[ACM investiupgradifications] All things MICROPHONE

[clintrubber]

I've forgotten about what was actually different w.r.t. the actual motors
between the ACM-2 (lollipop) & the ACM-3 (Ryr/B+O-style).

Anyone remembers ?

Thanks,

  Peter

 

[mushy]

I was under the impression that this company essentially makes three motors: The short 45mm one (ACM-2 & ACM-3) and the longer 55mm AEA R84 style one (ACM-70) and the dual ribbon (ACM-4).

Michael Joly explains here:

http://recordinghacks.com/2008/11/01/chinese-ribbon-microphone-designs/

So I've assumed that the motors and ribbons were the same between the ACM-2 and the ACM-3, just different housings.

 

[clintrubber]

Thanks for that link, had this article in mind but had no idea were to re-find it.
Thanks for posting !

Bye,

  Peter

 

[clintrubber]

Got a question about ribbon-sag of the ACM-mics...

Lovely woodenish 'landscape' ribbon-mic storage boxes, but in case of the ACM-3 ribbon-mic for instance,
is it enough to position the mic so that the magnets are above each other ?
So the mic remains positioned flat (like a pencil on a table), but the ribbon is now stored vertically, like a fence.

Or would this just introduce sag into another equally undesirable direction ? (say touching the magnets)

Storing those wooden boxes vertically ('portrait') is obviously the best and a simple label would help
(and that would also work for the ACM-2 that can not be rotated in its box), but is less convenient.

No idea how sensitive ribbons are w.r.t. sag in the various directions.

Thanks,

  Peter

)

 

[andrewsamuel]

how did you retension it ?

the electronics appear to be surface mount covered in goop [ just a few parts ,transistor i guess ]
should be able to jumper across two wires going into the glob and two wires
comin out of the glob , whether the out transformer is good for this is another ?
but maybe that's part of the problem and they just used the usual one they had
and it's not a match for the electronics ? [ with any luck ]

there's another good one , oh can't give you what you ordered but we'll sub this crap we can't
get rid of instead

Retensioning is pretty easy, but you have to be careful. Here's a good read:
http://www.hometracked.com/2007/08/28/ribbon-mic-sag-and-repair/

A good trick is to use a q-tip to move the ribbon. Also, a drop of alchohol under the ribbon acts like a temporary glue (that totally dissipates) to make screwing the block back on easier.

I'll try bypassing the goop, thanks!

Andrew

 

[clintrubber]

Hi,

Anyone aware of a schematic of the ACM-583 (FET) and ACM-1200 somewhere?

The few seconds I looked inside the ACM-583 it looked like the 'common' Schoeps-style circuit,
as say in the MCA SP-1 etc, but I don't recall a schematic that's extended to having also omni
& fig-8 & the pad- & HPF-switches.

Same for the ACM-1200:
The circuit of the Apex 460 & its supply is around, but that one is not the same,
also other switches etc.


Of course the 'principles' are out there & known, but for convenience a dedicated/complete drawing for these mics
would be nice, so if it's already out there then no own tracing needed.

Thanks,

  Peter

 

[RIMSHOT]

I received most of my parcels last Thursday (ACMP-73 still dealing with Customs) and i had a friend of mine come to the studio with his Royer R-121 just to hear the differences with the ACM-3 mic.
We did a really quick session recording acoustic guitar, electric guitar & spoken voice.

The files (24bit/44.1kHz) are located here: http://rapidshare.com/files/215856168/TNC_ACM-3_vs_Royer_R121.zip.

 

[clintrubber]

Thanks Rimshot for posting these, nice.
On the simple speakers I listened these on first impression was that while there are differences these are not enormous, but must listen elsewhere as well.

Apart from that there's a polarity inversion, or was one of the mics rotated w.r.t. other ?
Could also be a (random) polarity swap fro the ACM-3, if you happen to have another it might be gone.
Either way, it;s easily fixed.

I now recall the different timbres of the Royer because of the offset ribbon, don't know if the ACM-3 copies that.
I'll keep it in mind when testdriving mine.

Bye,

  Peter

 

[Barks67]

Hi All,

first post here. Small observation...

I have just got my second ACM-3, a 1200 and 6 preamps from this group buy.
I bought an ACM-3 from the previous buy and when comparing the two ribbons together, noticed they are polarity inverted with one another.

Anyone else notoce this?

excellent forum btw!

