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JJ Audio Mics Milkbone Mod (MXL 991) VS Neumann KMi84 Condenser Microphones
View Poll Results: Which file is the Neumann KMi84???
JJ Audio Milkbone vs KMI84
27 Votes - 65.85%
KMI84 VS JJ Audio Mics Milkbone
14 Votes - 34.15%
Voters: 41. You may not vote on this poll

Old 22nd March 2010
  #31
Gear Guru
 
drBill's Avatar
Quote:
Originally Posted by illacov View Post
Whats up with all the views and only a handful of votes?

"input, need input!!"

Peace
Illumination
WAV files and you'll get more votes. Cheap pre's, mediocre instruments and mp3's are the bane of internet comparisons. MP3's are worthless for this application IMO. (not saying you used a mediocre instrument or cheap pre, but did you? heh heh j/k) Put up waves and I'll vote.
Old 22nd March 2010
  #32
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Haz-Mat-Strat's Avatar
 

Hi Michael,

I have two renditions of this mic at this time, each with different configuration on the ports. I am continuing to evaulate the configuration of the ports and the frequency response and will research this further. On one of my tests will be focusing on leaving all of the bars intact and making the slots longer and wider. This will keep the Helmholtz resonator more intact. The current configuration in the first photo, is an aproximation of the Neumann KM84 open area on the ports.

The whole theory behind the ports is that it is a Helmholtz resonator and the tuning of the port is dependant upon reflection from the bars in the port to provide the proper resonant frequency to tune the capsule.

This is why I respectfully disagree with your aproach to eliminate the side bars completely. The tuning of the chamber is dependant upon reflection. Your design negates and minimizes the resonant frequency so the capsule is "untuned" by the Helmholtz resonation process provided by the added side bars.


That would be like taking 80% off the top of a guitar (Helmholtz resonator)to change the frequency response.


The changing of the components and the circuit change was a much bigger change than the ports. The tone of the microphone changed dramatically. The harsh edge was eliminated and the mic became more accurate. The change in the ports was much more subtle.

Attached Thumbnails
JJ Audio Mics Milkbone Mod (MXL 991) VS Neumann KMi84-p3210048.jpg  
Old 22nd March 2010
  #33
Gear Maniac
From Wiki:

"Helmholtz resonance
is the phenomenon of air resonance in a cavity. The name comes from a device created in the 1850s by Hermann von Helmholtz to show the height of the various tones. An example of Helmholtz resonance is the sound created when one blows across the top of an empty bottle.

It can be shown[1] that the resonant angular frequency is given by:
(rad/s) , where:
  • γ (gamma) is the adiabatic index or ratio of specific heats. This value is usually 1.4 for air and diatomic gases.
  • A is the cross-sectional area of the neck
  • m is the mass in the neck
  • P0 is the static pressure in the cavity
  • V0 is the static volume of the cavity
For cylindrical or rectangular necks, we have
, where:
  • L is the length of the neck
  • Vn is the volume of air in the neck
thus:
By the definition of density: , thus:
, and
, where:
The speed of sound in a gas is given by:
, thus, the frequency of the resonance is:
The length of the neck appears in the denominator because the inertia of the air in the neck is proportional to the length. The volume of the cavity appears in the denominator because the spring constant of the air in the cavity is inversely proportional to its volume. The area of the neck matters for two reasons. Increasing the area of the neck increases the inertia of the air proportionately, but also decreases the velocity at which the air rushes in and out.
Depending on the exact shape of the hole, the relative thickness of the sheet with respect to the size of the hole and the size of the cavity, this formula can have limitations. More sophisticated formula can still be derived analytically, with similar physical explanations (although some differences matter). See for example the book of F.Mechels [2]. Furthermore, if the mean flow over the resonator is high (Mach number above 0.3 typically), some corrections must be accounted for.

Helmholtz resonance finds application in internal combustion engines (see airbox), subwoofers and acoustics. In stringed instruments, such as the guitar and violin, the resonance curve of the instrument has the Helmholtz resonance as one of its peaks, along with other peaks coming from resonances of the vibration of the wood. An ocarina is essentially a Helmholtz resonator where the area of the neck can be easily varied to produce different tones. The West African djembe has a relatively small neck area, giving it a deep bass tone. The djembe may have been used in West African drumming as long as 3,000 years ago, making it much older than our knowledge of the physics involved.
Helmholtz resonators are used in architectural acoustics to reduce undesirable low frequency sounds (standing waves etc.) by building a resonator tuned to the problem frequency thereby eliminating it.
Helmholtz resonators are also used to build acoustic liners, which aim at reducing the noise of aircraft engines for example. These acoustic liners are made of two components:
  • a simple sheet of metal (or another material), perforated with little holes that can be regularly spaced or irregularly spaced, called resistive sheet,
  • a series of so-called honeycomb cavities (holes with a honeycomb shape, but in fact only their volume matters).
Such acoustic liners are used in most today's aircraft engines. The perforated sheet is usually visible from inside or outside the airplane; the honeycomb is just under it. The thickness of the perforated sheet is of importance, as shown above. Sometimes, there are two layers of liners; they are then called "2-DOF liners", by opposition to the "single DOF liners" (DOF meaning Degree Of Freedom).
This effect could also be used to reduce drag on aircraft by 40%.[3]"

Um, there are references but I am not going to post them. I suspect someone paid attention (somebody didn't) when they were teaching this stuff. This is physics, I am betting.
Old 22nd March 2010
  #34
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Haz-Mat-Strat's Avatar
 

Quote:
Originally Posted by drBill View Post
WAV files and you'll get more votes. Cheap pre's, mediocre instruments and mp3's are the bane of internet comparisons. MP3's are worthless for this application IMO. (not saying you used a mediocre instrument or cheap pre, but did you? heh heh j/k) Put up waves and I'll vote.

Hi Bill

Attached are 2 WAV files. In the same order.

Thanks,
Enjoy
Attached Files

KM84-991 #1.wav (4.30 MB, 799 views)

KM84 - 991 #2.wav (4.30 MB, 817 views)

Old 22nd March 2010
  #35
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Storyville's Avatar
I'll give my listening impressions.

