Talk box

[marcos_s_p]

Hey guys!

I´ve been thinking for the past days about talk boxes and I figured that I actually could make one without much effort. I mean that because I have a Fender pocket amp that is basically serving as a decoration here at home. So I realised I could basically re-box everything and make use of the small amp and speaker creating a talk box for home use and recording that could likely work better than using any driver speaker from other purposes. Besides, I would get tone adjustments and gain/overdrive as well. Because of that I decided to look into it and opened the amp. For my surprise the bloody amp has 2 speakers connected in series. Hence, here go the questions:

Could I use it just like that and re-box both speakers together sending the sound to the hose? Or due to the very closed environment and proximity will I create a destructive sound interference, hence loosing frequencies? Or will it just enhance the overall volume in a constructive interference?

Also, there is no way to un-solder one of the speakers and adjust the circuit to keep delivering only 4ohms to a single speaker? Because as they are in series, right now the amp is delivering 8ohms that is divided by the two speakers, right?

Sorry if those are dumb questions, but my physics have some "blind spots".

Thank you in advance!!

[PRR]

1/4" (6mm) plywood, a little bigger than the speakers. Trace the outside of the speaker on the plywood. Trace inside that by the width of the speaker gasket, so the gasket/frame will seal but the cone will not slap.

Cut the inner hole.

Clamp that with scrap wood and drill a 1/4" hole into the edge so it comes out in the big hole. (With plywood, this will be a mess, just chop a 1/4" slot.)

Shove 1/4 tube in the hole (use some form of goop to seal it). Attach the speakers, one on each side.

Run 1/4" tubing to mouth.

Use the original wiring polarity (extend leads as needed).

This has real acoustic flaws, but for "small" speakers, especially "flat cone" speakers such as most toy speakers, it may not be bad. (Try this with two 15" speakers and it will sound like a bowl.)

[marcos_s_p]

Thanks PRR,

However, my doubts were not so much about that right now. As talk boxes are usually made out with a single small speaker, I was wondering if having these two could be bad somehow. I mean, if they could interfere with the sound of one another because of the small space. Anyone knows? I believe not, as they are from the same amp and with equal specs and would be delivering same sound from the same circuit. All this makes me believe that they would only increase the overall volume, no?

About the construction, usually I think these pedals don´t take much in consideration the acoustics of it (as they are not really cabinets). Should I worry about that? If so, I´m not sure that I understood your description completely of how to make it. Usually there is one speaker facing up in an enclosure with the hose on top. I was thinking of the same but with the two speakers. But I have the impression that you said to me to put one facing the other...?

Additionally, a 1/4 hose wouldn't be small? I read somewhere that we should use bigger to not loose the acoustics, etc...

Thanks again!
Marcos

[Myampgoesto12]

I don't see a disadvantage with having two speakers, maybe some minor tonal differences but not necessarily bad. To save from spending time modifying the circuit to run a different speaker load I'd simply use both speakers. Build it and see how it sounds. Mini amps have the tone shaping power to probably compensate if need be.

I modified a little RadioShack speaker box with a rubber tube for this effect, but never got around to making a stompbox for it. Would rather go with a mini amp like you are. Really fun effect.

I'd like to hear the end result!

[marcos_s_p]

Thanks Myampgoesto12!

Do you guys think I could then put the speakers in a 90° angle from each other in a V shaped position so I could reduce the size of the stompbox and direct the sound to the hose upwards? Or would that increase any interference between the speakers?

For sure when it's done I'll record it

Thanks!

[Mark Hammer]

The sonic quality of what you end up with will be affected by the physics of the speaker-to-tube-to-mic axis.  The amp has to be powerful enough to result in acceptable/loud-enough output at the mouth end of the tube, such that what the voice mic picks up is more guitar signal than hum or other ambient noise.  Keep in mind, as well, that the tube, and its resonant properties, dictated by its diameter and length, will shape what comes out the mouth end.  Bandwidth and resonant peaks will depend on diameter, and the longer the tube, the more those properties will be imposed on the signal.   I can't point to any R&D to compel the view, but my sense is that "best" talk-box sound (where the resulting tone is determined largely by one's mouth, than by other factors) is attained by using a wider and shorter tube to efficiently conduct the whole guitar signal to the aperture-mouth-mic junction.

