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The Free Air Driver Excursion Video Thread


Ricci

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This is where we are going to dump videos of drivers being exercised in free air. Hopefully this will help give some sort of an indication as to how much useful excursion a driver has and when it starts to get noisy or make mechanical clatter. Nothing scientific here just a cheap camera mic recording the noise that each driver makes when driven to large excursion in free air. I don't know that every driver will be done like this or not. Eventually maybe this will be done with a better microphone and video camera. These first couple of videos are off of a cell phone so they are not very good quality at all. hopefully there is enough there to give you an idea of which drivers are noisiest which have the most useful excursion, how the noise occurs etc...Again these are terrible quality since this was spur of the moment, I was using a cell phone and trying to control the signal being applied at the same time. (16Hz sine wave). I apologize for the quality.

 

Note: Once any of these drivers is placed in an enclosure with some dampening it will dramatically cut down on the noise emanating from the back side of the driver. Free air is a worst case scenario since all of the drivers output is self cancelling, what is left are the undesireable mechanical and air pumping noises of the unit in operation. No long throw bass driver I have yet seen is completely quiet in operation when driven to xmax and extreme excursion levels. Still, some are better behaved than others and some of these operational noises are loud enough that they will be audible through the cone while operating within an enclosure.

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Creative Sound Solutions SDX15

 

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As can be heard in this video the driver is impressively quiet through the initial 1.5" of peak to peak excursion, almost silent, exactly as you would want a driver to behave. Abruptly it develops a very loud tapping sound that sounds like physical contact. This is well before the rated 30mm one way xmax is reached. Physically pressing the cone inward shows that the coil is nowhere close to bottoming out. Perhaps it is coil rock. Both SDX15 drivers that I have used behave in the same manner. Others who have owned these drivers have reported the same thing.

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Mach 5 Audio UXL-18

 

 

 

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This driver is very quiet through it's initial first 1" to 1.5" of excursion other than a slight whistle from it's tiny pole vent. It maintains very good noise levels up until about 2.5" peak to peak where it abruptly transitions into a distinct clattering sound. This might be coil rock perhaps due to an out of round cone as the test unit exhibited a bit of curvature on one side of the cone. The UXL still has substantial physical clearance left when this occurs. Otherwise this unit is impressively quiet through it's useful range of stroke. Xmech seems to be about 40mm inward and limited by the soft parts.

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Fi Car Audio SSD 18 D2

 

 

 

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This driver exhibits a lot of stroke for the money but develops some motor air noise and a distinctly mechanical noise during high excursion. Even at modest excursion levels of 1 to 1.5" peak to peak there is an odd mechanical tap emanating from it. The driver is rated at only 21mm xmax so perhaps this noise is due to some sort of BL non linearity or the drop off in force seen with the coil pushed so far from center position. The driver will produce excursions of about 2.75" peak to peak without damage but once past about 2" peak to peak it has loud mechanical and motor air pumping noises. Also the leads looked perilously close to stretching tight on the spider landing. Xmech seems to be about 40mm and limited by the suspension stretching tight.

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Fi Car Audio Q18 D2

 

 

 

 

 

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This driver behaves similarly to the SSD 18 but with slightly less mechanical noise. This could be due to production tolerances in the builds or the longer effective range of motor force. Xmax is rated at 28mm for this driver versus 21mm for the SSD. The mechanical limits are no different and at about 2.75" peak to peak the mechanical noise from this driver is very loud. Similar to the SSD there is a mechanical knock which is present and increases in loudness at higher excursion but it still noticeable free air at modest drive levels. These drivers are mechanically rugged but do have the aforementioned tapping sound and develop air noise from the under spider vents during long excursions. Xmech seems to be about 40mm effectively due to the surround getting very tight.

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SSA Xcon 18 D2

 

 

 

 

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This driver behaves similarly to the Fi SSD and Q 18's which is unsurprising considering the similarities between all 3. The Xcon seems to be the quietest of the 3 by a small margin but this could be due to nothing more than production tolerances or it could be that the extra extended 31mm xmax is coming into play as less distortion due to BL non linearity, or it could be that the sewn in voice coil leads are responsible for some of the reduction in noise. It still produces the same slight knocking sound that the other 2 drivers do even at relatively modest excursions. It too is producing a lot of mechanical noise once driven to about 2.75" peak to peak. real world excursion limits seem to be about the same for all 3 of those drivers but the longer xmax does seem to reduce the driver noise at the excursion limits a little. Again Xmech seems to be about 40mm due to the suspension running out of travel.

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TC Sounds Pro5100

 

 

 

 

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This driver has little noise up to an excursion level of about 1.5" peak to peak but gradually develops more mechanical noise as the stroke is increased from there. At about 2.5" peak to peak the mechanical noise gets severe so the testing was stopped. The pole vent on this motor passes a very large amount of air at large excursions but it is relatively quiet due to the large diameter and radius built into the design. The amount of stroke that the accordian style surround on this driver allows is surprising as is the amount of useful stroke from a driver with this much sensitivity. Xmech seems to be about 38-40mm inward.