The first clips seems to have more lows than the second. They seem to have the same overall amount of high end, but the second one has more presence of treble. The low mids in the first are very "natural", while the second has low mids that sound more controlled - kind of like compression on just that range. The second seems to have a flatter response across the mid to upper mid range. The first has some dips and peaks, especially some dips in the upper mid (1.5-2) that gives the mic a perceived flat response (working against fletcher-munson curve). The top of the first one is quite bright, but seems to have a very wide and extended lift, whereas the lift in the second one seems more concentrated in the treble range, maybe 9kish.

Now I'm going to download the wav clips and run them through a spectrometer and do some null testing. Just to see how the data compares to my impressions.
Old 22nd March 2010
  #36
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Storyville's Avatar
So, I've highlighted the points of interest in these two freq responses. The left is clip #1, the right is clip #2.
Attached Thumbnails
JJ Audio Mics Milkbone Mod (MXL 991) VS Neumann KMi84-freq-response.jpg  
Old 22nd March 2010
  #37
Lives for gear
Results please
Old 23rd March 2010
  #38
Registered User
 

Perhaps another useful clip would be modded vs unmodded.

Or Joly mod vs jj mod

A mod off- pull out your Helmholtz and let the venting begin.
Old 23rd March 2010
  #39
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MadGuitrst's Avatar
Quote:
Originally Posted by Michael_Joly View Post
You asked me to be more forward in my language, here it is: Your incorporation of vent enlargement in the MXL 991 derives from my own prior art.
This bickering reflects so poorly. I don't get it Michael - you didn't invent modding mics, why do you come off as acting like you're the only one with the right to run a business doing so? You know I like and respect you Michael, but that's exactly how you come off, especially towards JJ Audio (but you and Marik have gone at it more than a few times too) and I just don't get it. And this is not the only thread - it seems like every thread they post you jump in and go on the attack. It's really lousy etiquette, especially from a respected member.....IMO.

So much has been done over at Prodigy Pro, so much discussed at Rec.Audio.Pro (I started reading that newsgroup around 1995-1996) before ANY of this.

Michael, correct me if I'm wrong, but aren't your Oktava 219/319mods based on Scott Dorsey's work?

Myles Boisen was the first person I read about touting the Oktavas. Ty Ford, Michael Molenda, etc. spoke about them.

Some of the rec-audio.pro threads are so old they're not around or difficult to dig up (maybe I'm just not inclined).

Check this rec.audio.pro thread from 1997, including a quote from Michael Molenda and his views of the Mk219 in 1996....and posts from Mike Rivers and Scott Dorsey. In the last post Scott asks what he asks what people think he could make modding Oktavas
Has anyone else noticed the *new* Mix Magazine? - rec.audio.pro | Google Groups

Ty Ford about the 219 "boink" in 1997:
"Boink" resonance on Oktava MK219 - rec.audio.pro | Google Groups

Here's one where you're asking questions to Scott Dorsey and Harvey Gerst about the Oktava ribbon mic in 2003:
Scott Dorsey , Harvey Gerst al, ML-52 Mod Question - rec.audio.pro | Google Groups

The following was published in 2005 but I remember reading about Scott's work back in the late 90s, when I lived near Atlanta (and bought my Mc012s and a couple of MK319s).

- Oktava MC-219/319 Upgrades : Recording Magazine -

Quote:
Oktava MC-219/319 Upgrades
Mechanical and electronic modifications
By Scott Dorsey





As my earlier article on modifying the Oktava 012 microphones seems to have gained some degree of popularity, a number of people have asked me about modifying the Oktava 219 and 319 microphones. This is a rather different sort of article, because the problems that these mics have are very different.

Let me first explain that the Oktava 319 has the same internal mechanism as the earlier 219, in that it has the same capsule and the same electronics, even down to the PC board layout and the supporting brackets. The 319 appears to have been an attempt to fix some of the mechanical problems with the 219’s cabinet, but unfortunately it seems to have replaced them with different ones. Nevertheless, you can make some substantial improvements to both of these mics without even picking up a soldering iron.

Mechanical modifications

If you do nothing else, it is worth the time to make some simple mechanical modifications to the cases of these microphones, because the cases are so severely resonant. Tap one with a pencil and listen to the clear ringing sound it makes, rather than the dull thwap that would indicate a well-damped enclosure. Those resonances can be excited by music too, not just by a sharp rap on the case—hence the problem.

The mechanical problems with these mics are much more severe than any of their electronic problems, so if you just finish the simple mechanical alterations and stop there, you’ll hear a considerable improvement without too much effort. (This is in marked contrast to the 012, where the mods involve swapping components on a very small and tightly packed circuit board.)

Removing the 219’s grille supports

On the 219 the first step is to open the case, remove th e circuit board and put it away in a dry place, then to remove the grille from the inside of the case and cut away the supporting members for the grille, filing them down as carefully as possible. You can then touch up the sections you filed down with a black automotive touch-up lacquer. Clean the glue residue off the grille with acetone or nail polish remover. This opens up the grille considerably. The grille itself can be re-cemented back into place with a 2-part epoxy glue.

A pair of diagonal cutters and a hacksaw will aid in removing the support members, since the body is a very brittle diecast aluminum. The holes in the top of the mic should just be left as is, though you can remove the grille entirely up there if you wish.

Do note that removing the support members from the grille will make the mic more fragile, so if you’re using this under field conditions where it’s going to get beat up, you might forego doing this. Although removing them makes a substantial improvement to the sound, it’s not as great as what you gain from the next mod I describe: damping down the body resonances.

Killing the 219’s body resonance

Actual ringing of the mic case is the most serious problem with these mics. Some of the folks working on these mics have tried gluing felt to the inside of the body with some success, but I find it much easier to use silicone RTV (Room Temperature Vulcanizing) compound—in other words, silicone caulk.

