Loud Speaker?

[ChrisGreece52]

Hello i got 2  8 watt 14 ohm 2" speakers and i am wondering if i can increase the max volume (like overcklocking the speaker) with any kind of way ....
This may sound crazy but it may be possible i think.
Also could i use both speakers as one (by connecting them in parallel or in series ?)

[c4757p]

Increase the voltage they are driven with, obviously. Just like overclocking a CPU, you risk damaging them by running them above rated power.

As for series/parallel - have you ever wondered why an orchestra isn't dozens of times louder than a trumpet, or why it has so many damn violins? Sound volume adds logarithmically.

[Psi]

If you put the two 14ohm speakers in parallel you lower the total resistance to 7ohms.
The amplifier will then put more power into the speaker for the same position on the volume knob.

But be aware that you're pushing the amplifier harder in order to get more volume out of it.
Depending on the specs of the amplifier you could damage it with low ohm speaker loads.

In reality i doubt you'd damage it with 7 ohms since 8 ohms is very common for speakers.
A typical amplifier might get unstable in the 1-4ohms range for example.

Are you sure your speaker is 14 ohms  8 watts?  The reverse (8 ohms and 14 watts) would seem more likely?

[madires]

Hello i got 2  8 watt 14 ohm 2" speakers and i am wondering if i can increase the max volume (like overcklocking the speaker) with any kind of way ....
This may sound crazy but it may be possible i think.

Overdriving speakers isn't a good idea, because at high power levels the sound becomes really distorted. I wouldn't even max out the specified power.

Also could i use both speakers as one (by connecting them in parallel or in series ?)

Yes, but you have to take care that the amp is able to drive the resulting impedance. BTW, adding up the dB values of both speakers is done by: sq(SPL1² + SPL2²).

[ChrisGreece52]

If you put the two 14ohm speakers in parallel you lower the total resistance to 7ohms.
The amplifier will then put more power into the speaker for the same position on the volume knob.

But be aware that you're pushing the amplifier harder in order to get more volume out of it.
Depending on the specs of the amplifier you could damage it with low ohm speaker loads.

In reality i doubt you'd damage it with 7 ohms since 8 ohms is very common for speakers.
A typical amplifier might get unstable in the 1-4ohms range for example.

Are you sure your speaker is 14 ohms  8 watts?  The reverse (8 ohms and 14 watts) would seem more likely?

Its a low power amp LM386 but i think that i will take the speakers

[ChrisGreece52]

Hello i got 2  8 watt 14 ohm 2" speakers and i am wondering if i can increase the max volume (like overcklocking the speaker) with any kind of way ....
This may sound crazy but it may be possible i think.

Overdriving speakers isn't a good idea, because at high power levels the sound becomes really distorted. I wouldn't even max out the specified power.

Also could i use both speakers as one (by connecting them in parallel or in series ?)

Yes, but you have to take care that the amp is able to drive the resulting impedance. BTW, adding up the dB values of both speakers is done by: sq(SPL1² + SPL2²).

Thanks but i am already getting distortion from the amp alone (i got a 10 uf cap but the version 2 i am going to build a case and things i am going to put switches so i can sellect value of the cap and ill even put a wire (no cap) to get maximun gain)

[madires]

Thanks but i am already getting distortion from the amp alone (i got a 10 uf cap but the version 2 i am going to build a case and things i am going to put switches so i can sellect value of the cap and ill even put a wire (no cap) to get maximun gain)

Let's see. LM386 delivers 700mW at 8 ohms with 9V and a THD of 10%. You won't overdrive the speakers with that :-) But yes. the distortion is awful. I would recommend something like a TDA1519B (2*6W or 12W, roughly 12V). It also got a THD of 10% at maximum power, but if you keep the power below 3W or so you'll have just about 0.1%.

[mariush]

It doesn't matter how big the speakers are if your audio amplifier doesn't have the power to drive them. LM386 is too small.

Make your own amp with TDA2040 or TDA2050 for example, they're mono audio amplifier chips so you need two , one for each channel ...

tda2040: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf
tda2050: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1461.pdf

The datasheets have examples for both split power supply (if you have transformers with center tap or two separate secondary windings)  or for single power supply (if you want for example to power one from a computer power supply or something like that) and they're very easy to make even on breadboard.

tda2040 can work with 5v to 40v but at 12v it can only do about 2-3 watts. At about 30v it can do 10w on 8 ohm, or about 18w on 4 ohm with 0.5% distortion
tda2050 can work with 9v to 50v but at 12v it can only do about 2.5 watts. At about 40v it can do 22w on 8 ohm with 0.5% distortion

Tayda electronics has tda2050 on ebay for 3$ for a pair, and the rest of the components are about 3-4$.

