LDC mics and preamp question

[Aaron Straley]

I am using an SSL 12 interface. The preamp gain is 62db's. The mic in question, a Warm Audio WA14. Using as a vocal mic, I can get good recordings. When I try to record a quieter source from further away, seems like I need to turn up the preamp knob to beyond 75%, which amplifies the noise floor as well. Its either that or turn up the clip gain in the track. Usually when recording I like to see at least -20 on my channel meter?
I put the Wa14 in figure 8 mode and paired with a SDC for MS recording on acoustic guitar yesterday. Adjusted the gain levels so that both pics were hitting about -20. While the SDC tracks were really clear with no noise, the WA14 seemed to be too noisy. I think this is because I needed to turn up the preamp too high (75-80%) on the WA14.
Do I need a special preamp for the WA14? I just assumed that all mics would work well with the SSL that has 62dbs gain. I gotta say that all my other mics work pretty good with it. Why am I constantly fighting for level with this mic? IS it the MIC or my preamp?
As a result, I'm looking at the KSM44a or the TLM103. From what I've read, these have higher output and lower self noise. I dont want to make another mistake and buy something that is not really working for my set up. I'm definitely trying to avoid purchasing an external preamp (that I only need for one MIC) . In my mind I shouldn't need to because the pre's on my interface should have plenty o gain. Is this assumption correct?

[Wonks]

Probably two things happening here.

1) The preamp level for the WA14 sides mic is probably too high. With proper gain settings, the sides signal will be lower than the mid signal.

2) The sides mic isn’t pointed directly at the guitar, so you’ll be picking up a lot more room noise which you’ll probably interpret as mic or preamp noise.

Try setting the Mid mic up for around -20dBFS peaks. Then rotate the sides mic so one lobe of the fig-8 is pointing at the guitar and set that for a similar level. Then rotate it back by 90°.

The mics should now have roughly equal gain.

Having the sides mic level too high will give you a false starting stereo image.

You should now have less gain on the sides mic than before and the results should sound more natural.

Whilst a guitar does put out different sound from different areas, it’s not much of a stereo instrument, so a lot of the stereo width comes from reflections from the room, which naturally are a lot quieter than the direct sound.

But if the room is noisy, then you will pick up that noise with a fig-8 pattern pointing to the sides, whilst a cardioid is getting a much stronger signal from the front and rejecting noise from the rear.

[James Perrett]

The problem may just be the microphone. The TLM 103 is much quieter than the WA14 and the KSM44 is 4dB quieter than the TLM103. Changing the preamp won't help if you have a noisy microphone.

The other issue is that most rooms are much noisier than people think so you may just be hearing the background noise present in the room.

[Hugh Robjohns]

Using as a vocal mic, I can get good recordings. When I try to record a quieter source from further away, seems like I need to turn up the preamp knob to beyond 75%, which amplifies the noise floor as well.

Well, yes... it would.

A more distant source means a much poorer ratio between wanted sound and room sound. So amplifying the mic will inherently also bring up a lot more room sound.

Also, increased gain will raise the self-noise of the mic itself, as well as the preamp's own self noise. However, the SSL preamp specs indicate it's about as quiet as it can be. In contrast, the WA14, is relatively noisy.

So it's not really a good mic to use for distant placements, especially in an acoustically poor room.

I put the Wa14 in figure 8 mode and paired with a SDC for MS recording on acoustic guitar yesterday. Adjusted the gain levels so that both pics were hitting about -20. While the SDC tracks were really clear with no noise, the WA14 seemed to be too noisy.

Well, yes... it would be!

The Mid mic is getting almost entirely direct sound, peaking -20dBFS. The Sides mic, by definition, gets very little direct sound. It's mostly reflected room sound which you would expect to be very much lower in level — at least10-12dB lower... yet you've turned up the gain so much that it's also peaking -20dBFS. So not surprising that it seems noisy.

Do I need a special preamp for the WA14?