There are basically two grades of RTV: the inexpensive hardware store material (Ace 100% Silicone Caulk or equivalent), which uses acetic acid in its manufacture, or the higher electronics grade (GC Electronics RTV or equivalent), which does not. When working on electronics, it’s very important to avoid the cheaper materials because they deposit some acetic acid on the circuit board, which eventually leads to surface corrosion—to say nothing of their very strong vinegar odor while they cure! But here, we’re just putting the caulk on the inside of the case rather than on a sensitive PC board, so there is no reason not to use the cheap material (as long as we wait a few days for it to cure solidly—and for the stink to subside).

Take the material and glob a nice thick coating all over the inside of the case, being sure not to get it on the grille itself. If you get too much on, it’s no problem to cut it away with a razor blade or X-acto knife to get the board back in. After it’s set, try tapping the sides of the case halves with a pencil and see how much less they ring with the silicone compound applied. Instant sonic improvement.

Damping resonance in the 319

The Oktava 319 appears to be an attempt to repair some of the defects in the 219 design, but—although the body is better damped on it—the grille assembly has even worse resonance problems. It can be helped with RTV on the inside of the microphone body, as can the 219, but reinforcing the 319 grille assembly to prevent it from ringing is still difficult.

I have seen attempts to support the inside of the grille with thick piano wire or electric fence wire, but everything I have seen in this regard has really been ineffective. The only real solution I have seen to the grille resonance problems on the 319 is to tear the grille out altogether and replace it with a more flexible material. Replacing the material on the top is less important than replacing the grille that goes around the outside. A little epoxy glue and some fibreglass window screen is at least a good start toward dealing with these problems. Again, tap on various parts of the grille and listen to how it goes instead of a nice dull thump.

After this is done, go and additionally put RTV around the supports for the grille, and a nice thick layer of RTV on the inside of the body (the bottom part of the case that holds the electronics... and be sure to remove the electronics before you start glopping the stuff in there). This results in a much more solid thump when tapping on the mic in any place.

Some people have said they have removed the grille itself completely and that this results in a great sonic improvement. I have no doubt this does produce a great improvement but it leaves a very delicate capsule unprotected. As always, just keep tapping it with a pencil and looking for a thunk rather than a clang.

If you stop right now and reassemble the microphone, you’ll be happy and won’t have spent much time or money. But if you want to go on, there are a number of electronics changes that can be made, keeping the existing topology, but upgrading a few parts.

Electronic Modifications

Before talking about mods to the electronics of the 219 or 319, it’s important to investigate how the original design works. One modification I consider optional and much more difficult than anything we’ve done so far is removing the baffle on the capsule itself—see the sidebar.

The 219 and 319 printed circuit boards

The design of these mics has changed a lot over the years, and you’ll find that there are four basic PC board layouts. The third and fourth match the schematic shown here.

Revision 1: You can tell the first type of board because the capsule leads are soldered directly to the PC board without any standoffs. Board traces go from the FET to C2 capacitor and to the capsule. C7 on the schematic is replaced with three 1 uF capacitors in series.

Revision 2: This layout uses plastic standoffs to which the capsule wire, C2, and the FET are soldered. This results in lower noise and less trouble with flux contamination. This board can be recognized because C7 is replaced with three capacitors in series but there are standoffs on the front end.

Revision 3: This layout matches the schematic exactly. There is one capacitor for C7, but the reed switches (glass barrel things) are still mounted directly to the rear of the PC board. Most of the mics out there seem to be this revision.

Revision 4: This board does not have the reed switches on the main PC board but has a small daughterboard with the reed switches on it. Avoid this revision if you can, and if you can’t, remove the daughterboard—and therefore the pad and bass-cut functions.

There may be other variations on the electronics out there that I have not seen, so keep your eyes open. Revision 3 and Revision 4 boards may sometimes be seen with plastic FETs instead of metal-can FETs.

How the electronics work

The electronics are comparatively simple. They consist of a single FET that acts as an impedance converter stage, and a transformer that takes care of balancing the output.

Power is supplied on the output jack by the preamplifier, so pins 3 and 7 of the transformer are about 48 V above ground. This means that the center tap of the transformer is also 48 V above ground, and the DC offsets on both sides of the transformer cancel each other out so the transformer doesn’t saturate. So we take the power off the center tap, use C9 to filter any noise or residual signal from it, and then apply it through R1, a very high value resistor, to directly polarize the capsule. We also run it through R10 and C7 to produce a lower filtered voltage that is used to power the front end.

With 48 V charging the capsule up through the very high value resistor, any change in the capsule capacitance will result in a change of voltage on the output because it changes the amount of charge the capsule stores. This is dependent on the resistor being such a high value that it only very slowly affects the capsule charge. The changing voltage across the capsule is read through C2 (which blocks the DC polarizing voltage), and into the input of the FET.

The pad operates by shunting an additional fixed capacitor, C1, across the capsule. This means that the output is reduced, because the total change in capacitance is much smaller compared with the total amount of capacitance there. I don’t really like this method of padding but it’s one that a lot of manufacturers use.

R3 and R4 are a voltage-dividing ladder shunted between ground and the rail voltage. They are used to generate a fixed DC voltage to set the FET bias through R2, another very high-value resistor, so that the FET is just slightly turned on at all times with no signal in the mic.

The FET turns on and off with very tiny changes in the gate voltage. When it turns on, current flows through R6, through the FET, then down through R7 and R8 to ground. Now, the Russian folks designing this thing have done some interesting tricks to compensate for differences in the FETs. R8 is bypassed with a capacitor, and signal can go through the capacitor easily, so adjusting R8 only affects the DC level on the source of the FET. R7 affects both the DC level and the AC level, though. So the factory will drop in different values of R7 and R8 depending on the turn-on voltage and the gain of the FETs they are using on any given day. Since we’re going to be replacing the FET with a much more consistent device, these values are going to be changed to stock ones.

When the FET turns on, it reduces the voltage on the bottom of R6 by pulling it toward ground. So the voltage on the base of R6 is going to be proportional to the amount of movement of the capsule. We block the DC on it with C8, and apply it to the primary of the transformer. The transformer secondary, then, carries that signal out to the microphone preamplifier as a balanced signal.

