Takstar CM-60 and CM-63 capsule mods.

[k brown]

Though this stuff would seem more logically to belong in this thread:
https://groupdiy.com/threads/takstar-cm-60-suggested-mods-improvements.84885/
that one has become almost exclusively about circuit mods, so I didn't want to derail that one with this info.

The electronics in the CM-60 and CM-63 seem just fine for my purposes, as I don't do close mic'ing of loud instruments, so don't need the FET bias tweaking to maximize SPL handling, and their self noise, while higher than my other mics, has yet to be audible in actual use during a recording.

Initially spurred on by @kingkorg experiments in this thread:
https://groupdiy.com/threads/diy-m50-capsule.73114/
I was more interested in how the sound of these capsules could be improved, and also converting them to omnidirectional.

The biggest single improvement to the CM-60 capsule is to shave off as much of the front of the capsule as possible, leaving just enough material to securely hold the contents in place. This is what kingkorg did in his mod to make an M50-type mic. The diaphragm is just too recessed behind the front of the grille. The capsule is disassembled (leaving the two halves of the backplate attached), the front removed (I used a razor saw; crude, but effective - followed by some filing) leaving a thin retaining lip, and the stock mesh replaced with a suitable size of stainless steel mesh disc from a plumbing supply, which is more robust than the stock mesh for better protection.

To further convert this to an omni, simply plug the holes in the rear backplate - kk used epoxy; I used Coax-Seal black mastic, so that I can return them to cards if I choose. kk also removed all the spacers between the backplates, but for me that resulted in a sound that was too bright. I later found that leaving in only one metal spacer (and not plugging the holes), still results in an omni, but has a more usable top end (I'm awaiting another pair of '60s to double-check this on, so I have an unmodded one to compare; this could suggest that balancing the top end of these capsules could additionally be done by how many, if any, spacers are used - stay tuned).

I actually like this omni a bit better than my Oktava MK-012 omni capsule, which has a bit of a heavy, somewhat blurred bottom. These compare quite well with the Rode NT45-O!

_________

The unpleasant top end of the CM-63 capsule is also due almost entirely to the front grill. The nasty peak at 7-8kHz seems clearly to be the result of too much material in front of the diaphragm; in the '63's case it's not because the diaphragm is too recessed, as in the '60. By enlarging the outer-ring holes to 3/32", and lengthening every other slot to the bottom of it's bevel, then restoring the bevel, the top boost becomes more even. It's still rather bright for close mic'ing, but because it's more even it can be EQ'd more effectively.

For distant / Classical mic'ing in or near the diffuse field, the top lift is just about right; my reference for that is my Okatva MK-012 cardioids, which have always delivered a tonal balance that's just right in most such cases.

The other thing i like doing with these is plugging just one or two of the rear backplate holes with Blu-Tak or Coax-Seal which nudges the pattern towards subcardioid and warms their sounds a bit (any SDC cardioid, actually).

If the '63's front grill is removed completely (and just plumbing screen in front), the response is quite flat and suitable for close mic'ing.

 

[pmfalcman]

Though this stuff would seem more logically to belong in this thread:
https://groupdiy.com/threads/takstar-cm-60-suggested-mods-improvements.84885/
that one has become almost exclusively about circuit mods, so I didn't want to derail that one with this info.

Your (great) post absolutely belongs there! Organically, so to say. All the modding info in one place, at least for the ease of finding information for present and future generations.
Circuit mods are just a part of the subject. Besides there's not that many of them.

The slots in CM-63 grill - from your description in another thread I thought you went further with cutting. And been wondering "how?" for not being much space there. And, from the photo, it seems that this lenghtening is really just minimal.
Maybe enlarging the central hole would be beneficial? More sound pressure on the central part of the diaphragm would equal to better low end? Or am I wrong? It's a kind of drum after all - middle is LF, sides - HF.

-----
As an aside: it makes me smile to see how things evolved from the first answers to the question: "what to change in these mics? Maybe front grill?"
They were: "Nah, they're fine. Not much to change, maybe the polarisation voltage."

