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Battery amp speakers

Will automotive aftermarket speakers work well with the little battery powered amp circuits? I see them all the time at thrift shops for cheap, but the usually have really high wattage ratings. Will a 1/2 watt 9V chip amp do much with them?

I"ve heard that these small amp circuits will run large speakers, but it seems to be my experience that the larger and " better" the speaker is the quieter the amp is.

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Permalink Reply by Timothy Hunter on December 13, 2016 at 1:23am

no wonder that big ass subwoofer didnt work well. 600w? RMS or peak music power? big difference in those two.

those higher wattage speakers have a stiffer "acoustic suspension " to deal with the high power input. the magnets are also stronger and larger. and the voice coil is a much higher gauge of wire. so 3W from a 9V amp isnt going to shift that cone .

you will get more voice coil excursion if you match the speaker wattage closer to the amp output. the cone will shift more air if it can move more... 10W speakers for a 3W amp isnt to bad but the high you go the less efficient it will be . most of the power will be used in overcoming the inertia of the stiffer cone suspension .

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Permalink Reply by Gordon Cooper on December 14, 2016 at 12:42pm

It helps to remember that in essence, speakers are electric motors. They use electricity to move a metal object many times a second. The Rolling Stones have some 100K watt concert speakers that the maker of the current US (the good one) Godzilla movie used to record the 'Zilla roar in empty alleys, with the loudspeakers a mile or so away. Unique sound indeed.

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Permalink Reply by BUGGY (C) on December 14, 2016 at 12:10pm

A battery LM386 circuit will actually run a 4x12 on a battery but probably not for very long...but it does works (check those cigaraette packet amps)

kinda defies logic.... most amp circuits have a limited output but dont forget if you wire speakers in parallel it halves their resistance... ie 2x16 ohm becomes 8 ohms, or 2 x 8 ohms becomes 4 ohms and then blows up ya amp as kit was designer for 8 ohms minimum ! a big magnet is always a good thing for sound.

If a speaker is lets says rated 15 watts to 100 watts a 50 watts amp is probably ok. Generally, more amp than is needed. What you want is an amp that has good peak power(also called dynamic headroom). Most of the time the amp isn't putting out a lot of power but certain peaks can hit 200 watts or a lot more depending. It depends on what you are listening to, what volume and etc.

But the frequency response is key 20hz-20,000hz is about right, the lower the more bass.

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Permalink Reply by BUGGY (C) on December 14, 2016 at 12:14pm

for example

https://www.youtube.com/watch?v=TY_xZgZfJek

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Permalink Reply by BUGGY (C) on December 14, 2016 at 12:17pm

with a remote 9v feed you could probably gig a smokey amp via decent 4x12 cab

https://www.youtube.com/watch?v=GpKH2wGtvXg

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Permalink Reply by BUGGY (C) on December 14, 2016 at 12:22pm

https://www.youtube.com/watch?v=QwaLQ04I04s

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Permalink Reply by BUGGY (C) on December 14, 2016 at 12:30pm

Image result for lm386 circuit for guitar amp

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Permalink Reply by Scott aka Farmer Ted on December 14, 2016 at 1:37pm

Nice schematic Buggy. Seen this one before. The one I've made for years uses a 0.1uF bypass cap from pin 7 to ground, and omits the 0.047uF cap & 10 ohm resistor on the pin 5 to ground.

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Permalink Reply by John Sawyer on December 14, 2016 at 6:10pm

If you use a 1K pot between pins 1 and 8 instead of the cap, you can vary the gain...

Every LM386 circuit I have seen also calls for a cap on the input... prevents feedback loops or something...

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Permalink Reply by Paul Craig on December 15, 2016 at 7:21am

The Ruby Amp and Noisy Cricket Amp uses a 1k pot for gain pins 1&8,100nf on pin 7 and they use a 220uf on the output to speaker pin 5 like above.

My dual chip amp build, I used 2k pots, 100nf pin7 for both chips, but when it came to the output caps from both chips I had to use 10uf or the treble was too great for the speaker I chose. The speaker was a WGS Veteran 10" 20watt 8ohm. So the way your speaker is voiced will also have a influence on output cap values or you'll have to go through several speakers to find the one that works with the 220uf cap. Also my problem could've been because my amp design was 2 chips bridged that added a capped output to the negative side of the speaker.

Point is, you may need to try a couple different value caps to get the results you want. If you burn out something, you haven't lost much on these amps which makes them a great learning platform.

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Permalink Reply by John Sawyer on December 15, 2016 at 11:40am

I haven't seen a lm386 bridge circuit, sounds intriguing... great point on selection of output caps. Given the cost of chips vs off the shelf build amp boards, it is hard to compete... of course for myself, I'm up for the challenge.

I have found that the fret based preamp circuit helps a piezo on these a lot... http://www.till.com/articles/GuitarPreamp/

Or you can buy an acoustic preamp and mount it to the box...