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Double Bass Revisiting the AKB C411 PP Contact Microphone

rickwolff

rickwolff

‘Leave the clams in, let ’em know we're human,'
Supporting Member
Dec 24, 2012
3,609
5,770
Hudson Wisconsin (15 miles from St. Paul/Mpls
#1
First, a BIG Shoutout to John Chambliss who is generously loaning me this microphone to try.

I used to have one some years ago and honestly don't recall why I sold it.

But, I wanted to see if I could get a good sound out of my Palatino EUB using the C411. Well, it appears I can't. There just isn't enough body resonance to create a good sound through this mic. I have also tried a Krivo magnetic which sounds pretty good, but it's a VERY DIFFERENT SOUND, more like a big P bass than an acoustic double bass. I have also tried my KNA bridge wing piezo but I'd have to do some work on the bridge wing to get a decent fit and so far it doesn't seem promising.

It's kind of a shame because the action on this EUB is Really Nice. I bought it from a bass luthier who took the time to set it up properly and it really shows. If I could only get a good amplified sound out of it.

I haven't tried the 'inner tube under the bridge feet' yet, but perhaps that is next.

HOWEVER, I TRIED THE C411 ON MY BIG BASS AND IT SOUNDS TREMENDOUS. It sounds so good, in fact, that I would strongly recommend it IF YOU HAVE A BASS THAT SOUNDS GOOD ACOUSTICALLY. The 411 doesn't quite have the big fullness in the low end that I get from the Xlson, but it does give it a run for its money. And being a 'sealed unit' it seems to be pretty much immune to feedback (I'll have to try pushing it a bit more to see where the ceiling is. I'm going to try it on my '2nd bass' (which doesn't sound nearly as good as my big bass acoustically) and see how that sounds.
 
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#4
I tried the AKG C411 my Eastman V305. This didn't sound very good. Kind of boxy and boomy. I think the top on that bass doesn't move nearly as much as my 7/8 Shen Gemunder.

I put the KNA piezo back on the Eastman and that sounds GREAT. Interesting that different mics and pickups will sound good on one bass but not another. I guess you just have to figure out what works on each bass.

I also pulled my Prodipe out of the drawer (kind of like an inexpensive DPA 4099). I place the mic capsule about an inch in front of the middle of the bridge. That also sounded really nice on the Eastman.

@John Chambliss, Let me know if you'd like to try my Prodipe. I could send it back with the C411 if you'd like to try it.

Finally, back to the Palatino EUB. If only I had known how simple it was to put something under the bridge feet (you don't have to worry about a soundpost falling over). I didn't have any innertube rubber, but I had some waffle-weave rubber that's used for lining kitchen shelves. I cut pieces to fit under both bridge feet and the tone was 100% better. It gets rid of the thin-sounding highs and has a much richer, fuller sound.
 
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#5
upload_2021-9-24_14-20-21.png

Here's a shot of the freq response of the C411. This explains the "boom". You'd have to adjust eq or placement for it.
 
#7
lurk said:
Where did you put it on your bass?
Click to expand...

On my 7/8 bass, I put it just about right over the soundpost. It sounded great.

On my 3/4 it didn't sound very good - kind of boxy. But that bass doesn't sound great acoustically, either. Interestingly enough, that 3/4 bass sounds really good through the KNA piezo and also quite good through my Prodipe mic right in front of the bridge.
 
#9
Rick - No thanks on trying the Prodipe, but I’ll gladly accept some white putty. I use the AKG on my backup Kay bass, and it seems to work well enough on this bass. It’s also a good backup for the Realist Life Line on my carved bass. Like you, I tried it on my BSX Allegro EUB (and an ABG) with marginal success. Bottom line - It’s a very good contact mic for a double bass.

John
 
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#10
I just got a really good deal on C411 L that had been sold then returned without the mounting adhesive, storage bag or any documentation.
Question 1.
How much putty are you guys using? Are you doing multiple small points with the mic hovering over the top like an Ehrlund or setting it in one bigger glop with no air between the top and mic?
Question 2.
This L version has the wireless pack compatible mini XLR that I’m intending to replace with a regular XLR. I don’t know why it wouldn’t be wired pin 2 hot but the web documentation I could find wasn’t 100% explicit that it was. Anyone ever do this mod?
 
#11
Do some research before you cut the leads. If i'm not mistaken the C411 is based around an electret capsule that likely can't handle 48v phantom power directly. The wireless pack feeds the capsule a smaller current. The XLR version most likely has a small current-reducing circuit housed inside the connector. So if you just cut it off and replace it with a straight connection it may not work.
 
