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Neumann KM-D Digital Microphones

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Neumann KM-D Digital Microphones

Postby John Willett » Sat Feb 24, 2007 8:33 pm

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INTRODUCTION

This is not intended as a review, as Hugh Robjohns has already done an excellent review of the KM 184-D in the March 2007 issue of SOS HERE. Also, as Sennheiser UK pay my salary, you will obviously think any review as biased.

However – here I am taking off my Sennheiser/Neumann hat and putting on my Circle Sound Services hat to say why I invested my own money in a pair of KM 183-D omnis and a DMI-2 interface and will describe the start of an ongoing recording project using them. So I am sticking to facts and a description of how I used them.

I went over to Neumann, Berlin in November 2006 to be shown the new range and initially was thinking – digital microphones, great, but…..

However, I was forgetting about all the headroom that you have to allow for with analogue microphones. Headroom in the microphone pre-amplifier (and the additional noise in the analogue circuit) and the headroom you have to allow in the D/A converter. These two added together mean there is about a 25dB reduction in the s/n ratio – so, a 130dB dynamic range gets reduced, in effect, to only 105dB. That was point #1 that started me sitting up and listening.

The A/D in the Solution-D series (including the KM-D) is a patented Neumann true 28-bit conversion that gets the full dynamic range of the microphone – this is outputted as a 24-bit signal in the AES42 format. The interface controls the microphones and outputs the signal as standard AES3. Details of all this – AES42, Stephan Peus’s paper on digital microphones and product brochures can all be downloaded in pdf format from the Neumann website HERE.

Once the signal is in the digital domain in the microphone you can adjust the level, add compression, pre-attenuation, etc., even switch the microphone's power light on and off or change the brightness. This is all controlled by the Neumann RCS software included with the DMI-2 (see channel strip below).

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And there is a lot more you can do in the digital domain in the microphone. Most important (and convincing point #2 for me) is the inclusion of an integral digital limiter that prevents overload. On a test with a microphone with this disabled, is was very clear how effective this limiter is. No distortion at all, it just does not get any louder. Great for transients that would normally distort the recording and require a re-take – now it’s just perfect.

Those are the main reasons why I immediately put my own money on the table and bought my own pair and I have also put my name on the top of the list for the new KK 131-D flat-omni (nearfield) capsules when they come out.



THE PROJECT

I have been asked to record a series of CDs for the pianist, Richard Meyrick. I have recorded Richard many times over the years, normally with Sennheiser MKH 20 omnis – but this time I also used the new Neumann KM 183-D digital microphones.

The project is sponsored by The Man Group and Blüther pianos, so our hands were not tied to get a good sound.

The recording venue was The Menuhin Hall in the Yehudi Menuhin School in Stoke d’Abernon. This is a superb building with a great sound. It is totally isolated from outside noise with a perfect cable route to the Green Room where we set up the recording equipment.

AES42 signals can only travel about 10-metres along normal microphone cable, so I went along to Canford Audio and got them to make me some custom cables (yes, I know - I’m lazy and I am not proficient with lead-free solder yet) made with proper balanced AES digital audio cable, terminated with the new Neutrik EMC XLR connectors. AES42 at 24/96 can travel about 200-metres along these cables, so distance was not a problem.

As this was my first outing with the KM-D series, I did a parallel recording with a pair of MKH 20s (as you can see in the picture).

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The microphones were set up as shown in the photo (just click on the picture to get the large version). As the KM 183-D is a diffuse-field omni, it has a lift in the upper frequency range. But I had the microphones only about a couple of metres from the piano. Anyone who has seen a polar-pattern of an omni microphone knows how the high frequencies are attenuated off-axis due to the physical size of the microphone. We started with having the 183-Ds at about 45°, but found this was still a bit too bright; so we turned them through 90° and had them vertical. At this position the frequency response was ruler flat and the piano sounded great (the MKH 20s didn’t need turning as they have a flat response head on).

The KM 183-Ds were connected to the DMI-2 interface which locked them to the same clock time. They were set to a 96kHz sample rate and a digital gain of 25dB was applied (in practice this was fine as the absolute maximum peak ended up being about -1.6dBFS – I ended up not needing the limiter at all). I did not apply any compression at all.

