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Need help with Stereo and Speakers

Started by Jeff Rosansky CLC #28373, February 18, 2014, 09:18:05 AM

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Jeff Rosansky CLC #28373

I have learned enough over the years to admit what I don't know and try to seek advice.  Well I admit I don't know much about speakers, ohms,etc.....I need help from those who really know radios and speakers.
I have located a radio for our 70 Deville.  It will be a stereo which is what she came with. 
My question is on the speakers. I have read that they need to be 8 ohm speakers for the front but have no info for the rear speaker. 
Here is where I get confused.  I admit that I really know nothing about speaker resistance, how much is needed, etc.  What size speaker is needed for the rear.  What if I want to put 2 speakers in the rear?  Can I get a 4ohm speaker for say the left front and just splice in and have another 4 ohm speaker for the left rear giving me a total of 8 ohms?  If I do this, do I need to have anything hooked to the line for the rear speaker or can I just leave it unconnected and just run all 4 speakers on the front channel without hurting anything?  Would it be best to just splice into the rear channel and just put 2 4ohm speakers in the rear?  I realize if I splice and run 2 rear speakers off the one line that it will not be in stereo but that will be OK.  It also appears that there are 2 wires going to the front speakers so they ground by the wire but the rear speaker just has 1 line so does it just ground to the car's frame?
I realize this will not give me sound like I am listening to the Boston Symphony but I would like decent sound with 4 speakers out of this and I might as well do it now while I have everything open.
Thanks in advance,
Jeff
St. Louis
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Aprules2

How many outputs does the radio actually have?

TJ Hopland

Im not real clear on what you are asking or trying to do so here is just some general info:

It was common in factory radios in cars to use a common ground for the speakers.  Just the + wire would go between the radio and speaker.  Minus at the speaker was then hooked to ground.   Some amplifier designs don't have a problem with doing this, others do.   Most instruction manuals will say if its ok to ground the minus terminals. 

As far as the ohms in the case of speakers its called impedance.   Like with resistors they can operate in series and or parallel.   Parallel is where everything is plus to plus to plus and minus to minus to minus.  Series would be amp plus to speaker plus.  That speaker minus to next speaker plus.  That speaker minus to amp minus.   2 8 ohm speakers parallel would give a 4 ohm load to the amp.  2 8 ohm speakers series would give the amp a 16 ohm load.  You can go higher impedance on an amp without direct damage to the amp.  You can't go lower than what its rated at without overloading it.   You get the most power out of an amp working closest to its minimum rating.   An example of a commercial amplifier's rating would be 225 watts at 8 ohms, 350 at 4, and 450 at 2 ohms.  So if you ended up with 2 in series thats a 16 ohm load on that amp you would have around 100 watts available so thats only 50 watts per speaker.  That could be a problem if you needed 100 watts per speaker to make your spec.  In that case you would be better off to go to parallel which would then get you 175 per speaker.   More amp power is almost always better than to little.   What you want to avoid is clipping which is where the amp reaches its maximum power and sends straight DC power to the speaker.  The amps can usually tolerate that but the speakers really don't like it.   Being a little off on the impedance usually won't hurt anything if you are not pushing things hard.     
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Aprules2

I agree 100% with TJ.
Please tell us exactly what radio you are hooking up, how many outputs it has, how many speakers you intend to install, and if you can find out what your maximum impedance is on your radio?


Jeff Rosansky CLC #28373

OK, sorry for not being clear. 
70 Deville stereo.  I found one that I hope to get soon.  I have not seen it yet so I didn't want to be specific but let me tell you about the radio I am replacing...... It has 2 front and 2 rear speakers.  The front speakers each have 2 wires going to them but the rear speakers only have 1 wire each so I assume they ground to the frame.
There were no rear speakers in the car when I got it and the rear speaker wires were disconnected from the stereo so having to use the wiring diagram to figure what is what which is interesting because the wire colors are not the same.
What I really want to know about is the speakers.  I do not know what kind of speakers the car had and have not been able to figure that out.  I have read that they are 8ohm speakers but I am not sure and if so, I don't know if all 4 are 8's or not. 
Not sure how many watts the stereo is and I don't know what kind of speakers to get.  I kind of have to keep the costs down (wife).
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

TJ Hopland

#5
Another thought that popped into my head is that most of the factory radios had unique plugs on them that are not easily duplicated or modified so if your original harness and plug is gone you will want to try and get at least part of the correct harness that goes with your replacement radio to make the install easier.   I seem to remember a lot of the plugs looked similar but when it came down to it there were subtle differences between models or options that made them not easily interchange.  I think later 70's and early 80 GM kinda had a standard between most of the models and makes as far as the plugs but in the mid 80's they got away from that again.

