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How do I build a Mic Splitter or perhaps a Combiner?
Old 12th June 2012
  #1
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Talking How do I build a Mic Splitter or perhaps a Combiner?

Hay.
My name is Mladen and I am from Bosnia and I play keyboard and accordion.

Can you give me a scheme of the splitter to the microphone.
I need to have two XLR inputs and one XLR output.
This we need to make a microphone for an accordion.
I hope you understand me what I need.
Thank you all.
Old 12th June 2012
  #2
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Richard Crowley's Avatar
 

It sounds like you are asking for a microphone "combiner" (two inputs to one output). A "splitter" takes one input and splits it to two or more outputs.

The connection for a simple combiner ("Y-cable") is to wire each pin 1 to pin 1 on the other connectors, and the same with pin 2 to each pin 2, and pin 3 to each pin 3.

Note that this method has many potential problems. For example, you cannot adjust the relative levels of the microphones.
Old 12th June 2012
  #3
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Lotus 7's Avatar
Quote:
Originally Posted by maricm View Post
Hay.
My name is Mladen and I am from Bosnia and I play keyboard and accordion.

I apologize if I put the topic on wrong place, this is my first post and I hope to get an answer to the question?
Can you give me a scheme of the splitter to the microphone.
I need to have two XLR inputs and one XLR output.
This we need to make a microphone for an accordion.
I hope you understand me what I need.
Thank you all....
It's not clear if you need a "splitter" or a "combiner".

If you're trying to combine the output from a mic with the output from your keyboard to feed a PA system or a single track recorder, combining the signals in a simple "combiner" probably won't work because of the great difference in the signal levels (the keyboard is "line-level" and the mic is much, much weaker). If you use a hard wired "Y" cable, the keyboard line-level output will be fed into your mic and will probably destroy it!

If that's what you're trying to do, a simple, basic powered mixer will work. Take a look at any of these:

Mackie 402 VLZ3 US$ 100
Behringer Xenyx 802 US$ 80
Samson MDR624 US$ 80
Alesis Multimix 4USB US$ 80

On the other hand, if you're actually looking for a real mic "splitter" - a device that will let you connect one mic to (2) inputs (like a recorder and a PA system) then take a look at the Whirlwind IMP Splitter 1X2.

That device will provide one "direct" mic feed-through (which allows a phantom powered mic to function}, and it also provides a transformer isolated output to a second input device, like a PA system.
Old 12th June 2012
  #4
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Richard Crowley's Avatar
 

It is not clear what signal is coming out of your keyboard? Is it really XLR? Is it mic level? NOTE: It would be very helpful to tell us exactly what make and and model equipment you are using here. What keyboard? What microphone?

If you are trying to combine a microphone-level output from your accordion with a line-level output from your keyboard, then Lotus7 is correct, you really can not do this with a simple combiner Y-cable. At minimum, you would need to pad the line-level (keyboard) signal down to mic level to mix with the accordion microphone, and by the time you did this correctly, you could have got a small mixer and do it properly.
Old 12th June 2012
  #5
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Thread Starter
re

I want to make two microphones in one box and I want put it together a make one out.
Picture is here.
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How do I build a Mic Splitter or perhaps a Combiner?-6439649-2v_662x497.jpg  
Old 12th June 2012
  #6
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Richard Crowley's Avatar
 

What is that? It says "Shure Beta 58.A" But it looks nothing like any Shure microphone I have ever seen. Where are the XLR connectors?

If those are just two Shure microphone capsules (what goes inside a 57 or 58), then you can simply wire them in parallel and then to an output cable or connector.
Old 13th June 2012
  #7
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audibell's Avatar
 

You want to make a two mic pick-up for an accordian and you seem, from your picture, to want to cannibalise the capsules from Shure beta58s?

I do not think you want to combine the signals from your keyboard and accordian?

The capsules from any dynamic mic will work and as Crowley says, you need to combine them, rather than split them.

A simple Y-cable splitter needs a resistor network so the two capsules don't "fight" each other.

Rane Note number 109 Why Not Wye? explains this elegantly. You want to build the networks displayed in figs 3 or 4, depending whether you are coming out with xlrs or tip-ring-shield plugs.

Crown also provides a diagram with resistor ohm values,
Crown International / Knowledgebase / How do I combine two mics into one input?

Happy soldering!
WalterT

Last edited by audibell; 13th June 2012 at 12:50 AM.. Reason: singular toplural
Old 13th June 2012
  #8
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Is it just me, or is that RANE illustration a bit confusing? I'd wager one should proceed with the wiring based on the actual PIN numbers, and not use it as a "this is how it will look while the connector is in your vise" basis. Perhaps misrepresented illustrations (the circles sure look like XLR connectors...) are the norm in wiring diagrams... so "Do as they say... not as you see" might be the rule.
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How do I build a Mic Splitter or perhaps a Combiner?-wye-illustration-copy.jpg  
Old 13th June 2012
  #9
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Richard Crowley's Avatar
 

Quote:
Originally Posted by hbphotoav View Post
Is it just me, or is that RANE illustration a bit confusing?
No, its not just you. It looks confusing to me, also. You can see why they drew them that way, to make it convenient to show the ground (pin 1) wire out the left side, and the signal paths (pin 2 & 3) out the right side.