The output of the DMI-2 was fed to an AES splitter which outputted to a Fostex FR-2 for the main recording at 24/96. The second output went to an Audio Design ProBox 10 sample rate converter which down-converted to 16/44.1 to record a DAT safety copy on my old Fostex D-10. The MKH 20s went to an Audio Design DMA2 24/96 mic. pre. and into a second FR-2 (kindly loaned by SCV London for the event).

Monitoring was via a Grace m902, Sennheiser HD 650 headphones and Klein + Hummel O110 active monitors (as shown in the picture – again, click the image to get the large version). Talkback was via my custom unit (made by myself many years ago) which also controlled the red lights. I also used “The Box” for stereo soundstage imaging.

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The first recording session was five consecutive days just before Christmas ’06. The sessions went extremely well and the microphones behaved flawlessly. We were delighted with the results.

The KM-D microphones are so quiet that we had no background noise “clue” when we were playing back. We kept thinking something was wrong, as every time we started to play back a take we couldn’t hear anything – until the music started. They are quiet!

The sound of the microphones is the sound of the capsules with nothing added and nothing taken away. Once we had tamed the top end by angling the microphones correctly, everything was wonderful.

Earlier this year, we spent a weekend with Samplitude9 on the PC, editing most of the sessions and the pianist and sponsors are absolutely delighted with the results.

We are going back for the next sessions just before Easter and a CD of Chopin music should be released mid year. We have more sessions booked and further CDs will follow later.

Yes – we chose the KM 183-D microphones for the release (not that the MKH 20s weren’t good – but this combination was the best one in this situation).

I don’t spend my own money lightly - probably something to do with my Scottish great-grandmother ;) - and I certainly have no regrets in doing it this time.

In fact the KM 183-Ds work out quite cheap – including the interface, a pair works out at about the same price as any top class omni (slightly cheaper than a pair of MKH 20s) – but when you factor in that you don’t need a mic. pre. or A/D, or even a limiter / compressor...

And - when the mixer and DAW manufacturers come out with AES42 inputs on their equipment, you won't even need the interface.

All in all, I'm delighted and plan to add to the system as it is expanded over the next year or two.

(Forget I work for Sennheiser - this is my own money I'm spending here - no regrets, it's great)
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Re: Neumann KM-D Digital Microphones

Postby TImellis » Sat Feb 24, 2007 9:18 pm

Many thanks for that John - honest & unbiased - just like the recording turned out, eh? :bouncy:
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Re: Neumann KM-D Digital Microphones

Postby tea for two » Sat Feb 24, 2007 9:23 pm

Concise & easy to understand review JW.

Thank you.
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Re: Neumann KM-D Digital Microphones

Postby John Willett » Sat Feb 24, 2007 9:56 pm

TImellis wrote:Many thanks for that John - honest & unbiased - just like the recording turned out, eh? :bouncy:

As honest and unbiased as I can be.

I liked the mics. I bought them with my own money - and this is how I used them.

Yes, it can be difficult when you are writing about something made by your employer - but if something excites me I want to talk about it; and this excited me so much I spent my own money on it.

For a review that is totally unbiased, read Hugh Robjohn's review - you can take this how you wish.

But I liked them so much I bought them myself.

What I write I believe - negatives I may leave out, but I honestly couldn't find any with these, other than the brightness which I fixed with moving them to the best angle for the best results.

And my customer is so delighted that he plans on a 3,000 production run for the CDs. :D
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Re: Neumann KM-D Digital Microphones

Postby Aural Reject » Sun Feb 25, 2007 12:47 am

Very nice, John.

I'm looking forward to hearing them :lol:
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Re: Neumann KM-D Digital Microphones

Postby TImellis » Sun Feb 25, 2007 1:07 am

I hope you didn't think there was any sarcasm intended, John, in my post - not at all - you came across totally honest and unbiased.
Would you predict a time when digital microphones become the norm?
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Re: Neumann KM-D Digital Microphones

Postby Hugh Robjohns » Sun Feb 25, 2007 1:31 am

TImellis wrote:Would you predict a time when digital microphones become the norm?