Here's a page showing one ready made on prototyping board, which uses a split power supply, to see how easy it is: http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/

[ChrisGreece52]

Thanks but i am already getting distortion from the amp alone (i got a 10 uf cap but the version 2 i am going to build a case and things i am going to put switches so i can sellect value of the cap and ill even put a wire (no cap) to get maximun gain)

Let's see. LM386 delivers 700mW at 8 ohms with 9V and a THD of 10%. You won't overdrive the speakers with that :-) But yes. the distortion is awful. I would recommend something like a TDA1519B (2*6W or 12W, roughly 12V). It also got a THD of 10% at maximum power, but if you keep the power below 3W or so you'll have just about 0.1%.

Thanks ill probably have to change my amp

[ChrisGreece52]

It doesn't matter how big the speakers are if your audio amplifier doesn't have the power to drive them. LM386 is too small.

Make your own amp with TDA2040 or TDA2050 for example, they're mono audio amplifier chips so you need two , one for each channel ...

tda2040: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1460.pdf
tda2050: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1461.pdf

The datasheets have examples for both split power supply (if you have transformers with center tap or two separate secondary windings)  or for single power supply (if you want for example to power one from a computer power supply or something like that) and they're very easy to make even on breadboard.

tda2040 can work with 5v to 40v but at 12v it can only do about 2-3 watts. At about 30v it can do 10w on 8 ohm, or about 18w on 4 ohm with 0.5% distortion
tda2050 can work with 9v to 50v but at 12v it can only do about 2.5 watts. At about 40v it can do 22w on 8 ohm with 0.5% distortion

Tayda electronics has tda2050 on ebay for 3$ for a pair, and the rest of the components are about 3-4$.

Here's a page showing one ready made on prototyping board, which uses a split power supply, to see how easy it is: http://diyaudioprojects.com/Chip/DIY-TDA2050-Hi-Fi-Chip-Amplifier/

Thank you but there is a thing.
With the LM386 you can use different values of caps for maximun of minimun gain can you do that with the TDA's
And also i think that the TDA chips produce much heat.

[mariush]

Of course you can adjust the gain with those TDA chips, the datasheets explain what each capacitor and resistor in the example circuits do and what increasing or decreasing their values does.

Of course these chips will get warm or hot without a heatsink, they're not 100% efficient, they're class AB amplifier chips, not class D chips (but class D chips are more expensive and can be much more difficult to make on your own, these are super easy to use). Their efficiency is about 65-70%, so if you'll give them 40v and output 20-25w to the speakers, you'll get about 10-15w wasted as heat, so you'll need a large heatsink for them.

But if you power them from 12v and they output 2.5-4 watts, a small heatsink would be enough, something recycled from an old power supply, or even some metal sheet screwed to the back of the chip may be enough.

Your LM386 may not get hot, but that's only because it won't output much power anyway, it's limited to 1.5w or something like that, you only get about 0.7 watts on a speaker... if it doesn't take much power in and doesn't put much power out, what's there to heat?
It's not a powerful audio amplifier and no matter how you put it, it's just not designed for those big speakers. Honestly, I wouldn't use it to power something bigger than headphones.

The point is that it's a very easy project to tackle, it doesn't cost much money, these chips are very generic and you may find them in stores around you (stores that sell parts for tvs and radios, maybe even people repairing tvs have them around if you ask them), they're cheap. The capacitors and resistors are also cheap...You can find everything needed on eBay if you don't find in Greece, it's really not a problem.
It would be a nice simple project for you to make and enjoy.


I have an audio amplifier board taken out of an older Phillips TV (I'm attaching it to this message) that uses TDA2040 and never had to adjust the gain, I found that adjusting the volume in Windows was enough. Nowadays I have a 5.1 system and don't use it anymore. The circuit in the datasheets is much simpler, this one has headphone output and some other additions that I don't use and you wouldn't need anyway.

The heatsink is sized so that the amplifier would output up to 20-25w per channel, the 35w printed on the board is peak, with 10% distortion. tda2040 is designed for about 40v input voltage, the transformer in the picture is +/- 15v and low current.  When I used it with two 10w 4w speakers, the heatsink barely got warm, even at high volume.
 

