Neumann KM184 + SSL2 = weak signal which requires a lot of gain

[megajonson]

I have a Neumann KM184 SDC mic connected to a SSL2 audio interface through a 10 meter Mogami xlr-cable and notice that it requires me to set the gain to about 7-8 out of 10 to land at levels of about -24 to -18 db. Being aware that mic signals are weak but given that the preamp gain of SSL2 is 62 db I don't expect it to require me to crank it up to about these levels. If I stay at 5/10 I stay at about -40 to 30 db. I believed that the KM184 was rather "hot". Anyone who can calm me or have experience from this mic or audio interface? Unfortunately, the gear is new so I don't anything to compare with or other equipment to test.

 

[Ricardus]

Interesting. I just tested for the first time today, a Neumann KM84 clone that I just built, and on my API clone preamp I didn't have to go beyond 3 or 4 to get tons of gain, and that's an older circuit with less gain than the 184.

 

[Blumlein 88]

Is it the same with both microphone inputs? Also what are you recording, and at what distance?

If you have a smartphone you could probably use a sound level meter app, set the level of a test signal and we can help you puzzle out if the microphone/SSL combo is putting out about the right signal levels.

The KM184 is rated for 15 millivolt output (36 dbV) at 1 khz at 94 db SPL . This is about what most condenser microphones put out in general.

PS-welcome to ASR as it looks like your first posting.

 

[Ricardus]

In general, for questions about recording equipment you might want to join GroupDIY. It basically specializes in recording equipment, and there are lots of mic specialists there.

 

[Blumlein 88]

Here is a possible test. Your microphone should output 1.56 millivolts at 74 db SPL at 1 khz or about 1 millivolt at 70 db SPL. If you use a 1 khz tone you have standing waves and the level will vary several db just moving it over a few inches. However, if you use white noise and filter out everything below 900 hz and above 1100 hz it will be close enough and no standing wave problem. I can provide that test signal if you need it.

So play such a filtered noise test tone and adjust to 70 db using a good smart phone SPL app. Especially easy if you have an iPhone. Put the microphone at the same position you had the phone using SPL software. Probably should be at least 2 meters (7 ft) from the speaker you use. With full microphone gain you should be 2 or 3 db below 0 db on your SSL2 unit. Some assumptions are made and it is approximate, but you'll know if you are far off of what it should be.

My thinking is 1 mV from the KM184 at 70 dbSPL with 62 db of gain is an input to the SSL2 of 1.26 volts. The maximum input of the SSL2 microphone input is supposed to be 1.46 volts according to specs. You could try it at 60 dbSPL first to see if you get -11 or -12 db on the meters.

 

[megajonson]

Is it the same with both microphone inputs? Also what are you recording, and at what distance?

If you have a smartphone you could probably use a sound level meter app, set the level of a test signal and we can help you puzzle out if the microphone/SSL combo is putting out about the right signal levels.

The KM184 is rated for 15 millivolt output (36 dbV) at 1 khz at 94 db SPL . This is about what most condenser microphones put out in general.

PS-welcome to ASR as it looks like your first posting.

Thank you for your elaborate reply below. I am recording voice and keep a normal distance of about 16 cm or 6 inches. I am speaking with moderate voice. I have tried the other input jack as well with the same result. When recording into Logic Pro I get the output metering to be about -30 db when at 5/10 on the gain knob, then -24 db when at 7/10 and finally -16 at 8/10.

Thanks. I will continue on your other reply below.

 

[megajonson]

Here is a possible test. Your microphone should output 1.56 millivolts at 74 db SPL at 1 khz or about 1 millivolt at 70 db SPL. If you use a 1 khz tone you have standing waves and the level will vary several db just moving it over a few inches. However, if you use white noise and filter out everything below 900 hz and above 1100 hz it will be close enough and no standing wave problem. I can provide that test signal if you need it.

So play such a filtered noise test tone and adjust to 70 db using a good smart phone SPL app. Especially easy if you have an iPhone. Put the microphone at the same position you had the phone using SPL software. Probably should be at least 2 meters (7 ft) from the speaker you use. With full microphone gain you should be 2 or 3 db below 0 db on your SSL2 unit. Some assumptions are made and it is approximate, but you'll know if you are far off of what it should be.

My thinking is 1 mV from the KM184 at 70 dbSPL with 62 db of gain is an input to the SSL2 of 1.26 volts. The maximum input of the SSL2 microphone input is supposed to be 1.46 volts according to specs. You could try it at 60 dbSPL first to see if you get -11 or -12 db on the meters.