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RE Audio MX-18 D2

 

 

 

 

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This driver operates relatively quiet mechanically at least up until past 2" peak to peak but the motor makes a very obvious hissing noise from all of the air movement. The motor does not have much venting. What is there consists of the VC gap itself and a small 1/8" vent around the top plate. With a big 4" VC pumping back and forth it forces a lot of air in and out of these small gaps. This driver is rated at 22mm xmax, but it was driven up to about 3.5" peak to peak without damage. It does start to make a lot of air noise and a loud knock develops around 3" peak to peak but this is well past the 44mm rated linear range of operation and also may partly be the amp clipping as this driver will take all of a 1400w rated amplifier channel in free air without damage. Xmech physically measured at 48mm inward where the bottom spider joint contacts the top plate. I'm not sure whether the motor has enough force left to move the assembly that far against the increasingly tight suspension.

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PSI 18" recone of an Elemental Designs 13AV2 motor

 

 

 

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This driver was fairly quiet up until about 1.5" peak to peak where it started to produce a little more racket. Air noise from the motor was not an issue and the pole vent moved a generous amount of air at high excursion. Similar to some of the other drivers this one did decently up until about 2" peak to peak at which point it changed character and developed a lot of extra noise and a dull tapping or doubling type of sound. At about 2.5-2.75" peak to peak the amount of noise was substantial and not knowing the driver mechanicals or specifications the testing was stopped.

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  • 3 weeks later...

Here is a grainy excursion video for the 18Sound 21LW1400.

 

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This 21" pro driver turned in a surprisingly quiet and large amount of stroke. Xmax is only listed at 9.5mm. Looks like this drivers useful excursion could be listed at something closer to 15 to 18mm. It does eventually start making a lot of suspension clatter once too much past about 1.25" peak to peak but still for a pro driver and with such a small manufacturer's xmax rating this is an over achievement. The motor moves a lot of air out of the pole vent and from under the frame at high excursion but it doesn't get noisy until the suspension noise is already drowning it out anyway.

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B&C 21SW152-4

 

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This driver is relatively quiet until about 1" peak to peak and starts to make some suspension and motor noise from there. At large excursions the motor does emit some noise and there is a very large amount of air flowing out of the pole piece and from under the spiders. At about 1.5" peak to peak the driver starts making a lot of suspension and motor noise. Further increases in input power produce little increase in excursion indicating that the suspension and or motor are not responding linearly to further power increases and resulting in excess heat to the voice coil. It should be noted that while the manufacturers Klippel verified xmax is about 15mm the usual calculation of gap height minus the the height of the coil wind, divided by two results in only 9.5mm. Physical hard bottom Xmech is supposed to be 30mm inward but it is unlikely that the driver can physically produce this much excursion judging from obscene amounts of power being dumped into the driver with test tones in free air. The amplifier is rated at 1400w into the load in the video and is clipping at the highest excursions shown.

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SUNDOWN AUDIO ZV3 18D1

 

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This driver features a hefty motor with a couple of large under spider vents and a moderate sized machined pole vent surrounded by some under gap vents. During high excursion operation the motor has a little bit of a whistle to it from the pole vent which increases with excursion but it is not excessive and is likely to be inaudible once in an enclosure. This is one of the quieter drivers that I have seen mechanically. Definitely a step up from most. there is virtually no noise other than a quiet whistle from the pole at 1" peak to peak. it remains linear and still comparatively very quiet up to and past 2" peak to peak. This driver was driven up to about 3" peak to peak or maybe slightly past and it still seemed to be responding to power increases well. At around the 2.5" peak to peak mark it starts to make some mechanical clatter which gets increasingly louder from there on out. The testing was stopped due to noise and the likelihood of it approaching it's mechanical limit on the inward portion of the stroke. This driver would be a good choice for a system needing a bass pump that offers high displacement with low self noise.

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  • 4 months later...

RE Audio XXX 18d2

 

 

 

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This driver claims a massive 54mm xmax and has a measured physical xmech of about 62mm inwards at which point the glue joint of the bottom spider crashes into the top plate extension. It seems impossible that the suspension could support this much stroke but it somehow does. Past about 3" peak to peak the surround starts to dimple a little. The mechanical noise is low through the first couple of inches of stroke and increases from there until producing a large amount of chatter past 4" peak to peak but considering the absurd amount of movement this driver is capable of it is impressively quiet through the first 4" of travel. The majority of the noise is actually air rushing through the motor vents which pump a large amount of air and creates an in/out chuffing noise as the assembly flies to and fro. The amplifier is clipping by the end of the video so even with a 1400w rated amplifier channel there is no chance of bottoming the driver in free air.

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  • 3 weeks later...
  • 1 month later...

Stereo Integrity HT-18D2

 

 

 

 

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This incredibly cheap 18" driver has an xmax rating of 20mm one way. Physical pushing in of the cone until the former touches the backplate indicates that the xmech is around 32-35mm or so. the driver is clean and noise free up through the initial 25mm peak to peak of excursion but starts to make some air noise through the motor and suspension noise past that point. The operating noise increases until by 45mm peak to peak it has grown quite loud. 50mm peak to peak or a little more will not cause damage but is getting close to hard bottom. The 20mm xmax rating seems appropriate.

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  • 2 weeks later...

Dayton Audio RS-18HO

 

 

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This low cost 18" driver has an xmax rating of 12.75mm but the xmech is about 32mm inwards which the suspension system will support. The motor will push the assembly that far as well. excursion noise through the first 25-32mm peak to peak is impressively quiet. Past about 35mm peak to peak the driver starts to make more noise as the air through the motor starts to chuff and distortion increases as the suspension and motor get increasingly non linear. peak to peak excursion of a little over 50-55mm are possible but excursion of about 40mm peak to peak seems like a practical limit for typical use.

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