[ChrisGreece52]

Nevermind i saw the datasheet and the site in depth and i saw that instead of a capacitor the TDA uses a resistor

[ChrisGreece52]

I think i am going with the TDA 2050 because of its output power.
Ill feed a 12 volt DC voltage to it and reffering to the diagram it says that with about 12 volt input voltage the power output is about 10 watts.
Also i will use the same gain configuration that i wanted to used with the LM386
its a double pole single throw switch the one pole is connected to an led (to indicate the status of the gain) and the other pole to the main capacitor (in this case resistor)

[ChrisGreece52]

From the datasheet i got this info.
I will operate it at 12 volts
At this voltage the output power is about 10 watts
the distortion at 20 watts (1 khz) is 0.03%
and at 15khz is 1% (non existant at 10 watt)
also the power dissipation at 10 watt is also 10 watt (i hope i am wrong at this one)

[mariush]

No.

Pay attention to what the graphs say:



The graph is for SPLIT POWER SUPPLY  (a power supply that has negative AND positive voltages feeding the amplifier). 
The voltage values below are listed as +/- VOLTAGE.

In the first picture (on the left), you're not interested in 10% distortion, so you look at the second curve that's a bit lower than the first, which is for 0.5% distortion.

On the Y axis, you have the output power, on the X axis you have the input voltage, in +/-V. If you're going to use a single power supply ( just ground and +v), you have to double that value.

You can see that it crosses the 5w output at +/-10v, so you'd need +20v to get 5w output on the speaker. With 40v (+/-20v) you get about 20w output.
With just 12v, you have to look at +/-6v , so you're somewhere between +/-5 and +/-10v, at about 2-3 watts.  This is still way better than about 0.5-0.7w you get with LM386, with 10% distortion.

Since these have such large input voltage range (up to +/- 25v or 45-50v for single power supply) it makes them great to use with recycled transformers - 24-30v AC transformers are relatively easy to find (but remember it's not just the volts with a transformer, the VA rating must be big enough, let's say about 40-60VA at least, this would make it a heavy transformer, about 0.5 Kg at least).
Until you do find one, you can simply use a 12v from a computer power supply and only get a lower number of watts. 

In the second picture, on the right, you have the Distortion versus output power, WHEN the IC is powered from +/- 22v (so with a single power supply that would be 44v - the IC tolerates a maximum of +/-25v or 50v).  This is close to the IDEAL way the amplifier would like to work, the maximum voltage it supports.
That one says that with 8 ohm speakers, the distortions are typically below 0.1% from 1kHz to 15kHz. 
But the graph is only correct for +/-22v or about 44v. If you power the amplifier from only 12v, the distortions may be a bit higher... but should be below 0.5% as the graph in the first picture say.


Later edit:   The graph there on the left is for  8 ohm speakers. If you use 4 ohm speakers, the output power changes a bit, and you can see that in Figure 8, on the following page in the datasheet.  And notice that with 4 ohm speakers, the amplifier is no longer able to work at up to +/-25v (50v), the graphs stop at about +/-22v (44v)  and on the right side of the page, you see those distortion graphs made for +/-18v (36v) , not for +/-22v like before.

[madires]

If the supply voltage is 12V single rail the TDA1519B (in BTL mode) would give more power at a THD of 0.5% and you won't need the large cap at the output to block DC. There are also some more powerful amps in that family like the TDA1518BQ with 24W in BTL mode (or 2 * 12W in stereo mode). For single rail applications a car stereo amp is mostly the better solution. The TDA20xx is great if you got a dual rail supply like in a standard stereo.

[SeanB]

All I did with mine was to use a TDA2009 on a premade board sold as a replacement for some rather unreliable STK modules in older television sets. Added a big heatsink and it runs nicely on 32V from an old inkjet printer power supply.

[mariush]

madires, the IC is interesting but... if you dig deep in the datasheets you'll notice that it can typically do 10w at 8 ohm with about 14.4v input voltage, in BTL mode.
At 12v, it will pretty much go down to about 7-8w at 8 ohm, again, in BTL mode.  With just one speaker per channel, it will be about 3.5-4w, just a watt or a couple of watts above the tda20xx.

Chris is a beginner at electronics, so he won't easily understand the concept of BTL and doesn't have such nicely made application circuits and examples of pcb and a website showing off a ready made amplifier to get insipiration from, and in addition he only has two speakers right now.  He doesn't have four speakers, to put 2 speakers on each channel (which is needed for btl mode).