Truly thankful for your suggestion but it took me a while to understand. Not sure I fully got it right, but I believe I was able to create a white noise test tone limited to 900-1100 Hz in Tone Generator and WavePad from NCH. Then playing it through my external speakers, raising volume to reach 70 db about 2 meters away from the speakers measured with my iPhone SPL meter by David Bannach. Then recording with the microphone from the same spot and distance having the mic gain set to max (10). Then I get the enclosed result from my multimeter in Logic Pro and also from the wave-file recorded and opened in Wavepad. Not sure how to conclude it all, but it seems the meters peak at -7,5 db rather than -2 or -3 or isn't it the RMS value I should be looking for?

What I think is strange is that almost nothing happens when increasing the gain on the interface from 0 to 5 and then between 8 and 10 it goes from acceptable to clipping. I would expect the gain to be more linear.

As mentioned earlier I did check both xlr-inputs and also that the instrument button is not enabled (which I assume works as a pad and lower the signal). I am not sure if there's any reason to measure the voltage from the cable connected to the mic jack to see that it actually delivers 48V phantom power.

 

[megajonson]

In general, for questions about recording equipment you might want to join GroupDIY. It basically specializes in recording equipment, and there are lots of mic specialists there.

Thanks, I wasn't sure where to post, but tried this being a newbie...

 

[Ricardus]

Thanks, I wasn't sure where to post, but tried this being a newbie...

There are plenty of recording guys here too, like me and Blumlein, but this site is more for home hifi. GroupDIY is great for pro audio. I'm over there too with the same handle and profile pic.

 

[Blumlein 88]

Truly thankful for your suggestion but it took me a while to understand. Not sure I fully got it right, but I believe I was able to create a white noise test tone limited to 900-1100 Hz in Tone Generator and WavePad from NCH. Then playing it through my external speakers, raising volume to reach 70 db about 2 meters away from the speakers measured with my iPhone SPL meter by David Bannach. Then recording with the microphone from the same spot and distance having the mic gain set to max (10). Then I get the enclosed result from my multimeter in Logic Pro and also from the wave-file recorded and opened in Wavepad. Not sure how to conclude it all, but it seems the meters peak at -7,5 db rather than -2 or -3 or isn't it the RMS value I should be looking for?

What I think is strange is that almost nothing happens when increasing the gain on the interface from 0 to 5 and then between 8 and 10 it goes from acceptable to clipping. I would expect the gain to be more linear.

As mentioned earlier I did check both xlr-inputs and also that the instrument button is not enabled (which I assume works as a pad and lower the signal). I am not sure if there's any reason to measure the voltage from the cable connected to the mic jack to see that it actually delivers 48V phantom power.

Julian Krause reviewed the SSL 2. He measured 55 db of gain on the microphone preamps. SSL claims 62 db.

You can see that just past 9:15 in this video.

So adding 6 or 7 db to your result that all lines up pretty close. Considering the inexact method that makes me think the SSL and the Neumann are both operating fine.

Just as something of a crosscheck, using a microphone with the same sensitivity rating I end up running it around 36-40 db gain for singers who are a couple feet away, and somewhere around 50 db for someone just talking. Although I have not recorded much speaking or talking.

As for the action of the gain knob, that sounds bothersome. If it were a log taper, the difference in 5 and 10 would be 6 db and the difference in 2.5 and 5 would be 6 db. So you'd have a touchy gain knob at low levels and one easily controlled in the upper half of its range.

 

[Rja4000]

I am recording voice and keep a normal distance of about 16 cm or 6 inches. I am speaking with moderate voice.

Well...
Normal speech level is between 54dB SPL and 60dB SPL at 1m.
At 16cm, that's between 70dB and 76dB SPL.
A KM184 has a sensitivity of 15mV/Pa.
Or 15mV for 94dB SPL.
If we have a level of, say, 74dB SPL (to keep it simple), that means we have around 1.5mV at the mic preamp input. Or -54dBu.
That's low.

The max input level of the SSL 2 (as per the user manual) is +5.5dB.
To reach 5.5dBu with a signal around -54dBu, you need to push by approximately 60dB.
(Or 40dB to keep level around -20dBFS)
The SSL 2 has a maximum gain of 62dB, so it's not surprising at all that you have to push your gain seriously.

Why do you keep the microphone so far away ?
And why to use a KM184 to record voice, to begin with ?

 

[Rja4000]

In general, for questions about recording equipment you might want to join GroupDIY. It basically specializes in recording equipment, and there are lots of mic specialists there.

Why do you send a new user elsewhere ?

 

[Ricardus]

Why do you send a new user elsewhere ?

I am informing them of a specialty site. You know. Being a NICE HELPFUL HUMAN BEING????

