To someone who got a TnC ACM-3. Can you help?

  • Thread starter Thread starter tarnationsauce2
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I was reading through the gearslutz and Tape Op threads as I figure I'll have to go through this with the ribbons I ordered... and I didn't see anything about "tuning" the mic. You mention setting yours to a specific Hz and I was curious to get a little more insight to that process, and what it would improve.

I'm sure it's too late now... but a before and after audio sample would have been cool as well.

Thanks for the details and pics.
 
Some of those pics of the ribbons are so loose, I can't believe that would happen in the transport from China to you all. I am dying of couriousity how China will rectify this. Will they make restitution? I flat out told them "THIS IS NOT ACCEPTABLE"

edit Is there any one mic that this problem exists on ? Or is it ALL the ribbon mics. I'm going to be yaking with them later and want all the information/ammunition ahead of time
 
chance said:
Is there any one mic that this problem exists on ? Or is it ALL the ribbon mics. I'm going to be yaking with them later and want all the information/ammunition ahead of time
Click to expand...


Almost 50% of the two hundred or so non-group buy Chinese mics I've worked on have had sagging ribbons. Some times I'll see 4 or 5 Apex 205s in a row with slack ribbons, then I'll see another 4 or 5 that are tuned perfectly. This is also true of the Nady mics I've worked on.

I can't figure out if the ribbons are installed slack, or if the corrugations relax during shipment and allow the ribbons to sag in the gap. I tend to think it is not a factory installation problem - it is almost as easy to install a ribbon in a mic with something close to the proper tension as it is to just allow the ribbon to sag in the gap. And the kind of sagging we're seeing would be so obvious even to the most casual factory inspector. So I think the problem might be shipping-related.

One of my suppositions has to do with packing - if a long ribbon mic is packed with the ribbon face parallel to the floor the ribbon is much more susceptible to being stretched by the force of gravity and its own inertia if the shipping carton is dropped. On the other hand, if a long ribbon mic is packed so the the face of the ribbon is perpendicular to the floor it is much less likely to be damaged if the carton is dropped. This is how I return ship all ribbon mics to my clients - mic turned so the ribbon face is perpendicular to the floor. I've had excellent results so far.

Chance - you may want to confirm that the manufacturer does in fact have a procedure for setting ribbon tension and that there is some inspection of ribbon tension prior to packing. And - have them pack for shipment as I suggest.
 
one thing i've noticed about the way that some of the chinese mics are listed when sold by larger companies through retail websites is that in the specs they are listed as having "x micron low-tension ribbons" as if it's intentional.
i wonder if setting ribbons to lower tensions is a measure-- like the excessive wind protection, aimed at minimizing ribbon damage in overseas transit.
 
eyeteeth said:
I was reading through the gearslutz and Tape Op threads as I figure I'll have to go through this with the ribbons I ordered... and I didn't see anything about "tuning" the mic. You mention setting yours to a specific Hz and I was curious to get a little more insight to that process, and what it would improve.

I'm sure it's too late now... but a before and after audio sample would have been cool as well.

Thanks for the details and pics.
Click to expand...
Yeah I know I should have done a before/after. I was too hasty. I just wanted to be sure I could correct the mics. Sorry about that.

I am not totally sure what the benefits of having the resonance tuned, other than you will know it's not too low or too high. Also, in the case of multiple ribbons (stereo pair), it helps match the ribbons.
I do know that different tunings will give boomier sounds, different output, etc.

It may just as well be good enough to eyeball it too. if you want to match two ribbons, then you would probably want to match them.

I chose the frequencies I did after reading these pages: http://www.lkmusic.co.nz/ribbonfix.htm & http://www.josephson.com/ribbon.html

Setting the frequency is actually pretty easy.
Follow the method for determining a speaker's resonance (Fs) here:
http://sound.westhost.com/tsp.htm

Just omit the amplifier, and replace the speaker with the ribbon element (disconnected from the xfmr) And use a 100ohm resistor.
tsp-f2.gif


I started with the lowest possible amplitude out of the generator. I am not sure what level I had turned it to. But I know it was quite low. Way into the milli-volt region. Make sure you start with very low voltage, if you don't your ribbon will may tear from electromagnetic force.
 
chance said:
edit Is there any one mic that this problem exists on ? Or is it ALL the ribbon mics. I'm going to be yaking with them later and want all the information/ammunition ahead of time
Click to expand...

