Monitor 5 - My First Speaker Upgrade!

ChiGuy

I’ve been a long time viewer of this forum and finally decided to do some of the speaker mod’s that I’ve been reading about. My original plan when I acquired a pair of Monitor 7’s was to have the crossover’s updated for me by one of the forum members that offered that service. Unfortunately when I reached out to him this past summer he advised that he had retired.

At that point I had to figure out plan B. After spending hours “studying” the various speaker mod thread’s on this site I came across one that was the catalyst that broke my “lack of confidence” logjam. Thanks to @plastic_avatar for his thread titled My 5B - In Mod We Trust. It was his post below in italics and specifically his comments in bold that hit a chord with me and got me moving!

- Worried you don't know enough to upgrade a crossover?
Relax! You can, and everyone here will help you get started.
- Thinking you can't swap out tweeters or terminal plugs, make custom cables, or rewire innards?
C'mon! You can refurbish a crossover! I told you so! This stuff is a breeze. All the info is in these forums!
- You want to jump off the pier and swim in the sea of madness, but worry you'll drown?
You'll live! Swim! Swim, you sweet, frelling wonder! Fly your freak mod flag and dive, dive, DIVE!

There are modding maniacs here, from royalty to street gangs, and you'll find support. From safe mods to strange mods, you do you- you'll live (they're just old, consumer-grade speakers, not a crate of undiscovered Rembrandts).

With that inspiration I decided to give it a go on my own! I wanted to get some experience doing these modifications so I would be more proficient when I did my M7’s. I had picked up a pair of Monitor 5’s for $25 so I did the mods on them with plans to gift them to one of my kids or use them in a 2nd system.

I didn’t do all of the suggested mod’s. I didn’t replace the inductors or the internal wiring and I didn’t replace the speaker terminals. I purchased an inexpensive set of speaker terminals from Parts Express but I was too anxious to test out my completed crossovers so I decided to postpone that mod.

This is a summary of what I did including pictures and links to some reference posts. Hopefully this might help anyone else that is looking to do the same thing but are a little hesitant to do this on their own like I was.

ChiGuy

1. Magnet shift prevention - JBWeld or Loctite Powergrab

This is the first thing I did. I’ve taken the advise of many people on the forum and didn’t want to risk having a speaker lock up. The link above is one of many discussions on the topic. There are a lot of comments about which glue to use. Some people tried Loctite PowerGrab because it was easier to apply. I decided to use JB Weld which is also highly recommended. Hopefully I applied enough glue on them! I glued the bottom side first and then created a simple jig to hold the speaker to make it easier to glue the top side.

ChiGuy

2. Damping Speaker Baskets - Dynamat

This is another straightforward modification and it makes sense to do. I did it on each MW and the PR. Dynamat can be cut with a scissors so its easy to apply. From what others have said you don’t have to cover every inch but you can if you want. I purchased a 12 in x 36 in sheet from Amazon for $65 which should be enough to do several speakers. I probably should have covered the complete back of the PR but for some reason I didn’t want to cover the original stickers!

ChiGuy

3. Hurricane Nuts

This is another mod that’s pretty easy to do. The link above is one of many discussions on the topic. I followed the process described by @WestMassGuy which I’ve shown in italics below. The only real difficult thing I ran into was having to remove some of the factory glue for some of the holes in order to seat the H nuts properly. I used a utility knife to cut the area out. There are probably better ways to accomplish this but this brute force method worked for me.

“The hole size is 13/64" for the 8-32 size nuts. Don't drill out the holes with that size immediately. I use three drill sizes to enlarge the hole gradually. Start with 1/8", then 5/32", finishing with the 13/64”.

To set the Hurricane Nuts, I use a small 1/2" diameter washer, and a couple of sacrificial screws. Put the washer under the head of the screw, hold the hurricane nut to the back of the hole, manually start threading the screw, and finish with the drill with a Phillips bit in it. Use low speed, and you'll know when the Hurricane Nut is seated by the sound of your drill. The washer helps prevent the screw head from sinking too far into the particle board as its pulling
the Hurricane nut up into the hole. The H Nuts should be installed on the Tweeter, Woofers, and Passive Radiator. You do not need to install them on the Binding Post Cup. The Cup only receives air pressure fluctuations, and doesn't produce any mechanical stress like the other components do.”

ChiGuy

4. Seal Cabinets

Many members reseal their speaker enclosure by applying a bead of silicone sealer/adhesive in all the corners. I assume they do this over the existing glue in the cabinet in case anything has separated from the wood. That’s what I did and I used Loctite Power Grab for this. I did find that some of the front sections are hard to reach from the speaker terminal opening and if you go in from the front you’re working blind.

5. Monitor 5 Tweeter Replacement

Before I did any modifications I listened to the speakers and I noticed that one of the existing SL 2000 tweeters didn’t sound as loud as the other. It was in Spkr B which had some damage to the top right of the cabinet. I’m not sure if it was related. In any case I swapped tweeters and the issue followed the tweeter so I assumed that the tweeter from Spkr B was bad. I had planned to upgrade the tweeters to the RD0194-1 tweeters so this didn’t really matter. I purchased the replacement tweeters from Midwest Speaker Repair.

ChiGuy

6. Crossover:

Updating the crossovers was the mod that caused me to hesitate doing this on my own. Once I decided I had nothing to lose I was all in. This mod was a little challenging but it also ended up being the most fun. I wanted to use the existing circuit board so the challenging part was figuring out where to put the new components. I created some masonite riser boards and purchased some standoffs to give me a double decker set up but in the end I decided not to use it. I’ll probably use that approach for the M7 upgrade.

