It's fairly common for bass guitar-designed speakers to have asymmetrical suspension and/or excursion which can cause what you saw. This goes against the grain of normal speaker design theory (and is often overlooked).
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Speakers.. push or pull?
- Thread starter BASSKADET
- Start date
- Dec 18, 2000
- 13,201
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- greenboy designs: fEARful, bassic, dually, crazy88 etc
I was trying to avoid that. Aggie thought I might have it cranked too much but I disagree. I have no problem with the sound of the 15". And there is only a 50W difference between the two. Both are 8 ohm.
Can you post a video on youtube? Does your camera have a high speed setting?
Your title is right. speakers push and pull air. They set up a longitudinal pressure wave. Which needs to push and pull.
Record you're low E and look at the wave form. Most all bass guitar waveforms are asymmetrical. They are bigger on one side of the waveform than the other. If you can actually see this by looking at the speakers you have some truly superhuman abilities and should contact Stan Lee.
Your title is right. speakers push and pull air. They set up a longitudinal pressure wave. Which needs to push and pull.
Record you're low E and look at the wave form. Most all bass guitar waveforms are asymmetrical. They are bigger on one side of the waveform than the other. If you can actually see this by looking at the speakers you have some truly superhuman abilities and should contact Stan Lee.
Actually, JBL came out with a fix for asymmetric excursion some years ago, their so-called "symmetrical field geometry". They add a ring of some kind to the bottom of the pole piece that makes the magnetic flux structure in the voice coil gap symmetrical (it's typically got a big lobe on one side, usually going towards the back of the magnet). This supposedly reduces harmonic distortion.
I had a pair of E140's with the SFG in my main cabinet back when I was gigging and I have to say I've never heard lows down to 40hz that were as smooth as I got out those drivers.
BTW, if you see the cone kind of wobbling in and out when overloaded that's more likely instability in the amp itself. If it always consistently goes in one direction, that could also be the driver itself...
LS
- Jun 24, 2006
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don't gum up Aguilar's customer service centres on calls like this...does it sound OK? That's all that matters. We don't know whether this speaker is made to go out more than in, or whatever. Most bass speakers that I have owned go 'in' more than 'out', because their suspension is stiff and made that way.
Frivolous complaints drive me crazy...
Cameron
billfitzmaurice
Commercial User
- Sep 15, 2004
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Do it it both directions, with a straight edge across the front of the frame. You can measure how far it travels in each direction, and it should be the same. The likelihood of otherwise is very slim.
I have been told that a speakon cable with its poles reversed will result in the speaker going in instead of out. Did you make the cable? Is it a speakon? If so, change out the speaker cable and test it.
okcrum
in your chest
OP, are you doing this under fluorescent light? If so, you are seeing the stroboscopic effects of the lighting. Try again under incandescent light and then tell us what you see.
don't gum up Aguilar's customer service centres on calls like this...does it sound OK? That's all that matters. We don't know whether this speaker is made to go out more than in, or whatever. Most bass speakers that I have owned go 'in' more than 'out', because their suspension is stiff and made that way.
Frivolous complaints drive me crazy...
Cameron
Do you think I would bother with this if it sounded alright...
I think the problem of the OP's speaker is indeed a voicecoil not mounted symetrical to the airgap.
I have had this problem with a few drivers too (Eminence Deltalite 2510, Delta 10b and some ol' 6" philips drivers).
Because the magnetic field is asymetrical the cone wil move more into one direction (the direction in which the magnetic force is the strongest)
Try to do what Bill says, use a 9v batterie and see how far the cone travels in either direction. In your case it should move more in then out.
I have had this problem with a few drivers too (Eminence Deltalite 2510, Delta 10b and some ol' 6" philips drivers).
Because the magnetic field is asymetrical the cone wil move more into one direction (the direction in which the magnetic force is the strongest)
Try to do what Bill says, use a 9v batterie and see how far the cone travels in either direction. In your case it should move more in then out.
Only thing I can think of would have to be some DC at the amp output, a seriously AFU amplifier...
Randy
The problem I had was really because of the drivers. I tried different amps and the problem still occured. And it also did not occur with other drivers, so I'm pretty sure it was not the map.
I really don't believe it's DC at the amp output.
Maybe the OP should check the speakers at a different amp. Connect the speakers to a regular amp, run some music and turn up the bass control and see what happens.
No, this isn't a stupid joke or wordplay. I have a sealed (I thought) 212 cab that I swiped from my son's car stereo (boy, was he pissed). Anyhow, when I played through it, I saw the same rearward cone excursion, with little forward travel. Upon investigation, it seems the speaker wire was run into the cab through a 4"X4" hole in the back. Why such a large hole, I can't imagine, maybe the little dweebs that built it only had a saw and no drill. So, when I fabricated a plate to seal the hole, the performance and behavior began to resemble a normal speaker. I guess it was pumping out the air quicker than it could normally be drawn back in...So...check yours for something similar...who knows??...keep us posted...Cheers
