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-   -   A good stereo mic for PDX10? AT825? (https://www.dvinfo.net/forum/all-things-audio/21235-good-stereo-mic-pdx10-at825.html)

Ralf Strandell February 15th, 2004 03:13 AM

Shotgun mics good for stereo?
Thank you very much for your informative replies. The AT835ST seems to be a quite good stereo microphone...

There is something that I do not understand though. In many threads it is said that shotgun microphones are a) very directional and only good for picking up a selected voice where there is excessive ambient noise, and b) only good for recording talk (interview use and such). It is said that they may not have as pleasing a sound as cardioid mics (read: non-shotgun) have. It is also said that shotguns have an interference tube that cancels lateral sounds by wave interference and that it cancels mostly high frequencies thus distorting any off-axis sound.

This does not sound very stereo to me. What have I missed?

I'm not a sound technician, obviously, and neither will anyone hearing my recordigs be (unfortunately, probably). Thus any differences that require years of experience to be noticed do not exist to me.

So, if I want to record a high frequency ambient sound, then is this AT835 a bad choice? Doesn't it cancel high frequency ambient sounds by its design?

Would it be better to choose a mic with two spatially separated capsules? Would that become too expensive? ( 600 $ is quite a bit of money for me... )

Bryan Beasleigh February 15th, 2004 12:23 PM

Read the PDF. It shows the vaious polar patterns. I think it will answer your questions.


Patrick Bower February 15th, 2004 05:44 PM

Ralf, you will have to compromise. If you want maximum rejection of off axis sound, and a bit of stereo ambience, then a shotgun mic is appropriate. If you want hi-fi sound, with no colouration of any off axis sound that gets recorded, you can't use a shotgun. You either have to be closer to your subject, or put up with more off axis sound. The options are:[list=1][*]a fixed XY stereo cardioid, like the AT822 or AT825 or Rode NT4, but they will pick up all the sound at the sides (more than 180 degrees acceptance angle).[*]2 separate cardioids angled at less than 90 degrees, which will give you a narrower stereo field.[*]Ideally (but most expensive), a hypercardioid and a figure of 8 microphone, giving M/S stereo. This way, you can control the amount of off axis sound in post production. You may find these articles interesting:


Ralf Strandell February 16th, 2004 04:33 AM

Still unceretain about high freq. ambient sounds
The AT835ST has a line-cardioid element (front/middle) and a bi-directional element. It is a shotgun format microphone capable of mid-side stereo and internally matrixed left-right-wide stereo (wider than AT825 at 1 kHz) and left-right-narrow stereo. I would love the possibility of choosing a more directional pattern (L/R narrow) when ambience is not needed and a wide pattern when I want a wider stereo image. It might be a compromise, but it might also be just good enough for me.

So it is a shotgun microphone that is "wider" than a stereo cardioid (isn't that a contradiction?)...

The polar patterns in the PDFs for AT825 and AT835ST are for 1 kHz only... What about 500 Hz, 2 kHz, 5 kHz, 10 kHz and 18 kHz (near 20 kHz)? Can I find more accurate graphs anywhere?

What I fear is that the high frequencies from left/right are somehow lost/cancelled/distorted when using the AT835ST "wide stereo shotgun"...

... maybe because of the "shotgun" construction of the mic (the "interference tube")? I'm not sure. There is a bi-directional 8-element for the sides after all. So is this AT835ST wide only for low/mid frequencies? Or does it record any near-decent high freq. at the sides? I can't find these mics in any local shop so I cannot compare.

The question really is: Is a bidirectional + line-cardioid combi capable of HiFi or near-HiFi sound?

-slighly confused now-

Marius Peterson February 16th, 2004 08:36 AM

Sennheiser MKH 418-S
What about
Sennheiser MKH 418-S


Ralf Strandell February 16th, 2004 10:24 AM

An educated guess
The user manual of the MKH 418-S was quite informative. Thank you. I start to understand the basics of these mics now :)

So, the the line-cardioid mic (for the mid/front channel) has an interference tube that makes it more directional by eliminating lateral sounds, especially the higher frequencies. Thus it will record "high frequencies" only directly in front of it ("line"?) and "other frequencies" from a cardioid shaped area...

The bi-directional element (the side channel) records all frequencies from both right and left.

Because X/Y stereo is created by combining these two channels, then the higher the frequency the more it moves towards the sides unless it is right in the front, right?

Thus "high frequencies" would be *heard* either from left or right or front but not from, say, 45 degrees? This would distort the sound to some degree unknown to me. As I have not really studied how well ones ear can localize high frequenciens, I do not know how bad this is. Anyway, it now seems logical that stereo shotguns just might not record HiFi...

So, if I want true HiFi stereo then I really need the AT825 although it will be more prone to handling noise (than AT835ST in L-R-narrow mode) that could easily destroy the quality of the recording (especially when the mic is mounted on the camera).

If I would use bass roll-off to avoid part of the handling noise then the low frequencies would be partially lost, but the overall quality might be more acceptable. Unfortunately not all camera handling noises are low frequency (clicks and such)...

So the choices with the AT825 would be:

1) good stereo sound, bass light, lots of handling/camera noise
2) good stereo sound, better bass, even more handling/camera noise

The AT835ST on the other hand would not give such a good stereo sound because the sound localization would vary much more depending on frequency.

It would, however, produce "cleaner" sound without so much handling/camera noise and possibly without cutting low frequencies with a bass roll-off. Thus it might still sound better than the "HiFi" alternative. Especially if one cannot detect the "high frequency problems" too easily. (Is it so?)

