10 ohm or 4 ohm speakers what? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

77 lowboy · 03-30-2014, 05:06 PM

i dont want to cut dash in 77 so going to use original am fm radio. when shopping for speakers i was told that original speakers were 10 ohm and all new stuff is pretty much 4 ohm. also told to run 4 ohm speakers i would need an amp or i would burn up output on radio. im not really a electronic guru and just want a decent sounding fm radio please help with any info.

ray_mcavoy · 03-31-2014, 12:57 AM

Yes, the 60's & 70's GM/Delco radios were designed for use with 8 to 10Ω speakers and should not be used with the 4Ω speakers that are common nowadays.

It's also important not to operate these older Delco radios without a speaker attached. Due to the way the output transistor is connected to the output transformer, it can see some dangerous inductive feedback when operated without a speaker. Connecting the Delco radio's output to an amplifier with a high imput impedance is similar to operating it without a speaker ... not good. I suppose you could put a resistor in there to provide the necessary load and still connect it to an amp.

Fortunately, you can purchase new 10Ω speakers that will work with your original radio (and fit the stock dash location) from places like S&M Electro-Tech --> http://www.turnswitch.com/speakers.htm I used one of their 4x10 speakers in my 74 Nova and it actually sounds pretty good ... for a 40 year old radio anyway.

Another option would be to use a radio from a slightly newer GM car or truck. It's my understanding that the 79 & newer Delco electronic tuning (ETR) stereos have amplifiers that can safely drive 4Ω speakers. Here's an example --> http://67-72chevytrucks.com/vboard/s...79&postcount=5 I put a stereo like that into Dad's 77 GMC and it was a direct fit (no dash cutting necessary). I did have to add some wiring because the 78-up radios use different plugs and the ETR units need a couple extra wires for the clock/memory and a display dimmer signal.

motornut · 04-10-2014, 11:59 PM

I used two smaller ones up front,to get left right.
fit right in there
I'd check the junk yard some times you get lucky...i did

03-30-2014, 05:06 PM	#1
77 lowboy Registered User Join Date: Jan 2014 Location: toledo oregon Posts: 17	10 ohm or 4 ohm speakers what? i dont want to cut dash in 77 so going to use original am fm radio. when shopping for speakers i was told that original speakers were 10 ohm and all new stuff is pretty much 4 ohm. also told to run 4 ohm speakers i would need an amp or i would burn up output on radio. im not really a electronic guru and just want a decent sounding fm radio please help with any info.

03-31-2014, 12:57 AM	#2
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,361	Re: 10 ohm or 4 ohm speakers what? Yes, the 60's & 70's GM/Delco radios were designed for use with 8 to 10Ω speakers and should not be used with the 4Ω speakers that are common nowadays. It's also important not to operate these older Delco radios without a speaker attached. Due to the way the output transistor is connected to the output transformer, it can see some dangerous inductive feedback when operated without a speaker. Connecting the Delco radio's output to an amplifier with a high imput impedance is similar to operating it without a speaker ... not good. I suppose you could put a resistor in there to provide the necessary load and still connect it to an amp. Fortunately, you can purchase new 10Ω speakers that will work with your original radio (and fit the stock dash location) from places like S&M Electro-Tech --> http://www.turnswitch.com/speakers.htm I used one of their 4x10 speakers in my 74 Nova and it actually sounds pretty good ... for a 40 year old radio anyway. Another option would be to use a radio from a slightly newer GM car or truck. It's my understanding that the 79 & newer Delco electronic tuning (ETR) stereos have amplifiers that can safely drive 4Ω speakers. Here's an example --> http://67-72chevytrucks.com/vboard/s...79&postcount=5 I put a stereo like that into Dad's 77 GMC and it was a direct fit (no dash cutting necessary). I did have to add some wiring because the 78-up radios use different plugs and the ETR units need a couple extra wires for the clock/memory and a display dimmer signal.

04-10-2014, 11:59 PM	#3
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: 10 ohm or 4 ohm speakers what? I used two smaller ones up front,to get left right. fit right in there I'd check the junk yard some times you get lucky...i did Attached Images __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350



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