RTA15TL MW's with extra donut magnets

[brgman]

I am taking apart my 15's to mod.The first was non eventful but now that i started into the second every 6503 has an additional donut magnet stuck to the back of the standard magnet.
What is up? Why does one have these and the other not?
Has anyone seen this or maybe know why this is?:confused:

[comfortablycurt]

Hmm...Just taking a guess here, but they could be bucking magnets to make the speaker magnetically shielded. It's possible that at one time, the one speaker was sitting right next to a CRT TV and was distorting the picture. The magnets would have magnetically shielded the one speaker, so it wouldn't affect the TV's picture. If that is the case...the other speaker must have been far enough away from the TV to not impact the picture.

That's just a guess though.

[Toolfan66]

Pics!!!!!!

[ken brydson]

Hmm...Just taking a guess here, but they could be bucking magnets to make the speaker magnetically shielded. It's possible that at one time, the one speaker was sitting right next to a CRT TV and was distorting the picture. The magnets would have magnetically shielded the one speaker, so it wouldn't affect the TV's picture. If that is the case...the other speaker must have been far enough away from the TV to not impact the picture.

That's just a guess though.

I think that's it. A few years ago I ordered a new driver for one of my LS50's. When I questioned why it looked different than the original that was Ken S's exact response.

[brgman]

I'll get some pics to post...

[F1nut]

As CC stated, it's a bucking magnet. No worries, no need for a pic.

[brgman]

For those that are curious

[brgman]

just cannot figure why they put them in one and not the other.The guy i bought them from wasn't smart enough to do this himself.Hell he left another pair he had sitting in water rotting away.Didn't strike me as someone that cared.
Anyhoo.Thanks for the feedback.I guess i can keep these off for the modded version.

[Tour2ma]

Agree...

So they were in one, but not the other? Previous owner must've had one channel close to a TV...

If I remember correctly, the bucking mags do depress output ~1 dB, so you'll want to remove them.

Might make a good karma...

[brgman]

yep.consecutive s/n's also.

[F1nut]

If I remember correctly, the bucking mags do depress output ~1 dB, so you'll want to remove them.

I don't recall that. What I do recall is that there is the potential for a slight change in the driver Q. However, there are a number of folks who think that adding bucking magnets improves the sound quality of the driver.

You know all those speakers out there that state they are shielded? Yeah, they all use bucking magnets.

For example, Polk's LSi 15's are advertized as, "Magnetically Shielded
All models* are magnetically shielded for safe placement near CRT displays.
*Except LSiFX, but you wouldn't put your surround speakers next to your TV anyway…"

Yep, bucking magnets.

[dorokusai]

I wouldn't remove them as there's no real need to do so.

[Tour2ma]

I don't recall that. What I do recall is that there is the potential for a slight change in the driver Q.I looked into them for my SRS's (which ate a tv picture tube once... pretty colors...). Talked to Ken S. about the magnets and I am sure he said they drop the efficiency (sensitivity)...

What I'm not sure of is the amount, but it was slight, around 1 dB. This wasn't the reason I did not buy them. The replacement TV (a Proton) was shielded much better...

In any case I'd either add magnets to the speaker that did not have them, or remove them from the one that does.

JMO...

[brgman]

I guess what i need to nail down is which is more advantagous,with or without.i reckon polk cs still sells these.
i will be doing the dynamat and mortite as well when they get reassembled

[dorokusai]

Unless you've noticed a difference before you knew about the magnets, why bother? If it's that big of a deal just swap some drivers between the cabinets, that way at least you'll have some balance. Move two bucking magnet drivers over to the other cabinet and vice versa....problem solved.

[FTGV]

I don't recall that. What I do recall is that there is the potential for a slight change in the driver Q.A small reduction in the Q would be expected as would possibly a slight increase in sensitivity.

[brgman]

Unless you've noticed a difference before you knew about the magnets, why bother? If it's that big of a deal just swap some drivers between the cabinets, that way at least you'll have some balance. Move two bucking magnet drivers over to the other cabinet and vice versa....problem solved.

That's what i was thinkin'.Throw 2 of the 4 in the other for balance.:wink:

[Toolfan66]

Thats what I would do and forget about it..

[Tour2ma]

FAGEDABOWDIT? Not arguing, but since removing the bucking mags is a big deal, I have to assume that they are glued.... yes?


... as would possibly a slight increase in sensitivity.For a second that made more sense than the reduction I'm remembering, but then I had to go and think about...

