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Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
I have recently been experimenting with an audio amplifier chip that I found, the LA4705.
I just have one question regarding the output section. In the datasheet the schematics show that the output end where the speakers connect are labelled inverting and non-inverting out, the speakers connect directly across them.
But I am unsure as to what polarity I should connect my speakers, Do I connect the + side of the speaker to the inverting or non-inverting pin? Below is the schematic from the datasheet:
So basically I am asking what pin connects to the speakers + terminal and what pin connects to the - terminal.
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Per the speaker, it really doesn't matter. The speaker doesn't care if its wired either way. However, as a listener, you want to wire it so the phase between your two speakers is the same (and with other speakers, if there are any, in your system)
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
EasternVoltageResearch wrote ...
Per the speaker, it really doesn't matter. The speaker doesn't care if its wired either way. However, as a listener, you want to wire it so the phase between your two speakers is the same (and with other speakers, if there are any, in your system)
So are you saying that how it is wired in the datasheet is wrong?
I do notice a slight difference in sound depending on which way I connect the + and - terminals of the speaker, but am unsure which is the right way of connecting it (like how it would be connected in a consumer audio device).
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061
Google "Bridge Tied Load" (BTL)
This essentially doubles output from the same chip by driving each side of the speaker out of phase.
Also you do need an output Zobel, consisting of a 10 ohm resistor and 0.1uF capacitor in series. This ensures stability which prevents smokeage on amplifiers if it ever tries to oscillate at RF.
Some speakers do sound different if you drive them negative (ie centre to in) as it causes resonances inside the support frame. Normally this is only an issue with headphones but I've had this happen before on a bass speaker which already drives the coils at close to their destruct point.
(does patent search for wirelessly powered speaker coils..)
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Conundrum wrote ...
Google "Bridge Tied Load" (BTL)
This essentially doubles output from the same chip by driving each side of the speaker out of phase.
Also you do need an output Zobel, consisting of a 10 ohm resistor and 0.1uF capacitor in series. This ensures stability which prevents smokeage on amplifiers if it ever tries to oscillate at RF.
Some speakers do sound different if you drive them negative (ie centre to in) as it causes resonances inside the support frame. Normally this is only an issue with headphones but I've had this happen before on a bass speaker which already drives the coils at close to their destruct point.
(does patent search for wirelessly powered speaker coils..)
-A
It already has zobel networks, that is what the 2.2 ohm and 100nF caps form isn't it?
But still what pin (inverting or non-inverting) does the + terminal of the speaker connect to? That is all I really want to know
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Conundrum wrote ...
Some speakers do sound different if you drive them negative (ie centre to in) as it causes resonances inside the support frame. Normally this is only an issue with headphones but I've had this happen before on a bass speaker which already drives the coils at close to their destruct point.
I don't see how a basic speaker would sound different if wired in opposite phase by itself. A speaker is just a magnetic coil and the output is an AC signal. So unless you had several speakers operating together in a system, then phasing really should make a difference one way or another as far as sound or function goes.
If i took any subwoofer and fed it a 100Hz sine wave, and then fed it a 100Hz 180 degrees out of phase, you would not be able to hear the difference nor would it create any different resonances within the speaker etc...
Of course, if you had an isobaric (push-pull) subwoofer arrangement, you would want them wired 180 degrees out of phase from one another.
wrote ...
But still what pin (inverting or non-inverting) does the + terminal of the speaker connect to? That is all I really want to know
IT DOES NOT MATTER!
The only thing that matters is if you have a stereo pair, you want BOTH speakers to have the same polarity.
A speaker is just an inductor (simplied). Polarity either way will not change the operation of the single speaker.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
EasternVoltageResearch wrote ...
The only thing that matters is if you have a stereo pair, you want BOTH speakers to have the same polarity.
A speaker is just an inductor (simplied). Polarity either way will not change the operation of the single speaker.
Hmm didn't know that, thanks.
It was just I was told by someone that it can make the speaker cone move inwards if you have it hooked up the wrong way causing the speaker to sound "backwards".
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've read on some car forum that you get a better sounding stereo if you wire the driver's door speaker and passenger door speaker with opposite polarities, but it sounds dubious to me. It's supposed to give a 'fuller sounding stereo' where the speakers are opposite each other. I've not tried it though.
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Alex1M6 wrote ...
EasternVoltageResearch wrote ...
The only thing that matters is if you have a stereo pair, you want BOTH speakers to have the same polarity.
A speaker is just an inductor (simplied). Polarity either way will not change the operation of the single speaker.
Hmm didn't know that, thanks.
It was just I was told by someone that it can make the speaker cone move inwards if you have it hooked up the wrong way causing the speaker to sound "backwards".
Inward how? The output wave is AC, and should have no DC component. It will always move out and in. If you have enough DC bias so that the speaker doesnt move inwards from its at-rest position, then bad thingsâ„¢ tend to happen.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Why would this BTL chip show speaker polarity in its datasheet if it doesn't matter?
Confused(.com)
@ConKbot of Doom Just from looking at the speaker cone when I touch the audio input, it does move in or out slightly depending on which way I have it connected.
I measured the voltage between the output pins and there is about 100mV DC between pins 17-15 and 14-12, with the non-inverting sides being the more positive pins.
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Inverting and non inverting outputs on an audio amplifier chip
