Topic: Lo priced forgiving HyperCard or multpattern

[Gutbucket]

Thanks D.  The plots in my post above are from the Microtech Gefell site for the SMS2000 series, from here- http://www.microtechgefell.de/index.php/en/microphones/studio-a-recording/small-membrane-transistor-mics/49-transistormikrofonsystemsms2000. Specifically the M21 hypercardioid capsule.

I was disappointed to find the plots above, currently on the MG site, do not indicate the frequencies of the polars.  It looks to me like that information may have been cut off at the bottom of the images.  In any case the low-frequency polars are left-most and the high frequency polars are on the right.  Upon close examination of them upon reading your post, I can see and relate the high frequency polar behavior to the response graph showing the on-axis and 135 degree off-axis responses.  I can also see how the left most polars do not show the pattern broadening at the lowest frequencies which should correspond to what is seen at the very left side of the on and off-axis response response.  I think that's the mismatch you are noting.

Below are alternate copies of these same M21 polars I have stored on this computer, which do indicate the frequencies for those same polars.   Note that the lowest frequency polar data line is 250Hz, which is just about the point where pattern broadening begins to manifest at low frequencies.  I think that explains the discrepancy.  There simply are not any polar measurements indicated at frequencies where pattern broadening becomes significant down low.  A few questions for you about all this in my next post..

[Gutbucket]

Here's my question based on what you've stated above-

I've long assumed most small diaphragm directional microphones show pattern broadening at the lowest frequencies, and often at higher frequencies as well.  I've assumed that because most of the frequency response data I've seen for various microphones do not show the minimum off-axis response to be an identically shaped line to the on-axis response (minimum response being 180-degree off axis in the case of a cardioid, 135-degree in the frequency plot above for the M210), which would be the case if the polar response was the same at all frequencies.  Instead, I most always see a differently shaped far off-axis curve, usually with sort of a scooped midrange shape, indicating maximal directionality throughout in the midrange, and loss of pattern where the bottom (off-axis) curve becomes closer to the top (on-axis) curve.

Polars often don't show that at low frequencies because they are often not taken at the frequencies at which it occurs.

Here's an example of what I'm talking about (DPA cardioids in this case).  Although obviously smoothed, notice that the off-axis response through 90-degrees off-axis tracks the shape on-axis response closely, just at a lower level.  The 'scooped shape' indicating the pattern widening is only evident in the 180-degree off-axis curve:



The general trend in the shape of the 180 degree off-axis response of the DPA cardioids, is similar to the 135 degree off-axis response of the Gefell M210.  Is this not also the case with the Schoeps MK41?  The polars on the Schoeps site only go down to 1kHz, well above this region of interest, and I can find no off-axis response curves posted at all.

I've looked for this information on the MKH50 and it seems that Sennheiser only publishes on-axis and 90-degree off axis responses, nothing farther off-axis where this kind of behavior would be seen.

Unfortunately I don't have actual response charts for my MG210 pair, but below are actual measured on-axis and 180-degree off-axis responses for a few Gefell cardioids (M94, M20, M300) which the factory provided when I sent these back to for service a few years ago.  All of these show a 'scooped shape' 180-degree off-axis response, with response increasing at the lowest frequencies (and higher frequencies), indicating pattern loss at those frequencies.  These are all very good microphones (along with the DPAs above), generally well regarded for stereo pair recording.  Does this imply they are they all designs with acoustical short comings of the type you describe?

[Gutbucket]

I've never seen off-axis or polars for the large, dual-diaphram ADK TL.  I don't expect they'd look especially pretty, certainly not like high quality SDC responses posted above.  I can only say that in my experience, when used in the super/hyper pattern, the off-axis room sound seems natural to me and hasn't posed a problem.  I can EQ the recordings so that both the on-axis direct stuff and the ambient room stuff work without problems, which to me is an indication of decent off-axis behavior.  That's what doesn't work for me using many lesser performing super/hypers.  They get all weird, peaky and pinched sounding.

[edit] Apologies to those who aren't interested for this somewhat OT sidetrack.  I jump on these opportunities to pick DSatz's thoughts on these things whenever the opportunity presents itself.  I do think it's relevant in figuring out which measurements and specifications are indicative of a hypercardioid sounding subjectively "good" or not.

[Gutbucket]

^^^
The first part jibes with my understanding of basic dipole phenomena and roll-off.  With particular implementations all manipulating that basic phenomena via applied design, construction complexity, and manufacturing of their producers.

As for the application of those tools, the second part squares with my move over the years to a pair of spaced omnis at least in part for 'stereo bottom', plus decently behaved super/hypercards for the top providing sufficient directivity from the mids on up (usually 3 or more of them in odd arrays), when the situation permits that kind of thing.  But of course the real world often intervenes and forces other compromises.

