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10 ohm front speakers - is it important with factory radio?
Is it important to have 10 ohm speakers up front with factory radio? The original design put 10 ohm speakers in front, 4 ohm in back. If one was to replace with 4 ohm up front, the new speakers would draw more than twice the current of 10 ohms? Is this going to be a problem for the amplifiers? Is this going to be a problem in getting the sound to balance because the new speakers would be louder due to the higher current draw?
Re: 10 ohm front speakers - is it important with factory radio?
Gave my man John Henshaw at Precision Radio a call concerning this. Admitted he wasn’t certain but if had to venture a guess GM had a lot of 10 ohm 4x6 they needed to unload from the days of transistors, discrete that is. Said some of the newer delco that used the DM165 amps used 4 ohms all the way around. said older discrete transistor radios would burn up if 10 ohm not used
guess this makes sense cause the rears are 4 ohm being driven by same amps. the only thing that could be different is pre/post circuitry on the amps. need some schematics!
One thing thing i didn’t think of asking is maybe they had multiple 4 ohms in series up front.......
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by LiquidBlue
Is it important to have 10 ohm speakers up front with factory radio? The original design put 10 ohm speakers in front, 4 ohm in back. If one was to replace with 4 ohm up front, the new speakers would draw more than twice the current of 10 ohms? Is this going to be a problem for the amplifiers? Is this going to be a problem in getting the sound to balance because the new speakers would be louder due to the higher current draw?
Read thru this again:
Think of the speaker as a pipe. The audio signal — your music — acts as the water flowing through the pipe. The bigger the pipe, the more easily water can flow through it. Bigger pipes also handle more volume of flowing water. A speaker with a lower impedance is like a bigger pipe in that it lets more electrical signal through and allows it to flow more easily.
As a result, you see amplifiers that are rated to deliver 100 watts at 8 ohms impedance or 150 or 200 watts at 4 ohms impedance. The lower the impedance, the more easily electricity (the signal or music) flows through the speaker. A lot of amplifiers aren't designed to work with 4-ohm speakers. Using the pipe analogy, you can put a bigger pipe in, but it'll only carry more water (audio) if you have a pump (amplifier) powerful enough to provide the extra flow of water.
Impedance of Car Speakers
In car audio, 4-ohm speakers are the norm. That's because car audio systems run on 12 volts DC instead of a 120 volts AC. A 4-ohm impedance allows car audio speakers to pull more power from a low-voltage car audio amp. Car audio amps are designed for use with low-impedance speakers. So crank it up and enjoy.
If you run an 8-OHM up front rather than the 4-OHM your not really running "louder" speakers: The same AMP will produce more watts at a lower OHM ----> Allows more "water" thru the larger "pipe".
There are a ton of older GMs that used a 4-OHM 4x6,... I used to pull them from first gen S10 Blazers all the time when I couldn't find a Camaro/Firebird parts car. Some GM front speakers might need the mounting holes re-drilled for the model they were installed in, but most are the same basic 4x6 4-OHM speaker they used thru the 70's & 80's. I figure there's GOT to be someone still making aftermarket 4x6 as "stock" replacements for Thirdgens ?!?!
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by John in RI
If you run an 8-OHM up front rather than the 4-OHM your not really running "louder" speakers: The same AMP will produce more watts at a lower OHM ----> Allows more "water" thru the larger "pipe".
This is exactly my question (well almost) I asked if the 4 ohm speaker would be louder? (Which I had more or less concluded they would because at same volume more current would be running thru them). So there are really 3 questions here.
Q2) I also asked if it would damage the amplifiers by running 4 -vs- 10 ohm.
Q3) And also asked if maintaining balance would be an issue, because now the front speakers are running louder (BTW - I do understand Ohms law, these questions really don't pertain to Ohms law)
To further elaborate, I realize there is a balance control if the fronts are too loud when using 4 ohms, but I'd venture a guess the circuitry is cheap and using it comes at a cost in distortion.
Originally Posted by John in RI
There are a ton of older GMs that used a 4-OHM 4x6,... I used to pull them from first gen S10 Blazers all the time when I couldn't find a Camaro/Firebird parts car. Some GM front speakers might need the mounting holes re-drilled for the model they were installed in, but most are the same basic 4x6 4-OHM speaker they used thru the 70's & 80's. I figure there's GOT to be someone still making aftermarket 4x6 as "stock" replacements for Thirdgens ?!?!
There are, they Delcos and made in China and available on Amazon. Its a matter of do they sound any good -vs- 4 ohm after markets that are available today -vs- the above questions.
Re: 10 ohm front speakers - is it important with factory radio?
I normally avoid these type of speaker questions because of the many misunderstandings that surround speaker ratings , but I will tell you this from my many years of working with electronics ;
If you have an amplifier designed to play into a 10 ohm speaker , and you hook up a 4 ohm speaker to that amp , the amp is gonna run too hot trying to drive that speaker . Back in the days of good ol vacuum tubes you could get away with improperly matched speaker/amp combinations but semiconductors (be they discreet packages of one semiconductor only or integrated packages of multiple semiconductors) are notoriously heat sensitive and anything that makes them run hotter than their design rating is a recipe for early failure .
