Help needed -- my pair of AKG C451B is really noisy

[JoeCharter]

Hi folks,

I grabbed a pair of C451Bs yesterday and was all excited to try them out.

However, I quickly realized they caused more noise than my old and cheap AT3035.

Perhaps I'm the nincompoop who doesn't know how to use these, but here's my attempt at recording a track last night:

https://soundcloud.com/syndicatedart...-mhor-kraut-om

Notice the annoying background noise at the end of the track. I couldn't turn up the mic level much higher.

In comparison, I think I had a much more dynamic (and quiet) recording with my AT3035:

https://soundcloud.com/syndicatedart...mprovisation-3

Any insight as to what I may be doing wrong would be appreciated. Otherwise I may well return these small microphones and get a keyboard instead...

Thanks for your help.

[rick-slo]

The two are about equal in the usual mike self noise, both being low and quite acceptable. In the C451Bs there is a sound of something like blowing wind.
Here is just the end of the recording where you can hear it:

http://dcoombsguitar.com/Guitar%20Music/Temp/Temp0.wav

I don't think that wind sound is coming from the mikes directly. You might try recording a few seconds with no guitar playing and listening to the nature of what noise might be there.


I assume you faded the ending.

[JoeCharter]

Originally Posted by rick-slo

The two are about equal in the usual mike self noise, both be low and quite acceptable. In the C451Bs there is a sound of something like blowing wind.

Thanks for your feedback, Rick.

Yes it does sound like "wind" indeed. However when I compared the two microphones, I could crank up the AT3035 way higher without catching any "wind". Perhaps they are not sensitive to the same frequencies.

[rick-slo]

Did you record where there was any possible breeze (outside, air conditioning) or something going on in the background that could have made that noise.

[sdelsolray]

Four things.

1) The self noise (A weighted) is higher on the AKG 451B (18 dB) than the AT 3035 (12 dB). All other things being equal, the AKG will sound more noisy. 18 dB is about the upper limit for an A weighted self noise spec for my uses for solo fingerstyle acoustic guitar. The lower the better.

2) The sensitivity of the AKG 451B is lower than that of the AT 3035. You need more preamp gain with the AKG than the AT. This has the potential of adding noise from the preamp.

3) The frequency response of the AKG has a medium wide 4-5 db high frequency lift at about 10k - 12k Hz. The AT is more or less flat at these frequencies but starts a 5 dB dip at 15k Hz. All other things being equal, the AKG will sound noisier because of these HF differences.

4) Even with identical specs, the sound of the noise often varies from mic to mic. Some sound noisier than others because the frequencies emphasized in the noise are different.

Some ideas to mitigate the noise:

1) Move the mics a bit closer which will allow for lower preamp gain.

2) Apply an EQ filter at mixdown to tame the HF rise of the AKG mics. See the frequency response below and apply a filter which reverses the HF rise.

AKG 451B Frequency Graph

Upon listening to the sample, that "wind" noise is not normal mic noise.

[JoeCharter]

Originally Posted by rick-slo

Did you record where there was any possible breeze (outside, air conditioning) or something going on in the background that could have made that noise.

My home was dead quiet. There was wind outside -- but nothing that my ear could pick up (and nothing that the AT could pick up).

Thanks for sharing your thoughts, Rick.

[JoeCharter]

Originally Posted by sdelsolray

Four things.

1) The self noise (A weighted) is higher on the AKG 451B (18 dB) than the AT 3035 (12 dB). All other things being equal, the AKG will sound more noisy. 18 dB is about the upper limit for an A weighted self noise spec for my uses for solo fingerstyle acoustic guitar. The lower the better.

2) The sensitivity of the AKG 451B is lower than that of the AT 3035. You need more preamp gain with the AKG than the AT. This has the potential of adding noise from the preamp.

3) The frequency response of the AKG has a medium wide 4-5 db high frequency lift at about 10k - 12k Hz. The AT is more or less flat at these frequencies but starts a 5 dB dip at 15k Hz. All other things being equal, the AKG will sound noisier because of these HF differences.

4) Even with identical specs, the sound of the noise often varies from mic to mic. Some sound noisier than others because the frequencies emphasized in the noise are different.

Some ideas to mitigate the noise:

1) Move the mics a bit closer which will allow for lower preamp gain.

2) Apply an EQ filter at mixdown to tame the HF rise of the AKG mics. See the frequency response below and apply a filter which reverses the HF rise.

AKG 451B Frequency Graph

Upon listening to the sample, that "wind" noise is not normal mic noise.

