Desktop beeper (aka internal speaker) with polarity?

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stf92

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Aug 26, 2011
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Hi: Desktop computers have two pins on the motherboard (mb) which go through a cable to a speaker (drive in audio terms). Mine is a miserable transducer which has the polarity marked on it. So I take it this mb output is not, as it was in the old days, for connecting a moving coil speaker, i.e., the kind of speaker there used to be on old mb. Because the latter has no polarity. You can reverse the polarity and it will work.

Are all modern desktops like this one, that is, the speaker output has a polarity which you must respect? The question is rather vague, because maybe high-end desktops have speakers in the old fashion (no polarity). So this datum: the mb is the Gigabyte H61M-S1. May be I am wrong and the transducer has no polarity? My opinion: the plus sign marked on it is a mere decoration.
 
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stf92

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Then the signal driving the piezo-electric speaker has DC component = 0?
 
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stf92

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Let's start from scratch. It's the amplifier output signal which I care about and not the transducer. Either it is a square wave or a sinosoidal wave. If square, the voltage can be low or high, let's call them V_l and V_h. If sinosoidal then it is E(t)= A + B sin wt. What are V_l and V_h in the first case, or A and B in the second one?
 
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GhislainG

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I presume that you are referring to this device that can be mounted on the motherboard or connected as a speaker: http://i.ebayimg.com/t/Motherboard-speaker-buzzer-Computer-/00/$(KGrHqIOKioE14OK1g,oBNtJQGM5bw~~_35.JPG I've used that type of device instead of a 0.25W speaker and it works, but the motherboards alreday had speaker pins. I wouldn't expect the one already installed on your motherboard to be very different; therefore it most likely can be replaced by a speaker. Why would you want to do that?
 
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stf92

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Both but, to be honest, the practical side of it is getting me upset. I'm used to old desktop computers. Namely, the IMB PC. It had a driver (the transducer) in comparison with which present day internal beepers are a joke. I can hardly hear the feeble sound the beeper of my newly bought desktop makes (it's a piezo-electric driver). I thought then "I'll see if replacing it by a moving coil driver I get more response". But people in linuxquestions.org told me the polarity could not be inverted. Therefor, the output must have a non-zero DC component, and this could damage a moving coil driver. Anyways, with an 8-ohm load connected, the output power would be too low, I thought but, anyways, I decided to test. But I repeat, first I had to make sure I would not damage either the driver or the motherboard.

The problem however seems to have been solved. In the site I mentioned, they toldme I can buy speakers that have the amplifier inside. They are worth 10 pounds sterling in supermarkets and I would feed it to the output pins on the motherboard. So, I would have my bell character (ASCII character 0x07) in the desktop console. And much else, for frequency and duration can be varied.

There is an unsolved problem, however. That of fitting the cable to the connector and where to find a shop that sells those connectors. But tomorrow I'll go to a computer repairing shop and will ask the employee to do this work for me. Sure enough, he has
these connectors and the tool to assemble them with the cable. Any way, there can always exist a better solution. This one, has a defect. The speaker would be outside the computer chassis. I translate the computer frequently, so... on second thought I do not feel is so good.
 
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stf92

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I presume that you are referring to this device that can be mounted on the motherboard or connected as a speaker: http://i.ebayimg.com/t/Motherboard [...] w~~_35.JPG I've used that type of device instead of a 0.25W speaker and it works, but the motherboards alreday had speaker pins. I wouldn't expect the one already installed on your motherboard to be very different; therefore it most likely can be replaced by a speaker. Why would you want to do that?

It's exactly the same. My motherboard too has speaker pins. "To have a really audible bell character (ASCII character 0x07) in the console" is the answer to your question. However, do you thing that amplifier, the ampli built in the motherboard, could drive the 8-ohm impedance of a moving coil speaker (those for PCs were 8-ohm). The thing is that I have a very pretty PC speaker (speaker = driver = transducer) with a heavy magnet.
 
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stf92

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I now stand on dry land. The motherboard output will be able to drive my old speaker in a way that it'll be more loud than the piezo-electric. My oldspeaker is 0.25W too and, if the
amp is design to drive such a load (but in the latest launched machines too?), then I'm a happy man.

As to your question, it all depends on the powered speaker size. Within my machine there is plenty of space. 41 x 41 x 17cm. and a tiny motherboard (Gigabyte H61M-S1, actually the chipset). If space is not a problem, then I'm only facing two remaining problems:

(a) Where to buy it. This is not the U.S. (Buenos Aires)
(b) How to fix it to the PC chassis.

Considering all things, the electrical problem I now see, thanks to this forum, does not exist. And that is the more important. Thank you, GhislainG.

EDIT: I beg your pardon, GhislainG. I'm contradicting myself. I'm sleepy. Tomorrow I'll send another post when I have a clear head.
 
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