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How to make an inexpensive microphone capable of picking up low frequencies that doubles as a speaker and direct box.
The large diaphragm of this microphone will pick up more of the low frequencies when recording a kick drum or bass guitar.
Sound recording engineers have been using this trick for years, and Yamaha has also made a commercial speaker microphone called the SubKick, that usually retails for around USD$300.
I was able to build this mic for under $20 by "scrounging" various parts out of old junk. Even if you need to buy all the components, you should be able to build this mic for a fraction of the price of the retail version.
This design goes slightly beyond the SubKick, as far as electronics are concerned, with a dual coil design, and internal direct injection (DI) box.
You should be comfortable using a power drill and a soldering iron, and be able to read a schematic diagram. There is a little sewing, but it isn't too difficult.
The large diaphragm of this microphone will pick up more of the low frequencies when recording a kick drum or bass guitar.
Sound recording engineers have been using this trick for years, and Yamaha has also made a commercial speaker microphone called the SubKick, that usually retails for around USD$300.
I was able to build this mic for under $20 by "scrounging" various parts out of old junk. Even if you need to buy all the components, you should be able to build this mic for a fraction of the price of the retail version.
This design goes slightly beyond the SubKick, as far as electronics are concerned, with a dual coil design, and internal direct injection (DI) box.
You should be comfortable using a power drill and a soldering iron, and be able to read a schematic diagram. There is a little sewing, but it isn't too difficult.
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Signing UpStep 1Materials and Tools
Materials
- 6.5" dual coil woofer speaker (4ohm). I pulled this one from an Altec Lansing multimedia system that had a blown amplifier.
- 10" drum. Cheap is okay, but you'll want something with lugs that screw into the shell, not springs or T-rods that screw into couplers. I found this one for $2 at a second hand store.
- Two miniature bungee or elastic cords. I got a 4 pack for $2.50
- Crimp on terminal rings. I paid $2.50 for a dozen
- Adjustable hose clamp (the same diameter as the magnet of your speaker). This was about $1.50 at the hardware store.
- Female mounting flange for 3/8" microphone stand and small bolts to mount it. I got this at Parts Express
- 2 sq. ft. of speaker grill cloth. Also at Parts Express
- Thread
- Male XLR 3pin panel mount connector and mounting screws
- Two 1/4" TS (mono) female phone jacks (at least one needs a tab for a normalling connection)
- A six-pole four-throw rotary switch (I scrounged my switch from a 4-way printer "data" switch box), or you can use Mouser part no. 105-SR2921F-34S
- 100 ohm potentiometer, also called a variable resistor
- two knobs (for pot and rotary switch)
- Two DPDT toggle switches (on-on)
- A SPST toggle switch
- Resistors: 100k ohm, two 10k ohm, 10 ohm
- 100nF capacitor
- 1:1 ratio audio isolation transformer (pulled from a second hand 270-054 I got for $1)
- metal container to hold and shield transformer, and mounting hardware
- heat shrink tubing or electrical tape
- connecting wire. 22ga or 24ga is fine.
- short microphone stand (another second hand store find)
- Small adjustable wrench
- Drill
- Soldering iron and solder
- Wire stripper/crimper
- Scissors
- Sewing needle
- Screwdrivers
- Small hack saw
- Ruler, or other measuring device
- Sharp hobby knife
- Marking pen
- Rotary tool
- Drum key
- Pliers, tweezers, or other soldering aids
- Adjustable calipers
- Cutting mat
- label maker
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The speaker will be used to the low frequency and the mic to the mid and high.
Can I just wire the speaker (4 ohm) in series with a mic (600 ohm) like a solution to the low resistence (impedance) prolblem?
Speaker + mic = 604 ohm. The mixer input works well to 600 ohm.
Is there some power (watt) problem in that wire. Thanx.
The best option is to run the speaker an mic separately into two separate channels of the mixer, and mix them together using the mixer. This way you can use the EQ in the mixer to remove the high frequency component from the speaker signal.
I would not use them in series as you describe. The speaker coil may reduce too much of the high frequency of the microphone, and the speaker may try to drive signal into the microphone.
Balanced is better when using longer cable runs, and/or in electronically noisy environments- simply, it helps reject noise. Over short runs you can run unbalanced. Be careful about going directly into a high-z preamp with a 50W rated speaker. you may want to have a pad/attenuator to start with.
I used a simple 1:1 transformer to balance the signal, although it probably does not do a very good job at impedance matching. If you use an impedance matching transformer, you can balance the signal with that at the same time. you do not need a second transformer.
I hope this answers some questions. If not, just reply to this comment, and I'll do my best to help.
Here I have quoted from my original text, in italic, and added notes in between in normal text:
Circuit ExplanationThe configuration of the coils can be changed by the rotary switch (S1).
Position 1 Single: A single coil of the speaker is used (Coil B) (4ohms), both 1/4" jacks are wired in parallel with the coil. Coil A is disconnected. Any input will drive both Coil B and the DI's input.
