What is "line + gradient"

R

rtmst3k

Member
I have Barry's "audio for film and tv" and much of this information echoes what I've heard from other sources (which is good!). I plan on purchasing a shotgun mic for outdoors (fully blimped & furry), and a separate hypercardioid for indoor use (also furry).

In my shopping for microphones, there appears to be a LOT of choices for shotgun mics, but very little choices for quality hypers. And some microphone specs say that the pattern is "line + gradient", which is neither omni, or any other cardioid type that Barry's DVD or other literature talks about.

Is there a "shootout" available somewhere that compares hypercardioid mics? Also, can anyone shed any light on the term "line + gradient"? I understand omni, and all the <blank>cardioid pattern mics, but never heard of line+gradient.

Thanks a bunch!
Randy
 
Line + gradient is supposed to mean a shotgun ("beam" pickup... i.e. pseudo-laser accuracy... PLUS a gradient fall-off of pickup... meaning gradual reduction in off-axis (off "beam") sounds. If this were true then it would be a desirable characteristic... because "gradient" translates to "natural" in regards to sound... true "gradient" means a gradual attenuation... but the fact is that there are few mics that could truly claim this... the Sanken CS3e is one... the Rode NTG-3 is another.

It's just terminology anyway... so beware of adjectives and trust your ears.
 
rtmst3k said:
I have Barry's "audio for film and tv" and much of this information echoes what I've heard from other sources (which is good!). I plan on purchasing a shotgun mic for outdoors (fully blimped & furry), and a separate hypercardioid for indoor use (also furry).

In my shopping for microphones, there appears to be a LOT of choices for shotgun mics, but very little choices for quality hypers. And some microphone specs say that the pattern is "line + gradient", which is neither omni, or any other cardioid type that Barry's DVD or other literature talks about.

Is there a "shootout" available somewhere that compares hypercardioid mics? Also, can anyone shed any light on the term "line + gradient"? I understand omni, and all the <blank>cardioid pattern mics, but never heard of line+gradient.

Thanks a bunch!
Randy
Click to expand...

Line+gradient isn't so much a pattern as it is the physical principle used to achieve the mic's directional pattern. (There is a classic "lumpy" lobar shape to a line+gradient mic's pattern but the actual pattern is usually described as super-cardioid.) The mic's capsule is mounted at the bottom of a long ported tube, the classic shotgun mic form-factor. In fact, it's the resemblance of the tube to a gun barrel that gives "shotgun mic" its name.

Sound waves are pressure waves in the air consisting of alternating compressions and rarefactions, just like a sine wave is alternately above and below zero voltage. A portion of the sound waves arriving from the front of the mic enter the tube and pass down inside it. The portion of those same sound waves that are passing down the outside of the tube are in step with that inside. As they pass the ports the pressure bleeding in through the ports is in phase with the portion inside, adding to it so it gets to the bottom of the tube unimpeded to hit the diaphram. But sounds arriving from the sides and rear enter the tube first through the ports, then their inverse wave enters the tube from the front and starts down the tube. For those sounds the pressure in the tube coming down from the front entry is in compression while the pressure from the portion of the wave coming through the ports is in rarefaction and vice versa. The two wave fronts are 180 degree out of phase and interact within the tube to cancel each other out. Because the tube and port system is resonant, just like an organ pipe, the degree that this interaction takes place is highly frequency dependent, becoming almost non-existent at low frequencies and so shotgun mics can behave almost as omnis under certain circumstances.

The interference tube physics works fine for direct sound where the sound field is coming directly from the source but in an interior the sound hitting the mic is a mix of direct and multiple reflections of the wave. The reflections are slightly delayed with respect to the direct waves and so the various waves are partially out of phase with each other. When they interact within the mic tube all sorts of strange freequency-dependent reinforcing where they should cancel and cancelling where they should reinforce goes on, leading to the classic "recorded in the bottom of a well" hollow sound of a shotgun used indoors. Hypercardioids use a different physical principle to achieve their directionality and so don't suffer from the same distortion.
 