I would feel pretty comfortable replacing a 10 ohm speaker with an 8 ohm unit , but with 4 ohms being less than half of the designed for 10 , I feel that excessive load would produce damaging heat levels ....
Last edited by OrangeBird; 09-10-2019 at 09:53 AM.
Reason: typos
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by OrangeBird
If you have an amplifier designed to play into a 10 ohm speaker , and you hook up a 4 ohm speaker to that amp , the amp is gonna run too hot trying to drive that speaker ..
checkout post #3 above, let me know what you think
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by LiquidBlue
checkout post #3 above, let me know what you think
I would love to see a schematic of the amp , that would pretty much tell all . It's my belief that if they (Whoever actually built the radios for GM) used 4 ohm in back and 10 ohm in front , they engineered the amp to drive the differently rated speakers . But then , I could very well be wrong , and if the amp was actually designed to drive four 4 ohm speakers you'd be fine , I just personally find the "had a bunch of old speakers they had to use up" reason to be kinda far fetched .
Unless I was 100% sure , I'd still try for 8 ohm rather than 4 ohm if I could find them .
finding an 8 has turned up zero in my searches so far. they don't seem to exist. which is pretty much at how I arrived at starting this thread. I am finding acdelco 10 ohm, but that is only choice. was hoping for something a little better.
Re: 10 ohm front speakers - is it important with factory radio?
"One DM165 is for the front and rear left speakers, the other DM165 is for the front and rear right speakers. This way each DM165 drives a 10ohm front speaker, which requires very little power, and a 4 ohm rear speaker. I think they also did this to prevent left and right channel cross talk."
Hi Jim , Thank You for posting that link with the schematic . I cut & pasted the above statement from the link and I believe now even more strongly that the output chip would overheat if it were made to drive two 4 Ohm speakers . Since he made specific mention of the use of the 10 ohm speaker "Which requires very little power" , that leads me to think it'll overheat with two 4 Ohm VS the 4 and 10 ohm .
Last edited by OrangeBird; 09-10-2019 at 04:48 PM.
Re: 10 ohm front speakers - is it important with factory radio?
After seeing the schematic you led me to I went crazy looking for the spec sheet on the DM165 audio output chip , and the best I could find is that it's got two outputs (one each for a front and rear speaker) and it's good for 20 watts total power to the speakers . With only 20 watts* to work with I can see where they'd want to direct a bit more power to the back with the lower Ohm speakers , the front speakers being far closer to the driver's ears than the rear speakers are .
* That 20 watts is per side , 20 watts to the left rear and left front from one DM165 , and 20 watts to the right rear and right front from the other DM165 for 40 watts total radio output across the 4 speakers (each radio having two , a left and a right DM165) .
Re: 10 ohm front speakers - is it important with factory radio?
great point. i’ve heard complaints of folks putting 4 ohm up front and too loud before covering with acoustic cloth. the link i put has the pin out of the DM165s. did you see that? no spec, but at least you know what each pin is for. these must be proprietary delco chips, or at least designed specifically for them and them only. i’ve seen posts around the web of people trying to find pin compatible amps with no success.
Re: 10 ohm front speakers - is it important with factory radio?
I believe your right about them being proprietary Delco , because most times when I search a semiconductor's spec sheet I come up with an ECG or other manufacturer cross reference , and I found precious little in my searches about the DM165 .
Re: 10 ohm front speakers - is it important with factory radio?
thought just popped into my head. if these amps are providing 10W / channel - then maybe the only thing that really matters is heat production as far as amp output goes.
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by rt66er
Okay, you got me paranoid now. Ordered some 50w 6 ohm resistors from Amazon yesterday.
Hoping to get OrangeBird re-engaged on this. There are actually 2 channels per DM165 (Channel A and Chanel B) with 2 DM165s for a total of 4 channels each handling its own speaker. Not 1 channel, handling 2 speakers. So the issues isn't about over-driving an amp by having one-4ohm and one-10ohm speaker on that channel. Its about switching a channel that previously had a 10 ohm speaker on it to 4 ohms. We have no way of knowing, because there is no spec sheet, but, I'd assume each channel is perfectly capable of handing the same amount of power, but is the rest of the circuitry and the heat sink up to the task of having both channels each drive 4 ohm speakers.
I didn't catch what he said yesterday, was feeling a little under the weather.
Re: 10 ohm front speakers - is it important with factory radio?
Hi Jim , yes there are two channels in each DM165 , and so we have two DM165 chips driving four speakers . Looking at the schematic you just posted the amp's output channels have identical components , so if there is any difference it would be in the chips themselves . I do believe your right in that as long as you don't ask more than 20 watts total from the chip it'll be fine regardless of whether the front speakers are 4 or 10 ohm , the one caveat here being that with the 4 ohm speakers it'll be far easier when cranking the music to draw more than the 20 watt limit , causing overheating of the chips .