Thus the AT-835ST might still be the mic producing the best overall quality stereo audio for camera-mount applications. The 825 would be better if I had someone else take care of recording because it should be kept well in front of the camera...

This is starting to become complicated now, and I feel that this thread might not lead anywhere anymore. One would just need to try the mics and listen to learn how prone to handling noise the 825 actually is compared to the 835 ST...

Ralf Strandell February 18th, 2004 12:59 PM

On another thread I found this exceptionally good link: http://www.jtv.be/JTV/info/sound/sound.html

Having read what Shure and Alan Barker have written about shotgun microphones I have no trouble in choosing between the AT825 and the AT835ST (and the suggested Sennheiser).

I want natural stereo sound. Thus I need the 825.

If the sound source is too distant I walk closer.

Case closed.

- - This thread was very useful. I learned a lot. Thanks to all the contibutors. - -

Dave Largent February 18th, 2004 02:51 PM

Just curious what you mean by "HiFi"?

Ralf Strandell February 20th, 2004 01:23 AM

Well, with HiFi sound I meant this time that

- it is a good and full (frequencies, amplitudes, directions) representation of what the ear can hear on location. With one exception: sounds from the rear should be ignored, because I don't want to record myself or the camera. There is a limit to the price I can afford, though.

- it contains even the 16kHz - 20kHz frequency range (many mics only have up to 16 kHz) and that high frequencies above 10kHz can be heard at a natural relative level without sacrificing human voice and talk.

Without a DAT this is a bit problematic because the frequency response of the camera itself is less than optimal (no, I cannot afford a DAT right now). Cameras freq. resp. http://www.jtv.be/JTV/info/sound/sound.html

- human voice sounds natural

- the resulting stereo sound feels natural with no coloration of sound from the sides. If there is some colorization of off-axis sound then the sound is not hifi, IMO. Mono sound is not HiFi because it completely lacks an important part of the sound - direction.

Dave Largent February 20th, 2004 01:38 AM

Where do you see that the M-S mics fall short?
If you do go with one of the X-Y mics, let us
know how the mic is.
I use an NT4 and have been happy with the
localization it provides.

Ralf Strandell February 20th, 2004 01:43 AM

And no; I don't want surround sound because it is far too complicated to record (lacking skill and there are better things to do in life) and edit and the equipment costs *far* too much.

And the show seems to go on...

I also looked at the Shure VP88. It's a stereo mic (M-S with internal matrixing option and an internal shock mount!) that has a cardioid mid element. Thus no coloration of off-axis sounds. Excellent, right?


It is both heavy (417g) and expensive (can get it at $800) and so it fits best on a big camera and a big budget (well, that's relative, but for me it is *very* expensive). But comparison is always good.

So how would that one compare to the AT825?
I mean, how shoud I interpret the differences in the frequency responses?

Ralf Strandell February 20th, 2004 02:02 AM

"Where do you see that the M-S mics fall short?"

Do they? I have nothing against M-S mics.


I don't care what sort of technology has been used to achieve a certain sound quality. It is the result that matters.

The AT835ST is a shotgun microphone. Thus the mid element does not hear high frequencies from the sides but it does hear lower frequencies. That must affect the sound... Tell me if I'm wrong. Shotgun mics are a bit problematic, too, if the sound source is moving or if the mic is moving - because of the side slots - or so I have read.

I haven't compared any mics because I only have the default Sony ECM-NV1 and no other microphones. I have to travel 2 hours by trains to find shops that offer some alternatives to test. That would be a whole day of mic shopping...

I don't want to do any "learning by buying". That's why I'm discussing this matter here despite of my limited knowledge in the field of mics.

The Shupe VP88 is not a shotgun mic, but it is a M-S mic. I would be very interested in it if I could get it a bit cheaper (and not $800)...

Dave Largent February 20th, 2004 02:28 AM

It's been awhile since I was shopping for a
stereo mic, prior to getting the NT4, but I
vaguely recall that I looked into the Shure
and that it didn't seem like it was all that.
Perhaps something about high self noise,
but don't quote me.
I do recall hearing that the NT4 is the best
stereo mic under $1000.

Ralf Strandell February 20th, 2004 02:53 AM

AT825 vs. Rode NT4
I did take a look at Rode NT4. It's quite nice, too. However, when compared to the AT825 mic the Rode NT4

- has about the same price

- has the same polar response

- has a similar frequency response with the exception of high frequencies. The curve slopes down faster for NT4 than it does for AT825. My camera seems to have enough of "high frequency roll-off" (probably too much?), so I prefer the AT825 that has a flatter response there. Shouldn't I ? Again, tell me if I'm wrong. Note that I was trying to record high frequencies here, so the fact that NT4 reaches lower (20Hz vs. 30 Hz) is not that big a deal.

- weighs two times more (NT4=480g, AT825=240g)

So the AT825 seems to be a better deal

... unless there is some big difference in the quality of the sound that cannot be seen in the numbers and graphs...

(and why is it so light? Both Rode and Shure weigh 2 x more...)

Ralf Strandell February 20th, 2004 03:25 AM

Can anyone explain to me how to interpret the self noise and signal/noise ratio?

The AT825 has 70 dB S/N ratio at 1 kHz, wile Rode NT4 has 78 dB. Isn't it so that 10 dB means double the noise? Thus the AT825 would have almost twice as much hiss?

I will be recording quiet sounds mostly, closer to 20 dB than 120 dB... And I want those high freq. quiet sounds on tape if possible...

Does the "self noise" affect this somehow? Or the sensitivity?

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