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Gear / Technical Help => Battery Boxes, Preamps, Mixers, ADCs, and Processors => Topic started by: larrysellers on March 23, 2009, 07:20:04 PM
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Do you have to use an ak20 with this box? I see that they make a Y cable (AC-30) but can it be used to run a stereo pair(ak40 x 2)?
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You can bypass the M/S matrix in the MTX 191 and simply power any two Neumann active capsules on extension cables. The actual setup can be X/Y, near-coincident (e.g. ORTF) or even A/B if you want.
The output stage of the matrix box is similar to the output stages of two KM 100-series microphone bodies, while the RSM 190/191 stereo microphone is somewhat like having two active capsules.
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Anyone have any pics?
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No pic, but found this show: http://bt.etree.org/details.php?id=523666
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(http://img525.imageshack.us/img525/3221/ac30.gif) (http://img525.imageshack.us/my.php?image=ac30.gif)
(http://img299.imageshack.us/img299/3882/rsm191z.jpg) (http://img299.imageshack.us/my.php?image=rsm191z.jpg)
(http://img299.imageshack.us/img299/6217/neummtx191a.jpg) (http://img299.imageshack.us/my.php?image=neummtx191a.jpg)
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wow that's cool. so it replaces the bodies and also acts as a preamplifier. http://www.bhphotovideo.com/bnh/controller/home?O=&sku=146408&Q=&is=REG&A=details#features $1200 + 16.5' cable http://www.bhphotovideo.com/bnh/controller/home?O=&sku=239444&is=REG&A=details&Q= $389
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No "flat" option? All HPF?
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> so it replaces the bodies and also acts as a preamplifier.
No, it replaces the bodies and also acts as a battery power supply. The outputs are at (professional condenser) microphone level, not line level.
> No "flat" option? All HPF?
The switch has three positions. In the middle is "LIN" (for "linear" response).
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>whats the difference: The outputs are at (professional condenser) microphone level, not line level.
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NOLAfishwater, while line levels in U.S. professional audio are generally +4 dBu (= ca. 1.2 Vrms), consumer line (or "aux") levels are typically referenced to -10 dBV (= ca. 0.3 Vrms).
Professional condenser microphones generally have lower output levels than that. Take the original Neumann U 87--the prototypical studio condenser microphone; its maximum output voltage is only about 200 mV. Driving it to a -10 dBV output level would require about 126 dB sound pressure, which is more than the microphone can handle. Its more recent counterpart, the U 87 Ai, has an even lower maximum SPL capability. 126 dB SPL just isn't a typical studio recording level, though some microphones can certainly handle it; 126 dB is scary loud.
So while it's not an enormous difference and there are definite exceptions (e.g. Neumann's "M 149 Tube" microphone can apparently put out 6-Volt signals, with a nominal sensitivity of 62 mV/Pa in its figure-8 setting), microphone levels in general are lower than line levels in general, to the extent where professional condenser microphone levels are higher than consumer microphone levels, but are still generally lower than consumer line levels.
--best regards
P.S.: If you connect the balanced output of a professional microphone to an unbalanced input by leaving one of the modulation leads unconnected, then depending on the output circuit of the microphone you may well be throwing away 6 dB of signal level, which makes the difference even greater.
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Mr DSatz, you are a wealth of knowledge. Thank you for all the great info.
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thank you for your detailed response. that would explain why some people have to run an attenuator between mics and preamp.
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thank you for your detailed response. that would explain why some people have to run an attenuator between mics and preamp.
Because the mic capsules can put out under very high spl conditions more voltage then the ( mic body )preamps input can handle. Or the output of the mic is overloading the mic input stage of your mic preamp. Take your pick it will be one of the two.
Chris
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It's also because there's typically a 10 - 20 dB difference between consumer (dynamic and cheap electret) mike levels and professional (studio condenser microphone) mike levels, and some (many?) people in this forum are recording at rather high SPLs.
A lot of "semi-pro" recording equipment is still designed for consumer mike levels even when it has XLR inputs and phantom powering. Marketing departments seem to add on those two features to give their products automatic "professional" status. When this class of equipment first came onto the market in the 1970s and 80s, companies such as Sony, Panasonic and Tascam (TEAC) designed it for use with electret microphones that had output levels comparable to dynamic microphones, or just a few dB more sensitive. So the microphone input circuits were often limited to handling 50 - 100 mV or thereabouts just as in consumer recording equipment, and this was not seen by the manufacturers as a problem.
These days the typical limit for mike inputs might be around 250 mV, but there are microphones from well-known manufacturers that put out five to ten times as much, and even more at the highest sound pressure levels. To my way of thinking, if microphone inputs can't handle a Volt of input, they shouldn't be considerd professional equipment in modern terms.
--best regards
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You can bypass the M/S matrix in the MTX 191 and simply power any two Neumann active capsules on extension cables. The actual setup can be X/Y, near-coincident (e.g. ORTF) or even A/B if you want.[/quote]
How would you achieve this with the available X/Y settings? Does the result sound like a pair of mics in ORTF or A/B configuration? I'm really curious....
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Hi, jazzunit. On the MTX 191, the switches are labeled on the assumption that you'd be using the Neumann stereo shotgun microphone (originally called the RSM 190, now called the RSM 191 by association with this matrix box--the only difference between the two models). Since that's a coincident stereo microphone, the switch settings are "XY" and "MS."
(The Neumann stereo shotgun actually has three capsules--a central, forward-facing supercardioid with the interference tube in front of it for the "M" channel, plus a pair of cardioids facing to the left and right, connected so that the one on the right subtracts its output from the one on the left, thus synthesizing a figure-8 for the "S" channel.)
If you're using the special adapter cable and two active capsules from the KM 100 series, you can space the capsules apart, and then all you need is to pass the signals through the MTX 191 without dematrixing. It looks to me from the block diagram (attached) as if you'd want to set the switch to "MS" for that, and that also makes sense since the two signals coming from the stereo shotgun would be unmatrixed M and S signals.
Incidentally, I used to own an RSM 190. It was a very good-sounding microphone, but not as highly directional as some people seem to expect or imagine. But I've noticed that people who aren't really familiar with shotgun microphones nearly always imagine them doing what no microphone can ever do: give a recording a nice balance of direct and reflected sound, when the sound sources are so far away that the direct sound at the microphone position is swamped by reflected sound.
--best regards
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Awesome! Thanks for the info. I've always wondered if one could get away with using the MTX191A as simply a replacement for the KM100 bodies. When money permits, I will try this.
Thanks!