New to me Monitor 7 and 5

DeRod

F1nut wrote: »

3M 300LSE

Thank you! I'll give that a shot before trying the stinky glue

Gardenstater

Here's a couple of repositionable/temporary ones that might be worth a try and they are from Aleenes:

https://quiltingthread.com/products/aleenes-tack-it-over-and-over-repositionable-glue-4-ozaleenes-tack-it-over-and-over-repositionable-glue-4-oz

https://quiltingthread.com/products/aleenes-no-sew-temporary-fabric-glue

The removable gummy glue hot melt types require a special low temperature hot melt glue gun. I don't know if you could just put a speed control on a regular one and throttle down the temperature, or if the glue sticks are available in a size to fit the regular guns.

DeRod

Well I got so into into my 7s that I haven’t done anything with my 5s yet. This evening I decided to start looking into the 5s.

First thing I noticed was the poly in this box was different from all my other Polks. It completely filled the box and was nicely cut out, not rolled up behind the tweeter and MW. It goes all the way to the bottom filling behind the PR.

Also I noticed the crossover was slightly different with a 6.2 ohm resistor. I thought I had everything needed to refresh that crossover but that 6.2 was a curveball I didn’t expect.

Just checked and parts has a Jantzen 6.2 .. I guess the crossovers will have to wait till next week when the resistors arrive. Mean while going to start putting in hurricane nuts in preparation

DeRod

The crossovers on these also had metal standoffs not the plastic one they started using later. The inductor isn’t glued or zipped tied.

Gardenstater

It is interesting to me that it "appears" that the tweeter cap is another TSI electrolytic. But if so, it would be odd that it is larger than the 34uF 🤔 Is the tweeter cap 12uF like in later crossovers?

The 6.2 Ohm tweeter resistor is of course interesting as well. Have you had a chance to check the DCR of those Peerless to see if Polk may have been correcting for ones that had a lower than the usual 7.8 Ohm?

DeRod

Yes 12 & 34uf just like all the others. Just wasn’t expecting the 6.2ohm resister. After digging around the the forum here I did see a couple of other folks had these same crossovers in their older 5s with that 6.2 as well.
I didn’t notice any of the other model 5 crossovers with the metal standoffs like these though. The crossovers don’t have a date, but the back of the woofers from the same speakers are dated 11-1978.

DeRod

I will check the tweeters tonight and post results.

I also noticed the other 5s with the same crossover as these had the same pant leg type poly inside. It seems as though that these had twice the amount (2 pant legs) in each speaker from the top to the bottom behind the PR. The boxes are basically stuffed. If you try rolling up the pant legs behind the MW its far too tight. If I remove one from each speaker then I could roll it up like you normally would on all the other Polk speakers.

DeRod

The serial is on the paper tag not a label on the crossover.

Gardenstater

Another possible explanation for the 6.2 ohm (rather than 4.7 or 4.5) could be that the Gefco Mfg. drivers were less efficient than later ones. "If" they had copper plated pole pieces they could be less efficient.

DeRod

Both tweeter 8.2 ohm but notice they have slightly different caps on the magnets.

The tweeters in the 7s are both the same.

DeRod

Woofer and tweeters from the 5s ☝️

VSAT88

Not all that unusual from what I have seen from buying multiple Polk vintage speakers. Some were that way from the factory. Using up older parts in newer production speakers. Hey! Look! we have another box of mid woofers sitting over here in the very back of the storage room! Some times owners change them out if they blow them and have no clue except if it fits then there you go. No care as to model number, specs, whatever. Then you have the cruel ones that know its the wrong speaker and put em in anyway just to sell the. Whats the old saying??? Buyer Beware!

Gardenstater

Comparing schematics for 5B vs 7C, both having the same MW6502 + SL2000 drivers, the schematics are the same except for the 5B not warranting the mylar tweeter capacitor and getting an electrolytic. So the question would be why are the schematics for 5A vs 7B different when they both have the same MW6500 + Peerless? I'm assuming the only difference is the tweeter resistors (6.2 Ohms vs 4.5 Ohms) but what if there are inductor differences, especially in DCR?

Maybe you could check the DCR of the MW inductor.

DeRod

Question - would a Jantzen 18uf + 16uf to equal 34uf be good idea or just a single 33uf ?

pitdogg2

Either would work.

DeRod

pitdogg2 wrote: »

Either would work.

Once again thanks for your advise. I didn’t want to make the same mistake as with the 7s when you pointed out making a more even split would be better.

I’m going to give the Jantzen 18+16 a shot and use an Audyn 12uf with Jantzen resistors for the Monitor 5. The only thing I’m missing is the 6.2 resistor which is already on the way to me. I’ll probably start on these tonight

DeRod

Still waiting on the resistors to arrive. Did some Dynamat and hurricane nuts meanwhile.