 

[k brown]

Well the moderators may move it over there, if they feel the same.

I modded two of the CM-63 grilles, and I probably didn't deepen the slots in the one I photographed as much as I did the other one; should go back and match the two.

As to how, I neglected to mention that it does require taking the capsule apart.

I made the first mod test to the outer ring of holes and the slots only because of the example of the DPA grilles, and the plate that's in front of the diaphragm of the Primo Em21/23 capsules, both of which leave the outer area of the diaphragm more exposed than the center. I'm leaving it at that because they now sound just the way i wanted; like I said the top end is now very much like my MK-012 cardioids, which for my uses have just the right degree of top lift.

 

[OneRoomStudio]

Is there any reason to not just remove it entirely and replace it with mesh (as you mentioned in your last sentence)? What benefits (if any) do the modified grills have over plain mesh?

I wonder how a small grill made from metal foam (i.e., https://ergaerospace.com/metal-foam-material/) like Josephson mics would sound.

 

[pmfalcman]

As to how, I neglected to mention that it does require taking the capsule apart.

No this "how"

Disassembly requirement is pretty obvious.
I guess...

By "how" I meant the distance between the bevelled edge of the slots and the ring of central holes is quite small.
So tiny elongation or one rides right into said holes.
Now I saw the pics. You went for tiny elongation option.

 

[k brown]

Is there any reason to not just remove it entirely and replace it with mesh (as you mentioned in your last sentence)? What benefits (if any) do the modified grills have over plain mesh?

I wonder how a small grill made from metal foam (i.e., https://ergaerospace.com/metal-foam-material/) like Josephson mics would sound.

As I said in the last sentence of the post, with the grille completely removed the response is quite flat, and I did that on one pair which I'll use as spot/close mics. I also wanted a pair with enough top lift for distant mic'ing, but without the ugly peak at 7kHz.

 

[pmfalcman]

Is there any reason to not just remove it entirely and replace it with mesh (as you mentioned in your last sentence)? What benefits (if any) do the modified grills have over plain mesh?

even at the beginning of his post @k brown states that he wants them for distant micing which benefits from slight hf peak

 

[k brown]

No this "how"

Disassembly requirement is pretty obvious.
I guess...

By "how" I meant the distance between the bevelled edge of the slots and the ring of central holes is quite small.
So tiny elongation or one rides right into said holes.
Now I saw the pics. You went for tiny elongation option.

As I said, the slots on the other grille I modded were deepened more. If you look closely at the photo of the stock grille, the slots are very beveled on the inner edge. I filed all the bevel away, then re-beveled the new edge (I just unintentionally stopped short on the one I photographed.

 

[pmfalcman]

As I said, the slots on the other grille I modded were deepened more. If you look closely at the photo of the stock grille, the slots are very beveled on the inner edge. I filed all the bevel away, then re-beveled the new edge (I just unintentionally stopped short on the one I photographed.

Yes, I read this and inspected the photo closely just after you posted, thank you

Do you feel the bevels are necessary, from the acoustic point of view?

Technically speaking the slots were made with a cutting wheel (faster than using a routing bit) and that's why the bevels. But are they sonically necessary?

 

[k brown]

Just on general principles, a beveled edge has less diffraction than a square edge - audible ??

 

[pmfalcman]

Yes, how much audible can this be?
The long(!) edges are square. And there's more of them. And longer, obviously
Well.. all the edges (holes included) are square except the few shortest ones.

If the bevel weren't really that relevant then maybe these additional 2 mm would give you a nicer, smoother curve?

I'm genuinely curious and asking to learn.


------
I know jack **** on the acoustics but my designerishly artistic-with-technical-twist brain is already designing a jig to elongate these slots in a repeteable and elegant, yet simple way.
As if I needed this. Or expected to do this often...




P. S. Rounded edges maybe?

 

[k brown]

Yes, how much audible can this be?
The long(!) edges are square. And there's more of them. And longer, obviously
Well.. all the edges (holes included) are square except the few shortest ones.

If the bevel weren't really that relevant then maybe these additional 2 mm would give you a nicer, smoother curve?

