Dual Magnets on Speakers

If you had about $20,000.00USD in test equipment and a very quiet place to test them, you might be able to tell the difference in the Thiele-Small parameters of a speaker with two magnets. But, could you hear any difference in sound quality? Nope!

Save your time for listening to the music.

I'm not sure if I could say "always" but I feel safe saying "usually", the second magnet is called a "bucking" magnet. It's there to cancel the magnetic field of the main magnet, so the speaker would not cause magnetic field induced problems with magnetic field sensitive devices, such as CRTs. With the growth of non-CRT displays, this probably is not as much an issue as it once was.

Tom

Trying to 'cancel' some of the flux from a permanent magnet by placing another permanent magnet in close proximity, would not be a rewarding task. There would almost certainly be more flux whatever the configuration. Flux isn't really 'cancelled out' unless the magnet is overwhelmed. Flux can be turned. Thiss is probably how stray flux is minimized. ..........................Benbenben

Some automotive (and I would think home audio) speakers have a Dual Voice Coil (DVC) set up where there are two magnets pushing the cone, and these typically boast greater power output from one speaker cone. I don't know if this may be what you are referring to, but it seems to be the automotive audio answer to getting more volume out of limited space. I doubt if there are gains in sound quality, but I'm no expert on the subject.

I believe the magnets are both fixed in relation to each other, and the portion of the cone which they act upon passes through both magnets, so that the cone can be pushed with twice the power without increasing the voice coil diameter.

-T

Everenlightened,

I don't believe Dual-Voice-Coil speakers typically have dual magnets. The DVC setup is a method to allow three different types of connection options. You can drive them with the coils in series, in parallel, or independently. There may be DVC sub-woofers that have dual magnets, but the ones I've worked with didn't.

Tom

I thought some set-ups had two matched magnet+voicecoil components where some have one magnet with two voicecoils, I'm really not sure, I just remember helping a buddy put a DVC speaker into his sub box, he was replacing an alpine sub single coil with a dual coil from the same series and the dual coil was like 3" deeper into his box. Maybe it just used a larger magnet.

I'm definitely no expert, and I very well could be wrong about the two magnets set-up.

-T

Hey those are special designs !

If you do that with any and every speaker, most of the times you shall end up cutting down the performance of the speaker in terms of PMPO and decible output !

Please do not try some thing without knowing why it has been done !

Ashok Shukla

09810145598

Just playing around with no knowledge is MOST unlikely to make any positive changes.

If the loudspeakers were so badly designed that a rank amateur with no knowledge and no equipment could make them better, I can only say that is not a good starting point!!

Better quality does not need to be expensive....I bough two oval car speakers, wide range (3 speakers in one frame) for my caravan after a listening test in the shop first, they were easily picked out as being as good as significantly more expensive ones, but lower wattage..... Totally fantastic, not even €30 and can handle up to 50 watts.....cheap, but a good, well known name (don`t ask I have since forgotten!).....

TDESMIT is correct.

1) the extra magnet is there to force the magnetic flux to be more perpendicular to the face of the speaker. Hence reducing the effect on a CRT when the speakers are next to a TV. You see this on almost ALL internal speakers of TV sets. Or if nothing else a metal shield around the actual magnet.

I have never heard of it actually increasing performace...How it would (if it does) I have no idea.

2) a DVC speaker simply has two Voice Coils that are driven 180 degrees out of phase of each other. Hence increasing the overall efficiency of the speaker. (One is pushing the cone while the other is pulling the cone) And because there are two coils they can obviously handle more power.

Good answer TDE!

bill12780

Bill, thanks for backing me up, I appreciate the "Good answer TDE", but you can also chose to vote my response as a "Good Answer". I know I shouldn't fish for GA's, but I can't resist (the devil made me do it! )

Sorry my man...I forgot to GA you.

My bad...I fixed it.

bill12780

PS The devil makes me do lots of stuff....no worries.

Thanks to all who replied. I opened this topic because when I bought a pair of speakers from a local "DIY expert" I noticed that there are several woofers that has another similarly-sized magnet glued at the woofer back plate aligned with the original magnet, supposedly to improve the efficiency and sound quality. At that time all woofers have magnets already glued to them (some even had a triple stack!) so I did not get a chance to listen to the difference with only the original magnet vs the dual or triple stacked magnets. I do hope i get another chance to visit his shop and do some listening and sensitivity tests.

The second magnet will increase the bass response. Let the other one pull it in (don't oppose the field). This will simulate a larger magnet.

Hi,

You have missed the practical question: Can improvement be made by adding a second magnet?

If a second magnet is added (either way) the voice coil will have different movement in both directions for the same power input, as per the original design. Muffled sound, different response. May damage cone at higher power.

Different strength magnetic field for different size cone and coil.

easyab