In addition, these ICs will only work at up to about 18v, while the TDA2050 works up to 50v - he can compromise now going for tda2050 and get only 2-3 watts on each channel running it from 12v and later when he finds a transformer with bigger output voltage, he'll get more power. With this tda1519, he'll be stuck at up to 18v and 11-12w in btl mode (or about 6w per speaker).

[madires]

In addition, these ICs will only work at up to about 18v, while the TDA2050 works up to 50v - he can compromise now going for tda2050 and get only 2-3 watts on each channel running it from 12v and later when he finds a transformer with bigger output voltage, he'll get more power. With this tda1519, he'll be stuck at up to 18v and 11-12w in btl mode (or about 6w per speaker).

The decision which TDA fits better is based on the power supply. If it's around 12V the TDA151x is the better choice, if its >16V then the TDA20xx wins. No worries! :-)

[ChrisGreece52]

Thank you all but i am confused.... i had not so many time to read in depth all the comments but here are some things that will make you life easier
My supply will be a 12 volt 1 amp ac to dc converter
I only need 1 channel (left or right ) or even both no prob.
I need adjustable gain with caps or resistors
I need it to be loud but no so easily distorted
As for heat dissipation its ok ill use a big ass heatshink or even combine a small heatshink with a fan for maximun cooldown

[madires]

Thank you all but i am confused.... i had not so many time to read in depth all the comments but here are some things that will make you life easier

Welcome to the Amp wars :-)

My supply will be a 12 volt 1 amp ac to dc converter
I only need 1 channel (left or right ) or even both no prob.
I need adjustable gain with caps or resistors
I need it to be loud but no so easily distorted
As for heat dissipation its ok ill use a big ass heatshink or even combine a small heatshink with a fan for maximun cooldown

Then it's the TDA1519B. Since you're got a SMPSU please add an additional power filter (a LC filter for example).

[IanB]

"Adjustable gain" is a "volume control knob". Almost all audio amplifiers need one of these. Typically a logarithmic pot serves this function.

The loudness you get with small amplifiers depends mainly on the sensitivity of the speaker. You don't need that much power necessarily for comfortable listening. Small transistor radios have done fine for years with batteries. You will have to test the speakers you have and see how they perform.

[ChrisGreece52]

"Adjustable gain" is a "volume control knob". Almost all audio amplifiers need one of these. Typically a logarithmic pot serves this function.

The loudness you get with small amplifiers depends mainly on the sensitivity of the speaker. You don't need that much power necessarily for comfortable listening. Small transistor radios have done fine for years with batteries. You will have to test the speakers you have and see how they perform.

I am not reffering to the volume knob (sorry for the missunderstanding)
I am reffering to the cap between pin 1 and 8 adjusting the value of the cap you actually change the gain
http://www.ti.com/lit/ds/symlink/lm386.pdf

[IanB]

I am not reffering to the volume knob (sorry for the missunderstanding)
I am reffering to the cap between pin 1 and 8 adjusting the value of the cap you actually change the gain
http://www.ti.com/lit/ds/symlink/lm386.pdf

OK, I see.

[mariush]

Thank you all but i am confused.... i had not so many time to read in depth all the comments but here are some things that will make you life easier
My supply will be a 12 volt 1 amp ac to dc converter
I only need 1 channel (left or right ) or even both no prob.
I need adjustable gain with caps or resistors
I need it to be loud but no so easily distorted
As for heat dissipation its ok ill use a big ass heatshink or even combine a small heatshink with a fan for maximun cooldown

Ok, Chris, here's a very basic explanation.

Amplifiers output a certain amount of power (in watts) based on the resistance of the speakers ( in your case 8 ohms) and the input voltage they receive (and the current, naturally).  Some audio amplifiers aren't that sensitive to input voltage, others are. 

These amplifier chips that I mentioned (tda2040, tda2050) like bigger voltages a lot, the more voltage the more audio power they can output. With these amplifier chips, as you can see in the graph above, the power output increases quite a lot as you increase the input voltage... with +/-5v (10v with single power supply) you only get 2-3 watts, with +/-22v (44v with single power supply) you get 25-30 audio watts (ten times as much).

Other amplifier chips like the TDA1519 mentioned by madires only works with a smaller range of voltages and is a bit more efficient with lower voltages, but as a downside it can't give you as much power as the previous chips - it tops out at about 5-6 watts while the tda2050 can do about 20-25 watts.

