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  1. #1
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    Lightbulb Monitor 5 Jr Rebuild

    I decided to rebuild the components in my Monitor 5 Jrs a few weeks ago. There was talk about doing it by a couple members, but to my knowledge, it hadn't been done lately. The benefits of replacing stock components with higher quality ones had be proven in the past to me, but the benefit of replacing old, leaky capacitor with new ones is a sound investment, both sonically and electrically. So I decided to order some parts and put some heat in the old iron.

    My Monitor 5 Jrs were not stock to begin with. A few months ago I swapped RDO194s into them and have highly enjoyed the upgrade. When I started looking at parts, I realized that I didn't need too many. The Monitor 5 Jr only has 5 components in its crossover (the simpler the better, right?). It uses two inductors at .56mH and .19mH which I just left. It's debatable whether changing the inductor is an improvement, so I just decided to leave it. Plus the fact that the bind post cup and .56mH inductor are the same unit, so that is just more work than I wanted. There is also a polyswitch which luckily had never acted up, but I decide to replace them with a jumper just for good measure (the simpler the better, right?).

    The two components that I did replace were the 1 Ohm, 5w resistor and the 12uF, 100v capacitor. Because there was only two components, I knew I could keep the price of this rebuild low. On my SDAs, I used Mills and Sonicaps with great success, but wanted to try something different (and cheaper) for my little guys. I decided to buy from Parts Express because of my great history with them and their good selection. For the resistors, PE offers Mills 12w for $3.25 and Dayton Audio 10w for $1.25. I thought both were good selections, being that they have similar power ratings and both have reviewed well. I was actually going to use the Dayton to try something different, but the part was back ordered and I can be impatient. So Mills resistors were chosen even though they were a little more money.

    For the capacitors, there were many options available, and it took me awhile to make my selection. PE offers a "12uF 100V Non-Polarized Capacitor" for $0.60, but I was going to be audiophile snob and use a name brand. Dayton Audio offers two 12uF caps, both at 250v. However, one has a 1% tolerance and sells of $8.08, and the other has a 5% tolerance and sells for $4.34. The three other options were a Jantzen 400v at $5.63, a Solen 400v at $7.03, and the most expensive Kimber Kap 200v at $27.66. I have heard many mixed reviews of Solen, so they have never been my first choice. The Kimber was out because I was trying to stay "budget" as was the Dayton 1%. This left the Dayton 5% and the Jantzen for my choosing, and here was the breakdown:

    Dayton 5%

    Price: $4.34
    Dimensions: 22.5mm x 56mm
    Voltage: 250v
    Tolerance: 5%
    Construction: Metallized Polypropylene

    Jantzen

    Price: $5.63
    Dimensions: 27mm x 44mm
    Voltage: 400v
    Tolerance: 5%
    Construction: Metallized Polypropylene


    As is obvious, the caps are similar and the only real difference is the voltage. I'm not sure that the voltage of the cap has an effect on the sound as long as the stock voltage is meet, but being a tube guy, I like high voltage. One point for Jantzen. The price of the Dayton is lower, so one point for them. After reading many reviews, both the Dayton and Jantzen tested well for "budget" caps, which makes the score tied 2-2. The last thing I am looking at is the size. Since the Monitor 5 Jr has a compact crossover, size was a concern. I didn't feel that diameter was a huge concern because they are both mid size and similar sizes. However, the Dayton was longer than the Jantzen by 12mm, so that makes the winner Jantzen at a score of 3-2. Plus, I just wanted to try them, so call me biased.

    My bag of parts (four total to be exact) took about a week to arrive and I only paid $1.50 for shipping! The total came to about $20, which I thought was a great deal and well worth it for a little crossover work (and hopefully a sound improvement). When they arrived, I inspected the contents of the package and received everything that I had ordered (which is my experience with PE). Even though I had the dimensions of the components, I never really know the size of something until I see it and hold it. The components were a little larger than I expected, but still medium size as far as hifi components go.

    The Monitor 5 Jr rebuild started with opening up the speakers cab by removing the binding post/crossover cup from the back. The speaker leads are soldered directly to the crossover, so I had to disconnect them from the drivers themselves. This proved easy as the mid parallels the crossover, but I actually had to remove the tweeter to disconnect its leads because of the cramped quarters. I then pulled out the cup to look at what I had. The board is actually screwed to the cup face down so that the components are inside the .56mH inductor. I removed the screws that held down the board, and the board didn't come up. After a few "polks" around I realized that the leads from the .56mH inductor, as well as the leads from the binding posts were soldered on in a fashion that provided very little wiggle room for the board.