But considering the likely audience (people not very experienced in wiring XLR connectors) it is rather a disservice to show a diagram like that unless it is accompanied with photos of actual connectors explicitly calling out the pin numbers.
Old 13th June 2012
  #10
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Lotus 7's Avatar
Rane's drawing is just "sloppy". If you're going to represent the XLR connector schematic as a circle with 3-pins inside, why not orient the pins in their proper locations as does the Crown International schematic?

One thing to note, if anyone is interested in building one of these, is that Rane does specify the resistors as 475 ohm 1% as opposed to Crown's spec of 470 ohms. Specifying 475 ohm 1 % resistors encourages the use of good quality metal film parts instead of the 470 ohm RETMA value which would result in using a plain old molded-carbon resistor.

With the Beta 58a output Z of 150 ohms and its level of -51 dB (94dB SPL) before going through the combiner, using metal film resistors (instead of molded carbon) should help keep the added noise down a bit. As drawn, the Rane combiner circuit (when driving a typical 1K input impedance mic preamp) will have an approximate 5.5 dB loss of level from each mic and will raise the effective output impedance of each to 1100 ohms. The output of the combiner should not be used if the circuit has to drive a long mic cable (over about 15 meters) unless you're willing to tolerate some high-frequency loss and to have the Beta 58a's upper resonance peaks (4.5 kHz and 9 kHz) pushed down into the mid-range. However, doing that might just be the ticket for recording a "double-miked" accordion. Who knows?
Old 13th June 2012
  #11
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Thread Starter
re

I will explain.
These are the two heads of sm58 mic and they should be connected to one output and it does not lose dB and kHz.
XLR cable will go into the remote transmitter, which will be bonded to the accordion.
Thanks for all your effort to help me in solving problems.
Old 14th June 2012
  #12
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Lotus 7's Avatar
Quote:
Originally Posted by maricm View Post
I will explain.
These are the two heads of sm58 mic and they should be connected to one output and it does not lose dB and kHz.
XLR cable will go into the remote transmitter, which will be bonded to the accordion.
Thanks for all your effort to help me in solving problems.
There may be a slight language problem with my ability to understand what you would like to do, but as best as I can tell you want to mic your accordion into a single wireless transmitter to send to your sound system and/or a recorder.

Why you're using 2 Beta 58 capsules physically parallel apparently spaced about 100 mm from each other is your business, but presumably you believe it will somehow give you better sound. I can imagine that on the "chord" side of an accordion, since the various notes sound radiate from different areas of the instrument, using (2) mics, spaced will give you somewhat more uniform pick -up of all the chords even with the mics almost in contact with the accordion.

I'm no expert as far as mic placement for optimal accordion recording, but everything I've read and everyone I've ever heard speak about how to do it usually recommends using at least two mics, one a meter or so in front of the chord end and one in front or at a 45 deg. angle to the bass end.

Obviously that won't work if you have to move around very much so we can understand what you're trying to achieve.

Anyway, form your last post, I get the impression that you would like to combine the (2) Beta 58A capsules without loosing any signal level and without any loss of signal bandwidth (kHz). Connecting directly to the wireless transmitter eliminates the possible high-frequency loss due to cable capacitance, so that's not a problem. Combining the mics without using the isolation resistor network can be done by just wiring them directly in parallel. HOWEVER, that will not give you correct "combining" of the two mic signals. If the mics could somehow be in the exact same physical location in space, combining the outputs by wiring them in parallel would actually work. The electrical signal coming for each mic would be exactly the same voltage, the signals would be in phase and would combine like (2) batteries wired in parallel.

The problem with doing that with mics that are physically separate, but are also close enough to pick up the same signal, but with a phase difference because of their locations will not only "load" each others signal resulting in reduced output level, but they will have frequency response "anomalies" such as severe comb-filtering when you play a note that results in a 180 deg. phase shift between the two closely spaced, parallel capsules (which WILL certainly happen with your proposed set up). The other concern about your configuration is the considerable proximity effect of the Beta 58A. At 25 mm from the accordion you will have a bass boost of at least 9 dB at 200 Hz. This can always be toned-down with a HP filter or EQ on your mixer or PA amp, but may create a problem in the wireless transmitter unless the input gain is kept quite low.

Sorry, but there is no passive way (non-amplified) to combine the (2) mic capsule outputs without some signal loss at some (probably many) frequencies. As much as you might like it to happen, the laws of physics still apply here.

There is no harm in trying it, so you certainly can try simply wiring the (2) capsules in parallel and driving your transmitter from the result. It won't damage the capsules. You will get response from both capsules and the signal (even with the comb filtering), might be acceptable for your application. Some frequencies will add and some will cancel out each other resulting in "notches" in your frequency response. Alternately, it would be possible to construct a small portable dual channel pre-amp circuit that was battery powered that could be installed ahead of your transmitter and would be small and light. It's not a simple matter however to do it right. It would work somewhat better in that the signal loss would be eliminated, but the non-uniform frequency response would still be there.

Sorry for the long post and hope you can understand the content. I'm trying to keep it as simple as possible, but it is not a simple subject, and combining two slightly seperated mics very near the sound source is generally not a good idea.

If your budget allows it, using (2) transmitters (one on each capsule) and then mixing the two channels with one panned partly left and one partly right, and possibly adding 20 or 30 msec. of delay on one channel might actually enhance the sound you're trying to achieve. The spatial panning will eliminate most of the comb-filtering (as long as you don't re-mix to mono) and the effect might give your performance extra dimension. Something to think about.
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