Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Cabinets-Speakers => Topic started by: SpareRibs on March 02, 2016, 02:50:04 pm
-
Hello,
I just finished my Newcomb PA to Guitar amp project. I only have one question about speakers.
I pulled speakers form an old Hammond Orgon. One of them is 12" 16ohm's. That is the one I am using.
The speaker has a magnet that is about the diameter of a half dollar, about 1" thick. It is held on by a u shaped piece of steel about 1/4" thick.
I pulled another magnet from a junky speaker That is 2 1/2" in diameter and 1/2" thick.
When I just strum the guitar strings, with the amp turned on, put the magnet onto the back of the existing magnet, it seems to increase the volume.
My question is, will leaving it permanently attached cause damage to the speaker ?
-
Hello,
No one has any ideas, information concerning speakers and the effects the magnets have on them ?
-
When I just strum the guitar strings, with the amp turned on, put the magnet onto the back of the existing magnet, it seems to increase the volume.
My question is, will leaving it permanently attached cause damage to the speaker ?
That's a cool idea and something I've not come across doing before. The increase in magnetism makes the cone harder to displace from it's resting position. Normally when a guitar speaker employs a bigger magnet in general it gives the speaker better bass response, is punchier, yields an increase in power handling ability, stays cleaner longer as power is applied, & is harder to cause speaker distortion, and yes causes it to be louder by means of it being more efficient.
As for possible damage by doing so? Hard to imagine that this could be and in fact should make it less prone to damage by limiting the cone travel more than having less magnetism which allows the cone to travel more. When a cone travels too much as in being over-powered it can help to cause the coil to rub possibly more or out of it's normal range. This could be one reason for speaker damage but another possibility to blowing a speaker is if the wire used to make the coil is so thin that too much current could cause it to heat up too much which would then break it down to either short open or closed similar to a power transformer when it is trying to supply too much current out of it's normal design range.
Lastly, since a magnet has polarity N & S, I would think that when you attach the extra magnet that it causes the cone to move from it's original neutral position? This is going to be the "new" neutral position. As long as it still operates within it's range without over-excursion to the cone I think you're okay without it prematurely blowing the speaker due to this? But it's hard to say how much excursion is okay or not with any speaker let alone an older vintage type?
-
... I pulled speakers form an old Hammond Orgon. ... I pulled another magnet ... 2 1/2" in diameter and 1/2" thick.
When I just strum the guitar strings, with the amp turned on, put the magnet onto the back of the existing magnet, it seems to increase the volume. ...
I didn't really know. So I went looking.
Since the new magnet sticks to the old magnet, they are arranged in opposite polarity. This should have the effect of slightly decreasing the magnetic flux at the voice coil gap. Paradoxically, this increases the cone movement with the same applied power, because it now takes more voice coil movement to generate the same back-EMF. So the speaker sounds a little louder.
It shouldn't damage anything. Then again, I worry about what could happen if you apply a lot of power to the speaker... Very free voice coil/cone/speaker movement seems like it could increase the chances of blowing out the speaker, especially given its age.
But I don't know for sure about that last part. You might best direct the question to a speaker manufacturer who's likely to answer, such as Weber VST.