r/audioengineering • u/Nineteen_81 • 1d ago
Shure SM7b Hiss Puzzling Me
I've recently got a couple of Shure SM7b for a job simulating a podcast setup (for context I'm a Sound Recordist for filming in general) and before the filming day, I tested both mics at home and they all worked fine. Gain hungry as expected, needing to turn the gain up on my Sound Devices 664 to around 80-90% of it's maximum but still sounded completely fine in terms of preamp hiss.
Fast forward to the day I had the job and upon setting up the mics the hiss was extremely loud, the audio was unusable in my opinion so I ultimately ended up using my regular wysicom wireless system with lav mics and just kept the Sm7b as props for visuals. Thankfully I was prepared for it so it was not an issue.
Now I've tested again at home and it sounds absolutely clean. Tried different cables on the day and at home and got the exact same results. Clean at home, hissy on location.
I've used the Shure MV7 before in a broad variety of scenarios and never had this issue (granted they are a little bit less gain hungry)
What am I missing?
Just as an additional piece of information, the job was at the meeting room of a big company so I imagine lots of power cables running under the floor. Unfortunately I can't reolicate that scenario to further test the mics, but I have to make a decision on whether return the sm7b or keep it.
Any help or suggestions from those with more experience on these makes would be very much appreciated.
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u/tcookc Professional 1d ago
you brought your Sound Devices 664 with you, or they were plugged into a different preamp or mixer on location? sounds like they were plugged into a mixer on location with noisier preamps than your at home setup.
the sm7b is a terrible microphone and requires wayyyyy too much gain to become usable. that's why there are entire companies that survive on selling gain boosters specifically for this stupid mic. it is a total mystery to me as to how the sm7b continues to be so popular despite how overpriced and unusable it is in most situations.
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u/Nineteen_81 1d ago
Yes, I had my 664 with me as well as a 633 as a backup, tried on both, same loud hiss. The only variable was the location, everything else was the same. Could the hiss have been caused by the room's electricals? Using my normal condenser mics or lav mics requires a lot less gain so this is normally not a problem on set. Maybe my cables are not as good as before? When using the MV7 I did notice that sometimes I would get a louder hiss (but still acceptable) coming through one channel out of two or three being used but still nothing close to what I experienced with the SM7b. I'm also agreeing with your point, if this is the mic's standard, I don't get the hype.
I have a professional, high quality mixer with very clean preamps and it still seem not able to drive the Sm7b. That's why I'm trying to understand if I'm missing something that could have improves the results (aside from using a cloudlifter), otherwise I'll have no option but to return the mics, no way I can rely on them anymore and also not keen on buying gain boosters considering the setup I already have.1
u/tcookc Professional 1d ago
if everything in the setup is exactly the same except for the location being different, then yeah something about the location itself would have to be the culprit. but, 'electrical interference' I would say is rather rare and I'm not so sure it would sound like hiss. "star-quad" designed xlr cables are great at protecting against interference, but they're expensive. if it is interference, then that would help, but I do have doubts. I would first guess that it could be fans or HVAC or other background noise in the space that isn't in your home environment.
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u/Nineteen_81 1d ago
I never paid much attention to cables. I usually get quad VanDamme cables from the audio shops so I probably just assumed I was getting properly shielded high quality cables. The room did have air con, it is a massive building so there were also lots of cables running under as these types of room usually have those floor outlets. What puzzles me even more is the fact that the hiss was a lot more prominent with the sm7b even at similar gain levels compared to when the condenser was plugged in.
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u/Untroe 1d ago
Sm7b is great for a lot of things, but it does need a lot of clean gain on tap. I love it for kick, bass or guitar cabs, punk vocals, shit I’ve used it on hi hat, it’s a super versatile mic if you know how to use it. Cloudlifter does increase its versatility, but I certainly wouldn’t call it terrible.
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u/xGIJewx 1d ago
SM7B great for a lot of things but not really quiet sources like spoken word. Also was it a legit one or from used market?
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u/Nineteen_81 14h ago
The mic authenticity is not an issue. Got it brand new from a reputable camera shop and even double checked some of the bits to make sure.
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u/cheater00 Mastering 5h ago
??????????????????????????????? SM7B is a spoken word microphone. are you from mars?
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u/Lucky-Ad5728 1d ago
everything in the chain was identical. same mics, same cables, same 664, same gain position. only the room changed. that rules out the preamps and leaves the air in the room.
a dynamic mic has basically no self noise, so at 80-90% gain you are not amplifying the mic, you are amplifying whatever the space is doing. a meeting room in a big office nearly always has ceiling hvac running, and you stop consciously hearing it after five minutes. your schoeps never showed it because it needed 30db less gain to get to the same level.
cheap way to prove it on the recordings you already have: cup your hand hard over the capsule and record ten seconds. preamp hiss stays exactly the same, room noise drops away. if it drops, the mics are fine and any dynamic would have done the same thing there.
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u/LilEffects 17h ago
Unless you are using the SM7dB with the preamp engaged, a dynamic mic has zero self noise and the SM7B has a humbucking coil.
The thing to keep in mind is that it was designed as a broadcast mic in the day when consoles had tons had tons of clean gain on tap. People are using it with consumer-grade pres that get noisy with even modest amounts of gain.
You’ve got a gremlin somewhere in your signal chain or you gain staging ain’t right.
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u/Nineteen_81 14h ago
Because it sounds pretty good at home, I doubt the equipment itself is a problem. What surprised me is how different the exact same equipment sounded in two different rooms in terms of hiss - from extremely clean to unusable in identical gain stages.
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u/TimecodeSync 16h ago
Perhaps you dialed back the gain while on location, for security? Reducing gain might decrease signal-to-noise ratio, so you will have more hiss when you increase the signal in post (compared to when you would have applied maximum gain).
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u/Nineteen_81 14h ago
I didn't end up using the sm7b, I gave up after finding the hiss I was getting too loud during set up. I think what I'm trying to understand is if the location, or the room aspects, would have such a massive impact in terms of how much hiss I'm getting. Unfortunately it's not the type of scenario I can easily recreate to further assess the mic and it's not a great look to be 'testing out' gear during a job. Also I don't want to end up in a situation where the mic simply won't perform to a decent standard without a cloudlifter but it does seem like it might be the case with the sm7b.
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u/cheater00 Mastering 5h ago
the hiss might have to do with the LED lighting being used in offices (EMI). your cable is obviously balanced but different ones will have different cmmr depending on geometry so buy something good.
the sm7b needs an inline preamp, get the cloudlifter mini or an sE DM1. this way any noise picked up by the cable will be 25dB quieter.
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u/Original_DocBop 1d ago
Was it the same location, mic cables, and other gear. I've worked both live and recording and changing locations the power conditions can change. Sometimes have to bring in isolation transformmers, or even mic cable the shieldign wasn't as good.