DIY subkick pad

[andywho]

I'm in the middle of building my own version of a yamaha subkick, which is basically a 6" speaker used as a low-frequency kick drum mic.

I've read (and discovered for myself) that an inline pad is a necessity so as to not blow out your mic preamps. I'm assuming an H-pad will work as outlined by tim here:

Here's one of many calculators: http://www.icycolors.com/nu9n/tpad-calculator.html A search for "H pad" or "balanced pad" or "balanced attenuator" will find lots more.

To attenuate the mic signal, you want an input impedance of 1500 ohms and and output impedance of 150 ohms. To attenuate the preamp output, use an input impedance of 10000 ohms and an output impedance of 600 ohms.

a few questions before I break out the soldering iron:

- I measured the speaker resistance at 4.6 ohms. tim recommends an output impedance of 150 ohms. I put that into the calc for a 20db pad, and got R1/2 = 0, R3/4 = 74, R2 = 5. does this sound about right?

- since R1/2 = 0, that just means I'm essentially only using three resistors?

- can I just solder the resistors to the XLR jack like this guy did?:


- does it matter what type of resistors I use? I have a bunch of 1/4 watt carbon-films lying around.

I think that's it. thanks in advance for any and all help.

[andywho]

just a quick update on my own post: I ended up using a 150 and two 1K resistors for the pad, and it worked great. somewhere around 20db of attenuation...or something. either way, it no longer overloads the preamps on the way in.

a few pictures of the process and finished product:








BTW...sounds FANTASTIC.

[Ringwraith]

Cool project!
What do you have over the speaker? Is that a regular drum head?

Cheer
Sean

[andywho]

drum heads are pearl "muffle" heads. pretty easy to find. meant for practice, but work well for this--just like a real Subkick®!

[goldcut]

hey looks cool your subkick!

i want to build one me too!
what kind of speaker is ideal. do any generic 6" speaker will do the trick?

also, can you give where and how you put your resistance for your balanced attenuator and how did you find you needed 1 x 150 ohm and 2 x 1k ohm resistance. It is based on the resistance of the speaker?

thx a lot!

Mathieu

ps.: i found a speaker here, do you think with the spec it would work?

[quote]High compliance rubber suspension Silver gray ceramic cone High-temp aluminum voice-coil Size : 6-1/2â€

[andywho]

mathieu-

this thread at gearslutz should give you more than enough info:
http://gearslutz.com/board/showthread.php?t=22079

as far as the attenuator, the 150 ohm bridges the + and - XLR pins and the 1Ks are inline with the + and - wires. to tell you the truth, I can't quite remember how I got those values (the result of an hour or so sitting confused with an online attenuator calculator), but they made sense at the time, and they seem to do the trick. if anybody has a better sense of these things, let us know!

good luck with the subkick. I rarely record rock drums without it now.

[goldcut]

thanks !

i'll start building my own thing!

[josh_boyes]

what size speaker is best to use or is it just the frequency response that matters.

[sweerra]

What is a nice and cheap microphone for making videos? I want to buy a microphone the kind that go on cameras, I don't have a camera yet so you could help me with that also if you can. I don't want it too expensive, I don't really know prices on microphones i just don't want one that is fuzzy in the background.
_________________________
external keyword tool ~ keyworddiscovery.com ~ keycompete.com ~ compete.com ~ webmasterworld.com

[Zion11]

Hey guys Im also thinking of constructing the subkick myself. Is there a specific speaker or subwoofer and sizes that its required? I have two 6 1/2 JL-Audio subwoofers (JL Audio 6W3v3-8 and JL Audio 6W3v3-4). Are these possible to use for the Subkick construction?

Thanks

6.5" 8-ohm subwoofer
mineral-filled polypropylene cone with nitrile-butylene rubber surround
power range: 40-150 watts RMS
peak power handling: 300 watts
frequency response: 30-300 Hz
sensitivity: 80.13 dB
top-mount depth: 4-3/16"
sealed box volume: 0.15 cubic feet


6.5" 4-ohm subwoofer
mineral-filled polypropylene cone with nitrile-butylene rubber surround
power range: 40-150 watts RMS
peak power handling: 300 watts
frequency response: 30-300 Hz
sensitivity: 80.49 dB
top-mount depth: 4-3/16"
sealed box volume: 0.15 cubic feet