FTGV,
Check me out here...
- Using a bucking magnet to negate the external magnetic field would also reduce the axial field; therefore
- A given current through the VC would produce less movement since the attraction/ repulsion to a reduced axial field would be reduced; and
- Less movement = reduced sensivity...

[FTGV]

Actually Tour I'm thinking it will focus more of the magnet strength(flux density) into the voicecoil gap,therefore increase voltage sensitivity ?

[brgman]

Not glued,just slapped on the back of each driver.Strong little suckers too!

[twochannel]

Bucking Magnets! I installed them on my SDA-SRS's because my CRT TV had distorted colors only three feet away. I purchased a Sony XBR RPTV 7 years ago and have only recently removed the magnets from the mid bass drivers because I was curious how much they effected the sound. Yes, the bass is much better without the magnets. I left the bucking magnets on the tweeters until I replace them with RDO194's. Mine were not glued to the back of the drivers.

[F1nut]

Yes, the bass is much better without the magnets.

I think it is more likely that you got a better seal when you reinstalled the drivers. I don't see how the bucking magnets could decrease the bass response.

[brgman]

The plot thickens.Poking around for info everything i am reading is to reverse polarity when installing.Hence forcing the bucker onto the driver mag and using epoxy to keep it on.
Mine are all opposite of this.They are just stuck on by equal polar magnetics.:eek::confused:

[dorokusai]

Look man, do what you want. You have all the information you need to make a decision and they should be connected as they are right now.

Good luck.

[inspiredsports]

Not glued,just slapped on the back of each driver.Strong little suckers too!

I'm curious if they were installed correctly if they are just slapped on north/south/north/south instead of being oriented to repel, centered at the null, and securely glued in place. I thought the idea was that they repel/cancel the extraneous field of the existing magnet . . .

https://www.madisound.com/store/product_info.php?products_id=8285

"Bucking magnets are used to reduce the stray magnetic field of a woofer. This will allow you to put the woofer closer to a CRT TV screen. The magnet is glued to the back of the existing magnet system with the magnets repelling each other. When the magnet are centered, the magnetic field will cancel and it will be possible to glue the magnet on."

[FTGV]

I don't see how the bucking magnets could decrease the bass response.Well a possible scenario .If the electrical Q of the driver is dramatically changed with the additional magnet it would increase damping in the bass.Increased damping would make the bass tighter which some equate to less bass.


The plot thickens.Poking around for info everything i am reading is to reverse polarity when installing.Hence forcing the bucker onto the driver mag and using epoxy to keep it on.
Mine are all opposite of this.They are just stuck on by equal polar magnetics.:eek::confused:To be effective at reducing stray magnet fields they have to be installed with opposing poles.Installing them otherwise just increases the stray field(worse for a CRT)and will change driver characteristics.


Edit.I see post above already covered the last point.

[inspiredsports]

brgman, yours were installed improperly from what I can tell.

[FTGV]

brgman, yours were installed improperly from what I can tell.

Agreed.

[brgman]

Agreed.

That's what i thought.Thanks for confirmation

[F1nut]

Mine were not glued to the back of the drivers.

Not sure how I missed this, but like brgman's, yours were installed incorrectly.

[dorokusai]

Either way, he's never sonically heard a difference so is this really an issue? He didn't even know they were there until he investigated. Why is everything on Club Polk so difficult? It would be different if this was the Skunk Works department....but it's far from it. DK and TFLF are the only people to really go out of the box here.

Remove them, replace them, reglue them, swap them, modify the xovers to compensate for the bucking magnets, modify your room to compensate for the waxing and waning of the moon, etc. It just never ends and is not that hard to choose something simple.

Brgman - Cool thread :smile: Good luck.

[Toolfan66]

Take em off throw them in a box and move on.... Put em back together and put em to use..

[FTGV]

Either way, he's never sonically heard a difference so is this really an issue? He didn't even know they were there until he investigated. Why is everything on Club Polk so difficult? It would be different if this was the Skunk Works department....but it's far from it. DK and TFLF are the only people to really go out of the box here.

Remove them, replace them, reglue them, swap them, modify the xovers to compensate for the bucking magnets, modify your room to compensate for the waxing and waning of the moon, etc. It just never ends and is not that hard to choose something simple.