Thanks so much for this. I had sort of assumed some of these ideas and I'm glad to see them validated by you.

If I only record fingerstyle guitar (no loud strumming), would you think that the AKG C451B might not be for me?

[rick-slo]

Originally Posted by JoeCharter

My home was dead quiet. There was wind outside -- but nothing that my ear could pick up (and nothing that the AT could pick up).

Thanks for sharing your thoughts, Rick.

Mikes pick up things you would never notice live but that you do notice in quiet spots in the recording. Again, with the gain at the same level as used in the recording above, record a few seconds of just the room (without playing). Post that if you are hearing noise.

Also listen to this guitar recording using AKG C451B mikes - no wind noise

http://www.youtube.com/watch?v=BuUE-lUYEKs

[sdelsolray]

Originally Posted by JoeCharter

Thanks so much for this. I had sort of assumed some of these ideas and I'm glad to see them validated by you.

If I only record fingerstyle guitar (no loud strumming), would you think that the AKG C451B might not be for me?

I can't say whether a pair of AKG451B would work best for you. I do know that they don't work best for me. I would suggest that you actually try several different mics in your studio, with your guitars, other recording gear and music to see what you like best. That's the only way to be sure. Keep in mind that the "wind" noise from your clip is not a normal sound from any mic (unless the "wind" noise is an actual ambient noise from your environment), so it might be best to solve that problem first and then evaluate the AKG 451B mics.

In that $1,000+-/pair price range, you might want to check out (in no particular order):

1) Used Neumann KM184;
2) Beyer Dynamic MC930 (or MC940);
3) Michael Joly modified Oktava MC-012 with a second set of capsules;
4) 3 Zigma CHI with a second set of capsules;
5) Shure SM81;
6) Used Microtech Gefell M300.

Getting another AT 3035 could likely be a good choice. That mic has a mid-sized diaphragm (19mm), so it is between a SD and a LD in terms of noise and behavior. Personally, I like many mid-sized diaphragm mics for solo fingerstyle, although there aren't many different ones out there. Two possible choices here are the Peluso P28 and Microtech Gefell M295, both of which are unfortunately above the $1,000/pair price point.

[JoeCharter]

Originally Posted by rick-slo

Mikes pick up things you would never notice live but that you do notice in quiet spots in the recording. Again, with the gain at the same level as used in the recording above, record a few seconds of just the room (without playing). Post that if you are hearing noise.

Also listen to this guitar recording using AKG C451B mikes - no wind noise

http://www.youtube.com/watch?v=BuUE-lUYEKs

OK thank you. I will post something in the evening.

[JoeCharter]

Actually I managed to find a few minutes to put these together.

Mic level set at 55 on the Duet.

AKG: https://soundcloud.com/syndicatedart...-noise/s-dUBw0

AT: https://soundcloud.com/syndicatedart...-noise/s-Cr1m9

[rick-slo]

Originally Posted by JoeCharter

Actually I managed to find a few minutes to put these together.

Mic level set at 55 on the Duet.

AKG: https://soundcloud.com/syndicatedart...-noise/s-dUBw0

AT: https://soundcloud.com/syndicatedart...-noise/s-Cr1m9

I hear some background noise (computer?) in both clips. In a recording that can sound vary depending on the exact position of the mikes in the room.
I do think it is the environment and not inherent in the mikes.

[sdelsolray]

Originally Posted by JoeCharter

Actually I managed to find a few minutes to put these together.

Mic level set at 55 on the Duet.

AKG: https://soundcloud.com/syndicatedart...-noise/s-dUBw0

AT: https://soundcloud.com/syndicatedart...-noise/s-Cr1m9

That certainly sounds like ambient noise from inside or outside of your studio space. Both mics pick it up.

Nitpick: setting the input gain on your preamp the same for each mic does not guarantee that the sound is recorded at the same volume. Those two mics have different input sensitivities, which guarantees that the sound files will not be at the same volume.

[JoeCharter]

Thanks so much for your help, guys.

I will keep experimenting.

[JoeCharter]

Originally Posted by sdelsolray

That certainly sounds like ambient noise from inside or outside of your studio space. Both mics pick it up.

Nitpick: setting the input gain on your preamp the same for each mic does not guarantee that the sound is recorded at the same volume. Those two mics have different input sensitivities, which guarantees that the sound files will not be at the same volume.

Yes I understand your latter point.

I set the level the same just for comparison purposes.

When I recorded with the AT, I set the level much lower (no noise).

I do like the airiness of the AKG but there's no way I can drive these to decent levels in this environment without audible background noise.