PC speaker louder in PC/XT machines than AT?

[musicforlife]

I have noticed that the pc speaker is clearly louder in my IBM 5150 than in my 286 although both uses same size speakers. Why is that? Is there a difference in speaker itself or is it "hotter signal" from the motherboard? More interestingly I received Hyundai Super-16T which is XT compatible machine and it's got similarly loud speaker as in IBM.

 

[Chuck(G)]

Reallly, you could have answered this one for yourself by checking the logic diagrams. Both speakers are driven by 75477 peripheral drivers, but the XT uses a 33 ohm resistor in series with the speaker, where the 5170 uses a 100 ohm resistor. Doubtless you could make the 5170 just as loud, or the 5160 just as soft, by changing this value.

 

[musicforlife]

Reallly, you could have answered this one for yourself by checking the logic diagrams. Both speakers are driven by 75477 peripheral drivers, but the XT uses a 33 ohm resistor in series with the speaker, where the 5170 uses a 100 ohm resistor. Doubtless you could make the 5170 just as loud, or the 5160 just as soft, by changing this value.

Sorry, I am not an engineer and can't read diagrams. But I know what ohms are doing. Thanks for letting me know this.

 

[A-ko]

I will forever wonder why the PC, XT and most clones dont have a volume control for the speaker. I dont think adding a potentiometer over a resistor would have added that much cost to an already extremely expensive system...I understand the original intent was for business use, but still, I'd picture most workplaces would have liked the option to tone down beeps in certain programs. Then again, the Apple ][ didnt have a built-in volume control either.

 

[romanon]

No way, IBM AT has loudest PC speaker ever....Maybe bigger case offer larger acoustics...

 

[Chuck(G)]

I suspect that the perceived volume has a lot to do with the frequency being "beeped". A good resonant cavity will make things sound much louder.

 

[VileR]

I suppose that the ultimate in 'emulator accuracy' would be for someone to record the impulse responses of different PC cases, feed them into a convolution reverb VST plugin and use that to simulate the perceived characteristics of the sound.

 

[SpidersWeb]

I will forever wonder why the PC, XT and most clones dont have a volume control for the speaker. I dont think adding a potentiometer over a resistor would have added that much cost to an already extremely expensive system...I understand the original intent was for business use, but still, I'd picture most workplaces would have liked the option to tone down beeps in certain programs. Then again, the Apple ][ didnt have a built-in volume control either.

I think the idea is that you wouldn't hear it very often.

It's only with games or music would it be an issue, and that wasn't the 1984 AT's target market.
However my 1984 IBM PC JX has a volume control on the monitor though, and 3 voice sound.

 

[Flamin Joe]

I think the idea is that you wouldn't hear it very often.

It's only with games or music would it be an issue, and that wasn't the 1984 AT's target market.

Yes I think that's pretty much it in a nutshell. Why go to the extra expense of providing volume control for the PC speaker when it's not something the average user would require.

It's interesting though that the original Sound Blaster's provided this functionality by the way of a pass through connector on the board so you could hear (and adjust) the sound level of the PC speaker through the sound card for those older games which didn't have sound card support. So there was at least some thinking that it would be a good idea but then again as pointed out it's because it is an issue when it comes to games and music which is the sound cards intended market.

Sort off on topic, in one of my Atari PC3's the previous owner did a mod where they drilled a neat hole in the side of the case directly where the speaker header was on the motherboard and fitted in their own speaker jack. The motherboard was faulty and I never got around to trying it out with another board so I don't know how well it worked but it was a quite impressive looking mod which almost looked like it came like that out of the factory.

 

[Chuck(G)]

I can't recall ever running into anyone who wanted an amplifier for the PC speaker...

 

[Trixter]

The ;-) makes me think you're referring to an inside joke, but I'm not getting it. What am I missing?

I worked with a lot of bit-banged PWM stuff in the 1980s, which is very quiet in a PC/speaker implementation, so I tapped the speaker line and routed it to my boom box to make it louder. (And also so I could make it quieter to not wake anyone up late at night)

 

[Chuck(G)]

Only that, in office environments, many found the speaker beep to be annoying. Even more so, if a program got hung up and turned the speaker on continuously. I think it's a good trend that speaker volumes and sizes for the simple square-wave output have decreased steadily.

I had a system set up with XP that would periodically beep while I was typing. No error messages; nothing in the system log--irritating as hell. In desperation, I reloaded XP and the appropriate drivers and the problem vanished.

 

[Casey]

I will forever wonder why the PC, XT and most clones dont have a volume control for the speaker. I dont think adding a potentiometer over a resistor would have added that much cost to an already extremely expensive system...I understand the original intent was for business use, but still, I'd picture most workplaces would have liked the option to tone down beeps in certain programs. Then again, the Apple ][ didnt have a built-in volume control either.

Economies of scale. Even if it only costs 25 cents to add it, that's $25,000 extra for 100,000 units. Leave it off, and you've generated another $25,000 revenue. Even a cheap item at 25 cents can make a big difference in your bottom line.

 

[musicforlife]

Reallly, you could have answered this one for yourself by checking the logic diagrams. Both speakers are driven by 75477 peripheral drivers, but the XT uses a 33 ohm resistor in series with the speaker, where the 5170 uses a 100 ohm resistor. Doubtless you could make the 5170 just as loud, or the 5160 just as soft, by changing this value.

Could you do me a photo of showing the location of the component so I could change it?

 

[Chuck(G)]

Which system do you want to change?

The easiest way is to look for the 75477 IC and then the appropriate resistor (depending on PC model). Double check by testing continuity between one leg of the resistor and the speaker jack pin. 33 ohm = orange, orange, black, 100 ohm = brown, black, brown (gold or silver stripes are tolerance specifiers and can be ignored for this purpose).