Brgman - Cool thread :smile: Good luck.Dude what up with the fixation with making everything 'simple'?You have spouted this verbiage in a number of threads regarding how the members here are over complicating things.(yet you say great thread)It's a frickin audio forum so sometimes minute technical details will be discussed.Feel free to ignore posts if they are too complicated or are not from one of the only two individuals in whom you feel posts have merit,and leave us to our foolishness.:wink:

[dorokusai]

Dude what up with the fixation with making everything 'simple'?You have spouted this verbiage in a number of threads regarding how the members here are over complicating things.(yet say great thread)It's a frickin audio forum so sometimes minute technical details will be discussed.Feel free to ignore posts if they are too complicated or are not from one of the only two individuals in whom you feel posts have merit,and leave us to our foolishness.:wink:

I often say great thread because its at least not a bunch of arguments and useless discussions about how big your Polk member is, in regards to SDA soundstage....or cables.

However, this place never ceases to over complicate the simple things and offer suggestions for items that were never mentioned by the original poster, OP for those that shorten everything possible. Sure, everyone is just trying to help....blah blah....and maybe I'll mention something that hasn't been suggested. That's quite possible but unlikely given the historical content here on certain subjects, especially SDA for example. No one uses the search engine anymore.

A classic Polk example is...."I would like to know what kind of AVR I can get fro $200 and I've narrowed it down to 2, Pionoeer and Onkyo. What are your thoughts?".....Polkie "I suggest the upcoming Pass Labs AVR for $4000 if you really want to get the best from your Polk speakers.". You get the idea as I'm sure since you can read it every 3 months in one way or another.

The search engine here sucks ass and most quit after a couple failed searches. I don't blame them one bit but its almost as if zero effort happens anymore. The winner in this, oddly enough, is our forum because we have such a diverse group of members that its fairly easy to ind the information you seek. That's not common, and I assure you, I'm everywhere when it comes to audio forums. THAT'S cool, but....

When you get a few years under your belt, you may understand some basic frustration as it pertains to here, the depths of Polk Audio. And no, I'm not talking about post count, just time reading threads. I read more than I post and that's a good thing because I'm too hot headed to be involved in everything and everybody's business anyways. There are much cooler heads to handle these issues but sometimes I get overwhelmed.

Too complicated? Please. Feel free to teach me something and I LOVE foolishness more than ever now....to a point.

It just seems that everything has to be over discussed to the point that even less decision is actually made. I thought this was a grassroots forum, where we shoot from the hip, did things against the grain, middle finger to normalcy....it reads more like we cant do anything without getting a handjob from 10 members anymore.

[dcoil]

Wow, bucking magnet?:confused: I learn something new everytime I read this forum. Now I know what it's for and how it should be installed.:cool:

[FTGV]

Too complicated? Please.As in too complicated for your simplistic sensibilities,not your knowledge base.
Feel free to teach me somethingNope I'm certain this newb has nothing for you there.

On a different note is speaker wire sold by the foot?:smile:

[dorokusai]

As in too complicated for your simplistic sensibilities,not your knowledge base.Nope I'm certain this newb has nothing for you there.

On a different note is speaker wire sold by the foot?:smile:

LOL I'm not sure that has been closed yet. You're not a newb FTGV and I'm no guru, so unless your capacitor is bigger than mine, we should be pretty even.

[Tour2ma]

"Bucking magnets are used to reduce the stray magnetic field of a woofer. This will allow you to put the woofer closer to a CRT TV screen. The magnet is glued to the back of the existing magnet system with the magnets repelling each other. When the magnet are centered, the magnetic field will cancel and it will be possible to glue the magnet on."In all my Googling, I never turned up a source as clear and certain as this. Most of what showed were forum threads as, if not more, scattershot as this one.

For some reason this thread brought this (http://www.youtube.com/watch?v=8ZvugebaT6Q&feature=related) to mind…


Is that Big Ted at the 1:27 mark?

[inspiredsports]

In all my Googling, I never turned up a source as clear and certain as this. Most of what showed were forum threads as, if not more, scattershot as this one.

For some reason this thread brought this (http://www.youtube.com/watch?v=8ZvugebaT6Q&feature=related) to mind…


Is that Big Ted at the 1:27 mark?

That is clip incredibly funny, and on the mark.

[greyford1979]

LOL I'm not sure that has been closed yet. You're not a newb FTGV and I'm no guru, so unless your capacitor is bigger than mine, we should be pretty even.

I always enjoy reading your posts, usually end up with a big grin on my face lol:biggrin: