why phantom over battery?
 

after reading the abundance of information, both objective and subjective, on this forum regarding mic choices and usage, i found myself in the unfamiliar world of phantom powered mics when recently faced with buying decisions, specifically about the best mics for my budget and what i want to get out of them. after heading over to B&H and looking at some of the mid-priced ATs (and giving all the samples on this board a listen -- thank you beas, matt, ty, dse, etc), i sold my two battery powered ENG mics, and purchased the at4073a, at4053a, and a marantz pmd660 recorder (which has two xlr inputs that provide 48v phantom power).

my question is probably more technical than anything else... why are there so few quality battery-powered mics out there? in other words, why are all the real quality mics phantom powered? does the battery introduce interference or some level of noise to the audio acquisition process? or is it just an assumption that the real quality mics will be powered off of a mixer or other professional device?

thanks for indulging me...

If I am wrong, I hope someone corrects me....

Phantom power usually means you are running a balanced circuit, whereas battery power means an unbalanced curcuit. Balanced is obviously much better for quality. For my needs, I like mics that do both, like the AT825 and at897.

It's not really an issue of balanced versus unbalanced. There are balanced mics that can be battery powered and balanced mics that require external phantom powering.

After having spoken to some really great mic designers from Neumann, Sennheiser, AKG and Audio Technica about this question, I'm told that from a design perspective electret (or internally polarized) condensers can be made every bit as good as externally polarized condenser mics.

With a little time I could probably dig up a few electrets that sound better than some externally polarized mics, but I don't have the time. Suffice it to say that during the last five years there have been some truly crappy condenser mics that have come out of China.

The Neumann RSM-191 stereo mic (link below), on the other hand, is the most amazing stereo mic I have ever heard. And that's saying a lot. It can be run on batteries.

http://www.neumann.com/infopool/mics...&Language=Engl

That's not really the answer you wanted, but it's the best I can offfer. It remains a puzzle.

Regards,

Ty Ford

It's not really an issue of balanced versus unbalanced. There are balanced mics that can be battery powered and balanced mics that require external phantom powering.

After having spoken to some really great mic designers from Neumann, Sennheiser, AKG and Audio Technica about this question, I'm told that from a design perspective electret (or internally polarized) condensers can be made every bit as good as externally polarized condenser mics.

With a little time I could probably dig up a few electrets that sound better than some externally polarized mics, but I don't have the time. Suffice it to say that during the last five years there have been some truly crappy condenser mics that have come out of China.

The Neumann RSM-191 stereo mic (link below), on the other hand, is the most amazing stereo mic I have ever heard. And that's saying a lot. It can be run on batteries.

http://www.neumann.com/infopool/mics/produkte.php?
ProdID=rsm191&Language=Engl

That's not really the answer you wanted, but it's the best I can offfer. It remains a puzzle.

The bottom line is to get the best sounding mic you can.

Regards,

Ty Ford

Based on discussions with designers at AT and Audix, both say that inclusion or non-inclusion of a battery is dependent on weight, design appearance, cost target, and where/how the mic is intended to be used.
Keep in mind from the video side that until recently, few mics were designed with the film/television/video production world in mind. Those that were designed for these areas of use are pretty well accepted as standards, and virtually everything else is a 'newcomer' to the market when compared to some of the older ones. I think that Ty would agree that even 5-6 years ago, there were very few mic choices in terms of what was "accepted" whereas today, there are quite a few more models of reasonably comparative value to the well established standards.
As more mics are designed for the field production, film, and television industries, you may or may not see battery power creep in. At least cams now have phantom, whereas a few years ago only a handful of higher costing cams did.

thanks bob and ty...

bob, i read your post and you mentioned mics that do both, like the at897 and it got me thinking.

i did some fiddling around last night. i have an me66 that can also run by phantom or battery power vis the k6. i connected it to the pmd660 with and without the battery. when connected to a 48v phantom power source, the mic runs noticably hotter than when connected via battery.

i'm thinking the answer lies in the voltage being provided by the power source. perhaps the voltage from a battery wouldn't be enough to power many of the high-end condensers as designed. needless to say, this is completely speculative.

thanks dse... i didn't see your post as i was writing mine...

Henry I think you have it right about voltage. When I was shopping mics last year the Dynamic Range was always written in two versions, phantom powered and battery powered; phantom was always better. Here is an example with the at897.

