2700 ETR based system, was lost, now not so much

[Green79Scottsdale]

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I picked up this 2700 ETR radio for my truck a bit back. My plan is too replace the original mono center speaker and to add some 6x9's in the rear cab corners. During all this planning I am also trying to make it "easy" to add an amp to this setup if I deem it necessary.

For the front I am leaning towards Retrosounds 4x10... https://www.crutchfield.com/p_068D412UK/RetroSound-D-412UK-Dash-Speaker.html. It has to be better than my old factory speaker, right? Or I could do a pair of 3.5" or 4" 2-way speakers. Fabbing a mount should be cake. No clue on what speakers I would use. Probably whatever looks like the best bang-for-the-buck at the moment. Suggestions, links?

Rear speakers are the same thing. No clue, I am audio illiterate for the most part. I will be making my own mounts (at least that's the plan). Suggestions on speakers is welcome. Links and reasons why those particular ones is preferred.

As I said, I want to keep an eye on adding an amp to all this too. It is not a guarantee, but the option will be open. How easy is it to hook one up after the fact? I saw in my research mini-amps. Would one of them do alright? Small packaging sounds easier to mount, and thats good to me. Again, links?

I am not looking for some show-stopping system, just some decent pieces for the limited driving I do with the truck right now. And I did do research on everything, but my brain didn't take to the info very good, so I want more input on this. Before buying anything I am seriously thinking about swiping the 6x9's out of the SS and hooking this radio up to those and the mono speaker and see the results. Sorry for the long read, tia for your help. Again, the whys to your answers are what I am after.

 

[HotRodPC]

Whoa !!! Look who dropped in !!! @RetroC10Sport might be some help on this one.

 

[Green79Scottsdale]

I drop in more than you realize, I bet, I just usually don't post. I am in that middle ground where I don't need to actively research something for my truck, and when someone else posts a question, someone else has already given the answer I would have, so I just move on. And I don't have time to read the vast array of threads we have now.

But researching this radio stuff has my brain tied in knots. I have done a good amount of research, but I still am unsure and all my other car buddies know as much (little??) as I do. We can't hardly do a radio, but dammnit we can rebuild an engine!

 

[1987 GMC Jimmy]

Just a few thoughts... Nice radio, by the way! Congrats. I just acquired a rebuildable core 2700 ETR, and I have two mechanical 2700s w/cassette (one working and in a box, the other not working and in the truck - ironic). I’ve done something ideologically similar to what you’re thinking with the Delco 2000 ETR in my Caprice. I’m running 4” two way speakers in the 4x10 corner holes, and I’m running 6.5” two way speakers in the 6x9 rear deck holes. The big thing to concern yourself with that this post kind of reminds me of is impedance matching. Modern speakers place a pretty considerable load on a radio that was designed to work with 8 ohm speakers, and when I listen to music on mine, I know I need an amp. The easiest way to achieve this is with a 4 ohm four speaker setup on a good two channel amp with two wired in series per channel to fool the radio into thinking you’re running higher resistance, old timey speakers. You could probably do two 2 ohm dash corner speakers and a 4 ohm center speaker on one channel and two 4 ohm speakers on the rear channel to have a five speaker setup, which is what I want explore for the Jimmy whenever the day comes that I can work on the finer things. You’ll also need a line output converter to match the factory line level outputs on the 2700 to the RCA jacks on the amp. So you asked if the center 4x10 was better than your factory monaural speaker. Yes, it’s better on your ears than an old speaker with cones that have more or less turned to jelly, but no, the resistance parameters will prevent you from cranking up the radio a bunch, and it does put a strain on the radio that you can see on by the dimming of the display whenever it hits a heavy note.

As far as brands go, I would tell Crutchfield customer support what you’re trying to do and see what they suggest. I hear good things about them, and I’ve done business with them with good results. This kind of kit a fire under me to do an amp in my car for matching impedance if nothing else. Hopefully I can net an output boost, as well. The safest thing for the radio’s health and longevity without running an amp or doing some kind of Aurora conversion to the innards is to run higher impedance speakers that can agree with the radio. I hope others chime in, but this outlines what I think I know about speakers wired to older factory stereos.

I’d do the largest possible speaker combo. 4” in the dash if you can mod it and whatever the largest feasible speakers for the rear pillars are. People say that circular cones are better than oval cones, but you know people. Either way, that’s created an innate bias for me when I look into speakers. If 6x9s are the biggest possible, I’d run with it, but if there’s a chance of doing 5” or 6.5” speakers, that’s what I’d do. I need to do more research on this part, as I don’t know what these trucks are fully capable of in terms of speaker mods.

https://cie-wc.edu/Series_Parallel_9_14.pdf

https://www.crutchfield.com/S-ADP1Bh1IPgd/learn/what-are-line-output-converters.html

 

[bluex]

Just a few thoughts... Nice radio, by the way! Congrats. I just acquired a rebuildable core 2700 ETR, and I have two mechanical 2700s w/cassette (one working and in a box, the other not working and in the truck - ironic).

I have a 2700 ETR I need to have checked out. Who do you send yours too?

