ivan H
Well-Known Member
Who doesn't like a bit of well done talk box. I was hooked the first time I heard Peter Frampton's "Do you feel like we do" & " show me the way" in the late 70's. The thing is, talkbox is not something u can use a whole lot of, in fact its something u use very little of, & these things are expensive. A quick search of music stores shows the Dunlop "Heil" talkbox (Frampton used a Heil) retail at almost $300 here in Australia. This makes building your own an attractive prospect. So wot is "in" a talkbox? Well, very little. Nothing to justify that price. The main component inside a talkbox is something like this
This is a "midrange compression driver". This one that I've been using is a (JBL) Selenium D250 - X GW, that cost $38 at Parts Express & is recommended on their site for use in talkbox's. The other component needed is one of these
This is a "non polarised 100 volt electrolytic capacitor", the type used in speaker crossover networks & cost 2 or 3 bucks. These 2 components are the only electrical components that allow the talkbox to work its magic. Schematically, they are hooked up like this (edit; sorry, mistaken pic posted, schematic posted next post)
Oh, I should have mentioned before for anyone who doesn't know, a talkbox hooks to the OUTPUT of an amplifier. When in use it REPLACES the speaker(s). Ok, the capacitor connects to the + terminal of the driver. It forms a 6db/octave high pass filter that prevents low frequencies from getting to the driver. This is because the driver cannot handle lows, they damage its diaphragm. Anything below 500hz needs to be rolled off. Heil use a capacitor with a value of 15 or 16uf. This puts the 6db roll off at about 1200 or 1300hz. Many people find that they would like more lows than this. I use a 22uf capacitor which puts the roll off a bit lower, around 900hz. The formulae to calculate the 6db/octave rolloff is
C=159000/(R x FC), where C = capacitance in uf, R = Impedance of the driver in ohms & FC = cutoff frequency in hz. The other thing needed is a way in which to fit the hose that goes into your mouth to the driver. U want an airtight fit there. Now the driver is designed to mount by its threaded throat. The thread size is 1 3/8" x 18 TPI. The hose that a Heil uses has an ID of 1/2", an OD of 5/8", making the wall thickness 1/16". U can get the clear polypropylene tubing at any hardware. If u have access to a metal turning lathe u could easily turn up an adapter, or u may be able to purchase one somewhere. Wot I did was to buy the smallest wave guide, or horn that these drivers normally mount to, measuring 4.5" x 4.5" for about 5 bucks, & siliconed an 1 1/2" length of the next size bigger poly tubing into the mouth like so
The driver can now mount the way it was designed to, I could easily mount the whole shebang into a fiberboard box (shielding isn't needed) & when not in use I can unplug my tube & stick a rubber chair leg boot over the little hose (adapter) to stop crap from entering, & its all protected as its below the front face of the horn, like so
& there is my talkbox. I use a dedicated 50 watt tube amp for it so switch to it with an A/B footswitch. I don't have one in the talkbox like the commercial ones do. I'll cover switching for a talkbox & more later. Here's my bus stop. Cheers
This is a "midrange compression driver". This one that I've been using is a (JBL) Selenium D250 - X GW, that cost $38 at Parts Express & is recommended on their site for use in talkbox's. The other component needed is one of these
This is a "non polarised 100 volt electrolytic capacitor", the type used in speaker crossover networks & cost 2 or 3 bucks. These 2 components are the only electrical components that allow the talkbox to work its magic. Schematically, they are hooked up like this
(edit; sorry, mistaken pic posted, schematic posted next post)Oh, I should have mentioned before for anyone who doesn't know, a talkbox hooks to the OUTPUT of an amplifier. When in use it REPLACES the speaker(s). Ok, the capacitor connects to the + terminal of the driver. It forms a 6db/octave high pass filter that prevents low frequencies from getting to the driver. This is because the driver cannot handle lows, they damage its diaphragm. Anything below 500hz needs to be rolled off. Heil use a capacitor with a value of 15 or 16uf. This puts the 6db roll off at about 1200 or 1300hz. Many people find that they would like more lows than this. I use a 22uf capacitor which puts the roll off a bit lower, around 900hz. The formulae to calculate the 6db/octave rolloff is
C=159000/(R x FC), where C = capacitance in uf, R = Impedance of the driver in ohms & FC = cutoff frequency in hz. The other thing needed is a way in which to fit the hose that goes into your mouth to the driver. U want an airtight fit there. Now the driver is designed to mount by its threaded throat. The thread size is 1 3/8" x 18 TPI. The hose that a Heil uses has an ID of 1/2", an OD of 5/8", making the wall thickness 1/16". U can get the clear polypropylene tubing at any hardware. If u have access to a metal turning lathe u could easily turn up an adapter, or u may be able to purchase one somewhere. Wot I did was to buy the smallest wave guide, or horn that these drivers normally mount to, measuring 4.5" x 4.5" for about 5 bucks, & siliconed an 1 1/2" length of the next size bigger poly tubing into the mouth like so
The driver can now mount the way it was designed to, I could easily mount the whole shebang into a fiberboard box (shielding isn't needed) & when not in use I can unplug my tube & stick a rubber chair leg boot over the little hose (adapter) to stop crap from entering, & its all protected as its below the front face of the horn, like so
& there is my talkbox. I use a dedicated 50 watt tube amp for it so switch to it with an A/B footswitch. I don't have one in the talkbox like the commercial ones do. I'll cover switching for a talkbox & more later. Here's my bus stop. Cheers
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but it seems cool.
