Too much excursion! with no watts no less!!! - diyAudio
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Old 4th March 2007, 01:18 AM   #1
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Default Too much excursion! with no watts no less!!!

the other day i had some friends over, so i turned on the sub/sat system, and turned it up with some metal. At which point i noticed my poor fe166e getting about 5mm p-p!!! :O. Needless ot say i ran for the volume knob at full speed hoping the damage wasnt permanent. and yet to my surprise, they werent the speakers that i selected( the harsh lower treble should have given it away, but i was enjoying mild inibriation). So i figured WTF and turned it back up. Once again teh fostex leap into action! so i put my ear infront of them...RIIIGGHHTTT UP! and guess what?

no sound. at all.

so what was happening? i believe that a horn helps a driver couple with a room better....it probably works the opposite way! the immense compressions in my room that my subwoofer was making, was causing the drivers to excurt with no power!

so that begs the qeustion....what do i do about it? just leave it alone? i cant imagine that a driver with an xmax of less than a mm likes 5mm+p-p, although the fostex does have SIGNIFICANTLY more mechanichal capabilities.

i notice that the drivers seem to jiggle alot when tapped when they are not recieveing any power, but when you select them with the reciever(even not recieving any actual music) they become significantly more damped, and only create a mild bump when tapped. Is there another way i can acieve a similar affect? maybe a small amount of DC current when the speakers arent in use? a attenuated and inverse phase signal to the speaker?(but that woudl cause phase problems).

ive heard of peoepl bitching about excursion limitations on fullrangers...but never quite in this regard!
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Old 4th March 2007, 10:20 AM   #2
Svein_B is offline Svein_B  Norway
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Shortening the speaker terminals should limit the movement of passive speakers, equivalent to connecting an amp with no signal.

I wonder if unused speakers in a listening room may have the function of "bass traps" at heir resonant frequency. Horns, with their big mouth, may ba able to trap quite a bit of air.

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Old 4th March 2007, 11:00 AM   #3
tinitus is offline tinitus  Europe
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I would think it is excactly your horns that are coupling to the room

Block the horn mouth, and that might be the end of it
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Old 4th March 2007, 12:01 PM   #4
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I noticed that once with a pair of subwoofer boxes I had stacked..
If I cranked one subwoofer,I could see the cone of the second one moving a bit,and it was completely disconnected!

I wonder if that can cause a drop in SPL,from the second speaker absorbing the sound wave? I would assume so.
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Old 4th March 2007, 01:43 PM   #5
ronc is offline ronc  United States
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I wonder if unused speakers in a listening room may have the function of "bass traps" at heir resonant frequency. Horns, with their big mouth, may ba able to trap quite a bit of air.



Yep!

ron
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Old 4th March 2007, 01:51 PM   #6
freddi is offline freddi  United States
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my 15" Karlsons pick up lots of energy (seemingly for a pretty good span - not just one bass note) and reradiate it so shorted condition on a speaker not hooked up can do some interesting things. Perhaps a pot and cap ?
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Old 4th March 2007, 11:32 PM   #7
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Quote:
Originally posted by tinitus
I would think it is excactly your horns that are coupling to the room

Block the horn mouth, and that might be the end of it
Totally agree with this. Depending on the volume (and at what point your horns are resonating) you could do damage to your drivers in this way.

I remember my brother using a speaker as a microphone at one stage (he'd broken his and was poor), but shorting out the speaker terminals won't stop the physical interaction with the air movement in the room.
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Old 5th March 2007, 06:42 AM   #8
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Not about backloaded horns but horns anyway:

"For example, the horns attached to the driver act in both directions - not only do they transform and radiate sound from the driver to the outside world, but they also focus external sounds on to the diaphragm, adding significantly to its stresses. "

From:

http://www.meyersound.com/support/fo...op/drivers.htm

As already mentioned: Short-circuiting the voice coils should help a bit.

Regards

Charles
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Old 5th March 2007, 11:41 PM   #9
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Quote:
Originally posted by Cloth Ears
I remember my brother using a speaker as a microphone at one stage ...
I once worked in an office where there was evidence that the big shots (really just one big shot) was listening in some times, but we could not find any microphones.... DUH! He was using the PA speakers in the ceiling. No Kidding.

Who knows, maybe there's a clever way to measure horn response buried in there somewhere.

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Old 8th March 2007, 02:15 AM   #10
synergy is offline synergy  United Kingdom
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Quote:
Originally posted by Cloth Ears

Totally agree with this. Depending on the volume (and at what point your horns are resonating) you could do damage to your drivers in this way.

I remember my brother using a speaker as a microphone at one stage (he'd broken his and was poor), but shorting out the speaker terminals won't stop the physical interaction with the air movement in the room.
won't help in the slightest in fact it'll probably do more harm than good as you're completely disengaging the driver from the circuit by shorting what's left of any potential amplifier damping straight to ground

choose your poison-

turn your volume down
remove them from the room
try to find some way of plugging them up
or play the same material through them but at a significantly reduced volume (some 25-30dB below)
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