Since I'm on a break for a couple of months, I decided to undertake home improvement.
I have a long to-do list, the first was to make a real interconnect for my MX5021-Delta66 connection. One thing led to another and soon the mighty MX5021 subwoofer was in six pieces on my living room floor, ready for soldering iron and multimeter.
Opening it was a piece of work, however. I struggled till I found the easy way into the thing was to remove the front grille (yes, it does come off) and unscrew the subwoofer.
An hour later it was back in place after mods, and I did a quick search on Google to see what others had been doing with this. To my surprise, there was just one Jimmy Auw in Indonesia or someplace who had done the mods. That webpage is here: Jimmy’s Junkyard » Blog Archive » Altec MX5021 Speaker Mod
I don't agree with all of Jimmy's mods, and down in the comments section are what I ended up doing.
The point of the thread is that the MX5021 is easily moddable if you have touched a soldering iron before.
After a full suite of mods the MXs already good sound goes up a couple of notches. It is still not at the level of the discontinued Klipsch Promedia Ultra, which I consider the best compact 2.1 system I've heard (bar bookshelf/sub combos). But it is head and shoulders above the stock system, and gives a lot of entry-level bookshelf/amp systems a run for the money. At its current price + approx 1500 bucks for all the mods, it's a no-brainer.
Be warned: Doing the mods will void your warranty. Also, I take no responsibility for any damage to you or any of your equipment while you're doing the mods.
To perform the mods you will need:
1. Tools: Soldering iron, solder and some soldering skills. One hobby knife, a wire cutter/stripper and lead snipper.
2. Screwdriver, Philips head. Battery operated prefered if you're buying one to start with. There are a lot of screws, some very difficult to manually remove. Elbow grease also works, but a decent screwdriver with a thick handle will help.
3. The components (based on the list of mods below)
4. Two hours of listening. This will warm up the unit and soften some of the glue. The sub is well put together, with lots of glue. It will also get you to notice the sound of the system, as we are now analysing and expect results it is important to measure the 'before'.
The mods I recommend doing in order of priority are:
1. Bypass caps on the tweeter.
How:
This needs you to remove 6 screws from the back of each satellite and solder a small film capacitor across the 4.7uF bipolar electrolytic. This is very easy to do and totally reversible, if you have a small enough capacitor it will be unnoticeable. The sound will improve a lot, though.
What:
I use BC components .47 uF, 63 volts MKP16 from Digikey - a range from .22 uF to .47 uF is suitable. More than that and the crossover frequency will shift, lower than that and you may not notice the difference. For those willing to do some legwork you may get similar values from your local electronic market.
Don't use the green polyester caps if can help it: some industrial electronics shops will yield yellow metallised polypropylene caps, which work superb in this application. They are more inconvenient due to larger size and lead orientation, but are easily available and don't involve forex. You may get Panasonic 'Crossover capacitors'. These are large metallised capacitors, mostly brown in colour. You may even get a 4.7uF cap and then you can just replace the original. They are huge though (a 4.7 will be ~ the size of a small wax match-box), so watch out, there ain't much room in there. Plan thrice, solder once.
Material required: 2 capacitors of 0.22-0.47, any voltage over 35 volts will work fine.
Why?
The reason the mod is done is that an electrolytic has a rising impedance at high frequencies, the bypass gives a lower impedance path to the high frequencies. The mod will result a more open soundstage and better definition at high frequencies. Some may find it a bit bright - but that's a result of hearing new things. The treble extension really picks up.
2. Change of subwoofer wire.
How: You have to pry off the front of the sub. The grill detaches quite easily (gentle pulling pressure is required). Pull from all sides at once. This is not a speaker grille. The inserts are glued in, so the thing takes a bit of effort. Enthusiasm will lead to a broken frame.
Once you get the grille off, there is a decorative plastic insert ring around the speaker, this comes off similar to the main front grille, with glued-in inserts. Don't use any tools or you will dent the ring. Then come four screws and the subwoofer is free. The sub should be lying on the floor, face up, or else the driver will fall out and break your foot. Gently lift the sub till the wires pull taut. Use the cutters and cut the wire off, we will hardwire it with much better wire. Notice how thin the wire is - even the cable that comes on a computer fan is thicker.