R5, C4, C5, and R9 make up a low-pass filter network connected to the FET output. When the low-cut switch is turned on, the low-end signal is applied to the FET gate. Since the FET stage is inverting, this means the low-end feedback reduces the low-end response of the system and drops the bass response. This doesn’t seem to me like a good way of doing a bass cut, since it also results in the load on the capsule changing and so it can alter the high frequency response as well.

That’s how it works... now what do we change?

The whole goal of the microphone design is to make sure there is as high as possible an input impedance so the capsule sees as little loading as possible, and to make sure there is as low an output impedance as possible so the transformer loads the FET stage as little as possible. Our goal for these modifications is to make this actually be the case.

First of all, if you encounter any of the Revision 4 boards, remove the daughter board completely and discard it. On these boards, C1, C4, and R5 and the switches for the bass cut and pad are on the daughter board, and by removing the board you lose the bass cut and pad functions. However, removing all of the additional stray wiring which substantially contributes to stray capacitance is essential. If you have a Revision 4 board, you’ll have to live without the bass cut and pad functions (which is not a terrible loss since they both degrade sound quality when used anyway).

Front-end components

The most substantial sonic changes can be made by upgrading all of the parts in the front end. Desolder the FET, the capacitor C2, and the two resistors. Replace the two resistors with 1000 Megohm types. The original resistors are specified at 500M ohms but often substantially lower values can be found in these mics, especially in earlier production. Replacing them with 1000M types will substantially improve the top and bottom end response. Likewise, replacing the 680 pF blocking capacitor C2 with a higher-grade COG type of slightly larger value will improve linearity a lot. The original capacitors use a poor grade of dielectric that results in higher distortion.

Replace the FET with a Toshiba 2SK170BL according to the photograph of the modified Revision 1 board. The original FETs have different pin configurations and come in several variants; you want the center pin of the new FET to be connected to C2 and the other two pins to be connected to the resistors R6 and R7. As long as the flat side of the FET goes toward the capsule, the center pin is connected to C2, and the ground hole is unused, you are fine. Many of these boards come with four-pin metal-can FETs in which the fourth pin is connected to the can of the FET and goes to a hole on the board that is grounded. You can see in all of the photos that these holes are left disconnected on boards using plastic FETs, and we wish to leave them disconnected when we install a new FET.

Because such a huge variety of different FETs were used at Oktava, resistors R8 and R7 are normally selected for each particular FET, as mentioned above in the circuit description. With the 2SK170, we want to have R8 be 2.0K and R7 be 1.78K. Check the resistors in place on your board and if you see something different, replace them with precision 1% types. If you have any question, measure between the junction of R7 and the FET and the junction of R4 and R2; this is the bias voltage being applied to the FET and it should be approximately 1.3V.

Capacitors

Replace all of the cheap electrolytic capacitors with tantalum types. That is, C7, C8, and C9 should be changed from poor-quality 1uF aluminum electrolytics to higher-grade tantalums.

If you encounter a Revision 1 or Revision 2 board where C7 consists of three 1 uF caps in series, replace two of those capacitors with wire jumpers and one of them with a 4.7 uF cap. It is possible, as you can see in the photo of the modified Revision 2 mic, to replace this set of three with a 1 uF mylar film capacitor, and this may bring a slight sonic improvement. Sadly, the one capacitor that would really benefit from replacement with a film cap is C8, for which there isn’t much room. The problem with the film capacitors is that they are substantially larger than electrolytic types.

You could decide to replace C1, C4, C5, and C6 with higher-grade ceramic capacitors, which will improve the quality of the sound when the pad or bass-cut switches are enabled. Unfortunately, I think it does not improve the sound enough for me to ever want to use the pad or bass-cut functions, so I normally just leave them alone. You could make some argument that C5 and C6 are in the signal path even when the bass cut is not engaged, so you might consider replacing them. I don’t hear a substantial improvement with replacing C5 and C6 but it’s not much additional work, so I’ll leave that up to you.

Conclusion

The Oktava 219 and 319 microphones have well-designed and solid electronics and quite fine capsules. Unfortunately the quality of construction and the case designs sometimes leave something to be desired, but I think all of the changes suggested in this article are well worth the effort and can improve a good microphone quite considerably.



Scott Dorsey ([email protected]) is a recording engineer and electronics engineer in eastern Virginia.





Parts Lists

-----------

Electronics

Parts / Quantity / Description / Digi-Key Part

----------------------------------------------

C7, C8, C9 3X 4.7 uF 50V tantalum P2077-ND

C2 1X 820 pF COG ceramic P4860-ND

C3 1X 100 uF 6.3V tantalum P2019-ND

R1, R2 2X 1000M (1G) resistor MOX200J-1000MEG-N

Possibly needed:

R7 1X 1.78K 1/4W film resistor 1.78KXBK-ND

R8 1X 2.00K 1/4W film resistor 2.00KXBK-ND

C5 1X 1500 pF COG ceramic P4863-ND

C6 1X 680 pF COG ceramic P4859-ND

1X Toshiba 2SK170BL FET (not available from Digi-Key)

You might want...

Chemtronics flux remover pen CW9100

Paladin solder sucker PAL1700-ND

---------------------------------------------------------------------

All electronics parts except the FET are available from Digi-Key at 1-800-DIGI-KEY.

You will need to purchase window screening and silicone compound at a local hardware store.

Chemtronics Flux Remover spray and GC Electronics conformal coating are available from Cain Electronics in Hampton, VA, at 757-826-5535. They also sell silicone RTV.

The specified Toshiba 2SK170BL FET is sometimes available from B+D Enterprises (800-458-6053 or B&D Enterprises - electronics, projection lamps for hitachi, sony, mitsubishi, panasonic, samsung) or MCM Electronics (800-543-4330 or Audio and Video, Computer Parts, Batteries, Cable and Wiring at MCM Electronics). They both have a minimum order and do not always stock the 2SK170BL (and no, other 2SK170 variants won't work).

