Monitor 5B Update

skrol

I've had a pair of minty Monitor 5B sitting around waiting for be to do something with. I can do the obvious updates: RD0194 tweeters, nix the poly-switch, caps, resistors, damping, etc. However, I am wondering about the SL-3000 (TL) XO mod and using RD0198 tweeters.

Has anyone done the TL mod to the 5B?

If so, any idea how it compares to just going with the RD0194?

Thanks in advance
Stan

skrol

I’ve been playing with the RD0194 tweeters in the 5B. They are def more laid back than the SL-2000. But I can see why some like the SL-2000 for certain music. They work well with old Rod Stewart.

I presently have the RD0194 doing burn-in in prep for install.

skrol

Temporarily installed.


In the burn-in chamber as to not annoy my wife.

skrol

I have a pair of RD0198 and SL3000. I’m still wondering about the TL mod.

xschop

Although I have the 5.8uf caps on hand, I still haven't tried the TL mod. I can say that the 6x6 x 0.5" thick open-cell foam behind the MWs and 1/4 of the poly-fill removed is a nice improvement in midrange and bass extension. Mine play down to 32HZ all day.

skrol

Ok, I just pushed the poly-fill up from behind the MW and it got rid of some of the muddiness. Thanks. I have some sonic barrier that I can play with.

xschop

I followed what others have suggested and had the poly-fill up away from rear of PR, yet still behind tweet and MW. The foam sheet and lessened poly-fill cleans up the kick drums along with mids.
I listen to alot of jazz, old school and new, and am working on the tweeter adapter plates for the Morel MDT-29 and Dayton DC28f sticky domes (Morel knockoffs).

skrol

I have the poly-fill pushed up behind the tweeters. The bass seems much cleaner. Where did you put the foam sheet?

Cool about the Morel tweeters. I'd like to hear how it goes. They make some awesome tweeters.

xschop

I put the 6x6" foam sheet directly centered behind the MWs on the rear wall. Do you feel that the front baffle between MW and tweeter needs reinforced on yours?
Nice looking 5B's you have BTW.

skrol

Reinforcing? The cabinets seem very solid. I wasn't planning on any structural mods. Is this something that others have done?

xschop

Was just curious. I'm not sure if the 5Bs were particle board vs MDF. Mine seem ok as is but I think the area does exhibit some vibes on kick-drums at times.

skrol

Time for component selection. I figure that I'll go with Clarity Cap CSA for the tweeter networks. Previously I have used the PX with good results. They are a big step over the electrolytics. The CSA should be more so and the cost is reasonable.

The larger 34uF used in the MW network can get costly. I'm looking at Dayton or Jentzen Cross Cap unless someone has another economical suggestion.

I plan to nix the polyswitch. Therefore, I plan to replace the 2.0 ohm tweeter resistor with a 2.5 or 2.7 ohm resistor and put a jumper in place of the PS. I figure Mills 10W or Mundorf. Preference?

If I decide to to the TL mod, I will need to replace the 0.23mH inductor with a 0.27mH. I believe these are 22 awg but I haven't found any yet. I figure it is important to use the same awg to maintain the same ESR. Anyone know of a source or what the actual ESR should be?

skrol

xschop wrote: »

Was just curious. I'm not sure if the 5Bs were particle board vs MDF. Mine seem ok as is but I think the area does exhibit some vibes on kick-drums at times.

I believe it is thick particle board but they are very solid. Knocking on the cabinet gives no apparent resonance. Have you tried putting Dynamat on the MW and PR baskets?

westmassguy

skrol wrote: »

Time for component selection. I figure that I'll go with Clarity Cap CSA for the tweeter networks. Previously I have used the PX with good results. They are a big step over the electrolytics. The CSA should be more so and the cost is reasonable.

The larger 34uF used in the MW network can get costly. I'm looking at Dayton or Jentzen Cross Cap unless someone has another economical suggestion.

I plan to nix the polyswitch. Therefore, I plan to replace the 2.0 ohm tweeter resistor with a 2.5 or 2.7 ohm resistor and put a jumper in place of the PS. I figure Mills 10W or Mundorf. Preference?