Quote from: George K Hashem on February 19, 2014, 08:46:46 PM
If you get the wrong speakers you will destroy  the radio.

That is just not true as a blanket statement. 

It is true that a miss match can make things work less efficiently and if you then pushed the system hard it could stress things including the radio which could shorten its life.   The way most of us on this forum use our radios and given the era in question I really doubt a slight miss match will cause issues.   I don't think many of us are entering our cars in the decibel drag races any time soon.  It sounds like the original poster has a kinda of hacked up system and is looking for something closer to stock but not looking to spend the bucks for reproduction show quality stuff.

What can destroy a radio is what I mentioned above about the speaker line being grounded.  If you had a radio who's amplifier was not designed to have a speaker line grounded and you ground it you are not going to have a happy amp.   Tube amplifiers usually didn't have a problem being grounded because by nature they had transformer outputs and the transformer isolates things.   I am assuming because the transformers make it possible to do it they did it just to save the extra piece of wire.  I would GUESS that most of the factory radios especially in the 70's era won't have a problem with a grounded speaker but if that is the way the car is set up and you don't want to change it I think I would want to verify the model car the radio in question was intended for and check the diagrams for that car to make sure it too used a grounded speaker.

Speakers them selves don't care about the ground unless its a unique design were both terminals are not isolated on the speaker itself.    It seems to me that many of the factory speakers that were grounded you could see a little jumper wire from the terminal block to the frame of the speaker.    If you have a typical speaker both terminals will be isolated so if you want to used it grounded you just run a wire from one terminal to a good ground.

I have not looked at aftermarket speakers lately but 20 years ago they tended to be physically deeper than most stock ones which could cause fit issues in some places.   This may be a reason to look at something more along the lines of a reproduction speaker.

20 years ago you could still get a fairly efficient speaker that sounded good for a decent price, today I suspect that could be more difficult since power and processing is cheap.  This means that no longer do they have to actually design a good speaker that does not take a lot of power to work, they can just throw more power at it and if it does not sound right they can hit it with some digital processing to compensate.    A stock radio from the 70's may not even be 5 watts.  Hook that to a modern speaker that may need 200 watts to reach a decent output level and  I would not expect much sound and that may be an example of a big enough miss match to make Georges statement more true which again makes maybe looking at a reproduction speaker possible a better option. 

Like I said its been 20 years since I have looked close at aftermarket stuff so I could be totally wrong and there is some stuff that will work but my guess is your best option will be to look for something closer to original.  If a Cad reproduction piece is not available or too much money I suspect once you know the size you can cruise the sites for some of the more popular to restore cars of the era and find something that fits well and sounds decent for a price that works for you.    Its amazing what is out there for cars like Mustangs and alike.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Jeff Moffo

Ask for Greg at www.turnswitch.com.  The guy knows his stuff!!
Jeff
Jeff M
North Jersey
Best of all, it's a Cadillac....
'76 Coupe DeVille - Claret (Sold)
'73 Series 60 Fleetwood (Sold)
'76 Coupe DeVille-Dunbarton Green

Jeff Rosansky CLC #28373

Thanks guys.  That's pretty much what I thought but wanted to confirm with everyone.  I wanted to get a little fancier of a speaker than the stock stuff but they are all 4ohm.  So, I'll stick with the 8's.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Jeff Moffo

Jeff,
I have used Greg at turnswitch a lot as I have a 1976 Coupe that needed its entire radio and speakers overhauled.  I am not sure WHAT the previous owner did.  However, after the radio was sent out for restoration, I found the front speakers were no longer any good.  And the rear (like yours) were totally dead.  Greg explained what was happening and the nuances of the radios/speakers that GM made back in the early 70's.
You will not be disappointed.  He is very friendly and knowledgeable.  His speakers arrived in two days without any issues and came with detailed instructions for installation and correct use.
Don't be fooled by the people that claim the new 4 ohm speakers work.
Regards,
Jeff in NJ
Jeff M
North Jersey
Best of all, it's a Cadillac....
'76 Coupe DeVille - Claret (Sold)
'73 Series 60 Fleetwood (Sold)
'76 Coupe DeVille-Dunbarton Green

76eldo

#9
If you are using a stock 1970 radio, you need to get 8 ohm speakers.

