Topic: Newbie Question: What does the term "active" mean for mics?

[BradM]

I keep seeing the term "active" (as in "AKG Active Project", "New Sennheiser Active Setup", "active cables") used in describing microphones, and I have no idea what it means. My main experience in taping is with small-diaphragm condensors (I use Oktava MC-012s), so I grok phantom power and such, but is "active" something above and beyond phantom powering, or does it mean something completely different? Functionally, what are the advantages (and/or disadvantages) in using active mics vs. SDCs? (And what are some of the more popular/common active mic models that I could keep my eye open for in source info?)

Thanks,
Brad

[Sheed]

i'm sure others will chime in but active cables basically allow you to separate the mic capsules from the mic bodies for running more low profile.  i'm sure if you search the rig pics sections for "actives" or some such word you'll find some nice pictures. 

[George2]

Just an exstention cable between the capsule and the mic body, commonly used for lower profile during filming or video taping. Why do tapers want to invest in these cable? They aren't cheap.

[fozzy]

Just an exstention cable between the capsule and the mic body, commonly used for lower profile during filming or video taping. Why do tapers want to invest in these cable? They aren't cheap.

much lower profile, generally mount into a single shouckmount, much less gear to carry around

[rokpunk]

sennheiser refers to their cable as a "remote cable" not an active cable. basically it's a cable that remotes the body from the capsule. they are generally used in tv/film since they are easier to keep out of a camera shot than a typical small diaphram condenser. i'm still not 100% sure why tapers use these as much as they do...frankly it's just another thing in the signal chain to worry about, but i suppose it's for the lower profile. the new sennheiser system is so small to begin with, the remote cable seems almost useless.

[eric.B]

I could be wrong, but I thought the only "active" cable was made by DPA for their 40xx mics.. the rest are just extension cables as mentioned..

[Patrick]

I could be wrong, but I thought the only "active" cable was made by DPA for their 40xx mics.. the rest are just extension cables as mentioned..

I'm not sure about other brands but I know the schoeps KCx active cables are not simply "extensions" but have active components within the connector housing.  What those components are and what they do, I have no idea    But I do know that they're in there somewhere.

[John Willett]

Regarding the Sennheiser MKH 8000 "Actives" - the microphone head (capsule) is in fact the complete microphone.  The end is just the XLR connector and the cables just connect the two.

I think the term "active" came into existence to differentiate between the old remote capsule microphones where only the capsule was remoted and the cable was unbalanced and very high impedance (so all the electronics were at the XLR end) - and the newer ones where there were electronics in the capsule and the remote cable was low impedance and fully balanced.

[it-goes-to-eleven]

"Active" means "Expensive".

[DSatz]

Active accessories were developed by engineer Jörg Wuttke and patented by Schoeps in 1973 as part of their "Colette" series of condenser microphones. Attached is a drawing from the German patent document; the first active accessories were flexible extension cables which could be placed between the capsule and amplifier of a microphone, thus allowing the capsule to be placed unobtrusively.

The word "active" refers to the presence of circuitry (i.e. a gain element) in the cable or other accessory. Previous extension accessories, such as passive extension tubes, created a risk of signal losses, distortion and RFI since the output of a traditionally polarized capsule occurs at extremely high impedance (billions of Ohms). The FET circuitry of the Schoeps active cables, extension tubes and goosenecks overcame this problem.

Schoeps also devised an active low-cut filter (the "CUT 1") which could go between the capsule and amplifier, along the same lines; it is used by many film and video sound people to eliminate low-frequency noise due to wind or room rumble, and it can even be combined with other active accessories if needed.

The system was imitated, or occasionally copied outright, by all the other major microphone manufacturers within a few years. Some companies such as Neumann were scrupulous in observing Schoeps' patent rights (their designs, like Sennheiser's new MKH 8000 series, place the circuitry in "active capsules" rather than in the accessories), while other manufacturers were not quite so careful. In any case the patent has now run its course.

--best regards

[Tim]

Why use them? Much lighter weight than mic cables, they take up less room in the bag, they let you tape from in front of the board with less worry about blocking sight lines or being seen if you're trying to be stealthy.

frankly it's just another thing in the signal chain to worry about

Actually it's exactly the opposite. Everyone I know leaves their caps connected to the actives all the time, and samefor the bodies which are connected to internconnects which are connected to the pre. Nothing ever has to be unplugged so you don't have to worry about an xlr end going bad from plugging/unplugging.

With an active setup you can be up and running in 2 minutes, literally. It's just a much quicker, lighter and easier way to tape.

I could be wrong, but I thought the only "active" cable was made by DPA for their 40xx mics.. the rest are just extension cables as mentioned..

Schoeps (kc5), Neumann (lc3) and DPA are all active. MBHO is not. Not sure about the others

"Active" means "Expensive".

This is true

[DSatz]

Tim, since the point of this thread is to talk about how it all works--Neumann's LC 3 cables and other KM 100-series accessories are not active; their capsule heads are. That's why the interchangeable capsule heads for this series of Neumann microphones have the names "AK 20," "AK 30" etc.--the "A" stands for "active."

They are all built in two distinct parts (see attached photo)--the front part is the actual transducer, while behind it sits a little cylindrical barrel containing a FET and a couple of resistors. This same barrel is part of every active capsule head in this series. Its little circuit accepts DC power from the output stage (the "body" of the microphone) and delivers a fairly-low impedance, unbalanced signal to the output stage via the cable, gooseneck or tube--or directly, if no extension accessories are being used.

The output stage contains ICs and an output network to accept phantom powering and to convert the signal from the FET circuit to a balanced, low-impedance signal, which is then fed to the XLR connector.

--best regards

P.S.: Aside from the patent issues, the main practical difference between this approach and the Schoeps approach is that the Schoeps approach keeps the capsules simpler; if you want just the basic microphone and maybe some alternate capsules, but no active accessories, you don't pay any extra for the flexibility options. If you decide to buy a "Colette cable" or other active accessory then yes, that does become more expensive. But people don't tend to need many different active accessories, and it's nice to keep the cost of alternate capsules down to a dull roar.

The Neumann approach makes their extension accessories less expensive, but then every capsule has to include the extra cost of the special "active" element whether the customer intends to use extension accessories or not (many people don't). As a result Neumann's KM 100-series capsule heads are rather more expensive than they would be otherwise. If you own a pair of KM 100-series microphones and want to acquire capsule heads with other directional patterns, you end up paying for the multiple "active" elements even though you can use only two of them at a time. (Thus the KM 180 series exists ...)

[Tim]

Thanks for clarifying

[BradM]

Thanks for all the info! Everything's a lot clearer for me now.

Aloha,
Brad

[danlynch]

Yes, I've been pricing the LC3's for my 150's, but at about $200 a pop, it just seems too much to pay for cable that give the ability to go stealth once in a while with the Neummies.