 

[Snoots]

I'd go with this for the front . . .

https://www.classiccarstereos.com/dual-dash-mount-speaker-30-watts.html

They also have other high-wattage units for more $$.

 

[Snoots]

I have a 2700 ETR I need to have checked out. Who do you send yours too?

I've used these guys with GREAT results . . .

http://www.hunt-radio.com/default.aspx

and you can check out these folks . . .

http://www.mnrelectronics.com/

 

[bucket]

In my '77, I put two 4 inch speakers in the center dash opening. It was very easy. I bolted the two speakers together and then bolted them into the dash, no brackets needed.

 

[SDJunkMan]

I'd go with this for the front . . .

https://www.classiccarstereos.com/dual-dash-mount-speaker-30-watts.html

They also have other high-wattage units for more $$.

From that page:
If you have an original, 8 Ohm or 10 Ohm radio, this speaker will not work. You must use this speaker with radios designed for 4 ohm applications.

 

[Snoots]

I have no idea what output impedance the 2700 ETR Series radios have.

 

[1987 GMC Jimmy]

I have no idea what output impedance the 2700 ETR Series radios have.

8 ohm, I believe.

 

[1987 GMC Jimmy]

I have a 2700 ETR I need to have checked out. Who do you send yours too?

I planned to crack mine open and see if I could figure it out, but if not, I’ve used Factory Car Stereo Repair, Inc. in Longwood, FL. They work on 2000 and 2700 ETRs.

 

[Green79Scottsdale]

I read your post this morning and had a chance to quick go through the links before work. So that was rolling around in my head all day.

Just a few thoughts... Nice radio, by the way! Congrats.

Thanks. It took a while of looking. $75 for the radio and the rear speaker harness. Guy had the radio hooked up and working when I arrived. The only thing "wrong" is the treble knob is missing.

The big thing to concern yourself with that this post kind of reminds me of is impedance matching. Modern speakers place a pretty considerable load on a radio that was designed to work with 8 ohm speakers, and when I listen to music on mine, I know I need an amp. The easiest way to achieve this is with a 4 ohm four speaker setup on a good two channel amp with two wired in series per channel to fool the radio into thinking you’re running higher resistance, old timey speakers. You could probably do two 2 ohm dash corner speakers and a 4 ohm center speaker on one channel and two 4 ohm speakers on the rear channel to have a five speaker setup, which is what I want explore for the Jimmy whenever the day comes that I can work on the finer things. You’ll also need a line output converter to match the factory line level outputs on the 2700 to the RCA jacks on the amp.

I’d do the largest possible speaker combo. 4” in the dash if you can mod it and whatever the largest feasible speakers for the rear pillars are. People say that circular cones are better than oval cones, but you know people. Either way, that’s created an innate bias for me when I look into speakers. If 6x9s are the biggest possible, I’d run with it, but if there’s a chance of doing 5” or 6.5” speakers, that’s what I’d do. I need to do more research on this part, as I don’t know what these trucks are fully capable of in terms of speaker mods.

Okay, I understand the concept of running x2 4 ohm speakers run in parallel to equal a single 8 ohm speaker. I also understand the two channel amp to power the speakers you mentioned. But why not a four channel? Wouldn't you lose fade functions with a two channel?

What about doing something like running a pair of 5" or 6 1/2" speakers in each corner to create the 8 ohm impedance, with no amp? That would be four total for rear speakers... not sure what possibilities there could be in the front. My truck is a '79, so I would have to do some cutting to get speakers in the corners. Then it comes to the possibility of still wanting an amp after all that. I see a rabbit hole...

In my '77, I put two 4 inch speakers in the center dash opening. It was very easy. I bolted the two speakers together and then bolted them into the dash, no brackets needed.

That is good to know 4"ers fit! Thanks!

 

[1987 GMC Jimmy]

The two channel amp was the easiest way for me to visualize what was going on. I haven’t thought much about the four channel amp and what it would take to achieve the same impedance matching if it’s possible, but if there’s a way to do that, I would go that route for obvious reasons, one of which you pointed out. I’m not sure if there is, though, because I thought those were intended for one speaker per channel, or if you needed more than four speakers you could wire in parallel to match impedance using 4 ohm speakers and a 4 ohm HU. Personally, I wouldn’t lump speakers together back there. I like to maintain at least a close to factory look, even if the items in question are mostly hidden. From my experience, I would rather go back and do the amp proactively instead of reactively. I don’t think I’ve damaged my HU by running 4 ohm speakers because I have it EQ’d down from max treble and bass, and I don’t let the volume go past the point where distortion occurs, but I’m not 100% on what’s happened. I was so frustrated with working on the radio harness that I just wanted to get it in there and call it. The PO had two aftermarket stereos after the original, and all three harnesses were piled one on top of the other. What a pain to yank all that out, identify what I needed, and redo it. As you have seen, there isn’t a wealth of information on 1977-93 GM radios. With the front speakers, you could lump the two small speakers together in the center hole to avoid cutting.

 

[bucket]

In the past, I've run many aftermarket speakers with original Delco ETR units. The difference in ohms never seemed to be a problem?