The amplifier chips that can output a lot of power are usually designed to be used with split power supply. That is, you have a transformer with two secondary windings or a single winding with a center tap, and from that you can create a negative voltage and a positive voltage, so they amplifier has two input voltages, like this:



From top to bottom, you have at the output +V , GND and -V
In the picture above, you have a transformer that outputs 48V AC with a center tap - the center tap becomes the ground, and there's a positive 24v AC and a negative 24v AC. These are RMS values, so when converted using a bridge rectifier like in the pictures, you get about 34v.  So that is a +/- 34v split power supply.
The TDA2050 can handle a maximum of +/- 25v  so this transformer is actually too big for it, but it's just an example.

Split power supply is better for audio amplifier chips because it makes it easier for an audio amplifier to create the audio waves that are sent to the speakers.

Single power supply is the power supply like you have on the computer or on ac to dc adapters, where you have just ground and a positive voltage. 
Some amplifier chips can work with just positive voltage but when using such power supply you have to keep in mind that the voltage difference is now half compared to a split power supply.  12v DC  is equivalent to -6 - 0 - +6v split power supply because from -6 to +6 is a potential difference of 12v.
So wherever you look in graphs made for split power supplies, you have to look at the values for half the voltage for your single power supply.

Now, as the amplifier chip no longer has that positive and negative voltage, the output is harder to generate and it's a bit hard to explain but in such configuration a large capacitor is needed in front of the speaker - if you look in the datasheet for TDA2050 you will see the "single power supply" design has a 1000uF capacitor near the speaker while the split power supply doesn't need one. The TDA1519 works around this issue in BTL mode by making both audio amplifiers in the package work like a single amplifier so in that mode, the audio chip needs two speakers connected for each channel.

Going back to your original problem. 

You have a 12v 1A ac to dc adapter.  The power this adapter can deliver to some device is determined by the formula  Power = Current x Voltage so the power for this adapter is P = 12v x 1 = 12 watts.

An ideal amplifier would take these 12 watts of power and produce 12 watts of audio power.
However, you have to understand that audio amplifiers are not ideal, and depending on their type,and they're not very efficient. The amplifier chips we're talking about here are class AB amplifiers, which usually are about 60-70% efficient.
But as you can see from that graph I showed you, with 12v input, the amplifier chip can only produce 2-3 watts of audio power without causing a lot of distortion, it just doesn't "like" such low voltages.
So you give it 12v, but produces about 3 audio watts. It probably has about 50% efficiency so the tda2050 probably uses about 6 watts out of those 12 watts you make available, the rest are unused.  If you make two amplifiers, one for each channel, both chips will use in total 12 watts or more, so your 12v 1A ac to dc adapter is to the limit.

I originally told you about 12v because computer power supplies have 12v, so it would be easy to get a used power supply from a computer or just power the audio amplifier from your computer.

But keep in mind, even if you connect it to a power supply that outputs 12v and may output 20-30 A on 12v (250-400w), the audio amplifier chips won't use this power, because they don't like such low voltages, they'll still only use about 6-10 watts.

The beauty of these chips is that you use properly rated capacitors (with big voltage rating) you can power these audio chips from 12v and get only 3 audio watts in speakers and when you find a transformer you can replace the 12v with the output of that transformer and get lots of audio watts.

For example, let's say you find somewhere a 24v AC rms transformer rated for 50 VA (a new one costs about 15-20$, on eBay they're cheaper but shipping to Greece costs anyway money).  When converted to DC, that 24v AC rms becomes about 32 volts.  The total power of the transformer is 50VA, you can equal that to 50 watts.

If you go and look on that graph, 32V DC from a single power supply is equal to about +/- 16 V so the TDA2050 could produce about 13-14 audio watts in the speaker. Now keep in mind the amplifier chip is about 60-70% efficient, so to produce those 13-14w of audio power, the amplifier "eats" about 4-6 watts and wastes it as heat, so in total the amplifier chip uses about 20w out of those 50w the transformer can give.

So even though the transformer makes 50 watts available, a single tda2050 would use only about 20 watts.  That's great, because you want stereo, so you basically have two identical circuits and in total, the two amplifier chips would use about 40 watts, which is below the 50 watts the transformer is capable of.
 
The gain of the amplifier... normally, you don't mess about with it, you just set it to a reasonable value (the one recommended in the datasheet and mentioned on that website with hi-fi amp based on tda2050) is a good one. You can always adjust the volume from your sound card. Either way, you can adjust that quite easily on a lot of amplifier chips.
The LM386 probably needs one because it distorts a lot otherwise... the lm386 is lousy for powering speakers like the ones you say you have.