All of this has to be qualified by the caveat that precious little bass content will come through the tube, simply because it can't.  First, there is the matter of what sort of speaker cone one needs to produce that content.  Then there is the matter of coupling that speaker to a tube in a manner that doesn't kill the low end.  Then there is the matter of the longer wavelengths of bass content that would require a much wider and longer tube to conduct.  Then there is the matter of what a human mouth can modify.  So, for a many reasons, talk boxes are mostly mids and highs.  If one switches from unaffected to talk-box, the sound will get thin, and quieter, which will require some compensation.

[marcos_s_p]

Thanks Mark for the interesting information!

The matter of the need of a certain compensation and being most highs and mids, if I'm not mistaken is always the case, isn't it? Because those are always built with small speakers that are not properly for bass and in a not so acoustic enclosure, right?
But I guess that, at least for compensation, I shouldn't worry so much as it is for home and recording purposes, not live.

In any cases it's good to know about the hose as well. Smaller and wider the better.

However, what about putting the 2 speakers as I said in a V (90° from each other)? Would that be bad? Besides which is a good material to fix those on to get the best sound? To not loose frequencies and volume...

Thanks again!!!

[Myampgoesto12]

You could use sheet metal to make adjustable mounts to set it to taste if ya wanted. Given the speakers are relatively flat coned I think it matters less than with sharper cones.

[marcos_s_p]

True, but metal sheets wouldn't´t be the best acoustic option, right? Also, as this is not a horn driver, I need to adapt a cone of some sort to condense the sound to the hose. Metal would be a bit difficult to do all that and also to drill big holes for the speakers. Any other ideas?

Also, anyone have any insight about putting the speakers in a V shape as mentioned?

Thanks all again!!

[Myampgoesto12]

I've seen adjustable holesaws at big box hardware stores before, may be more cost effective than buying an entire kit just for the right size for your speakers, but havent looked for them recently.

I can see using a light gauge metal being sort of bright, maybe 16 or 14 gauge wouldn't be bad. As mentioned before talk boxes already have that mid and high range sorta tone. Instead of dedicating to one shape for the speakers you could also make space (at least for now) in an enclosure and make jigs out of any material with different angles to try.

As for a cone to blend the speakers into one tube, I think that'll have to be trial and error. I'd go for some kind of flexible plastic/runber liner sheet big enough to shape to a cone. Heck you could just fit the speakers into a tapered top box and stick the tube in the peak of the taper and see how it sounds hah.

Edit: Now that I've woke up abnormally early on this day, I've decided I'm going to try something like this hah. Ive got a really small preactice amp i may try and rehouse. Keep us updated, ancious to hear your results.

[marcos_s_p]

Hey guys,

Just to let you know that I´m still trying to find a housing solution to use the two speakers, but I couldn't´t do much the last weeks because I´ve been busy at work .

Anyways, if someone has any ideas would still be much appreciated.

Thanks!

[blackieNYC]

is a kitchen funnel of any help here?  If a small speaker is being used instead of a midrange horn.
I would think that for a talk box to work well, the audio coming thru the tube has to be at least as loud as your voice. Right?

[marcos_s_p]

is a kitchen funnel of any help here?  If a small speaker is being used instead of a midrange horn.
I would think that for a talk box to work well, the audio coming thru the tube has to be at least as loud as your voice. Right?

It would, but I'm adapting a mini amp with 2 speakers for the purpose. So the funnel won't do the trick. I need a way to channel the sound from both. My idea is to put them in an angle so I can concentrate most of the sound to an exit point where the tube will come off... But I'm still trying figure that out...

Sent from my LG-H831 using Tapatalk

[PRR]

These are "small" speakers, right? Like 3-inch (75mm)? And probably flat shallow cones?

Then you want the *smallest* speaker chamber possible. A large volume on the end of a pipe is a resonator, a "jug". All we can do is make the jug as small as possible to shift the resonance as high as possible.

