Still searching for an air core inductor...

AFEuphman

Hello all!

First off, thanks again for all the great onformation on the forums... Wow, what a resource! Now, some of you may know my travails in getting my "free to me" CRS+ speakers up and running, fully. I've had them working for a while, but have always wanted to get them "back to spec". The right speaker had suffered a fall and the crossover was damaged (since replaced, thanks to Ken!) and the big air core inductor was splayed out all over the place. I replaced it with a parts express Frankenstein of two inductors, but I REALLY want to find an original.
I posted a request in the classifieds, but got only a slight bit of motion. Recently I had a lead that just hasn't quite panned out. So, I've decided that the rash of inductor upgrades MIGHT net me one!

So, here is my request: if anyone has an extra, large air core inductor from a CRS+ (or a 2B, as I understand...) that is extra, please let me know! I would be happy to purchase it from you!

So, there you go! Thanks so much in advance, and thanks for all the great info already delivered!

drumminman

AFEuphman wrote: »

Hello all!

First off, thanks again for all the great onformation on the forums... Wow, what a resource! Now, some of you may know my travails in getting my "free to me" CRS+ speakers up and running, fully. I've had them working for a while, but have always wanted to get them "back to spec". The right speaker had suffered a fall and the crossover was damaged (since replaced, thanks to Ken!) and the big air core inductor was splayed out all over the place. I replaced it with a parts express Frankenstein of two inductors, but I REALLY want to find an original.
I posted a request in the classifieds, but got only a slight bit of motion. Recently I had a lead that just hasn't quite panned out. So, I've decided that the rash of inductor upgrades MIGHT net me one!

So, here is my request: if anyone has an extra, large air core inductor from a CRS+ (or a 2B, as I understand...) that is extra, please let me know! I would be happy to purchase it from you!

So, there you go! Thanks so much in advance, and thanks for all the great info already delivered!

I'm pretty sure that many more Polks than the CRS+ and 2B use the same large 16 mH inductor, so don't limit your search to those models.

AFEuphman

That's certainly good news... that should increase my odds! This is where my knowledge shows itself as more limited. I'll take a look through some of the wiring schematics and see if I can come up with more sources.

As an aside, I see that you are from NC... I'm on tour with the Heritage of America Band from Langley AFB right now. We are in the middle of a week long series through NC... We just played at Elon University, today we play at the Greensboro Coliseum, then we head to Winston-Salem and finally finish up in Morganton. I used to live in Asheville and its great to get back down here...beautiful!

inspiredsports

When I upgraded the 16mH inductors in my 2B's, I did them incrementally, meaning 1 speaker had the factory 16mH hooked up and the other had the new inductor in place. The sound was fine.

One thing that was pointed out to me is that both are in the "same circuit" when the SDA interconnect is connected. You could actully use any combination to get the the right inductance value (a total of 32mH in your case), including a single 32mH inductor.

Additionally, in my case I used 2 8mH inductors wired in series in each cabinet to get the required 16mH value per the suggestion of my new inductor vendor.

Don't get caught up in thinking you need identical coils in each cabinet. Mixing and matching brands is not necessarily a bad thing. Additionally, replacing the original late '80's inductors in SDA's with modern audiophile grade incuctors is currently a hot topic here at Club Polk. The replacement you have in there might actually be better than the original.

AFEuphman

Oh wow! I did NOT realize that! If that is true, then maybe it's not such a big deal, after all... I think I'll still be on the lookout for an original, just for my own OCDness. I guess what has really driven me to find an original replacement is the fact that there is a subtle, but noticeable difference in character between the left and right speakers. First, the right speaker has always played a little less loudly (that's th one that has needed the repair). Everything else SEEMS equal, except the inductor. Now, as I type this, I'm thinking that maybe I need to be getting some other ideas... Second, the right has seemed a bit warmer, if maybe slightly duller.
I first attributed all this to the receiver I was using, but now I have a nice Carver unit and, while everything sounds better, the differences still remain.
I know that right speaker suffered some sort of fall that knocked the inductor off, splayed it, and broke some solder points on th original crossover. Should I be looking at magnets or something else?
Wow, thanks again for all the help guys!
John

inspiredsports

With power off . . . Have you gently pushed (and held) the passive radiator in about a half-inch and watched the 6.5" midwoofers extend outward. They should take between 3 and 5 seconds to recede. If they don't slowly recede, you could have and air leak that would cause reduced sonic performance.

