them. I recorded some very loud drums and percussive instruments at fairly close range with them and so far I have not been able to overload them. I did record starter guns on stage once or twice which might have overloaded the microphone/preamp. The person pulled trigger had to wear hearing protective muffs. But, that is for effects so it didn’t really matter. It is such an ugly sound anyways. I could have recorded some fire works outside and dubbed it in instead.

Da-Hong
Da Hong, interesting information. How are things with the cmc 6? Do you prefer those?
Old 14th January 2019
  #131
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Quote:
Originally Posted by dseetoo View Post
My Schoeps microphones have no HP filter in them. I recorded some very loud drums and percussive instruments at fairly close range with them and so far I have not been able to overload them. I did record starter guns on stage once or twice which might have overloaded the microphone/preamp. The person pulled trigger had to wear hearing protective muffs. But, that is for effects so it didn’t really matter. It is such an ugly sound anyways. I could have recorded some fire works outside and dubbed it in instead. Da-Hong
So gunshots or percussion is not what concerns us here, with HP filters, as these sources are mostly HF and have very little LF in their spectrum.

Very LF air handling or other rumbles are what can overload the mic amp if there is no HP filter present.

Last edited by David Spearritt; 14th January 2019 at 09:01 PM..
Old 14th January 2019
  #132
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Quote:
Originally Posted by David Spearritt View Post
So gunshots or percussion is not what concerns us here, with HP filters, as these sources are mostly HF and have very little LF in their spectrum.

Very LF air handling or other rumbles are what can overload the mic if there is no HP filter present.
I've had this trip me up a few times in one particular venue, usually when cardioid mics are being used. The air-con airflow can be virtually undetectabe at floor level, but the ducting vents can be directing a stream at the capsules from above....dependent upon fan speed and regularity. I suspect some are even deliberately designed to be 'intermittent', or ' breeze-like' in operation ?

Yes it's very LF indeed, and more to the point it's a very low velocity... yet quite sizeable volume... of air being aimed at the capsules. The low velocity means it barely registers on your skin as air movement, if at all, but to a mic capsule it's another matter entirely ! In my experience, no amount of regular foam windsocking can alleviate it...you'd almost need to blimp it to attain the air stillness necessary !

As for a high pass circuitry solution, when you have the capsule diaphragm being subjected to that sort of buffeting...I doubt any signal filtering is going to work. You'll still have the membrane generating a very sizeable signal in response to unusual (non-music related) displacement....so a circuit-based HPF is introducing a solution 'after the bull is already in the china shop' ! The buffeting probably ranges across a frequency spectrum to boot...it's not like Kingsway Hall underground train (acoustic) rumble.....

You gotta stop that air...via mechanical (trapping) means...or as I tend to do, turn off the aircon well before the concert begins, and set the thermostat high enough so it doesn't kick back in...if you can get away with such devious behaviour ?

Last edited by studer58; 14th January 2019 at 12:57 PM..
Old 15th January 2019
  #133
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Quote:
Originally Posted by Lucas_G View Post
Da Hong, interesting information. How are things with the cmc 6? Do you prefer those?

CMC5 is a much better choice, as far as I am concerned. But, that is for a different reason.
Old 15th January 2019
  #134
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Quote:
Originally Posted by David Spearritt View Post
So gunshots or percussion is not what concerns us here, with HP filters, as these sources are mostly HF and have very little LF in their spectrum.

Very LF air handling or other rumbles are what can overload the mic amp if there is no HP filter present.
Air handling capability is only a concern with directional capsules. Omni is pretty much immune to air flow issue in the hall due to its higher membrane tension.

Gun shot has a lot of low end energy in it. It is an explosion after all, thus it changes the air pressure in the hall. The sound it makes is very much full spectrum.
Old 15th January 2019
  #135
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Quote:
Originally Posted by dseetoo View Post
CMC5 is a much better choice, as far as I am concerned. But, that is for a different reason.
Is it sonically better?
Old 15th January 2019
  #136
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Quote:
Originally Posted by Lucas_G View Post
Is it sonically better?

Read the post number 2 in this thread.

Schoeps cmc5 vs cmc6
Old 15th January 2019
  #137
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Quote:
Originally Posted by dseetoo View Post
Read the post number 2 in this thread.