Straight cardioid? eh, has it's place, but it's always seemed something of a compromise pattern for me, neither really one nor the other.  Although if limited to two microphones for stereo, then that compromise may be the most appropriate one.  I get that.

[Gutbucket]

EQing the difference signal (to counter the dipole rolloff).

It's the other way around that I still need to wrap my head around, which is where the need for massive DSP really is unavoidable- using arrays of omnis and a bunch of DSP to form higher order virtual directional patterns via "beam forming" arrays.  Mostly measurement and research applications, with most implementations compromised by noise and/or aliasing issues in terms of music recording.  Although apparently not all, I'm aware of one exception at least.

[2manyrocks]

According to this information posted by Shure, a card, supercard or shotgun should be positioned no farther than 50% of Dc.  Since they list cards, supercards and shotguns in the same breath, is this being overcautious or are they saying something more generally fundamental to the effect that we really can't cheat critical distance with a supercard?

http://shure.custhelp.com/app/answers/detail/a_id/82/~/critical-distance-and-microphone-placement

[Gutbucket]

Well, that addresses microphones for speech rather than music.  Most taper applications (except some on-stage or stage-lip recording) place the mics beyond the critical distance.

However, it's conclusion is still true:

What if the microphone must be placed farther away than 50% of Dc?
1. Make the room less reflective via acoustical solutions. This will increase Dc. or...
2. Accept the sub-standard audio provided with a >50% of Dc talker to mic distance.
THERE ARE NO OTHER SOLUTIONS!

Except there is.  The solution is getting and mixing in a SBD feed, which technically is equivalent to adding microphones which are much closer than the critical distance, but that's no more of a "cheat" than their circular logic of answer #1.

Basically it confirms that microphone location is the most important variable we have control over.

[DSatz]

Gutbucket, the broadening of cardioid and (often to a lesser degree) supercardioid patterns at low frequencies isn't a matter of small-diaphragm vs. large-diaphragm; it's a matter of single- vs. dual-diaphragm. Small-diaphragm, dual-diaphragm microphones such as the Neumann KM 88 (see attached curves) and Sennheiser's variable-pattern small microphones have this characteristic as much as larger microphones such as the Neumann U 87.

Having large diaphragms just means that at high frequencies, the pattern also becomes narrower. So see, for example, the polar plots of a Neumann U 47 or any of the later microphones that use the same capsule design (I've attached the M 49 and M 50 graphs on a single page; the M 49 used the same M 7 capsule as the U 47, and its "cardioid" polar graph is shown on the upper right of the four in the picture). They're supercardioid at high frequencies, cardioid in the midrange, and wide cardioid in the bass.

The supercardioid pattern of a dual-diaphragm mike is often better than the cardioid pattern at low frequencies, since the rear diaphragm is brought more into play and the combination begins to approach the symmetry of a figure-8 pattern. When you set these microphones all the way to figure-8, their low-frequency polar pattern can be very good if the two halves of the capsule are well matched in their sensitivity.

--best regards

[Gutbucket]

Yes, I understand that, thanks.

My observation and question above refers to single diaphragm designs.  The observation is that the on-axis and far off-axis (taken at the angle of minimum sensitivity) response plots I've seen for single diaphragm SDCs all show similar overall trends- a more or less equal response with basically only a change of sensitivity over the front on-axis centered hemisphere (plot lines are mostly parallel), but with a significant change of response at the far-off axis angle of minimum sensitivity.  That far off axis response seems to have a common trend among all single diaphragm mics for which I can find data- at low frequencies there is of course the the dipole response roll off for all angles of arrival, which becomes more significant as the intended pattern leans more heavily on the pressure-gradient component verses omni, but the response far off-axis at the angle of minimum sensitivity is never a parallel line to the on-axis response.  Although indicating lower sensitivity at all frequencies, that line always slopes upwards to the left rather than paralleling the on-axis downwards sloping response.

Seems to me that all real-world single diaphragm cardioids/supercardioids follow is same general trend.  This can be seen in each of the plots I posted in reply #34 above. I've no doubt excellent engineering can get things closer to the constant directivity idea, and I'd love to see this measurement data for the MK41 if you can point me to it.  I've no doubt that a single diaphragm LDC would behave similarly in this regard. 

[John Willett]

I was disappointed to find the plots above, currently on the MG site, do not indicate the frequencies of the polars.

That's just the thumbnails - click on the picture and they enlarge and show what frequencies they are measured at.

They are shown on the UK site with the frequencies marked - and there tends to be more info. on the UK site than on the German one for many mics.

[Gutbucket]

Thanks John.