Also, (again with power off) if you gently push the passive in and quickly let it back out several times and hear any scratchy noises from the 6.5" midwoofers, that would indicate "magnet shift" and could definitely compromise sound quality.

In a hard fall, it's almost a given that you get magnet shift with these older drivers as the glue that holds the magnet in place is dried out and no longer supple.

AFEuphman

Well, now this gives me something to think about. I don't get home until Wednesday, but once the wife heads out to school Thursday morning, that speaker and I are going to spend some quality time together. I had wondered about the possibility of an air leak, and had read a bit about magnet shift and pondered... I didn't realize that the passive would give me such a great way to test for it all!

So, as another way to do a little testing... Could I disconnect the interconnect cable and essentially eliminate the large air core inductors from the circuit? Or would that cause them to work independently?

inspiredsports

So, as another way to do a little testing... Could I disconnect the interconnect cable and essentially eliminate the large air core inductors from the circuit? Or would that cause them to work independently?

Yes, the two outermost 6.5" midwoofers ("SDA" or "dimensional" drivers) and components in that circuit (including the 16mH inductors) would be completly de-energized and out of the circuit.

You would only be powering the tweeters and two inner-most stereo drivers.

If it's an air leak, the sound from the "leaky" speaker would still be worse.

Keep track of your findings and post them here, and we'll have those SDA's singing in no time.

AFEuphman

Absolutely! Will do, and thanks for all the help!

evhudsons

In a hard fall, it's almost a given that you get magnet shift with these older drivers as the glue that holds the magnet in place is dried out and no longer supple.[/QUOTE]

Dropping my CRS+ speaker is what started my new path to upgrading the speaker. the magnets on both drivers separated. I put them back and thought I was ok, but realized upon listening that they weren't good at all. I had to buy new replacements from Polk Audio. I got the mw6511 and the mw6510


I would agree with the quote in that I would assume you have driver problems with the shift. It's not the end of the world, it can be the beginning of wonderful new things!

AFEuphman

As soon as I get back home from this tour, I will start checking all this out. Thanks for all the great info !!!

AFEuphman

OK, back from tour and I've been working with the speakers... I did the PR push test, and indeed the right speaker seems to let the MWs recede back in just a bit faster. It's hard to tell how much quicker... both speakers seem to be "around" 2 seconds. I've been reading up on different sealing methods and will probably head out to get some moretite. I'll get to the speakers themselves, but I think I had better run a bead inside the box itself where all the angles are (corners, etc...). I'll work only on the right speaker so I can compare. In trying this stuff out, I think I may have made it a bit better already... that tells me the seal for the PR is probably questionable, as it's the only part I've messed with (came off when I removed rear grill). I have some brand of speaker sealer that I may try on it first, as it release pretty easily... we'll see!

evhudsons

I just installed my Solen inductors and they sound great already!

But...I did the press test as mentioned above and it failed on both speakers. It only held for about one second. I could hear a swoosh. One swoosh came from the passive radiator and the other from somewhere up front on a driver but I couldn't tell which one. Upon closer inspection I saw how some of the rubber surround was coming loose from around the screw. It is one of the newer mw6511 from Polk. I thought I had cut out enough rubber around the screw, but some of it got caught in the screw as I turned it and it must have pulled some of the rubber loose. Is this fixable? Otherwise I'll have to replace it and be much more careful installing.

on the passive radiators I had some of the particle board come loose during the installation of the rings. I put mortite around and in the holes to seal it up better. I put in four screws for the pr, then put on the cover and the other four screws. I'm wondering if I should put something in the screw holes as I'm inserting them. I think I have that done pretty well now, but the drivers are still leaking air.

evhudsons

Another spot I found that could be an issue is there is a little black cap on the back of the speaker. I popped one loose as I was curious as to what it was. It was a small hole drilled through into the cabinet. I put the cap back but thought I might put mortite in the inside to help seal it up. I have no idea what that is but it may have had something to do with leaking air.

inspiredsports

I wish F1, DK, etc. would chime in, but that fast retract time would indicate you have less than perfect midrange/bass response.

