Is there a way to limit speaker output?

[phil]

I just wanted to ask if there might be a simple way to limit the output of the speaker voice coil.

Many early sets don’t have AGC, could the amount of power available to the voice coil be limited somehow to avoid tuning them to strong local stations and blowing the fragile speaker?

I also see this issue with my modern TV/ stereo arrangement. especially now with various sources like netflix and Utube. The output levels are so different that it’s easy to get commercials blasting way higher that any sane person would set the volume. It would be nice to install something that could clip anything beyond a certain volume so no matter where the volume is set it could only get so loud.

Any simple solutions to this issue? Something that could just be installed in line with the speakers to limit how loud it can go?

Phil

[Steve Dow]

Hello Phil,
The simple solution to limit the power level to a speaker, to a fraction of the
maximum power that the amplifier can produce, is to use a ‘pad’ .

In audio we use this term to denote an attenuator, connected in an audio feed line.
The most common pad available is called an L pad. This control reduces the power level
of a speaker, while maintain a constant impedance load for the amplifier. There are
many 8 ohm L pads available on the net.

A more advanced pad, in this group is a T pad. It does everything a L pad does, and also
maintains a constant load as seen by the speaker, back down the line. This is key, where speaker
damping is an issue.

Your tern ‘clip’ , could change to limiter. Clipping in audio. is bad.
A clipped signal may contain frequency components that can blow small speakers i.e.
tweeters.

A interesting device for audio is a DBX 117 compressor/expander. They come up on E-Bay.
This device can maintain a level automatically, but not in a speaker line.

Old telephones had a device across the earpiece device to limit the sound pressure
level for hearing protection when large voltages got on the line.

[phil]

Thank you for your in depth reply Steve. I see there is a DBX 117 compressor/expander on ebay. I think I mainly just wondered if it would be a simple feat to limit the output level and I guess it isn’t so simple as adding a few little components to the speaker line. I guess I could have also substituted AGC ( automatic gain control) with AVC automatic volume control.
Phil

[Steve Dow]

If it is a very early radio, the volume can be controlled by a variable resistor
in the antenna circuit, similar to half of the Philco model 20 pot.

If you found a suitable CdS cell, you could illuminate it with small light bulb connected to
speaker circuit.

Electronic Goldmine had some large ones on sale a while ago. Those go from 2500 to 200 ohms
room light, to a flashlight directed.

[Author]

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