Rear speakers for 86.5 cars (8 speaker systems)
01-02-2020, 07:59 PM
#16
Rennlist Member
Thread Starter
That's it. And the documentation there answers a couple of questions.
First, the pinout I posted up there was accurate: It uses front and rear channels with separate grounds. There is also something in there saying to use isolated scopes when checking the power output, probably to keep the output from going to ground. Input *is* split with left and right channels using separate grounds common to front and rear but that kind of makes sense as since your speakers are supposed to be 180 degrees out of phase anyway, the ground wire will never be overloaded because while front speaker is at + voltage the rear one will be in a trough in negative and your ground will be neutral. This does mean if you have a quadrophonic head unit you might have problems, but that would be pretty damn schizophrenic music.
Anyway, this is probably moot for the din outputs as they are very low current and can probably share any rational ground. Which is the chassis anyway which is still bugging me. Hm.
Thoughts? I have to order a DIN 8 plug or two to build an adapter so this will take a few days to accomplish. I think the only way I could isolate the ground from frame would be to pull the + side from the din plug and the grounds from the speaker outputs. The amps on the head units are 4 20 watt op-amps, while the amp on the BQB80 seems to be 8 10 watt op-amps in a push pull configuration.
Maybe that's why the output grounds can never touch, that would wreck havoc on the amplifier with crosstalk and whatnot...
First, the pinout I posted up there was accurate: It uses front and rear channels with separate grounds. There is also something in there saying to use isolated scopes when checking the power output, probably to keep the output from going to ground. Input *is* split with left and right channels using separate grounds common to front and rear but that kind of makes sense as since your speakers are supposed to be 180 degrees out of phase anyway, the ground wire will never be overloaded because while front speaker is at + voltage the rear one will be in a trough in negative and your ground will be neutral. This does mean if you have a quadrophonic head unit you might have problems, but that would be pretty damn schizophrenic music.
Anyway, this is probably moot for the din outputs as they are very low current and can probably share any rational ground. Which is the chassis anyway which is still bugging me. Hm.
Thoughts? I have to order a DIN 8 plug or two to build an adapter so this will take a few days to accomplish. I think the only way I could isolate the ground from frame would be to pull the + side from the din plug and the grounds from the speaker outputs. The amps on the head units are 4 20 watt op-amps, while the amp on the BQB80 seems to be 8 10 watt op-amps in a push pull configuration.
Maybe that's why the output grounds can never touch, that would wreck havoc on the amplifier with crosstalk and whatnot...
01-12-2020, 02:16 PM
#17
Rennlist Member
Thread Starter
Ok! So after waiting a week or two for all the parts to come in I went outside and got to work.
First step was to take the Din plug with wires, cut it in half, and separate out the individual wires. For this particular one, the color code was as follows (figured out with an ohmmeter to the pins)
I was just going to crimp them to insulated male space plugs (the red ones for 20-22 gauge wire) but those ones from Home Depot are SAE and the ones in the car are metric, so I took the spade out of each plastic plug housing, turned it down on my grinder to fit the car's plugs, then put them back together and crimped the wire. Never dull, but I really didn't want to cut the car's harness.
With this I hooked everything up according to the BQB schematic, closed the doors, and powered on the radio.
WOW!
Sound is crystal clear. Not a hint of distortion in the base/midrange all the way up to 3/4 full volume which is way more loud than I want or need. Solid bass from the front Hans speakers with crystal clear tweeter highs, and a very deep base from the rear two earthquake speakers.Given that each channel is putting out 20 watts peak, I am *well* within the spec for the speakers and the wire to the speakers. Music sounds great, music from my Ipod touch through the bluetooth casette adapter sounds perfect, and I think I got it!
The root of the problem I think is matching the amplifier inputs to the head unit outputs. In this case I was trying to drive the amp's high bain input (300mv to 8v) with the output from the stereo's line output (which is probably 300mv to 2v). Thus the only way I would get appropriate volume is if I was most of the way to full on the head unit where distortion would creep in anyway. Likewise the 20w output from the stereo's amplifier is double what the bqb is trimmed to take (it looks like 10 watts is what comes out of the old head unit) so it was clipping right off the bat.
Going with the pre-amp input on the amplifier (300mv to 2v) was the right way to go and results in the amp doing all the work, the head unit sounding good, and life being normal.
Now I can say that the BQB80 is plenty of power for me, using the speakers I am using. The base is quite solid and distortion free and I can see both the earthquakes and Hans' speakers moving cleanly in their housings. I'm happy, and will run with this setup for the foreseeable future.
Thanks everyone for the thoughts and comments. The only thing I may want to do going forward is select the lower tweeter crossover if it's too bright, and maybe put some sort of filter in front of the earthquakes to ensure they are not trying to replicate high sounds. But that can wait for a bit, any thoughts on the latter type of filter (for the earthquakes)?
C
First step was to take the Din plug with wires, cut it in half, and separate out the individual wires. For this particular one, the color code was as follows (figured out with an ohmmeter to the pins)
- Yellow 4 left front
- Purple,7,left rear
- Brown,1,left ground
- Green,5,right front
- Blue,6,right rear
- Orange,3,right ground
I was just going to crimp them to insulated male space plugs (the red ones for 20-22 gauge wire) but those ones from Home Depot are SAE and the ones in the car are metric, so I took the spade out of each plastic plug housing, turned it down on my grinder to fit the car's plugs, then put them back together and crimped the wire. Never dull, but I really didn't want to cut the car's harness.
With this I hooked everything up according to the BQB schematic, closed the doors, and powered on the radio.
WOW!