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#12
jlmorgan84 said:
25969638[/URL], member: 258379"]Do some research before you cut the leads. If i'm not mistaken the C411 is based around an electret capsule that likely can't handle 48v phantom power directly. The wireless pack feeds the capsule a smaller current. The XLR version most likely has a small current-reducing circuit housed inside the connector. So if you just cut it off and replace it with a straight connection it may not work.
Click to expand...
Looking at the documentation more closely you’re right. I’ll grab phantom adapter.
 
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#14
Get a B29L from AKG. The connector fits in, the adapter delivers the correct voltage and you have a preamp for it. Runs on 9 volts battery or phantom power.

The one time I tested my very old one (with mini TRS), I used the white Faber-Castell putty with a very thin layer over the whole contact area. I did like that sound more than the sound of my Ehrlund EAP.
Pickup position close but on the outer side of the bass bar about three to four inches below the bridge foot.
 
#15
DoubleMIDI said:
25973256[/URL], member: 165059"]Get a B29L from AKG. The connector fits in, the adapter delivers the correct voltage and you have a preamp for it. Runs on 9 volts battery or phantom power.

The one time I tested my very old one (with mini TRS), I used the white Faber-Castell putty with a very thin layer over the whole contact area. I did like that sound more than the sound of my Ehrlund EAP.
Pickup position close but on the outer side of the bass bar about three to four inches below the bridge foot.
Click to expand...

Thanks! I was just about to ask for advice on a starting position. I’ve got some white Gorilla mounting putty but I’m also going to try some clear reusable Alien Tape. I think it might work well for me but I’d be extremely cautious using it on a more delicate finish.

I got the MPA VL adapter cable because it was what was in stock locally. Even if they’d had the preamp I probably would not have gotten it. I’m not quite a green fascist (yet) but I do vigorously avoid using inessential batteries these days.
 
#16
iAsh said:
…
I’m not quite a green fascist (yet) but I do vigorously avoid using inessential batteries these days.
Click to expand...
I wrote 9 volts battery OR PHANTOM POWER.
So you have both options. BTW you can also use 9 volts (well, 8.4 volts) ready-to-use rechargeables instead of alkaline batteries.

If you don‘t use a AKG wireless Transmitter, the B29L is the preamp intended to be used with all AKG electret mics.
 
#17
DoubleMIDI said:
25974736[/URL], member: 165059"]I wrote 9 volts battery OR PHANTOM POWER.
So you have both options. BTW you can also use 9 volts (well, 8.4 volts) ready-to-use rechargeables instead of alkaline batteries.
If you don‘t use a AKG wireless Transmitter, the B29L is the preamp intended to be used with all AKG electret mics.
Click to expand...

I understood you. The adapter cable does all I need it to do in a smaller package for less money and I didn’t have to order it. Next time I’ll keep my dirty hippie politics to myself.

If anyone is curious about what this adapter looks like inside here are pics.

upload_2021-12-24_17-46-55.jpeg upload_2021-12-24_17-47-26.jpeg

I’d like to compare this to the circuit inside the regular size XLR on the C411 PP. I‘d hoped it would be something you could build fairly easily yourself like this P48 to T12 converter.

2F26E9B3-44C4-4432-A153-F47EF8C9E084.jpeg

This circuit might even work on the c411. I’ll put a meter on the output of my adapter sometime in the next couple of days. But right now it’s Christmas Eve and there’s good food, good whiskey and small children who need to know there is no Santa.
 
#18
Slightly off topic, but closely related:

I have a Prodipe mic (very impressive for the money, btw, and great mounting system) that came with an XLR to mini-XLR adapter. The adapter is designed to take 48V phantom power, and (according to my measurement) converts it to 5V. I have a few preamps I can use with it, but one, an LR Baggs Mixpro, only supplies 9V phantom power, which the mini-XLR adapter converts to about 1.4 or 1.5V. It would be really nice to have a single adapter for this setup: a mini-XLR to TS adapter that would convert 9V to ~5V, but idk how to build one or where to find one.

The mic actually does work well with the 9V phantom, but the output is pretty low, and this setup requires multiple adapters to go from min-XLR to XLR to TS.
 
#19
Your current adapter uses a fixed relation voltage divider. A Zener diode can define a fixed voltage instead.

Please don’t ask me for a schematic.
I’m sure it could be done with a Zener diode which breaks through if the voltage is above its barrier voltage, but applying it to a mixed signal and phantom line is beyond my knowledge.
 
#20
DoubleMIDI said:
Your current adapter uses a fixed relation voltage divider. A Zener diode can define a fixed voltage instead.

Please don’t ask me for a schematic.
I’m sure it could be done with a Zener diode which breaks through if the voltage is above its barrier voltage, but applying it to a mixed signal and phantom line is beyond my knowledge.
Click to expand...

lol ok, I won’t ask. I understand only the bare basics here but my curiosity is sparked. Zener diodes can do some interesting things....
 

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