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LM3886 68W amplifier design: needed ur suggestions/opinions

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GraveYard_Killer

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i have this partial schematic here for the lm3886 68W amplifier. i want to build a 2.1 speaker system. my problem is how do i connect the woofer to have the L and R channel be audible to the woofer? if i will connect the one end of the woofer to both L and R, then the one terminal to ground, I will be shorting the L and R channel of the amplifier. Are the speakers all right for the lm3886? What are the critical computation that will be involved here? Thanks in advance.

**broken link removed**
 
I would use separate amps for the sattelites and the woofer, each with a specific filter on them (low pass for the woofer,...)
merging the inputs could then be done with simple resistors...

The only thing i can think of to merge your outputs is also with resistors, but you'll lose a lot of your power in those resistors...
 
is it not possible to hook up all those three speakers to the lm3886 amplifier? thanks for answering my post.
 
GraveYard_Killer said:
is it not possible to hook up all those three speakers to the lm3886 amplifier? thanks for answering my post.

You really need to use a seperate amplifer, that way you can individually control the frequency and levels of the different drivers.

Passive sub-woofers are possible, but it's far more complicated to do, the best option is to use a specific sub-woofer speaker, this has two voice coils with each fed from one channel. You still need to provide two large and expensive passive filters though - and you need all the speakers specifically designed to work together in this fashion, as you've no control over the levels.
 
It's been awhile since I looked into filters and crossovers, but can't you use an ?active? filter (I think its called active, it's the filter that's used after the signal has been amplified). You'll lose a lot of power this way, but atleast you have some control over the frequencies going to each speaker
IIRC you should be able to just use an inductor on the woofer and a cap on the mid range. It won't sound that great, but it's a start.
I think I searched for DIY and crossover, there's a whole bunch of info on this.
 
jrz126 said:
It's been awhile since I looked into filters and crossovers, but can't you use an ?active? filter (I think its called active, it's the filter that's used after the signal has been amplified).

Wrong way round :D - that's a 'passive filter', as I mentioned above!.

His problem isn't really filtering, it's how to feed one mono sub-woofer from two stereo channels.
 
thanks for answering my post.

yeah nigel is right. my only problem is how to connect the subwoofer and what are the consideration for the power requirements.
ok lets say i will remove the two speakers and place the two midrange in two separate LM386 low voltage amplifier (one lm386 for each midrange).
how do i connect the woofer with the lm3886 68W amp to have the L and R audible? am i doing it right here:

**broken link removed**
 
No, the woofer requires a mono amp and you should merge the L and R channel at the input. This can be done with simple resistors
 
Exo said:
No, the woofer requires a mono amp and you should merge the L and R channel at the input. This can be done with simple resistors

can u point me to a site that does this kind of setup or any examples, also computation of the resistors needed? TIA
 
GraveYard_Killer said:
how do i connect the woofer with the lm3886 68W amp to have the L and R audible? am i doing it right here:

You need some active filters, one feeding each mid-range amp that removes the low frequencies, and one to remove the high frequencies for the sub-woofer - this should also have a mixer on the front, which adds the two channels together. As already suggested, the mixer could be as simple as a couple of resistors.

Have a look at **broken link removed** for a suitable sub-woofer processor.
 
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