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Author Topic: Speaker testing time...  (Read 561 times)

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Offline profezzorn

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Speaker testing time...
« on: February 18, 2018, 03:05:15 PM »

Offline Sincenatic

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Re: Speaker testing time...
« Reply #1 on: October 30, 2018, 11:40:00 AM »
I saw this post a long time ago, but I actually never answered, which I should have had. These kinds of tests are very valuable and it should be acknowledged! Thanks for posting!

Very recently I started to search for mini speakers and now I found some specifications that I never had seen in the past. I don’t know if I didn’t search well enough before, or if these are just reaching the market. For example, there are round speakers of about 30mm with 6 or 8 Ohm and 20W.  I don’t know the quality of these, but it would certainly be interesting to try. My question is; what is the voltage output from the teensy directed to the speaker? I suppose that a speaker with a high Wattage rating is still restricted by the voltage that doesn’t allow the speaker to use its full potential. I found a forum with a discussion about this issue using Ohm’s law, and if I understood it correctly, I can keep the voltage and resistance constant and calculate the power.

Ex Ohm   W   V   Amp
1   4   6,25   5,0   1,25
2   6   4,17   5,0   0,83
3   8   3,13   5,0   0,63
4   4   3,42   3,7   0,93
5   6   2,28   3,7   0,62
6   8   1,71   3,7   0,46
7   4   13,69   7,4   1,85
8   6   9,13   7,4   1,23
9   8   6,85   7,4   0,93

Now, to be fair, the actual impendence will vary, but the calculation is just to get an idea. Another question is if a speaker rated to 20W will still sounds better than 3W speaker. In the video, the last speaker is clearly the "winner", but maybe the key advantage is the large box that holds the speaker. I added the last three lines to see how a 2*3,7V option would work. Please correct my if I have misunderstood something.

Offline Sincenatic

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Re: Speaker testing time...
« Reply #2 on: October 30, 2018, 02:59:51 PM »
I have been reading a little more, and it turns out that the speakers that I had found are "tweeters", which are responsible for high-frequency sound. Usually a cross-over is used to direct bass to a “woofer” to protect the “tweeter”. Tweeters cannot play low-frequency sounds. That kind of rules out the illusion that I had... :cheesy: At least I have learnt something new today!

Offline profezzorn

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Re: Speaker testing time...
« Reply #3 on: October 31, 2018, 10:37:36 AM »
I have been reading a little more, and it turns out that the speakers that I had found are "tweeters", which are responsible for high-frequency sound. Usually a cross-over is used to direct bass to a “woofer” to protect the “tweeter”. Tweeters cannot play low-frequency sounds. That kind of rules out the illusion that I had... :cheesy: At least I have learnt something new today!

It's not that tweeters cannot play low frequency sounds, they are just extremely inefficient at doing it. Any speaker with a small membrane is going to be bad at low frequencies. Every kid knows that you can't start a large wave in the bathtub with your hands, but it's no problem if you use your whole body.  Speakers have the same problem, and the scale is actually fairly similar. Low sound frequences have wavelengths in the meter range, and ideally the speaker diameter should be in the meter range too.... :)

Offline Sincenatic

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Re: Speaker testing time...
« Reply #4 on: November 01, 2018, 08:12:12 AM »
I have found a round 1”, 4Ohm, 5W speaker and another 30mm, 8Ohm, 5W and both are full range. These are not labelled as Tweeters. The speakers that I found before are also “full range”, but labelled Tweeter. I already have two 28mm, 4Ohm, 3W speakers at home, but as louder (and brighter) in general is better in our world...I might try 5W. I have just ordered two ProffieBoards, so I wonder if it is 5V that goes to the speakers, or is it 3.7V?

Offline profezzorn

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Re: Speaker testing time...
« Reply #5 on: November 09, 2018, 12:42:25 PM »
I have found a round 1”, 4Ohm, 5W speaker and another 30mm, 8Ohm, 5W and both are full range. These are not labelled as Tweeters. The speakers that I found before are also “full range”, but labelled Tweeter. I already have two 28mm, 4Ohm, 3W speakers at home, but as louder (and brighter) in general is better in our world...I might try 5W. I have just ordered two ProffieBoards, so I wonder if it is 5V that goes to the speakers, or is it 3.7V?

Proffieboards (and TeensySabers) feed about 5.1 volts to the amplifier, which then feeds it to the speaker. The amplifier uses high frequency PWM, which can induce even higher voltages into the speaker coil temporarily.


Offline Sincenatic

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Re: Speaker testing time...
« Reply #6 on: November 12, 2018, 07:33:33 AM »
Great! I will try a 30mm speaker (8Ohm, 5W). Thanks for the reply.

Offline profezzorn

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Re: Speaker testing time...
« Reply #7 on: November 12, 2018, 08:02:32 PM »
Great! I will try a 30mm speaker (8Ohm, 5W). Thanks for the reply.

A 4 ohm speaker will be louder.

Offline Sincenatic

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Re: Speaker testing time...
« Reply #8 on: November 13, 2018, 08:36:36 AM »
I want to be on the safe side, since the specified Ohm-rating is nominal and it actually varies. A very high bass sound can reduce the impedance substantially, which can make distortions if sufficient current cannot be provided. Even with 5V, 4Ohm, we have 6.5W and 1.25Amp, and a temporary drop to 2Ohm would produce a lot of extra heat. I will (finally) try neopixels, so I prefer to not add too much pressure on the battery.