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Thread: What is this thing?

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    What is this thing?

    Replacing the radio and can't find a wiring diagram that shows an amplifier. Called the Crutchfield tech and they don't show any of the models as having an amp either. They had remote power for a separate tape deck, but I don't think that's what it is either. The caveman in me wants to pull it out and smash it with a rock or sell it on ebay. Just want to make sure it's nothing important first.

    Never mind the scooby doo hair. Thanks.
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    Re: What is this thing?

    Quote Originally Posted by beetleswamp View Post
    Replacing the radio and can't find a wiring diagram that shows an amplifier. Called the Crutchfield tech and they don't show any of the models as having an amp either. They had remote power for a separate tape deck, but I don't think that's what it is either. The caveman in me wants to pull it out and smash it with a rock or sell it on ebay. Just want to make sure it's nothing important first.

    Never mind the scooby doo hair. Thanks.
    Its a speaker (mid range) gives a more full sound. None of the stock stereos for the Van were pre-amp. The amp was built in

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    Re: What is this thing?

    Thank you. I never would have guessed speaker. Obviously it's powered since there are wires going to it. Don't think it works anyway so will take it out and post some photos when we get the van back from the mechanic. They are taking their dear sweet time with the gummy bear issue.

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    Re: What is this thing?

    Quote Originally Posted by beetleswamp View Post
    Thank you. I never would have guessed speaker. Obviously it's powered since there are wires going to it. Don't think it works anyway so will take it out and post some photos when we get the van back from the mechanic. They are taking their dear sweet time with the gummy bear issue.
    Its a strange one the speaker grill is on the bottom essentially pointing to the floor

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    Re: What is this thing?

    Very strange placement indeed. Can't find a diagram that shows how it's wired in, but as long as I can disconnect it and nothing bad will happen I'm sure installing a fresh round of modern speakers in all the other pockets will pick up the slack.

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    Re: What is this thing?

    So I've got one of these too, I just found out. I'd like to use it with my aftermarket stereo because it (probably? maybe?) still works. 4/5 wires of the "sub" harness seem to be connected appropriately, but one is not connected to anything currently.

    Name:  sub wiring.jpg
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    Anyone know what the pink/blue wire is, and how I might be able to splice it into my current harness to make it work?

    I'm kinda an ignoramus when it comes to audio stuff.

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    Re: What is this thing?

    This little speaker is more than just a midrange device. It was designed as a sub woofer for the stock audio system. I remember when purchasing the van new in 86 and wondering how in the world did they get the base response the system had. Now, after getting another van and tearing it apart I find the sub. It is a L+R input stage. The problem you will have is that it was designed to accept audio from the speaker outputs of the old radio. Only one issue here and that is that the new systems you put in are differential in design. This means the output on both the - Neg and +Pos wires for each channel hold a fair amount of DC (Direct Current) This is normal. This is how they get the power amps to go beyond 6 watts. Each wire is the same thing but different and work out of phase. So to a speaker it just plays normally as if there is no DC floating on it. But if you connected one side of the speaker to ground you would hear a serious POP. This is the DC that is floating on each speaker wire.j Be careful here, it could melt the windings in the driver.
    Now, let's return to the sub. The sub also was made at that time period. That means it will not accept the DC on the output of your current radio. There is a fix for this. It is kind of old school but it should work. You tap into each speaker wire to share its output to the sub. Then the wires to the sub must use be wired in series with it a 1000uF capacitor. This will block the DC and the sub will work great. That means you need 4 of these to use the sub. You must also take into consideration the polarity of the DC on each wire. In this case you should us an electrolytic capacitor that is polarized. Take the plus side and connect that side to the radio and the minus side to the sub.

    I am about 99% confident this will work. However if you want I can build up a fixture on my bench and try it if you would like.

    As for the subs response. It will play like dog poop on the bench. However, the Japanese are not stupid. The speaker is designed to work low to the floor taking advantage of the large wave length that base response provides. As an example, at 20KHz the wave length is less than an inch. That is why tweeters are so small. But at 20Hz the wave length is almost 150 feet. So you see, when placed low to the floor and aimed down the unit takes advantage of the cavity making it a tune port and the base is rather good.

    Let me know and I will jig it up.

    OH, forgot to tell you, I am an audio and video electrical engineer.

    MT

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    Re: What is this thing?

