Monitor crossover rebuild questions

Kryten

I have a pair of Monitor 5b apart to be followed by two pair of 7s.
The crossover board is a) connected to the inductor and input terminals, b) made with electrical traces on one side. I am planning the TL mod with new binding posts for all the speakers.

I previously used a 4 1/4" hole saw to make a couple dozen round riser boards to accommodate the larger SonicCaps. The magnets have been powergrabbed, the cabinets have been resealed, the Drivers and PRs have been dynamatted. I have the hurricane nuts, washers and screws. The tweeters will get oval head, no washers. When I move on to restoring the 7s, I have Loctite 290 on order.

Can you guess my questions?
1) Where do I start? Take pictures, mark the board and unsolder the inductor wire?
2) Am I using the traces and putting some components back in the same place? Will the traces take the heat of solder removal and reapplication?

Looking at threads on here (like these):

https://forum.polkaudio.com/discussion/149215/monitor-10-rebuild-with-tl-mod

https://forum.polkaudio.com/discussion/comment/2139304#Comment_2139304

It looks like they used the original board for the bottom layer. I could use two homemade boards and make all solders wire to wire and skip trying to use the traces and have more flexibility.

3) I have armacell to create gaskets for the drivers, PRs and binding post cup. The tweeter gaskets are intact. Many say just reuse them. Opinions?

4) what am I forgetting?

pitdogg2

you may need to get creative to fit the new caps. The boards are not worried one bit about heat, they will take it fine. No need to worry about lifting traces or pads ..well unless you throw them in a fire but you normal 750 degree solder will be fine. use whatever gaskets as long as they are not torn they should be fine. I'd do one board at a time so you can at least use one for reference if need be. go slow be methodical.

skrol

If interested, here is my Monitor 5B Update. https://forum.polkaudio.com/discussion/comment/2627864#Comment_2627864

Kryten

Thanks guys

Kryten

I am dry fitting all the components for a Monitor 5 SL2000 -> SL3000 / TL Mod RD0-198. I'm considering leaving the connections from the terminal cup-mounted 1.55mH coil as they are, one on the terminal and one on the original crossover board and then running wires down to a perf board mounted to the floor of the cabinet. Even though V3R and others have hung all the parts off the cup on riser boards, I am leery of the weight and it is dang tough fitting everything on two round boards. So.... I figure the only "long" wire runs (14 gauge) will be from the inductor down to the bottom and then back up to the drivers. I can't think of a good reason not to make the construction easy and reproducible. I have two pair of Monitor 7s to TL mod next so this is proof of principle.

Comments???

Kryten

dang, I just realized I had already posted that last in another thread.

Gardenstater

I don't know if this helps you because I didn't attempt any TL mod for my Peerless 7B's (no need to) but I was able to pretty easily fit the larger caps on my PCB. I'm not clear on what components you will be mounting on the auxiliary board on the floor of the speaker cabinet. I think I could've added a 3rd capacitor on top of the other two, with some sponge rubber and proper cable ties.
The weight isn't really that much when properly supported.

Gardenstater

Too late to edit my post. Anyway, I just thought to add that you could upgrade from the cheezy nylon clip type standoffs for the pcb to the ones I have which are aluminum hex stock tapped at both ends for aluminum screws. You could probably use non-magnetic stainless or brass as well.

Kryten

Your recap looks quite neat and tidy. I do have other standoffs I can use which are stronger to better support the new parts. The difference between the 7B schematic and the 5B SL3000 "TL Mod" to allow use of the RD0-198 tweet is the tweeter inductor gets replaced and to get the DSR close, an additional series resistor is needed. A new cap is then added to the tweeter circuit along with a resistor to replace the polyswitch. The other caps and resistors are the same as what you replaced using the larger SonicCaps. I could certainly just stack and make it work.

What I also wasn't fond of was trying to fit all the leads down to the original board or using jumpers to get up to the riser board. It's not difficult to drill additional holes and solder, it was more protecting all the leads with shrink wrap and routing them to the proper solder areas. I got to thinking if I have to jumper up to the second riser board, why not jumper down. Because I'm using the original 1.55mH inductor on the terminal cup, it's really easy to leave it landed on the original crossover and go from there.

So yea, I'm still thinking, weighing options. Thanks for the input!