    My first task was desoldering these joints to allow me to remove the board for further work. Be sure to mark where components and leads were removed so that you replace them in the right location when you are putting the board back together. I started desoldering all the components on the board and cleaning up the holes and pads. The only tricky piece to remove was the capacitor since one side of it was glued to the .19mH inductor. This was successfully removed my desoldering one end, prying the cap off the board and inductor by pulling from that end, then desoldering the other end. Once everything was removed, I started by soldering in a jumper where the old polyswitches had been. I bent the jumpers over on their sides since this would allow the new caps to sit lower on the board. Next was the resistor. Since it was somewhat tall and skinny, it went in standing up, with the top lead having to be extended and run back down to the other hold. Both of those pieces went back onto the board like stock.

    Installing the new Jantzen caps however changed the board on my little Jrs. Soldering them into the original holes was not an issue as they were just about as wide as the caps. A little fitting was required, but no where near that of my SDAs. The problem came when I soldered the caps on, and then turned the now completed board over to reinstall it in the inductor/cup. There was no way that it was going to fit. After considering my options, I figured out that I was going to sandwich the board against the inductor/cup. I straightened the solid inductor wires and the binding post wires and placed the board and components against the inductor/cup. Then, soldered the four wires to keep them and the board in place. The physical strength of the unit is not as good as if it was screwed or glued to the inductor/cup, but it does hold pretty well because of the solid core wire. I don't know if I would trust this set-up if I was shipping the speakers or something violent like that, but for normal wear and tear, it will work well.

    Now that the rebuild was complete on the board, all that was left was reconnecting the leads to the drivers and reinstalling the tweeters and binding post cups. Luckily, the new, larger capacitors don't change the clearance of the cups in the speaker cabs. With all the screws back in place, I connected the speakers to my amp to make sure that everything was working and operating properly. With all the drivers checked and working properly, I turned the amp back off as I didn't want to get an impression of the sound before they were burned in at least a little. My little Monitor 5 Jrs are now being burned in using a combination of music and pink noise. I will do initial listening tests at around 10 hours of operation.

    If I were to do this over again, I would probably solder the cap upside down on the board so that I could screw down the board back onto the cup in the original fashion. This would probably provide a little more stability to the crossover, as well look a little better. This was an easy project and once I figured out how I was arranging the components, the second board took me only about 15 minutes. I would highly recommend this for anyone wanting to get into electronics work but not wanting to get over your head for a first project.
    Last edited by zingo; 08-11-2008 at 05:39 PM.

  2. #2

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    Nice post. Sounds like the exact procedure I performed on my 5B's. Really they are the same speaker with a smaller PR.

    I'll be interested in your impressions. I'm trying to find some time to replace the high frequency Solen caps I put in with Clarity caps to see if I can "mellow" out the upper midrange a bit. Even with the RD0's there seems to be a forwardness to the upper midrange (coming from the tweeter). It's not really that bad, but I want to take it down a notch and smooth out the response a little bit.

    Maybe I missed it but what value resistor did you use?

    H9

    P.s. I hope you changed the resistor out......that's in the signal path and makes a huge difference
    Last edited by heiney9; 08-11-2008 at 11:57 PM.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  3. #3
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    I used the 1 Ohm Mills 12w resistor. :D


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    Thanks for posting your rebuild experience! Not sure exactly when I'll get to it, but this is a project I'd like to undertake on my 5Jr+.

    Highly looking forward to your listening review after burn-in.

    Jay

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    Go for it, you will be rewarded

    http://www.polkaudio.com/forums/show...ighlight=5b%2A

    H9
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

  6. #6
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    Jay,
    Rebuilding crossovers is always a fun project, and yields good results too! If you have any questions on that rebuild, feel free to shoot me a PM and I'll help you with any part of it. Also remember that you are going to need a 12uF and a 1.5uF cap to make the needed 13.5uF C1 capacitor for the Jr+ (verses 12uF C1 cap for original Jr).

  7. #7
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    Great write up,congrats on doing the upgrade.

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    Thanks for the offer; I'll certainly take you up on it when I get to it (some day...)

    Jay

    Quote Originally Posted by zingo View Post
    Jay,
    Rebuilding crossovers is always a fun project, and yields good results too! If you have any questions on that rebuild, feel free to shoot me a PM and I'll help you with any part of it. Also remember that you are going to need a 12uF and a 1.5uF cap to make the needed 13.5uF C1 capacitor for the Jr+ (verses 12uF C1 cap for original Jr).