"Angling" works when projecting into open air. But here we need to concentrate on a small exit. Does not work the same. But if the space is very small, the sound WILL "squish" into the exit.

You get into "problems" when the cone diameter is similar to a wavelength. For a 3" cone, at/above 4KHz. Possibly higher, because most of the 4KHz comes off the center of the cone, not so much around the rim. "Talk Box" is not a hi-fi application. We do not need (probably do not want!) extended treble.

BTW, "bass" may not be a problem even for small drivers. Working into open air, small air-paddles make weak bass. But here the sound is entirely confined. The bass SPL in the pipe gets MUCH higher than it ever could as a room speaker. At the exit (mouth) there is a bass-loss at a distance, but we close-mike the mouth. The mouth will form various 100Hz-1KHz resonances, unpredictable, but this IS what we want (singer controlled vocal resonances).

Metal sheets are begging for tinny sound. When we make metal horns for PA, we use *heavy* thick metal or smother the outside with a tar/sand coating.

I said to make the big hole slightly inside the speaker gasket. Actually in this case it can be half the size, as long as the cone will not slap the plywood. There is a small acoustic advantage (less empty space) but also more acoustic friction. I don't think it makes any real difference: if a 50mm hole-saw is handier than a 70mm, just use it.

I used to do similar things for pay. While there are many clever ways to couple a large diaphragm to a small horn throat (tube), unless you have elaborate fabrication skills, small and simple is always best.

[marcos_s_p]

Thanks for the replies!

PRR, great information there. That was exactly what I was wondering. So the fact that in this system I have 2 speakers just make everything harder. Because to reduce the space or I would have to make two separate casings for the speakers and inter-connect them in the hose path with a Y shaped adaptor or I would have to put them flat in one casing, but in this case the hole would be in the center of the casing that would end up being in between the speakers. In that last option it looks to me that I'll loose quality, no?

Maybe it will be easier to arrange a 8Ohm compression driver and wire it up in the small amp (getting rid of the speakers), no? The problem there is that it starts becoming a bit expensive....

[Tony Forestiere]

Test with a 2"x4". Drill a hole through the 4" (3 1/2") side to mount the speakers face to face against the slab. A half inch hole should do. More testing to come.

These are "small" speakers, right? Like 3-inch (75mm)? And probably flat shallow cones?
Then you want the *smallest* speaker chamber possible. A large volume on the end of a pipe is a resonator, a "jug". All we can do is make the jug as small as possible to shift the resonance as high as possible.

Drill from the end of the wood to the newly created "sound chamber" hole with a bit sized appropriately for your mouth tube OD. Clamp on the speakers, test, and open the chamber to taste.

Best of luck in whatever you try.

[marcos_s_p]

Hmm, maybe it's a solution. However putting them facing one another could create another problem. I mean, wouldn't by doing that I create a negative interference and just loose sound because of that?

Thanks for the ideas!

[Rob Strand]

However putting them facing one another could create another problem. I mean, wouldn't by doing that I create a negative interference and just loose sound because of that?

The two signals are in phase it should be OK.  Maybe even better than putting a box in front of it as you can get the volume down.

You shouldn't be too fussy,  sending an acoustic wave down a tube isn't exactly free of issues anyway.

[hiflyerint]

What you really want to use is an in-efficient compression driver. Back in the day when I worked at Electro-Voice I made a talk box with an EV 1824S horn driver. I believe it's the same one Joe Walsh used years ago. Anyway, it worked really well.

[marcos_s_p]

The two signals are in phase it should be OK

Then it's actually going to be a better solution.I can take a plywood (like a baffle) cut a hole in the middle and put one speaker in one side and another in the other facing each other. Then make a hole in the edge of the plywood where I can add the tube. With all that I should economise in space. I guess the suggestion was something like that, no?

in-efficient compression driver

Why do you say inefficient? If I find a cheap compression driver like that I'll use, but here in quebec it is being hard to find.

Anyways, If I try the speakers and they don't work, I can always change for the compression driver. In this solution the enclosure could likely be the same.

Thanks