No. The SSL12 preamp is about as quiet as they come.

Your noise problem is a combination of a relatively noisy mic being used in an acoustically poor room, and either too far away or inappropriately.

Why am I constantly fighting for level with this mic? IS it the MIC or my preamp?

It's the mic and the room.

As a result, I'm looking at the KSM44a or the TLM103. From what I've read, these have higher output and lower self noise.

These are both some of the quietest mics on the market.... so you'll definitely have less electronic noise in high-gain applications. But they'll still capture similar levels of room noise, of course (for the same polar pattern).

In my mind I shouldn't need to because the pre's on my interface should have plenty o gain. Is this assumption correct?

Yes.

[Wonks]

The TLM103 is a cardioid-only mic, so not a mids* mic. The KSM44 is multi-pattern, so can be used as a mids* mic.

*should say 'sides'.

[Wonks]

No valves in a WA14 mic, Hugh, it's a brass capsule C414 copy.

Unfortunately WA don't state an output level for a given input signal, and self-noise is stated in a non-standard way as "-115dB".

[Hugh Robjohns]

I think you mean Sides mic, Wonks... but yes, the KSM is more versatile.

https://www.soundonsound.com/reviews/shure-ksm44

And whoops! You're right, the WA14 is solid-state. Dunno what I was thinking of! I've edited my post to avoid further confusion!

Re the -115dB noise figure... not only is it non-standard, it's completely meaningless because they haven't given a reference. What use is a ratio if you don't know what the denominator is? Why would you quote self-noise in a meaningless way? Perhaps because the real figure is disappointing....

[Aaron Straley]

Thanks everyone. I've tried this mic in different rooms including a well treated room. Works pretty good for up close applications. Moving further away (even 20 inches) for acoustic guitar, just not working very well, and its all boiling down to not enough output from the mic. Not too happy with the performance of this one. Might be taking a look at the return policy and purchasing the KSM44a

[Wonks]

I've seen figures of 6mV/Pa for the WA14, which means it needs about 12dB more gain than a TLM103 in the same position.

I have a WA14 and I like it, but I haven't used it at any distance. However I do have a few alternatives if I need a stronger signal output.

[Hugh Robjohns]

Doing a quick Google for self-noise of the WA14, I came across a GearSpace thread which quotes a response from Warm Audio claiming the self-noise figure is 18dBA.

That's pretty bad for a modern solid-state LDC, but actually very close to the 1960s vintage C414EB it's supposedly based upon.

(https://gearspace.com/board/so-much-gea ... cm414.html, post 8)

However, the electronic self-noise figure is only one part of the equation. The polar pattern also plays a big part in how much room sound is captured, and room sound almost always swamps electronic noise in domestic settings.

[Aaron Straley]

I emailed the company for a full spec sheet and they are telling me its not compiled for the public yet. Seems really strange. Lessoned learned for me

[ef37a]

I think you mean Sides mic, Wonks... but yes, the KSM is more versatile.

https://www.soundonsound.com/reviews/shure-ksm44

And whoops! You're right, the WA14 is solid-state. Dunno what I was thinking of! I've edited my post to avoid further confusion!

Re the -115dB noise figure... not only is it non-standard, it's completely meaningless because they haven't given a reference. What use is a ratio if you don't know what the denominator is? Why would you quote self-noise in a meaningless way? Perhaps because the real figure is disappointing....

I am SO glad you said that Hugh, about that noise figure. I found it and was going to ask how to convert it to the conventional "self noise" parameter but you have now showed me it is not possible. I also don't think I could find a sensitivity figure to relate "-115dB" to either?
As for specifications "not released to the general public"? How very patronizing! Must have something to hide. "18dB" would be good for a mid priced SDC of course (but there are better) but is pretty poor for modern LDCs.

One trick to test for room noise? Roll the mic in a duvet in the quietest place in the house.

Dave.

[Wonks]

The WA14 came out in 2017, so it’s not like it’s a couple of months old.

