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I recently bought a Rode NT4, and after several tests with my Tascam, the bass frequences bellow 80 hz are too high, like a constant rumble. Fixable, but annoying...

With a pair of Sontronics STC1, I have another problem : a sort of blow, above 5000 Hz...

So, where does it come from ? Any idea ? Any advise on how to fix it ?

the bass frequences bellow 80 hz are too high, like a constant rumble.

Ruling out the obvious, you are using wind protection if outdoors and you are mounting the mic on a tripod or mic stand, not handholding it?

Also if you are lifting the gain above real levels, you will find low frequencies more audible as a result of the ear's nonlinear frequency response with level.

http://en.wikipedia.org/wiki/Fletcher-Munson_curves

I find with a Sennheiser MKH30/40 pair I can hear aircraft noise in the headphones earlier than unaided, if the gain is set high enough, and traffic rumble is more apparent. At mid to high frequencies the system self-noise masks the benefit of the extra gain - I don't hear other sounds clearer through the recorder than unaided.

I had never come across this effect using cheaper mikes, presumably because the self-noise made the signal unlistenable before the sound level at the headphones became raised above ambient level.

Glaneur de sons
I recently bought a Rode NT4, and after several tests with my Tascam, the bass frequences bellow 80 hz are too high, like a constant rumble. Fixable, but annoying...

With a pair of Sontronics STC1, I have another problem : a sort of blow, above 5000 Hz...

So, where does it come from ? Any idea ? Any advise on how to fix it ?

Same here, I neither liked the low frequencies from the NT4. Has no low cut filter and you have to correct it in post. This, along with its very high handling noise when used in the field.... well, sorry to tell but it went to eBay.

Ok, that was what I was wondering... Handling sounds are not really a problem to me, as I use it on a stand indoors just for little sounds, but this low frequencies problem are annoying.

Here is an unedited wave file of a sound I recorded, the Tascam on 5, so that you see what I'm talking about.
And here is another example with the sontronics.

Anybody, any idea to fix the problems, or any idea of a better microphone for this kind of recording ?

Thanks for your help.

Look (or hear ), your samples are two different recordings of totally different sources, so it is not possible to compare the microphones that way - but judging from high noise and harshness on "sontronics" recording it is not exactly the microphone I would want to use... The NT4 sound fine to me - the low rumble is normal (like ermin explained) and it also sounds like on your recording it was caused by some handling or recorded object vibration or it could also be from the proximity effect of the microphone - bass frequencies are enhanced when you close mic audio sources - there is no other way then to do a low cut or low shelving in post production if the mic doesn't have a low cut switch... But the overall sound of your short clip of NT4 sounds nice... I don't hear a problem.

On the NT4 it sounds like you have a resonance in the combination of the mic and the stand which is picking up the impact as a structural vibration. There is a characteristic 'thunk' which I associate with a heavy mic picking up vibrations on a non-elastic suspension.

You might want to try using a floor stand and stand it on a solid concrete floor eg in the ground floor, rather than on floorboards in an upstairs room. Or possibly your object is on a wooden table, and that is resonating with the impact like a soundboard when the object is struck.

I agree that the Sontronics is noisy and perhaps not your best mic, unless the sound was really faint and not the sound of something like a door creaking loudly

Thanks for your reactivity, Ermine, it's really great to ask something and have answers within an hour !

I agree with what you say, and it's true that I recorded the sound on a wood floor. I was still using these homemade suspensions, which are not my best handwork :
http://glaneur.de.sons.perso.orange.fr/medias/suspensions.jpg

(You'll understand why I call them "rednecks"... :wink: )

So, I understand the first point : buy suspensions (or a least one for the NT4) !

But there will be always the problem of low frequencies on the NT4, and the noise on the Sontronics is still bothering me. So, any advice on microphones ?

Thanks again.

Ah, that is clearer. Your suspensions look fine, but the way you are using them doesn't The mic cable also conducts sound to the mics (wear headphones with no input and listen to the conducted sound if you touch the cable 5cm from the earpieces to confirm this...).

You want a long piece of cable (about 30cm or more) hanging loose and then clamped to a solid structure. Or you need to make a loop and clamp it to something that won't move.

At the moment all the trouble you have taken with your suspension is being degraded by the mic cable transmitting the floor vibrations to the mics via about 5-10cm of the cable, which is resting on the floor. Listen to the mic when you tap the floor, then raise the stand so there is more of a loop of wire, maybe taped to the stand after 30cm of a loose loop, and tap the floor again.

The mics are not necessarily at fault - any mic with an extended LF response will behave similarly. But at least the fix is low cost.

You also have the mics low-down on a table. This will tend to boost low frequencies by working as a boundary, if you raise the stand and have it on the floor aimed across the table you will pick up less sound from the table and have more air for the mics to pick up sound - you may get a better stereo image too. The NT4 have a reasonably good reputation though people sya they are a little more prone to handling noise than others so you will need to take a bit more care with the mounting. This is easier to do indoors though.

You may also want to look at using O rings for your suspension (or old VCR belts) these do not have the bounce that rubber bands do, so they have more internal damping which may help. Also experiment with the tension on your elastic suspension. I use a similar rig to yours sometimes, using wide flat rubber bands, and it works very well. Not quite as good as a dpa shockmount but the price is good. On the dpa they use specially thin and damped cable to reduce mechanical sound conduction through the cable to the mic, but I find if you have a long enough length from the mic to the clamped cable this works well enough with normal mic cable.