Horseshoe pickup magnetization experiment

walker · Post by **walker** » Fri Feb 17, 2012 9:15 pm

Here's an experiment I did earlier this evening. I took some very strong, yet small magnets, and applied them to the horseshoe pickup in various configurations. I was surprised by the results.

I had just the horsehoe pickup on during this experiment. The audio is picked up solely by the lo-fi mic on my camera. I started out with no additional magnets on the pickup.

34 seconds in - notice how much bottom end is accentuated when the magnets are attached!

At 1:18, I put the magnets on the E/A side with the polarity reversed. Notice how it colors the tone. (I'm not sure which side of the magnets is North or South, so I'm just saying "normal" or "reversed." If anyone has the correct terminology, feel free to jump in.)

At 1:35, the magnets on the E/A side are reverse polarity, while the D/G side is normal. You can really hear how the opposing polarities affect the sound differently.

At 1:57, both sides are attached with reversed polarity.

2:15 - (same configuration as at 1:35.)

2:27 - both sides are attached with normal polarity

2:39 - magnets removed (where'd the low end go???)

One weird thing - the small magnets stick to the horseshoe magnets on either side, which is uncharacteristic of how magnets usually attract on one side, and repel when flipped over.

***What you see in this video is the extent of the experiment. It was fun to mess with, but I've been warned by the guy who usually recharges my horseshoe magnets to NOT expose them to other magnetic fields because it could permanently disrupt their polarity, especially when subjected to opposing polarity.***

johnallg · Post by **johnallg** » Fri Feb 17, 2012 9:44 pm

Very interesting Mark. I've thought of doing this but was afraid of what it would do to the shoes. Another point I noticed and you didn't bring up was when you went from opposite polarity to the same at 2:27 there was a reduction in the hum or background noise.

walker · Post by **walker** » Fri Feb 17, 2012 10:11 pm

Good ear, John. I didn't notice that. Although, the degree of buzz & hum is greatly affected by when I am or am not touching the strings or pickups, and what angle I'm holding the bass at. Those factors could have come into play, too.

Kopfjaeger · Post by **Kopfjaeger** » Fri Feb 17, 2012 10:40 pm

Mark,

Very cool!! I'm assuming it's an original horseshoe pup and not a reissue? Not sure if that would make a difference or not. Also, what strength magnetic pull should the horseshoe naturally possess? My 67 horseshoe has a bit of strength but quite near the growl of yours with or without the additional magnets on it.

Sepp

sloop_john_b · Post by **sloop_john_b** » Fri Feb 17, 2012 10:47 pm

Fascinating stuff Mark!

Can ya do it with flats next time?

8mileshigher · Post by **8mileshigher** » Fri Feb 17, 2012 11:22 pm

That is a cool experiment. Very fascinating things you learn about on this Forum

walker · Post by **walker** » Sat Feb 18, 2012 2:36 am

FLATS???

Why, I ought to flatten you for that one, Biscuti! I'd never allow a flat within MILES of this place!

Sepp - yes, the pickup is a stock '68 horseshoe with an output of about 7.5k. (For those who may not already know the difference - the pickups from the '60s and earlier have magnetized horseshoes, but the reissues don't have magnetized horseshoes; the poles are the magnets instead. Also, the reissues generally have much larger coils wrapped to around 12k.)

I don't currently have a gauss meter, but I believe that my '68 horseshoe magnets rate at about 40. They had faded to about 20 before I recharged them, which was about 3 years ago, and they've been hanging tough ever since. As I understand averages, 40 is on the low side. I think most '60s horseshoe sets, more commonly found on the lapsteel guitars, were charged to 50-70 gauss from the factory. I know there's a limit as to how much charge a pair of HS magnets will hold, but I think you could conceivably get a pair up to 100 gauss, maybe even more. I'd really like to get a read from Tony M's '62 4000. That horseshoe basically sounds like my '68 does WITH the extra magnets on it! Yet it's rated at the same ohm level - 7.5k. It wouldn't surprise me if the '62 HS gauss rated at about 70-80.

weemac · Post by **weemac** » Sat Feb 18, 2012 3:31 am

Playing with magnets around old horsies can end in tears. Mark knows what he is doing to fix it if it drops dead. My old one dies several times a year... I'll do a regauss video next time I change strings on my RM...
Eden.

walker · Post by **walker** » Sat Feb 18, 2012 6:52 am

That would be great, Eden!

I have my "go-to" guy for recharging the HS mags that I know is reliable, but Tony Matura and John Algaier have developed do-it-yourself methods with independent magnets that have also proved effective. I think the magnets I used in the video could be used for an effective recharge, but I'd want to check them with a gauss meter before I tried it to make sure I was putting them on with the correct polarity. I almost think I could do it by ear - making sure the bass sounds right when putting the magnets on and just leaving them there overnight, but it couldn't hurt to back that up with the meter.

walker · Post by **walker** » Sat Feb 18, 2012 7:00 am

Another note for what it's worth - those magnets I used in the video are by far stronger than the horseshoe magnets of the pickup. If your touch the HS mags with an average size screw driver, you get a "sticky" pull, but those others would practically pull the screw driver right out of your hand. And although they'll stick to the HS mags on either side, they stick to each other and my refrigerator on only one side, and repel strongly on the other.

ken_j · Post by **ken_j** » Sat Feb 18, 2012 9:16 am

Mark, even using this simple tool from Stew Mac will ensure you get the polarity correct. Schatten Magnet Polarity Tester: http://www.stewmac.com/shop/Electronics ... xsr=117147 I have used one of these in the past and it works very well.

walker · Post by **walker** » Sat Feb 18, 2012 12:27 pm

Thanks, Ken! Man, Stew/Mac has everything! They're like my 'Toys-R-Us'.

ram · Post by **ram** » Mon Feb 20, 2012 12:04 pm

Cool stuff Mark!... the physics & dynamics of magnetic fields demonstrated in real time. That is neat! Eden, would love to see that video as well....

johnallg · Post by **johnallg** » Mon Feb 20, 2012 9:12 pm

weemac wrote:Playing with magnets around old horsies can end in tears. Mark knows what he is doing to fix it if it drops dead. My old one dies several times a year... I'll do a regauss video next time I change strings on my RM...
Eden.

Appreciated. My other pair of magnetic shoes are like this.

johnallg · Post by **johnallg** » Mon Feb 20, 2012 9:14 pm

walker wrote:Another note for what it's worth - those magnets I used in the video are by far stronger than the horseshoe magnets of the pickup. If your touch the HS mags with an average size screw driver, you get a "sticky" pull, but those others would practically pull the screw driver right out of your hand. And although they'll stick to the HS mags on either side, they stick to each other and my refrigerator on only one side, and repel strongly on the other.

A good source for very small but strong magnets are old hard drives.

Rickresource Rickenbacker Forum