wooden DIY percussive stompbox

[johnson]

Ok guys i have almost zero experience in electronics, so this might seem like a dumb question. i couldnt find the answer online tough.
I made a very simple stompbox. I mounted an old speaker on an old speakercase and voila.
the only thing it need to do is produce a bass kick sound when stomped with a shoe. i added some pictures below. My only problem is that it's still to trebly for my liking. So i would like to add a simple adjustable low pass filter to it. I'm thinking of something like a guitar tone potmeter, wich will give me an adjustable knob to determine my cutoff. any tips on what would work in this setup?

[Kipper4]

I'm no Expert but cant you eq the signal with the amp?
Putting a passive LPF between the speaker (mic) and output jack will lose a lot of signal.
It might be worth thinking of putting a active LPF in there though. Just my hacker opinion.

Ps side note I would tie a knot in the cable inside the box so it doesnt get pulled off the speaker connections in the heat of a gig/practice and you end up with an air drum.

[GGBB]

A speaker isn't that far removed from a guitar pickup, so I think a tone control would work pretty well assuming you choose the right values for pot and cap. You probably want a big cap in this case, and best would be bipolar. I'd take a wild guess and try two polarized 100µF caps in series back-to-back with a 250k pot. I could be way off though.

[stallik]

Made a number of these using speakers and piezo elements then got hold of a device from peterman in Aus. Best I've come across, used a tiny speaker with a bit of plastic glued from one side of the frame to the other and damping the centre of the cone. It also has in impedance matching transformer. Massive bass. Try damping the cone a little to see if that helps

[PRR]

> lose a lot of signal.

He apparently has OK signal now.

He has a metric boat-load of impedance to fool around in. The filter input should be over 4 Ohms, the filter output should be under say 400K Ohms... we never have 100,000:1 of impedance to play with! Here we do.

> too trebly .... adjustable low pass filter.....

Would be nice to have a clue what frequencies you want to cut.

Also: a "simple" filter may not cut enough for a mechanism which is strongly top-heavy (dynamic transducer with light cone). A 2-pole may give a better "thud".

Here's my rough cut. You can hang a capacitor right across the speaker, and the roll-off is sharpened by the voicecoil inductance. Since we do not know the inductance or what frequencies we want to clobber, some experimentation is needed. Get your clip-leads and all your spare electrolytic(*) capacitors, experiment.



That will take off a lot of the "paper tone" edge. Make it a tenor instead of soprano. Since this is not a melody instrument, you probably want to filter it out of the melody range, down in the rhythm/percussion area, and more/less depending on how it fits with other instruments. The 100K variable resistor and about 0.01uFd cap lets you trim 160Hz to over 1,600Hz. If you only want the deeper thuds, use 0.02u or 0.05u here.

(*)Technically this should be a non-polar capacitor. However the "back voltage" is never large, and only for instants. Conventional polar e-caps will last decades.

The caps should be rated for more than 2 Volts. (You probably can't find them that small, any higher voltage is fine.)

[johnson]

I'm no Expert but cant you eq the signal with the amp?
Putting a passive LPF between the speaker (mic) and output jack will lose a lot of signal.
It might be worth thinking of putting a active LPF in there though. Just my hacker opinion.

Ps side note I would tie a knot in the cable inside the box so it doesnt get pulled off the speaker connections in the heat of a gig/practice and you end up with an air drum.

I'm wiring it to an old 5.1 set subwoofer, wich doesn't have a filter. the knot in the cable is a good idea tough

A speaker isn't that far removed from a guitar pickup, so I think a tone control would work pretty well assuming you choose the right values for pot and cap. You probably want a big cap in this case, and best would be bipolar. I'd take a wild guess and try two polarized 100µF caps in series back-to-back with a 250k pot. I could be way off though.

i was guessing something like that, is there any way to find out what i need?

> lose a lot of signal.

He apparently has OK signal now.

He has a metric boat-load of impedance to fool around in. The filter input should be over 4 Ohms, the filter output should be under say 400K Ohms... we never have 100,000:1 of impedance to play with! Here we do.

> too trebly .... adjustable low pass filter.....

Would be nice to have a clue what frequencies you want to cut.

Also: a "simple" filter may not cut enough for a mechanism which is strongly top-heavy (dynamic transducer with light cone). A 2-pole may give a better "thud".

Here's my rough cut. You can hang a capacitor right across the speaker, and the roll-off is sharpened by the voicecoil inductance. Since we do not know the inductance or what frequencies we want to clobber, some experimentation is needed. Get your clip-leads and all your spare electrolytic(*) capacitors, experiment.



That will take off a lot of the "paper tone" edge. Make it a tenor instead of soprano. Since this is not a melody instrument, you probably want to filter it out of the melody range, down in the rhythm/percussion area, and more/less depending on how it fits with other instruments. The 100K variable resistor and about 0.01uFd cap lets you trim 160Hz to over 1,600Hz. If you only want the deeper thuds, use 0.02u or 0.05u here.

(*)Technically this should be a non-polar capacitor. However the "back voltage" is never large, and only for instants. Conventional polar e-caps will last decades.

The caps should be rated for more than 2 Volts. (You probably can't find them that small, any higher voltage is fine.)

the frequency i want to filter are those above 100hz at it's minimum, so i'm guessing 0.05u cap?
Again i'm totally clueless when it comes to wiring, including the way it is written down. is this how it's supposed to be wired?