Electronics > Beginners
putting a resistor in series with a speaker to increase the impedence
james_s:
YMMV, but in my own experience it works fine to drive a 4 Ohm speaker from an amplifier designed for 8 Ohm speakers. This may not always hold true but I can't think of a case where I've had any trouble with it so long as the volume is kept at a reasonable level.
Something else you can do is drive a pair of 4 Ohm speakers in series on each channel.
Zero999:
--- Quote from: johnkenyon on July 27, 2018, 12:16:55 am ---
--- Quote from: Hero999 on July 26, 2018, 11:16:52 am ---The mute function can be used, as described in the TDA7492P data sheet. Failing that, use the timer relay circuit to bypass the current limiting resistor, once the surge has passed. 5 seconds is probably much longer than necessary. 1 second or less will do.
--- End quote ---
Three ideas:
1) Use the suggested circuit, but bypass the current limiting resistor with a normally closed relay contact, and have a timer which energises it for 5 seconds.
2) Put a normally closed relay contact on the power rail between the reservoir capacitor and the load and drive the relay for 5 seconds at power up time.
That way, you have 5 seconds of the battery feeding capacitor only, followed by the battery topping off the capacitor and powering the load.
3) Have the battery circuit permanently connected to the reservoir capacitor and switch the amp on afterwards.
Same as 2 above, but the relay contacts are replaced by the on/off switch - no timer required.
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1) The problem with that is it takes a finite time for a normally closed relay's contacts to open and it will need to break the full current surge, so will be less reliable, than a normally open contact.
2 & 3) Good ideas, but it might be difficult/impractical to break the connection between the reservoir capacitor and amplifier, if the PCB is already made.
--- Quote from: james_s on July 27, 2018, 03:31:38 am ---YMMV, but in my own experience it works fine to drive a 4 Ohm speaker from an amplifier designed for 8 Ohm speakers. This may not always hold true but I can't think of a case where I've had any trouble with it so long as the volume is kept at a reasonable level.
Something else you can do is drive a pair of 4 Ohm speakers in series on each channel.
--- End quote ---
Yes an amplifier designed of a 4R speaker should be fine with an 8R load.
I wouldn't recommend connecting speakers in series, because it will result in a poorer damping factor and more peaks and troughs in the frequency response.
Adhith:
Thank you every one once again for all those sincere and detailed explanation. I'll build one such circuit and let you guys know about the result.
Audioguru:
--- Quote from: Hero999 on July 27, 2018, 07:58:23 am ---I wouldn't recommend connecting speakers in series, because it will result in a poorer damping factor and more peaks and troughs in the frequency response.
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Players of electric guitars like that awful sound and call it "effects".
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