We have to now remove the power connector. Look inside the subwoofer and you'll see a plug like an AT power connector. This needs to be pulled off, except that is is glued in. This is where we use a knife, just cut through the glue. the connector is strong and will not be harmed. I didn't even look, I just ensured I didn't hit the wire, and hacked away mercilessly, pulling the connector between attempts to check on progress. In a minute the connector was off.
Then it's 12 screws removed from the back panel, and the MX5021 motherboard is in your hands. Remove the connector for the sub. I just cut it off and left it like that. Using the soldering iron, solder the new wires in. This kind of wire normally has a stripe for the polarity marking. I would trace out the rear of the connector, and soldered my new thick wire in place, on the back of the board. Solder the other end to the sub, and you're done. Note that if you want to do any other mods, this should be the last as it's messy to work with a 18-inch cable dangling off a board.
What?
We will use generic 15AWG speaker wire. Do NOT use the twisted cord we use to wire up lamps. 15 AWG means the wire core should be roughly be 1.5 mm in diameter. We just need 18 inches of wire.
Why?
Seriously, the stock cable is pathetic. The thicker cable reduces the impedance of the amp to the speaker, improving the bass resolution and slam (extension is not affected) and overall tighter bass. Essential mod IME. I had to pull the sub away from the wall to correct the bass after the mod.
3. Recap
How?
Recapping is basically changing out all the critical caps in the signal path. The caps are removed very easily. Hold the board upside down, apply the soldering iron and simultaneously pull the cap from the other side. It will pull right out from one side. Then the next leg, and it's out. Took me two seconds per cap. this board is very easy to recap. In contrast my Delta66 took me about 5 minutes per cap, or half a day for the entire board.
Be careful not to push the cap back, or the track will come off. The board quality is very poor plus humidity doesn't help, and some tracks will come off anyway, so don't do this unless you're OK with a few loose capacitors. Superglue will help a lot after all the carnage is over. Even I needed it.
What?
Here's the thing - don't do this mod unless you have the right parts. I did, so I changed them out. The stock Samxcon caps are not horrible, they're just average. You may not get better capacitors in India to replace them. I used some imported and some Indian ones. Following is parts list:
C61, C54 They're originally 0.22uF. I used 0.47 Thermax met/poly caps. these should be easily available for about 15 bucks. Brand is not too important. If you notice they're the caps Jimmy changed first.
C50, 52: 2.2uF
C45, 34: 22uF
C41, 46: 1uF
I replaced all 6 caps with 22uF Panasonic FCs, the budget audiophile's caps. Cost 5 bucks each from Digikey if you buy a hundred. One value saves money. Note that almost any value from 4.7 to 47uF works for all locations here.
Why?
At a very basic level, all caps in the signal path are bad. This amp has about 5 caps between input and the amp per channel. Terrible. Each capacitor degrades the sound. Ideally there should be no cap but this requires forethought and some expense in design. Since we cannot eliminate the caps or it will cause problems in the amp, we substitute them.
Jimmy used some very expensive caps, but he used only two of them. I rather work on the whole chain. I decided that met/poly caps will be very expensive, so I opted for the FCs. The biggest improvement comes in the midrange resolution. Now the texture of instruments is totally clear. I used to monitor because the MXs were perfect at telling you where each instrument was, now even the timbre is great. Finally I can relax while listening to them! MP3s sound good, these speakers won't improve to the point where MP3s sound bad, as the power amps isn't the best quality. But we can enjoy the system
While I did this, I also changed the thin little stock wire for the satellites to thicker wire. I used some leftover 15 ga wire - this may not actually help the sound too much, but placebo is also a drug
Also added bypass caps for the satellite amp - this is a little too technical so won't get into it, and probably contributes only 5% to the final result.
Mods that will be done and updated later: 1. Opamp swapping and 2. RCA jacks for input on the back instead of that wimpy little minijack. for this set I think that's the most that should be done, as spending too much on this is pointless.
Total cost excluding tools:
15 ga speaker wire, 4 meters (including satellite wiring) - 200 INR
22uF/50V Panasonic FC, 6 pcs. - 50 bucks (tops)
0.47 uF Thermax met/poly caps - 30 bucks (iirc)
4 hours time - priceless.