You should know that this is considerably more than the going rate and the parts I am selling aren't any better than anyone else's. I don't want to be in the business of selling parts but I understand that some of these are difficult to get so I am doing this as a service if you have no alternative.

Sidebar: The 219/319 Capsule Baffles—Strictly Optional!

The Oktava capsule is built with a black metal baffle with eight holes screwed to each side of the capsule. This forms a resonant chamber on each side of the diaphragm and increases the high-frequency response of the microphone.

If you remove these baffles, you will get a smoother but a more rolled-off top end. If you use the mics on vocals, you may prefer the sound with the baffle in place. If you use it on horns, you may prefer the sound with the baffle removed.

I don’t recommend removing the baffle the first time around, and I suggest being very careful working around the capsule if you decide to remove it. You will have to desolder the ground lead from the board which is wired to the center post on the diaphragm to remove the baffle; don’t attempt to solder or desolder to the center post because it’s very easy to overheat it and damage the capsule.

Removing the baffle will change the sound, but whether it improves it or not is a matter of taste and application. I include mention of this change here because it’s a useful thing to know about, not because I strictly recommend doing it on all microphones.
Frankly, I'm fatigued from all of this bull****
Old 23rd March 2010
  #40
Gear Addict
 

The first clip is slightly richer, so I'm going to guess that's the Neumann. It's interesting how the frequency response of a mic can change the musical effect of a passage. In the first clip the intrinsic melodic contour of the harmonies sounds like it shifts down in the first few seconds, whereas it sounds like it goes up in the second clip. It reminds me of an optical illusion where the same pattern looks different depending on how you focus your eyes.
Old 23rd March 2010
  #41
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Michael_Joly's Avatar
 

Quote:
Originally Posted by MadGuitrst View Post
...Michael, correct me if I'm wrong, but aren't your Oktava 219/319mods based on Scott Dorsey's work?
No they're not - I'll explain in a minute.

But first. I publicly apologize to the Gearslutz community for my role in creating an argumentative environment here. Next I apologize to Langston and JJ for my challenging response to their debut. I've learned a tough lesson and won't be repeating those mistakes.

To MadGuitrst's question -

In 1993 I was working for dbx Inc. founder David Blackmer at his film sound company Kintek Inc. David and I had done the "Linkwitz" mod to some Panasonic electret capsules. This turned out to be the first steps toward David founding Earthworks mics. As great as the little electret capsules could be made to sound, I was still more enamored of LDC mics and was trying to convince David to also put his great mind to work on LDC mics.

When the Oktava MK-219 became available from Harris Allied in late '93 or early '94 I bought one for $550 (over $700 equivalent now) because this was the least expensive way into LDC research. Drawing on my study with David Blackmer, my work on body resonance reduction, grille modification, circuit topology changes, capsule modification and component upgrades (include alternative FET research and biasing techniques) dates from this time. With the exception of cutting out the 219 grille bars, my work in all of these area is quite different than Scott's.

Because the 219 was the least expensive LDC at the time it attracted reviewer and experimenter interest. It appears Scott and I were doing near-simultaneous work on Oktava mics - prior to either of us publishing our findings.
Old 24th March 2010
  #42
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MadGuitrst's Avatar
Quote:
Originally Posted by Michael_Joly View Post
With the exception of cutting out the 219 grille bars, my work in all of these area is quite different than Scott's.
Could you explain a little more in detail (mods to these mics are not like giant secrets)?

I read a lot from Scott before he ever published his work......years before it was ever published in the rags.

BTW Michael, thanks for the change in direction..... thumbsup
Old 24th March 2010
  #43
Gear Guru
 
drBill's Avatar
Quote:
Originally Posted by Haz-Mat-Strat View Post
Hi Bill

Thanks,
Enjoy
Thanks Jim. The wav files gave a much clearer picture to me of what I was expecting to hear, but hoping not to. The mp3's are definately messing with the transient reponse that your Ac Gtr gives off in spades, but the wav's tell the tale.

The wav labeled KM84-991 #1 is clearly the KM84, although surprisingly, it doesn't sound nearly as "rich" or "warm" as what I expect from any of my 3 KM84's. Really, on these clips, more than "picking the KM84 due to it's richness", I picked the 991 for it's zingy-ness and extrapolated backwards. Perhaps it's the guitar / strings / placement / micpre combo or ??? but in these clips, the 84 doesn't sound that great to me.

At any rate, the comparison was good with the WAV's and it's easy to hear the differences. Everything I needed to know was located between 5.5 and 9 seconds into the WAV files. Clip #2 exhibits the typical constricted zingy-ness that I'd expect from the MXL's. (I have 2 991's and 2 604's - none of which ever get used other than on an occasional dull sounding HH, and VERY rarely, on toms - NEVER on ac gtr.) On your Ac Gtr clips, there's a lack of depth or 3D-ness, and (personal preference) it's way too bright - although I've been known to go for bright and use 451's on ac gtrs, I usually head for the darker km84 or a Gefell 692/M70 which splits the difference mid-way between the 84/451.

All that said, I think you've made some serious strides from what a STOCK 603/604 sounds like. The last time I put one on an acoustic, I vowed to never do it again. It has a horrible phase smear and sounds quite ugly to my ear stock. Your mic is a vast improvement over what I remember. (Still trying to forget.... heh heh)

Michael has said good things about the modded 603/604/991's and I was anxious to hear them. I have not heard his, and I suspect, that my impression of either yours or his would be different on my own sources as is usually my experience with internet clips. That said, what I would expect to hear out of a 604 was still in residence on your clips. I was hoping for better, but honestly, still expecting a little MXL - and to my ears, my expectation was confirmed.

Soon I will be putting up a KM84, stock 184, modded 184, 604 and modded 603 on my favorite small bodied mid-60's martin - 00018 model with a superb picker. That will be interesting. We'll see how the would be contenders stack up to the king. heh heh

Oh, and just to be crystal clear, I have no problem with my bias. heh The KM84 is the U47 of SDC mics IMO.
Old 24th March 2010
  #44
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Piedpiper's Avatar
Quote:
Originally Posted by drBill View Post
Thanks Jim. The wav files gave a much clearer picture to me of what I was expecting to hear, but hoping not to. The mp3's are definately messing with the transient reponse that your Ac Gtr gives off in spades, but the wav's tell the tale.

