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Ohms, Subwoofers and Amplifiers

OHMS, SUBWOOFERS and AMPLIFIERS

Describing Flow Through a Mobile Audio Pathway

PLAYER -> SIGNAL PROCESSOR -> AMPLIFIER -> SPEAKERS

The topic today refers to the last pair of modules of a total of four that complete the Mobile Audio Pathway. Refer to the previous article. I believe if we can’t have an audio system that plays loudly, clearly and with good balance, for a long time reliably then what is the point? 

Ever heard the saying “It’s so hot you could cook an egg on that?” That’s the sort of condition I would like you to plan to avoid when planning to run subwoofers and an amplifier to power them.

car amp cooking eggs
Click for the video.
ShowtimeSPL
Published on Jun 21, 2012
Once again we see Hank Veach showing off. His amps got hot enough to fry an egg on.

Review: Why do we need an amplifier? 

Answer: Small signals must be multiplied to get the loudness we desire out of our speakers.

Why? Speakers, as we use them in mobile audio systems, are very inefficient. Most of the signal, the voltage, that gets to the speaker is lost as waste heat. 

Amplifiers are much more efficient than speakers, yet they still lose a great amount of energy as heat.  

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Review: What are “Ohms” and why is it so important with subwoofers and amplifiers? I am not going to get into all of the “Whys” as it will end up requiring many thousands of words. I do strongly recommend you follow the link in the carton image below to refresh your knowledge of Ohm’s Law. 

Disclaimer: If you want to be able to confidently design and build out a reliable mobile audio system you cannot do it without understanding electricity.  ‘Basic Installation Technician Study Guide’, published by MECP under the Consumer Electronics Association, is a book I strongly recommend for anyone who wants to learn to earn a living with mobile audio systems.

Ohms law cartoon
Click to learn “How to Use Ohms Law”

Common mistake: mixing up where the Ohms come from in the amplifier+subwoofer relationship

RIGHT: We speak of Ohms with the subwoofers, specifically the voice coils.

WRONG: An amplifier does not “have” Ohms.

LOWER OHMS = MORE HEAT AND MORE RISK OF THE AMPLIFIER SHUTTING OFF

MTX Audio has provided a web site to help you to know if your subwoofer and amplifier combination is compatible. You can go through this exercise to be a more empowered DIY shopper, or you can use this to double check my recommendations for you.

Subwoofer Wiring Diagrams

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Barry Schanz
Rubyserv
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sales@rubyservsales.com