If I decide to to the TL mod, I will need to replace the 0.23mH inductor with a 0.27mH. I believe these are 22 awg but I haven't found any yet. I figure it is important to use the same awg to maintain the same ESR. Anyone know of a source or what the actual ESR should be?

I would stick with the Clarity PX for the low Pass. Keep it all in the same family. A 12uf & 22uf will stack nicely.
Go with a 2.5 ohm Mills/Vishay Mills 12 watt.
The required DCR not ESR for the shunt inductor, is .5 ohms
The closest inductor I've found, is the Jantzen Air Core #000-1640 #22 gauge @ .49 ohms. Special order from HiFi Collective out of the UK

dromunds

I was also going to suggest going with the Clarity PX for the low pass. Stay with the same family.

skrol

Ok, thanks for the advise.

skrol

I know it doesn't give the 34uF value but what about the PX in 15uF + 18uF to get 33uF? This keeps them closer in value to each other and is well within the factory tolerance. Or would it be more important to have the 34uF total value?

xschop

I'm using 33uf caps on the MW circuit, mids and bass are outstanding. And yes I used the Butyl Mat on the MWs and PRs. You should Butyl Mat the rear face of the RDO plastic frames as well.

Gardenstater

I'm pretty OCD but I guess if I was going to go with 33uF, I'd try to ask the seller if they could give me caps that were towards the high side of their tolerances, if they do that. I think if they say +/- 5% it probably means that typically they are more like +/-2.5%, because the manufacturers give themselves some factor of safety. If you could get 33uF +3% that would put you right at 34uF.

westmassguy

skrol wrote: »

I know it doesn't give the 34uF value but what about the PX in 15uF + 18uF to get 33uF? This keeps them closer in value to each other and is well within the factory tolerance. Or would it be more important to have the 34uF total value?

You could go that way as well. It's a shunt cap. Not as critical as an inline component in the high pass circuit.

skrol

I believe the crossovers are done. I went with the PX 15uF + 18Uf to replace the 34uF, CSA for the 12uF and Mundorf 2.7 ohm 10 watt resistors. I found one of the 34uF were reading 39uF but worse, one of the polyswitches was reading 2.2 ohms vs the other 0.7 ohms.




I threw the first speaker together temporarily with the upgraded XO and played some music to test. I was amazed how nicely it blended with my upgraded RTA-11TL. Prior to the XO upgrade, even when I had the RD0-194 in the 5B it didn't blend well.

Next I'll make sure the cabinets are sealed well, DynaMat the MW and PR and glue the MW magnets.

westmassguy

Nice!

Faustin

Looking good. Did you end up replacing the poly switches or leave them out? I can't tell from the pictures.

wispolkboy

Wow, those look great. Big!

skrol

Faustin wrote: »

Looking good. Did you end up replacing the poly switches or leave them out? I can't tell from the pictures.

I took the polyswitches out, replacing them with a jumper. Since the resistors were in series with the polyswitches, I replaced the 2.0 ohm resistors with 2.7ohms to compensate.

DaveHo

I gotta ask the dumb question. Did you verify they fit back in? Looks to be pretty close!

skrol

They have a 1.5 inches clearance.

Damping material applied to the PRs

Magnets glued and damping material applied to the MWs

XO's mounted

All together again. Radiohead sounds magical.

Now time for break-in.

xschop

Nice job. The 5Bs are excellent sounding monitors for their size.

skrol

Even not broken in, they sound better than I expected. Much more dimensional, better tonal balance. They just sound right. XO upgrades are such a great bang for the buck improvement.

I probably should have posted all this in the DIY section. My next part is speaker stands. I have these that came with a pair of 5As. The original owner modified them making them taller. I’m not sure the tilt angle is the same as the original.

They aren’t the most stable things. I think I can make something better. Ideas?

tonyp063

https://forum.polkaudio.com/discussion/176797/finished-my-monitor-10b-stands

https://forum.polkaudio.com/discussion/183765/hybrid-monitor-7-stands

Gardenstater

You can't beat mass density for stability and that's why I chose concrete blocks for the bases of my stands. They could be spackled and sanded and painted matte black.

That extra stability can allow you to get the tweeter/midwoofs up at ear height at the listening position.