The wav labeled KM84-991 #1 is clearly the KM84, although surprisingly, it doesn't sound nearly as "rich" or "warm" as what I expect from any of my 3 KM84's. Really, on these clips, more than "picking the KM84 due to it's richness", I picked the 991 for it's zingy-ness and extrapolated backwards. Perhaps it's the guitar / strings / placement / micpre combo or ??? but in these clips, the 84 doesn't sound that great to me.

At any rate, the comparison was good with the WAV's and it's easy to hear the differences. Everything I needed to know was located between 5.5 and 9 seconds into the WAV files. Clip #2 exhibits the typical constricted zingy-ness that I'd expect from the MXL's. (I have 2 991's and 2 604's - none of which ever get used other than on an occasional dull sounding HH, and VERY rarely, on toms - NEVER on ac gtr.) On your Ac Gtr clips, there's a lack of depth or 3D-ness, and (personal preference) it's way too bright - although I've been known to go for bright and use 451's on ac gtrs, I usually head for the darker km84 or a Gefell 692/M70 which splits the difference mid-way between the 84/451.

All that said, I think you've made some serious strides from what a STOCK 603/604 sounds like. The last time I put one on an acoustic, I vowed to never do it again. It has a horrible phase smear and sounds quite ugly to my ear stock. Your mic is a vast improvement over what I remember. (Still trying to forget.... heh heh)

Michael has said good things about the modded 603/604/991's and I was anxious to hear them. I have not heard his, and I suspect, that my impression of either yours or his would be different on my own sources as is usually my experience with internet clips. That said, what I would expect to hear out of a 604 was still in residence on your clips. I was hoping for better, but honestly, still expecting a little MXL - and to my ears, my expectation was confirmed.

Soon I will be putting up a KM84, stock 184, modded 184, 604 and modded 603 on my favorite small bodied mid-60's martin - 00018 model with a superb picker. That will be interesting. We'll see how the would be contenders stack up to the king. heh heh

Oh, and just to be crystal clear, I have no problem with my bias. heh The KM84 is the U47 of SDC mics IMO.
I'm hearing the first one as the 84 as well but don't want to assume too much.

What modded KM184 is this that you mention? Is this one that Michael opened up the rear grills on? I don't remember hearing back about that experiment. What all has been done to it?
Old 24th March 2010
  #45
Gear Guru
 
drBill's Avatar
Quote:
Originally Posted by Piedpiper View Post
I'm hearing the first one as the 84 as well but don't want to assume too much.
I would sure hope so. heh Otherwise, I'll need to sell all my 84's..... heh heh

Quote:
Originally Posted by Piedpiper View Post
What modded KM184 is this that you mention? Is this one that Michael opened up the rear grills on? I don't remember hearing back about that experiment. What all has been done to it?
It was modded by someone who does NOT want to be known as a Neumann butcher, but did it as an experiment. heh His/Her anonymity is safe with me.
Old 24th March 2010
  #46
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Quote:
Originally Posted by drBill View Post
It was modded by someone who does NOT want to be known as a Neumann butcher, but did it as an experiment. heh His/Her anonymity is safe with me.
so can you reveal what was done, generally speaking?
Old 24th March 2010
  #47
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illacov's Avatar
 

Talking

Seeing as how we will be doing some more shootouts in the coming days, I will put this one to bed.

Clip #1 is the KM84

Clip #2 is the Milkbonez.

We are still doing a few experiments on the mod itself, the different venting schemes that you can do to the pre existing vents all offer subtle yet different results to the tuning of the sound of the mic.

I will hint that we are currently experimenting with the actual capsule itself.

The experiment is so far different than the 2 known capsule mods of the 603/991 in that we go in a different direction from either reshaping the capsule housing or re-machining the capsule and inserting a new spacer to retune the capsule.

So far the findings are positive but we are still tweaking away until we feel the mod has fully matured.

I will say this much, me personally I would love to hear what these things sound like (as they are), on a drum kit overhead or even in a room or distance miking application.

The 8kish high end forwardness would I feel serve well for something like a choir perhaps or even something orchestral in nature. Up close would be for some too extra, but somebody recording through darker preamps or perhaps even analog tape might like that extra bit of top end boost (or not heh).

There other microphones out there that are useful in this application, which do not sound as controlled as the km84 in closer applications but sound excellent further away from the source where a close proximity is not always possible.

Peace
Illumination
Old 24th March 2010
  #48
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drBill's Avatar
Quote:
Originally Posted by illacov View Post
which do not sound as controlled as the km84 in closer applications but sound excellent further away from the source where a close proximity is not always possible.

Peace
Illumination
Just a side note : other than the general timbre of the 84, the thing that amazes me more than anything else about the mic is it's "reach" and ability to pull in stuff from a distance that I've not been able to duplicate with any other mic.

These are things that no clip can show, and really, that can only be discovered by using the mic for awhile.
Old 24th March 2010
  #49
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Haz-Mat-Strat's Avatar
 

[QUOTE=Michael_Joly;5231869]No they're not - I'll explain in a minute.

But first. I publicly apologize to the Gearslutz community for my role in creating an argumentative environment here. Next I apologize to Langston and JJ for my challenging response to their debut. I've learned a tough lesson and won't be repeating those mistakes.


Michael

Thank you for your apology to all here in Gearslutz.

I think we are both striving to achieving the same goal. That is to give people a superior microphone that is not currently available in the music stores and improve microphones that people currently own. In each microphone that we mod, we improve someone's overall recorded sound. We both have a passion for making and developing the best product we can.

You have been here a long time and have developed many wonderful mods and have created a "signature sound" that you want to hear from your products. Kudos!! You will continue to develop more mods for mics and continue to research and develop superior products.

I know when I do R&D, I look at all of the information I can find on the subject (including your R&D Michael) and try to come up with the best mod for the mic. I know we both spend a lot of time researching, testing and refining our product for our mods. Even when I feel the mod is finished, I still try to make improvements that will make a difference.