I'm genuinely curious and asking to learn.


------
I know jack **** on the acoustics but my designerishly artistic-with-technical-twist brain is already designing a jig to elongate these slots in a repeteable and elegant, yet simple way.
As if I needed this. Or expected to do this often...




P. S. Rounded edges maybe?

Dunno - fodder for experiment. The other thing that was in the back of my head is that it's well known that beveled speaker cabinet edges produce less diffraction, and also the Schoeps GFM132 boundary mic has beveled edges.

________

Update on capsule mods:

Best omni on the 'faceless' CM-60 is with both washers in place and the back holes plugged.

Found that with just one washer in place, and the back holes left open, the pattern was closer to what Schoeps calls their 'open cardioid', which is between omni and subcardioid. So only with holes plugged is the pattern fully omni. But with the spacers removed also, the response is too bright to me; Just right with the stock spacers left in and the holes plugged. A little less peak than the Rode NT45-O, which all to the good!

 

[jp8]

If you want to buy CM-60 capsules for modding purposes without having to buy a complete CM-60 mic, here's a link:
https://a.aliexpress.com/_EQNWCO0

I bought one long time ago and it looks and measures the same as the one on my CM-60, so I assume it's a real Takstar. Saves you some money and saves the world some E-waste.

Have you also checked off-axis response one way or another before and after the mod? Unmodded, the 90 degrees off-axis response touches the on-axis response between 6 and 8 kHz.

 

[k brown]

If you want to buy CM-60 capsules for modding purposes without having to buy a complete CM-60 mic, here's a link:
https://a.aliexpress.com/_EQNWCO0

I bought one long time ago and it looks and measures the same as the one on my CM-60, so I assume it's a real Takstar. Saves you some money and saves the world some E-waste.

Have you also checked off-axis response one way or another before and after the mod? Unmodded, the 90 degrees off-axis response touches the on-axis response between 6 and 8 kHz.

I haven't checked off-axis response of the modded CM-63 capsule simply because I know of no way to alter it; it is what it is. Measurements would be interesting to see, but I have no way of doing that.

 

[glitterball]

If you want to buy CM-60 capsules for modding purposes without having to buy a complete CM-60 mic, here's a link:
https://a.aliexpress.com/_EQNWCO0

I bought one long time ago and it looks and measures the same as the one on my CM-60, so I assume it's a real Takstar. Saves you some money and saves the world some E-waste.

Have you also checked off-axis response one way or another before and after the mod? Unmodded, the 90 degrees off-axis response touches the on-axis response between 6 and 8 kHz.

That seller on Aliexpress also has a different capsule entitled "22 microphone capsules Nueman replacement" - do you think that might also be compatible with the CM-63? This is my first post, so didn't want to include a link.

 

[jp8]

I assume you are referring to this one:
https://a.aliexpress.com/_EvJ0Rlw

It was presented here on this forum by @kingkorg . I tried his mods on the identical capsule in my counterfeit KMS 105, but I ended up ruining the capsule. I'm afraid mechanical modifications just aren't my cup of tea. Anyway, I ordered a new one, which you see mounted on the CM-60 in the pictures. The KMS 105 still has the modded & broken capsule on it.

It will also screw on the CM-63 and Akctron T-02A.

Jan

 

[glitterball]

I assume you are referring to this one:
https://a.aliexpress.com/_EvJ0Rlw

It was presented here on this forum by @kingkorg . I tried his mods on the identical capsule in my counterfeit KMS 105, but I ended up ruining the capsule. I'm afraid mechanical modifications just aren't my cup of tea. Anyway, I ordered a new one, which you see mounted on the CM-60 in the pictures. The KMS 105 still has the modded & broken capsule on it.

It will also screw on the CM-63 and Akctron T-02A.

Jan

Thanks for the info - I also saw another similar-looking 22mm capsule from the same manufacturer (HI-LI) that seems to have the widened slots mod that was suggested in that thread: https://www.aliexpress.com/item/1005007701689329.html
Seller doesn't have any feedback.

Edit: I can see now that this design (with wider slots) is the same as the Neumann KMS-105 capsule