If the radio plugs in the dash harness have been cut, you need to get some plugs with tails on them to splice in. There is an ebay seller "themrgrandprix" who sells radio to 8 track harnesses. I am sure he could supply a plug with the right color wires on it for you of you need that.

I'm surprised that 8 ohm speakers are hard to come by. I'm going to need some for some of my cars.

Is it possible to add a resistor in series to the positive side of a 4 ohm speaker to increase load or will that just reduce the volume output?

I just did a Google search for " 8 ohm car speakers" and here is just one link of many that came up:

http://www.onlinecarstereo.com/products/15/Car_Speakers/Full_Range_Car_Speakers.aspx?NS=Impedance|8

If you replace any of the speakers, I would do them in pairs.  As far as the source of the ground connection, I don't think it matters if it grounded through a wire back to the radio or grounded to the body.  All grounds in the car are common to each other.


Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

TJ Hopland

It is possible to add a resistor in series with a speaker or even another speaker in series to raise the impedance.    This does get around the issue of minimum impedance but you are doubling the load because the resistor will consume as much power as the speaker.   The extra load is going to be the lesser of the two evils but still not ideal.   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

TJ Hopland

Looking at the car stereo world reminds me why I always tried to avoid it, the laws of physics apparently don't apply. 

I did a quick look at some of the more popular current 'car stereo places' and see what appears to be a typical 6x9 car speaker these days and I would agree that hooking those up to a 70's era stock radio would not likely yield good results.   When I was tinkering with car stereos there were all sorts of impedance stuff out there like 6 ohm 10 ohm.  There was even more strange stuff if you started looking at the OE stuff in cars.   My statement about being close being close enough was based on what I assumed was still fairly easily available stuff.   Looks like that stuff much harder to find now.  If you are happy with the blanket statement of 4 ohm will break your radio then I will say I agree and you can stop reading.   If you want to know why I now agree with this read on......

-------------------------------------------------------------------------------------------------------------------------------------------------------------------------

A typical inexpensive ($100?) speaker now seems to be at least a 2 way and saw some that even say they are a 5 way?   I would like to see some real data on that design.  I also see that 200watts appears to kinda be a minimum rating these days.  I did not look real hard but was not able to easily find enough details on this rating to actually have it mean anything so its all guessing.

Looking at a few examples where I was able to dig up some vague specifications I find sensitivities in the 88-92 db range, this is the problem.   

Sensitivity is an important factor.  Put simply it is how loud is it at a given power input level.   As I said they seem to leave a lot of details out of their specs but we will assume they are sticking to the typical standards, if they are not it just makes them look better.   So typically sensitivity is given at 1 watt 1 meter.   1 watt of power input and measured at a distance of 1 meter.   

What sort of input signal you say?  Bach?  Meggadeath?  Larry King?  Full band pink noise?   1000 hz test tone?   This is an area you can cheat on your specs because you can sort of leave that detail out or bury those details in a footnote somewhere.   

Anyway with one watt of power lets say we are in the middle of the range I found at 90db.  80-85 db is normal traffic noises so in a nice quiet car with no one talking you are good to go if you don't need it 'loud'.  So you want it louder?  It takes about a 3db gain for most people to say its louder.  Just need more watts so we turn it up.  This is where the power handling comes in and this is also where some of those darn physics laws and math comes in.   The inverse square law.  If you are really curious you can look it up and do the math but to grossly simplify things its an exponential thing, to make it slightly louder you need to double the power, so using our example we were at 90db 1 watt,  at 2 watts we are 93.  So far so good.  We want 96 we need 8 watts (this is likey the point we just exceeded the capacity of a 70's radio, and we are no yet even close to windows down or top down levels).  We want 99 we need 50 watts, 102 need 150 watts.   Those numbers are not actually using the real formulas, I'm way to lazy and bad at math to do it just for fun but they are not that far off.  You see how quickly things grow.  The example speaker having a capacity of 200 watts means its going to max out at around 105db which is not really that loud.    IF we only have a 5 watt factory radio to feed it we maxed out at just over normal traffic levels.   This is why back when power was expensive they made better speakers. 