Transducer Condenser

Polar Pattern Line + Gradient

Frequency Response 20Hz to 20kHz

Dynamic Range (Typical) Phantom: 112 dB, 1kHz at Max. SPL
Battery: 98 dB, 1 kHz at Max. SPL

Signal-to-Noise Ratio 77 dB, 1kHz at 1 Pa

Maximum Input Sound Level Phantom: 129 dB SPL, 1 kHz at 1% T.H.D.
Battery: 115 dB SPL, 1 kHz at 1% T.H.D.

Power Requirements Phantom Power: 11 - 52V, 2 mA typical
Battery Type: 1.5V AA/UM3

Output Impedance Phantom: 200 ohms
Battery: 300 ohms

Output Connectors 3-pin XLR

Pad No

Low Frequency Roll-Off 80 Hz, 12 dB per octave

Dimensions 0.83 x 10.98" (21.0 x 279mm) (Length x Diameter)

Weight 5.1 oz (145 g)

thanks jerry...

the reason why i asked this question in the first place, besides straight-up curiosity, is based on the simple fact that sometimes i have no other option than to run a camera mounted mic and my xl1 does not have native phantom power. i understand that camera mounting is a far-from-ideal use of any quality mic, but a lack of a live-in boom operator (unfortunately my wife doesn't qualify) often makes off-camera sound an impossibility. battery power offers me flexibility in this regard, but, again, the lack of high-end mics that are powered by battery makes things a bit more complicated. i'd love to put a "battery powered" sanken cs3e on a k-tek shock mount, with the optional camera mount adapter. when i need to run on-camera, i can put it in battery mode, and put the shock mount on the camera. when i want to run audio off-camera, i can unscrew the mic holder, put the shock mount on a boom and run phantom though a mixer. the point of minor frustration about all this is the fact that with all the money i've spent on mics i've accumulated to cover various scenarios, for a few hundred dollars more, i could have bought a schoeps AND an mkh60 (which are both in my ultimate plans). don't get me wrong... i'm really digging all my mics so far, but i would have loved to buy a high-end condenser which offered me the type of flexibility i mentioned and called it a day. i doubt sennheiser even thought someone would want to mount an mkh60 on a gl1 or xl1, but i think a mid-priced mic like the cs1 would benefit from offering this kind of flexibility considering the success of the me66 and at897.

several companies make small, battery powered phantom power boxes.

Ty Ford

My only non-technical observation on this is the fact that having to run on phantom power means that you can pretty well be assured of a constant voltage supply to the mic element. With battery power, you will have that point where the battery will die and possibly degrade the mic's performance just before doing so.

Again, no technical facts to prove this but just my thoughts on why a design engineer might choose to go this route.

=gb=

greg, that makes sense to me... thank you...

ty, i'm definitely going to give one of those power supplies you mentioned a shot.

Part Two -- Phantom Supplies

Please be aware that Phanton Power requires the enough voltage and current.
The formula fforr power is P=IxE. P is Power, I is current and E is voltage.

The point is some Phantom supplies only crank out 12 or 24 volts and dont have the current to power some phantom powered mics.

SOme mixers say they have 48 VDC Phantom and do, but the current is to low to power any more than one or two mics that really use a lot of current.

When a phantom powered mic is under powered, the result is higher noise and distortion because you are starving the mic. Most condenser mic spec show a rating of voltage and mA (millamps) required to power it properly.

Please make sure the phantom supply you choose can handle the mic you choose.

Other tips and tricks are in my Audio Bootcamp Field Guide book whicch is available on my site.

Regards,

Ty Ford

i just got back from b&h (no i don't camp outside the store... i just work a few blocks away), and talked to a rep about portable phantom power devices. he initially showed me the beachtek DXA-6.

http://www.bhphotovideo.com/bnh/cont...ist&sku=224231

it advertises sustained 48v phantom power to two channels off of a single 9v battery (i don't see how that math works itself out). it's not cheap at $250, and i wasn't thrilled about the stereo minijack audio out. i passed on it.

everything else they had in stock by way of portables advertised 48v mic compatibility, but, as ty stated, output only between 9-24v of true power to the mic. the sales rep said that there was nothing short of a $350 mixer that could kick out sustained 48v power to a mic that didn't have to be plugged into a wall. he did say that my ATs would probably run fine on something that could kick out around 18v, but i've read posts about hiss and noise being introduced when a portable mixer is underpowering the mic.

i guess this cuts right into the original question about why most high-end mics run off phantom power.

if i'm missing out on a product i should give a look, please let me know. thanks...

http://www.sweetwater.com/store/category/c494

Regards,

Ty

thanks for the link ty. i'm going to take a look at the stewart bps1. the sennheiser is too expensive for me, and everything else seems underpowered or needs a wall to plug into.