  9. #9
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    Here are some pictures of my completed crossovers. You can see how the cap makes the board stand off the cup. Please don't mind the camera as it does not take good pictures. Use your imagination to fill in the fuzzies!
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  10. #10
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    5 hour burn-in update:

    I took my first real listen last night at the 5 hour burn-in mark (I haven't been leaving my equipment on all day to burn-in so it's only on when I've been home). The sound came across as a little less warm than pre-rebuild, edging on neutral. It is still a very good sound and is not sterile, but not quiet as warm as classic Polk. However, I expect this to warm up per previous experience once I get some more hours into the components.

    The sound has also cleared up a bit. The imaging and sound is a little more defined and a little more sharp than stock. It is not a huge amount, but it is noticeable and I am already enjoying the change. On the other hand, the dynamics seem to be about the same and I haven't noticed a difference yet. These Jantzens did not product hisses and pops on the first few hours of burn-in as some other cap do, but that doesn't mean that other ones won't.

    The rebuilding of the crossovers is already an improvement. The changes aren't overly pronounced as of now, but my listening session last night was enjoyable and I look forward to the development of the crossover components.
    Last edited by zingo; 08-15-2008 at 02:38 PM.

  11. #11
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    Late evening foam mod:

    I decided to put high quality 1/2" foam on the interior panels on my Monitor 5 Jrs last night because I was in the tinkering mood. I cut the pieces to fit in a few minutes, making sure that I didn't cut foam pieces for the front baffle. After test fitting the pieces, I used the fantastic 3M 77 to glue them all in place. (Note: make sure that you are spraying the glue on the foam pieces and then fitting them into the speaker cabinet, not spraying into the cabinet itself. Also, spray the foam pieces outside and away from your drivers and cabinets) I then stuck the cabinets in front of a big fan and let them dry for a couple hours. After replacing all the components and drivers in the cabinets, I sat down for a little listen to see what the results would be.

    I have read many reviews of sound deadening materials being used inside speaker cabinets with success. I started with the old "knock on the side of the cabinet" test. The results was not completely dead, as I was expecting with some 1/2" foam, but definitely reduced; only a very slight echo remained. From there I turned on one of my favorite albums, "Hiding Place" from a Christian vocal group named Selah. They are pretty well recorded both vocally and on the piano, as well as doing some great mixes with male and female voices. My first "foamed" impressions were a little more clear and defined. I can almost explain it terms of musical decay like you would have in a cathedral. This decay, or echo, had disappeared and left me with only the sound being reproduced, no extensions of it. The modification had not colored or changed the music in any other way, as far as I could tell last night. The bottom line is I accomplished what I was trying to do, improve the sound, and all with some foam and a little glue. Could I have used some more HIFI material and made a bigger difference, absolutely. But, I would have not been able to find out that so little could make a difference.
    Last edited by zingo; 08-15-2008 at 03:10 PM.

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    Nice write-up Zingo! I see what you mean about that big cap. Putting it on the underside of the board would have made it look cleaner and more stable.

    I've never tried fooling around with different sound deadening materials. Nice to see you are experimenting to try to improve the sound. Vintage and new Polk's are great speakers for the money. I'm always impressed with the "Polk" sound!
    Carl

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    20 hour burn-in update:

    The sound has improved a little more. Highs are clear and "sparkley", and the mids are smooth and more refined than before. However, the speakers are still a little bass shy. This probably has to do with the generally low burn-in hours, but I also have been playing a lot of pink noise, and not a lot of bass heavy music. This up coming week I will be hooking them up to a tuner and letting them play for the entire week. That should help the bass open up a bit and provide a pretty good final burn-in session. (since I've only been doing it on and off at this point) The sound is still very good and non fatiguing, but I'm just waiting for the bass to come out a little more. And hopefully it will, but this is my first experience with Jantzen caps so I'm not quiet sure what to expect...

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    150 hour burn-in update:

    Ahh, that's much better. For the last week and a half, I have had the 5Jrs hooked up in the garage with a "hip-hop old school" station playing that does a lot of 90's R&B and hip-hop to try to loosen the bass. It worked great and I think these speakers are about as burned-in or evolved as they're going to get. The highs are just a little more refined than before and very clear. The lows are more full and pronounced, and sounds very balanced now with the highs. The imaging has also improved a little and the sound stage seems wider with voices more easily placed. After the 150 hour mark, the Jantzen/Mills combo is definitely worth it for the $18.50 I spent on parts. They are a very good "budget" combination of components that performs well. After the number of modifications that I performed on my Monitor 5 Jrs, the sound is cleaner, more refined, and the imaging is better. With the price of a pair of Monitor 5 Jrs, plus the price of a few modifications, I would be hard pressed to find a better sounding pair of speakers for the money. I have Sonicaps in my 4.1TLs, but in the future when I don't want to spend a lot on caps, the Jantzen/Mills combo will definitely be used again.