[2manyrocks]

Coming back to the original rubber meets the road question of the OP, what are the lo priced hypercards that tapers have found to make an acceptable recording?  Boltman brought up the Avantone CK-1s for $300. Aren't there some hyper caps for AT853s?  How are they? 

I hate to fork over the bucks for mk41s....especially thinking there's no real substitute for being up close and personal with mic placement, but the other part of me really wants to know how far I can push the envelope.

[Gutbucket]

There is a hyper/super cap for the AT853, but I've only used the 853 cardioid and can't offer you an opinion on the other caps.  You might check out whatever Naiant super/hyper Jon is making now, I don't know the model, and haven't used them, but I've heard good things and the price is very attractive.  The aforementioned ADK TL can probably be found for about $4-500 a pair.

I'll also mention a strange microphone I've grown to like a lot, but is not common around here- DPA 4098H.  It's indented as a miniature hanging choir hypercardioid.  It has an odd integral gooseneck mount and features a small interference tube design like a miniature shotgun.  It is very clean and clear sounding and has a good bit of rolloff at the bottom.  I use them in combination with a pair of wide spaced DPA 4060 or 4061 omnis which compensates for that, but I've found they are smooth and well behaved enough that I can bring up what bass is there with EQ when used alone.  For over bassy material the response without EQ correctly can compensate nicely.  Compared to the AT853 cards they are much cleaner and clearer, but with less bottom. It is a low powered mic using a microdot connection like the DPA 406x.  Power it with 5-9Vdc, unbalanced output, comes with a P48 balanced XLR adaptor.

Thread on the microphone-
DPA 4098H miniature supercardioid

My odd use of them-
Oddball mic techniques thread, p141

They've worked so well in my arrays that they are now replacing the undoubtedly superior MG cards and supers even when the weather is beautiful and there is no foul weather threat.  As a stereo pair alone, the MGs dust them, but in the 6 channel arrays, combined with the omnis, they are pretty close.  And in practical terms they are very small, very light, low-powered, more weather resistant, and much less costly.  New they are about $500 each but you might find them used for around $300 each.

Weird one, probably not what most here are looking for, but worth a mention in this thread.

[2manyrocks]

It's better to pull together all the options and then sort through them than to overlook one and later wish we hadn't.  Mainly I'm curious to see what practical use could be made of a hypercard in m/s, but maybe I should grab a mk41 capsule if a single one ever pops up in the YS. 

Another thought is that wireless mixers like the Behringer XRs and the Soundcraft ui16 have built in recording--could stash one and mics up near the stage and hypercards are no longer needed for concert recording at a distance.   

edit:  4098h discontinued replaced by 4081 pair for $1,100? 

[DSatz]

2many, I see the struggle that you're having, and I agree that it would be painful to pay the cost of Schoeps or Neumann "in-between-super-and-hyper-cardioids" (which is what they are) and still have the results be less than satisfactory. What's more, that risk seems very real from where I sit, despite how good those microphones are.

The main thing that I want to warn against is wishful thinking in this situation. Here's an exercise in realism:

Take an omnidirectional microphone. Place it, say, 6 feet from a sound source in a reasonable-sized room. You'll get a certain mixture of direct sound and reverberant (reflected) sound at that distance; depending on the room, it might seem like an ideal mixture to you, or it might be too dry (not enough reverberation) for your taste, or on the contrary, it may be too muddy and washed-out sounding at that distance; I dunno. Whatever you may think of that pickup quality, if you don't like it, you can adjust the miking distance one way or the other. But let's say for the sake of this discussion that you really like the balance at 6 feet with the omni mike.

So the question is, if you take the microphone pattern that does the most that any first-order microphone (the kind we all use) can possibly do to exclude room sound from a recording--how far do you think you could place it from the sound source and get that same quantitative balance of direct vs. reverberant sound? I ask because if you're recording from the back of a room, you could well be 10 or 15 times farther from the sound sources than you really want to be. So do you think that you can get a "distance factor" of 10 or 15 from any first-order directional microphone, relative to an omni?

The answer is that the maximum physically possible distance factor is only 2:1 relative to an omnidirectional microphone. And relative to a cardioid at 6 feet, the maximum physically possible distance factor would only get you about one more foot of miking distance on top of the 6.

So even the best possible microphones (whatever you or I may consider those to be) can't possibly fix the situations that you're talking about. At best, they can provide "palliative care"--making a terrible situation somewhat more tolerable MAYBE, and not make it worse than it absolutely has to be. If you imagine that any microphone can do anything more than that, you are setting yourself up for disappointment and wasted money. There's no technology that can substitute for putting your microphones in at least a somewhat good place acoustically.

--best regards