Henry,
Awhile back I was in your situation and a real pro mixer
here recommended me a reputable portable
phantom powering unit that she actually uses in
her work. It is Denecke brand. Costed around
$125. Seems real solidly built. Runs on one 9V
and puts out 48V phantom. Has an option to
activate a 15dB attenuator. Has low battery
indicator. I remember being told that one nice
thing about it was the way the battery is connected,
that it's a real solid connection.
Don't recall the model number off the top of my head,
something like P-1a or something, I think.
Anyways, I've been happy with it. If you need me
to check the model number let me know.

dave,
i really appreciate the suggestion. funny enough, after doing some research last night, i bought the denecke ps-1a from trewaudio... i like that the denecke looks like it could take a beating and it's size is compact enough to possibly velcro mount to my ma-100... if it all works out, i'll post some pics of the rig. thanks again...

Yeah, Henry, that's the one that I've got. I even think
I purchased it from Trew Audio! You know if Trew
sells it, it's probably a good unit. The owner of the
company not only has that store but also works
as a pro mixer as well so I don't think he'd be selling
stuff that wasn't pretty decent quality.

Back to the subject line of this posting... Although I am no expert, I believe it is common knowledge among "audience tapers" that using phantom over battery (when you evenhave the choice) can provide a wider dynamic range, and more importantly, can help prevent brickwalling in high SPL enviroments. Not sure, but this might depend on the mic. As stated in an early post, some mics even list out this difference in the technical specs. Please note that this comment is most applicable if you are recording in LOUD environments like rock concerts.

ME66 powered by phantom and powered by its K6 internal battery does have some audio differences. But, I speak only for ME66 - I don't know of any other mics (which I have no access to). The differences are so small I think you need to be a bat or a dog in order to hear the difference. I use a digital oscilloscope to test (A-B). Phantom power appeared to have a flatter frequency response in the low end. Mid and highs are essentially the same. I do not know why this is the case.

Also - note the following ... if your mic can accept 12V phantom, please use it, instead of upping the voltage to 48V. Sound wise, the mic and mixer will not see any difference. But the battery driving the mixer will say thanks to you for using 12V rather than 48V. Because the consumption of battery power is 4 times greater in 48V phantom as opposed to 12V. Hence, if your mixer and/or portable phantom power generator can switch between 12 and 48, try 12 first.

TS

On the other hand, starving your mic by not feeding it enough voltage results in distortion.

It's not just about voltage. The mic requires POWER. The formula for power is P = I x E, where I is current and E is voltge. Dropping the voltage from 48 to 12 causes the mic to try to pull more current to work properly.

Batteries are cheap. Keep your mic happy. It will draw what it needs.

Regards,

Ty Ford

Something I haven't been able to figure out is this.
I have a Rode NT4 that is specified to operate on
either 12V or 48V phantom. Using a Sound Devices
preamp set to 15V phantom, the NT4 won't fire
up from trurned "off". Now, if I fire it up with 48V
for the first few seconds I can then back it down
and it will run on 15V.

Hi Ty,

Power drawn from a battery is independent of the voltage supplied. If the mic requires 100mA (let's say - then it will draw 100mA, whether the voltage is 12V or 48V). I am referring to the power needed from the battery to the mixer in order to supply 12V or 48V. Nearly all mixers use 1.5V x 4 or less = total of 6V or less at source. To generate 12V or 48V, a DC-DC stepup convertor is used. If you measure the power drained from the batteries to supply 12V versus 48V, the power required is 4X greater at 48V when compared to 12V.

Therefore, if your mic can cope with only 12V phantom, use it - instead of pushing the mixer's circuit to generate 48V.

TS

You're suggesting to many people who can't tell the difference (or don't know what thespecs mean) that in some cases lower votage can be used. Many may have NO CLUE as to whether or not their mic "can cope" with less voltage.

Much less whether or not the phantom supply is antagonistic to the batteries inside some electret mics. (but that's another story.)

Ty Ford

Ty,
But if the mic manufacturer specifies that the model can be used with either 12V or 48V, you're better off using the 12V, right? Or is there more to it than that?

I can't recall where (a review of a Rode, maybe)
but I thought it was claimed "but of course the
best performance will be at the maximum 48V".