Schoeps cmc5 vs cmc6
Thanks a lot for that information. One would assume the newer one to be better, but often this is not the case.
Old 15th January 2019
  #138
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Quote:
Originally Posted by dseetoo View Post
Read the post number 2 in this thread.

Schoeps cmc5 vs cmc6
Quote:
Originally Posted by king2070lplaya View Post
Quote:
Originally Posted by blackfinder View Post
do you have a link for that thread ?
It's at the very beginning of this thread that we're writing on.
Please note in that same thread, DSATZ in post #37 ,
that discusses his testing that showed NO difference in noise level between the CMC5 and
CMC6.
Old 16th January 2019
  #139
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josephson's Avatar
Just a bit of technical clarity (hopefully) with respect to some of the posts in the thread...

An omni mic capsule, being "sealed" behind the diaphragm, needs a bit of a leak to avoid being blown up if you take it on an airplane. Precision omni capsules like the MK221 used in our C617SET have a microscopic capillary slot that sets a LF turnover point below 1 Hz. Sometimes it's laser cut, sometimes it's a piece of very fine tubing. This represents one pole of a HP filter. Then, the electronics often throw in a few more poles -- coupling cap(s) in some circuits, the polarization resistor together with the capsule capacitance in DC-polarized mics, the discriminator components in RF condenser mics, servo time constants in the preamp, etc. There is no magic in either high-impedance DC-polarized or impedance-bridge RF mics. Theoretically either could go to DC but for practical reasons we choose rolloff points.

We are concerned with ultra low frequency response not because we want to record sonic booms, microbaroms or whales, but because *filters cause phase shift* whether they are implemented in electronics or mechanics. We make gain staging decisions based on staying within a useful noise/overload range, we make rolloff decisions based on not damaging phase response.
Old 16th January 2019
  #140
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Thanks to DaHong and DJ for illuminating this issue.

But I still think some practicalities weigh against getting our mic body HPF corner frequency lowered.

1. I do not want to dedicate a particular set of Schoeps bodies to omni use only.
2. Waves of A/C air in the concert hall and structure borne rumbles and other excitation still maybe audibly intrusive and overload mic amps. After all this is why Schoeps implement such a filter characteristic in the first place.
3. How noticeable is LF phase shift anyway at 20Hz (CMC5, 45 deg, wavelength 17m ~ roughly 2m distance shift?) and up to what freq? I don't think I have heard any artefacts when comparing to the live sound, even with very healthy LF response phones (Denon ADH9000) and the bass sounds wonderful (from M150's) on my full range home system.

Interested in what repertoire and recording setup exhibited deal breaking LF phase distortion that prompted the lowering of HP filter corner freq.
Old 16th January 2019
  #141
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Quote:
Originally Posted by David Spearritt View Post
Thanks to DaHong and DJ for illuminating this issue.

But I still think some practicalities weigh against getting our mic body HPF corner frequency lowered.

1. I do not want to dedicate a particular set of Schoeps bodies to omni use only.
2. Waves of A/C air in the concert hall and structure borne rumbles and other excitation still maybe audibly intrusive and overload mic amps. After all this is why Schoeps implement such a filter characteristic in the first place.
3. How noticeable is LF phase shift anyway at 20Hz (CMC5, 45 deg, wavelength 17m ~ roughly 2m distance shift?) and up to what freq? I don't think I have heard any artefacts when comparing to the live sound, even with very healthy LF response phones (Denon ADH9000) and the bass sounds wonderful (from M150's) on my full range home system.

Interested in what repertoire and recording setup exhibited deal breaking LF phase distortion that prompted the lowering of HP filter corner freq.
Deal-breaker is probably a bit overstated., but wouldn't you rather deal with LF problems in post on a case to case basis?
Old 16th January 2019
  #142
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Quote:
Originally Posted by Lucas_G View Post
Deal-breaker is probably a bit overstated., but wouldn't you rather deal with LF problems in post on a case to case basis?
Not if I have to repair a distorted or overloaded waveform, that is much worse in my book.
Old 16th January 2019
  #143
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Quote:
Originally Posted by Lucas_G View Post
Deal-breaker is probably a bit overstated., but wouldn't you rather deal with LF problems in post on a case to case basis?
I think I'd rather first know what musically-significant tones, and from which instrument (or massed combo of instruments) I'd be likely to be missing out on by implementing a particular filter in a mic's preamp body.