Have fun, and happy listening.
I have a long to-do list, the first was to make a real interconnect for my MX5021-Delta66 connection. One thing led to another and soon the mighty MX5021 subwoofer was in six pieces on my living room floor, ready for soldering iron and multimeter.
Opening it was a piece of work, however. I struggled till I found the easy way into the thing was to remove the front grille (yes, it does come off) and unscrew the subwoofer.
An hour later it was back in place after mods, and I did a quick search on Google to see what others had been doing with this. To my surprise, there was just one Jimmy Auw in Indonesia or someplace who had done the mods. That webpage is here: Jimmy’s Junkyard » Blog Archive » Altec MX5021 Speaker Mod
I don't agree with all of Jimmy's mods, and down in the comments section are what I ended up doing.
The point of the thread is that the MX5021 is easily moddable if you have touched a soldering iron before.
After a full suite of mods the MXs already good sound goes up a couple of notches. It is still not at the level of the discontinued Klipsch Promedia Ultra, which I consider the best compact 2.1 system I've heard (bar bookshelf/sub combos). But it is head and shoulders above the stock system, and gives a lot of entry-level bookshelf/amp systems a run for the money. At its current price + approx 1500 bucks for all the mods, it's a no-brainer.
Be warned: Doing the mods will void your warranty. Also, I take no responsibility for any damage to you or any of your equipment while you're doing the mods.
To perform the mods you will need:
1. Tools: Soldering iron, solder and some soldering skills. One hobby knife, a wire cutter/stripper and lead snipper.
2. Screwdriver, Philips head. Battery operated prefered if you're buying one to start with. There are a lot of screws, some very difficult to manually remove. Elbow grease also works, but a decent screwdriver with a thick handle will help.
3. The components (based on the list of mods below)
4. Two hours of listening. This will warm up the unit and soften some of the glue. The sub is well put together, with lots of glue. It will also get you to notice the sound of the system, as we are now analysing and expect results it is important to measure the 'before'.
The mods I recommend doing in order of priority are:
1. Bypass caps on the tweeter.
How:
This needs you to remove 6 screws from the back of each satellite and solder a small film capacitor across the 4.7uF bipolar electrolytic. This is very easy to do and totally reversible, if you have a small enough capacitor it will be unnoticeable. The sound will improve a lot, though.
What:
I use BC components .47 uF, 63 volts MKP16 from Digikey - a range from .22 uF to .47 uF is suitable. More than that and the crossover frequency will shift, lower than that and you may not notice the difference. For those willing to do some legwork you may get similar values from your local electronic market.
Don't use the green polyester caps if can help it: some industrial electronics shops will yield yellow metallised polypropylene caps, which work superb in this application. They are more inconvenient due to larger size and lead orientation, but are easily available and don't involve forex. You may get Panasonic 'Crossover capacitors'. These are large metallised capacitors, mostly brown in colour. You may even get a 4.7uF cap and then you can just replace the original. They are huge though (a 4.7 will be ~ the size of a small wax match-box), so watch out, there ain't much room in there. Plan thrice, solder once.
Material required: 2 capacitors of 0.22-0.47, any voltage over 35 volts will work fine.
Why?
The reason the mod is done is that an electrolytic has a rising impedance at high frequencies, the bypass gives a lower impedance path to the high frequencies. The mod will result a more open soundstage and better definition at high frequencies. Some may find it a bit bright - but that's a result of hearing new things. The treble extension really picks up.
2. Change of subwoofer wire.
How: You have to pry off the front of the sub. The grill detaches quite easily (gentle pulling pressure is required). Pull from all sides at once. This is not a speaker grille. The inserts are glued in, so the thing takes a bit of effort. Enthusiasm will lead to a broken frame.
Once you get the grille off, there is a decorative plastic insert ring around the speaker, this comes off similar to the main front grille, with glued-in inserts. Don't use any tools or you will dent the ring. Then come four screws and the subwoofer is free. The sub should be lying on the floor, face up, or else the driver will fall out and break your foot. Gently lift the sub till the wires pull taut. Use the cutters and cut the wire off, we will hardwire it with much better wire. Notice how thin the wire is - even the cable that comes on a computer fan is thicker.