I would suggest using what ever the designer has specified.If 12v is specified fine.As Ty stated the designed CURRENT draw for 48v would differ from a designed 12v supply even when the POWER requirement stays the same.The battery longevity would NOT be proportional to the voltage change. If supplying a non designed voltage the current draw would typically change due to the load of the circuit.Bottom line using the design voltage should yield the best result.

So, Jack, you're saying that using 12V would
not give you 4X the battery life as using 48V?
My Rode is specified to use 12V, 24V, or 48V.

An example would be the Rode NT4. It can be used in either 48v, 24v, 12v or 9v.The current draw for each of this ,in the same order is 4ma, 2ma, 2.8ma and 2.4ma. As you can see the current draw at 12v is about 75% of 48v.Depending on your battery powered mixer the loss thru voltage up conversion would increase the difference a bit.On 12v would give about double the battery life.All dependent on mixer and mic.
But in essence TS is right the 12v setting on a mic designed for this would allow extended battery life.

We can always do a simple experiment to test whether mic can cope with a lower voltage or not. Plug it into mixer with your normal XLR cable connection and set the voltage to 12V or its lower setting. Talk to the mic and see if audio is coming out from mixer? Yes - you are in luck. I run all my Sennheiser ME66s and MKH50s + MKP70 at 12V phantom and have not encountered any problems with audio.

Thanks for that Jack. While we're on the subject of Phantom Power, some cheap mixers that SAY they offer 48 V Phantom Power, may, in fact, deliver 48 V and be able to power one mic.

On the down side, some of these mixers don't have the guts to power a full complement (8 ch, 16 ch, whatever) of mics, especially if those mics happen to be the hungry sort requiring more mA (milliamps) than the circuitry can supply.

Regards,

Ty Ford

And what about the sensitivity, and capability to handle high
SPLs without distorting at 48V vs. 12V or 9V with
the NT4?

Yes, I vouch for that statement. I once had a cheap mixer that could power up 2 mics at 48V. When I plug in the 3rd mic, all 3 mics died :-(. That mixer is, needless to say, in the dumpyard.

****

I did another experiment for the benefit of our members here. Using a 4 channel Sound Devices mixer (model 442), if I use 12V phantom, one pair ME66 (+ K6 power unit) and one MKP70 all works (together). If I plug in my MKH50 (just one of them), all of the mics fails. Pushing the voltage from 12V to 48V, any combinations of mics works.

(Note that Sennheiser says phantom is 48V, not 12V. So, by lowering the voltage to 12V, I am essentially on my own).

But, if I want to be stingy on batteries, I could couple the 442 with my MixPre (a 2 channel mixer). Run the pair of MKH50s off the MixPre (48V "factory setting") and the remainder on the 442 at 12V phantom.

You can easily experiment with your mix of mics and mixers and find which combinations can operate at 12V (provided the mixer allows you to use 12V and 48V) and you can optimise your battery uptime - knowing that the mics will still receive adequate power.

TS

Dave , I don't know if the specs change on the NT4 but I wouldn't expect much change as it is designed for 12v.Using the 9v might take a edge off because although they say you can use a 9v it falls in the 12v design level.

TS, I think we're talking about 2 different things.I'm talking about mics designed for lower voltages ,not using lower voltage on mics designed for 48v.
I believe you'll find Ty is right. If you undervoltage a mic it is not going to do the job at it's best.And after all that is what we want,get the best we can.Well at least thats what I want.

Hi Jack,

You and Ty are right. If the specs says 48V phantom, I will run it at 48V.

Some manufacturers don't publish specs or is ambigious. In such cases, I will experiment to see if mics fare well at lower voltages first. A pretty good example will be the ME66 with K6 powering module. That mic works perfectly well at 12V as well as 48V. No difference can be found for audio quality between 12 and 48. I can't find any specs for K6 phantom voltage requirements.

On the other extreme, the MKH50 cannot work at 12V - no sound. Very clear here. The specs says it clearly - phantom is 48V.

The MKH70 - although specs calls for it to be 48V, I found it can work at 12V as well. I have not made any measurements for audio degradation so far.

I hope I cleared all doubts now? If I am using ME66 or ME67, I will use it at 12V - no point at 48V. If I am using MKH50 or 70, I will be using it at 48V.

Cheers,
TS

I believe I did see a spec for K6P of 12V to 48V on
the Sennheiser site.

Hi Dave,

Thanks. It will explain why K6 with ME66 or ME67 works perfectly at 12V or 48V.

TS