ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: 1 [2] 3  All   Go Down

Author Topic: Condenser Mic fault explanation.  (Read 3548 times)

Ken Webster

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Condenser Mic fault explanation.
« Reply #10 on: February 20, 2018, 06:02:57 am »

Transformers don't amplify, they step up or down voltage.  Total energy stays the same (less a little bit of coupling loss).

The explanation of how a condenser microphone works that was given to you by Mike is very good.  It's important that you understand that before you try and fix it.  Repairing items is a great way to increase your electronics knowledge.

Are you using a good high impedance meter?  One thing that you have to get over is that measurements are mostly relative.   Your meter measures resistance, without loading the circuit, impedance, while expressed in ohms is resistance to alternating current and changes depending on frequency.

I am obviously not the greatest at understanding electronics though I have some basics. So yes I will review the comments as you suggest.  I understand that while transformers can step down or step up AC voltage, they can't increase energy (basic entropy).  I was just repeating what I had been told by a PA trainer, though it hadn't made sense to me at the time.  No, I don't have any way to measure impedance, I am just using resistance on a very basic multimeter to check continuity etc.

I was reluctant to take the mic apart completely as that required unsoldering and I could feel resistance when unscrewing the base socket.  Really thought I'd break wires there but it came away fine and exposed the transformer.  Found some thin connections (1 strand) and a wire that had been caught in the base sockets threads.  Luckily an earth wire.   Tightly twisted wires everywhere.  I'll try rewiring the whole thing with new.  If it's component failures, some will be impossible to replace so I may come to a brick wall on this one.  Give it try anyway.

The transformer only has 3 wires so it appears there is a common tap between the 2 coils.  There is a board attached to the capsule that has a tiny black box component marked J7 I can see one leg on top connects to the capsule.  Took a while to figure out it is placed exactly between 2 large solder spots on the board so I'm assuming it's a transistor.  I drew up a schematic and can see that assumption makes sense as one leg is connected to battery + and the other to signal via a 10 uF electrolytic cap.  So it's a simple 1 stage amplifier and DC block.  Still find the transformer a bit mysterious though I can see one signal pin is direct and the other is induced at a different impedance.

In any case, I think my chances are pretty much limited to addressing possible connection issues and anything much more will see the mic go in the bin.


Ken
« Last Edit: February 20, 2018, 06:06:26 am by Ken Webster »
Logged

Mike Caldwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
  • Covington, Ohio
    • Mike Caldwell Audio Productions
Re: Condenser Mic fault explanation.
« Reply #11 on: February 20, 2018, 06:31:57 am »

The transformer would be after the the pre-amp circuit and is used is the dual impedance output selection.

Even the slightest amount of wind hitting a microphone capsule imparts more force on the capsule than just talking into it.

Ken Webster

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Condenser Mic fault explanation.
« Reply #12 on: February 21, 2018, 03:21:14 am »

The transformer would be after the the pre-amp circuit and is used is the dual impedance output selection.

Even the slightest amount of wind hitting a microphone capsule imparts more force on the capsule than just talking into it.

Yep, I thought I pretty much said that, I just had a memory of a comment suggesting it did a little more but on reading through again I don't see that now.  I have rewired the mic and it's just the same as before.  Pick up breath and pop sounds in speech but no actual sound.  The preamp is just 2 caps and 1 transformer.  I can only see a value on the electrolytic cap, so I could try replacing it.  Is that a chance or more likely a damaged capsule?

On a plus, I had success with our only other condenser mic today.  Battery case terminal had gone open circuit, so I replaced the spring's rivet with a brass screw and nut.  I have no idea what this mic is though, looks a bit like a CALREC 1050 but not quite.  I expect it's rubbish but will try it on some instruments to see if it's at all useful.

We hadn't had musicians for quite a while.  Until recently we had been merging singers with recorded music.  We have some musicians again now but only once a month or so and it's usually just a clavinova and drums.  Been surviving with SM58s but it would be nice to have some decent instrument mics for the occasional acoustic instrument, or some super cardioids when we do a carols event with a live band and choir.  However these events are so infrequent, I can't see how I can justify the expense.  We would do better upgrading the AV computers and getting some analysis software and calibrated mics to tweak sound cards and EQ.  That seem to me a bigger bang for buck.  I am just training 2 new sound people and couldn't show them a working condenser mic.  That's what prompted me to have a go at them.
Logged

Mike Caldwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
  • Covington, Ohio
    • Mike Caldwell Audio Productions
Re: Condenser Mic fault explanation.
« Reply #13 on: February 21, 2018, 07:49:10 am »

Before you buy any analysis software buy some working mics.
You can get decent condenser mics for under a $100.