My ACM4 had good tension on the ribbons.
The ACM3 and 2x ACM2 did not have good tension.
 
Is there a way to know if the ribbon is sagging short of opening the mic up? A specific sound?

The ACM are my first ribbons, they sound good to me but I have no point of reference to compare them too.
 
You can check for ribbon sag very easily. Listen to the mic in headphones, gently tip the mic back and forth so first the front face, then the back face comes to rest parallel to the floor. If you hear a sudden "clang" or "clunk" this indicates a severely under tensioned ribbon flopping about in the magnet gap. Not good.
 
MichaelJoly said:
You can check for ribbon sag very easily. Listen to the mic in headphones, gently tip the mic back and forth so first the front face, then the back face comes to rest parallel to the floor. If you hear a sudden "clang" or "clunk" this indicates a severely under tensioned ribbon flopping about in the magnet gap. Not good.
Click to expand...

Will do tonight - thanks Michael.

I listened to the ACM1,2 & 3 yesterday through a UA M610 & Avalon M5 last night and liked all three very much.

The ACM1 was huge through the M5, very big and warm.

The ACM 2&3 both sounded natural on acoustic guitar; I'm happier with them than the C414 I've been using. The ribbons don't have that unnatural hyped high end.

I'm more keen on those three so far than the ACM LDC Tube mic which has a nice body but harsh/phasey high end (reminds me of the AKG C1000S).

All three ribbons lack high end detail - I'm happy enough with that over a hyped condensor or tube though.
 
tarnationsauce2 said:
I am not totally sure what the benefits of having the resonance tuned, other than you will know it's not too low or too high...
I do know that different tunings will give boomier sounds, different output, etc.
Click to expand...

Resonant frequency set too low (single Hz range) will emphasize sub-sonic rumble - footfall, drum / piano pedal noise etc. And, as you note, resonant frequency set too high (~100Hz) can make the mic mic boomy in the upper bass.
 
China is supposed to get back to me today about this sag problem. I don't know, but there is so little mass and weight to a ribbon, it's hard to believe that gravity can do this. On top of that, with that much sag, if gravity did that (or shaking in shipping) you would think the corrigated folds would flatten out somewhat. (that is if the ribbon is streached) Perhaps it's at the clamps?
 
I've started counting the number of corrugations between clamps in properly-tensioned and sagging-ribbon Apex 205 mics. So far, I've found the same number of currugations between the clamps in either case.

This suggests the currugation folds in some mics are relaxing after manufacture and allowing the ribbons to sag. Becuase if a ribbon was installed very slack I would expect to see more corrugations between clamps than found in a ribbon with proper tension.

I suppose the way to verify this is to do a little good 'ole "destructive testing" ;)
 
Hmm,, so maybe the folds in the ribbons are losing memory. Maybe when they manufacture the ribbons they should increase angle of the folds to compensate for memory loss so when they relax they will be where they're supposed to be?
 
According the to Royer web site, once their ribbons are tensioned to the correct resonant frequency they only relax by 1 Hz. So I don't believe trying to "outguess" the ribbon relaxation by over-crimping is the way to go.

I'm sticking with this being a packing / shipping problem becuase only 50% of the mics I've seen have sagging ribbons. In other words, a good number of Chinese ribbons are corrugated, installed, tensioned and shipped without a problem. The current manufacturing, QC and shipping process must be deconstructed and understood before a solution can be proposed.
 
tarnationsauce2 said:
So I guess it's safe to say that the ACM-3 is not an offset ribbon.
I think that would be easily modifiable with 4 or 8 washers and slightly longer screws. ;)
Click to expand...

