[grd777]

is it just a simple thing like adding a jumper wire

[JUDGE3]

use these on the speakers.

and enjoy the view in the trunk. and really enjoy getting out of the trunk.

your stereo should have a connector for separate speakers wires.

[necdb3]

Originally Posted by grd777

is it just a simple thing like adding a jumper wire

No!!!! You cannot just add a jumper from your other speaker. It will cut the resistance in half and burn your amp out.

[unruhjonny]

what radio do you have?

is it a factory radio?

if so, is it a single speaker radio - or a dual speaker radio?

[78w72]

Originally Posted by necdb3

No!!!! You cannot just add a jumper from your other speaker. It will cut the resistance in half and burn your amp out.

Thats only if the speakers are connected in parallel that the ohms are dropped, when connected in series the ohms are doubled, if he has original 10 ohm speakers, series connection with a jumper wire will come out to 20 ohms, in parallel will be 5ohms. If using modern car speakers @ 4ohms connected in series will get to 8 which is very close to the original 10 ohm design. For lower to medium volume listening 8 ohms shouldnt damage the amp, running too low of ohm speakers creates heat that will eventually damage the amp, usually from higher volumes or prolonged use at higher volumes. But its best to keep everything at the proper ohms.

You can also add the right sized resistor to the speakers if needed to get closer to the desired ohm rating of the amp, but that will effect the higher freq response some.

If the car isnt 100% original, its probably best to get a later year factory 2 channel stereo radio than trying to add a speaker to a single channel radio. Or look into the modern 2 knob radios that will fit the dash but have higher power for modern 4ohm speakers, most have aux inputs or bluetooth if you care about that.

Diagram shows series connection to double ohms. Parallel connection to drop ohms in half is when you run the +wire from the amp to both + on 2 speakers & both - on 2 speakers in parallel like train tracks.

[70TA-RAIII]

Good summary!

[grd777]

Originally Posted by unruhjonny

what radio do you have?

is it a factory radio?

if so, is it a single speaker radio - or a dual speaker radio?

i have a original 1972 factory radio and speaker, not sure if it is a dual speaker radio . how can i tell

[78w72]

Pretty sure 1972 fm radios were mono, or at least if the car only had 1 rear speaker it wasnt a dual speaker radio.

You can add another speaker using a jumper in series as shown above, but it will be mono, not stereo.

if you want true stereo sound with 2 rear speakers, its probably easier or better for sound to get a later 70's stereo radio, or one of the modern radios that will still fit the stock dash... they will sound much better, the 70's GM delco stereo radios sounded pretty crappy by todays standards.

[unruhjonny]

assuming you no longer have the label, and it is not the factory installed;
the plug in will denote which one it is - one only has a single speaker output, the other has two.

if it’s the factory original, then it’s safe to assume that it’s a single speaker.

the single speaker setup was standard (when ordering a radio), unless either the “rear speaker” option was ordered.

I believe that generally the factory 8-track player cars used the “mono” radio, but I understand that sometimes this wasn’t the case.

[bhill86]

Not sure about earlier cars but since the radio / 8 track setup was the same 70-77 I would think the same offerings would be available throughout that time. Feel free to correct me if I’m wrong.

In 77 at least there was available:

A single (front) speaker mono radio, AM only or AM/FM;

A dual speaker (one front, one rear) AM only, AM/FM mono or AM/FM Stereo;

A dual speaker (one front, one rear) AM or AM/FM mono radio paired with a stereo console mounted 8 track and;

A dual speaker (one front, one rear) AM/FM Stereo radio paired with stereo console mounted 8 track player.

I’m not aware of there ever being a rear speaker-only setup in the firebirds. Single speaker setups would have one speaker in the center of the dash and dual speaker would add the package tray speakers.

If you do have the front and rear speakers the easiest way to tell if you have a stereo units vs mono is the FM dial will have a red dot in the center that illuminates when a stereo frequency (station) is tuned in.

All that said, one way you could accomplish what you want is to install a small amp that drives modern speakers. I say modern in the sense that the 70-77 radios use a common ground speaker setup. Although the rear speaker does have a dedicated ground to it it’s not in the same sense as modern speakers. The front speaker for example only has one wire to it. It’s grounded through its bracket.