I imagine the noise issue is (as Hugh mentioned) down to it being based on an old mic design and so have followed a similar component choice to get as close to the original sound as possible. But they’ve opted not to give all the pickup patterns, so it’s not a slavish copy.

They can make quiet mics, e.g. their WA47Jr has 9dB of self-noise, so it’s probably them sticking to a transformer-based circuit that is the culprit.

[Hugh Robjohns]

I still suspect room noise is the more likely root problem here, rather than mic self-noise.

Yes, 18dBA SPL equivalent is high in comparison to modern LDCs, but it's not unusably high. After all, vintage C414EBs were used in distant stereo arrays back in the day.... although we did have tape noise to mask mic noise then too!

[Aaron Straley]

Room noise may be part of the problem but I can get crystal clear recordings from other mics with all other factors being equal. Even less expensive ones. Also to get a decent recording level I need to crank the preamp towards 80%, while the same level on other mics requires about 55% on my preamp knob. Try one out sometime and LMK how it goes. From my experience, I would not recommend this mic to anyone

[Wonks]

Do you have any other fig-8 mics you’ve swapped out the for then, in exactly the same configuration?

[Hugh Robjohns]

Also to get a decent recording level I need to crank the preamp towards 80%, while the same level on other mics requires about 55% on my preamp knob.

This is not a problem. Different mics have different sensitivities by design. A low sensitivity mic will require more preamp gain than a high sensitivity mic.

Among my own collection of LDC mics, the least sensitive (AKG C414 B ULS) is 12mV/Pa and the most is 34mV/Pa (Blue Baby Bottle). So the quietest mic needs roughly 10dB more gain than the loudest.

The other thing to consider is that nominal polar patterns can vary substantially. Some cardioids are wider/narrower than others at different frequencies, so its quite possible for one mic to pick up significantly more or less ambient room sound than another at the same position and with the same nominal pattern.

[Aaron Straley]

Hugh - The company got back to me and said the sensitivity of this mic is 6mV/PA. By far, the least sensitive mic I own. I have gotten some good vocal takes and guitar cab recordings with it, but otherwise when I try to use it, always fighting for enough level on that track.
On quieter sources, it does get noisy when the pre's need cranked. Thats been my experience. Just doesn't seem like a versatile mic to me. If I can only use it for very loud sources or need the very best room to record with it in....its not really a "home studio mic" to me.
What should I use this for other than up close vocals or loud sources? Maybe someday I'll record fiddle or trumpets but otherwise its kinda a waste for me.
What are the advantages of having a mic like this over the same mic with better sensitivity?

[Hugh Robjohns]

Hugh - The company got back to me and said the sensitivity of this mic is 6mV/PA. By far, the least sensitive mic I own. I have gotten some good vocal takes and guitar cab recordings with it, but otherwise when I try to use it, always fighting for enough level on that track.

That is certainly unusually low for an LDC but, yet again, it exactly corresponds to the C414 EB that it is supposedly based upon.

Back in the days of the C414EB studio and broadcast mic preamps routinely offered 70dB or more of gain which would cope with 6mV/Pa quite happily. Today few interfaces and preamps offer more than 60dB and some not even that much.

Obviously, if close miking vocals and guitar cabs etc, the signal level will be very high, 60dB will be more than enough gain, and self-noise won't be an issue at all. But distant placement with quiet sources is obviously going to be far more of a challenge, as you've found. Most LDCs have a sensitivity of around 25mV/Pa, so 6mV/Pa is about 12dB quieter than 'normal'.

Throw in a less than perfectly quiet room and a relatively noisy mic and the results are inevitably going to be disappointing.

What are the advantages of having a mic like this over the same mic with better sensitivity?

It's designed to have the sound character of a vintage C414 EB, one of the more revered studio mics in history. But if it's not practical for your applications there are no advantages.

[Wonks]

Don’t ever think of getting an SM7b with its 1.1mV/Pa sensitivity then.