Hey TS2, I just discovered the newer Nady RSM-5 mics DO NOT have an offset - just like the ribbon in your ACM-3! I've got two new RSM-5s on the bench now - no offset.

The first RSM-5 mics I saw several months ago came in wooden boxes with a velvet bag and shock mount. These mics had a ribbon motor with an obviously offset ribbon (As well as the RSM-3 "Royer-look" mics). The ribbon in these mics is offset by a 3:1 ratio easily and is very visible.

Now, the RSM-5 is shipping in a cardboard box, no velvet bag, no shock mount. The ribbon clamps have been re-designed to hold the ribbon in the center of the magnetic field. This new ribbon motor is also labeled "R2-2" near the connection terminal - like your ACM-3 motor pics.

Perhaps Nady and their manufacturer got "cease and desist" letters from Royer regarding the use of an offset ribbon. I can see it now - "Vintage" wooden box RSM-5 and RSM-3 mics will start to command a higher value on the used market because they incorporate the illicit "Royer Offset" ribbon ;)
 
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tarnationsauce2 said:
Also, a very cost effective way to make an adjustable ribbon saddle would be to make it screwed in loosely, with about 1/8" of movement. Then simply tighten it down where the ribbon is properly centered and tensioned. This isn't as good as a lead-screw system for fine tuning of resonance. But mfg costs would be about the same as they already are and there'd be at least some level of adjustability.
Click to expand...

You could also do the poor-man's leadscrew design and it would probably work just as well with possibly less engineering.

As with a leadscrew design, the clamp would be in two parts, and you'd clamp the ribbon between them. The back part would be thick enough to run a standard machine screw into the end of it parallel to the ribbon. It would screw into a support brace. You would then create a sandwich with the screw head pulling the clamp down towards the support brace while a spring pushed it away from the brace. Thus, in effect, the spring would maintain the tension on the ribbon up to the limit set by the screw.
 
Ok before I type another word lemme say I am ignorant. I've not owned a ribbon before. :o
From what I have read the ribbon element is really thin and fragile. It just seems that a leadscrew might be like using the jaws of life to open a can of beans. One wrong turn and you have a torn ribbon.

What about a spring loaded tensioner? On one end a slide-clamp with a turret to hook the spring and the other end of the spring attached to the frame. Then maybe a screw stop to prevent excess stretching.

Just an idea... :rolleyes:
 
Somnium7 said:
What about a spring loaded tensioner? On one end a slide-clamp with a turret to hook the spring and the other end of the spring attached to the frame. Then maybe a screw stop to prevent excess stretching.

Just an idea... :rolleyes:
Click to expand...

In fact, it is a very good idea. Something similar was realised in some vintage ribbons.
Unfortunately, needed precision and a few additional parts increase the cost significantly and modern mics do not do it anymore.
 
ribbon wierdness

so... using a flashlight, and studying the ribbon inside the mic, I see the tension is different between my two ACM-3s.

Since I don't have a way of tuning to a specific hz... i decide to plug them both in, play a bit, and see if I can tell a difference between them... then... if needed try to match the ribbon to the one i like.

After doing this, I discover one seems to have more "life" to it then the other one so i decide to go for it, and try and ribbon adjustment.

Upon taking them both apart, I discovered the difference. while the picture mic on the left looks like there a strange light reflection on for the ribbon, that is the ribbon. Almost perfectly smooth. in person, you can see where the folds were, and the really strange thing is the folds don't match the other ribbon. The one on the left seemed to have simple a simple back and forth pattern,(hard to tell) while the mic on the right has more of a "ledge" thing going. Not sure how to describe it. Needless to say, the mic on the right sounds better to my ears.

Kinda like /\/\/\/\
verses /---\__/---\__/---\

It's really hard to tell from the photo, and since there not much fold to the one on the right, they may have been them same

IMG_8079-vi.jpg


IMG_8080-vi.jpg

I decided not to try messing with them... I like the sound of the one, and figure the other needs to be fixed.

Anyone have any suggestions as to who or where?

also... the pattern may be interesting Chance's metallurgist.
 
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