Anyway, this sounds more complicated than it is but what you can do is run your original speaker outputs into a line output converter which reduces the signal to line level. From there, connect the two outputs from that to a small amp using RCA jacks. The amp I used has 4 inputs. LF, RF, LR, and RR. I took the left and right channel outputs from the converter and split them using a Y splitter so the left channel fed the “left front and left rear” channels of the amp and the right channel converter output split with a Y into the “right front and right rear” amp inputs. From there, wire your new speakers into the amp like you would. The amp now takes over driving the speakers so you can use modern 4 ohm speakers with the standard positive and negative leads.

Of course if your radio is mono you’ll only get mono output from all 4 speakers (4 speakers assuming you replace the center front with a dual voice coil stereo speaker)

If you have a stereo radio, you will now have switched the stereo split between the factory front and rear speakers to left and right.

I have this basic setup on my 77 except the amp I used is Bluetooth enabled with a wired remote I can use to stream and control music from my phone. One touch of the source button on the remote and the amp switches over to its analog input and my factory stereo and console 8 track players function as they should.

Lot of info, sorry. Any questions ask. I’d be happy to try to help.

[78w72]

Correct, there wasnt a rear speaker only option, I should have mentioned the dash speaker but assumed it was a given since its standard on all the radio options listed I think.

I have a base model 72 firebird that only had a single rear speaker and the dash speaker, but Im pretty sure there is a factory cutout in the rear deck plate for the 2nd speaker, I will have to check since I plan to use dual rear 6x9 speakers and one of the dual 4" dash speaker plates that mount in the single dash opening for a stereo hook up along with a retro sound brand 4 channel 2 knob radio.

[bhill86]

My 77 does have the second speaker cutout in the package tray so I’d imagine your 72 might too.

[unruhjonny]

I do see a typo in my last post (which I would fix now if that was an option) but I do not see that I suggested a single rear speaker was ever a thing;
Hopefully no one took tat from my reply.

As mentioned, a single rear speaker never was a thing;
For single speaker cars, the front dash location was used.
For two-speaker cars, the front dash and rear left (drivers side) speaker locations were used.

Even though the metal structure of the rear dash was made to accommodate dual rear speakers, for 70-77 Firebirds at least, the right speaker location was occupied more or less with the spare tire or jack.

[bhill86]

I think this is what caught me “ if it’s the factory original, then it’s safe to assume that it’s a single speaker” since he asked about adding a second rear speaker meaning he already had one rear. No harm intended and truth be told I’m a bit sleep deprived at the moment so that could be my fault lol.

[necdb3]

Originally Posted by 78w72

Thats only if the speakers are connected in parallel that the ohms are dropped, when connected in series the ohms are doubled, if he has original 10 ohm speakers, series connection with a jumper wire will come out to 20 ohms, in parallel will be 5ohms. If using modern car speakers @ 4ohms connected in series will get to 8 which is very close to the original 10 ohm design. For lower to medium volume listening 8 ohms shouldnt damage the amp, running too low of ohm speakers creates heat that will eventually damage the amp, usually from higher volumes or prolonged use at higher volumes. But its best to keep everything at the proper ohms.

You can also add the right sized resistor to the speakers if needed to get closer to the desired ohm rating of the amp, but that will effect the higher freq response some.

If the car isnt 100% original, its probably best to get a later year factory 2 channel stereo radio than trying to add a speaker to a single channel radio. Or look into the modern 2 knob radios that will fit the dash but have higher power for modern 4ohm speakers, most have aux inputs or bluetooth if you care about that.

Diagram shows series connection to double ohms. Parallel connection to drop ohms in half is when you run the +wire from the amp to both + on 2 speakers & both - on 2 speakers in parallel like train tracks.

You are correct but is it any better to connect them in series? Now you have twice the ohms. Either way, it may work but it will be very short lived.

[Ramairnacho]

I'm no expert but original speakers and radio are touchy. Meaning not upgrading radio to handle the second rear will break radio. The ohm going to second speaker will probably burn out original unit. I would have it digitized but having stock appearance with rca jack blue tooth ect. Tuck a small Amp for 6 x 9 s and have the speakers modernized too. I personally am trying to figure out if stock square speakers can be updated to modern more durable speaker material and better ohms. I had a 1973 4 speed formula with a nice Kenwood pull out, modern infinity 6 x 9 's in baffles and 2 free air 12 inch woofers behind the seat using trunk as speaker box. It sounded good but again wasn't stock. In my opinion stock sound quality probably isn't that good without doing some upgrading.

[78w72]

Originally Posted by necdb3

You are correct but is it any better to connect them in series? Now you have twice the ohms. Either way, it may work but it will be very short lived.