Again what are plugging these mics into, does it provide phantom power.

Ken Webster

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Condenser Mic fault explanation.
« Reply #14 on: February 21, 2018, 04:47:51 pm »

Before you buy any analysis software buy some working mics.
You can get decent condenser mics for under a $100.

Again what are plugging these mics into, does it provide phantom power.

Phantom power is an option from our console, 48V from memory.  We don't have anything that requires it so it should always be off.  However I did discover it turned on a few years ago I supposed it may be possible that the mic got killed that way.  There are no obvious blackened components, its old so there are stains and detritus on the board.  Looking at it, I have a suspicion the electrolytic may have leaked but it could just be part of the general detritus.  It's likely I would have to order one the replace.  Low cost so easily done.  If it has been killed by phantom power, would the capsule definity be damaged?

I can make an argument for software to adjust the whole system spectrum as there is a clear and measurable benefit to the overall sound every day, I can't make an argument for better mics we may use maybe 3-4 times a year when we already have dynamic mics that have been doing the job.  To most, a mic is a mic and they will not see the point.  It's a small church, I have zero budget so every item has to be approved.  It often means ministry leaders purchase items themselves.  If I want misc, I'd have to purchase and donate them.  I think $100 for a condenser mic is a bit optimistic.  I have my eye on a 2nd hand stereo pair of Rode NT5s about half price.  Decent super cardioids appear to be more expensive unless you are looking at domestic video camera ones.  So for $100, I doubt I can get anything that for the audience sound substantially better than our vintage ones if working.  You know the story, you spend a heap of money and nobody notices any difference so they just think your wasting money.

Ken
« Last Edit: February 21, 2018, 06:12:20 pm by Ken Webster »
Logged

Mike Caldwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
  • Covington, Ohio
    • Mike Caldwell Audio Productions
Re: Condenser Mic fault explanation.
« Reply #15 on: February 21, 2018, 06:01:55 pm »

Phantom power is an option from our console, 48V from memory.  We don't have anything that requires it so it should always be off.  However I did discover it turned on a few years ago I supposed it may be possible that the mic got killed that way.

I can make an argument for adjusting the whole system spectrum as there is a clear benefit every day, I can't make an argument for better mics we may use maybe 3-4 times a year when we already have mics because to most, a mic is a mic. 

Ken

What is your "system" makes, models, part numbers, pictures, ect.

As far as software goes....REW is free and not too bad, SMAART is something like $900. Any software tool is not just a plug and play make a pretty picture on your computer screen and your sound system magically sounds better. It takes a bit of practice to know what your looking at and what to adjust, yes I'm still learning!

Ken Webster

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Condenser Mic fault explanation.
« Reply #16 on: February 22, 2018, 04:56:37 am »

What is your "system" makes, models, part numbers, pictures, ect.

As far as software goes....REW is free and not too bad, SMAART is something like $900. Any software tool is not just a plug and play make a pretty picture on your computer screen and your sound system magically sounds better. It takes a bit of practice to know what your looking at and what to adjust, yes I'm still learning!

Video Projector

   NEC MT 1020G/820G

Video Splitter

   Quest tm VGS2

Microphones

    McCardin radio mic set (2ch) (1 head mic and transmitter)

    Shure SM58 x4

    Leem SF-600 x1

    Peavey PV Low Z Cardioid Dynamic x6

    Condenser mic of unknown brand

CD Player

    Denon DWR-840

DVD/Video Player

    LG DC593W
   
Mixing Desk

   Yamaha MR-1642

Graphic Equalizers

   Yamaha Q2031, A (FOH), B (FB)

Amplifiers

    QSC MMX1450 Power Amp (FOH)
   
    Perreaux 3000B Power Amp (FB)  (2x Line isolation units Redback A2513)

Speakers
 
    Fold Back
   
        Interlink 1201F 2 in use, 2 spare 400W 8 ohm

    FOH
        Built Up 2 of

      Enclosures:   100 L
      Tweeters:   Motorola KSN 1 142 Piezo
      Horns:      Ross KSN 1 151
      Drivers:   Selenium 12PW3C-E
      Crossovers:   Jaycar Kit CX-2612 with load resistors on HF

    Cables 4 x 7.5m 14 AWG.

PCs

    PC1 XP (Sound) backup Maxtor One Touch 3 mini

    PC2 Vista (Video presentations)
« Last Edit: February 22, 2018, 05:18:23 am by Ken Webster »
Logged

Mike Caldwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
  • Covington, Ohio
    • Mike Caldwell Audio Productions
Re: Condenser Mic fault explanation.
« Reply #17 on: February 23, 2018, 12:26:41 am »

Your system is pretty simple and straight forward. Before investing in any software and the needed mic and IO interface I would look at upgrading some areas of your system, some of the mics, the wireless mics, a more professional amp for the monitors, that's a nice home stereo amp but that's why you needed the input interfaces.
Don't forget proper gain structure and system configuration goes a long way in
making everything play nice together.