Barks,

Barkley McKay

 

[clintrubber]

Hi Barkley,

Welcome here, enjoy!

W.r.t. the polarity inversion, then it might be a safe bet that the latest batch of ACM-3 are all swapped,
see also my observation above (the ACM-3 being pol.inverted w.r.t. the Royer, at least in the resulting files that Rimshot posted).

Bye,

  Peter

Hi All,

first post here. Small observation...

I have just got my second ACM-3, a 1200 and 6 preamps from this group buy.
I bought an ACM-3 from the previous buy and when comparing the two ribbons together, noticed they are polarity inverted with one another.

Anyone else notoce this?

excellent forum btw!

Barks,

Barkley McKay

 

[mushy]

I bought an ACM-3 from the previous buy and when comparing the two ribbons together, noticed they are polarity inverted with one another.

Yeah. Seems you have a 50/50 shot at polarity with these mics, particularly in the last group buy.

 

[clintrubber]

Aha, we better should be checking our new toys...

Of course simplest to compare to a KnownGoodMic, but us DIY-types might want to make it more elaborate... 

http://www.ethanwiner.com/micpolar.html

Bye,

  Peter

 

[rodabod]

I received most of my parcels last Thursday (ACMP-73 still dealing with Customs) and i had a friend of mine come to the studio with his Royer R-121 just to hear the differences with the ACM-3 mic.
We did a really quick session recording acoustic guitar, electric guitar & spoken voice.

The files (24bit/44.1kHz) are located here: http://rapidshare.com/files/215856168/TNC_ACM-3_vs_Royer_R121.zip.

Those samples actually sound surprisingly similar. I remember hearing a comparison of a few different Chinese models compared to a 4038 on drums though, and the 4038 sounded immensely better. Much bigger, and less muddy.

 

[clintrubber]

Does anyone happen to know if the ACM-3 (so also the ACM-2) also does the offset ribbon of the
'original' ? (Patent Number: 6434252)

No idea how big the difference in sound actually is between front & rear. Rimshot, you had access to a 121, can you tell ?

Thanks,

  Peter

 

[RIMSHOT]

Well, i didn´t had the time to do that check on the offset ribbon really, i just rotated each mic and recorded a second take with the acoustic guitar. The distance between mics & guitar was of 60(+) cm.
The R-121 owner has to come to the studio again in the next weeks so i´ll try to do another session (a better one, hopefully).

 

[andrewsamuel]

the electronics appear to be surface mount covered in goop [ just a few parts ,transistor i guess ]
should be able to jumper across two wires going into the glob and two wires
comin out of the glob , whether the out transformer is good for this is another ?

FWIW, I bypassed the electronics and the hiss is gone. The mic sounds pretty good, if a bit dark. It still has all the extra screens on it, so I suppose that's to be expected.

Cheers!

Andrew

 

[clintrubber]

Well, i didn´t had the time to do that check on the offset ribbon really,

Hi,

I've been toying around with the ACM-mics as well, but so many things to try, haven't made it to trying both sides either.

Let's all keep sharing if we have a minute, good to hear about various experiences.

Like: here two out of my two ACM-583 FET mics look to be swapped w.r.t. their polarity as well (just like the ACM-3).
No big problem, just a bit strange it pops up so often. Maybe their reference was a clone ? 

Bye,

  Peter

 

[okgb]

the phantom powered ribbon  [not working ] makes you wondrer if they even
checked the design ?
Don't conventional models have the a different xfmr from the ribbon and then
drive the electronics ? or two xfmrs ? then how does the 48v make it past the xfmr ?

 

[clintrubber]

then how does the 48v make it past the xfmr ?

Hi Greg,

(ignoring the mic-design & assembly-questions & -wondering for now  )

Have a look at for instance some Shure schematics: the mic-TX-secondary has a center tap
from which the supply is derived. That supply feeds the unbalanced active circuitry the drives the mic-TX-primary.

All the best,

  Peter

 

[crazydoc]

the phantom powered ribbon  [not working ] makes you wondrer if they even
checked the design ?
Don't conventional models have the a different xfmr from the ribbon and then
drive the electronics ? or two xfmrs ? then how does the 48v make it past the xfmr ?

I'm igorant of phantom powered ribbon mics, but it seems you'd just need an appropriate transformer to match the ribbon impedance to a more-or-less conventional phantom powered mic headamp input.