Ohms are a often misunderstood concept, yes its better to have more ohms when talking about amplifiers that arent rated for lower ohms. Ohms are a unit of resistance and speakers need to match the rating of the amp, in this case lowering ohms in a parallel connection has less resistance and will draw more power from the amp making it run hotter, that excessive heat is what will eventually damage electrical parts of the amp, usually the output drivers/transistors. Increasing ohms with series connection raises resistance which will draw less power from the amp & make it run cooler, will have less power/volume but will last longer, ideally you want the speaker ohm matched to the amp to run as designed.

As a teenager, even though I knew the basics of ohms & electronics, many times i ran aftermarket speakers on factory radios, the 1980-81 digital tuner stereo radios actually sounded decent on a set of 4 ohm 6x9 speakers, i ran that for a few years & didnt damage the amp in the radio... but then again I did a lot of stupid things as a kid! When car audio got more popular in the 1990s-2000s, i did some tricks with the subs where you wire in parallel to drop the ohms, that would increase the power of the amp which meant more volume, some aftermarket amps are designed to be 2 ohm stable, some high dollar amps could be ran at 1 ohm or even .5 ohms for real high power. You can play with lower ohms for a short time, the radio/amp wont blow up instantly, or at least it shouldnt if its in good condition, just dont play it too loud or run it that way for too long. After market is best option these days for better sound or as mentioned connect a secondary amp to the stock radio speaker outputs.

Originally Posted by Ramairnacho

I'm no expert but original speakers and radio are touchy. Meaning not upgrading radio to handle the second rear will break radio. The ohm going to second speaker will probably burn out original unit. I would have it digitized but having stock appearance with rca jack blue tooth ect. Tuck a small Amp for 6 x 9 s and have the speakers modernized too. I personally am trying to figure out if stock square speakers can be updated to modern more durable speaker material and better ohms. I had a 1973 4 speed formula with a nice Kenwood pull out, modern infinity 6 x 9 's in baffles and 2 free air 12 inch woofers behind the seat using trunk as speaker box. It sounded good but again wasn't stock. In my opinion stock sound quality probably isn't that good without doing some upgrading.

Adding a 2nd rear speaker will not "break radio" or burn out original unit IF the 2nd speaker is connected in series as mentioned above, it will actually increase the ohms and lower the strain on the amp, if anything will prolong the radios life since its running cooler at less power.

Stock square speakers? Stock speakers are 6x9 oval shaped in teh rear and a 4x10 oval in the front, probably cant update stock speakers in a cost effective way compared to buying new speakers that match the ohm of the radio being used. Theres a couple companies that make retro looking 2 knob radios that have all the modern features and higher power for modern speakers. If one wants to keep the stock radio it can be updated for aux or bluetooth, probably have the amp section updated too but that will probably cost more than one of the modern retro radios.

I had many car systems back in the 90's, had a couple of those "pull out" radios too, they were a neat invention to avoid theft... but those radios & the new at the time CD radios are responsible for all the cut out dashes we have today. I liked the pull off face plate radios better than the big pull out units.

In my 78 t/a in the 90's, I had pretty big systems in my car i built myself, dual 12" competition level subs connected in parallel with a big amp bridged to one channel at 2 ohms, ~500 quality watts, top of the line alpine 6x9s running at 100 watts each, 4" speakers in the front lower console as i didnt want to cut up the door panels, and a set of 1" dome tweeters velcro'd to the upper A-pillars. That system sounded better than many high dollar home set ups, it could play at the big boomy levels you hear the kids doing today with rap music, where you can feel it before you can see the car, but luckily I had better taste in music and didnt do that obnoxious stuff.

My other hobbies since I was a teenager besides pontiacs are home audio/theater and car audio, ive built some pretty impressive systems over the years, even been dabbling in repairing vintage home audio stuff lately, have learned a lot but there is so much more involved with electronics that requires a real education to understand it all.

Sorry for the long post, hope some of that info helps the OP & others.

[necdb3]

78w72, I understand Ohms law well. Just saying those old amplifiers don't like deviation. They even have a hard time when someone replaces a 10 ohm speaker with an 8 ohm.

GRD77, Best bet would be to send the radio out and have modern electronics put in it. Just tell them the speaker setup you intend to use. It will still be you original radio with modern internals. That way you can insure yourself a great sounding radio for the long haul.