They'll never become the norm, but they will become a lot more common and even mainstream -- particularly in classical and serious music recording circles.

But there will always be those who want to stay with analogue because they like the limitations of that technology. They like the distortions, and they like the 'black art' of choosing mic preamps and A-D converters to create a particular sonic character. You can't do that with digital mics, and especially not with mics as good as Neumann's Solution D series.

John is quite right, the KM-D mics are stunning in every way, and I am sorely tempted to buy a pair myself but can't really justify it at present.

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Re: Neumann KM-D Digital Microphones *DELETED*

Postby John Willett » Thu Sep 13, 2007 1:57 pm

John,

I amended the IMG tags to show the missing 2 pictures so have removed this secondary post.

ian G
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Re: Neumann KM-D Digital Microphones

Postby John Willett » Thu Sep 13, 2007 2:04 pm

As a postscript - I have now ordered a pair of the new KK 131 flat-omni heads for the KM-D system.

And if anyone else is using the Neumann Digital microphone systems there are firmware upgrades downloadable from the Neumann website.
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Re: Neumann KM-D Digital Microphones

Postby Hugh Robjohns » Fri Sep 14, 2007 10:13 am

John Willett wrote:What I write I believe - negatives I may leave out, but I honestly couldn't find any with these, other than the brightness which I fixed with moving them to the best angle for the best results.

That makes it sound like the mics are inappropriately bright, which isn't the case. These particular capsuels were intended for diffuse field use adn John didn't want to use them that way, hence having to correct the response by turning them off axis. Neumann has now produced direct field omni capsules, and the fact that the off axis response of the originals sounded so good is a testament to the quality of the original capsule design.

I have to agree with John that the KM-Ds are phenomenally good mics, and althoguh they appear expensive initially, when you look at all the other things you no longer need in your recording chain, they are actually very good value for money. It was only the whispers of a similar Sennheiser system in the near future that disuaded me from buying the KM-Ds myself.

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Re: Neumann KM-D Digital Microphones

Postby RegressiveRock » Sat Sep 15, 2007 12:26 am

John Willett wrote:It seems the hosting site has removed a couple of the pictures I posted on the original review.

As I can't edit it to reallocate them - I am posting the missing pictures here:-

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Nice to see your stereo image box gets a regular outing John... ;)
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Re: Neumann KM-D Digital Microphones

Postby John Willett » Sat Sep 15, 2007 1:37 pm

RegressiveRock wrote:
Nice to see your stereo image box gets a regular outing John... ;)

Of course, it's excellent and invaluable - I use it on every recording session.

If you want one you get it from Mike Ballance (yes, that *is* his real name) at Tabor Audio.

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Re: Neumann KM-D Digital Microphones

Postby Hugh Robjohns » Sat Sep 15, 2007 6:22 pm

The Box is quite useful once you've learned how to interpret it (which doesn't take that long), and it is quite cost effective.... but the DK-Technologies meters are soooo much better and do sooo much more..
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...but they do cost a lot more! ;)

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Re: Neumann KM-D Digital Microphones

Postby John Willett » Sat Sep 15, 2007 8:39 pm

Hugh Robjohns wrote:The Box is quite useful once you've learned how to interpret it (which doesn't take that long), and it is quite cost effective.... but the DK-Technologies meters are soooo much better and do sooo much more..

....but they do cost a lot more! ;)

I agree - but five times more (and more). :frown:

I would have got one if they were cheaper.
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Re: Neumann KM-D Digital Microphones

Postby Hugh Robjohns » Sat Sep 15, 2007 11:47 pm

John Willett wrote: I agree - but five times more (and more). :frown:

I would have got one if they were cheaper.

But it does do five times as much!

Bargraph level meters with selectable scales and true peak indicators

Spectrum analysis as 1/3 octave RTA or FFT

Phase meter

Lissajous display (goniometer)

Surround jellyfish/starfish displays (on the surround meters)

Routing matrix

test tone generator

Loudness measuring

Digital fault logging

Stereo Downmixing (for surround version)

...and more.

It's not that I'm a huge fan or anything..... and other metering systems are available ;)

And yes, I did have a BOX too, but I stopped using it and gave it to a friend.

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