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True there are a ton different shotguns, all made for different uses and distances and directionality. When indoors, as mentioned above alot of the variables that you get outsides aren't inside and you have new variables to deal with but mostly the same from local to local but anyways, your basic list of indoor mics would be (pretty much in price order from most expensive to cheapest)

Your standard Schoeps CMC6 with MK41 cap. Pretty much the favorite of just about everyone, I love this mic. Very warm, i've recorded screaming matches and not a single bit of distortion.

Your Senn MKH50 and now the MKH8050 modular mic, I personally have no used these two mics but i've heard that th 8050 sounds really nice but does have some major low freq issues but if you have a low cut on your mixer then you should be golden.

Farther down the list would be the AKG ULS series with CK63 cap.

and then you have the AKG Blueline with CK93 cap. There are known problems with this mic when paired with a Sound Devices mixer. I've had it just cut out and stop working then you have to set them down for 10 minutes then they start working again.

Oktava MC012 (now has an availible low cut filter) Personally I think the MC012 is the best bang for the buck if you can't aford a 1900 dollar price tag of the Schoeps, isn't as warm and even with the 10db pad you can still get some distorting if levels get too intence.

Happy shopping.

Eric
 
ZeroContent said:
and then you have the AKG Blueline with CK93 cap. There are known problems with this mic when paired with a Sound Devices mixer. I've had it just cut out and stop working then you have to set them down for 10 minutes then they start working again.
Click to expand...

That's the first I've heard about that issue. Do you know other people with the issue using that mic/mixer combo?
 
Thanks everyone for the replies on this thread...I will try to remember that, in essence, "line + gradient" approximates the performance of a shotgun mic, and I will assume that this is probably better for outdoor use, or some "special-case" indoor use.

I'm' definitely leaning towards a hypercardioid for indoor use, and while I can't afford the Schoeps, I'm leaning towards the Audio Technica AT4053a.

I understand that the Oktava mk012 is the "darling" of the low-budget indie film/video folks, but there are apparently very few places to buy this thing, and my local dealers here in LA don't carry it. B & H doesn't appear to carry it either.

I heard some tests on the AT4053a and it sounded real good, and it's about the price I'm willing to pay. I'm basically looking for the richest, warmest, clear sound I can get indoors for under $500. The Rode NT3 also sounded nice but it's pretty heavy for booming all day long...

Thanks again for the replies!
Randy
 
rtmst3k said:
I understand that the Oktava mk012 is the "darling" of the low-budget indie film/video folks, but there are apparently very few places to buy this thing, and my local dealers here in LA don't carry it. B & H doesn't appear to carry it either.
Click to expand...

Sound-room.com is the only place to get it with the hyper cap in the US (to my knowledge). Enter the coupon code "dv" for a discount.

And thanks for the link ZeroContent.
 
rtmst3k said:
Also, can anyone shed any light on the term "line + gradient"? I understand omni, and all the <blank>cardioid pattern mics, but never heard of line+gradient.
Click to expand...

There are basically just two types of microphone:

Pressure - which looks at changes in the sound-pressure level - this is a "sealed box" type of mic. and the polar-pattern is OMNI

Pressure Gradient - which looks at differences in the sound pressure level - this diaphragm is open on both sides and the polar-pattern is FIG-8

All other polar-patterns are a combination of the above- EG:
Cardioid is equal pressure and pressure-gradient: 1:1
Super-cardioid has more of the gradient component: 1:2
Wide-cardioid has more of the pressure component: 2:1

Any mic. that is not omni is normally termed as "pressure gradient"

So, basically, a "Line + Gradient" means that it is a gun mic. with an interference tube on the front (Line) with a pressure-gradient capsule inside (Gradient). Most gun mics tend to use a super-cardioid as the basic capsule because it gives directionality at low frequencies where the interference tube falls over (though the old Sennheiser ME 88 actually used an omni at the base of the interference tube).

I hope this helps.
 
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