The passive radiator reacts/moves based upon the mids building up sound pressure inside the almost 100% sealed cabinet you have with a longer retract time.

Our three favorite sealing methods are new gaskets from brgman, Armacell or Mortite (probably in that order) and Larry's rings are the icing on the cake AND the cherry on top all in one.

drumminman

evhudsons wrote: »

I just installed my Solen inductors and they sound great already!

But...I did the press test as mentioned above and it failed on both speakers. It only held for about one second. I could hear a swoosh. One swoosh came from the passive radiator and the other from somewhere up front on a driver but I couldn't tell which one. Upon closer inspection I saw how some of the rubber surround was coming loose from around the screw. It is one of the newer mw6511 from Polk. I thought I had cut out enough rubber around the screw, but some of it got caught in the screw as I turned it and it must have pulled some of the rubber loose. Is this fixable? Otherwise I'll have to replace it and be much more careful installing.

on the passive radiators I had some of the particle board come loose during the installation of the rings. I put mortite around and in the holes to seal it up better. I put in four screws for the pr, then put on the cover and the other four screws. I'm wondering if I should put something in the screw holes as I'm inserting them. I think I have that done pretty well now, but the drivers are still leaking air.

You can reattach the rubber surround to the frame with one version of Loctite's super glue. I think it's called Ultimate and it's formulated to bond like crazy, yet remain flexible. I bought it at Lowes.

Good luck!

evhudsons

thanks Drummingman!

I'll try that tonight and see how that responds. I had noticed that there was a lacking in the midrange. The bass had come back really well after the crossover upgrades and the mortite seals, but after installing the newer drivers and the rings I lost some of both. Now I know why. The rings were my fault, not of the rings or the way they were made. I did install very carefully but on the passives I had to widen up the holes more to get it to fit and some of the board simply crumbled. I'm pretty sure the mortite I stuffed in there did a good job to seal it back. I also had made a mistake in tightening the rings. I did not let it settle and then tighten by hand again. I got a lot more seal and tightness when I did that. So the only thing left I found was the drivers with loose rubber surrounds.

I overtigtened the tweeter on one speaker and the tweeter bracket snapped just a bit around the screw hole but it seems to still be solid all around the side and not contributing to the air leak. I stuffed more mortite in there just to be sure but if you do larry's rings which you should, be careful to not over tighten the brackets.

I'm still not sure what the black cap on the back covering a hole is for. I'm wondering if that is a good place to put in a cardas binding post instead of drilling a new hole by the sda connection?

Toolfan66

evhudsons wrote: »

I'm still not sure what the black cap on the back covering a hole is for. I'm wondering if that is a good place to put in a cardas binding post instead of drilling a new hole by the sda connection?

If it's about 3/4" in dia. it was for a SDA socket for the SDA cable..

Toolfan66

BTW seal the hole!!

evhudsons

LOl, I'm not super smart but I'm not pfb!

I sealed it already so it should be good. If I bypass the pin blade connection to use a single sda cable would that be a good spot to use as it is predrilled? And why did they put that there if the pin blade connection was used?

I love history and I'm sure there is a reason for it.

AFEuphman

Haha! I was just about to ask about that plastic disc covered hole. I did the same thing... Curiosity had me pull it off and look. It's a perfect hole, centered on the bottom of the back panel.
I, too noticed whooshing coming form three of the four mw's on my speakers... After some listening, I determined it to be coming from the dust caps. I've since read that that is ok... Correct? It's funny, whatever they used to seal them to the cone is complete on one, so no whoosh on it. I was wondering what other's experience is with this...

evhudsons

By the way my Solen's really opened everything up. I can't give a full opinion until I fix my air seal leak and for the burn in, but I listened to the new versus old inductor and already it put a huge smile on my face.