If we start out with a speaker with 100db sensitivity we are that much further ahead to start with.   I would bet the 70 OE speakers were in the 100-105 range.   The typical charts put a chainsaw at 100db, rock contert 110db, jet 130db so you can see where having a 5 watt amp and a 100 db speaker is a good setup that gives you some range.    If you are using a speaker with a 90db sensitivity it better have a 500 watt capacity and you are going to need to feed it that to get levels out of it.                   
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

Jeff Rosansky CLC #28373

I went ahead and got a full set at turnswitch. 
At first I hoped I could find a way to use the 4 ohm jobs with resistors,etc but decided against it.  I figured if I was going to go to all the trouble to get a factory radio, I mite as well not blow it up.
I pulled the old dead one months ago figuring I would just get another at a local salvage yard along with a full set of speakers for $50 or so........That's what I did when I was a kid and put in that nice,fancy Kraco cassette.  Well, that did not work so easily and simply as I thought. 
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

76eldo

The 1970 radios are not that easy to find.  My 70 Deville has the deluxe signal seeking stereo radio.  One channel is out.  These were wired in such a way that the "left" channel is front left and right rear, and the "right" channel is right front and left rear.

Mine only plays through the front left and right rear.  I doubt that the speakers blew out that way, so I am assuming that the radio has a channel blown.  I don't live too far from Mike Hagan, a well known radio restorer.  I bought a beautiful radio from a low mileage car on ebay and brought it to him to test it.  It worked fine on the bench, so when it gets warm I will swap radios and I hope my speakers are good.

Mike told me that the output transistors that go bad are no longer available so he doesn't know if he would be able to fix my radio or not.  The output transistors are probably what blows if hooked up to a 4 ohm speaker so it's really important to have the right ones.

Let us know how it turns out.

Brian
Brian Rachlin
Huntingdon Valley, Pa
I prefer email's not PM's rachlin@comcast.net

1960 62 Series Conv with Factory Tri Power
1970 DeVille Conv
1970 Eldo
1970 Caribu (?) "The Cadmino"
1973 Eldorado Conv Pace Car
1976 Eldorado Conv
1980 Eldorado H & E Conv
1993 Allante with Hardtop (X2)
2008 DTS
2012 CTS Coupe
2017 XT
1956 Thunderbird
1966 Olds Toronado

Jeff Rosansky CLC #28373

That' what I thought..... not worth trashing a vintage radio just so save a few bucks.  That's why I went ahead and got the right speakers.  I don't want to take a chance but I wanted the opinion of others before I spent the $$.  Everything is in the hands of UPS now so hopefully I will have them in a few days and can work on it next weekend.
Jeff
Jeff Rosansky
CLC #28373
1970 Coupe DeVille (Big Red)
1955 Series 62 (Baby Blue)
Dad's new 1979 Coupe DeVille

Aprules2

I was a broke teenager in college when I had my previous 75. I didnt have the cash to spend on stereo equipment.  When I got the car I had one right rear speaker that worked and one left front that worked. A couple months later I lost the other rear speaker, and I thought the same thing probably a bad radio. I went ot the Junkyard hoping to find another Delco Radio. I ended up not finding one but bought speakers anyway, hoping to find a radio at a later date.  I got home and popped in the junkyard speakers and the thing played great. I used stock speakers out of a 2003 or 2004 Malibu they cost me next to nothing and were 6x9. They are 8 ohms and the stock Delco radio powered them well and they sounded nice. The 3.5 inch fronts I found in a 70s or early 80s lesabre and they worked good too.

A few years later I got bored and decided I wanted it to look stock but sound better. I found a small 4 channel Alpine amp and mounted it under the front seat, then mounted an equalizer in the glove compartment, and used HiLo converters to step down the sound from the stock Delco radio to a signal the equalizer could use then ran that into the amp. At the time AudioBahn was still well made, so I installed their 4 way 3.5s and 3 way 6x9's. The radio sounded absolutely awesome, the equalizer had a port for my Ipod, and everything looked bone stock.