ASR doesn't have the market cornered on audio sites.

Why are you bothered by this is a better question? When people ask HiFi questions on GDIY I send them here. Haven't seen anyone complain over there.

 

[Ricardus]

And why to use a KM184 to record voice, to begin with ?

People use SDC's all the time for voice. This isn't surprising at all.

 

[Rja4000]

ASR doesn't have the market cornered on audio sites.

For sure not. But it's... surprising.
Sending a new user, asking his very first question, to another web site ... as soon as post #4...

Given the type of question, I think we can (and did) pretty easily answer his question.

And now he seems to be gone.

 

[Rja4000]

People use SDC's all the time for voice. This isn't surprising at all.

Well, the KM184 is not the first tool that comes to mind for that.
Especially for its price.
Now he may have other uses for it.
(I do own and use a pair of KM184)

 

[dfuller]

Probably using an audio taper pot. Chances are good that like 60% of the gain is in the last 1/4 of the pot's rotation.

 

[megajonson]

Julian Krause reviewed the SSL 2. He measured 55 db of gain on the microphone preamps. SSL claims 62 db.

You can see that just past 9:15 in this video.

So adding 6 or 7 db to your result that all lines up pretty close. Considering the inexact method that makes me think the SSL and the Neumann are both operating fine.

Just as something of a crosscheck, using a microphone with the same sensitivity rating I end up running it around 36-40 db gain for singers who are a couple feet away, and somewhere around 50 db for someone just talking. Although I have not recorded much speaking or talking.

As for the action of the gain knob, that sounds bothersome. If it were a log taper, the difference in 5 and 10 would be 6 db and the difference in 2.5 and 5 would be 6 db. So you'd have a touchy gain knob at low levels and one easily controlled in the upper half of its range.

Thanks, it feels a bit reassuring. I believe the fact that I am not experienced with phantom powered mics was making me doubtful. Having both a new mic, interface and cable didn't help not making me think something is wrong. I have just watched Julians video and I also looked at his gain when speaking into the SM7B and also in other parts of the video. He seems to be hitting the 9 mark for the SM7B and then around 8 for his other voice over (he seems have the mic from a distance outside the picture). I also noticed his other video on not being afraid to use the gain... But when doing the unscientific thing of going from 0-10 and pronouncing the values, nothing happens from 0-1, 2-4 gives about -55 o -54 and 5 -42, 6 -37, 7 -31, 8 -20 and 9 happened to show -2,5 and 10 -4,8. Of course the pronunciation as well as my turning is not exact and I guess that when reaching the end one is afraid to peak and maybe unintentionally lower the voice. I was informed from an acoustic guitar player on YouTube who used KM184 and the SSL2 that he had it at about 6 or 7 on a distance of 14", but I assume a guitar is louder than spoken word. Thanks for all the help.

 

[megajonson]

Well...
Normal speech level is between 54dB SPL and 60dB SPL at 1m.
At 16cm, that's between 70dB and 76dB SPL.
A KM184 has a sensitivity of 15mV/Pa.
Or 15mV for 94dB SPL.
If we have a level of, say, 74dB SPL (to keep it simple), that means we have around 1.5mV at the mic preamp input. Or -54dBu.
That's low.

The max input level of the SSL 2 (as per the user manual) is +5.5dB.
To reach 5.5dBu with a signal around -54dBu, you need to push by approximately 60dB.
(Or 40dB to keep level around -20dBFS)
The SSL 2 has a maximum gain of 62dB, so it's not surprising at all that you have to push your gain seriously.

Why do you keep the microphone so far away ?
And why to use a KM184 to record voice, to begin with ?

Hi, no I also get the understanding that I would probably have to have a high gain. But as mentioned I believed the gain was to be more linear and that the mic was more sensitive having read about plosives etc (I am using a pop shield) and when I see people using it for spoken word it seems to be even further away than many LDC's. I get about nothing from 1-5 on a gain knob scale of 10. I picked the KM184 as I have heard it on spoken word and it sounds very natural compared to many what I believe are bass boosted mics (not sure about the terminology here). In fact, it's used by Swedish Radio on their daily news channel where they only have spoken word. Their other household mic is the Microtech Gefell M930 but it's even pricier and I think that the KM184 sounds more neutral. Thanks for the reply.

 

[megajonson]

For sure not. But it's... surprising.
Sending a new user, asking his very first question, to another web site ... as soon as post #4...

Given the type of question, I think we can (and did) pretty easily answer his question.

And now he seems to be gone.

No worries, I didn't take it that way. I am glad for all the input I have received on this post. You seem all very technically experienced. Bare with me, I guess it's the time difference to Sweden...