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Beginner wants help retrofitting old PC speakers
Beginner wants help retrofitting old PC speakers
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Old 6th December 2020, 09:46 PM   #51
planet10 is online now planet10  Canada
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Beginner wants help retrofitting old PC speakers
That 3/10mm might be enuff to get a good seal with the right gasket tape.

The reason i ask is there are probably some variations of these on my give-away shelf

dave
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Old 2nd January 2021, 02:52 AM   #52
ElBjorno is offline ElBjorno  Australia
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So finally finished my speakers. I had to wait for a few bits and pieces that I ordered to arrive, and then christmas got in the way, so it took a bit longer than expected. But I'm pretty happy with the results. They're not perfect, but they definitely have the surprising and unexpectedly high audio quality out of crummy looking beige desktop boxes that I was going for!

Click the image to open in full size.

Click the image to open in full size.

As you'll see, I did replace all the caps in the end. As I said, I had to order a few things anyway, and I just decided to throw the caps in to the order since they're cheap and I could probably do with some practice soldering. Besides, this way I know they're not going to die anytime soon. (And testing the old caps that came out of the board, they mostly seemed to have drifted out of spec)

However I think it's clear that the parts aren't necessarily designed to go together, as the speakers sound a little unbalanced, even to my untrained ear - I have to put the treble way up and the bass way down, and even then it sounds like there's not enough mid-tones. But I think I can make it tolerable with the mixer on my computer.

At first I thought it lacked dynamic range too (the big dramatic hits in the Tron Legacy soundtrack sounded flat), but now I'm thinking that was just because of the crummy Vibra16 soundcard I was using. I do have an AWE64 on the way though, which should mitigate that somewhat. Either way, they sound a damn sight better than they did (even if the right driver hadn't been broken).

So yeah, thanks again to everyone for your tips! I've learned a lot, and ended up with a pretty decent set of speakers for a retro computer!
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Old 2nd January 2021, 10:35 AM   #53
russc is offline russc  England
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Try reversing the leads to one driver.
If they are in opposite phase they will cancel the mids where they overlap.
Easy to try & if it doesn't work to undo.
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Old 2nd January 2021, 04:39 PM   #54
Galu is online now Galu  Scotland
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Thanks for the update. That looks like a quality job!

If you used a 1.5uF capacitor in series with the 8 ohm tweeter, you could experiment with a larger value (up to a maximum of 4.7uF) that will pass a wider band of treble energy.

And for a quick and easy experiment, you could try to tame the over-generous bass by blocking the reflex ports with bath sponge type foam or even an old pair of socks!
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Old 3rd January 2021, 03:50 AM   #55
ElBjorno is offline ElBjorno  Australia
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Thanks! I think it's a reasonable effort for a first time speaker resto. Definitely good enough for their purpose.

After more testing I'm starting to think the problem is almost like an uncanny valley effect - the sound is too good to be one thing, but not quite good enough to be another. I've tried a few different audio samples on different systems, and I'm finding that ideal levels tend to differ a lot.
(In particular I was constantly fiddling with the levels in Star Wars Episode IV every time it switched between music, dialogue and action)
I guess I'm just used to cheap desktop speakers that flatten everything out to an inoffensive beige meh. These just show up every imperfection and imbalance!

I'll see how I go with those other suggestions though (reversing leads, trying a different capacitor for the tweeters, and sticking a sponge in the reflex ports)
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Old 3rd January 2021, 08:38 PM   #56
sgrossklass is offline sgrossklass  Germany
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If you have anything floating around that even remotely behaves like a measurement microphone, that would definitely help. I have even used a fixed-pattern cardioid LDC with a well-extended and balanced response - takes some extra distance to fend off proximity effect but actually worked quite well.

Also, the 1-capacitor "crossover" is very crude and only ever works properly if the bass driver rolls off where you want in a well-behaved manner with well-controlled breakup modes (chances of that are pretty slim), and both drivers' sensitivities sort of match. That generally means adding some inductance in series (when then provides a much-needed 90 phase shift at crossover, complementing the -90 - 180 of the highpass-filtered and phase-reversed tweeter), and probably a series resistor or resistor divider for the tweeter which tends to be the more sensitive of the two. And then that still isn't great as such a 1st order XO has to be fairly high to avoid overloading the tweeter, often running afoul of possible geometric driver spacing.

You can sort of coax a 1-capacitor XO into working by aiming for a rising treble response and then pulling down the treble electronically to compensate. That's what e.g. the JBL 104s do. The problem is, this generally doesn't give nearly enough suppression of breakup modes unless the bass driver is extremely well-behaved, giving distortion peaks and erratic directivity.

By the time you are making the jump from one to two drivers with its obvious benefits in terms of reduced IM distortion and not requiring an expensive one-size-fits-all driver, you are also confronted with a number of new problems to be solved, no way around that.

Given your listening impressions, I'll assume the original drivers are fairly high-fs jobs to get some half-decent efficient out of what I would guess is not the strongest magnet system and narrowest air gap in the world, which is to say they would play decently loud with the little amplifier provided but not have that much bass, and possibly still be bass deficient despite support from the port. The new driver may even be filling in the low end too much, hence the suggestion of plugging the port. Hopefully it also features some half-decent (linear) excursion, as Xlin requirements quadruple per each octave added.
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