    Quote Originally Posted by MyToy View Post
    This little speaker is more than just a midrange device. It was designed as a sub woofer for the stock audio system. I remember when purchasing the van new in 86 and wondering how in the world did they get the base response the system had. Now, after getting another van and tearing it apart I find the sub. It is a L+R input stage. The problem you will have is that it was designed to accept audio from the speaker outputs of the old radio. Only one issue here and that is that the new systems you put in are differential in design. This means the output on both the - Neg and +Pos wires for each channel hold a fair amount of DC (Direct Current) This is normal. This is how they get the power amps to go beyond 6 watts. Each wire is the same thing but different and work out of phase. So to a speaker it just plays normally as if there is no DC floating on it. But if you connected one side of the speaker to ground you would hear a serious POP. This is the DC that is floating on each speaker wire.j Be careful here, it could melt the windings in the driver.
    Now, let's return to the sub. The sub also was made at that time period. That means it will not accept the DC on the output of your current radio. There is a fix for this. It is kind of old school but it should work. You tap into each speaker wire to share its output to the sub. Then the wires to the sub must use be wired in series with it a 1000uF capacitor. This will block the DC and the sub will work great. That means you need 4 of these to use the sub. You must also take into consideration the polarity of the DC on each wire. In this case you should us an electrolytic capacitor that is polarized. Take the plus side and connect that side to the radio and the minus side to the sub.

    I am about 99% confident this will work. However if you want I can build up a fixture on my bench and try it if you would like.

    As for the subs response. It will play like dog poop on the bench. However, the Japanese are not stupid. The speaker is designed to work low to the floor taking advantage of the large wave length that base response provides. As an example, at 20KHz the wave length is less than an inch. That is why tweeters are so small. But at 20Hz the wave length is almost 150 feet. So you see, when placed low to the floor and aimed down the unit takes advantage of the cavity making it a tune port and the base is rather good.

    Let me know and I will jig it up.

    OH, forgot to tell you, I am an audio and video electrical engineer.

    MT

    Woah, cool. That's a way better response than I ever hoped for.
    I'm trying to digest what you're saying here. 2 of the 5 wires (P and L-G) seem to still be tapped into the regular speaker wires for the Left and Right speakers (like in the diagram). I should cut the wires that then go to the sub after they split off towards the sub and put a 1000uF capacitor in-line before it gets to the sub?

    That's 2, where should I put in the other 2 capacitors?

    And what should I do with that 5th wire (P-L) in the diagram?

    ha, feel like making a doodle in Paint for me?

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    Re: What is this thing?

    OK, here is a rough drawing of what you have to do. I would suggest I try this first. Like I said, I am 99% confident this will work but it is always best to physically test it first.
    Anyway, this is pretty straight forward and "Old School" for sure. We are building a Phantom ground here. Then radio does not use a ground any more for its speakers because they are differential. So by floating the ground with the caps makes up this Phantom ground. The caps simply block the DC from leaving the radio and allows the sub woofer to work. I know for a fact that the subwoofer does not line DC on its inputs.
    The wire color codes in the manual does not match mine. So I took a pic of mine so you can see the colors. I matched those in the drawing.


    I am traveling this week so maybe this weekend I can take some time and build this up for you. If it performs as well as I expect you are good to go!


    MT
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    Re: What is this thing?

    Hello,

    Until I was doing some work under the dash and had to pull it, I'd always thought this was part of the AC/icebox system. Pretty surprised to see it was a speaker. Has anyone tried the circuit with the 1000uF caps? I was considering picking up a floating ground adapter but might like to try this suggestion instead.

    Thanks!

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    Re: What is this thing?

    The best way to do this is with an isolation transformer with a 1:1 ratio. This would be hard to find because the output impedance of the radio is low, like 2 to 4 ohms and input to the sub amp is high. Plus it would have to be rather large in order to support the low frequency response need for the sub.
    I will do some work looking for other alternatives. In the mean time I will jig up the schematic and give it a whirl.

    It should work, but you know those Murphy's

    MT

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    Re: What is this thing?

    Quote Originally Posted by MyToy View Post
    The best way to do this is with an isolation transformer with a 1:1 ratio. This would be hard to find because the output impedance of the radio is low, like 2 to 4 ohms and input to the sub amp is high. Plus it would have to be rather large in order to support the low frequency response need for the sub.
    I will do some work looking for other alternatives. In the mean time I will jig up the schematic and give it a whirl.

    It should work, but you know those Murphy's

    MT
    Thanks for the reply. I had the same thought about using a couple transformers but I couldn't anything with the right specs that was reasonably priced. Some inexpensive caps seem like a much better way to go. Looking forward to hearing about your results!

