Weekend score: Altec Lansing VS4121 Speakers for $7.59!
Was browsing the local classifieds for cheap audio crap last week. Found this system up for sale for ridiculously cheap.
After a few days of not enough time or bad weather i could finally get to pick it up on Saturday. The seller also gave me a bag of "old electronics a neighbor gave me and i do not need", which contained various crap like old TV speakers, what appears to be a monitor power supply, a couple Samsung USB cables with a weird connector at the other end, could be some service interfaces, and a cheapo universal laptop power brick that just had a plastic tab on its voltage selector switch broken, some super glue and it works fine. Quite the score.
Fault on the Altec Lansing system was described as "one sat works intermittently, sub cuts out". The subwoofer had been removed from the box and wires cut but it was in very good shape. He told me that he wanted to build the sub in another speaker box but never got round to it. He did not provide me with a signal cable for this system.
So, i hooked up the system with my own signal cable and plugged it in. Both satellites sounded fine!
I then took the amp out and replaced the wires for the subwoofer. It appeared to work as well and sounded very clean, no scratching or grinding noises in free air.
I put the sub back in the box and fitted all the missing screws. Then i set up the system in the bedroom, with the sats to the sides and the sub under the bed and it sounds great.
Later i did find that it does indeed cut out. However, not just the sub does it, the whole thing goes quiet. Responsible for this are the bass knob and the power switch that are on the front of one of the satellite speakers, and it only does that if you mess with the knobs a lot - leave them alone and the whole thing plays along with no problems!
I did not see any obvious ways to take that satellite apart, but apparently it is possible: http://flybchen.blogspot.ro/2013/06/...ng-vs4121.html so i will look into it soon.
All the caps inside this are Samxon and none are bloated. The PCB is very clean and sparse inside.
There are another few mods that i would like to make to this system, first of all there is a minor amount of hum present at all times, i have read that this is a flaw present in all of them not just mine. Likely a small ground routing issue.
Also, if the bass knob is turned towards minimum, it starts buzzing a little bit (not 50Hz hum, higher harmonics only, which is interesting). Then there is the slightly louder hum that occurs when i plug my laptop in while it is being connected to this system, i will try replacing the extension cord with a grounded one as i am pretty sure the lack of earth is my issue here. But to stop worrying about hum entirely, i am thinking of removing the existing mains transformer and marrying the power brick mentioned above (after recapping, of course!) to this system.
Another thing i am looking to do is extend the length of the bass port and thus lower the tuning frequency of the box. While testing i have noticed that the woofer seems to unload a little below 40Hz despite it still having useful output at this point. This will reduce midbass response as a trade-off for the low-end extension, however i also have a large peak between 80-100Hz (which is likely to be also caused by the room), so this trade-off would actually be desired in my case.
Finally, there is an amount of hiss that makes itself present as i turn the volume knob past 1/3, i am looking to adjust the gain internally so i do not have any more available than is required for the devices i hook up to it. I have checked the tone control IC's datasheet (LM1036N and it has pretty good specs, so the problem is either simply too much gain, or i may need to upgrade the opamps in the crossover.
The amplifier in this is a TDA7377, where the two satellites are using two channels in single ended mode, with the sub bridged over the other two. For a "car radio" chip this certainly sounds impressive - yet another proof that good speakers are the most important thing in a sound system, and the amplifier is a second priority. This system has two front-firing tweeters on each sat, with a down-firing midrange speaker at their base. They put out beautifully clear sound with crisp highs. Compare this with anything Logitech has put out, where none of their systems ever sporting tweeters.
After a few days of not enough time or bad weather i could finally get to pick it up on Saturday. The seller also gave me a bag of "old electronics a neighbor gave me and i do not need", which contained various crap like old TV speakers, what appears to be a monitor power supply, a couple Samsung USB cables with a weird connector at the other end, could be some service interfaces, and a cheapo universal laptop power brick that just had a plastic tab on its voltage selector switch broken, some super glue and it works fine. Quite the score.
Fault on the Altec Lansing system was described as "one sat works intermittently, sub cuts out". The subwoofer had been removed from the box and wires cut but it was in very good shape. He told me that he wanted to build the sub in another speaker box but never got round to it. He did not provide me with a signal cable for this system.
So, i hooked up the system with my own signal cable and plugged it in. Both satellites sounded fine!
I then took the amp out and replaced the wires for the subwoofer. It appeared to work as well and sounded very clean, no scratching or grinding noises in free air.I put the sub back in the box and fitted all the missing screws. Then i set up the system in the bedroom, with the sats to the sides and the sub under the bed and it sounds great.
Later i did find that it does indeed cut out. However, not just the sub does it, the whole thing goes quiet. Responsible for this are the bass knob and the power switch that are on the front of one of the satellite speakers, and it only does that if you mess with the knobs a lot - leave them alone and the whole thing plays along with no problems!
I did not see any obvious ways to take that satellite apart, but apparently it is possible: http://flybchen.blogspot.ro/2013/06/...ng-vs4121.html so i will look into it soon.
All the caps inside this are Samxon and none are bloated. The PCB is very clean and sparse inside.
There are another few mods that i would like to make to this system, first of all there is a minor amount of hum present at all times, i have read that this is a flaw present in all of them not just mine. Likely a small ground routing issue.
Also, if the bass knob is turned towards minimum, it starts buzzing a little bit (not 50Hz hum, higher harmonics only, which is interesting). Then there is the slightly louder hum that occurs when i plug my laptop in while it is being connected to this system, i will try replacing the extension cord with a grounded one as i am pretty sure the lack of earth is my issue here. But to stop worrying about hum entirely, i am thinking of removing the existing mains transformer and marrying the power brick mentioned above (after recapping, of course!) to this system.
Another thing i am looking to do is extend the length of the bass port and thus lower the tuning frequency of the box. While testing i have noticed that the woofer seems to unload a little below 40Hz despite it still having useful output at this point. This will reduce midbass response as a trade-off for the low-end extension, however i also have a large peak between 80-100Hz (which is likely to be also caused by the room), so this trade-off would actually be desired in my case.
Finally, there is an amount of hiss that makes itself present as i turn the volume knob past 1/3, i am looking to adjust the gain internally so i do not have any more available than is required for the devices i hook up to it. I have checked the tone control IC's datasheet (LM1036N and it has pretty good specs, so the problem is either simply too much gain, or i may need to upgrade the opamps in the crossover.
The amplifier in this is a TDA7377, where the two satellites are using two channels in single ended mode, with the sub bridged over the other two. For a "car radio" chip this certainly sounds impressive - yet another proof that good speakers are the most important thing in a sound system, and the amplifier is a second priority. This system has two front-firing tweeters on each sat, with a down-firing midrange speaker at their base. They put out beautifully clear sound with crisp highs. Compare this with anything Logitech has put out, where none of their systems ever sporting tweeters.
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