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    Glad you're happy with the results.

    I don't know if I missed it above, but where/how do you use your 5jr's?

    Jay

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    I use them for my computer rig and I love it.

    Adcom Power Center -> PC with lossless audio via optical -> AMC 8 DAC via custom ICs -> K16LS tube amp via custom speaker cables -> RDO Monitor 5Jr

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    I am thinking of doing a complete rebuild on my jrs. The enclosures are a little deteriorated. A couple of scratches and the corners are not in great shape. I am debating about what to use for wood, either real wood or use the MDF and apply veneer.

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    I decided I'm also going to upgrade the binding posts as a last modification. I don't expect it will effect the sound, but it will look better and it's a cheap afternoon of fun. I might be using the ones pictured below, but won't be posting a follow-up review as I feel it would be pointless.


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    Nice write up and nice work!


    I can't wait to get these....


    There going to be for a garage rig.

    I just bought one of those Fatman or HCT tube Ipod thingys to power them with. Its only 13wpc but I think it will be fine for the garage. I also got a Polk XM radio for the source on the way.

    I think this is going to be a great garage rig. I am going wait to get everything and then set it up in the house first to see how it all works together. Then move it out to the garage. I'll give my impressions after I get all setup.

    I have a feeling I might not want to put this stuff in the garage... We'll see..




    Nick




    Nick

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    I just picked up a pair of these as well, and am intending to do a similar crossover and tweeter upgrade. I am also planning on powering with a Dared MP5 integrated amp (mine's branded Sonic Integrity). This rig will be for office use.

    I'm interested in your impressions of the combination of the modded Monitor 5jr+ with the Dared amp?

    Dawg

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    Quote Originally Posted by Big Dawg View Post
    I just picked up a pair of these as well, and am intending to do a similar crossover and tweeter upgrade. I am also planning on powering with a Dared MP5 integrated amp (mine's branded Sonic Integrity). This rig will be for office use.

    I'm interested in your impressions of the combination of the modded Monitor 5jr+ with the Dared amp?

    Dawg
    I run my 5B's with a Dared MP5. Outstanding combo. The only thing you might notice is a slight lack of dynamics for really dynamic music. The amp section just doesn't have quite enough oomph for really dynamic passages so you'll notice a slight softening in this area.

    You'll also might notice that sub bass region is non-existent, but then again 5Jr's don;t play sub bass notes anyways. In a larger room you won't get absolute volume either.

    Sounds like I'm only pointing out the negatives, but really for a 15wpc hybrid I'm sure you weren't expecting high spl or bottom rumbling bass anyway. With the right tubes............the Dared and M5 combo is pure sweetness and the sound stage height and width can be huge!! I refer to my secondary set-up as the mini SDA rig, the imaging is that good and bass is more than sufficient.

    You will not be disappointed.

    H9

    P.s. I bought Nick's HCT (Dared MP5) tube amp and I also bought a NIB for a spare I like it so much.
    Last edited by heiney9; 10-26-2009 at 02:00 PM.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

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    Quote Originally Posted by heiney9 View Post
    With the right tubes............the Dared and M5 combo is pure sweetness and the sound stage height and width can be huge!! I refer to my secondary set-up as the mini SDA rig, the imaging is that good and bass is more than sufficient.
    I'll be using the RCA's you sent me - what tubes are you using in it?

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    It varies..........but for now the same RCA's....which are Siemens made in Munich. I have a pair of Telefunken's I like very much as well. Recently got a pair of Amperex from Heerlen Holland which are still breaking in. Russian 6N1P's are great for rock and heavier music....they have better, more driving bass, but you don't get the great wide open soundstage. If I'm listening to alot of harder rock or harder driving music I put in the 6N1P's. For lighter music, vocal, jazz or even well recorded classic rock, etc it's usually a tube like the RCA or Tele that has that nice huge sound stage
    Last edited by heiney9; 10-26-2009 at 11:54 PM.
    "Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass

    Pass Aleph 30; Eastern Electric Mini Max; Adcom GDA600; MIT S3/Z Pc; SDA 1C; Squeezebox; Tubes add soul!

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