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    Re: What is this thing?

    Sure thing Nick. I can tell you that when you get it up and running you will be very impressed considering how small it is.

    I have not done any work verifying this only because it did not seem there was much interest. It is somewhat of a job doing the experiment. The caps are cheap for sure, I have tons of them in the lab here I use. It is just putting it all together and then running in the real world when it is mounted to verify its response.

    I will try this weekend. I just got my van back with a newly rebuilt engine so there is much there to do putting Humpty Dumpty back together again. But I will try and will keep you posted.

    I will also verify the color code on the device telling you what is B+ always hot and which one is B+ from radio for power up control.

    MT

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    Re: What is this thing?

    I was able to set up the sub woofer test this morning. It does work rather well however depending on the source there can be a bit instability to the radio causing it to oscillate. I then tried an isolation transformer which worked well but it brings the output impedance down to much which can cause more instability.

    I then ran an analysis on the audio itself under 500Hz to see how much real separation , if any, there would be at these low frequencies. My theory was correct. Below 500Hz the signal is almost 100% mono. This means that you can use the caps on one channel and tie both left and right of the power amp to that one channel and get 99% of the base you would have gotten by using both.

    So just use one channel from the source, run either the left or the right channel to both channels of the sub amp module and you will be pleased with the results.

    Have fun! It sounds great. I am listening to the Police right now, very cool.

    MT

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    Re: What is this thing?

    Thanks for the great experimentation and analysis! Makes sense that there wouldn't be a big difference between L/R channels at low freqs. I've already ordered some caps and will rig everything up this weekend.

    Quote Originally Posted by MyToy View Post
    I was able to set up the sub woofer test this morning. It does work rather well however depending on the source there can be a bit instability to the radio causing it to oscillate. I then tried an isolation transformer which worked well but it brings the output impedance down to much which can cause more instability.

    I then ran an analysis on the audio itself under 500Hz to see how much real separation , if any, there would be at these low frequencies. My theory was correct. Below 500Hz the signal is almost 100% mono. This means that you can use the caps on one channel and tie both left and right of the power amp to that one channel and get 99% of the base you would have gotten by using both.

    So just use one channel from the source, run either the left or the right channel to both channels of the sub amp module and you will be pleased with the results.

    Have fun! It sounds great. I am listening to the Police right now, very cool.

    MT

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    Re: What is this thing?

    Finally got around to trying this and confirm that it does indeed work great! I did as you suggested and just used the right channel. I'm surprised at how much of a difference that little speaker makes. Thanks again for the help!

    Quote Originally Posted by MyToy View Post
    I was able to set up the sub woofer test this morning. It does work rather well however depending on the source there can be a bit instability to the radio causing it to oscillate. I then tried an isolation transformer which worked well but it brings the output impedance down to much which can cause more instability.

    I then ran an analysis on the audio itself under 500Hz to see how much real separation , if any, there would be at these low frequencies. My theory was correct. Below 500Hz the signal is almost 100% mono. This means that you can use the caps on one channel and tie both left and right of the power amp to that one channel and get 99% of the base you would have gotten by using both.

    So just use one channel from the source, run either the left or the right channel to both channels of the sub amp module and you will be pleased with the results.

    Have fun! It sounds great. I am listening to the Police right now, very cool.

    MT

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    Re: What is this thing?

    Fantastic.

    Just so you know my LE is very close to completion. The interior will be next and as I plan that out I will be planning in an entirely new audio system for the vehicle. The goal is to make it so it is non evasive to the chassis and frame yet still supply the quality of audio that one would expect from a typical high end system.

    I will be performing a complete spectral analysis of the chassis in a couple of weeks. With that I should be able to design in the correct drivers to use. The two front dash speaker drives will be replaced with a mid range product that will have the excursion needed to supply lower midrange audio down to about 700Hz. This will be matched to a set of tweeters that will crossover at the hinged high frequency response of the dash midrange drivers. The back hatch air vents will be modified to accept two sub woofers rolling off at about 120 Hz. Then an additional pair of midrange drivers in the rear columns and another set, one in the side door and one under the rear AC control.
    I will use 3 electronic crossover amplifiers for each crossover range.

    When completed I will "voice" the cabin for a linear frequency response using all 10 drivers. All of them will be concealed in the upholstery to match with the cosmetics.

    I will keep the group posted on this so if anyone wants to replicate it I can provide all the necessary hardware info.

    Happy it all worked out. I will probably use that sub woofer in conjunction with the rest of the sound system.

    MT

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