Sound is crystal clear. Not a hint of distortion in the base/midrange all the way up to 3/4 full volume which is way more loud than I want or need. Solid bass from the front Hans speakers with crystal clear tweeter highs, and a very deep base from the rear two earthquake speakers.Given that each channel is putting out 20 watts peak, I am *well* within the spec for the speakers and the wire to the speakers. Music sounds great, music from my Ipod touch through the bluetooth casette adapter sounds perfect, and I think I got it!
The root of the problem I think is matching the amplifier inputs to the head unit outputs. In this case I was trying to drive the amp's high bain input (300mv to 8v) with the output from the stereo's line output (which is probably 300mv to 2v). Thus the only way I would get appropriate volume is if I was most of the way to full on the head unit where distortion would creep in anyway. Likewise the 20w output from the stereo's amplifier is double what the bqb is trimmed to take (it looks like 10 watts is what comes out of the old head unit) so it was clipping right off the bat.
Going with the pre-amp input on the amplifier (300mv to 2v) was the right way to go and results in the amp doing all the work, the head unit sounding good, and life being normal.
Now I can say that the BQB80 is plenty of power for me, using the speakers I am using. The base is quite solid and distortion free and I can see both the earthquakes and Hans' speakers moving cleanly in their housings. I'm happy, and will run with this setup for the foreseeable future.
Thanks everyone for the thoughts and comments. The only thing I may want to do going forward is select the lower tweeter crossover if it's too bright, and maybe put some sort of filter in front of the earthquakes to ensure they are not trying to replicate high sounds. But that can wait for a bit, any thoughts on the latter type of filter (for the earthquakes)?
C
01-12-2020, 06:38 PM
#18
Rennlist Member
Thread Starter
And oh it does sound good! I did notice the fader was wired backwards (speaker to front was lighting the rear speakers, etc) so I removed the amp and fixed that wiring. Minor mistake.
Minor oddities: I noticed the fader doesn't really fade, it's dropping the signal from the front speakers 100% when about halfway to rear and dropping rear 100% when halfway to front. I think this is because the pots in the fader are expecting that higher voltage and are getting confused by the lower signal values from the pre-amp input. I may just give up on it and wire straight from the head unit to the amp so I can control all four channels from the amplifier, we'll see.
Only other thing is that when I try the jet airplane at takeoff test soundfile (from "The Digital Domain, a Telarc test CD) the right front midrange speaker does crackle a bit. This might be vibration inside the door panel though, it's not the amplifier or pre-amp circuits as I tried swapping the speaker outputs and it still happened (doesn't happen on the door channel). But that is an extreme case beyond normal (I don't need to hear airplanes taking off in my car, I can go to BWI for that) so I might leave things alone till the summer.
Minor oddities: I noticed the fader doesn't really fade, it's dropping the signal from the front speakers 100% when about halfway to rear and dropping rear 100% when halfway to front. I think this is because the pots in the fader are expecting that higher voltage and are getting confused by the lower signal values from the pre-amp input. I may just give up on it and wire straight from the head unit to the amp so I can control all four channels from the amplifier, we'll see.
Only other thing is that when I try the jet airplane at takeoff test soundfile (from "The Digital Domain, a Telarc test CD) the right front midrange speaker does crackle a bit. This might be vibration inside the door panel though, it's not the amplifier or pre-amp circuits as I tried swapping the speaker outputs and it still happened (doesn't happen on the door channel). But that is an extreme case beyond normal (I don't need to hear airplanes taking off in my car, I can go to BWI for that) so I might leave things alone till the summer.
01-12-2020, 09:33 PM
#19
Rennlist Member
I didn't finish reading - glad you got it all working to your satisfaction.
However, the stock amp and the DIN connector are Exhibit A on the "what were they thinking?" list for this car IMO.
You can repurpose the individual wires since they usefully run from behind the radio to the amp location and from there to each speaker location. The 928 wiring diagram shows the radio-to-amp and amp-to-speaker wiring quite clearly. Just cut a new amp in where the old one is and use the individual wires to hook it up at the radio and amp locations.
Also, the Pioneer GM-D1004 is an outstanding, cheap, and tiny amp. I have two of them in the stock amp location and they are capable of very clean deafening power. They will take line or speaker level input.
However, the stock amp and the DIN connector are Exhibit A on the "what were they thinking?" list for this car IMO.
You can repurpose the individual wires since they usefully run from behind the radio to the amp location and from there to each speaker location. The 928 wiring diagram shows the radio-to-amp and amp-to-speaker wiring quite clearly. Just cut a new amp in where the old one is and use the individual wires to hook it up at the radio and amp locations.
Also, the Pioneer GM-D1004 is an outstanding, cheap, and tiny amp. I have two of them in the stock amp location and they are capable of very clean deafening power. They will take line or speaker level input.
Last edited by chart928s4; 01-12-2020 at 09:36 PM. Reason: Missed a post
01-13-2020, 10:47 AM
#20
Rennlist Member
Thread Starter
Indeed, this is older equipment no doubt. However it seems to work pretty well now and I'm trying to keep the car as stock as possible. The 86 amplifier is different from the 87 and up one in that it's a pretty simple 4 channel without subwoofers.
So far running the system at 50% volume is more than loud enough, with a bit of hiss from the tape system that can be reduced by selecting the "Metal" option to reduce the bias. I wonder if re-encoding my MP3's through a Dolby B encoder would make the sound system even better. Will have to give that a try.
So far running the system at 50% volume is more than loud enough, with a bit of hiss from the tape system that can be reduced by selecting the "Metal" option to reduce the bias. I wonder if re-encoding my MP3's through a Dolby B encoder would make the sound system even better. Will have to give that a try.