Position 2 Series: Two coils are wired in series(8ohms), with the two 1/4" jacks wired in parallel. either input will drive the coils (a 8 ohm load) and the DI input
Position 3 Parallel: Two coils are wired in parallel (2ohms), with the two 1/4" jacks wired in parallel. Either input will drive the speaker coils (now a 2 ohm load) and the DI input
Position 4 Damping:
Coil A is normalled to the 100ohm potentiometer, which will electromagnetially (and perhaps inductively) dampen coil B. When a 1/4" plug is plugged into CN1, the potentiometer is disconnected, and the input (CN1) directly drives coil A only.
Coil B is wired in parallel with the 1/4" output jack CN2. A signal input here will drive coil B (at 4ohms) and the DI input.
In all positions, the output then passes through the phase flip switch, through a -20db pad, to one side of the transformer. The transformer's secondary outputs through the XLR jack. (The pins on the XLR jack are labeled.)
There's always some coil connected with the DI side. You can use either input in any position of the rotary switch and get sound out of the DI. Since there are different coils, loads etc. (that I haven't experimented with) each will affect the sound differently.
If you want a straight DI, disconnected from any speaker coils, you can install a switch to disconnect the coils from the input jacks. Or use a normalling jack for CN2, and the coil side connects to the normalling contact. (I just built myself a couple of regular DI boxes as separate units)
With the back of the pot facing you, and the three leads pointing down (toward you):
wire the lead on the left to the positive of the speaker (+) ,
the middle lead of the pot goes to the
-positive of the output -the tip of 1/4 in. jack,
-or pin 2 of XLR (if you are using my bitmap schematic in the comments)
-or pin 3 of XLR for yamaha schematic
the last lead of the pot on the right goes to connects with
-the common of the speaker (-),
AND either the
-shield of the 1/4in.
-or pin 3 of XLR (my schematic)
-or pin 2 of XLR (if using yamaha schematic)
maybe a little confusing, but you should have a variable volume control. You could mount it with a knob, or you could just hot glue it to the back of the speaker to set it once and forget it.
hope this helps :)
Yes it should work directly into the mixer. You may need to use a mic level input. Some mixers have mic/line switches on the 1/4in. jacks, others you need to use the XLR jack.
Yamaha wires the hot (+) lead of the speaker to XLR pin 3 (cold), the cold (-) lead of the speaker to XLR pin 2 (hot), and XLR pin 1 (ground) to a lug of the drum. (closest thing to ground.)
Here's a pic of the Yamaha I found online:
Of course, this instructable is for the more complicated dual-coil with DI box.
I may suggest running it through a compressor if you have one. It is meant to be mixed with a normal microphone.
I have not tried it with a bass guitar cab yet. But you should get some really low bass.
It has fantastic bass response, and i have been using it to mic my drum kit. It sounds great.
Feel free to modify my design however you like. Use the original speaker box, or use a larger drum., or let it hang in mid-air. its up to you.
I have not tried such a large speaker. try it -and write a post about how it sounds :)
I've got tons of speakers, parts, etc. laying around. I simply took an extra 15" woofer and laid it on it's back, on a folder blanket, inside the kick drum.
I left the front head and hoop off of the kick and wired an XLR connector to the speaker.
From what I remember, it sounded awesome! It provided ridiculous sub-frequencies (like big r&b/hip hop kick.) Of course, it was possible to dial back that excessive bass to taste.
Also, when I threw a blanket over the drum, the signal was completely isolated, even while recording in close proximity to bass and guitar. I would assume that this was because the 'mic' diaphragm was so huge and not easily moved by more distant sounds.
I experimented with suspending the speaker inside the drum, but that forced me to change the angle and wasn't nearly as good. I don't remember exactly how so. It could have been that it focused the sound too much on the beater.
It's also possible that part of the mojo of lying the speaker on its back was simply due to mass and resonance. After all, I was using a high quality woofer with a heavy magnet. Possibly an EV.
Aud1073cH, your design looks great. I've got some junk drum shells lying around. I'm gonna have to try making one like yours, sometime.
To everyone else, just experiment. This is a safe and fun project to play with, and can teach you about both mics, speakers, and how they work.
To ever
you can wire straight to pins 2 and 3 of an XLR connector (no ground)
or you can use a 1/4 connector for an unbalanced signal, and run it through an external DI if you want to balance it.
I could be wrong.
I had one, so I just wanted to see what it would sound like. (why do guitarists have so many different kinds of pickup configurations?)
This page also helped me figure out what I was doing:
http://www.ethanwiner.com/gadgets.html
If there is a good thrift store nearby, pick up a used one of these 4 way parallel printer switches - you can usually find them for US$3 to $5 - they have way more poles than you need, but you can just ignore the extras. Just look at the way the wires go from the DB25 connectors to get an idea of the pinout ( i.e., pin 1 on the common plug, and pin 1 on A through D connectors.)
A quick search found this new one:
http://www.buyextras.com/bbimadasw4pc.html
You could also use a 9 pin serial switch, if there are enough poles.
If the local thrift store/ second hand store doesn't have them, perhaps there is a computer recycling store near you, or on eBay?