I purchased ClarityCap CSA for the 12uF tweeter capacitor and ClarityCap PX for the 34 uF from HiFiCollective. ClarityCap doesn’t have a 34uF, only a 33 uF so I paid for the matching service and asked them to pick two as close to 34uF as they could. I ended up getting a 33.65 uF and 33.61 uF which is within about 1% tolerance of a 34uF. For my M7’s I’ll probably use Sonicaps with the exact values but for these I wanted to keep the costs down.

I used 12 W Mills resistors, a 2 ohm for the crossover along with a 0.5 ohm resistor to replace the Polyswitch. I purchased those from Parts Express.

I checked the values of original components. On Spkr A the 34uF cap measured 35.41 uF and the 12 uF cap measured 12.72 uF. On Spkr B they measured 36.24 uF and 13.26 uF. The resistors both measured 2.1 ohms. One poly switch Spkr A measured 0.7 ohms and the other one Spkr B measured 2.0 ohms.

ChiGuy

I initially had the capacitors set up so both would touch the pc board as shown in the M5_XO Layout1 an and b pictures. I inserted all the components but I didn’t solder them in. I thought I had the puzzle solved. I checked to make sure the crossover would fit in the cabinet but unfortunately it didn’t. You can have a capacitor hang over the edge of the pc board a little and still fit in the cabinet but in my initial layout they were hanging over the board in two different spots and that didn’t work. I can tell you from experience that the VHB tape holds extremely well. I had to remove one capacitor from the board and then remove the tape residue. Luckily it hadn’t been on there too long. I had to figure out a different layout. I started searching for more crossover pictures to see how other people did their crossovers. I found this thread by @Heiney9 and saw his crossover pictures. That led to layout #2 which is what I ended up with. As it turns out this layout was similar to what many others have done when using the same pc board.




The larger 33 uF ClarityCap PX capacitor is on the edge of the board secured by VHB tape. It’s leads had to be bent under the cap to get to the pc board holes underneath it. The PX leads are only 2 inches long compared to the 3 inch lead on the CSA. It was a close fit with all the bending! Because of that and because of how close the leads were to the speaker lead connection on the board and the 0.5 ohm resistor I used shrink tubing on the leads of both caps. The 12 uF ClarityCap CSA is in between the inductor and the 33 uF cap. It is secured to the 33 uF cap with VHB tape and a plastic tie wrap. Everything was very solid before I soldered them in.

The resistor leads also had to be bent under the resistors to get to the pc board holes underneath. This caused them to be raised above the pc board.




Initial Layouts

ChiGuy

Components inserted and ready to solder



Components soldered

ChiGuy

Completed crossovers

ChiGuy

7. Results

Good news, they work!





I think the best indication of how they sound is that I’m still listening to them! I took my main speakers out and put the M5’s in about two weeks ago. The first time I set them up before any modifications I listened to them for an evening but took them out the next day. I couldn’t wait to get back to my main speakers. I’m not in a hurry to switch them back. I’m actually amazed at how good the updated M5’s sound. I’m impressed by both the mid range clarity and the nice top end. They don’t get as low as my M10’s but I didn’t expect them to. However there’s more bass than I expected and it is well defined. The original speakers sounded like they had a blanket over them so its definitely been a big improvement. I’ll spend some more time listening to them with a variety of music.

This was a fun learning project for me. I accomplished my goal of updating a set of speakers and getting experience doing some of these basic mods that have been shared on this site.
Please let me know if there is anything you see that I should have done or could have done better.
My Monitor 7’s are next on my list!

F1nut

Nicely done, congrats!

Toolfan66

Nice job!!! Enjoy!!!

xschop

"However there’s more bass than I expected and it is well defined."
Put a 1" dia. wooden dowel front to back between midwoofer and PR. You'll have to offset it laterally to clear the x-over in the rear. Do this and the mid-bass tightens up. Great job on these.

Gardenstater

Nice work! After you have listened a while and have had their sound signature imprinted on you, I would definitely do the internal wiring. It wasn't great to start with being PVC insulated 3N copper and by now even though it is protected inside a speaker box, has experienced some oxidation. I did my tweeter wiring separate to the crossover mods, and also the fuseblock/binding post wires separate to that, and I can attest to the improvements. I would at least go with polyethylene or teflon insulation and 4N wire or better.

plastic_avatar

What a great write-up and fantastic documentation on your project!

Well done!

[M5 high five]

ChiGuy

F1nut wrote: »

Nicely done, congrats!

Thanks F1, I really appreciate that.

Toolfan66 wrote: »

Nice job!!! Enjoy!!!

Thanks Toolfan

ChiGuy

xschop wrote: »

"However there’s more bass than I expected and it is well defined."
Put a 1" dia. wooden dowel front to back between midwoofer and PR. You'll have to offset it laterally to clear the x-over in the rear. Do this and the mid-bass tightens up. Great job on these.

Thanks xschop!
I'll add that one to my list. I know I've seen some pictures of modded 5's and 7's with internal bracing on the forum.

ChiGuy

Gardenstater wrote: »

Nice work! After you have listened a while and have had their sound signature imprinted on you, I would definitely do the internal wiring. It wasn't great to start with being PVC insulated 3N copper and by now even though it is protected inside a speaker box, has experienced some oxidation. I did my tweeter wiring separate to the crossover mods, and also the fuseblock/binding post wires separate to that, and I can attest to the improvements. I would at least go with polyethylene or teflon insulation and 4N wire or better.

Thanks Gardenstater.
That's another mod I'll have to do some more research on. Now that I've tackled a couple of crossovers it doesn't seem that it would be too difficult to do!

ChiGuy

plastic_avatar wrote: »

What a great write-up and fantastic documentation on your project!

Well done!

[M5 high five]

Thanks plastic_avatar!
And thanks again for your inspirational post that finally got me moving with this upgrade!