J
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« Reply #24 on: July 22, 2005, 09:10:11 PM »
Steven,
I don't understand why I've given you whiplash. I sure hope your insurance covers you for it!
If you read all my postings on this subject (and I don't know why anyone would) then I think you'd find a very clear logic -- it is the notion of obvious personalities versus more subtle personalities in microphones. It is not limited to frequency response but design philosophy, transient response etc. How can that not be clear??
With regard to impedance, I thought you and I hashed that out at the beginning. I said I didn't think there would be any change as long as a low impedance went into a higher one. Then you stated a reason as to why that may not be so. So if the question is "does impedance have an effect?" then based on your information alone the answer must be "yes."
Are different preamps going to make a difference due to impedance or some other aspect of design? Sure.
I am sorry if I've been difficult to understand or have somehow appeared to flip-flop. It's not my fault you can't read my mind! ;>) -- I hate smiley symbols.
Barry
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« Reply #25 on: July 22, 2005, 09:32:58 PM »
Steven, I don't know the API preamps, but you describe them as having input transformers with a relatively high turns ratio. This type of input circuit makes good sense for use with low-output dynamic microphones, since you can get as much as 20 dB "free" voltage gain right at the input. But this voltage gain in the input stage is unnecessary with high-output condenser microphones, and in fact can cause some rather severe problems.
The most easily predictable of these problems is input stage overload at high sound pressure levels. This is especially dangerous since most preamps do not have overload indicators that respond to conditions at the input; you can record a live performance and not hear the distortion until it's too late.
Another problem that may be less well known or expected is that the input circuit's high frequency response can deviate several dB from linear when driven by a very different source impedance from what the preamp's design "expects." The problems can range from an unintended rolloff to possibly boosted, peaky response. In extreme cases of peaky response, bursts of parasitic oscillation can even occur on transients.
In many (most?) U.S.-designed preamps that have this type of input circuit, a 150 - 200 Ohm microphone source impedance was assumed. But the Schoeps CMC 6-- amplifier has an output impedance of only 35 Ohms when operated from a 48 Volt supply. So unfortunately, your preamp can't be assumed to work correctly in the top two audible octaves or so, given its design. Maybe it's working properly but maybe it really isn't.
If you have access to a pair of balanced, resistive pads (Shure A15A for example) please try inserting them at the inputs to your preamp. That will reduce the output from the microphones so that input overload is far less likely to occur, and at the same time will raise the driving impedance that the preamp's inputs are "seeing," bringing it into the intended range.
If this causes a noticeable change in the sound of the microphones, then you've got evidence that the preamp is unfortunately not especially suitable for use with modern, transformerless condenser microphones--and not only Schoeps, by the way. And if there is a difference, then the sound that you get with the pads in place should be more representative of what the microphones are actually capable of putting out.
Would you please let us know what you find?
--best regards
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« Reply #26 on: July 23, 2005, 12:23:52 AM »
David Satz wrote on Sat, 23 July 2005 02:32 |
Steven,
Would you please let us know what you find?
--best regards
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David, As I said in an earlier post, I don't have access to the Schoeps now. I had them on loan for a short time. I am aware of input stage overloading and that was not the case in this instance. If ever I do get the chance I will try your other suggestions. Sincerely, LRRec
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« Reply #27 on: July 23, 2005, 02:49:11 AM »
bonne wrote on Fri, 22 July 2005 18:56 |
Mark and Steven,
I have been testing Schoeps microphones the last few months in my quest to find a good setup for recording steel string acoustic guitar in the nearfield (about one foot out). CMC6 amps with Mk21, MK41, Mk4, Mk5 and MK8 in different stereo setups.
I found the same "artificial" sound and "grainy top end" you both are referring to, much to my surprise. The sound was very different from the actual sound of the guitar in the room. Guitar used was a Lowden with a big and solid sound overall and very full sounding treble.
J
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« Reply #28 on: July 23, 2005, 12:35:02 PM »
Hi Ivo,
I'm sure very expensive preamps and converters would make a difference.
But if we concentrate on the microphones for a second, I have in the last couple of months recorded with different stereo setups involving microphones from B&K, Brauner, Sennheiser (MKH-series), Royer and others in addition to Schoeps. Spaced, crossed, M/S and Blumlein. Using the same chain in every instance. The Schoeps setups especially were lacking in reproduction of the treble part of the instrument leading to an artificial overall sound, both in relation to the actual sound in the room AND in comparison to the results achieved with the other setups. Davids explanation of the impedance issues related to Schoeps and different preamps may be a part of this picture. Like Steven I have unfortunately returned the Schoeps by now and won't be able to test with the suggested resistive pads at the moment.
I mentioned the Steve Albini sample recording with Schoeps (from the Royer demo) because although he most likely used a different chain than I did, I recognised right away the weak top end of the Martin guitar he was recording. Very similar to what I got using Schoeps on a Lowden. This similarity was clearly evident both on my studio setup and on my living room stereo setup.
Kind regards
J
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« Reply #29 on: July 23, 2005, 02:00:12 PM »
Earlier I wrote: "I very much respect your observations about the Schoeps MK 2H and the CMC 6. Of course there is very much difference between the DPA 4003 130V and the Schoeps P48 Colette series. I wonder only how much psychology is involved in how you describe the differences in grey and black colours, since the Schoeps Colette series have Nextel grey housings, and the DPA mikes are matblack."
And Mark Lemaire replied: "If you 'respect my observations', please prove that by trusting that I know better than to assume that a grey mic will 'sound' grey or a black mic 'sound' black."
I worked 24 years ago for the first time with Schoeps, and 20 years ago with B&K. Although I hear clear differences in the bass, I cannot make myself a picture what a greyish or black sound in the bass means. The only remark I can make about the difference in bass between the DPA 4003 and Schoeps CMC - MK2(s), is the Schoeps capsules in general are a bit more colourised in the Great Octave.
About the "hearing in colours", I once described the loss of HF of a converter in stead of dark, as purple, untill I found out later this converter model had a purple stripe on it's front, which I had not noticed before. From that moment I had doubts about my findings. I must have seen the purple stripe, even when I did not remember it. I prefer rather words like dark, dull, bright for the discant, and coloured, thin or fat for the lower octaves instead.
David Satz wrote:"Erik, if I remember correctly you often make organ recordings with pressure (omnidirectional) transducers. You'd be one of the relatively few people to whom the difference in the infrasonic filters between the CMC 5 and the CMC 6 might matter. I'd assume that you would lean toward the CMC 6."
I do not use the CMC6. I may have not been clear, a 12dB per octave highpass filter causes in the high midrange because of phaseshift a different "colour" than a 6 dB per octave highpass filter or no filter at all, and therefore it is also audible on guitar or any other instrument without subsonic tonal information. Therefore I prefer a 6 dB per octave solution like the CMC5, but as far down as possible, 5 hz.
Erik Sikkema
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Bill Mueller:"Only very recently, has the availability of cheap consumer based gear popularized the concept of a rank amateur as an audio engineer. Unfortunately, this has also degraded the reputation of the audio engineer to the lowest level in its history. A sad thing indeed for those of us professionals."
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