Anyone have an SE speaker?

[9646gt]

I recapped my SE and there is no sound. Unsure if it ever worked before I bought it. The old PSU blew some capacitors pretty bad so it may have destroyed the speaker.

With a multimeter I get no resistance at all directly on the speaker terminals so it seems dead and the audio out jack is perfect. But I'm not finding a replacement online.

Does anyone have an extra they can spare or sell at a decent price? Shipping would be to Tennessee.

 

[ymk]

Transparent Nickel Plated Speaker for Macintosh SE & SE/30

If you bought one of our clear cases for your Mac SE & SE/30 you'll definitely want this speaker to really make your Mac stand out! This speaker is a functional replacement that also has nickel plating and custom transparent speaker cone.

maceffects.com

 

[9646gt]

Nice. May have to go that route. Thank you.

 

[finkmac]

I remember reading somewhere that the clear speaker linked had lower output power compared to the original speaker.

 

[halkyardo]

Actually, that's a good question; does anyone know what the correct impedance for an SE/SE30 speaker is? I bought a cheap 32 ohm speaker to use when I run my boards outside of a case, and while it does work, it's definitely quieter than the original.

 

[finkmac]

I believe the speakers say "63Ω 0.25watt".

 

[davewongillies]

I purchased one of these speakers for my Mac Classic II recently which also usually has a 63Ω 0.25watt speaker.

The speaker from Maceffects is rated 8Ω 0.25watts and I found the output volume more than loud enough.

 

[ymk]

Actually, that's a good question; does anyone know what the correct impedance for an SE/SE30 speaker is? I bought a cheap 32 ohm speaker to use when I run my boards outside of a case, and while it does work, it's definitely quieter than the original.

Any speaker will be quieter outside of an enclosure.

The clear 8Ω speaker is plenty loud, possibly louder than stock due to the reduced impedance.

 

[Phipli]

The speaker from Maceffects is rated 8Ω 0.25watts and I found the output volume more than loud enough.

8Ω in place of 63Ω!?

I hope they have an inline resistor or that will be trying to draw almost eight times the current from the sound circuit! Also, if the SE does actually output 0.25W at 63Ω, it will be trying to output 2W at 8Ω and be overdriving the speaker too.

Folks, when replacing speakers, a higher impedance is safe (but quieter), while a lower impedance works the sound output circuit proportionally harder. 8Ω is not good to replace 63. If you have no choice, put a resistor in line with the lower impedance speaker to make up the difference (i.e. a 32Ω resistor with a 32Ω speaker to bring it back to 63Ω). The resistor will make the volume lower, but protect the sound circuit.

With 8Ω being so low compared to 63Ω, you would probably need a small audio transformer to step down the voltage 8x.

It's worth trying to get a like for like replacement.

 

[ymk]

8Ω in place of 63Ω!?

I've used the @maceffects speaker for a long time and will confirm that it has caused no damage my SE.

 

[Phipli]

I've used the @maceffects speaker for a long time and will confirm that it has caused no damage my SE.

I wouldn't be content with that personally - I'd be upset if some software set it to full volume and burnt out the sound eventually.

A speaker with 1/8th the impedance will draw 8x the current in the same situation. If you have it set to the same volume.

Either you're putting more load on the circuit, are only using lower volume settings or perhaps the speakers are modified before delivery?

@maceffects - what's the situation with the speakers? Have you been adding a resistor to them to reign them in?

 

[Phipli]

Right, there is inline resistance on the Mac itself, which lessens the impact. The Plus and older seem to have 74ohm inline, which would make using 8ohm instead of 63ohm about a 67% increase in current, which is better than 800%, but you would be still be potentially putting 0.42 watts through a circuit designed for 0.25W.

I should find the SE scematic.

 

[Phipli]

SE/30 looks to only have 27ohm in line with the speaker, so an 8ohm speaker would result in a ~260% increase in current?

 

[davewongillies]

It's worth trying to get a like for like replacement.

I only ended up with the MacEffects speaker because besides ripping one out of an old Mac 0.25@/63Ω speakers don't seem to exist anymore (searching for it just yields a bunch of forum posts of people asking where to find 0.25@/63Ω speakers). Also I bought the MacEffects speaker because I assumed it would be the same or close to what was in an SE or similar machine (they don't list the specs of the speaker on their site).

 

[maceffects]

I've sold over 100 of these speakers with zero complaints other than folks commenting of the Ohm (8 vs 63) difference. JDW discusses this in his video at the time sampled link

Extensive testing has been performed to ensure it will work and not hurt the Mac.

 

[cheesestraws]

I've sold over 100 of these speakers with zero complaints other than folks commenting of the Ohm (8 vs 63) difference. JDW discusses this in his video at the time sampled link

Extensive testing has been performed to ensure it will work and not hurt the Mac.

I'm not sure if this reply is marketing or condescension? I'd prefer a better argument than "it hasn't broken yet" and a far better engineering authority than jdw

 

[Phipli]

I've sold over 100 of these speakers with zero complaints other than folks commenting of the Ohm (8 vs 63) difference. JDW discusses this in his video at the time sampled link

Extensive testing has been performed to ensure it will work and not hurt the Mac.

I'm more of a fan of parts being specific for their jobs.

This isn't my specialism, but... The SE/30 sound circuit uses a 2N3904 to drive the +ve and a 2N3906 for the -ve.

The 2N3904 and 2N3906 both look to be nominally rated for 625mW



That's a total of... 1.250W total.

On the SE/30, using an 8ohm speaker instead of 63 gives a 260% increase. If the 0.25W marking on the original speaker matches the output, then you're now at a max of 0.65W which is << than 1.25W...

But... Exceeds the 0.25W of the new 8ohm speaker.

If I've understood correctly, the drivers look like they can handle it, the speaker's rating is likely being exceeded and I haven't checked the PSU.

YOLO-ing component specs and picking a part 8 times different in value isn't great. There are ways of matching impedence and also any impedence higher than 8 would have been better.

 

[cheesestraws]

A youtuber says it's fine phil we should all sit down and know our places

 

[ymk]

I'd prefer a better argument than "it hasn't broken yet"

I ran some simulations with 63Ω, 8Ω and a dead short. The highest peak to peak voltage I recorded from an unloaded SE/30 speaker header was 6.8V, so I simulated with a sine wave with the same peaks.

63Ω speaker: 21.8mW
R10: 9.4mW
Q1/Q2: 54.1mW

8Ω speaker: 17.7mW
R10: 59.8mW
Q1/Q2: 170.0mW

Dead short
R10: 99.8mW
Q1/Q2: 226.2mW

While the 8Ω speaker is loud, you get a bit less power from it than the 63Ω. The bulk of the power ends up in R10.

8Ω is safe, but less efficient.

Even with a dead short, the output transistors run well within spec.

 

[cheesestraws]

Thanks!