I welcome your posting on any product that we develop and release. I welcome your input, opinions and comments about our products. Any input that helps us improve our microphones helps.


thumbsupthumbsupthumbsup
Old 24th March 2010
  #50
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Piedpiper's Avatar
Quote:
Originally Posted by illacov View Post
Seeing as how we will be doing some more shootouts in the coming days, I will put this one to bed.

Clip #1 is the KM84

Clip #2 is the Milkbonez.

We are still doing a few experiments on the mod itself, the different venting schemes that you can do to the pre existing vents all offer subtle yet different results to the tuning of the sound of the mic.

I will hint that we are currently experimenting with the actual capsule itself.

The experiment is so far different than the 2 known capsule mods of the 603/991 in that we go in a different direction from either reshaping the capsule housing or re-machining the capsule and inserting a new spacer to retune the capsule.

So far the findings are positive but we are still tweaking away until we feel the mod has fully matured.

I will say this much, me personally I would love to hear what these things sound like (as they are), on a drum kit overhead or even in a room or distance miking application.

The 8kish high end forwardness would I feel serve well for something like a choir perhaps or even something orchestral in nature. Up close would be for some too extra, but somebody recording through darker preamps or perhaps even analog tape might like that extra bit of top end boost (or not heh).

There other microphones out there that are useful in this application, which do not sound as controlled as the km84 in closer applications but sound excellent further away from the source where a close proximity is not always possible.

Peace
Illumination
I'm sure there are those that will benefit from your improvements on this mic. I'm also pretty sure that I won't be one of them. That particular area is my main pet peeve in recorded sound and I have a hard time imagining a situation where it would suit me. You'll remember my descriptor above, "unlistenable". If I'm after accentuated air, as in distant micing of a choir, or even on toms or overheads, I would be looking higher up than 8-10k. In addition, I have little interest in a mic that requires electronic EQing to be useable, whether in the mic or downstream. This is one reason why I prefer a U47 or M49 to a U67 or U87.
Old 24th March 2010
  #51
Gear Guru
 
Karloff70's Avatar
 

Quote:
Originally Posted by Piedpiper View Post
I'm sure there are those that will benefit from your improvements on this mic. I'm also pretty sure that I won't be one of them. That particular area is my main pet peeve in recorded sound and I have a hard time imagining a situation where it would suit me. You'll remember my descriptor above, "unlistenable". If I'm after accentuated air, as in distant micing of a choir, or even on toms or overheads, I would be looking higher up than 8-10k. In addition, I have little interest in a mic that requires electronic EQing to be useable, whether in the mic or downstream. This is one reason why I prefer a U47 or M49 to a U67 or U87.
That's very pure of you...lol. If you have any unused 67's or 87's lying around pm me.....heh
Old 24th March 2010
  #52
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Quote:
Originally Posted by Karloff70 View Post
That's very pure of you...lol. If you have any unused 67's or 87's lying around pm me.....heh
I'll let you know if I trip over any next time I clean up the studio. heh
Old 24th March 2010
  #53
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Storyville's Avatar
Quote:
Originally Posted by Piedpiper View Post
I'm sure there are those that will benefit from your improvements on this mic. I'm also pretty sure that I won't be one of them. That particular area is my main pet peeve in recorded sound and I have a hard time imagining a situation where it would suit me. You'll remember my descriptor above, "unlistenable". If I'm after accentuated air, as in distant micing of a choir, or even on toms or overheads, I would be looking higher up than 8-10k. In addition, I have little interest in a mic that requires electronic EQing to be useable, whether in the mic or downstream. This is one reason why I prefer a U47 or M49 to a U67 or U87.
And if you want to spend anywhere between 3,000, and 8,000 dollars I'm sure any of those Neumann's mentioned will do just fine.

I agree that a narrow band boost around 8k wouldn't be appealing to me if I'm recording a choir or orchestra.

I disagree that the sample is "unlistenable."

side note: I also read Michael's initial comment about changing the vents as a pat on the back (?).
Old 24th March 2010
  #54
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Piedpiper's Avatar
Quote:
Originally Posted by Storyville View Post
And if you want to spend anywhere between 3,000, and 8,000 dollars I'm sure any of those Neumann's mentioned will do just fine.

I agree that a narrow band boost around 8k wouldn't be appealing to me if I'm recording a choir or orchestra.

I disagree that the sample is "unlistenable."
To each his own. I found it unlistenable. I know people who would send 8k through the roof to make it sound that way on purpose.

You don't have to spend in the thousands to get a mic that is smooth, natural, transparent and flattering, that doesn't resort to corrective EQ. It is a philosophical approach that renders superior results IMHO, regardless of the price point, relatively speaking.
Old 24th March 2010
  #55
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lakeshorephatty's Avatar
 

Quote:
Originally Posted by illacov View Post
Seeing as how we will be doing some more shootouts in the coming days, I will put this one to bed.

Clip #1 is the KM84

Clip #2 is the Milkbonez.
Phew, my ears do work

Russell
Old 24th March 2010
  #56
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Michael_Joly's Avatar
 

re: stock MXL 991 et al 8kHz narrow band peak -

From an auditory perspective, human "equal loudness" hearing sensitivity is still quite acute at 8kHz - but is increasingly less so at 12-16kHz.
Our hearing doesn't need any help in the 8kHz region from a mic with a peak at that frequency.

From a source perspective, almost no acoustical material we would want to record exhibits a spectral density curve with an energy peak that rises up at 8kHz (fundamentals occur much lower in the spectrum and both harmonic and inharmonic partials decline in amplitude with rising frequency).
Recording a source with a mic that peaks at 8kHz produces a rather unnatural result - the resulting spectral response just doesn't make "sense" psycho-acoustically because it doesn't match any of our learned spectral density "profiles" we've accumulated listening to sound in the real world.