Re: 10 ohm front speakers - is it important with factory radio?
just installed new 6x9 today. they are plenty loud, so i ordered some 10 ohm delco’s up front. i’m getting some weird behavior. right rear is louder thAn driver side. hoping it’s due to front speakers are bad. the same holds true for factory fronts. pass louder than driver.
also, sometimes the volume suddenly gets quiet or loud as i move dials. hoping it’s the fronts. dash unit was bench tested as good
Re: 10 ohm front speakers - is it important with factory radio?
OK,..... I'm sure that what I'm about to describe is probably effected by the power source being used - a car battery connected to my testing station - however; I do not have electrical problems when testing any other devises on my set-up. ( Used for MUCH more than just radios ! ) While the amount of 'juice' in this battery is probably limited,... this little experiment shows the effect that running 4 OHM speakers has on a factory Delco head unit.
Speakers used: 4 factory Delco( 2-4 OHM and 2 10 OHM) ; then 4 aftermarket Pioneer (4 OHM); then a combination of 2-&-2 ; then reverse of the 2-&-2.
1) When just 2 4 OHM speakers were matched with 2 factory speakers (Front-Pioneer/ Rear Delco or Front Delco and Rear Pioneer) The head unit continues to produce sound at max volume.
2) When all 4 Delco speakers are used the Head Unit continues to produce sound at MAX volume.
3) When all 4 aftermarket 4 OHM speakers are used the Delco Head Unit "quits' before reaching full volume. ( varies depending on how much the BASS and TREBLE are adjusted
** At 1 point I called the aftermarket speakers "4-AMP",... I meant 4 OHM
** Battery charger was NOT connected at any time of test.
I'm sure that a battery that's in regular use might push enough power to keep the Head Unit to keep working all the way to full volume,... but there was really not a noticeable of a drop in the voltage during this video. This little exorcise is not an attempt to declare ANYTHING !!! It's simply an attempt to show that using 4 OHM speakers puts a lot more stress on a Delco Head Unit than using speakers that the Head Unit was designed for.
Last edited by John in RI; 05-07-2024 at 10:58 AM.
Reason: Edit: OHMs
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by John in RI
OK,..... I'm sure that what I'm about to describe is probably effected by the power source being used - a car battery connected to my testing station - however; I do not have electrical problems when testing any other devises on my set-up. ( Used for MUCH more than just radios ! ) While the amount of 'juice' in this battery is probably limited,... this little experiment shows the effect that running 4-OHM speakers has on a factory Delco head unit.
Speakers used: 4 factory Delco( 2-4OHM and 2 10OHM) ; then 4 aftermarket Pioneer (4-OHM); then a combination of 2-&-2 ; then reverse of the 2-&-2.
1) When just 2 4 OHM speakers were matched with 2 factory speakers (Front-Pioneer/ Rear Delco or Front Delco and Rear Pioneer) The head unit continues to produce sound at max volume.
2) When all 4 Delco speakers are used the Head Unit continues to produce sound at MAX volume.
3) When all 4 aftermarket 4OHM speakers are used the Delco Head Unit "quits' before reaching full volume. ( varies depending on how much the BASS and TREBLE are adjusted
** At 1 point I called the aftermarket speakers "4-AMP",... I meant 4 OHM
** Battery charger was NOT connected at any time of test.
I'm sure that a battery that's in regular use might push enough power to keep the Head Unit to keep working all the way to full volume,... but there was really not a noticeable of a drop in the voltage during this video. This little exorcise is not an attempt to declare ANYTHING !!! It's simply an attempt to show that using 4OHM speakers puts a lot more stress on a Delco Head Unit than using speakers that the Head Unit was designed for.
Please clarify, edit as needed. .........you typed 40OHM and 10OHM, did you mean 4 OHM and 10 OHM? I am trying to figure this out and that would help me(& others) understand. Thanks.
Re: 10 ohm front speakers - is it important with factory radio?
Originally Posted by mikeceli
Looking forward to an update.
Guess something happened back then. I gave up on the factory stereo, its horrible. bought a huge JBL Extreme 3 portable speaker and strap in to the back seat with the rear seatbelts and jam! So very tempted to go aftermarket.... which they made a repro for our factory systems
Last edited by LiquidBlue; 11-05-2022 at 12:27 PM.
Re: 10 ohm front speakers - is it important with factory radio?
The one thing I have learned, in general, restoring old cars, is --- if you keep to the original specs -- you are going to build a gem, because engineers get paid to make all the components to work together for many many years. If 10 ohm is available, and I have that, and it sounds good, at 10, then just use it. I did learn a lot on this thread though. I will say. Anyone to wants to disrespect these old Delco stereos - let me tell you something from an old guy who lived through this period and prior periods of GM sound:
1) Delco worked with BOSE to FINALLY learn how to build GREAT sounding 4 speaker stereos in the 1980's because up till the late 70's, the one speaker am/fm radio was way to old fashioned so they came up with this setup which was AWESOME at the time, us young's were TIRED of buying a car and immediately replacing the stereo. So in 1982 and beyond, we were VERY happy with these.
2) We all really like these stereos, so that's why we are on here trying to figure them out - so please keep the faith - it's good!
09-08-2019, 09:49 AM
Unless I was 100% sure , I'd still try for 8 ohm rather than 4 ohm if I could find them . 