[Ramairnacho]

Originally Posted by 78w72

Ohms are a often misunderstood concept, yes its better to have more ohms when talking about amplifiers that arent rated for lower ohms. Ohms are a unit of resistance and speakers need to match the rating of the amp, in this case lowering ohms in a parallel connection has less resistance and will draw more power from the amp making it run hotter, that excessive heat is what will eventually damage electrical parts of the amp, usually the output drivers/transistors. Increasing ohms with series connection raises resistance which will draw less power from the amp & make it run cooler, will have less power/volume but will last longer, ideally you want the speaker ohm matched to the amp to run as designed.

As a teenager, even though I knew the basics of ohms & electronics, many times i ran aftermarket speakers on factory radios, the 1980-81 digital tuner stereo radios actually sounded decent on a set of 4 ohm 6x9 speakers, i ran that for a few years & didnt damage the amp in the radio... but then again I did a lot of stupid things as a kid! When car audio got more popular in the 1990s-2000s, i did some tricks with the subs where you wire in parallel to drop the ohms, that would increase the power of the amp which meant more volume, some aftermarket amps are designed to be 2 ohm stable, some high dollar amps could be ran at 1 ohm or even .5 ohms for real high power. You can play with lower ohms for a short time, the radio/amp wont blow up instantly, or at least it shouldnt if its in good condition, just dont play it too loud or run it that way for too long. After market is best option these days for better sound or as mentioned connect a secondary amp to the stock radio speaker outputs.



Adding a 2nd rear speaker will not "break radio" or burn out original unit IF the 2nd speaker is connected in series as mentioned above, it will actually increase the ohms and lower the strain on the amp, if anything will prolong the radios life since its running cooler at less power.

Stock square speakers? Stock speakers are 6x9 oval shaped in teh rear and a 4x10 oval in the front, probably cant update stock speakers in a cost effective way compared to buying new speakers that match the ohm of the radio being used. Theres a couple companies that make retro looking 2 knob radios that have all the modern features and higher power for modern speakers. If one wants to keep the stock radio it can be updated for aux or bluetooth, probably have the amp section updated too but that will probably cost more than one of the modern retro radios.

I had many car systems back in the 90's, had a couple of those "pull out" radios too, they were a neat invention to avoid theft... but those radios & the new at the time CD radios are responsible for all the cut out dashes we have today. I liked the pull off face plate radios better than the big pull out units.

In my 78 t/a in the 90's, I had pretty big systems in my car i built myself, dual 12" competition level subs connected in parallel with a big amp bridged to one channel at 2 ohms, ~500 quality watts, top of the line alpine 6x9s running at 100 watts each, 4" speakers in the front lower console as i didnt want to cut up the door panels, and a set of 1" dome tweeters velcro'd to the upper A-pillars. That system sounded better than many high dollar home set ups, it could play at the big boomy levels you hear the kids doing today with rap music, where you can feel it before you can see the car, but luckily I had better taste in music and didnt do that obnoxious stuff.

My other hobbies since I was a teenager besides pontiacs are home audio/theater and car audio, ive built some pretty impressive systems over the years, even been dabbling in repairing vintage home audio stuff lately, have learned a lot but there is so much more involved with electronics that requires a real education to understand it all.

Sorry for the long post, hope some of that info helps the OP & others.

The stock speakers have square magnets so I call them square speakers. And a while ago while shopping for an oem red dot am fm I was told that if I install more speakers than designed originally to a stock am fm radio,it will not last and that it only had 2 speakers 1 in front and 1 in back. That reason I suggested upgrading internals. I'm no expert on stock.stuff just trying to help

[78w72]

Originally Posted by necdb3

78w72, I understand Ohms law well. Just saying those old amplifiers don't like deviation. They even have a hard time when someone replaces a 10 ohm speaker with an 8 ohm.

GRD77, Best bet would be to send the radio out and have modern electronics put in it. Just tell them the speaker setup you intend to use. It will still be you original radio with modern internals. That way you can insure yourself a great sounding radio for the long haul.

Wasnt sure if you or others in the thread knew how ohms worked in audio situations so wanted to explain it somewhat. I havent used many pre 77 radios, but the later 78-81 stereo 3 & 4 channel radios were built pretty well & could handle some deviations in ohms, especially going higher.

I knew of countless factory radios back in the day with aftermarket 4 ohm speakers installed that lived long lives at high volumes, cant recall any dying. Maybe the earlier radio/amps werent built as robust to handle that? But for the OP's situation, connecting a 2nd rear speaker in series that will raise the ohms above the stock 10ohms should be perfectly safe for the radios amp, probably wont sound very good in mono with even less power going to each speaker though.

I agree there are other better options for radios in these cars, just saying raising the ohms should not damage the amp.