series, parallel subwoofer relays?

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Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=112169
Printed Date: July 16, 2025 at 8:45 AM

Topic: series, parallel subwoofer relays?

Posted By: uncko_macko
Subject: series, parallel subwoofer relays?
Date Posted: March 07, 2009 at 8:31 AM

I have a 1700 watt MMATS amp and 2 Dual 2 ohm Kicker L7 12's. Its a daily driver and I do not need this crazy power all the time. I've blown the back window out of my Blazer 4 times. I would like to install relays to switch from series to parallel and back, or just take 1 sub out of the circuit all together by the flick of a switch. I've never seen or heard of this being done before. Are there any audio grade relays or contactors that would handle the kind of power the MMATS puts out?(without losing quality) Also would this impedance switching cause any damage to the amp itself?

Thanks!

Replies:

Posted By: i am an idiot
Date Posted: March 07, 2009 at 11:38 AM

Switching from Series to Parallel and Back

When the relays are at rest (normally closed position) the woofer coils are wired in series. When ground is applied to each coil (energizing the relay coils), the voice coils are wired in parallel. With 2 four ohm voice coils you'll have an 8 ohm load at rest and a 2 ohm load when the relay coils are energized.

For each dual voice coil woofer that you want to change from series to parallel, you'll need two relays for each. They can all be controlled from the same switch.
posted_image

Posted By: uncko_macko
Date Posted: March 10, 2009 at 3:29 PM

Do you know of a higher current relay? Brand? Part number? Maybe something that I can hook up to 8AWG speaker wire?

Posted By: i am an idiot
Date Posted: March 10, 2009 at 4:49 PM

These relays are rated at 30 amps. If you need more current capacity than that you could parallel another relay with each one in the pic. 4 relays total and 60 amps of current capacity.