Gardenstater

If you do the tl mod for the 7, which I think will require a different value low pass inductor, you may actually have to use an additional board. We don't actually have a schematic for the 7B in the archives. Personally I will just stick with my Peerless tweeters and be happy with that, never having heard the rdo-198-1's. Would be nice to hear a pair of series II's with those tweeters to compare, but it would be apples and oranges to some extent, since MW's are different as well. For the 5 if you could find the same gauge inductor the dcr may be close enough. I take it all the audiophile inductors on the market would be larger gauge though? Would it be possible to remove or add some turns to the existing inductor to get it to the new value?

Kryten

I have two pair of 5s and two pair of 7s, all with SL2000 tweeters, no Peerless tweets unfortunately. I will probably sell the 2nd pair of 5s after I epoxy the MWs but with the original crossovers.

I was under the impression the low pass inductor on the terminal cup remained the same when going to the TL Mod. I see the high pass inductor changes from 0.23mH to 0.27mH for the SL3000/RD0-198 mod. The high pass inductors I bought are Jantzen 255-216 from Parts Express. The specs are 0.27mH, 0.23ohms, 18 AWG so not too large. I then add a mexican Mills 0.27ohm resistor to get back to the 0.5ohm DCR specified. The extra caps and the size of SonicCaps makes the fit challenging.

I have no idea if the 7B was when they changed the low pass circuit to 1.75mH and 0.27uF or if that was done in the last 7s II iteration for which we do have a schematic. Maybe the cabinet was a bit different or they moved the tweeter crossover point. why do you say the MWs are different?
my 5s have MW6502s and all the schematics I've seen have that P/N. I'm learning.... SLOWLY.

Gardenstater

Kryten wrote: »

I have two pair of 5s and two pair of 7s, all with SL2000 tweeters, no Peerless tweets unfortunately. I will probably sell the 2nd pair of 5s after I epoxy the MWs but with the original crossovers.

I was under the impression the low pass inductor on the terminal cup remained the same when going to the TL Mod. I see the high pass inductor changes from 0.23mH to 0.27mH for the SL3000/RD0-198 mod. The high pass inductors I bought are Jantzen 255-216 from Parts Express. The specs are 0.27mH, 0.23ohms, 18 AWG so not too large. I then add a mexican Mills 0.27ohm resistor to get back to the 0.5ohm DCR specified. The extra caps and the size of SonicCaps makes the fit challenging.

I have no idea if the 7B was when they changed the low pass circuit to 1.75mH and 0.27uF or if that was done in the last 7s II iteration for which we do have a schematic. Maybe the cabinet was a bit different or they moved the tweeter crossover point. why do you say the MWs are different?
my 5s have MW6502s and all the schematics I've seen have that P/N. I'm learning.... SLOWLY.

Sorry I never replied. I think a tl mod will be difficult for the 7C. The 7C to 7 Series II is when they upped the low pass inductor from 1.55mH (18awg I think because my 7B is 0.038" dia.) to 1.75mH (18awg), so you will have to extend the magnet wire windings and try to get it to 1.75mH or abandon it and get another large inductor and mount it somewhere in the cabinet.

The 7B which I have that shipped with Peerless tweeters and then later for a brief period with SL1000 had the MW6500 driver (not MW6502). In my case doing a tl mod for that would also therefore entail having to get MW6502s.

Kryten

Thanks for the info. I will keep y'all apprised of findings and progress.

Gardenstater

Having said that, the tl mods for the 5B and 10B (SL2000 models) did not entail changing out the 1.55mH inductor, to use the SL3000 tweeter. We don't seem to have a SL3000 mod schematic for the 7C but maybe those could be extrapolated to something for the 7C that would work without changing out that large inductor? Has anyone here tl modded a 7C?

westmassguy

Gardenstater wrote: »

Has anyone here tl modded a 7C?

Dozens of times using the Monitor 5b SL3000 Schematic. Works perfectly

Gardenstater

westmassguy wrote: »

Gardenstater wrote: »

Has anyone here tl modded a 7C?

Dozens of times using the Monitor 5b SL3000 Schematic. Works perfectly

Next question is has anyone compared the tl modded 7C with RDO-198 to the 7B with Peerless, with upgraded crossover components ?

gp4jesus

What’s the “TL” mod?

pitdogg2

gp4jesus wrote: »

What’s the “TL” mod?

The ability to use SL2500,3000 and RD-0198 tweeters correctly.

As in SDA 1.2tl, 2.3tl, CRS & 2btl

xschop

....RTA 8TL