Are your speakers two way with just a woofer the piezo tweeter or three way.

Ken Webster

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Condenser Mic fault explanation.
« Reply #18 on: February 23, 2018, 03:38:23 am »

Your system is pretty simple and straight forward. Before investing in any software and the needed mic and IO interface I would look at upgrading some areas of your system, some of the mics, the wireless mics, a more professional amp for the monitors, that's a nice home stereo amp but that's why you needed the input interfaces.
Don't forget proper gain structure and system configuration goes a long way in
making everything play nice together.

Are your speakers two way with just a woofer the piezo tweeter or three way.

Agree, it is a straight forward system.  While I am not happy with the FB the Perreaux is not the problem, it's much the same power as the current FOH amp in fact, it was the FOH amp up to 2 years ago.  It developed an issue dropping the rails unevenly on power down and the previous FB amp (ETI480 kits) had lost a channel completely (cooked board).  We replaced FOH with the QSC (bought 2nd hand) and I temporarily put in a Pioneer A400X on foldback duty (did an amazing job), while Bill Crampton serviced the Perreaux which is now like brand new, possibly better than due the to cap upgrades.  Shure it isn't balanced and is devoid of features which is why it's on isolators and driving foldback.  It's way better than the speakers it's driving IMO.  So considering where we have come from, this is a considerable upgrade.

There are in fact a lot of issues you are not aware of.  We have a stage in the corner which is the bane of my PA life (someone thought it was friendlier).  Causes: echo around the stage area, FB echos muddy sound out to the audience and directly competes with and degrades FOH sound quality.  The FOH speaker position is difficult, if I put them on either end of the stage, 1 of them covers little audience and mostly just fires into the brick wall on that side  echoing interference patterns across the hall.  I have tried lots of placement options which all have problems.  Currently I have the FOH enclosures stacked vertically with the top one inverted, both aligned down the centre of the hall.  This seems to give the most even coverage and best penetration to the rear of the hall (vertical dispersion control).  Cons are, FOH source to one side of the stage and feedback as side coverage pattern runs along the front of the stage.  However,  feedback rarely happens, we are used to managing it I guess.  Even so, my advice is never ever under any circumstances put a stage in a corner, just don't do it.  There seems very little we can do acoustically with this stage position.  Any acoustic structures would adversely affect the visual design of the hall as the end wall has architectural symmetry.

Personally I think the only solution is to get an acoustic engineer consult to redesign the performance area in a more suitable location.  Pretty sure, that's not going to happen.

All I can really do is continue to keep up maintenance and gradually chip away at upgrades.
The most sub standard equipment right now is possibly the PCs.
I have just stripped down and rebuilt the sound PC just to keep it running long enough to research an upgrade.  This involved a thorough internal dedust, deoxit every plug, socket, card etc & replace battery.  This PC is the main music source for us so hopefully this will stave off further boot fails for a while.

I have tried several times over the years to EQ the system by ear.  As I am now 60, I can't hear a thing above 10kHz so have no idea how that sounds to the young ones.  The pizos are underrated so I killed the top end a bit.  Been no complaints.  I'd like to get analysis software just for some quantified evidence on the system and room response and to provide a consistent standard spectrum response.  Currently it is as good as I can do by ear but well, I don't think it's quite right.

Anyway, we have digressed from the original thread, do you think the most likely explanation for the Electret mic issue is a damaged capsule?  I thought this was the better of our 2 condensers though both are quite ancient.  I probably have a bit invested in these mics as they are the 1st things I got working after starting PA at the church all those years ago.

Ken

« Last Edit: February 23, 2018, 03:59:50 am by Ken Webster »
Logged

Mike Caldwell

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1439
  • Covington, Ohio
    • Mike Caldwell Audio Productions
Re: Condenser Mic fault explanation.
« Reply #19 on: February 23, 2018, 08:34:33 pm »

For decent low cost condenser mics look at the Audio Technica AT2021 or the side address version the AT2020. I have a few of the AT2020's and they work well. Stepping up a little will get you  the AT Pro37, great all purpose condenser mic, I have eight of them myself.

Post a couple pictures of the stage area.

ProSoundWeb Community

Re: Condenser Mic fault explanation.
« Reply #19 on: February 23, 2018, 08:34:33 pm »


Pages: 1 [2] 3  All   Go Up
 



Page created in 0.102 seconds with 25 queries.