To be completist about it, you'd have to include the possibility of electronic music, and samples, amplified and played back through full range PA speakers, as part of the performance....although for these you'd very likely take a balanced line level or DI output from the instrument also, as a duplicate feed....which could then be treated/processed at mix down ?

You'd have to include any LF reverb components supported by the particular space (eg hall, cathedral, etc) The anticipated amplitude of those LF's would come into play also ? Traffic rumble, I'll grant you, is very unlikely to cause the same buffeting overload as rampant aircon blasts....so I'll live with the bugbear of traffic, and therefore Rx it in post....

Or we could cut to the chase and simply do an analysis of what a particular organ in a given venue is going to be supplying us with, and work back from there.

Like David, I'm keen to omit air-movement induced mic overload...but I still maintain that's best done by wind-screening the capsule, or terminating the aircon at concert time...trying a preamp-filter fix after the capsule's been buffeted is too late.

If you're using the mics for non-musical, environmental logging type jobs, you'd likely have a whole different set of (non-filtering) priorities in play...
Old 16th January 2019
  #144
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Quote:
Originally Posted by David Spearritt View Post
Not if I have to repair a distorted or overloaded waveform, that is much worse in my book.
That is true, but up till now I have never seen that. If my headroom unexpectedly was eaten up, it is always by a soprano or a percussion group. Never had any turbulences of air that would eat up my headroom. In post one can very delicately filter out LF when necessary, but even there I try to preserve as much as possible of LF energy to let the ambience of the hall remain in place. Only the very intrusive would get filtered out.
If the capsule itself would distort by heavy turbulence, a HP in the electronics won’t save us, so applying a windscreen would be the only solution.

Most churches in the Netherlands have a heating system that blows hot air into the church. These could potentially cause overloads, I guess, but since they are so extremely loud I have always shut them down during recording.
Old 16th January 2019
  #145
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Lucas you're fortunate if you've never had to contend with borderline (or worse) intrusive air-con buffeting....it's nerve wracking to watch your metering shoot up towards 0 and to know there's nothing you can do about, which is why we're on the same page about preventive measures pre-concert.

Yes, soprano shatter.... I haven't suffered that for many years, but when it occurs (even when she's metres away from the mic) it's a puzzling and frightening event !
Old 16th January 2019
  #146
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Quote:
Originally Posted by studer58 View Post
Lucas you're fortunate if you've never had to contend with borderline (or worse) intrusive air-con buffeting....it's nerve wracking to watch your metering shoot up towards 0 and to know there's nothing you can do about, which is why we're on the same page about preventive measures pre-concert.

Yes, soprano shatter.... I haven't suffered that for many years, but when it occurs (even when she's metres away from the mic) it's a puzzling and frightening event !
With live concerts or recording sessions I always personally talk with the staff in order to get them pre-heating the church some two hours in advance. I also ask where the main switches are, and that has saved me on many occasions.

You are right about soprano's, but believe me, they can privately be very scary too!
Old 16th January 2019
  #147
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Quote:
Originally Posted by studer58 View Post
Lucas you're fortunate if you've never had to contend with borderline (or worse) intrusive air-con buffeting....it's nerve wracking to watch your metering shoot up towards 0 and to know there's nothing you can do about, which is why we're on the same page about preventive measures pre-concert.


Most of AF condenser microphones have two electronic stages, the impedance transfer stage and output stage. The HP filter is always placed between the two stages. A properly designed circuit will always have much higher dynamic headroom in the output stage than that of first stage. Therefore, using HP filter to reduce the potential airflow induced overload will not help at all because first stage will be overloaded before the signal reaches the HP filter. The exception will be if the microphone uses output transformer which can overload before the input stage at LF. In that case, you should use -10dB pad on the microphone.

If the LF is overloading the rest of the recording chain, you should reduce the frontend gain setting. With a modern clean 24Bit recording chain, you can very conservatively set the gain.
Old 16th January 2019
  #148
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fred2bern's Avatar
Sometimes foams are also useful...
Old 16th January 2019
  #149
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Quote:
Originally Posted by josephson View Post
*filters cause phase shift*
Just thought that this point needs to be emphasized.

Many folks don't seem to understand that filters do more to the sound than just eliminating undesirable frequencies.
Old 16th January 2019
  #150
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I wonder how many linear phase omni users actually use sealed loudspeakers.
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