We have to now remove the power connector. Look inside the subwoofer and you'll see a plug like an AT power connector. This needs to be pulled off, except that is is glued in. This is where we use a knife, just cut through the glue. the connector is strong and will not be harmed. I didn't even look, I just ensured I didn't hit the wire, and hacked away mercilessly, pulling the connector between attempts to check on progress. In a minute the connector was off.
Then it's 12 screws removed from the back panel, and the MX5021 motherboard is in your hands. Remove the connector for the sub. I just cut it off and left it like that. Using the soldering iron, solder the new wires in. This kind of wire normally has a stripe for the polarity marking. I would trace out the rear of the connector, and soldered my new thick wire in place, on the back of the board. Solder the other end to the sub, and you're done. Note that if you want to do any other mods, this should be the last as it's messy to work with a 18-inch cable dangling off a board.
What?
We will use generic 15AWG speaker wire. Do NOT use the twisted cord we use to wire up lamps. 15 AWG means the wire core should be roughly be 1.5 mm in diameter. We just need 18 inches of wire.
Why?
Seriously, the stock cable is pathetic. The thicker cable reduces the impedance of the amp to the speaker, improving the bass resolution and slam (extension is not affected) and overall tighter bass. Essential mod IME. I had to pull the sub away from the wall to correct the bass after the mod.
3. Recap
How?
Recapping is basically changing out all the critical caps in the signal path. The caps are removed very easily. Hold the board upside down, apply the soldering iron and simultaneously pull the cap from the other side. It will pull right out from one side. Then the next leg, and it's out. Took me two seconds per cap. this board is very easy to recap. In contrast my Delta66 took me about 5 minutes per cap, or half a day for the entire board.
Be careful not to push the cap back, or the track will come off. The board quality is very poor plus humidity doesn't help, and some tracks will come off anyway, so don't do this unless you're OK with a few loose capacitors. Superglue will help a lot after all the carnage is over. Even I needed it.
What?
Here's the thing - don't do this mod unless you have the right parts. I did, so I changed them out. The stock Samxcon caps are not horrible, they're just average. You may not get better capacitors in India to replace them. I used some imported and some Indian ones. Following is parts list:
C61, C54 They're originally 0.22uF. I used 0.47 Thermax met/poly caps. these should be easily available for about 15 bucks. Brand is not too important. If you notice they're the caps Jimmy changed first.
C50, 52: 2.2uF
C45, 34: 22uF
C41, 46: 1uF
I replaced all 6 caps with 22uF Panasonic FCs, the budget audiophile's caps. Cost 5 bucks each from Digikey if you buy a hundred. One value saves money. Note that almost any value from 4.7 to 47uF works for all locations here.
Why?
At a very basic level, all caps in the signal path are bad. This amp has about 5 caps between input and the amp per channel. Terrible. Each capacitor degrades the sound. Ideally there should be no cap but this requires forethought and some expense in design. Since we cannot eliminate the caps or it will cause problems in the amp, we substitute them.
Jimmy used some very expensive caps, but he used only two of them. I rather work on the whole chain. I decided that met/poly caps will be very expensive, so I opted for the FCs. The biggest improvement comes in the midrange resolution. Now the texture of instruments is totally clear. I used to monitor because the MXs were perfect at telling you where each instrument was, now even the timbre is great. Finally I can relax while listening to them! MP3s sound good, these speakers won't improve to the point where MP3s sound bad, as the power amps isn't the best quality. But we can enjoy the system
While I did this, I also changed the thin little stock wire for the satellites to thicker wire. I used some leftover 15 ga wire - this may not actually help the sound too much, but placebo is also a drug
Also added bypass caps for the satellite amp - this is a little too technical so won't get into it, and probably contributes only 5% to the final result.Mods that will be done and updated later: 1. Opamp swapping and 2. RCA jacks for input on the back instead of that wimpy little minijack. for this set I think that's the most that should be done, as spending too much on this is pointless.
Total cost excluding tools:
15 ga speaker wire, 4 meters (including satellite wiring) - 200 INR
22uF/50V Panasonic FC, 6 pcs. - 50 bucks (tops)
0.47 uF Thermax met/poly caps - 30 bucks (iirc)
4 hours time - priceless.
Have fun, and happy listening.