On the other hand, an SDC mic with a response flat to 8kHz but rising a controlled amount up at 12-16kHz does a nice job of providing some compensation for the decrease in sensitivity we experience in that very HF range, helps overcome distant mic'ing HF loss due to air absorption but does not introduce an obviously exaggerated peak that would conflict with a learned psycho-acoustic profile for naturally occurring sound spectra.

This is the spectral curve I achieve with my modification to these SDC mics - flat to 8kHz then rising about 5dB to give an "air" boost at 12kHz.
A "compensatory" response curve that makes sense from the perspectives of auditory sensitivity, source spectral balance and air absorption loss.
Old 24th March 2010
  #57
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illacov's Avatar
 

Talking

Quote:
Originally Posted by Michael_Joly View Post
re: stock MXL 991 et al 8kHz narrow band peak -

From an auditory perspective, our "equal loudness" hearing sensitivity is still quite acute at 8kHz - but is increasingly less so at 12-16kHz.
So our hearing doesn't need any help in the 8kHz region from a mic with a peak at that frequency.

From a source perspective, almost no acoustical material we would want to record exhibits a spectral density curve with an energy peak that rises up at 8kHz (fundamentals occur much lower in the spectrum and both harmonic and inharmonic partials decline in amplitude with rising frequency).
Recording a source with a mic that peaks at 8kHz produces a rather unnatural result - the resulting spectral response just doesn't make "sense" psycho-acoustically because it doesn't match any of our learned spectral density "profiles" we've accumulated listening to sound in the real world.

On the other hand, an SDC mic with a response flat to 8kHz but rising a controlled amount up at 12-16kHz does a nice job of providing some compensation for the decrease in sensitivity we experience in that very HF range, helps overcome distant mic'ing HF loss due to air absorption but does not introduce an obviously exaggerated peak that would conflict with a learned psycho-acoustic profile for naturally occurring sound spectra.

This is the spectral curve I achieve with my modification to these SDC mics - flat to 8kHz then rising about 5dB to give an "air" boost at 12kHz.
A "compensatory" response curve that makes sense from the perspectives of auditory sensitivity, source spectral balance and air absorption loss.
Judging from Storyville's graphs of the KM84 vs the Milkbonez, I think more is going on that either people like or dislike, ASIDE from the 8khz peak.

It just seems like there is more going on in the bass region of the KM84 and the top end of the KM84 is much more neutral in contrast to the Milkbonez.

That being stated, I completely dig the Milkbonez versus the stock 991, which just sounded terrible.
The transient response and just overall increase in headroom was immediate to me.

Seeing as how we haven't quite settled on our final rendition, we are still working on it.

Speaking from the field tests that Jim conducted in the past with some of our sub mini LDCs, he had a mic (Doberman Eastlake) with a JJ67 capsule that had no filtering and a mic (Chihuahua Durango) with an ADK Vienna capsule that had no filtering.

Both mics were aimed at a Madrigal group which was almost 20 feet away from the microphones in a large music auditorium.

Considering that both of these microphones had a pretty good amount of top end response/authority, they did a good job picking up the choir from far away in a large hall.

I would think that a mic with a flat response would not sound the same at the same distance on the same source I'm speaking of.

That being stated, its understood that guys dig the natural sounding (IMHO) timbre of the KM84. I think its an awesome sounding microphone and is an old standby for a reason. As well, the 991 is transformerless, the circuit is completely different and so we definitely comparing apples to oranges here.

I think that both mics have a nice vibe going on however, we are working on getting that top end perfect on our mod

I also think that with a few more refinements, the Milkbonez will have a well established sound which will be very useful for quite a few different sources.

We are actually working further on taming down the top end, to address the sprinkly 8khz peak that folks are referring to and as well, finalizing our approach regarding the vents (hence the two different pictures of the vents).

I think aside from the bass our main issue right now is putting the top end into a decent spot where its enough but not too much and then putting the final seal of approval on it.

I may have to order the stock capsule, so that Jim can do it the way the original clip was presented. I would completely dig that mic on room for a drum kit (sorry).

I usually put my room mic about 20 feet away from the kit. So a mic with that kind of top end can be cool at that distance on a drum kit. Being able to screw on a different capsule to get that result is always helpful.

Stay tuned!

Peace
Illumination
Old 25th March 2010
  #58
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illacov's Avatar
 

Talking

Here are some pictures of the Milkbonez with a Greyhound (U87 mod) and the Red Schnauzer (Ela M251).

Two dogs with a Milkbonez!

Those nice badges are made in Vermont! Yes that's a Swarovski crystal on the Red Schnauzer!

Peace
Illumination
Attached Thumbnails
JJ Audio Mics Milkbone Mod (MXL 991) VS Neumann KMi84-mbonez-dogs.jpg  
Old 25th March 2010
  #59
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Storyville's Avatar
Mike makes a good point - very little acoustic material has fundamental tones at 8khz. Those are generally the upper upper harmonics, still within the realm of hearing without fletch-muns roll off.

Langston also makes a good point - because drums have multiple "fundamentals" and cymbals in particular have natural resonances up at 8khz. So OHs might be a good choice if cymbal clarity is favorable.

Piedpiper makes some very good point - there are "natural" sounding mics well within the lower price points, and some might look for a narrow 8k boost depending on style and such.

For room sound, I much prefer the wide Q natural extension of highs and lows.

Personally, I'd try to work the 8khz notch out - not having it in might help the mids feel a little richer. I'm very interested in the action of the low mids in the 84 vs 991.
Old 25th March 2010
  #60
Gear Guru
 
Karloff70's Avatar
 

This may be naive, as I know very little about mic circuits and their fineties of interaction, but would it be worth you lot trying a transformer out on this Milkbone thing? I say this, as I learned the transformer coupling cap and its size (almost tripled it ...) in my G7 mic is a very good way to play around with the bottom response of the mic and my mic sounds much nicer with more bottom/body AND bottom reach (which is why I thought of it when reading Dr Bill's thought) in a way that it seems this thing could benefit from. Then trim the top a little for slightly less poke and the thing could be very nice indeed. Not that I thought it sounded crap now, but the top feels a touch strident and the body a bit seethrough. Bla bla bla.....
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