Dual Speakers

Question: is it possible to drive two speakers in parallel? If they are 8 ohms, the apparent resistance to the proffieboard would be 4 ohms.

Or, could you run two 4 ohm speakers in series?

I say yes to both.

I agree with @NoSloppy.
I have also done this myself, running 2 28mm speakers in series.
it did yield some interesting results too.

my setup was with a traditional speaker facing away from the hilt while the second was facing towards the hilt. each with its own chamber behind the speaker driver. (this helps to stop reflected sounds messing with each speaker)
I found in my setup that i had issues with the sound not being able to escape from the hilt from the second speaker.
unless you have adequate sound holes for this too happen.
the sound I was getting from the second speaker because of this chamber being mostly closed (as it was facing the chassis) was that you will loose a significant amount of the higher frequencies as they will become trapped and reflected inside this chamber. (unless this is your intention)
or it could go completely the other way with all the bass missing and a very tinny sound being produced.
i found that messing around with the sound holes and possitioning of these holes that you can tune the sound emitted from them.
also the chamber size in front of this speaker will make a big difference too.
it could take you some time to design the right chamber size with the right size and shape sound holes for a more balanced sound to come from this.

also just to note that the speakers will not be driven as much by the amplifier (as with a single speaker) as both speakers will now share the audio signal thus resulting in both speakers being slightly quieter.

for these reasons I decided not to pursue it further, but if you come up with something please post it as I would be very interested in seeing how you did and how it sounds.

please also note that my replay is solely based on my own experiences and is by no means gospel. (it’s great that other want to dabble as i most likely missed a trick or something)

I am though having a look at making a passive radiator design (just waiting for bits to arrive) to see if bass can be improved with a more traditional single speaker setup.

here you can see one of my mock ups with a dual speaker setup.
as you can see there is a space between the second speaker and the chassis.
this forms a chamber in front of the second speaker and will tune the sound you get.
the sound holes will also tune what you will hear from this chamber.
the smaller the holes and further away from the speaker will give more bass and filter the highs.
the larger the chamber again more bass but less highs.
and the same in reverse.
https://www.dropbox.com/s/hnxk0p691naiuu8/Screenshot%20%28157%29.png?dl=0

Did you phase flip one of those back to back speakers? If that’s a sealed space between them, that would be ideal as they would both move the same direction, as opposed to both squeezing in and then pulling apart. That could wreak havoc on your sound.

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yes I experimented with both in phase and opposed phase.
I have to admit that it did not seem to change anything as I was expecting.
I also ran the experiment with the speakers sharing the same chamber behind the speakers and had the phases opposed so resulting in a push pull set up. (as you would find in a high grade audio system used for high output in a small package)
again it seemed more apparent that tuning the chamber in front of the second speaker made more of a difference to the sound than any other variable.
i’m thinking that this could be down to the small size for the speaker contributing to this as we are not moving enough air to make any changes apparent.
this is why im looking into passive radiator designs.

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Thanks for all the info!

Actually I was thinking about mounting one speaker directly below the blade connector, and venting out just below the emitter section. The second speaker would be mounted traditionally at the pommel. One of my biggest gripes with current sabers is the sound coming from the pommel…to me it would be more realistic to have the sound exit near the emitter, as it is the blade’s interaction with the air that primarily makes the lighsaber “noises”.

The only big issue is accidentally covering up the sound vents with your hand and muffling the sound, but I’ve been thinking about machining slots in the emitter, covering them with stainless mesh, and then putting a shroud over the mesh to hold it in place. That would greatly increase the exit aperture and reduce muffling.

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I had exactly this same idea but with only a single speaker.
When I get home ill pop up my draught of it for you to look at.
Running the wires to the blade connector is a bit tricky though.

this was my take on a speaker relocated into the front portion of the hilt.
in theory it should project the sound more towards the user… or at least that was my intention.
https://www.dropbox.com/s/w3zynu5omrgjee2/Screenshot%20%28159%29.png?dl=0

Interesting. Any reason you decided to mount the speaker facing down rather than up towards the blade? Seems like mounting it facing up would make it easier to wire at least.

I drafted a design last year…will post some screenshots once I have a minute.

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It was mk1 and yes I had that same thought.
I initially thought that the sound would project better toward the user this way as you tend to hold a saber in front of you and pointing away so the speaker facing this was would direct sound towards you.
In theory…
I was going to change it to face forwards and see how it changed things.

Ah, okay, that makes sense.

Here is the design that I worked on for a while:

There are slots milled in the emitter that intersect with the speaker chamber. A shroud is installed over the emitter that directs the sound up and into the radial grooves and out next to the blade. I may make a variation of this on the Titanium saber I am designing.

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now that’s cool!
it does beg the question of; “I wonder how it would sound?” :thinking:
maybe using a smaller 20 - 24mm speaker here and a larger 28+mm in the pommel?
kind of like you suggested in your original posts.
Titanium?!
super strong and super light!
i like it! :+1:

If I have room I’d like to do dual speakers!

Yes, I’ve always wanted to machine a titanium lightsaber. It just feels right to make such a powerful and elegant weapon out of super strong space-age metal.

It’s going to be a huge pain to make though. You cannot buy titanium tubing with thick walls like you can with aluminum. I’m going to have to start with straight up bar stock, drill, and ream to size. Not to mention titanium is hard to machine to begin with. Plus the chips can catch on fire. :upside_down_face:

Still, the strength of the material means you can get away with some really thin walls and still be okay. It also takes fine threads really well. And it’s just straight up cool!

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i wish you good fortune on your journey!
post it up when you get going… so cool :sunglasses:

did some further research with running speakers in parallel and what it does to the amp.

running both speakers (4ohm + 4ohm = 8ohm) effectively half’s the total (watt) output from the amplifier. meaning that if we have a 3watt amp, running a duel speaker set up we only get 1.5watts of total power output.
so in turn we only get half the power going to each speaker so volume is reduced.

it could be summarised that each speaker uses half the available power so added together will give us roughly what we would get from a single speaker.

there are two advantages from running a duel speaker set up though.
firstly the amplifier will be less stressed due to not needing as much current to drive the speakers.
secondly each speaker could be mounted at different points in the hilt giving a bi-directional sound.

i have run some basic tests with this and can confirm that the volume was reduced from both speakers.

Half the current means you get half the watts, which means half as much audio.
If you had one 4-ohm speaker and one 4-ohm resistor, you would get one quarter of the audio. Since audio perception is exponential, it’s not easy to hear the difference.

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That being said, could you wire the 4-Ohm speakers is parallel?

The amp can handle 2.8A. So at 4.2V, the maximum current with a 2-ohm speaker set would be 2.1A.

Then again, the wattage would be 8.4W…which I assume is too much for the 3.2W amp?

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The voltage to the amplifier is 5 volts, not 4.2. Also, the calculations you are making would only apply to a square wave. A sine wave has half as much power, which is what is normally used for speaker and amplifier power calculations.

Thus, a 4-ohm speaker will produce 5V * 5V / 4 \Omega / 2 = 3.125 W
Two 4-ohm speakers in parallel would produce 5V * 5V / 2 \Omega / 2 = 6.25 W ,

I’m not entirely sure how to calculate the current through the amplifier/speaker though, as the amplifier generates a 10-volt peak-to-peak PWM at ~300kHz. The speaker coil takes care of smoothing it out, but I’m not sure what that means for the current.

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Would the amplifier chip be able to run this sort of power consistently or is it something that is not advertised.